Chapter 54. Thoracic Anesthesia | Anesthesiology, 2e | AccessAnesthesiology

Thoracic Cavity

The thoracic cavity is formed by the ribs laterally, sternum anteriorly, vertebral column posteriorly, and by the diaphragm and thoracic inlet inferiorly and superiorly, respectively. The thoracic cavity encompasses the lungs, which provide oxygenation of venous blood, excretion of carbon dioxide, and metabolism of endogenous compounds.

Airway

The trachea is the initial conduit for airflow. Its cross section is outlined by the horseshoe shape of the cartilage anteriorly and the membranous portion posteriorly. The membranous portion consists of a fibrous envelope containing smooth muscle and epithelium. The location of the membranous trachea and the vertical orientation of the exposed muscle fibers guide fiberoptic-assisted placement of double-lumen endotracheal tubes into the appropriate side. The innominate artery lies just anterior to the trachea. Tracheal-innominate fistulae are rare but lethal complications of tracheal resection, tracheostomy, or prolonged intubation.

The trachea initially bifurcates into the right and left mainstem bronchi and then into the lobar and segmental bronchi. The right bronchus is shorter, wider, and more inline with the trachea as compared with the left bronchus. Because of the more oblique orientation of the left bronchus, inhaled foreign bodies and aspirated fluid are more likely to go into the right bronchus. The right bronchus provides access to 3 lobes (the upper, middle, and lower lobes) that are separated by major fissures. On the left, a major fissure separates the lower and upper lobes. The lobes of the lung are subdivided into bronchial pulmonary segments, each of which has its own bronchus, artery, and vein. The movement of air progresses through a series of branching tubes, which become narrower and more numerous as they penetrate deeper into the lung. The conducting airways contain no alveoli and therefore contribute a portion, about 50 mL, of the anatomic dead space.

Mediastinum

The mediastinum is the region between the 2 pleural sacs and contains the heart, the great vessels, and the thymus gland. For purposes of description, the mediastinum is divided into 4 subdivisions (middle, posterior, anterior, and superior compartments). The middle mediastinum contains the pericardium with the adjacent phrenic nerves, the heart, and the great vessels emanating to and from it. The superior mediastinum lies between the thoracic inlet and the horizontal plane connecting the sternal angle with the lower border of the fourth thoracic vertebrae. The main contents of the superior mediastinum are the thymus, great vessels, and several nerves. The posterior mediastinum, which is bounded anteriorly by the pericardium and posteriorly by the vertebral column, contains the thoracic aorta, thoracic duct, azygos and hemiazygos veins, esophagus, and bifurcation of the trachea with the 2 bronchi. The anterior mediastinum, which lies between the sternum and the pericardium, contains lymphatic vessels, lymph nodes, and branches of the internal thoracic artery.

Pulmonary Vasculature

The lungs are blood vessel–rich structures with extensive capillary networks that allow gas exchange. The main pulmonary artery branches and follows the bronchial tree, decreasing in size with each bronchial generation. The arteries branch to supply the respiratory bronchioles and alveolar sacks, which provide for gas exchange. The vascular endothelial surfaces form boundaries of the capillaries and occupy about 50% of the surface of the alveolar wall.

The pulmonary capillary network not only provides an enormous surface area for gas exchange but also for active metabolism, synthesis, and release of stored vasoactive substances. The lung also maintains an active role as a biochemical filter, inactivating exogenous and endogenous substances by metabolic elimination or cellular uptake. The release of vasoactive substances can be stimulated either by manipulation during surgery or by hypo- or hyperinflation. One such example is that of hypoxic pulmonary vasoconstriction, which functions in a homeostatic capacity to normalize the perfusion to ventilation inhomogeneity caused by alveolar hypoxia.

The metabolic functions of the pulmonary circulation also can trigger pathologic consequences. Anaphylactoid response to protamine is of particular importance to the cardiac anesthesiologist. The biologically active substances (histamine, slow-reacting substance of anaphylaxis, prostaglandin E [PGE]1, PGE2, prostaglandin F [PGF]2, and bradykinin) are released in response to specific biochemical and mechanical triggers.

Bronchial Vessels

The bronchial vasculature normally accounts for about 1% of the cardiac output, but it may increase its flow in response to acute lung disease or injury. The origin of the bronchial arteries is variable, coming from the aorta or intercostal, subclavian, or innominate arteries. The bronchial arteries enter the hilus of the lung and form a communicating arc around the main bronchus. The vessels follow the bronchi distally, supplying the vasovasorum of the pulmonary arteries and bronchi. The dominant deep bronchial venous system drains into the pulmonary veins, and the lesser superficial system of bronchial veins drains into the azygos, hemiazygos, and mediastinal veins. The clinical importance of the bronchial vasculature system is appreciated under conditions of acute lung stress or injury. Neovascularization and increased blood flow occurs in response to acute and chronic lung disease. This response may help preserve normal pulmonary ventilation-to-perfusion ratio and protect the lung from ischemia. The absence of an intact bronchial arterial circulation in patients receiving a lung transplant places the new lung at increased risk of ischemic injury immediately after surgery.

Lymphatic System

The lymphatic circulation has a major role in maintaining the balance of fluids across the endothelial membrane. Transcapillary flow (F) is proportional to the difference between pulmonary capillary hydrostatic pressure (inside pressure − outside pressure) and the difference between the capillary oncotic pressure and the interstitial oncotic pressure (Fa [P (inside − outside) − P (capillary − interstitial)]). Transcapillary flow also depends on the capillary filtration coefficient (K), which is a function of the effective capillary surface area and membrane permeability. Any clinical situation that impedes lymphatic flow increases the risk of pulmonary edema and pleural effusion. Abnormal clinical states that increase capillary permeability increase the flow of fluid into the interstitial space and increase the chance of developing pulmonary edema. In addition, pulmonary interstitial edema also may result from marked increases in negative pleural pressure. Markedly increased negative pressures can result from upper airway obstruction (tumors, laryngospasm, epiglottis), rapid reexpansion of the lung, or aggressive suctioning.

The lymphatic drainage pattern is from the periphery toward more proximal lymph nodes, which are located at the carina and points of bifurcation of the bronchi and alongside the trachea and great cardiac vessels. The location of the lymph nodes is classified for prognostic assessment of primary pulmonary cancers. The lowest number is assigned to the most central nodes and progresses to greater numbers at the periphery. The pattern of lymphatic drainage has an impact on the sensitivity and specificity of mediastinoscopy to diagnose and detect the spread of disease. Malignant disease of the right lung spreads ipsilaterally up the chain from the pulmonary nodes in the periphery to the paratracheal, scalene, or tracheal nodes more proximally. In contrast, disease from the left lung can either spread ipsilaterally or contralaterally up the chain or proceed subdiaphragmatically to the para-aortic lymph nodes. Biopsying of a lymph node unilateral to the lesion may provide false-negative results if spread occurs contralaterally or subdiaphragmatically.

Work of Breathing

During normal spontaneous inspiration, the major contribution to respiratory mechanics is by the contraction and downward excursion of the diaphragm, which increases the vertical dimension of the thorax. The dimensions of the thorax also are increased by the outward and upward swinging movement of the ribs during inspiration. The importance of diaphragmatic excursion and chest wall movement is most easily appreciated in patients with compromised respiratory function related to positioning. The patient in a flexed lateral decubitus or Trendelenburg position experiences increased abdominal pressure, which limits diaphragmatic excursion and chest wall movement. In addition, patients undergoing thoracic operations are at increased risk of phrenic nerve injury or diaphragmatic dysfunction, which may result in postoperative ventilatory compromise.

The mechanics of respiration are divided into the inspiratory and expiratory phases. The work of normal breathing is associated with the inspiratory phase, whereas expiration normally is a passive process related to elastic recoil of the lung and chest cage structures. The work of inspiration depends on overcoming airway resistance and the elastic forces created by the lung and chest wall mechanics. During normal quiet breathing, the work of respiration constitutes only 2% to 3% of total energy expenditure. During heavy exercise, pulmonary ventilation and total body energy expenditure may increase some 15- to 20-fold, but the energy expended for ventilation increases only slightly to 3% to 4%. Pulmonary disease or dysfunction that alters compliance, airway resistance, or lung or chest wall mechanics can dramatically increase the work of breathing to one-third or more of the total body energy expenditure. For example, the patient with preexisting respiratory disease having minimal reserve is at increased risk of postoperative ventilatory failure and may require reintubation because of diaphragmatic dysfunction and atelectasis.

Cough Reflex

A normal cough reflex is critical for maintenance of pulmonary toilet. Afferent impulses from the respiratory passages are conducted centrally by the vagus nerve. Efferent impulses trigger closure of the epiglottis, apposition of the vocal cords, and contraction of abdominal, chest, and diaphragmatic muscles to produce an explosive exhalation of air. Patients having postoperative dysfunction related to recurrent laryngeal or phrenic nerve injury, trauma to the diaphragm, or pain and who cannot cough effectively are at risk for respiratory failure related to aspiration or poor pulmonary toilet resulting in pneumonia. Such patients may benefit from conservative measures, such as breathing humidified gases to prevent inspissated secretions, chest physiotherapy, and nasal tracheal suctioning to clear secretions.

Preoperative Evaluation of the Patient Undergoing Thoracic Surgery

The preoperative evaluation of patients undergoing noncardiac thoracic surgery is similar to any patient undergoing general anesthesia. The anesthesiologist should perform a history and physical examination and be familiar with current laboratory studies, electrocardiogram (ECG), and radiologic studies of the chest. The anesthesiologist also should understand the evaluation of pulmonary function and the prediction of postoperative pulmonary function. This knowledge will help formulate a rational anesthetic and perioperative plan.

History

Most patients with lung cancer have a smoking history and therefore have some degree of chronic bronchitis and emphysema. This history is important because the management of infections and reactive airway disease preoperatively will have a positive impact by decreasing the incidence of postoperative complications. Exercise tolerance also should be assessed because this will estimate a patient's cardiovascular and pulmonary reserve.1-5

Physical Examination

Along with a routine assessment of the airway and cardiovascular systems, the anesthesiologist should pay particular attention to the respiratory system during the physical examination. Observation of the respiratory rate and pattern may give insight into the pulmonary reserve of the patient. The auscultation of wheezes, rales, or rhonchi indicates abnormalities that can be managed preoperatively. Clubbing of the fingernails may indicate chronic hypoxia or lung cancer. Deviation of the trachea may indicate a mediastinal mass, hemothorax, pneumothorax, or fibrothorax. The anesthesiologist also should assess the patient's ability to tolerate the supine position, because an intolerance to this position may indicate congestive heart failure or major airway obstruction from a mediastinal mass.

Diagnostic Studies

Laboratory tests should be ordered based on positive findings elicited from history and physical examination. The complete blood count may reveal polycythemia, reflecting prolonged smoking and hypoxia, or leukocytosis, indicating an active infection. Liver function studies may be altered, indicating hepatic metastases or drug or alcohol effects.

The ECG should be assessed for the presence of cardiac or pulmonary disease. Signs and symptoms of ischemia may indicate the need for further cardiac workup. Manifestations of cor pulmonale may indicate the presence of pulmonary hypertension, which may alter intraoperative management or portend intolerance to major pulmonary resection.6 However, the futility of subsequent therapeutic intervention is controversial. Recent research concerning patients undergoing aortic or peripheral arterial bypass graft surgery indicates that in some instances coronary revascularization does not decrease the rate of perioperative myocardial infarction or long-term mortality.7

Abnormal chest radiographs frequently antedate the first sign or symptom of lung cancer by many months. The radiograph may reveal tumor, secondary changes in lung parenchyma distal to an obstructed airway, or other abnormalities caused by intrathoracic and extrapulmonary tumor spread. Radiographic findings that may have implications to perioperative anesthetic management are listed in Table 54-1. The tumor may impinge on the trachea or the mainstem bronchi and thus influence the induction of anesthesia, or choice and placement of an endotracheal tube (Fig. 54-1). For example, tumor involvement of the trachea would suggest the use of awake, sedated fiberoptic intubation, whereas isolated impingement of the left bronchus would suggest the use of a right-sided double-lumen endotracheal tube.

Table 54-1 Radiographic Findings with Important Anesthetic Complications

Table 54-1 Radiographic Findings with Important Anesthetic Complications

Abnormality

Anesthetic Implication

Tracheal deviation

Difficulty with intubation

Identify cause: mediastinal mass, nodal metastasis, thyroid gland, aortic aneurysm, other

Mediastinal mass

Difficulty with intubation

Difficulty with ventilation even after successful intubation (see section entitled Anesthesia for Patients With Mediastinal Masses)

Possibility of superior vena cava syndrome and obstruction

Cardiac and vascular compressions

Pleural effusion

Cor pulmonale congestive heart failure

Need for additional monitoring

Careful assessment of response to myocardial depression from anesthetic drugs

Bullae

Risk of rupture with positive pressure and creation of pneumothorax

Wasted ventilation, increased dead space

Compression of healthy adjacent lung

Abscess

Need for separation of 2 lungs to prevent spillage and contamination of healthy lung

Consolidation and atelectasis

Need to manage infections aggressively with antibiotics

Ventilation/perfusion mismatch admixture and hypoxia

Normal chest radiograph

Patient still may have chronic, diffuse infiltrative lung disease with normal chest radiograph

Computed tomography is superior to chest radiography in diagnosing diffuse infiltrative lung disease and should be done before lung biopsy

Figure 54-1.

Patient is a 62-year-old man with esophageal cancer who presented with dysphagia and progressive shortness of breath. Panels A and B show enlarged lung fields with flattened hemidiaphragms consistent with COPD. A mass, designated by an arrow, arises from a structure posterior to the trachea at the level of the manubrium, causing partial opacification and deviation of the trachea, which is better visualized with the lateral chest radiography, panel B. The CT scan of the chest, panel C, shows a large tumor mass (M) in the mediastinum arising from the esophagus (E) and invading the right side and membranous portion of the trachea (T).

In addition, patients will have a computed tomographic (CT) scan of the chest, which is helpful in delineating the presence or absence of high-level nodes and extrapulmonary spread of the disease. Further diagnostic workup is guided by these studies. If mediastinal nodes are suspected, mediastinoscopy or parasternal mediastinotomy may be performed to confirm the diagnosis and to determine the extent of tumor spread. If clinical manifestations of distant organ involvement are present, appropriate investigations, such as bone scan and scan of the brain, liver, and upper abdomen, also should be performed.

Assessment of Respiratory Function

Preoperative evaluation of pulmonary functional reserve is used to estimate the patient's ability to tolerate thoracotomy and lung resection. Patients undergoing thoracotomy for lung resection usually have a long-standing history of smoking and varying degrees of underlying lung disease. Therefore, they have decreased pulmonary reserve and are at increased risk for operative and postoperative morbidity and mortality. Smokers have a significantly increased risk of postoperative pulmonary complications, 8% for nonsmokers and 23% for smokers.8 Carcinoma of the lung is associated with an average survival period of 18 months and a mortality rate of 100% after 5 years if not surgically treated. Therefore, every effort should be made to give the patient the benefit of surgical resection. It is difficult to answer the question, "What is an appropriate risk for rendering the patient a respiratory cripple postoperatively when managing a disease with a mortality rate of almost 100%?" Although most patients do not undergo a complete pneumonectomy, they should be evaluated as potential candidates. It is not uncommon that a more extensive resection is needed than initially anticipated. The next section discusses the tests available to assess respiratory function and the criteria for eligibility to undergo thoracotomy and pulmonary resection (Fig. 54-2).

Figure 54-2.

Sequence of tests for lung resection.1,6,12,15-17,19,58,59,240,350-361

Arterial Blood Gas Analysis

Arterial carbon dioxide tension of more than 40 mm Hg suggests increased risk for postoperative complications. Because hypercapnia may be reversible, attempts should be made to correct all potential reversible conditions, such as bronchospasm or infection. In contrast, hypoxemia is not a consistent criterion for increased risk. The change in Pao2 after thoracotomy and lung resection varies. Lung resection beyond the tumor may not be associated with any further decrement in oxygenation, but it may increase oxygenation by improving ventilation perfusion matching. Tumors that have already occluded the bronchus and the blood supply have already caused a functional resection.

Spirometry

Spirometry has proved to be an effective, inexpensive, and noninvasive way of measuring pulmonary reserve and predicting postoperative pulmonary function. Abnormal spirometry results that suggest an increased risk for postoperative pulmonary complications include forced vital capacity (FVC) less than 50% of predicted, forced expiratory volume in 1 second (FEV1) less than 2 L and FEV1/FVC ratio less than 50%. Other tests having predictive value are the maximum voluntary ventilation (MVV) and diffusing lung capacity for carbon monoxide (DLCO). The MVV is effort dependent, requiring the patient to breathe as fast and as deeply as possible for 6 to 12 seconds. This test is similar to an exercise test because it reflects the entire cardiorespiratory system and the patient's cooperation and motivation. The DLCO is reemerging as an important predictor of risk in patients undergoing pulmonary resection. A recent study has confirmed that the DLCO may be the best predictor of postoperative complications, including death and respiratory failure (Fig. 54-3).9 DLCO less than 50% to 60% of the predicted value is an indication for further testing with split lung function studies before undertaking major pulmonary resection (see Fig. 54-3).

Figure 54-3.

Prevalence of pulmonary complications after major pulmonary resection vs DLCO% for 165 patients.356

Split Lung Function and Ventilation: Perfusion Studies

Patients who are deemed to be at increased risk after the initial phase of the pulmonary function evaluation should receive additional testing to assess the effect of lung resection. The goal is to predict the impact of resection on postoperative lung function. The involved lung tissue may contribute little to existing lung function, and therefore its removal may not cause further deterioration of pulmonary function. Thus some patients who would be denied operations based on the initial results maybe considered surgical candidates after more specific evaluation.

The effect of anticipated lung resection can be predicted using radioisotope ventilation scans, perfusion scans, or a combination of both. More recently, dynamic perfusion magnetic resonance imaging (MRI)10 and quantitative CT have been shown to be as accurate as perfusion scintigraphy at predicting postoperative FEV1.11 Most authorities consider that the minimal predicted postoperative FEV1 that will be tolerated by a patient is 800 mL (Box 54-1). This is based on the observation that patients with chronic obstructive pulmonary disease (COPD) having an FEV1 value less than 800 mL had a dramatic reduction in their level of daily function.12 Additionally, patients with COPD start retaining CO2 and developing hypercapnia when their FEV1 value is less than 800 mL.12,13 These previous studies may have been overly conservative.13,14 Because an absolute value for FEV1 does not account for persons of different gender, height, and age, some physicians base their decision on an FEV1 greater than 30% to 40% of the predicted value.15

Box 54-1

Box 54-1

Factors That Predict Increased Perioperative Morbidity and Mortality

Paco2 >45 mm Hg

Pao2 <50 mm Hg on room air

Inability to walk 2000 ft in 6 minutes

Inability to ascend 2 flights of stairs

Inability to attain 7.5 mL/kg/min O2 consumption

Predicted postoperative FEV1 <30% of expected normal value for patient

Combined predicted postoperative FEV1 <35% and predicted postoperative DLCO <35% of expected normal value for patient

Measures of right heart catheterization after balloon occlusion of PA of a mean PA pressure >35 mm Hg, Pao2 <45 mm Hg, Paco2 >60 mm Hg)

DLCO, diffusing lung capacity for carbon monoxide; FEV1, forced expiratory volume in 1 second; PA, pulmonary artery; Pao2/Paco2, arterial oxygen/carbon dioxide tension.

The radioactive technetium-99 scan yields data about regional perfusion, and the xenon-133 ventilation scan provides data about regional ventilation and lung volumes. The results allow estimation of the fraction of lung function that is contributed by the lung segments to be removed. The equation for calculating the predicted postpneumonectomy lung function is postoperative FEV1 = preoperative FEV1 × perfusion (%) to the remaining lung. A modification of this equation has been proposed to predict the decrement in lung function after lobectomy: loss of function = preoperative FEV1 × functional segments in the lobe to be resected/total number of segments in both lungs.

Exercise Studies

In contrast with some previous studies, preoperative maximal and submaximal exercise testing has been shown to be a good predictor of postoperative pulmonary complications in patients undergoing pulmonary resection.16-19 Exercise testing may better predict adverse outcomes by uncovering deficits in O2 transport or cardiac function. A maximal oxygen consumption of less than 1 L/min is associated with a 75% mortality rate, whereas death is rare if oxygen consumption is more than 1 L/min. Additional exercise-related criteria indicating increased risk for pulmonary resection include (1) pulmonary vascular resistance more than 190 dynes/s/cm5 (with exercise), (2) arterial oxygen desaturation more than 2% with exercise, and (3) maximal oxygen consumption less than 15 mL/kg/min. Disadvantages of exercise testing are that it depends on patient effort and cooperation, and it requires special equipment and trained personnel to administer the tests.

Right Heart Function

Patients who are to undergo thoracotomy and lung resection frequently have a long-standing history of smoking and underlying COPD, which can lead to pulmonary arterial hypertension and its sequelae. Pulmonary arterial hypertension results from an increase in pulmonary vascular resistance (PVR) caused by a reduction of cross-sectional area of the pulmonary vascular bed associated with the destruction of the alveolar septa and hypoxemia-induced pulmonary vasoconstriction. Over time, pulmonary hypertension can lead to right ventricular hypertrophy, cor pulmonale, and eventually right ventricular failure. The normal pulmonary vascular bed can tolerate an increase in cardiac output of 250% without an increase in pulmonary artery pressure. In contrast, even a small increase of cardiac output causes a large increase in pulmonary artery pressure in patients with a restricted pulmonary vascular bed. Preexisting impairment of pulmonary vascular compliance associated with congestive heart failure and cor pulmonale may be exacerbated after extensive lung resection, leading to serious pulmonary hypertension and right-sided heart failure. The preoperative evaluation of these patients should assess for signs and symptoms of pulmonary hypertension, right ventricular and right atrial hypertrophy, cor pulmonale, and congestive heart failure (Boxes 54-2 and 54-3). A fixed elevated PVR has been associated with an increased risk of complications.6 In an attempt to simulate the cardiovascular effects of pneumonectomy, patients can undergo a right heart catheterization with occlusion of the affected pulmonary artery. The criteria for inoperability include (1) an increase in mean pulmonary artery pressure to more than 35 to 40 mm Hg, (2) an increase in Paco2 to greater than 60 mm Hg, and (3) a decrease in Pao2 to less than 45 mm Hg (see Box 54-1).6,20,21

Box 54-2

Box 54-2

Clinical Signs and Symptoms of Pulmonary Hypertension, Right Ventricular Hypertrophy, and Cor Pulmonale

Patient has prominent neck veins and prominent A waves, and perhaps prominent V waves are seen on electrocardiogram.

Prominent left parasternal heave and rocking motion synchronous with heart beat may be present.

Dullness to percussion over left second intercostal space near sternum may be present, indicating dilation of main pulmonary artery. However, if too much emphysema is present, entire precordium may be resonant because of hyperinflation of lungs.

On auscultation, pulmonary component of second heart sound increases, with narrowing or loss of normal splitting in second heart sound.

High-pitched, early systolic ejection click is heard.

Systolic ejection murmur is present.

Right-sided atrial S4 gallop usually indicates increased right ventricular end-diastolic pressure and may coincide with prominent A waves in jugular venous pulse. S4 gallop usually is not ominous.

Mid-diastolic right-sided S3 gallop usually is evidence of impaired right ventricular function and is usually ominous. Right-sided gallops can be differentiated from left-sided gallops because they increase in intensity with inspiration.

Early diastolic, pulmonary regurgitant murmur may indicate functional pulmonary insufficiency caused by dilation of root of pulmonary artery and pulmonic valve.

Right-sided heart failure with chronic, dependent edema; large, tender liver; ascites; positive, hepatojugular reflex; and dilated, distended, pulsating neck veins are signs.

Box 54-3

Box 54-3

Radiographic Signs of Pulmonary Hypertension

Dilation of main pulmonary vessels

Attenuation of peripheral pulmonary vasculature, leading to oligemic peripheral lung zones

Radiographic findings characteristic of chronic obstructive pulmonary disease, such as hyperinflated lungs and low, flat diaphragms

Manifestations of right ventricular hypertrophy, clockwise cardiac rotation, and loss of air space behind sternum on lateral chest radiograph

Preoperative Preparation of the Patient Undergoing Thoracic Surgery

The preoperative preparation of the patient for thoracic surgery should focus on treatable conditions.2-5,22 Stein et al23 found that postoperative complications developed in 4 of 17 well-prepared patients compared with 13 of 17 unprepared patients. Prophylactic measures, such as bronchodilator therapy, hydration, and chest physical therapy, decrease the incidence of postoperative complications and should be started preoperatively and continued postoperatively. In addition, preoperative patient education about the importance of cessation of smoking, incentive spirometry, and bronchodilator therapy also are beneficial.

Cessation of smoking for at least 4 to 8 weeks before surgery is associated with decreased incidence of postoperative respiratory complications.8,24 Although cessation of smoking for 12 to 24 hours preoperatively does not decrease the incidence of postoperative respiratory complications, it still may have a salutary effect by decreasing the concentration of carboxyhemoglobin. Other beneficial effects of stopping smoking several weeks before surgery include decreasing sputum production and improving ciliary activity.24,25

Elective operations should be postponed in patients with acute exacerbation until proper management has been instituted. Sympathomimetic drugs can be administered to activate β2-adrenergic receptors, increasing intracellular cyclic adenosine monophosphate (AMP) and leading to bronchodilation. Bronchodilation also can be produced by parasympatholytics, like ipratropium bromide, which inhibit parasympathetic vagal tone of the tracheobronchial tree. Other management for wheezing includes the administration of steroids to suppress inflammation and decrease mucosal edema. Because they are slow to act, their benefit in a patient with acute bronchospasm is debatable.

Mobilization of secretions and improved pulmonary toilet improve perioperative pulmonary function. Mobilization of secretions is achieved by a combination of deep breathing, vigorous coughing, postural drainage, hydration, and chest percussion.26,27 However, chest physical therapy is relatively contraindicated in patients with lung abscesses, pulmonary metastases, or a history of hemoptysis.

Acute and chronic infection should be managed vigorously with antibiotics before operation. A change in the color and quantity of sputum produced by a patient with COPD may indicate infection. One prospective study reported decreased incidence of postoperative pulmonary complications and mortality rate in patients treated with prophylactic antibiotics before pulmonary operations.28

Preoperative pulmonary rehabilitation should be considered for all patients. It typically includes all of the steps reviewed previously along with structured exercise. Compared with education alone, comprehensive pulmonary rehabilitation has produced a significant increase in 6-minute walk test,29 maximal exercise tolerance,30 maximal oxygen uptake,30 and quality of life measures.29,30 Although these interventions have been shown to decrease postoperative pulmonary complications,31 the programs need to be initiated 24 weeks prior to surgery to achieve maximal effectiveness.29 Even then the effect on perioperative morbidity and postoperative outcome remain controversial.32-35

Lung Cancer

Classification

Lung cancer is currently the most common cause of cancer mortality in the United States and throughout the world. The World Health Organization (WHO) classification of lung tumors, revised most recently in 2004, remains the foundation for lung carcinoma nomenclature.36 The characterization of lung carcinomas by histopathologic subtype is the basis of formal classification and has implications for management and prognosis. Lung cancer is divided into several broad categories based on histology: adenocarcinoma (25%), squamous cell carcinoma (SCC, about 35%), large cell carcinoma, adenosquamous carcinoma, carcinoid tumors, and carcinomas with pleomorphic elements.

Classically, the therapeutic approach to lung cancer depends on the histologic type of tumor and its extent (stage). The most common staging classification, the TNM system, is based on cell type (T), extent of lymph node involvement (N), and metastatic spread (M) (Box 54-4). The TNM system is used to group patients into subsets or stages that have implications on treatment options, surgical resectability, and prognosis. Clearly, the revolution in genetics and move toward individualized targeted therapy will necessitate the inclusion of advanced diagnostics alongside classic TMN staging in determining potential therapies and outcome.37,38

Box 54-4

Box 54-4

Definitions for Staging Bronchogenic Carcinoma

Recent proposed changes in the classification system will potentially add subgroups based on tumor size (T) with cutoffs of 0-2 cm, 2-3 cm, 3-5 cm, and >5 cm in greatest dimension due to increasingly poor prognostic outcome.

Data adapted from Spiro SG. The diagnosis and staging of lung cancer. In: Smyth JR, ed. The Management of Lung Cancer. London, UK: Edward Arnold; 1984.

The approaches to therapy for small cell lung carcinoma (SCLC) and for non–small cell lung carcinoma (NSCLC) differ. Small cell carcinomas account for about 25% of all bronchogenic carcinomas and have a strong correlation with cigarette smoking. In general, SCLC has metastized by the time of diagnosis and is managed primarily by chemotherapy without radiotherapy. Non–small cell carcinomas often are more localized and thus better candidates for curative resection. Surgical resection is a standard component in an attempt to cure lung cancer in patients with stage I and II NSCLC. In addition to surgery, adjuvant chemotherapy may be administered for selected patients with stage IB and stage II disease. Although the value of resection has never been established through randomized trials, the favorable results in surgical series and the relative infrequency of long-term survival in patients treated without surgery establish surgery as the treatment of choice.39

Lobectomy, the surgical removal of an anatomic lung segment, is generally accepted as the optimal procedure for early-stage NSCLC, because of its ability to preserve pulmonary function.40 Limited (sublobar) resection is increasingly used to treat patients who cannot tolerate a full lobectomy because of severely compromised pulmonary function, advanced age, or other extensive comorbidity. In addition, advances in video-assisted thoracoscopic surgery (VATS) have facilitated the utilization of limited resections in selected patients.

Intrathoracic Metastatic Manifestations

Clinical manifestations of lung cancer are varied. Common symptoms include shortness of breath, hemoptysis, chest pain, and increasing dyspnea (Table 54-2). Pleural effusions are a common but nonspecific finding observed on chest radiographs. The effusions result from obstruction of lymphatic drainage or malignant extension of the tumor to the lung surface. Chest pain associated with lung cancer usually is a dull or mild nonspecific pain occurring ipsilateral to the tumor. Metastasis to the chest wall and ribs can result in local tenderness and pleuritic chest pain. Shoulder pain may result from tumor growth at the lung apex and invasion or encroachment of the brachial plexus (such as in Pancoast tumor). Tumor extension into the pericardium can result in pericarditis, cardiac dysrhythmias, and pericardial effusions that cause tamponade. In addition, superior vena cava obstruction by local growth or lymphatic metastases will impede venous return from the head and upper extremities. Its implications to clinical management will be discussed later in this chapter.

Table 54-2 Incidence of Various Clinical Manifestations on Initial Examination of Patients with Bronchogenic Carcinoma

Table 54-2 Incidence of Various Clinical Manifestations on Initial Examination of Patients with Bronchogenic Carcinoma

Clinical Manifestation

Incidence (%)

Asymptomatic

5

Bronchopulmonary

Cough
Hemoptysis
Chest pain
Dyspnea
Wheezing

75

57

40

30

10

Extrapulmonary intrathoracic

Hoarseness
Superior vena cava syndrome
Chest wall pain
Pain radiating into upper extremity
Horner syndrome
Dysphagia
Pleural effusion

5

4

5

<5

1

10

Extrathoracic metastatic

Liver skeleton
Adrenals
Gastrointestinal tract
Kidneys
Pancreas

3-6

Extrathoracic nonmetastatic (paraneoplastic)

Endocrine/metabolic
Neuromuscular
Skeletal
Dermatologic
Hematologic

2

Nonspecific

Weight loss
Weakness
Anorexia
Lethargy
Malaise
Fever

10-22

Based on data from Landais A, Morin JP, Roche A, et al. Measurement of cardiac output by the thermodilution method during left horacotomy in the lateral position in the dog. Acta Anaesthesiol Scand. 1990;34:158-161; Hoppin FG Jr, Green ID, Mead J. Distribution of pleural surface pressure in dogs. J Appl Physiol. 1969;27:863-873; and Rehder K, Wenthe FM, Sessler AD. Function of each lung during mechanical ventilation with ZEEP and with PEEP in man anesthetized with thiopental-meperidine. Anesthesiology. 1973;39:597-606.

Other manifestations of lung cancer include neurologic symptoms caused by mechanical encroachment or invasion of the nerve plexus. Involvement of the brachial plexus may result not only in shoulder pain but also in upper arm weakness. Involvement of the phrenic nerve can lead to unilateral diaphragmatic dysfunction, and involvement of the recurrent laryngeal nerve can result in hoarseness of voice.

Extrathoracic Metastatic Manifestations

Common extrathoracic sites of metastases include lymph nodes, brain, bone, liver, skin, and suprarenal glands. The neurologic manifestations of metastatic brain tumors include hemiplegia, personality changes, cerebellar disturbances, seizures, headache, and confusion. Metastases to bone occur primarily in ribs, vertebra, humerus, and femur. Although metastases to the spinal cord and vertebral column are less common, they have implications for positioning and postoperative management of pain.

Extrathoracic Nonmetastatic Manifestations

The extrapulmonary manifestations of lung cancer affect the metabolic, neuromuscular, skeletal, dermatologic, vascular, and hematologic systems. Although uncommon, the systemic manifestations of such paraneoplastic syndromes can have an impact on the perioperative treatment. The metabolic and neuromuscular manifestations are more likely to affect perioperative management (Box 54-5). In general, the symptoms resolve and laboratory studies return to normal after a successful tumor resection.

Box 54-5

Box 54-5

Classification of Extrapulmonary Manifestations of Lung Carcinoma

Metabolic

Cushing syndrome

Excessive antidiuretic hormone

Carcinoid syndrome

Hypercalcemia

Ectopic gonadotropin

Insulinlike activity

Neuromuscular

Carcinomatous myopathy

Peripheral neuropathies

Subacute cerebellar degeneration

Encephalomyelopathy

Skeletal

Clubbing

Pulmonary hypertrophic osteoarthropathy

Dermatologic

Acanthosis nigricans

Scleroderma

Other dermatoses

Vascular

Migratory thrombophlebitis

Nonbacterial verrucal endocarditis

Arterial thrombosis

Hematologic

Anemia

Fibrinolytic purpura

Nonspecific leukocytosis

Polycythemia

Data adapted from Shields TW. Carcinoma of the lung. In: Shields TW, ed. General Thoracic Surgery. 2nd ed. Philadelphia, PA: Lea & Febiger; 1983.

Metabolic manifestations usually result from endocrine secretions by the tumor.

Cushing syndrome most often is associated with small cell carcinoma of the lungs; it is characterized by increased elevations in adrenal corticotrophic hormone (ACTH).
The syndrome of excessive antidiuretic hormone (ADH), which is associated with small cell carcinoma, may manifest as nausea, vomiting, anorexia, hyponatremia, seizures, or other neurologic disturbances.
Carcinoid syndrome is associated with the production of serotonin; it is diagnosed by elevated 5-hydroxyindoleacetic acid (5-HIAA).
Hypercalcemia, which is associated with hypophosphatemia, results from a parathyroid hormone–like polypeptide secreted most often by bronchogenic carcinoma.
Hypoglycemia and ectopic gonadotropin production are rare manifestations.
The neuromuscular manifestations are the most frequent extrathoracic nonmetastatic effects of lung cancer, most often small cell carcinoma of the lung.41 The paraneoplastic myopathy, Eaton-Lambert syndrome, may appear as a myasthenic-like syndrome characterized by proximal muscle weakness, particularly of the pelvic and thigh muscles. The defect in neuromuscular transmission is a result of an antibody-mediated impairment of presynaptic neurocalcium channel activity, which reduces the release of acetylcholine.42,43 Patients with this syndrome do not respond as well to anticholinesterase drugs as do patients with myasthenia gravis. In contrast, these patients exhibit an increased sensitivity to succinylcholine and nondepolarizing muscle relaxants.
Other neuromuscular manifestations include subacute cerebral degeneration, encephalomyelopathy, and polymyositis. The cause and the pathogenesis of these neuropathies are not completely understood. Immunologic factors are believed to be important because antibody and T-cell responses are directed against shared antigens that are ectopically expressed by the tumor, but otherwise are exclusively expressed by the nervous system.44,45

Monitoring during Thoracic Anesthesia

The treatment of patients undergoing thoracic surgery is one of the most challenging aspects of anesthesiology. The patients usually have underlying respiratory and cardiac disease, which is altered further by surgical manipulations, operative position, and periods of lung collapse and 1-lung ventilation, which worsen V/Q mismatches. Thus it is extremely important to constantly monitor oxygenation and ventilation. There is disagreement about the need for invasive monitoring for patients undergoing thoracotomy. Monitoring should be individualized, depending on the extent of operation and the patient's underlying cardiovascular and respiratory disease (Table 54-3). (Please refer to Chapters 30-32.)

Table 54-3 Use of Monitoring to Detect and Diagnose Intraoperative Events

Table 54-3 Use of Monitoring to Detect and Diagnose Intraoperative Events

Respiration

Pattern, respiratory rate
Auscultation
Airway pressure

Apnea, respiratory difficulty, rales
Wheezing, rhonchi, apnea, compliance
Obstruction, pneumothorax, bronchospasm, secretions

Oxygenation

Fio2 analyzer
Pulse oximetry
Arterial blood gas

Inadvertent hypoxia
Hypoxia, integrity of pulse
Acidosis (metabolic, respiratory)

Ventilation

Capnography

Bronchospasm
Hypoventilation and apnea
Confirm endotracheal intubation
Return of spontaneous ventilation during controlled ventilation

Cardiovascular Function

Electrocardiography
Intra-arterial catheter

Arrhythmia, ischemia
Hypotension or hypertension
Arterial compression

Pulmonary artery catheter

Pulmonary hypertension, filling pressures, assess cardiac performance

Svo2

Adequacy of cardiac output

Transesophageal echocardiography

Ischemia, volume status, right ventricular dysfunction

Monitoring for patients undergoing thoracic surgery includes ECG, pulse oximetry, blood pressure, and capnography. Other noninvasive monitors provide crucial information. Auscultation for wheezing, rales, or rhonchi assist in the diagnosis of endotracheal tube malposition, congestive heart failure, airway disconnect, or bronchospasm. Airway pressures give valuable information about changes in lung compliance, the occurrence of bronchospasm, or malposition of the double-lumen endotracheal tube. Perioperatively, pulse oximetry is the most valuable monitor for early diagnosis of problems with oxygenation. Capnography gives a continuous display of the CO2 waveform and alerts the anesthesiologist to apnea, airway disconnects, and hypoventilation. End-tidal CO2 is usually 5 mm Hg less than the arterial Pco2; the difference between them will increase as ventilation perfusion matching worsens as in the case of 1-lung ventilation or pulmonary disease.

The anesthesiologist may require additional monitoring, such as systemic arterial or pulmonary arterial catheters, when caring for patients with a history of pneumonia, cardiac disease, or major anatomic pulmonary resection. Intra-arterial catheters are routinely used to monitor arterial blood gases and hemodynamics during major anatomic resections.

The pulmonary artery (PA) catheter is used to monitor cardiac output, left ventricular function, pulmonary artery pressures, and mixed venous oxygenation. It can be used to assess the effect of pulmonary resection on right ventricular function because patients with preoperative cardiac dysfunction are at risk of acute right ventricular failure after a pulmonary resection. A dramatic increase in pulmonary artery pressures during temporary clamping of vessels might contraindicate such resection. More than 90% of PA catheters float into the right lung.46 During a right thoracotomy with the patient in the left lateral decubitus position, the PA catheter is in the nondependent lung. Although 1 study found that the pulmonary artery catheter in the nondependent lung underestimated measured cardiac output values, other clinical and animal studies found no difference whether the thermistor was located in the main trunk or branches of the pulmonary artery or in the dependent or nondependent lung.47-49 Thus accuracy and clinical interpretation of PA pressures and PA occlusion pressures must account for the location of the PA catheter in relation to the patient positioning, mode of ventilation, blood flow, and hypoxic pulmonary vasoconstriction (HPV). It is exceedingly rare for the authors to use a PA catheter during thoracic surgery due to its variable reliability and risk of inclusion in the arterial staple line.

Lateral Decubitus Position

The lateral decubitus position (or some variation of it) is common during thoracic surgery (Table 54-4). It allows for complete access to the hemithorax and permits extending the incision anteriorly and posteriorly. It offers access to the pleural cavity, the hilar vessels, the lateral pericardium, and the descending thoracic aorta. The lateral decubitus position is used for patients undergoing pulmonary surgery and operations on the esophagus, thoracic aorta, thoracic spine, and certain cardiac procedures. This position may affect pulmonary, cardiovascular, and neurologic physiology. Orientation of 1 lung in a more dependent position alters pulmonary mechanics and increases the risk of contaminating the dependent lung with blood and purulent materials. The dependent lung has decreased functional residual capacity (FRC) and increased airway closure and atelectasis. Increased pulmonary blood flow and reduced ventilation to the dependent lung results in ventilation and perfusion abnormalities when both lungs are ventilated, although the increased blood flow to the dependent lung is advantageous during single-lung ventilation.

Table 54-4 Various Patient Positions Used during Thoracic Surgery

Table 54-4 Various Patient Positions Used during Thoracic Surgery

Position

Possible Surgical Incisions

Clinical Application

Supine

Median sternotomy

Cardiac surgery, mediastinal, major liver, vascular trauma

Bilateral intercostal transverse sternotomy

Repair pectus excavatum, bilateral lung transplant

Anterior or anterolateral incisions: side to be incised can be slightly elevated

Pericardial tamponade, lung biopsy

Upright

For minor thoracic procedures during local anesthesia

Used in high-risk patients (eg, open drainage of empyema) and for biopsy of lung or pleura

Lateral decubitus (90 degree angle to table)

Anterolateral and posterolateral thoracotomy incisions

Standard thoracotomy position

To provide optimal access for cardiac, thoracic, vascular, or gastrointestinal pathology, the obliqueness of the patient's back to the table can vary between 45 degree and 135 degree.

Anterolateral and posterolateral thoracotomy

Anterior thoracotomy

Thoracoabdominal incisions

To improve exposure in certain cardiothoracic, vascular, or gastroesophageal procedures

Tracheal or esophageal surgery, thyroid or vascular trauma, penetrating neck injuries

Thoracoabdominal aortic surgery

The lateral decubitus position is associated with serious hazards (see Chapter 27). To avoid complications, special attention should be given to the orientation of the cervical spine, positioning of the extremities, and placement of straps to anchor the body. A chest roll should be placed under the axilla to prevent compression of neurovascular structures by the head of the humerus. Such compression decreases the fidelity and accuracy of the systemic blood pressure monitoring in the dependent arm. The use of a soft contour bag ("bean bag") is advocated because it not only functions as a chest roll but also supports the patient and decreases the risk of pressure necrosis by molding to the patient's body. Patients often are flexed to open the intercostal spaces and to facilitate the introduction of cameras or surgical instruments. Additionally, slight flexion of the dependent hip and knee help stabilize the patient and decrease stretch of the sciatic nerve. The nondependent leg is positioned on a pillow to avoid pressure on the dependent leg. Positioning of the upper extremities and the head require special attention to avoid compression or stretch injury to the brachial plexus and peripheral nerves. The cervical spine is placed in a neutral position, and the dependent arm is outstretched (Fig. 54-4). The nondependent arm is elevated superiorly on an arm board to bring the vertebral border of the scapula forward. The decubitus position is further stabilized by placing straps or tape across the table at the level of the hip and across the leg, paying attention to avoid compression of tissue.

Figure 54-4.

Standard right lateral decubitus position. A. Improper head position and inadequate padding. B. Proper padding over bony prominences, chest roll to protect axilla, proper alignment of cervical spine. Flexed lower leg stabilizes torso.

The standard lateral decubitus position may be modified to facilitate surgical exposure. Slight rotation of the upper chest from 90 degree permits better access for more anterior or posterior incisions. Positioning of the nondependent arm in a more cephalad and abducted orientation permits a surgical approach that preserves the integrity of the latissimus and pectoralis muscles, "muscle-sparing approach."

Proper positioning of the endobronchial tube should be reconfirmed after patient repositioning, because slight flexion or extension of the neck can displace the endotracheal tube. Flexion of the neck moves the endotracheal tube distally, whereas extension of the neck moves the tube proximally. Confirmation of tube position with fiberoptic endoscopy decreases the incidence of inadequate lung isolation.

Physiology: Principles of Ventilation and Perfusion

Disparity between the greater gravitational pressures at the base and the greater negative intrapleural pressure at the apex are major factors in understanding normal ventilation and perfusion. Gravitational hydrostatic pressure causes distention of vessels and increased perfusion in the more dependent portions of the lung (Fig. 54-5). The apices of the lung may have little or no perfusion. In addition, the effects of gravity tend to collapse the apex of the lung inward and create a negative intrapleural pressure, whereas the lower dependent regions tend to push outward toward the chest wall and create a relatively positive pressure. Because the density of the lungs is 25% that of water and because the height of the upright lung is about 30 cm, the difference between the intrapleural pressure at the base of the lung versus the apex is approximately 7.5 cm water.50 Because the intra-alveolar pressure is the same throughout the lung, the transpulmonary distending pressure is greatest at the top of the lung and decreases toward the bottom. Therefore, the alveoli in the apices are largest, and those in the base are the smallest. Approximately a 4-fold alveolar volume difference exists between the base and the apex of the lung (Fig. 54-6). The small alveoli in the base of the lung are on the steep portion of their compliance curve, whereas the nondependent alveoli are on the relatively flat, noncompliant portion of the curve. Therefore, in the upright position, the tidal volume is preferentially distributed to the basilar alveoli, because they expand more per unit pressure change than the apical alveoli. These physiologic effects result in greater increases in blood flow (Q) than the increase in ventilation (V), and the ventilation-to-perfusion ratio decreases from the lung apex to the base (Figs. 54-7 and 54-8).

Figure 54-5.

Schematic diagram shows the distribution of blood flow in the upright lung. In zone 1, alveolar pressure (PA) exceeds pulmonary artery pressure (Ppa), and no flow occurs because the intra-alveolar vessels are collapsed by the compressing alveolar pressure. In zone 2, arterial pressure exceeds alveolar pressure, but alveolar pressure exceeds pulmonary venous pressure (Ppv). Flow in zone 2 is determined by the arterial-alveolar pressure difference (Ppa − PA) and has been likened to an upstream river waterfall over a dam. Because Ppa increases down zone 2 and PA remains constant, the perfusion pressure increases, and flow steadily increases down the zone. In zone 3, pulmonary venous pressure exceeds alveolar pressure, and flow is determined by the arterial-venous pressure difference (Ppa − Ppv), which is constant down this portion of the lung. The transmural pressure across the wall of the vessel increases down this zone so that the caliber of the vessels increases (resistance decreases), and therefore flow increases. Finally, in zone 4, pulmonary interstitial pressure becomes positive and exceeds pulmonary venous pressure and alveolar pressure. Consequently, flow in zone 4 is determined by the arterial-interstitial pressure difference (Ppa − PISF). [Redrawn from West JB. Ventilation Blood Flow and Gas Exchange. 4th ed. Oxford: Blackwell Scientific and Journal of Applied Physiology; 1985.]

Figure 54-6.

During quiet breathing, the lower parts of the lung show greater volume changes (ventilation) than the upper parts. [From Weibel ER, ed. The Pathway for Oxygen: Structure and Function in the Mammalian Respiratory System. Cambridge, MA: Harvard University Press; 1984.]

Figure 54-7.

Distribution of ventilation and blood flow (left vertical axis) and the ventilation-to-perfusion ratio (right vertical axis) in normal upright lung. Blood flow and ventilation are expressed in liters per minute percentage alveolar volume and have been drawn as smoothed out linear functions of vertical height. The closed circles mark the ventilation-to-perfusion ratios of horizontal lung slices (3 of which are shown in Fig. 54-8). A cardiac output of 6 L/min and a total minute ventilation of 5.1 L/min were assumed. [From West JB. Ventilation/Blood Flow and Gas Exchange. 4th ed. Oxford: Blackwell Scientific; 1985.]

Figure 54-8.

Ventilation-to-perfusion ratio (V̇/Q) and the regional composition of alveolar gas. Values for the regional flow (V̇/Q), ventilation (VA), Po2, and Pco2 are derived from Fig. 54-7. Pn2 has been obtained by what remains from the total gas pressure (which, including water vapor, equals 760 mm Hg). The volumes (vol [%]) of the 3 lung slices also are shown. Compared with the top of the lung, the bottom of the lung has a low V/Q ratio and is relatively hypoxic and hypercapnic. [From West JB. Regional differences in gas exchange in the lung of erect man. J Appl Physiol. 1962;17:893.]

Physiology: Lateral Decubitus Position

Patient Awake, Spontaneously Breathing

Gravity causes a vertical gradient in the distribution of pulmonary blood flow in the lateral decubitus position for the same reason it does in the upright position (Fig. 54-9). The vertical hydrostatic gradient is less than it is in the upright position because the distance from the most dependent to the most nondependent part of the lung is less. Nevertheless, blood flow to the dependent lung still is much greater than blood flow to the nondependent lung. Normally, in the upright position, the right lung, because of its larger size, receives 55% of the total blood flow, whereas the left lung receives 45% of total blood flow.51,52 When the right lung is nondependent, it receives approximately 45% of total blood flow, whereas the dependent left lung receives 55% of the total blood flow. When the left lung is nondependent, it receives approximately 35% of the total blood flow, whereas 65% goes to the dependent right lung. As in the upright position, ventilation also is relatively increased in the dependent lung zones (Fig. 54-10).

Figure 54-9.

Schematic representation of the effects of gravity on the distribution of pulmonary blood flow in the lateral decubitus position. Vertical gradients in the lateral decubitus position are similar to those in the upright position and cause the creation of zones 1, 2, and 3. Consequently, pulmonary blood flow increases with lung dependency and is largest in the dependent lung and least in the nondependent lung. [Modified from Benumof J. Anesthesia for Thoracic Surgery. Philadelphia, PA: Saunders; 1987.]

Figure 54-10.

Pleural pressure in the awake patient (closed chest) is most positive in the dependent portion of the lung, and alveoli in this region therefore are most compressed and have the least volume. Pleural pressure is least positive (most negative) at the apex of the lung, and alveoli in this region therefore are least compressed and have the largest volume. When these regional differences in alveolar volume are translated to a regional transpulmonary pressure-alveolar volume curve, the small dependent alveoli are on a steep (large-slope) portion of the curve, and the large nondependent alveoli are on a flat (small-slope) portion of the curve. In this diagram, regional slope equals regional compliance. Thus for a given and equal change in transpulmonary pressure, the dependent part of the lung receives a much larger share of the tidal volume than the nondependent part of the lung. In the lateral decubitus position (right side of diagram), gravity also causes pleural pressure gradients and therefore similarly affects the distribution of ventilation. The dependent lung lies on a relatively steep portion, and the upper lung lies on a relatively flat portion of the pressure–volume curve. Thus in the lateral decubitus position, the dependent lung receives most of the tidal ventilation. [Modified from Benumof J. Anesthesia for Thoracic Surgery. Philadelphia, PA: Saunders; 1987.]

In addition, in the lateral decubitus position, the dome of the lower diaphragm is pushed higher into the chest than the dome of the upper diaphragm and is therefore more stretched and sharply curved than the upper diaphragm. This gives the dependent diaphragm more efficiency during spontaneous ventilation. Thus in the lateral decubitus position with an awake, spontaneously breathing patient, the dependent lung is better ventilated than the nondependent lung, and V/Q still is well matched.53

Patient Anesthetized, Chest Closed

In the anesthetized, spontaneously breathing patient in the lateral decubitus position, the dependent lung continues to receive relatively more perfusion than the nondependent lung. The distribution of ventilation changes after the induction of anesthesia (Fig. 54-11).51,54 With the induction of general anesthesia, FRC decreases. Both lungs share in the loss of lung volume and move to a lower location on the pressure–volume curve. The dependent lung now occupies the low, flat portion of the curve (ie, is less compliant). The nondependent lung, initially in the noncompliant part, now moves to the steep compliant part of the curve. Compression by the weight of the mediastinum and the abdominal contents contribute to the decrease in FRC of the dependent lung. Therefore, with the induction of anesthesia, little change occurs in perfusion distribution, whereas dramatic change occurs in ventilation distribution. Now the nondependent lung receives most of the ventilation but still is less perfused, whereas the dependent lung receives less ventilation but continues to be more perfused, which leads to an increase in shunt (dependent lung has a low V/Q ratio) and dead space ventilation (nondependent lung has a V/Q ratio >1).

Figure 54-11.

The left side of the schematic shows the distribution of ventilation in the awake patient (closed chest) in the lateral decubitus position, and the right side shows the distribution of ventilation in the anesthetized patient (closed chest) in the lateral decubitus position. The induction of anesthesia has caused a loss in lung volume in both lungs, with the nondependent (up) lung moving from a flat, noncompliant portion to a steep, compliant portion of the pressure–volume curve and the dependent (down) lung moving from a steep, compliant part to a flat, noncompliant part of the pressure–volume curve. Thus the anesthetized patient in a lateral decubitus position has most of the tidal ventilation in the nondependent lung (where there is the least perfusion) and the minority of the tidal ventilation in the dependent lung (where there is the most perfusion). [Modified from Benumof J. Anesthesia for Thoracic Surgery. Philadelphia, PA: Saunders; 1987.]

Patient Anesthetized, Paralyzed, Mechanically Ventilated

Mechanical ventilation causes further deterioration in the V/Q relationship. Perfusion continues to be more to the dependent lung because of gravitational effects, but now there is even more distribution of ventilation to the nondependent lung. With the institution of mechanical ventilation, the highly curved diaphragm in the dependent hemithorax no longer confers any advantage in ventilation because it is no longer actively contracting.55 In addition, the weight of the abdominal viscera physically restricts expansion of the dependent lung, leading to further preferential distribution of ventilation to the nondependent, less-perfused lung. The anesthetized patient in the lateral decubitus position has an unfavorable V/Q ratio that is made worse by muscle relaxation and controlled ventilation. The application of PEEP to both lungs restores their FRC and most ventilation to the dependent lung.51 The lower lung returns to a steeper, more favorable part on the pressure–volume curve, and the upper lung resumes its original position on the flat, unfavorable portion of the curve.

Patient Anesthetized, Chest Open

In the spontaneously ventilating patient with an open chest, the inspiratory tidal volume in the dependent lung is decreased by the downward displacement of the mediastinum, which leads to impairment in ventilation to the dependent lung and paradoxic respiration. Paradoxic respiration refers to the movement of air between the dependent lung and the nondependent lung during respiration and the ambient atmosphere in and out of the open chest cavity. These physiologic changes also can affect circulatory performance by decreasing venous return and triggering associated sympathetic reflexes, resulting in a clinical picture similar to shock. The reflex symptoms of hypotension, pallor, cold and clammy extremities, and pupillary dilatation can be lessened by local anesthetic infiltration of the pulmonary plexus at the hilum. Most commonly, the ventilatory and circulatory changes associated with mediastinal shift are abolished by positive-pressure ventilation.

Patient Anesthetized, Mechanically Ventilated, Chest Open

Opening the chest results in a marked increase in the compliance of the upper lung, with a slight but still important increase in the compliance of the dependent lung. Airway pressure decreases in the dependent and the nondependent lung. As a result, ventilation of the nondependent lung increases further compared with the closed-chest state.56 The cardiac index increases with opening of the chest and pleura, but mean arterial pressure does not change drastically.57

The upper lung eliminates more CO2 shortly after the pleura has been opened.57 The increased elimination of CO2 from the upper lung is proportionately greater than the increase in ventilation. Also, the end-tidal Pco2 measured from the upper lung increases more than that of the lower lung, which reflects a marked increase in the blood flow to the upper lung. The decrease in airway pressure on opening the pleura, along with the increase in cardiac index, results in increased blood flow to the nondependent lung.

Effect of PEEP

Selective PEEP application to the dependent lung can improve oxygenation by decreasing the shunt fraction. The explanation is that PEEP to the dependent lung increases the FRC of that lung, moving it to a steeper, more favorable portion on its pressure–volume curve and leading to improved ventilation of the dependent lung. Even if the increase in pulmonary vascular resistance caused by the application of PEEP shifts blood flow from the dependent to the nondependent lung, that portion of the cardiac output diverted to the nondependent lung still participates in gas exchange as long as it is ventilated or exposed to CPAP.

Effects of Surgical Manipulation

With the onset of surgical manipulations, compliance and distribution of ventilation to the upper lung decrease dramatically. End-tidal Pco2 and CO2 elimination from the upper lung decrease greatly, but changes in Paco2 are minimal.57

Summary

The anesthetized, paralyzed patient in the lateral decubitus position with an open chest may have considerable V/Q mismatch. The nondependent lung receives greater ventilation and less perfusion and has a V/Q ratio of more than 1. The dependent lung has more perfusion and less ventilation (ie, a low V/Q ratio) and therefore acts as a physiologic shunt. The blood flow distribution is mainly determined by effects of gravity. Causes of poor ventilation of the dependent lung are (1) loss of FRC because of induction of general anesthesia, (2) compression of the dependent lung by the mediastinum, (3) upward shift of the abdominal contents and paralysis of the diaphragm, (4) suboptimal positioning effects, (5) impaired ciliary clearance of mucus, and (6) absorption atelectasis from the use of high Fio2. Consequently, 2-lung ventilation in these patients may result in an increased alveolar-to-arterial Po2 difference and less than optimal oxygenation.

One-Lung Isolation

Indications

The techniques of lung isolation are used to selectively ventilate the lung within 1 hemithorax while the nearly motionless lung is operated on in the contralateral hemithorax. Collapse of the nondependent lung produces less trauma than surgical retraction and offers better exposure of structures within the hemithorax.58,59 The airways of the operated lung can be incised while positive pressure ventilation continues in the other lung. During thoracoscopic surgery, collapse of the operated lung is essential to provide adequate visualization of structures within the pleural cavity. Although many surgical procedures are greatly facilitated by the use of isolation techniques, most procedures are feasible without isolation.

Single lung isolation is absolutely indicated under certain clinical conditions. When one lung contains either blood or infectious secretions, isolation of the lungs becomes imperative to prevent spillage of contents into the unaffected lung. Isolated lung ventilation is essential when a bronchopleural or bronchocutaneous fistula would render positive pressure ventilation difficult or impossible. Further, directing ventilation toward the healthier lung may result in better oxygenation and ventilation.60 Some procedures require isolated ventilation, including open procedures on the trachea and mainstem bronchi, such as sleeve and carinal resections, and bronchopulmonary lavage for pulmonary alveolar proteinosis.

Design of Double-Lumen Tubes

Isolated lung ventilation usually is accomplished through a double-lumen endotracheal tube. The central shaft of a double-lumen endotracheal tube is cylindrical and contains a septum that divides it into 2 symmetric "D"-shaped lumens. At the proximal end of each lumen is a short length of tubing that creates a "Y" shape that permits independent attachment for ventilatory apparatus, clamping, or opening to atmospheric pressure. At the distal end, the shaft is surrounded by an inflatable tracheal cuff. The tracheal lumen terminates just below the tracheal cuff. The other lumen has a cylindrical extension, curved to fit into 1 of the mainstem bronchi, and carries an inflatable circumferential bronchial cuff. After the double-lumen endotracheal tube has been properly placed within the patient's airway, the bronchial cuff permits the bronchial lumen to be used for positive pressure ventilation or exclusion of the hemithorax in which it resides. The tracheal cuff provides a seal that directs pressurized gas from the tracheal lumen into the other bronchus. Thus a properly placed double-lumen endotracheal tube permits selective ventilation or collapse of either lung.

Double-lumen endotracheal tubes are manufactured with selective bronchial extensions intended for placement into either the left or right mainstem bronchus. The left main stem bronchus arises at a more acute angle with reference to the tracheal axis, but it is long enough to easily accommodate the endobronchial extension with its inflatable cuff. In contrast, the right mainstem bronchus is nearly a direct extension of the trachea, but it contains a branch to the right upper lobe bronchus that arises very close to the tracheal bifurcation (Fig. 54-12). A right-sided double-lumen endotracheal tube has a fenestration within the bronchial extension and an elaborately shaped cuff to permit a seal without airflow obstruction. Because of these considerations, right-sided tubes are more difficult to insert and require more maintenance to ensure continuous ventilation of all lobes of the right lung. In the absence of a specific indication for a right-sided double-lumen endotracheal tube, a left-sided tube is strongly preferred.

Figure 54-12.

Schematic representation of the most proximal and most distal acceptable positions of left- and right-sided double-lumen tubes and the relative margins of safety in positioning the various tubes. A. All left-sided double-lumen tubes. B. Mallinckrodt right-sided double-lumen tube has an "s"-shaped balloon for the occlusion of the right mainstem bronchus. C. Rusch right-sided double-lumen tubes use a "c"-shaped cuff on the endobronchial tube that seals off the right mainstem and isolates the right upper lobe. LMS, length of mainstem bronchus; LUL, left upper lobe; MS, margin of safety; RMS, length of right mainstem bronchus; RUL, right upper lobe.

Placement of Double-Lumen Tubes

Before placement of a double-lumen endotracheal tube, all necessary equipment including a laryngoscope, several double-lumen endotracheal tubes, and a fiberoptic scope should be assembled and tested. The type of tube is chosen based on the surgical procedure, and its size is based on the patient's body habitus (Table 54-5). Direct laryngoscopy with a curved (Macintosh) laryngoscope blade is preferred because the glottic opening is better exposed by it as compared to a straight blade. The double-lumen endotracheal tube is held with its bronchial curve oriented anteriorly and its tracheal-pharyngeal curve oriented to the right. The tube is advanced through the glottic opening until the bronchial cuff just passes the vocal cords. If a stylet was used, it is removed.

Table 54-5 Choice of Double-Lumen Endotracheal Tube

Table 54-5 Choice of Double-Lumen Endotracheal Tube

Tube Size (Fr)

Patient Height

M

F

Depth of Insertion (cm)

136-164 cm

37

35

27

4'5.5"-5'4.5"

165-179 cm

39

37

29

5'5"-5'10.5"

180-194 cm

41

39

31

5'11"-6'4.5"

F, female; Fr, French; M, male.

Modified from Brodsky JB, Benumof JF, Ehenworth J, et al. Depth of placements of left double-lumen endobronchial tubes. Anesth Analg. 1991;73:570-572, with permission.

There are 2 methods for the cannulation of the desired bronchus, empiric or "blind placement" and direct vision using fiberoptic assistance. In the first method, the tracheopharyngeal curve is then rotated anteriorly until the proximal end of the double-lumen endotracheal tube just passes the midsagittal axis. The bronchial curve should now be oriented to the side dictated by the type of tube, after which it is then advanced until moderate resistance to further insertion is encountered. A bifurcated connector is attached to the 2 lumens, and the tracheal cuff is inflated. Intubation of the trachea is then confirmed by capnography, auscultation, and observation of chest excursion. Once it has been determined that both lungs can be adequately ventilated, it is safe to proceed with confirmation that the tube is positioned to allow isolation of the 2 lungs. Correct placement can be determined by a series auscultation maneuvers whereby the tracheal and bronchial lumens are ventilated independently. However, this technique is time-consuming and may often prove inaccurate. The alternative method uses a bronchoscope to confirm placement. Each lumen of the bifurcated double-lumen endotracheal tube connector is fitted with a fenestrated membrane covered by a removable cap. While the lungs are ventilated with positive pressure, the fenestrated membrane on the tracheal lumen is uncovered, and the bronchoscope is passed through it into the double-lumen endotracheal tube to confirm placement. The alternative method of tube placement, which uses direct observation via a fiberoptic bronchoscope, is the most efficient method for confirming appropriate anatomic placement. The bronchoscope is steadily advanced through the tracheal lumen until its tip just exits from the distal opening. If the tube is properly positioned, the carina should be seen just beyond the opening, and the medial wall of the endobronchial extension should be seen entering the contralateral bronchus. The bronchial cuff should be entirely contained within the contralateral bronchus, while an unobstructed view of the opening into the ipsilateral bronchus is enjoyed. Disposable double-lumen tubes usually feature a prominent band around the endobronchial extension several millimeters above the endobronchial cuff to facilitate positioning. When ideally positioned, the band should lie at the level of the carina. It may be necessary to slightly advance or withdraw the tube to achieve the ideal position. Once anatomically correct tube position has been confirmed, it is secured in place and the endobronchial cuff is gently inflated under direct bronchoscopic visualization to ensure that the cuff does not herniate into the trachea. Each time the patient is repositioned, it is advisable to verify the position of the double-lumen endotracheal tube.

An alternative method of tube placement eliminates the possibility of placing the endobronchial extension in the wrong bronchus. The tube is passed through the cords and rotated as for the first method. It is advanced only until the tip of the bronchial extension is 20 to 22 cm beyond the central incisors as determined by markings on the shaft. The bronchial cuff is then inflated to seal against the wall of the trachea. An anesthetic circuit is attached to the connector for the bronchial lumen, and intubation of the trachea is confirmed. The bronchoscope is then passed into the bronchial lumen. After the tip of the bronchoscope has entered the trachea, it is advanced under direct visualization past the carina into the desired mainstem bronchus (Figs. 54-13 and 54-14). After the bronchoscope is advanced as far as possible, the bronchial cuff is deflated. Using the bronchoscope as a directing stylet, the double-lumen endotracheal tube is advanced until gentle resistance is met. The bronchoscope is withdrawn and placed in the tracheal lumen to confirm unimpeded access to the ipsilateral bronchus as in the first method. Once placement is confirmed, the tube is secured.

Figure 54-13.

Bronchoscopic guide for placement of single-lung ventilation devices. A. The bronchoscope is situated in the distal trachea. In this view, the carina is clearly visualized along with the anterior cartilaginous rings and the posterior striated membranous portion of the trachea. The takeoff of the right mainstem bronchus is more aligned with the trachea, predisposing for endobronchal intubation of the right mainstem bronchus when an endotracheal tube is advanced too far. The easiest way of absolutely identifying the main carina is to locate the right upper lobe (or the scar of the previously resected right upper lobe). Confirmation of the "true" left and right mainstem bronchi is the best way to ensure proper placement of the selective lung ventilation device. B. The bronchoscope is in the right mainstem bronchus, just proximal to the bronchus intermedius, which begins below the origin of the right upper lobe. Origin of the right upper lobe is variable but usually arises 1 to 1.5 cm past the carina between 2 and 4 o'clock. C. The bronchoscope is in right upper lobe bronchus. The right upper lobe branches into 3 segments: apical, posterior, and anterior. These 3 orifices are typically arranged in a "V" pattern, but they can also be oriented in a line. D. The bronchoscope is in the distal bronchus intermedius. The right middle lobe, which is to the right, immediately splits into the lateral and medial segments. It is possible to advance a double-lumen endotracheal tube distal enough down the right side that the endobronchial lumen will be in the right inferior lobe and that the tracheal lumen will expose the right middle lobe. The right middle lobe's lateral segment orifice could be confused for the right upper lobe orifice, but the right middle lobe's lateral segment does not subdivide like the right upper lobe. E. The bronchoscope is in the distal left mainstem bronchus. This view reveals the left upper and lower lobe bronchi. It is important to ensure that left-sided double-lumen tubes have not been too far advanced, leading to selective intubation of the left upper or lower lobes.

Figure 54-14.

Schematic diagram portraying the use of the fiberoptic bronchoscope to insert a left-sided double-lumen tube. A. The double-lumen tube can be put into the trachea in a conventional manner, and both lungs can be ventilated by both lumens. The fiberoptic bronchoscope may be inserted into the left lumen of the double-lumen tube through a self-sealing diaphragm in the elbow connector to the left lumen; this allows continued positive pressure ventilation of both lungs through the right lumen without creating a leak. After the fiberoptic bronchoscope has been passed into the left mainstem bronchus (B), it is used as a stylet for the after-coming left lumen (C). The fiberoptic bronchoscope is then withdrawn. Final precise positioning of the double-lumen tube is performed with the fiberoptic bronchoscope in the right lumen. [From Benumof JL. Separation of the two lungs (double-lumen tube and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]

Occasionally, double-lumen endotracheal tubes may be malpositioned. Three possible reasons are (1) the tube is so deeply inserted that the tracheal opening is beyond the carina; (2) the tube is not inserted far enough so that the bronchial cuff is above the carina; or (3) the endobronchial extension has entered the incorrect bronchus so that the tracheal lumen opening is trapped against the lateral wall of the trachea on the ipsilateral side (Fig. 54-15). Gently withdrawing or advancing the tube under direct bronchoscopic visualization should reveal and correct either of the first 2 causes. If the endobronchial extension is not in the correct bronchus, the tube is repositioned by inserting the fiberoptic bronchoscope in the endobronchial lumen and withdrawing the tube and scope until the carina is encountered, after which the tube and scope are advanced down the appropriate mainstem bronchus.

Figure 54-15.

There are 3 major (involving a whole lung) malpositions of a left-sided double-lumen endotracheal tube. The tube can be in too far on the left (both lumens are in the left mainstem bronchus), out too far (both lumens are in the trachea), or down the right mainstem bronchus (at least the left lumen is in the right mainstem bronchus). In each of these 3 malpositions, the left cuff, when fully inflated, can completely block the right lumen. Inflation and deflation of the left cuff while the left lumen is clamped creates a breath sound—differential diagnosis of tube malposition. (See text for full explanation). L, left; R, right; -, decreased. [From Benumof JL. Separation of the two lungs (double-lumen tube and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia: WB Saunders; 1987.]

Right-sided tubes require more vigilance and confirmation that the fenestration supplying the right upper lobe bronchus is positioned correctly. This is accomplished by passing the bronchoscope into the endobronchial lumen and observing the upper lobe bronchial orifice through the fenestration in the lateral wall of the endobronchial extension (Fig. 54-16).

Figure 54-16.

Schematic diagram portraying the use of a fiberoptic bronchoscope to determine precise right-sided double-lumen tube position. A. When the fiberoptic bronchoscope is passed down the left (tracheal) lumen, the endoscopist should see a clear straight-ahead view of the tracheal carina and the right lumen going off into the right mainstem bronchus. B. When the fiberoptic bronchoscope is passed down the right (bronchial) lumen, the endoscopist should see the bronchial carina off in the distance; when the fiberoptic bronchoscope is flexed cephalad and passed through the right upper lobe ventilation slot, the right upper lobe bronchial orifice should be visualized. [From Benumof JL. Separation of the two lungs (double-lumen tube and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]

Although confirmation of position through direct visualization with a fiberoptic bronchoscope usually is rapid and definitive, it is not always feasible. Further, although it assures anatomically correct position, it does not ensure functional isolation of the left and right lungs. Functional isolation is tested by selectively ventilating 1 lung while the other is vented to the atmosphere, and unilateral ventilation of the intended lung is confirmed by auscultation and visual or tactile observation. The opposite lung then is ventilated, and the test is repeated. A test for functional isolation should always be used when the double-lumen endotracheal tube is placed to prevent spillage of liquid from one lung to the other.

Complications

Complications associated with double-lumen endotracheal tubes can be divided into 2 types, those resulting from malposition of the tube and those caused by trauma to the tracheobronchial tree.

Malposition

Malposition may lead to failure either to ventilate segments of the dependent lung or to collapse the operative lung. Failure to ventilate segments of the ventilated lung can occur if the bronchial lumen obstructs the origin of the upper lobe bronchus, which frequently manifests by hypoxemia and increased peak airway pressures. A common cause of upper lobe obstruction is distal migration of the endobronchial lumen associated with flexion of the neck. Upper lobe obstruction is more common when a right-sided double-lumen endotracheal tube is inserted. Failure to collapse the nonventilated lung may interfere with the operation.

Cephalad migration of the double-lumen endotracheal tube can be caused by surgical manipulation, neck extension (occurs with placement of patient into lateral decubitus position), or by traction on an inadequately secured tube. As the tube withdraws, the bronchial cuff herniates over the carina into the trachea. When partially herniated, increased cuff pressure may force the cuff further into the trachea. The herniated cuff may partially or fully obstruct the contralateral mainstem bronchus, making that lung difficult or impossible to collapse (or ventilate).

Malposition of the tube should be suspected when there is a sudden increase in peak airway pressure, when hypoxemia occurs, or when inflation of the nonventilated lung is detected. Vigilance should be heightened immediately after repositioning the patient and during surgical manipulation near the hilum of the lung. At the first suspicion of a malpositioned double-lumen endotracheal tube, tube position should be confirmed immediately by fiberoptic bronchoscopy. If it is difficult to discern anatomy during an open thoracotomy, the surgeon may be able to manually guide the endobronchial lumen of the double-lumen endotracheal tube into the desired mainstem bronchus.

Traumatic Damage

Trauma to the tracheobronchial tree by double-lumen endotracheal tubes may include minor insults, such as ecchymosis of the mucous membranes, and more severe ones, like arytenoid dislocation or vocal cord rupture. Catastrophic tracheobronchial rupture has been reported.61-66 The multiple lumen design and relatively large size of double-lumen endotracheal tubes make them stiffer than conventional endotracheal tubes, thus increasing the risk of damage from forceful advancement against resistance. The stiffness is further increased by use of a rigid stylet during tube placement. Therefore, when use of a stylet is required for intubation of the trachea, it should be withdrawn before the bronchial lumen of the double-lumen endotracheal tube is advanced into the mainstem bronchus.

Injuries also may result from excessive pressure in either the tracheal or bronchial cuffs, leading to tissue necrosis or rupture. The small size and high-pressure bronchial cuff increases the risk of tissue injury from overinflation. Cuff pressure should be regularly monitored by palpation of the pilot balloon or by use of a calibrated device.

Failure to obtain a complete seal is especially hazardous when the double-lumen endotracheal tube is used to protect 1 lung from liquid contents within the other. The leak may allow spillage of liquid into the unaffected lung. Liquids include saline during bronchopulmonary lavage, pus from unilateral empyema, and blood from airway hemorrhage. In patients in whom a spillage occurs, a failed seal can lead to severe morbidity or death.

Contraindications

The principal contraindication to the use of a double-lumen endotracheal tube is the presence of a lumenal airway mass that may be dislodged or may prevent passage of the tube. Relative contraindications include critical dependence on bilateral mechanical ventilation in patients unable to tolerate its interruption, patients requiring rapid placement of an endotracheal tube to avoid aspiration of gastric contents, and patients in whom conventional tracheal intubation is judged to be difficult.

Alternative Methods of Lung Isolation

When collapse of the left lung and ventilation of the right is required or use of a double-lumen endotracheal tube is not feasible, a bronchial blocker can be placed in the left mainstem bronchus. In addition, this strategy eliminates the risk of losing the airway while changing the endotracheal tube at the end of the case for patients requiring postoperative ventilation. Specific bronchial blockers having a patent central lumen to permit deflation of the distal airway have been developed. The Ardnt® catheter has a nylon loop that is used to ensnare the distal portion of the fiberoptic scope as it is advanced in the selected mainstem bronchus.67,68 The loop is loosened and advanced distal to the fiberoptic scope. Another variation, the Cohen endobronchial blocker®, incorporates a small wheel that is used to deflect the tip of the catheter into the selected bronchus.69,70 Under direct vision, the catheter is slowly withdrawn until the inflated balloon is just distal to the level of the carina. In an emergency, an angled Fogarty catheter is inserted through the endotracheal tube under radiographic or fiberoptic guidance into the desired bronchus.71 Absence of a patent lumen extending below the balloon of Fogarty catheters prevents suctioning or oxygen delivery to the occluded lung segment. Bronchial blockers produce less risk of hoarseness and vocal cord injury,72 but they are more difficult to use when the surgeon requests intermittent insufflation or for application of continuous positive airway pressure (CPAP) to the operative lung.

Endobronchial intubation with a single-lumen tube offers an alternative to the double-lumen endotracheal tube that can be especially useful in emergencies. Disadvantages of using a single-lumen tube include loss of ability to selectively ventilate or suction the contralateral lung and increased difficulty in placing or ascertaining correct placement of the tube. Endobronchial intubation is especially useful for patients who require emergent tracheal intubation for massive hemoptysis. For adults, endobronchial intubation requires a tube of adequate length, often more than 31 cm, to ensure that the entire cuff is placed below the carina. Occasionally, it may be necessary to extend the tube using a length of tubing and a connector. Although endobronchial intubation of the right side is easier, there is inherent difficulty in preserving ventilation to the right upper lobe. Mainstem intubation is facilitated using a fiberoptic bronchoscope as a directing stylet. Blind left mainstem placement can be achieved with a 92% success rate by turning the head to the right after the tube has passed through the vocal cords and by then rotating the tube 180 degree so that the convex curve faces posteriorly before advancing it.73

The Univent tube is a single-lumen endotracheal tube that contains a bronchial blocker that passes through a small channel within the wall of an endotracheal tube. The bronchial blocker carries a low-pressure, high-volume cuff and has an internal lumen that can be used for suctioning the collapsed lung or for providing CPAP or high-frequency jet ventilation (Fig. 54-17).74 Initial tube placement in the trachea is accomplished as for any single-lumen tube, then it is rotated 90 degree toward the lung into which the blocker will be passed and advanced (Fig. 54-18). The blocker is then advanced into the targeted mainstem bronchus, after which the tracheal cuff is inflated and the tube is secured. The depth of the blocker is adjusted and confirmed using a flexible bronchoscope passed through the main lumen of the tube. Additional techniques to assist in placing the blocker include rotation of the head and placing the fiberoptic scope in the opposite lung to divert the blocker into the contralateral side. The tube offers the advantage of allowing easy conversion from single- to 2-lung ventilation (and vice versa), and it is suitable for long-term use in an intensive care unit (ICU) setting. The mobility of the blocker and large volume of its cuff increase the likelihood of proximal migration, with herniation of the cuff into the trachea.

Figure 54-17.

Close-up of the Univent tube shows 2 lumens. The small tube is retracted into the small lumen before intubation. [Modified from Kamaya H, Krishna PR. New endotracheal tube (Univent tube) for selective blockade of one lung. Anesthesiology. 1985;63:342.]

Figure 54-18.

The sequential steps of the fiberoptic-aided method of inserting and positioning the Univent bronchial blocker in the left mainstem bronchus are illustrated. One- and two-lung ventilation is achieved by simply inflating and deflating, respectively, the bronchial blocker balloon. FOB, fiberoptic bronchoscope. [From Benumof JL. Separation of two lungs (double-lumen and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]

Hypoxic Pulmonary Vasoconstriction

Humans encounter hypoxia throughout their lives. This occurs by destiny in utero, through disease, and by desire, in our quest for altitude. Hypoxic pulmonary vasoconstriction (HPV) is a widely conserved, homeostatic, vasomotor response of resistance of pulmonary arteries to alveolar hypoxia. HPV mediates ventilation-perfusion matching and, by reducing shunt fraction, optimizes systemic Po2.

Although total pulmonary blood flow is directly proportional to right ventricular cardiac output, its distribution within the pulmonary vasculature can be altered dynamically. Hypoxia, caused by either atelectasis or ventilation with a hypoxic gas mixture, diverts blood flow to better-ventilated, nonhypoxic lung segments. This phenomenon of HPV, first noted by Von Euler and Liljestrand in 1946, is of great importance to the anesthesiologist, particularly during thoracic anesthesia. In the absence of inhibiting factors, HPV can divert blood flow away from nonventilated regions.75 When a patient is in the lateral decubitus position, the dependent lung receives 60% of the cardiac output, whereas the nondependent lung receives 40%. If the nondependent lung is not ventilated and atelectatic, a maximal HPV response can reduce its blood supply by 50%. As a result, the dependent lung receives 80% of the cardiac output, and the atelectatic nondependent lung receives only 20% of the cardiac output (Fig. 54-19). Therefore, the arterial oxygen tension (Pao2) observed during regional lung hypoxia is much greater than would be expected if the HPV response were not present (Fig. 54-20).

Figure 54-19.

A. Schematic diagram showing that the 2-lung ventilation nondependent-to-dependent lung blood flow ratio is 40% to 60%. B. When 2-lung ventilation is converted to 1-lung ventilation (as indicated by atelectasis of the nondependent lung), the HPV response decreases the blood flow to the nondependent lung by 50%, so that the nondependent-to-dependent lung blood flow ratio is now 20% to 80%. [From Wernly JA, et al. Clinical value of quantitative ventilation-perfusion lung scans in the surgical management of bronchogenic carcinoma. J Thorac Cardiovasc Surg. 1980;80:535.]

Figure 54-20.

Effect of HPV on Pao2. As the percentage of lung that is hypoxic increases (x-axis), the arterial Po2 (Pao2) decreases (y-axis). When the amount of lung that is hypoxic 30% to 70%, which is in the 1-lung ventilation/anesthesia range, the decrease in Pao2 is much greater if there is no HPV compared with the normal expected amount of HPV. HPV, hypoxic pulmonary vasoconstriction. [From Benumof JL. One-lung ventilation and hypoxic pulmonary vasoconstriction: Implications for anesthetic management. Anesth Analg. 1985;64:821.]

Mechanisms

HPV is mediated by the smooth muscle cells throughout the lung. Although modulated by the endothelium, the core mechanism is in the smooth muscle cell. The Redox Theory for the mechanism of HPV proposes the coordinated action of a redox sensor (the proximal mitochondrial electron transport chain) that generates a diffusible mediator (a reactive O2 species) that regulates an effector protein (voltage-gated potassium [K(v)] and calcium channels). The subsequent inhibition of O2-sensitive K(v) channels, particularly K(v)1.5 and K(v)2.1, depolarizes pulmonary artery smooth muscle, activating voltage-gated Ca2+ channels and causing Ca2+ influx and vasoconstriction.76 A similar mechanism for regulating O2 uptake/distribution is partially recapitulated in simpler organisms and in the other specialized mammalian O2-sensitive tissues, including the carotid body and ductus arteriosus.77

Hemodynamic variables can influence the magnitude of HPV. The pulmonary vasoconstrictor response to hypoxia is decreased with increases in PA pressure, cardiac output, left atrial pressure, or central blood volume.78 Increases in pulmonary vascular pressures can mechanically open and recruit closed vessels in hypoxic lung regions, overcoming part of the active pulmonary vasoconstriction.79 An increase in cardiac output can mask the HPV response by recruiting pulmonary vessels or by increasing Pvo2. Alternatively, HPV may increase pulmonary vascular resistance and PA pressures as flow is diverted from a proportionately large section of hypoxic lung to a smaller section of normoxic lung.79 When flow is diverted from small hypoxic segments, the high compliance of the pulmonary circulation prevents clinically significant changes in pulmonary vascular resistance or PA pressure.

Drugs and anesthetics may modulate HPV and interfere with ventilation-perfusion matching. Calcium channel blockers and vasodilators, such as sodium nitroprusside, attenuate the HPV response (Table 54-6). These drugs increase the A-a gradient, often leading to hypoxemia perioperatively. Other perioperative conditions, such as hypocapnia and hypothermia, also decrease the normal HPV response.78,80

Table 54-6 Effect of Vasodilators on Hypoxic Pulmonary Vasoconstriction

Table 54-6 Effect of Vasodilators on Hypoxic Pulmonary Vasoconstriction

Drug

Effect

References

Hydralazine

No change

86

Nifedipine

Inhibited

86-89

Verapamil

Inhibited

90, 91

Nitroglycerin

Inhibited

93

Sodium nitroprusside

Inhibited

94

Nicardipine

No change

95

Labetalol

No change

96

Effects of Anesthetics

Extensive studies have been performed to examine the effect of inhalation and intravenous anesthetics on HPV. The results and implications of these studies differ according to the type of experimental preparation used. In human studies and in more physiologic in vivo investigations with an intact systemic circulation, inhalation anesthetics produced either no effect or only a mild decrease in HPV.81,82 In part, the discrepancy between the more complex in vivo studies and simpler in vitro models occurs because the additional factors that can modulate the HPV response, such as pulmonary vascular pressure, cardiac output, Pco2, and temperature, are absent. In the more biologically complex in vivo models, these factors seem to diminish the inhibitory effect of inhaled anesthetics on HPV.83,84

Intravenous agents such as ketamine and propofol do not dramatically affect HPV.83,85 HPV is also not directly affected by thoracic epidural analgesia. Any changes that have been observed during epidural may be attributable to alterations in cardiac function and loading conditions.86

Nitric Oxide

Nitric oxide (NO) is a unique endogenous compound that is found in endothelium and smooth muscle cells. NO induces vasodilation by activation of protein kinases and guanylate cyclase and reduction or resequestration of intracellular Ca+. There is a class of intravenous vasodilators, including nitroglycerine and nitroprusside, that produces muscle relaxation in a similar manner.

The most common clinical uses of NO are for the management of pulmonary hypertension and ventilation-perfusion mismatching. Intravenous therapy nonselectively produces pulmonary and systemic vasodilation. In contrast, NO administered as an inspired gas or NO donor Flolan (see Prostacyclin section) selectively dilates the vascular supply to those areas, thereby improving ventilation-to-perfusion matching. Nitric oxide has been used clinically in cases of primary pulmonary hypertension, lung transplantation, cardiac transplantation, cardiac disease, adult respiratory distress syndrome (ARDS), acute pulmonary hypertension, congenital heart disease, and idiopathic pulmonary hypertension. Its clinical potential has been hampered by the complexity and cost of the gas and its delivery system.

Delivery systems require an adequate scavenging system to reduce the risk of occupational exposure and continuous gas concentration monitoring. The potential toxicity of NO focuses on its conversion from the free radical form to NO2, which is associated with lung toxicity, and the formation of nitrosylhemoglobin, which is rapidly converted to methemoglobin.87-90 Clinical reports of NO-associated toxicity include methemoglobin toxicity, paradoxical deterioration in oxygenation related to edema or worsening of right-to-left shunting,74,91-95 and rebound pulmonary hypertension.87,96,97 Because of these latter responses, the dose of NO should be gradually decreased to avoid deterioration in oxygenation or rebound pulmonary hypertension.

Prostacyclin

Prostacyclin (PGI2, Epoprostanol, Flolan) is a member of the prostaglandin family of lipid mediators derived from arachadonic acid and is synthesized predominantly by endothelial cells, including the pulmonary vascular endothelium.98 PGI2 produces vasodilation in low-resistance vascular beds such as the pulmonary circulation.99 Not only has PGI2 been shown to stimulate endothelial release of NO,100 but NO has been shown in turn to enhance the production of PGI2 in human pulmonary artery smooth muscle cells. It has a good safety profile; PGI2 is spontaneously hydrolyzed in plasma to its inactive metabolite, 6-keto-prostaglandin-F. The in vitro half-life of prostacyclin in human blood at 37°C and pH of 7.4 is approximately 6 minutes.101 Animal studies demonstrate that intravenous PGI2 has a high clearance (93 mL · min−1 · kg−1), small volume of distribution (357 mL/kg), and a short half-life (2.7 min).101

Prostacyclin, which can be delivered as an aerosol, has replaced NO as the preferred inhaled selective pulmonary vasodilator due to lower cost and absence of toxic metabolites.98,102,103 It has minimal effects on systemic arterial pressure and dramatic improvements in arterial oxygenation and lowering pulmonary arterial pressures.102,103 Its use during 1-lung anesthesia can improve V/Q matching, but it is not nearly as effective as CPAP to the nonventilated (nondependant, operative) lung (see the following section) deterioration in oxygenation or worsening of pulmonary hypertension.

Strategies to Improve Oxygenation during 1-Lung Ventilation

The occurrence of arterial hypoxemia during 1-lung ventilation (OLV) is difficult to predict clinically. Previous studies have attempted to identify predictive preoperative and intraoperative factors of Pao2 during single-lung ventilation. Some variables (relative perfusion to the operative lung, intraoperative Pao2 during 2-lung ventilation) were strongly identified as predictors of low Pao2 during 1-lung ventilation, whereas others (side of operation, preoperative pulmonary function tests) have been controversial.104,105 Interestingly, patients with a hematocrit value of greater than 45% are reported to have lower Pao2 values during 1-lung ventilation.106 The occurrence of hypoxia mainly depends on factors such as residual shunt to the nonventilated lung, cardiac output, and degree of pulmonary vasoconstriction. There are, however, strategies to decrease the occurrence of hypoxemia during 1-lung ventilation and manage it when present.

The basic principles for management of 1-lung ventilation include (1) delay initiation until after turning the patient to the lateral decubitus position, while still allowing sufficient time for the nondependent lung collapse, (2) confirm correct positioning of the double-lumen tube by fiberoptic bronchoscopy, (3) use high-inspired O2 concentrations to decrease the risk of systemic hypoxemia, (4) using a large tidal volume while controlling peak inspiratory pressure to less than 30 mm Hg and adjusting respiratory rate to keep Paco2 at approximately 35 mm Hg, (5) continuously monitor oxygenation using pulse oximetry, and (6) continuously monitor ventilation by noting changes in end-tidal CO2 concentrations and peak inspiratory pressures.

Measures to improve oxygenation during 1-lung ventilation include 1 or more of the following strategies: (1) improve the V/Q distribution in the dependent lung (ie, lung recruitment maneuver, PEEP to the dependent lung), (2) increase Pao2 in the nondependent lung (ie, CPAP), (3) decrease blood flow to the nondependent lung (ie, placement of a ligature on the pulmonary artery), and (4) increase blood flow and perfusion to the dependent lung (ie, prostacyclin or nitric oxide).

Prevention of Absorption Atelectasis

Absorption atelectasis, caused by increased Fio2, can be decreased or prevented by ventilation using large tidal volumes, application of PEEP to the dependent lung, and ventilation with an Fio2 less than 100%.84 The use of 10% to 20% nitrogen with 80% to 90% O2 has been suggested to decrease the possibility of absorption atelectasis, because nitrogen splits open the alveoli in areas of low V/Q ratio. The small reduction in the Fio2 causes only a small decrease in Pao2. Nitrogen is more efficacious than N2O in splitting the alveoli because it is less soluble.

Verification of Lung Isolation

The most important factor in assuring adequate oxygenation and ventilation is the proper positioning of the double-lumen endotracheal tube or bronchial blocker. Tube position should be reconfirmed after turning the patient. In addition, secretions that could interfere with ventilation and increase inflation pressure also should be suctioned from the airway.

Recruitment Maneuver

Progressive atelectasis associated with decreasing Pao2 is a common problem of the patient undergoing single-lung ventilation during thoracic surgery. These patients are at increased risk of atelectasis due to single-lung ventilation, lateral decubitus positioning, inhibition of HPV, and periodic disconnection from the ventilator. Recruitment maneuvers are used to reinflate collapsed alveoli, which results in improved oxygenation and ventilation. A sustained pressure of about 35 to 40 cm H2O, which would be above the tidal ventilation range, is applied for a period of 30 to 60 seconds in order to inflate lung units. After this maneuver, it should not be necessary to increase the tidal volume or PEEP, as the subsequent lung volumes should be greater. A successful procedure will result in improved oxygenation, reduced end-tidal CO2, and improved compliance. Profound hypotension can occur due to inhibition of right heart filling.

Ventilation Using Large Tidal Volumes

Small tidal volume ventilation to the dependent lung can decrease FRC and promote airway closure and atelectasis. The development of a hypoxic area in the dependent lung interferes with the overall effectiveness of HPV in the nondependent lung, to optimize oxygenation of the dependent lung. The tidal volume at initiation of 1-lung ventilation should be about 6 to 8 mL/kg. The tidal volume is then adjusted upward or downward according to the airway pressures and arterial blood gas values. Delivering an excessively large tidal volume to the dependent lung can paradoxically worsen oxygenation and ventilation of the dependent lung. Increased airway pressures with the associated the risks of pneumothorax or barotrauma and increased PVR can divert blood, that is, perfusion, to the nonventilated nondependent lung.107-110 Increased airway pressures have been associated with postoperative inflammatory lung disease such as postlobectomy and postpneumonectomy pulmonary edema.111,112

Maintenance of Normocapnia

Respiratory rates should be adjusted to maintain normocapnia. Because the tidal volume is decreased with initiation of 1-lung ventilation, the respiratory rate should be increased to maintain the same minute ventilation and Paco2. The change from 2-lung ventilation to 1-lung ventilation usually causes no problem with CO2 elimination because of the high diffusibility of CO2 across the alveolar membrane.110,113,114 Theoretically, hypocapnia should be avoided because it can directly dilate the pulmonary vessels, interfering with HPV in the nondependent lung. Alternatively, hypercapnia will increase PVR and can increase right heart strain.

Dependent-Lung PEEP

Because the dependent lung often has a decreased volume during 1-lung ventilation, several attempts have been made to improve oxygenation by managing the ventilated lung with PEEP. The application of PEEP to the dependent lung maintains recently recruited atelectatic alveoli to increase FRC and lung compliance. The disadvantage of applying PEEP to the dependent lung is that the associated increased mean airway pressure and PVR could divert some blood flow to the nondependent, atelectatic, nonventilated lung. Therefore, the effect of using PEEP is a balance between its potential beneficial effects and the possible deleterious effects of decreasing HPV, causing the redistribution of blood flow to the nondependent nonventilated lung. In a patient with a very diseased dependent lung, the positive effect of selective dependent-lung PEEP may outweigh its negative effects. In contrast, patients who have a relatively normal dependent lung may have decreased oxygenation if PEEP is selectively applied to that lung (Fig. 54-21).

Figure 54-21.

Selective positive end-expiratory pressure (PEEP) to the ventilated-dependent lung can increase dependent-lung ventilation-to-perfusion ratios (−A/). Dependent-lung PEEP also can cause compression of the small intra-alveolar vessels in the dependent lung, causing blood flow diversion to the nonventilated, nondependent lung, thereby increasing the shunt through the nonventilated, nondependent lung. Therefore, the overall arterial oxygenation effect of dependent-lung PEEP will be a trade-off between the good effect of an increase in dependent-lung A/ and the bad effect of increased nonventilated-lung blood flow. [From Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia: WB Saunders; 1987.]

Selective Nondependent-Lung CPAP

The application of CPAP to the nonventilated nondependent lung improves oxygenation during 1-lung ventilation (Fig. 54-22). Even with a maximal HPV response, 20% of the cardiac output still flows through the nondependent lung. The use of an inhalation agent, such as isoflurane, may increase the nondependent lung blood flow to 24% of the cardiac output. Application of CPAP during 1-lung ventilation leads to the oxygenation of blood that perfuses the nondependent lung and thereby dramatically increases Pao2. CPAP is initiated during the deflation phase of a large tidal volume breath to maintain uniform expansion and avoid the need to overcome critical opening pressures of collapsed alveoli. The application of 5 to 10 cm H2O CPAP may not interfere with surgical exposure during open thoracotomies, but will significantly impede visualization during thoracoscopy. In addition, CPAP at less than 10 cm H2O does not compress small intra-alveolar vessels nor produce significant hemodynamic effects, but 15 cm H2O of CPAP decreases blood flow through the nondependent lung, diverting flow to the dependent lung.115

Figure 54-22.

Selective continuous positive airway pressure (CPAP) to the nonventilated, nondependent lung (static distension without tidal movement) allows this lung to participate in oxygen uptake and markedly decreases the shunt through the nonventilated, nondependent lung. Even if the nonventilated, non-dependent lung CPAP causes blood flow diversion to the ventilated, dependent lung, the diverted flow can still participate in oxygen uptake and CO2 elimination in the ventilated, dependent lung. Usually 5 to 10 cm H2O of nondependent lung CPAP is all that is clinically needed, and this amount of CPAP does not cause any serious surgical interference. [From Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]

During 1-lung ventilation, the nondependent lung does not remain totally unventilated. Each time the dependent lung is inflated, the mediastinum is displaced upward into the nondependent thorax. During the exhalation phase, the mediastinum falls away from the nondependent side. The effect of the mediastinal movement created by ventilation produces asynchronous, "pendelluft" ventilation of the nondependent lung. This phenomenon may be observed as a small puff of air emanating from the lumen of the nondependent endotracheal tube, which may be misinterpreted as a failed seal of the bronchial cuff. Because the nondependent lung is ordinarily open to the atmosphere, the pendelluft ventilation introduces room air into the tracheobronchial tree. Thus, even in the absence of CPAP, delivering 100% oxygen via T-piece may improve oxygenation of blood flowing through the nondependent lung.

The conventional method for instituting CPAP during 1-lung ventilation uses an O2 source and a manometer or PEEP valve (Fig. 54-23).116 Alternatively, delivery of oxygen at high flows via a catheter placed in the mainstem bronchus of the nondependent lung produces CPAP without need for a PEEP valve. In most situations, an O2 flow rate of 5 to 10 L/min, which creates CPAP of 5 to 10 cm H2O, is sufficient for improving oxygenation. One advantage of this system is that the elimination of CO2 is proportional to the flow rate of the gas in the CPAP system. A very high O2 flow rate delivered at or below the carina may improve gas exchange without any tidal exchange, which is known as "continuous high-flow apneic ventilation."

Figure 54-23.

A. and B. Schematic diagram showing 2 nondependent lung continuous positive airway pressure (CPAP) systems without reservoir bags. Both contain an oxygen source and a pressure relief valve, but A has a pressure manometer to measure the CPAP, whereas B does not. [From Benumof JL. Conventional and differential lung management of one-lung ventilation. In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]

Strategies to Improve Oxygenation during Single-Lung Ventilation

The strategies to maintain oxygenation are individualized to account for patient factors and surgical considerations. Although the application of CPAP during video thoracoscopy is contraindicated, its use for an open thoracotomy is better tolerated. The first step to improve arterial oxygenation is to confirm proper double-lumen tube placement. If oxygenation is still inadequate, the strategies of applying CPAP to the dependent lung and PEEP to the dependent lung can be sequentially and additively applied. If arterial oxygenation remains poor, the patient's hemodynamic status should be assessed. A decrease in cardiac output, leading to a decrease in mixed venous oxygen saturation (Svo2), can magnify the effect of shunt on arterial oxygenation.

If hypoxemia still persists after differential CPAP/PEEP, the nondependent lung may be intermittently ventilated with positive pressure and 100% O2. Intermittent reinflation of the collapsed lung with O2 is beneficial but its beneficial value was found to decline with repeated inflations.117 Finally, most of the V/Q mismatch and arterial hypoxemia can be eliminated by decreasing blood flow to the nondependent lung by temporarily ligating its pulmonary artery (Fig. 54-24). Caution should be taken as this further increases right ventricular afterload and may cause acute cardiac decompensation.

Figure 54-24.

Algorithm for managing 1-lung ventilation and improving oxygenation.

Selective Nondependent-Lung High-Frequency Ventilation

Any method that results in splitting the alveoli and air spaces of the nondependent lung will lead to an improvement in arterial oxygenation and a decrease in the transpulmonary shunt. High-frequency ventilation of the nondependent lung has been studied in combination with conventional positive-pressure ventilation of the dependent lung. Using this combination, Pao2 was much better than with intermittent positive-pressure ventilation of the dependent lung with total collapse of the nondependent lung.118 In most patients, the same increase in arterial oxygenation can be achieved using selective nondependent lung CPAP, which requires much simpler equipment compared with high-frequency ventilation apparatus. In some situations, high-frequency ventilation may be more advantageous:

If the nondependent lung has a major bronchopleural fistula, high-frequency ventilation to the nondependent lung using low airway pressures helps to decrease the air leak and improve oxygenation and ventilation.119

During operation on the major conducting airways, high-frequency ventilation permits the use of small ventilation catheters that pass through the operating field.119-122

Unilateral high-frequency jet ventilation with contralateral intermittent positive-pressure ventilation has been used in the anesthetic treatment of patients with severely compromised respiratory reserve. The technique provided satisfactory anesthesia, good operating conditions, and adequate gas exchange.123

Anesthetic Techniques

Although thoracic surgery can be performed solely using a regional block, most thoracotomies are performed during general anesthesia with controlled ventilation. Epidural or other regional anesthetic techniques often are used to decrease the intraoperative anesthetic requirement to facilitate emergence and extubation and for postoperative pain control.124 Recent evidence suggests that the use of epidural or paravertebral anesthesia for perioperative analgesia improves short-term outcomes up to several months.125

General Anesthesia

The choice of induction agent and dosage is influenced by the patient's medical condition. In patients in whom extensive airway instrumentation or manipulation precedes thoracotomy, an antisialogogue, glycopyrrolate, can reduce secretions. Opioids supplement the inhalational anesthetic, although the dosage of any narcotic should be reduced in patients who will receive epidural opioids. The incidence of postoperative respiratory depression is related to the total dosage of narcotics administered systematically and epidurally. After the induction of general anesthesia, controlled manual ventilation with mask is started using an inhalation anesthetic. N2O is only occasionally used during the induction phase and during prepping, draping, and positioning of the patient. Because large intrapulmonary shunts are anticipated with initiation of 1-lung ventilation, it is prudent to increase the inspired concentration of oxygen. N2O should be avoided in patients who have marginal preoperative oxygenation or in those with large bullae and emphysematous lungs to avoid expansion of bullae by N2O.

After the induction of anesthesia, the trachea is intubated with a single-lumen or double-lumen tube as indicated by the surgical procedure. Position of the endotracheal tube is confirmed by careful auscultation, capnography, and, if indicated, by fiberoptic bronchoscopy.

Volatile, halogenated anesthetic drugs have several desirable properties for use during thoracic procedures. They decrease airway irritability and obtund airway reflexes in patients who usually have reactive airways, and they maintain adequate anesthesia while allowing increased inspired oxygen concentrations. They can be eliminated rapidly, allowing tracheal extubation in the operating room with less concern for postoperative respiratory depression. Although volatile anesthetics allow high inspired O2 concentrations, at minimum alveolar concentration (MAC) values greater than 1 they may reduce Pao2 by increasing the shunt related to partial inhibition of HPV.81,82,126 The inhibition of HPV by inhaled anesthetics may exhibit substantial variability.

Patients with mediastinal and airway tumors may be at risk for airway obstruction during induction of anesthesia. In such patients, the anesthetic plan and emergency treatment strategies should be discussed with the surgeon preoperatively. If emergent tracheostomy, rigid bronchoscopy, or extracorpeal oxygenation are anticipated, the entire operating team should be prepared to act smoothly and efficiently. Patients at increased risk of airway obstruction may require awake fiberoptic intubation or spontaneous ventilation to avoid airway obstruction. Special management concerns for mediastinal tumors are discussed later.

Regional Anesthesia

Epidural anesthesia, paravertebral block, intercostal nerve blocks, or field blocks have been occasionally used as the sole anesthetic for various thoracic procedures, including thoracotomy. Thoracic epidural blockade in awake, sedated patients has been used successfully for open thoracotomies or thoracoscopies.127,128 Crawford et al described 677 patients with tuberculosis in whom epidural anesthesia was used for thoracotomy.129 Others successfully used this technique. The most surprising results were the absence of paradoxical respiration and dyspnea. The breathing pattern and speech appeared normal even when an upper lobe bronchus was transsected and held open. Several factors may have contributed to the success of this unorthodox technique: (1) the patients were extremely cooperative and had a good rapport with the anesthesiologist; (2) analgesia was complete, and patients were comfortable; (3) the use of premedication and sedation avoided the pitfalls of oversedation and excitability; (4) supplemental O2 was administered by positive pressure mask if the patient reported any shortness of breath; and (5) operation was remarkably gentle and swift. It is doubtful that all of the above conditions could be fulfilled during an anatomic resection in the routine patient by the average surgeon.

Combined Epidural Blockade and General Anesthesia

It is unlikely that the routine patient would tolerate the sole use of regional anesthesia, especially during an open thoracotomy. The techniques of general and epidural anesthesia often are combined to achieve the benefits of each. The relative contribution of each technique to a combined anesthetic can vary. The epidural blockade may either be used for postoperative analgesia or as the major anesthetic, with light general anesthesia used for amnesia and sedation. Epidural anesthesia has the advantages of reduction in afterload,130 improved pulmonary function, decreased incidence of venous thromboembolism,131,132 and suppression of the stress response.81,133 Potential disadvantages include the time required to establish the block, increased fluid requirements and relative decrease in blood pressure associated with sympathectomy, and the potential for technical complications such as epidural hematoma. A prospective, randomized, controlled clinical study examined the effect of epidural anesthesia and postoperative analgesia on postoperative morbidity rate in high-risk surgical patients.134 When compared with control patients, those who received epidural anesthesia and analgesia had fewer overall complications and fewer cardiovascular or major infectious complications, lower urinary cortisol secretion (a marker of the stress response), and lower hospital costs.134

Vital capacity and lung compliance decrease after general anesthesia and neuromuscular blockade in patients undergoing thoracotomy. Epidural analgesia with light general anesthesia results in less decrease in static compliance and fewer alterations in postoperative pulmonary function.135 The perioperative use of epidural anesthesia is also associated with fewer major postoperative infections. This may result from (1) decreased duration of endotracheal intubation and mechanical ventilation, which diminishes many of the defense mechanisms against infection136,137; (2) decreased duration of ICU stay postoperatively and reduced risks of nosocomial infection; and (3) suppression of the endocrine stress response to operation, which has an inhibitory effect on the immune system.138 Immune competence is less disturbed postoperatively when epidural anesthesia is used compared with other anesthetic and analgesic techniques.139,140

Patients who received epidural anesthesia had fewer cardiovascular complications, including congestive heart failure.134 A comparison of epidural analgesia with general anesthesia noted a decrease in the size of myocardial infarctions, probably related to improved regional subendocardial perfusion.130 Possible mechanisms include afferent sensory blockade, decreased adrenergic tone, and coronary and systemic vasodilation with a reduction in cardiac preload and afterload.141-143

An epidural catheter can be inserted in the midthoracic (T4-T9) or low thoracic-lumbar (T9-L2) regions. To date, no studies have demonstrated overwhelming superiority of 1 approach. In the experience of the authors, the midthoracic level, about T7, provides excellent conditions for thoracic and thoracoabdominal procedures. The low thoracic region is suitable for thoracoabdominal procedures, such as gastrectomy. Use of a lumbar epidural blockade in patients undergoing thoracic surgery requires a greater dosage of local anesthetics or narcotics to provide analgesia in the thoracic regions and is not routinely recommended. Because of the multiple advantages conferred by thoracic epidural analgesia, the anesthetic plan for open thoracotomy should always include placement of a thoracic epidural catheter unless an absolute contraindication is present.

Paravertebral block with the placement of a catheter for continuous analgesia has been found to provide pain control as good as epidural analgesia with less hypotension and nausea.144-147 These catheters can be placed with the aid of ultrasound. They are usually dosed with local anesthetic only as opioid does not improve analgesia. They may be safer to place in patients continued on platelet inhibiting drugs (Plavex) as hematoma formation will not directly impinge on the spinal cord. An alternative is to have the surgeon place these catheters from within the chest and externalize the catheter.

Thoracoscopy versus Thoracotomy

Evolution of surgical technique and technical advances in electronics and instrumentation have led to renewed interest in thoracoscopy. In a health care environment that values cost and patient outcome, video-assisted thoracoscopy (VAT) has advantages beyond open thoracotomy, including decreased postoperative pain, pulmonary impairment, and hospital stay. Thoracoscopy permits the visualization of the pulmonary cavity through several small portals. These portals provide access for the video camera and allow manipulation of thoracic structures and use of surgical instruments such as staplers, dissectors, coagulators, and lasers. Although initially used for only minor surgical procedures, the application of VATs has expanded considerably for both diagnostic and therapeutic procedures (Box 54-6). If access is inadequate or if bleeding complications occur, VATs are easily converted to a limited open thoracotomy.

Box 54-6

Box 54-6

Applications of Video-Assisted Thoracoscopy

Pulmonary

Lung biopsy
Resection mass
Bleb resection
Volume reduction pneumoplasty

Pleura

Diagnostic evaluation
Pleurodesis
Decortication

Pericardium

Pericardial drainage
Pericardectomy

Cardiac

Automatic implantable cardiovertor/defibrillator placement
Cryoablation, radiofrequency ablation for treatment of atrial fibrillation
Cardiac pacemaker placement

Mediastinum

Lymph node biopsy
Biopsy and resection of mediastinal mass
Vagotomy

Esophageal surgery

Thoracic duct ligation

Miscellaneous

Sympathectomy
Microdiscectomy

Anesthetic treatment for patients undergoing thoracoscopy is similar to that for open thoracotomy (Table 54-7). Although limited thoracoscopy has been performed in spontaneously breathing, sedated patients, this procedure usually is performed during general anesthesia with placement of a double-lumen endotracheal tube for lung separation. Good lung isolation is even more critical than in an open procedure because the surgeon cannot "pack the lung away." Many patients have obstructive lung disease that impedes passive deflation of the nonventilated lung. To foster deflation, the nondependent lung should be carefully suctioned of secretions that may cause air trapping, then denitrogenated by ventilating with 100% oxygen, with single-lung ventilation initiated before skin incision. The tidal volume delivered to the ventilated dependent lung should be decreased to prevent upward shift of the mediastinum during single-lung ventilation. If deflation is inadequate, CO2 can be insufflated into the nondependent thoracic cavity. Hypercarbia and hypotension may develop if excessive gas inflation causes mediastinal shift and reduction in venous return to the heart. The use of VAT over open thoracotomy has several advantages. Analgesic requirements and length of hospital stay are less than those for open thoracotomy.148-152 Adequate postoperative analgesia can be obtained with a combination of parenteral opiates, nonsteroidal anti-inflammatory drugs (NSAIDs), or paravertebral, epidural, or intercostal nerve blocks. We will typically place an epidural or paravertebral catheter for patients with respiratory compromise to facilitate postoperative pulmonary toilet.

Table 54-7 Anesthetic Guidelines for Video-Assisted Thoracoscopic Surgery and Thoracotomy

Table 54-7 Anesthetic Guidelines for Video-Assisted Thoracoscopic Surgery and Thoracotomy

Video-Assisted Thoracoscopic Surgery

Thoracotomy

Indication

Diagnostic, therapeutic (see Box 54-6)

Samea

Monitors

Standard monitors

Optional (arterial, pulmonary artery catheter, Foley catheter)

Samea

Anesthesia

General anesthesia

Optional (combined regional/general anesthesia)

Samea

Additional equipment

Fiberoptic bronchoscope

Arm board

Pillows

Bean bag or chest roll

Samea

Ventilation

Double-lumen endotracheal tube

Bronchial blockers

Position

Later decubitus position (check and pad pressure points)

Samea

Incision

Several portals for the introduction of equipment

Lateral thoracotomy

Anterior thoracotomy

Posterior thoracotomy

Muscle-sparing incision

Unique considerations

Single-lung ventilation

Samea

Intraoperative complications

Hypoxia

Hypercapnia

Bleeding

Samea

Estimated blood loss

<300 mL

Variable

Postoperative analgesia

Parenteral opiates

Nonsteroidal anti-inflammatory drugs

Intrapleural catheter, intercostal nerve block

Epidural > parenteral opiates

NSAIDs

Postoperative morbidity

Hypoxia (atelectasis, pneumothorax, pleural effusion)

Bleeding

Samea

Postoperative case

Adequate analgesia

Supplemental O2

Chest radiography

May require close follow-up evaluation overnight

Samea

aSame as video-assisted thoracoscopic surgery.

Anesthesia for Patients Undergoing Bronchoscopy

Background

Although introduced in the 1890s, it remained for Chevalier Jackson to perfect the therapeutic application of rigid bronchoscopy for retrieval of foreign bodies and diagnostic use in patients with neoplastic and inflammatory disease. The rigid bronchoscope is a hollow, metal tube with a blunted and beveled distal tip that allows insertion into the airway with minimal trauma. The proximal end is adapted for observation of the airway, maintenance of gas exchange, and introduction of surgical instruments. The proximal side arm is adapted for administration of oxygen or other gases, and also enables mechanical ventilation during bronchoscopy. Within the wall of the bronchoscope, there is a series of channels for the illumination of the distal field and for suctioning secretions and blood. The large size of the rigid bronchoscope permits insertion of sponges, snares, knives, scissors, electrodes, and other special devices. The most common uses of a rigid bronchoscope are for retrieval of large foreign bodies, evaluation and debulking of bronchial tumors, access to bleeding sites, and overall evaluation of the airways.

The introduction of the fiberoptic bronchoscope has had a dramatic impact by supplanting the use of the rigid instrument in many patients. The flexible fiberoptic bronchoscope initially contained clusters of glass fibers that illuminate the airway and transmit the visual image. Now they have an LED for light source and a photosensitive chip for image capture. Several hollow ports or channels are incorporated for suctioning, the instillation of medications or lavage fluid, and the introduction of accessory instruments. Flexion of the distal tip by cables allows the instrument to be directed to all segments of the tracheobronchial tree. Indications for fiberoptic bronchoscopy are listed in Box 54-7. Bronchoscopy often is only the first of several diagnostic or therapeutic procedures. After bronchoscopy, mediastinoscopy or thoracoscopy may be performed to further evaluate the presence of disease or for its management.

Box 54-7

Box 54-7

Indications for Fiberoptic Bronchoscopy

Diagnostic indications

Staging and characterization of pulmonary disease
Evaluation of the site and etiology of pulmonary symptoms

Therapeutic indications

Tracheal intubation
Positioning of the double-lumen endotracheal tube
Removal of secretions and bronchial toilet
Laser of tumors

Flexible Fiberoptic Bronchoscopy

Anesthetic Management

Flexible fiberoptic bronchoscopy can be performed during local anesthesia in sedated, spontaneously breathing patients or during general anesthesia with or without placement of an endotracheal tube (Table 54-8).

Table 54-8 Anesthetic Guidelines for Fiberoptic Bronchoscopy and Rigid Bronchoscopy

Table 54-8 Anesthetic Guidelines for Fiberoptic Bronchoscopy and Rigid Bronchoscopy

Fiberoptic Bronchoscopy

Rigid Bronchoscopy

Indications

Diagnostic, biopsy, lavage, confirm placement of endotracheal tube

Therapeutic, laser, retrieval or foreign body, pulmonary toilet

Monitors

Standard monitors

Samea

Anesthesia

General anesthesia, sedation with block

General anesthesia

Additional equipment

Shoulder roll

Airway

Awake spontaneous ventilation, single-lumen endotracheal tube (≥8 mm)

Apneic ventilation

Intermittent positive pressure ventilation

Jet ventilation

Position

Semirecumbent (awake patients)

Cervical extension

Unique considerations

Local and nerve block, antisialagogue

Lidocaine intravenously or intratracheal, muscle relaxation, antisialagogue

Intraoperative complications

Bronchospasm

Bleeding

Pneumomediastinum

Pneumothorax

Subcutaneous emphysema

Barotrauma

Hypoxia

Hypercapnia

Vasovagal (bradycardia)

Arrhythmias

Fever (bacteremia)

Samea

Dental trauma

Analgesia

Minimal pain (parental opiates)

Postoperative morbidity

Atelectasis

Bleeding and hemoptysis

Bronchospasm

Fever

Samea

Postoperative care

Chest radiography

Humidified O2

No eating or drinking until protective airway reflexes have returned

Samea

aSame as fiberoptic bronchoscopy.

Awake fiberoptic bronchoscopy is performed after administration of sedation, an antisialagogue, and adequate topical local anesthesia. If the correct balance of these components is not achieved, serious trauma can result from coughing and movement of the uncomfortable patient. Techniques of anesthetizing the airway include

Topical application of local anesthetic to the nose, mouth, or oral pharynx
Internal or percutaneous block of the superior laryngeal nerve
Glossopharyngeal nerve block
Recurrent laryngeal nerve block either by spraying of the tracheal bronchial mucosa from inside with local anesthetic or percutaneous transcricothyroid membrane injection
Inhalation of nebulized local anesthetic to the mucous membrane of the mouth, pharynx, larynx, trachea, and bronchi

The use of sedation and an antisialagogue improves bronchoscopic conditions. An anticholinergic, such as glycopyrrolate, is preferred because of the lack of central nervous system (CNS) side effects. A benzodiazepine is useful for anxiolysis and increasing the threshold for CNS toxicity to local anesthetics. Intravenous infusions of dexmedetomidine, remifentanyl, or propofol have also been successfully used to provide an adequate level of sedation. Sedation should be used with caution, especially in elderly debilitated patients or in those with serious underlying respiratory compromise. Cardiac and respiratory function should be monitored during the procedure by a person who is not responsible for the endoscopy. Because capnography often is unreliable during bronchoscopy, pulse oximetry is the most important monitor to assess the adequacy of oxygenation. After the procedure, the patient should be placed in a monitored environment initially to evaluate for complications from the procedure or the sedation.

Ventilation Management

When performed during general anesthesia, fiberoptic bronchoscopy usually is accomplished through an endotracheal tube. The resulting marked reduction in the effective functional internal diameter of the endotracheal tube available for ventilation is associated with increased airway resistance and can result in distal air trapping. To reduce complications, the anesthesiologist should avoid spontaneous ventilation, eliminate PEEP from the circuit, ventilate with a prolonged expiratory phase (inspiratory/expiratory [I/E] ratio of 1:3), and use the largest endotracheal tube possible. Suppression of airway reflexes to prevent laryngospasm and bronchospasm can be accomplished by the use of inhaled anesthetic agents and by the administration of lidocaine. A helium-O2 mixture will decrease airway resistance, but is usually not necessary.

Rigid Bronchoscopy

Anesthetic Management

Maintenance of anesthesia can be achieved with mixtures of intravenous sedatives and narcotics or in combination with potent inhalational anesthetics. Use of inhaled anesthetics has the obvious disadvantage of exposing personnel to the escaping anesthetic vapors. In the authors' experience, an infusion of remifentanyl and propofol provides very acceptable anesthetic conditions characterized by a quick emergence and negligible residual sedation. Topical anesthesia with lidocaine can be used to suppress cough reflexes and prevent bronchospasm. Patients undergoing rigid bronchoscopy should be paralyzed to prevent sudden movement or cough, which can result in major morbidity.

Ventilation Management

Intermittent positive pressure ventilation can be delivered during rigid bronchoscopy by connecting the standard anesthesia circuit to the ventilating side-port of the rigid bronchoscope (Fig. 54-25). This ventilating technique requires no special equipment, allows for accurate measurement of the Fio2 and inhaled anesthetic concentration, and provides adequate oxygenation in most patients. The ventilating gases may leak through the space between the bronchoscope and the tracheal wall. To compensate for the leak, gas flows should be increased, and the posterior pharynx and larynx can be packed with gauze. Because ventilation is only possible when the eyepiece is in place, the cumulative effect of multiple periods of apnea may result in hypercapnia and cardiac dysrhythmias.

Figure 54-25.

Schematic diagram showing a rigid ventilating bronchoscope system, which consists of the anesthesia circle system attached to a flexible connector that is attached to the sidearm of the bronchoscope. With the proximal eyepiece in place, most of the inspired gas goes into the patient. Because the bronchoscope cannot fully fill the area of the trachea, there is a variable leak around the distal end of the bronchoscope. Exhaled gases are through the anesthesia circle system. When the eyepiece is removed, there is a very large leak out the proximal end of the bronchoscope. [Modified from Benumof JL. Anesthesia for special elective diagnostic procedures. In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]

Jet Ventilation

The use of jet ventilation has been advocated for prolonged rigid bronchoscopy. The Venturi (jet) ventilation technique allows the surgeon an unhurried, undisturbed period of viewing without need for an eyepiece. A potential disadvantage is that jet ventilation can result in spillage of blood and other debris into the tracheobronchial tree.

An intermittent high-velocity jet of oxygen entrains air into the bronchoscope, resulting in expansion of the lungs. If the lungs are noncompliant or if the bronchoscope is small in relation to the trachea, large amounts of the tidal volume will escape between the bronchoscope and tracheal wall, resulting in poor alveolar ventilation. Careful observation of the patient's chest movement is necessary to ensure adequate tidal volumes. The adequacy of ventilation, a function of total thoracic compliance, can be monitored by obtaining an arterial blood sample, by transcutaneous CO2 monitoring, or by intermittent capnography. It is difficult to know the inspired concentration of oxygen because of the variable entrainment of room air, but the adequacy of oxygenation can be monitored by pulse oximetry or arterial blood gas sampling.

The intraluminal pressure is a function of the driving pressure from the in-line reducing valve, size and length of the needle jet, and design of the bronchoscope. In addition, a decrease in the effective intraluminal diameter by the introduction of suction catheters or biopsy forceps can prevent the escape of gas introduced by the jet and results in a dramatic increase in intratracheal pressure. If the instruments are tight fitting, the driving pressure should be decreased to prevent barotrauma.

The apparatus described by Sanders used a high-pressure oxygen source of 50 psi, which was delivered through a 16- or 18-gauge needle located within the rigid bronchoscope (Fig. 54-26). The original jet ventilation system has been improved by connecting the side arm to the anesthesia circuit, thereby entraining an oxygen anesthetic gas mixture. Increasing the size of the jet port (the Carden side arm) results in increased inflation pressure and increased Fio2 at the distal tip of the bronchoscope.153 Jet ventilation at low frequencies can provide for adequate oxygenation and ventilation. Commercial high-frequency jet ventilators (HFJV) have been used with the rigid bronchoscope. Rates of 150 to 300 breaths/min result in ventilation and oxygenation comparable with intermittent low-frequency jet ventilation,154 but rates greater than 300 breaths/min result in a decrease in oxygenation and an increase in Paco2. The major advantage of HFJV over low-frequency jet ventilation is that there is less movement of the tracheobronchial tree, providing better surgical conditions for such procedures as laser therapy.

Figure 54-26.

Components needed for jet ventilation through the bronchoscope (Sanders injector). Wall connector for oxygen supply, reducing valve and pressure gauge, high-pressure tubing, toggle switch, needle injector jet.

Apneic Oxygenation

In the absence of ventilation, adequate oxygenation can be maintained for a prolonged period at the expense of increasing Paco2. Initially, the patient is hyperventilated with 100% inspired oxygen until relative hypocapnia and complete denitrogenation is achieved. A period of hyperventilation, to a Paco2 of approximately 30 mm Hg, will increase the period of apnea that can be tolerated before respiratory acidosis ensues. A small catheter is placed above the carina and insufflated with O2 at 10 to 15 L/min. The adequacy of oxygen reserve and generation of CO2 are functions of pulmonary mechanics and body size.

Complications

Aside from the inherent risks of local and general anesthetics, bronchoscopy of the airway may be associated with perioperative morbidity. Patients may exhibit decreases in FEV1, FVC, peak expiratory flow rate, and peak inspiratory flow rate. Additional factors that may contribute to decreased lung function or bronchospasm include airway mucosal edema and mechanical activation of irritated airway reflexes.155 These responses may in part be mediated by the vagus nerve because preoperative administration of an anticholinergic agent, such as glycopyrrolate or atropine, has been shown to prevent or attenuate them.

Rigid bronchoscopy is associated with more trauma than flexible fiberoptic bronchoscopy. Positioning of the patient and placement of the rigid bronchoscope can result in dental trauma or laceration of the mucosa of the larynx, trachea, or bronchi. The trauma has been associated with pneumomediastinum, pneumothorax, and perforation of the esophagus. The cervical hyperextension that is required for placement of the rigid bronchoscope can cause injury to the cervical spine, vasovagal reaction, and cerebral ischemia by occlusion of vertebral arteries.

Hypoxia and hypercarbia are common complications during rigid bronchoscopy.108,156,157 Inadequate ventilation during rigid bronchoscopy can result from large air leaks along the space between the bronchoscope and the tracheal wall or from periods of apnea. There can be a serious loss of lung volume associated with plugging and atelectasis, which may be minimized by pulmonary toilet and ventilation with large tidal volumes. At the end of a procedure during general anesthesia, a single-lumen endotracheal tube should be placed, and the lung should be suctioned and ventilated with large tidal volumes to relieve atelectatic alveoli.

Transient cardiac dysrhythmias are common in patients undergoing bronchoscopy.158,159 Their causes include hypoxia, intense stimulation, hypoventilation with hypercapnia, inadequate depth of anesthesia, vasovagal reaction, β2-adrenergic agonists, and bronchodilators.

Postoperative Concerns

Barotrauma with resultant interstitial emphysema, pneumomediastinum, and pneumothorax can occur after fiberoptic and rigid bronchoscopy. Postoperatively, patients may manifest dyspnea or evidence of airway obstruction. Subglottic and mucosal airway edema can result from mechanical irritation.160,161 In addition, bleeding into the airway can result in reactive bronchospasm. Physical examination should confirm the absence of wheezing or stridor and the presence of bilateral breath sounds. A chest radiograph should be obtained to look for signs of pulmonary emphysema, mediastinal emphysema, or pneumothorax. Initial strategies for management include inhalation of cool moisturized oxygen and use of a bronchodilator. Further specific therapies may entail placement of chest tubes, administration of diuretics, pulmonary toilet, or repeat bronchoscopy.

Anesthesia for Patients Undergoing Bronchoalveolar Lavage

Bronchopulmonary lavage is indicated for management of alveolar proteinosis.162-168 The long-term improvements in arterial oxygenation, exercise tolerance, and level of activity vary from patient to patient. Some patients require annual or semiannual lavage, whereas others remain in remission for years.169 The pathophysiology of the disease is characterized by the abnormal bilateral accumulation of alveolar surfactant.169,170 Its accumulation is attributed to a failure of clearance mechanisms rather than increased formation. Most patients are diagnosed between the ages of 20 and 50 years and have symptoms of cough, fever, and chest pain. Pulmonary function tests and chest radiographs are abnormal, but definitive diagnosis requires lung biopsy.

Intraoperative Management

Unilateral lung lavage is performed by irrigation of the tracheobronchial tree with chest physiotherapy during general anesthesia (Table 54-9). The preoperative assessment should include ventilation-perfusion scans to characterize the distribution of impairment. Unilateral lung lavage requires placement of a double-lumen endotracheal tube to prevent spillage to the contralateral lung. After induction of general anesthesia, the trachea is intubated with the largest left-sided double-lumen endotracheal tube that can be positioned properly. Correct tube position is essential; it should be confirmed with a fiberoptic bronchoscope. To prevent leakage of lavage fluid into the contralateral lung, it has been suggested that the bronchial cuff be inflated to functionally separate the lungs at 50 cm/water. The patient should be ventilated with 100% oxygen to minimize the risk of hypoxemia and eliminate nitrogen from the lung. Failure to adequately denitrogenate before lavage may leave residual pockets of intra-alveolar nitrogen and thus limit the effectiveness of the procedure.

Table 54-9 Anesthetic Guidelines for Bronchial Alveolar Lavage

Table 54-9 Anesthetic Guidelines for Bronchial Alveolar Lavage

Indication

Diagnostic

Therapeutic (alveolar proteinosis, cystic fibrosis)

Monitors

Standard monitoring, optional (arterial catheter)

Anesthesia

General anesthesia (allows for sequential lavages on both sides)

Awake, sedated (lavage by bronchoscopy limited to lobe)

Ventilation

Left double-lumen endotracheal tube

Position

Lateral decubitus

Supine

Unique considerations

Single-lung ventilation

To prevent spillage to the opposite lung, endobronchial balloon should be inflated to functionally separate lungs (∼50 cm H2O)

(1) Drain 700-1000 mL warm saline into lung
(2) Manual chest percussion
(3) Drainage of fluid in Trendelenburg position
(4) Repeat until turbidity clears
(5) Repeat for contralateral lung
(6) Maintain accurate account of infusion and drainage volumes
(7) After lavage is completed, suction both lungs thoroughly, ventilate, and positive end-expiratory pressure

Intraoperative complications

Spillage of lavage fluid to contralateral lung

Hypoxia

Decrease pulmonary compliance

Pneumothorax, hydropneumothorax

Pulmonary edema

Analgesia

None required

Postoperative care

Supplemental O2

Chest radiography

The positioning of the patient is somewhat controversial. Lavage of the nondependent lung in the lateral decubitus position has the advantage of improving oxygenation by decreasing blood flow to the nonventilated lung. However, this arrangement also increases the risk of displacement of the bronchial cuff and spillage from the nondependent to the dependent lung. Lavage of the dependent lung decreases the possibility of spillage, but it may be associated with hypoxia resulting from shunt flow. The supine position balances the risk of aspiration against the risk of hypoxia.

The choice of which lung to lavage first is based on the ventilation and perfusion studies; the lung with the least perfusion is chosen to be lavaged first. The procedure is performed by instilling warm, isotonic saline by gravity from a height of 30 cm. The adult lung will accept 700 to 1000 mL of lavage fluid. Vigorous manual chest percussion is applied to the hemithorax throughout the lavage. Then the lavage fluid is drained passively into a collecting system. The lavage procedure is repeated until the drainage decreases in turbidity to near clarity so that it is possible to read fine print through a 0.25-in-diameter column of fluid. Typically, 12 to 30 L of saline are required. We warm the fluid to prevent cooling the patient. Accurate records of fluid administration and drainage are kept. After the effluent lavage fluid clears, the procedure is terminated, the lavaged lung is thoroughly suctioned, and ventilation is reestablished. Because the lavaged lung has decreased compliance, it is ventilated with a large tidal volume (15-20 mL/kg) to reexpand the alveoli. To improve compliance during the immediate postprocedure period, the patient should be positioned to enhance drainage, and secretions should be suctioned from the airway.

During the lavage procedure, most patients remain hemodynamically stable, although this procedure may increase right heart strain and decrease left ventricular filling and systemic blood pressure.171 Arterial oxygen saturation increases during lung filling and decreases with drainage. The increase in intra-alveolar pressure, resulting from fluid administration, causes an increase in pulmonary vascular resistance, thereby diverting blood flow to the ventilated side and decreasing the venous admixture. When the lavage fluid is drained, the pulmonary vascular resistance decreases, and the venous admixture increases.

Spillage of lavage fluid into the untreated lung is a serious complication. Leakage is detected by the appearance of bubbles in the lavage fluid, rales or rhonchi in the ventilated lung, discrepancy between the drained lavage fluid volumes, and arterial desaturation. If spillage is suspected, lavage should be stopped, the lung drained, and position of the double-lumen endotracheal tube confirmed. Massive spillage produces acute decreases in lung compliance and severe arterial desaturation. An unusual but serious complication of lung lavage is hydropneumothorax that is characterized by increased peak airway pressures, decreased oxygen saturation 20 minutes after an uneventful lung lavage, and a chest radiograph revealing mediastinal shift and a left pneumothorax. It was hypothesized that lung lavage decreased lung compliance by washing out surfactants, making it more susceptible to barotrauma. A chest radiograph should be obtained routinely within the first hour after lavage and compared with prelavage examination.172

Anesthesia for Patients with Bronchopleural Fistula

Etiology

The possibility of a bronchopleural fistula should be considered after pneumonectomy, lobectomy, bullectomy, volume reduction surgery, or high-speed deceleration injury. The symptoms and findings of a clinically significant bronchopleural fistula include dyspnea, subcutaneous emphysema, contralateral deviation of the trachea, expectoration of purulent material, a persistent air leak, and purulent drainage from the chest tube. Diagnosis is confirmed by bronchoscopy. Predisposing factors in patients developing air leaks after lung resection include cancer, malnourishment, debilitation, poor general condition, trauma, barotrauma, lung abscesses, immunosuppression, steroid therapy, diabetes, preoperative or postoperative radiation therapy, and pulmonary resection for tuberculosis. A continued air leak can lead to infection in the pleural space and dehiscence of the bronchial stump.173

Therapeutic Management

When bronchopleural fistula occurs early after resection, prompt resuturing of the bronchial stump may correct it. If the fistula develops later after operation it may be secondary to infection, and adequate drainage and reduction of the pleural space constitute initial therapy. Many small fistulas will close spontaneously using conservative therapy consisting of nutritional support, pulmonary toilet, antibiotics for infection, and spontaneous ventilation. If the lung expands to fill the thoracic cavity, the leak usually can be controlled with passive chest tube drainage. A persistent space indicates a leak from a larger bronchus, usually requiring surgical treatment.173 Sepsis should be controlled with antibiotics and adequate chest drainage.

Surgical options include (1) decortication if the lung is entrapped by a thick purulent layer; (2) revision of a long bronchial stump; (3) closure of the bronchopleural fistula with a pedicled muscle flap, usually in the form of an intercostal or serratus flap174,175; (4) thoracoplasty to obliterate the pleural space, usually combined with a pedicled muscle flap to cover the bronchial stump; (5) bronchoscopic application of fibrin glue to seal the communication; and (6) temporary deployment of a silastic stent.

Ventilation

Anesthesiologists care for patients with bronchopleural fistula either in the ICU when respiratory failure and sepsis require ventilator management or in the operating room. Goals include maintenance of adequate ventilation and oxygenation and protection of the contralateral lung from spillage of purulent material.

Application of positive pressure by a mask or a mechanical ventilator may lead to an apparent inadequate ventilation because the tidal volume is lost through the fistula. Several methods have been developed to improve the ventilation of patients with bronchopleural fistula and decrease the risk of pneumothorax. Chest tubes with unidirectional valves have been used to prevent air leak during spontaneous inspiration. During positive pressure ventilation, low inflation pressures should be used, and spontaneous ventilation with pressure support should be encouraged to decrease the air leak and to promote closure of the bronchopleural fistula. High-frequency ventilation has also been used to manage bronchopleural fistula but with varying results.176-178

The proposed advantage of high-frequency ventilation is that lower inspiratory pressures and smaller tidal volumes may result in less gas leak through the fistula. It appears to be less effective when patients have bilaterally diseased, noncompliant lungs. The improvement in the air leak depends on a decrease in peak and mean airway pressures; it is recommended that tracheal pressures and airflow through the leak be measured during HFJV and compared with values obtained during conventional mechanical ventilation.

Anesthetic Management

Intraoperative treatment of patients with bronchopleural fistula presents unique challenges. Management strategies for induction and intubation depend on the severity of the bronchopleural fistula and presence of infection. If a chest tube is not in place or is malfunctioning, accumulation of escaping air into the enclosed pleural space will result in a tension pneumothorax. Because positive pressure ventilation increases the air leak and risks contaminating the noninfected lung, patients often are induced using rapid sequence induction to minimize the time before tracheal intubation and lung isolation. An alternative approach is to intubate a spontaneously ventilating patient with a double-lumen tube. Awake, sedated intubation may be considered for patients at increased risk for aspiration of gastric contents caused by full stomach or a bronchopleuroenteric fistula.179 Once the tube has been positioned, the healthy lung should be isolated immediately, and the head placed slightly raised to decrease the likelihood of contamination of the healthy lung.

In patients with a small chronic bronchopleural fistula with a minimal air leak and no associated infection or empyema, a standard endotracheal tube can probably be used safely. If intermittent positive pressure ventilation is then found to be inadequate, the tube can be advanced into the bronchus of the healthy side or replaced with a double-lumen tube. If an empyema is present, it should be drained before induction of anesthesia. Decreasing the amount of pus in the pleural cavity reduces the chance of contaminating the contralateral lung and developing a tension pneumothorax. If intermittent positive pressure ventilation using a double-lumen tube provides inadequate oxygenation or ventilation, HFJV to the affected lung through the double-lumen tube is another option.119 When a double-lumen tube cannot be used, as in small pediatric patients or in those with difficult airway anatomy, lung separation can be achieved by endobronchial placement of a single-lumen endotracheal tube.

Our choice is to thoroughly denitrogenate/preoxygenate, and if no difficulty in managing the airway is expected we place and position the double-lumen tube immediately after induction so we can exclude the fistulae from positive pressure ventilation.

Anesthetic Implications of Spontaneous Pneumothorax

Patients who develop spontaneous pneumothorax usually are young, healthy, and sometimes athletic, with no preexisting lung disease and no previous lung resections. Surgical treatment for spontaneous pneumothorax includes pleurectomy and chemical pleurodesis.180

Surgical treatment is indicated in the following situations: (1) failure of the pneumothorax to resolve with chest tube drainage and suction, which indicates that bronchopleural fistula has formed; (2) if a second ipsilateral or a first contralateral spontaneous pneumothorax occurs; and (3) if the patient's lifestyle is such that a recurrence may be life threatening or highly inconvenient (recurrence rate for spontaneous pneumothorax is 10%-25%).

When patients with pneumothorax come to the operating room, they typically have a chest tube in place, and therefore tension pneumothorax usually is not a major concern. Patients usually are treated with a double-lumen endotracheal tube to facilitate surgical exposure for either thoracoscopy or thoracotomy. If a single-lumen tube is placed and if the air leak is too large, a then that tube can be advanced into the bronchus of the unaffected side with the guidance of a fiberoptic bronchoscope or replaced with a double-lumen tube.

Anesthesia for Patients Undergoing Bullectomy and Volume Reduction Pneumoplasty

There was a resurgence in the surgical management of bullous disease and emphysema from 1995 to 2005. Multiple studies have documented the efficacy of this procedure for patients with isolated large bullae, although the benefits of resection of diseased peripheral lung tissue in the presence of bullous emphysema are less certain. Large multicenter trials are under way to assess the efficacy of this therapeutic modality.

Bullae are air-filled spaces within the lung parenchyma. As bullae expand, the volume of the remaining lung is reduced (Fig. 54-27). The rationale for the surgical resection of the diseased lung is to remove areas of nonfunctional lung to permit reexpansion of compressed functional alveoli and to improve diaphragmatic function.18,181 Preoperative evaluation includes pulmonary function testing, chest radiograph, CT, and ventilation-perfusion scanning to predict which patients will benefit from bullectomy. Patients most likely to benefit from the plication of large bullae are those in whom the bullae occupies greater than 30% of the hemithorax,182-184 those with progressively enlarging nonfunctional pulmonary units and recurrent pneumothoraces, and those with moderate to severe dyspnea that is refractory to conventional medical therapy.183 A prospective trial with 20 patients reported an increase in FEV1 (0.77-1.4 L), FVC (2.2-2.8 L), and arterial oxygenation on inspired room air (64-70 mm Hg). The patients experienced less dyspnea and improved quality of life during the next 6 months. The beneficial effects were attributed to expansion of the remaining lung and improved diaphragmatic function, resulting in improved respiratory mechanics and decreased ventilation-to-perfusion mismatching. Another study reported more modest improvements in symptoms and pulmonary function analysis (FEV1, 1.74-1.85 L; FVC, 1.82-2.21 L) and was associated with a mortality rate of 5.5%.184 It is not known whether the difference between these 2 studies reflected patient selection or a difference in surgical technique. In the first study, resection was performed by open thoracotomy using a stapler, and in the latter study, resection was accomplished by thoracoscopy using laser technology. The goals of future studies will be to improve surgical techniques, ascertain the efficacy of volume reduction surgery, and define the patient population who would benefit most from the procedure.

Figure 54-27.

Characteristic radiographic findings of patients with bullous disease. Typical findings in patients with chronic obstructive pulmonary disease (COPD) include an increased size of lung fields and flattened hemidiaphragms. The appearance of hyperaeration of both apical lung fields (bracketed area), decreased vascular marking in upper lung fields, and compressive atelectasis of the lower lung fields also are consistent with severe bullous lung disease.

Lung Volume Reduction Surgery

In 1995 Cooper initiated a renewed interest in lung volume reduction surgery (LVRS), the technique of removing hyperinflated emphysematous lung to allow normal lung more space to function properly.185 From this case series, many institutions started offering this invasive procedure to this high-risk patient population. Although many centers reported good results, increased rates of morbidity and mortality raised a need for a comprehensive multicenter trial.

The National Emphysema Treatment Trial (NETT)186 was designed to determine if LVRS in combination with pulmonary rehabilitation led to greater improvements in functional capacity compared to pulmonary rehabilitation with medical therapy alone. The trial was a 4-year, multicenter study. Inclusion criteria were crafted to enroll patients with severe obstructive lung disease of varying anatomic distributions. Exclusion criteria eliminated patients at very high risk for perioperative morbidity, mortality, or other medical conditions that would decrease the likelihood of completing the trial. Once enrolled, all subjects went through 6 to 10 weeks of pulmonary rehabilitation prior to randomization.

Surgical management consisted of bilateral stapling of diseased lung, but the surgical approach was not consistent between centers. Eight centers performed LVRS by median sternotomy only, 3 centers performed LVRS by video-assisted thoracoscopy (VATS) only, and 6 centers randomized patients to either median sternotomy or VATS. The goal of surgery was the removal of 25% to 30% of lung tissue from each side. Anesthetic management was standardized to general anesthesia and a thoracic epidural. Although epidural analgesia was originally planned only for patients undergoing median sternotomy, the use of epidural analgesia in VATS patients was center dependent.

An interim analysis of the first 1033 subjects showed that there was excessive surgical mortality in the group of very high-risk patients187 as defined by FEV1 less than 20% predicted and either a homogeneous distribution of emphysema or a DLCO less than 20% predicted.32 LVRS in this group resulted in a 30-day mortality rate of 16% compared to a 30-day mortality rate of 0% in the medically treated group. Although the survivors of surgery did exhibit modest improvements in FEV1 and distance walked in 6 minutes, their quality of life did not improve.

Analysis of the completed study of 1218 randomized subjects showed that the risk of death was equal in the surgical and the medical treatment groups.188 The surgically treated subjects had a greater improvement in exercise capacity compared to the medically treated patients. A greater than 10-W increase in exercise capacity was observed in 15% of patients treated with LVRS compared to only 3% of patients treated medically. When the high-risk patients who were identified in the aforementioned interim analysis were excluded (140 patients), there was no difference in mortality between surgical and medical groups. Exercise capacity had improved by more than 10 W in 16% of surgical patients as compared to 3% in medical patients.186

Further subgroup analysis examining the effect of distribution of emphysema produced exciting results. Patients with poor exercise capacity and predominantly upper-lobe emphysema based on CT scan had a significant decrease in mortality as compared to their medically treated matches. The risk ratio for death was 0.47; P = 0.005. Patients with non–upper-lobe predominant emphysema and high exercise had increased surgical mortality with a risk ratio for death of 2.06; P = 0.02.

Based on the subgroup analysis, the current trend is to offer patients with upper-lobe emphysema and poor exercise tolerance the option of LVRS. However, it is not clear from the publications how exercise capacity less than 15 W was determined to be poor exercise capacity. Similarly, the exact criteria used to define upper-lobe predominance of emphysema based on the CT scan of the chest needs to be described in detail. Once these additional data become available, the risks and benefits of LVRS in individual patients can be predicted with greater accuracy. This is critically important as this technique is being used more commonly as a bridge to transplant.

Surgery

These procedures may be performed as single unilateral, sequential unilateral, or bilateral operations. Single unilateral bullectomy and volume reduction procedures are performed using the lateral decubitus position and video thoracoscopy or open thoracotomy. Sequential unilateral procedures can be performed by repositioning the patient to the contralateral decubitus position after the first side is completed. Bilateral procedures can be performed through a median sternotomy. Median sternotomy does not require repositioning and provides access to the contralateral pleural space in patients with pneumothorax. Plication of bullae and resection of peripheral lung tissue are accomplished with the use of a stapler. A major complicating factor in postoperative recovery is persistent air leaks at the suture line. This problem is decreased by using a stapler with a pericardial buttress.182

Anesthetic Considerations

Patients presenting for bullectomy or LVRS have poor respiratory reserve and challenge the anesthesiologist during induction, single-lung ventilation, and extubation.189,190 Before operation, the patients often are dyspneic and require supplemental oxygen. Many may have been considered for lung transplantation, but they were excluded because of their age or presence of coexisting diseases. Their tenuous cardiopulmonary status requires judicious use of any benzodiazepines or narcotics. In addition to the standard monitors, an arterial catheter should be placed to assess adequacy of oxygen and ventilation perioperatively.

Either thoracotomy or thoracoscopy requires general anesthesia and single-lung ventilation (Table 54-10). The combination of general anesthesia and epidural analgesia decreases the anesthetic requirement intraoperatively, thereby minimizing postoperative residual sedation. Patients with end-stage emphysema tend to have increased endogenous catecholamines caused by hypoxia and hypercapnia, often are hypovolemic, and are at risk for marked hypotension after induction of general anesthesia. General anesthesia can be maintained with either inhalation of intravenous agents or with a combination of techniques. Nitrous oxide should be avoided because of the risk of increasing the size of bullae, further compressing the adjacent lung or causing rupture. Communications between bullae and the airway may function as one-way valves, resulting in air trapping with rapid enlargement and compression of the surrounding lung. Initiation of controlled ventilation may be associated with hypoxia and hypercapnia. Acute rupture of bullae with resulting pneumothorax is a constant threat. An acute decrease in blood pressure associated with increased inspiratory pressures and loss of breath sounds should be considered a pneumothorax unless proven otherwise. The prompt placement of a chest tube can avert catastrophe. Low inflation pressures, that is, inspiratory pressures less than 25 cm H2O, will decrease the risk of pneumothorax.

Table 54-10 Anesthetic Guidelines for Bullectomy and Volume Reduction Pneumoplasty

Table 54-10 Anesthetic Guidelines for Bullectomy and Volume Reduction Pneumoplasty

Bullectomy/Volume Reduction Pneumoplasty

Volume Reduction Pneumoplasty

Indication

Bullectomy—large bullae >30% of hemithorax

Volume reduction—severe bullous emphysema

Severe bullous emphysema

Preoperative concerns

Review preoperative pulmonary function tests and check arterial blood gases

Pulmonary symptoms may mask presence of coronary artery disease

Samea

Monitors

Standard monitors and A-line

Samea

Anesthesia

General anesthesia

Combined regional/general anesthesia

Samea

Additional equipment

Optional (jet ventilator)

Samea

Ventilation

Double-lumen endotracheal tube

Samea

Position

Bullectomy (lateral decubitus)

Volume reduction pneumoplasty (lateral, supine)

Lateral decubitus

Supine (median sternotomy)

Incision

Bullectomy (thoracotomy, VATS)

Volume reduction pneumoplasty (thoracotomy, VATS, median sternotomy)

Thoracotomy

VATS

Median sternotomy

Unique considerations

Single-lung ventilation

Avoid positive end-expiratory pressure

Minimize use of long-lasting respiratory depressants

Restrict administration of intravenous fluids

Samea

Intraoperative complications

Tension pneumothorax

Pneumothorax

Hypoxia

Hypercarbia

Samea

Blood loss

Minimal <500 mL

Samea

Postoperative analgesia

Epidural

Parenteral opiates/NSAIDs

Samea

Postoperative morbidity

Persistant air leak

Respiratory dysfunction

Hypoxia

Hypercarbia

Pneumothorax

Difficulty weaning from ventilator

Postoperative care

Monitor respiratory status overnight for signs of decompensation

Supplemental O2

Chest radiography

Adequate analgesia

Minimize air leak by placing chest tubes to water seal or minimizing suction

VATS, video-assisted thoracoscopic surgery.

aSame as bullectomy/volume reduction pneumoplasty.

One-lung ventilation with a double-lumen tube facilitates bilateral volume reduction by providing selective ventilation, yet retaining the capacity for intermittent ventilation of the operative lung to manage hypoxia or hypercapnia or to assist the surgeon in identifying the location of bullae. Initiation of single-lung ventilation is associated with an increase in airway pressure and the concomitant risk of pneumothorax. Jet ventilation has been used to decrease airway pressures. The nonoperated, ventilated lung should be prepped and draped to allow access in case of a pneumothorax. Increased concentrations of halogenated anesthetics may worsen the venous admixture by inhibition of HPV. Anesthetic agents are chosen to permit quick emergence and minimal postoperative sedation, an important factor in causing respiratory embarrassment.

Postoperative Ventilation

Extubation of the trachea at the end of operation can be accomplished in most patients and should be attempted to reduce the risk of air leak from continued positive pressure ventilation. The need for continued mechanical ventilation is greater after volume reduction pneumoplasty as compared with plication of bullae. The beneficial effects of operation are not realized immediately after operation. Volume reduction patients may decompensate in response to the usual decrement in postoperative pulmonary function associated with thoracic surgery and pain. They also seem to be more sensitive to residual sedation, respiratory depression from analgesics, residual muscle relaxants, or hypercapnia. The presence of a major air leak can interfere with respiratory function. Criteria for extubation include the presence of a regular respiratory pattern, adequate patient strength, alertness, ability to respond to command, and measurement of an arterial blood gas. If mechanical ventilation is required postoperatively, positive airway pressure should be minimized to decrease the chance of producing pneumothorax from rupture of residual bullae or suture lines. If air leak remains an important factor, airway peak pressure may be minimized by changing the mode of ventilation to pressure control. In addition, the chest tube suction should be put to water seal or at least the suction pressure should be minimal.

Anesthesia for Patients Undergoing Decortication and Pleurodesis Procedures

Clinical Features

The pleural space is a virtual cavity between the visceral and parietal pleura. Pleural inflammation, either infectious or noninfectious, increases permeability and results in the collection of high protein pleural fluid. Lymphatic obstruction, altered central venous pressures, and low oncotic pressure contribute to pleural fluid accumulation. Large effusions may dramatically decrease pulmonary function. Additionally, the collection of blood or empyema precipitates deposition of a fibrin layer on the pleura. As the fibrin layer (peel) matures, the underlying lung is entrapped and lung expansion is decreased, necessitating surgical intervention to release and expand collapsed lung and to manage infection.

The signs and symptoms of pleural disease include fever, chills, pleuritic chest pain, dyspnea, hemoptysis, and expectorate foul-smelling purulent sputum. Such patients may be cyanotic, hypovolemic, and hypotensive because of bacteremia and release of endotoxins. Preoperative studies include chest radiography and CT scans to locate the site of effusion or empyema.

Patients with a simple nonloculated empyema may be treated conservatively with antibiotic therapy and chest tube drainage. Once the empyema becomes loculated or develops into a fibrous peel, surgical intervention by thoracotomy or thoracoscopy is performed during general anesthesia. The access provided by VAT may be limited, and open thoracotomy may be required for a more definitive procedure. Perioperative complications include sepsis, chest tube bleeding, wound infection, bronchopleural fistula, and air leaks. Failure to adequately manage a chronic draining empyema may require the placement of an open window thoracostomy for long-term care. This procedure consists of suturing a flap of skin to the pleura, creating an epithelial-lined sinus into the empyema cavity.

Occasionally, additional intervention, pleurodesis, is required either because reaccumulation of the effusion causes respiratory compromise or is refractory to medical therapy as in the case of malignancies. A number of agents have been used intrapleurally to produce a chemical pleurodesis that leads to formation of adhesions and obliteration of the pleural space. Common sclerosing agents include tetracycline, talc, and bleomycin. Fever and chest pain are the most common complications of pleurodesis.

Anesthesia Management

Surgical decortication requires the differential ventilation of the healthy and diseased lung to facilitate surgical exposure and to permit complete reexpansion after surgical intervention.191 After induction and tracheal intubation, patients usually are placed in a lateral decubitus position with the affected lung in the nondependent position. In patients with a lung abscess, placement of an infected lung in the nondependent position increases the risk of contamination to the dependent lung. Most common management issues involve hypovolemia related to bleeding or sepsis and pain associated with decortication and pleurodesis. Inability to remove the fibrous peel may result in failure to reexpand the entrapped lung. After the decortication procedure is completed, positive pressure can be applied to the diseased lung to help break residual fibrous deposition, thus enabling lung reexpansion. We commonly place an epidural or paravertebral catheter for analgesia.

Anesthesia for Patients Undergoing Esophageal Surgery

Dysphagia is the most common symptom of esophageal disease. When present for any major length of time, dysphagia can result in weight loss, dehydration, hypoalbuminemia, anemia, and depressed immune status. Postprandial heartburn, another common symptom of esophageal disease, is related to reflux of gastric contents into the esophagus. Symptoms may manifest with change in position, exercise, or belching. Patients who experience such symptoms usually are evaluated by barium swallow under fluoroscopy, followed by esophagoscopy and tissue biopsy. Common esophageal lesions are summarized in Box 54-8.

Box 54-8

Box 54-8

Common Lesions of the Esophagus

Tumors

Squamous cell
Adenocarcinoma
Hiatal hernia

Benign strictures

Reflux esophagitis in the lower one-third of the esophagus
Caustic fluid ingestion in the upper one-third of the esophagus

Motility disorders

Achalasia
Schatzki ring

Collagen diseases (eg, scleroderma)

Diverticuli

Trachea esophageal fistula (congenital or malignant)

Traumatic perforation or rupture

Foreign bodies

Esophagoscopy

Esophagoscopy is used for tissue biopsy or clarification of esophageal lesions detected after barium contrast studies. In addition, esophagoscopy is used for removal of foreign bodies, dilation of esophageal strictures, sclerotherapy of esophageal varices, diagnosis and management of bleeding lesions, and placement of prosthetic stents across malignant strictures.

Esophagoscopy can be performed using either a rigid or a flexible fiberoptic esophagoscope. Flexible esophagoscopy allows for greater comfort while examining the upper gastrointestinal tract and usually is performed on awake, slightly sedated patients. Although rigid esophagoscopy can be performed on awake, sedated patients, it is more readily accomplished during general endotracheal anesthesia. Rigid esophagoscopy is particularly valuable for removal of foreign bodies and for the examination and management of massive esophageal bleeding.

Anesthetic Management

Fiberoptic esophagoscopy can easily be performed during topical anesthesia of the mouth and pharynx combined with mild sedation and an antisialagogue (Table 54-11). Patients should not be allowed to eat or drink until several hours after the procedure when the effect of topical anesthesia has dissipated and when protective airway reflexes have returned.

Table 54-11 Anesthetic Guidelines for Esophagoscopy

Table 54-11 Anesthetic Guidelines for Esophagoscopy

Indication

Diagnostic (biopsy mass, evaluate esophagus)

Therapeutic (removal of foreign body, arrest bleeding, sclerosis)

Monitors

Standard monitors

Anesthesia

Awake, sedated (flexible fiberoptic)

General anesthesia (flexible fiberoptic and rigid)

Additional equipment

None

Ventilation

Awake spontaneous respiration

Single-lumen endotracheal tube (may require small size or cuff deflation to pass scope)

Position

Supine

Incision

None

Unique considerations

Antisialagogue

Aspiration precautions

Intraoperative complications

Dysrhythmia

Aspiration

Hematemesis

Pneumomediastinum

Pneumoperitoneum

Pneumothorax

Dental trauma

Respiratory compromise

Perforation esophagus

Postoperative analgesia

Minimal pain (parenteral opiates, nonsteroidal anti-inflammatory drugs)

Postoperative morbidity

Hematemesis

Respiratory distress (vocal cord paralysis)

Postoperative care

Chest radiography

No eating or drinking until protective airway reflexes have returned

Rigid esophagoscopy usually is performed on patients during general anesthesia with endotracheal intubation and muscle relaxation. An anticholinergic agent is administered to decrease airway secretions and vagal responses to airway manipulation and gastric distention. Cricoid pressure should be used during induction because many patients are at risk for regurgitation from esophageal diverticuli, stenosis, or obstruction. Awake, sedated endotracheal intubation is an option. To avoid injury to the esophagus during passage of the esophagoscope, a small endotracheal tube is used, and the patient is paralyzed before introduction of the esophagoscope. It also may be necessary to temporarily deflate the endotracheal tube cuff to facilitate passage of the esophagoscope. Complications during esophagoscopy include hemorrhage, cardiac dysrhythmias, aspiration pneumonia, and perforation of the esophagus. Perforation can result in pneumothorax, pneumomediastinum, pneumoperitoneum, or subcutaneous emphysema. At the conclusion of the procedure, the trachea should remain intubated until protective reflexes have returned.

Esophageal Cancer

Patients with esophageal malignancy often are malnourished with nutritional status predictive of poor outcome. Preoperative improvement in nutritional status has been shown to decrease the incidence of wound sepsis and perioperative morbidity and mortality.161,192 Indications for total parenteral nutrition include inability to swallow food, 10% or greater decrease in body weight, serum albumin less than 3 g, cachexia and anergy, leukopenia, and low transferrin value.

Patients with esophageal cancer often are treated with chemotherapeutic agents before surgery. The perioperative implications of the previous use of antineoplastic agents for management of esophageal cancer include anemia, leukopenia, and thrombocytopenia. Drugs such as doxorubicin (Adriamycin), bleomycin, and mitomycin C have additional side effects that are important to the anesthesiologist.

Adriamycin administration can result in acute and chronic toxic cardiac effects. Acute cardiac toxicity from Adriamycin is characterized by supraventricular and ventricular dysrhythmias, abnormal conduction patterns, and ST-T wave changes. These acute changes usually resolve 1 or 2 months after cessation of therapy,193 although Adriamycin administration also may result in irreversible cardiomyopathy and congestive heart failure. To avoid this complication, the total cumulative dose of Adriamycin usually is limited to a maximum of 300 mg/m2. Adriamycin-induced cardiomyopathy is diagnosed by obtaining an endomyocardial biopsy and by determining the ejection fraction using a multigated nuclear scan (MUGA scan). If the usual maximal dose is exceeded or if patients demonstrate evidence of cardiomyopathy, then dexazoxane (Zinicard) is given before future Adriamycin therapy.

Bleomycin and mitomycin C395 administration can result in pulmonary toxicity. Early symptoms include cough, dyspnea, and rales. The toxic signs may progress to severe hypoxemia at rest and a radiologic picture similar to those with ARDS, followed by pulmonary fibrosis. Predisposing factors include age more than 20 years, dosage greater than 400 units, underlying pulmonary disease, and previous radiation therapy. O2 in high concentrations can predispose the patient to pulmonary toxicity from bleomycin. Because the duration of O2 sensitivity after the conclusion of bleomycin therapy is unknown, the lowest Fio2 necessary to maintain adequate arterial saturation should be used perioperatively.

Esophageal Surgery: Esophageal Cancer

Management Strategies

Tumors of the lower third of the esophagus are managed by esophagogastrectomy through a left-sided thoracotomy or transhiatal esophagogastrectomy and gastric pull-through technique (Fig. 54-28).194 Lesions of the middle third of the esophagus are managed by a combined laparotomy and right-sided thoracotomy.195 Lesions of the upper third of the esophagus may be managed by combined laparotomy and cervical incision (Fig. 54-29).194 Esophagogastrectomy with colon interposition is a 2-stage procedure used for lesions in the upper third of the esophagus when insufficient stomach length or gastric disease prevents performing an esophagogastrostomy. During the first stage, the esophagogastrectomy is performed through a midline laparotomy and right thoracotomy. The patient is then turned supine, and a cervical esophagostomy is performed. During the second stage, an antiperistaltic segment of the colon is passed into the retrosternal space and anastomosed to the cervical esophagus above and to the stomach remnant below (see Fig. 54-29).

Figure 54-28.

For esophagectomy without thoracotomy, the patient is in the supine position. A. Upper midline and left cervical incision (broken lines) are made. B. The extent of resection (shaded area) is shown. C. Completed anastomosis. [From Ellis FH Jr. Esophagogastrectomy for carcinoma: technical considerations based on anatomic location of lesion. Surg Clin North Am. 1980;60:275.]

Figure 54-29.

Esophagectomy with interposition of antiperistaltic segment of left colon. A. Incisions used in performance of esophagectomy, cervical esophagostomy, pyloromyotomy, and gastrostomy. B. Extent of esophageal resection (shaded area). C. Preparation of segment of left colon (shaded area) for interposition based on middle colic artery (note sites of vascular interruption, which maintain the integrity of the vascular arcade). D. Completed operation. [From Ellis FH Jr. Esophagogastrectomy for carcinoma: technical considerations based on anatomic location of lesion. Surg Clin North Am. 1980;60:277.]

The approach to surgical management of esophageal cancer is controversial. Major issues involve whether the goal is cure or merely palliation. The transthoracic approach, which involves complete resection of lymph nodes, is potentially curative, whereas the transhiatal approach is considered palliative. Other controversies include whether the patient should undergo immediate reconstruction with colon or stomach to restore continuity or delayed repair. Long-term survival appears to be a function of the stage and aggressiveness of the tumor at the time of operation rather than the type of operation. Surgical resection is associated with a local recurrence rate of 30% to 60% and 5-year survival of 20% to 25%. The addition of induction therapy of any kind does not significantly alter these survival rates.196

Anesthetic Management

Preoperative evaluation should concentrate on the hematologic, nutritional, and cardiopulmonary systems. Preoperative improvement of nutritional status improves outcome. Hypoalbuminemia, an indicator of poor nutritional status, is associated with increased tissue edema, and anemia may increase the risk of ischemia. Because the operation may be associated with episodes of hemodynamic instability and cardiac arrhythmias, the patient should receive a thorough cardiac evaluation preoperatively. Accompanying respiratory disease should be managed if possible, and strong consideration should be given to placement of an epidural catheter for postoperative analgesia.

Preoperative medication is given according to the patient's general condition to allay anxiety. The use of an anticholinergic drug may be helpful if awake intubation is planned. Guidelines for anesthetic management are presented in Table 54-12. Use of central venous catheterization is encouraged for monitoring of central venous pressure, administration of antiarrhythmics or vasopressors, and fluid resuscitation. A pulmonary artery catheter should be placed if indicated, based on the patient's cardiopulmonary status; it may prove beneficial postoperatively for optimizing fluid therapy. Arterial lines are strongly recommended, particularly for transhiatal esophagogastrectomy where surgeons bluntly dissect behind the heart and often induce profound hypotension.

Table 54-12 Anesthetic Guidelines for Esophagogastrectomy and Esophagectomy

Table 54-12 Anesthetic Guidelines for Esophagogastrectomy and Esophagectomy

Indication

Therapeutic (palliative and curative procedures for esophageal cancer)

Preoperative considerations

Assessment of nutritional status

Presence of coexisting cardiopulmonary disease

Implications of preoperative chemotherapy

Monitors

Standard monitors, optional (arterial catheter, central venous, or pulmonary artery catheters)

Anesthesia

General anesthesia, optional (combined regional and general anesthesia)

Additional equipment

Shoulder roll

Ventilation

Double-lumen ETT or bronchial blocker

Single-lumen ETT

Position

Supine

Lateral decubitus

Incision

Left thoracotomy—mobilize distal esophagus and stomach without changing positions

Right thoracotomy—good exposure of upper and mid-esophagus, easy access to the azygous vein

Abdominal transhiatal, abdominal and neck incisions, esophagus mobilized by blunt dissection

Unique considerations

Single-lung ventilation

Anticholinergic drug to block carotid sinus reflex (vagal-mediated response)

Avoid N2O with abdominal surgery

Increased risk for aspiration

Intraoperative complications

Aspiration

Hypotension

Bradycardia

Dysrhythmia

Hemorrhage

Tracheal tears

Recurrent laryngeal nerve injury

Hypoxia and hypercapnia during 1-lung ventilation

Blood loss

1000 mL, but potential for large acute blood loss

Postoperative analgesia

Epidural > parenteral opiates

Postoperative morbidity

Aspiration

Pneumothorax

Respiratory compromise

Hemoptysis

Infection

Anastomotic leaks

Postoperative care

Chest radiography

Elevate head of bed to decrease edema and improve respiratory function

Increased fluid requirements during early postoperative procedures

ETT, endotracheal tube.

Before induction of anesthesia, a large-bore nasogastric tube should be placed and the proximal esophageal pouch should be emptied. The patient should still be considered to have a full stomach because it is impossible to completely empty the esophagus through a nasogastric tube. Awake intubation during topical anesthesia or induction with cricoid pressure is indicated. If airway compression by large mediastinal lymph nodes is noted, the patient should be treated as described in the section on mediastinal tumors (see Fig. 54-1). Anesthesia is maintained using inhalation anesthetics in O2, supplemented with intermittent or continuous infusion of narcotics and nondepolarizing muscle relaxants. The combination of epidural and general anesthesia can dramatically decrease inhalation anesthetic and muscle relaxant requirements.

If thoracotomy is planned for esophageal surgery, a double-lumen endobronchial tube or bronchial blocker to permit single-lung ventilation facilitates surgical exposure. Whether a right-sided or left-sided thoracotomy is performed, a left-sided double-lumen endobronchial tube is recommended because it is easier to position and offers less risk of obstruction of the upper lobe bronchial orifice. In patients having nonpulmonary surgery, the nondependent lung usually is not severely diseased and thus contributes greatly to normal respiratory function. Paradoxically, this increases the incidence of hypoxemia during single-lung ventilation as compared with that during pulmonary surgery, and the hypoxemia may persist as long as the lung is collapsed.114

Marked fluctuating cardiovascular responses are observed frequently during transhiatal esophagectomy. Bradycardia and hypotension may result from stimulation of carotid sinus reflexes during neck dissection and mobilization of the esophagus. They are easily managed with an anticholinergic drug such as atropine. Blunt manual dissection of the esophagus through the diaphragmatic hiatus is associated with hemodynamic lability. Arterial hypertension often occurs during manual dissection of the esophagus and when the stomach is brought up through the posterior mediastinum, whereas hypotension may result from impaired venous return and cardiac function during manual dissection. These relatively long-lasting alterations in hemodynamics could be deleterious to patients with cardiac disease, and they mandate careful intraoperative hemodynamic monitoring. Patients with advanced cardiac dysfunction may not tolerate these manipulations and therefore are not good candidates for a transhiatal esophagectomy. Sudden severe intraoperative hemorrhage also can occur, and therefore large-bore venous access is essential. Other complications include tracheal damage and recurrent laryngeal nerve palsy. Tracheal damage has been reported during transhiatal esophagectomy without thoracotomy and during dissection of the middle third of the esophagus during thoracotomy.

Postoperative Concerns

Because esophagogastrectomy is associated with extensive visceral manipulations, difficulty in clearing secretions, advanced patient age with concomitant debilitation, and cardiorespiratory impairment, these patients may remain intubated overnight in the ICU. They often have increased fluid requirements during the initial postoperative period, and central venous monitoring is useful in guiding fluid management. Postoperative complications include pleural effusions, wound infection, pneumonia, and leak from the anastomotic site, resulting in mediastinitis, sepsis, hydrothorax, or pyrothorax.197 Impaired pulmonary function, airway closure, atelectasis, and hypoxemia typically occur postoperatively because of lung manipulation, residual anesthesia, and postoperative incisional pain. Effective postoperative pain control is essential to facilitate deep breathing, cough, mobilization of secretions, participation in chest physiotherapy, and early ambulation. Postoperative analgesia is most effectively achieved using a thoracic epidural. For transhiatal esophagectomy we will often use a T10 epidural with dilute bupivacaine and a separate opioid intravenous patient-controlled analgesia (IVPCA) to cover the neck incision.

Anesthesia for Patients Undergoing Laser Surgery of the Airway

Laser technology has been applied extensively for procedures on the upper and lower airways. It has been used successfully in the management of laryngeal tumors, subglottic stenosis, recurrent laryngeal papillomatosis in children, and for the removal and debulking of obstructing airway tumors.198-205

Physics of Lasers

LASER is an acronym for light amplification by stimulated emission of radiation. Laser light is a monochromatic coherent form of electromagnetic radiation that does not occur naturally. To produce a laser beam, atoms are stimulated by electrical, optical, or thermal energy. The stimulated lasing medium radiates energy in the form of light, which is then repeatedly reflected, amplified, and emitted as a laser beam. The lasing medium can be a gas (eg, helium, argon, CO2) or a solid medium (eg, ruby, neodymium ytrium-aluminum-garnet [Nd-YAG]).

The effect of the laser beam on tissues depends on its wavelength and its power density. Laser beams with long wavelengths are strongly absorbed by tissues and therefore are converted into heat energy with a very shallow depth of penetration. In contrast, laser light of short wavelength penetrates more deeply into the tissues. Therefore, a CO2 laser that has a long wavelength (10 600 nm) is absorbed at the very superficial tissue layer, which allows for precise cutting and relatively little edema formation. The Nd-YAG laser has a short wavelength (1064 nm) and penetrates more deeply into the tissues, allowing its use for tumor-debulking procedures. The potassium titanyl-phosphate (KTP) laser emits green light with a wavelength of 552 nm. This lasing medium is produced by adding KTP to Nd-YAG crystals. The KTP laser beam is absorbed by blood and is therefore more effective than an argon laser beam for operation on vascular tumors (eg, subglottic hemangiomas).

Laser Surgery of the Airway

Malignant tumors of the tracheobronchial tree lead to progressive obstruction of major airways that manifest as progressive stridor. Laser resection has been used in the treatment of partially or totally occluding airway lesions with partial or complete relief of symptoms.206-208 In patients with a totally obstructing airway lesion, lasers can be used to bore through the tumor to reestablish an airway. A serious risk of bronchial perforation and hemorrhage exists. On the other hand, a partially obstructing tumor can be approached tangentially and gradually resected, resulting in widening of the available airway lumen. For partially obstructing lesions, laser resection often provides immediate and dramatic relief of symptoms with a low incidence of bleeding complications. The Nd-YAG laser is the most frequently used laser to resect obstructing tracheobronchial tree tumors.206-208 If a CO2 laser is to be used for a subglottic lesion, a rigid bronchoscope or laryngoscope is required because the CO2 laser beam cannot be transmitted along fiberoptic bundles. For supraglottic lesions being managed with a CO2 laser, a small endotracheal tube can be used for patient ventilation, but the tube should be protected from the laser beam to prevent ignition.

Intraoperative Considerations

Safety Issues

The use of a laser in the operating room poses safety hazards for patients and operating room personnel. Warning signs on the operating room door should be clearly visible. The most common major complication of CO2 laser surgery is the risk of explosion or fire.209,210 The anesthesiologist should therefore limit the O2 concentration to the minimum needed to maintain adequate oxygenation, even if the endotracheal tube is a specific "laser" stainless steel model. For a more complete discussion the reader is encouraged to review Chapter 67.

Use of Helium

The use of helium and O2 mixtures (60%/40% to 75%/25%) during CO2 laser application has been reported to prevent ignition and fires with unwrapped PVC tubes.201,211 Helium has greater thermal conductivity, thermal capacity, and thermal diffusivity than nitrogen. These properties of helium inhibit the increase in temperature around the site of laser exposure and thus prevent spontaneous ignition. Besides protecting against airway fire, helium may improve ventilation across an obstructing airway lesion because of its lower density compared with nitrogen, thereby decreasing turbulent gas flow across the stenotic area. The problem of delivering a hypoxic gas mixture of helium in certain anesthesia machines can be circumvented by using Heliox, a commercially available O2-helium mixture.

Anesthetic Management

Laser surgery often is performed on patients who have underlying respiratory compromise, a long-term history of smoking, and a malignant process encroaching on the airway. Because many of these patients have associated COPD, it is important to evaluate their respiratory function preoperatively and treat with bronchodilators and antibiotics if indicated. Because of the risk of life-threatening airway obstruction during induction of anesthesia or manipulation of the airway, the anesthesiologist should carefully examine the radiologic and other studies to define precisely the site and extent of airway compromise. Good communication with the surgeon or pulmonologist is necessary to plan anesthetic (eg, choice of endotracheal tube will depend on the size of bronchoscope and type of laser) and management strategies in case of emergencies.

Patients at risk of developing airway obstruction or those with severe pulmonary disease should be premedicated with an antisialagogue and minimal sedation only. If the patient is not at risk for airway obstruction, sedative premedications can be administered more liberally. Some ventilation techniques described in the next section do not allow the use of capnography. In these patients, monitoring of ventilation is done by careful auscultation of breath sounds, observation of chest movements, or monitoring of arterial blood gases.

Patients with minimal or no airway obstruction can receive a routine induction of anesthesia, followed by muscle relaxation and endotracheal intubation or placement of a laryngeal mask airway. The choice of anesthetic induction technique depends on the extent of airway compromise. Patients who have major airway obstruction should maintain spontaneous ventilation during induction. Induction therefore can be achieved by inhalation agents or by administering incremental doses of intravenous hypnotics and narcotics followed by the gradual introduction of inhalational anesthetics by mask. Alternatively, fiberoptic bronchoscopy can be performed in an awake, sedated patient whose airway has been topically anesthetized (Table 54-13).

Table 54-13 Anesthetic Guidelines for Laser Ablation

Table 54-13 Anesthetic Guidelines for Laser Ablation

Indication

Therapeutic (palliative of airway obstruction related to tumor)

Monitors

Standard monitors

Optional (arterial)

Anesthesia

General anesthesia

Additional equipment

Anesthetic ventilator capable of blending an O2 and air mixture

Ventilation

Rigid bronchoscope

Single-lumen ETT (special laser tube, but may be less important when using laser way distal to the ETT)

Position

Supine

Unique considerations

Maintain Fio2 <40%

Avoid nitrous oxide (N2O; also supports combustion)

Intraoperative complications

Hemoptysis

Hemorrhage

Airway fire

Airway obstruction

Bronchospasm

Hypoxia

Perforation of the tracheobronchial tree

Analgesia

Opiates

Postoperative morbidity

Hemoptysis

Bronchospasm

Airway edema

Postoperative care

Humidified O2

ETT, endotracheal tube.

Local anesthesia can be used for laser resection of an airway tumor via flexible fiberoptic bronchoscopy. Adequate anesthesia can be achieved by topicalization of the mouth and oropharynx, spraying of the larynx and vocal cords with local anesthetics, superior laryngeal nerve block, or transtracheal injection of a local anesthetic. To avoid serious potential complications, adequate sedation is imperative when awake, sedated anesthesia is used. This technique is not recommended for patients undergoing laser airway surgery performed with a rigid bronchoscope. The degree of discomfort is greater than that with fiberoptic bronchoscopy, and patient movement resulting in trauma and misdirection of the laser beam is more likely to occur.

Use of Fiberoptic Bronchoscopy during Laser Therapy

Fiberoptic bronchoscopy for laser resection of airway tumors can be done during local anesthesia and sedation or during general anesthesia with the fiberoptic bronchoscope introduced through the lumen of the endotracheal tube or laryngeal mask airway. The device with largest lumenal diameter should be used to allow for sufficient ventilation after the fiberoptic bronchoscope is introduced. Because resistance to airflow occurs with the introduction of the bronchoscope into an endotracheal tube, patients should either receive total mechanical or pressure support ventilation to overcome the resistance created by the bronchoscope. The administration of muscle relaxants may be relatively contraindicated in patients with partial airway obstruction.

Hypercapnia is a common complication of transfiberoptic laser tumor resection, with Paco2 ranging from 45 to 60 mm Hg.204 Long-acting opioids and benzodiazepines should be avoided because of prolonged postoperative somnolence and respiratory depression. Short-action inhalation anesthetics and sedatives allow for rapid emergence without postoperative respiratory depression or sedation.

Use of Rigid Bronchoscopy during Resection of Airway Tumors

Many laser resections are performed using a rigid, open-tube bronchoscope.208 It allows easy manipulation of the laser beam and provides a greater field of vision, greater access for suction catheters, removal of tumor fragments, and promotion of homeostasis. The rigid bronchoscope can be used to establish an airway. If airway obstruction occurs, the bronchoscope is advanced distally to the site of obstruction, thereby reestablishing airway patency. The absence of a combustible endotracheal tube decreases the chance of an airway fire. Although the steel bronchoscope will not burn, carbonized tissue may flare.212 It is important to use the lowest O2 concentration needed to maintain adequate arterial saturation. The rigid bronchoscope facilitates homeostasis because the bronchoscope can be gradually withdrawn while the endoscopist coagulates bleeding sites as they appear.

Maintenance of ventilation can be achieved using 1 of several techniques. Conventional intermittent positive pressure ventilation can be maintained by connecting the anesthesia circuit to the ventilating side arm of the rigid bronchoscope, which allows the administration of O2. If a major leak occurs around the rigid bronchoscope, interfering with the adequacy of ventilation, packing the distal pharynx with gauze is helpful. Typically, anesthesia is provided by the use of intravenous agents to avoid exposing the surgical staff to any inhalational agents. Often, the patients are paralyzed to eliminate the risk of sudden, unexpected movement. Ventilation and oxygenation may be further compromised if the rigid bronchoscope is advanced into the mainstem or distal bronchi. Inadequate ventilation to the contralateral lung will result unless the bronchoscope has side holes that allow ventilation of the opposite lung.

Ventilation during periods of rigid bronchoscopy may be provided by jet ventilation. Low-frequency manual jet ventilation using the Sanders' jet injector at a frequency of 20 breaths/min has been shown to provide adequate oxygenation and ventilation.154 Total intravenous anesthesia can be achieved with intermittent or continuous infusions of propofol, etomidate, alfentanil, or remifentanil. Disadvantages of low-frequency jet ventilation include the lack of precise control of the Fio2 because of entrainment of ambient air and Venturi effect, which can lead to distal migration or aspiration of blood and tissue debris. Alternatively, HFJV at rates of 150 to 300 breaths/min can achieve satisfactory surgical conditions and provide adequate gas exchange in patients with tracheobronchial stenosis.154 At a faster rate, some hypoxemia and hypercapnia are noted, especially when the bronchoscope is advanced into a mainstem bronchus. The use of a small tidal volume at a high rate results in an immobile surgical field and decreases the chance of misdirection of the laser beam with trauma to healthy tissues. Additionally, unlike low-frequency ventilation using the Sanders' injector, which creates a Venturi effect, HFJV is associated with a continuous egress of gas to the outside, thus decreasing the chance of aspirating blood and tissue debris or forcing it into the distal airway. When arterial desaturation occurs during laser resection, the surgeon should stop the resection, thoroughly suction blood and tissue debris out of the airway, and hyperventilate with 100% O2. When adequate arterial oxygenation is reachieved, the O2 concentration can again be decreased, and the surgeon can resume laser resection.

Anesthesia for Patients Undergoing Mediastinoscopy

Mediastinoscopy and mediastinotomy are performed to diagnose and stage lung cancer to determine resectability. These procedures provide access to paratracheal, subaortic, and bronchial lymph nodes to detect metastatic spread of lung carcinomas. Lymphatics of the lung initially drain into the subaortic and paratracheal areas and then to the sides of the trachea, supraclavicular areas, and thoracic ducts. The surgical site is chosen based on likely path for regional spread of metastatic disease. Cervical mediastinal exploration (mediastinoscopy) yields a greater percentage of positive results for tumors affecting the right upper and middle lobes, and to a lesser extent left lower lobes. Anterior mediastinotomy is recommended for those patients suspected of tumor in the left upper lobe.

Mediastinoscopy is performed in patients in the supine position with the neck extended. Access is gained through an incision in the suprasternal notch, and a tunnel is created by blunt dissection anterior and slightly lateral to the trachea into the mediastinum. The rigid mediastinoscope passes posterior to the innominate and aortic pulmonary arteries down to the subcarinal area. The mediastinoscope can injure adjacent structures (Fig. 54-30). Increased risk of complications during mediastinoscopy has been noted in patients with major collateral vascular flow and in patients with abnormal or altered anatomy (Table 54-14).213

Figure 54-30.

Mediastinoscope within the mediastinum. Note the pinched innominate artery. [Modified from Petty C. Right radial artery pressure during mediastinoscopy. Anesth Analg. 1979;58:428.]

Table 54-14 Complications of Mediastinoscopy from Review of 14 Mediastinoscopy Series (1968-1970)

Table 54-14 Complications of Mediastinoscopy from Review of 14 Mediastinoscopy Series (1968-1970)

Complications

No. of Patients

Bleeding

Moderate
Necessitating thoracotomy
From superior vena cava
From brachiocephalic artery
Wound hematoma

15

4

1

Vocal cord paralysis

Left vocal cord
Side not given
Bilateral
Hoarseness, possible vocal cord paralysis

7

4

1

Pneumothorax

11

Pleural tear

3

Tumor seeding in incision line

1

Perforation of esophagus

1

Myocardial infarction (postoperative)

1

Bradycardia

4

Cardiac arrest (anesthetic error)

1

Wound infection

2

Left hemiparesis (transient)

Total

1

60

From Foster ED, Munro DD, Dobell AR. Mediastinoscopy. A review of anatomical relationships and complications. Ann Thorac Surg. 1972;13:273-286.

Anesthetic Management

Preoperative assessment should include inspection for the presence of occult airway obstruction or distortion, superior vena cava outlet obstruction, evidence of paraneoplastic syndromes, and cerebral vascular disease. The standard anesthetic plan is designed to permit rapid emergence and extubation after surgical pathology confirms adequacy of the specimen. General anesthesia with mechanical ventilation is the most commonly applied technique (Table 54-15). However, mediastinoscopy can be performed using local anesthesia with sedation in rare cases (ie, mediastinal masses with airway compromise). Muscle relaxants are advantageous for facilitating intubation, controlling ventilation, and preventing sudden movement or coughing that would increase the risk of surgical complications.214 The negative intrathoracic pressure associated with spontaneous ventilation may increase the risk of air embolism through open venous structures. Manipulation of the mediastinoscope can compress the innominate artery, thereby decreasing arterial blood flow to the right upper extremity and the right common carotid arteries, and obliterating the pulse and pressure in the right arm.215 It is recommended that a noninvasive blood pressure cuff be placed on the patient's left arm and either a pulse oximetry probe or an arterial catheter (if indicated) be placed in the right upper extremity. Waveform analysis of the arterial pressure or pulse oximeter plethysmograph trace can detect compression of the innominate artery.216

Table 54-15 Anesthetic Guidelines for Mediastinoscopy and Mediastinotomy

Table 54-15 Anesthetic Guidelines for Mediastinoscopy and Mediastinotomy

Indication

Diagnostic (biopsy mass, lymph nodes)

Monitors

Standard monitors, optional (arterial catheter)

Anesthesia

General anesthesia

Additional equipment

Shoulder roll

Ventilation

Single-lumen endotracheal tube

Position

Supine with cervical extension

Incision

Mediastinoscopy (suprasternal)

Mediastinotomy

Unique considerations

To avoid artifact induced by innominate artery compression, place noninvasive blood pressure cuff on left

To detect innominate artery compression, place pulse oximeter on right hand

Intraoperative complications

Dysrhythmia

Asthma

Hemorrhage

Pneumothorax

Recurrent laryngeal nerve injury

Respiratory compromise

Air embolism

Perforation of esophagus or bronchus

Neurologic event (compression of innominate artery or hyperextension of the neck)

Blood loss

Usually minimal

Postoperative analgesia

Parenteral opiates

Postoperative morbidity

Pneumothorax

Hemoptysis

Respiratory distress (vocal cord paralysis)

Postoperative care

Chest radiography

Elevate head of bed to decrease edema and improve respiratory function

Complications

The overall complication rate for mediastinoscopies ranges from 1.5% to 3%.213,217-219 Appreciation for the surgical risks associated with mediastinoscopy comes from an understanding of the anatomy relevant to the procedure. The most common and potentially serious complications are bleeding, cardiac tamponade, and air embolism. Compromise of other structures such as the trachea, bronchi, esophagus, laryngeal nerve, or innominate artery can lead to temporary or permanent complications. Massive hemorrhage can result from laceration of a pulmonary artery or a thoracic aortic artery.219 Therefore, a large-bore IV access catheter should be secured before induction of anesthesia. Clinical situations that increase collateral vascular flow, such as superior vena cava syndrome or aortic coarctation, predispose to bleeding and are relative contraindications to the procedure. Hemorrhage may be temporarily controlled by packing the surgical wound. Immediate mediansternotomy may be required to control bleeding. In patients with superior vena cava obstruction, intravenous access should be secured in the lower extremity to avoid distending the thoracic venous vasculature and increasing the risk of bleeding.

Laceration of venous structures in the mediastinum increases the risk of air embolism.220

Compression of the vertebral arteries from hyperextension of the cervical spine or compression of the innominate artery that feeds the right common carotid artery can cause CNS complications.216,221,222 One study documented transient decreases in blood flow for periods ranging from 15 to 35 seconds in 4 of 7 patients.221 However, the clinical significance of such transient effects is unknown.

Tracheal laceration can lead to mediastinal emphysema and loss of effective ventilation. If it is suspected, fiberoptic bronchoscopy should be used to define the site and to guide advancement of the endotracheal tube beyond the laceration. Tracheomalacia resulting from long-standing compression of the trachea by mediastinal tumor can predispose to acute tracheal injury or collapse.

Pneumothorax is the second most common complication of mediastinoscopy. It may be unilateral or bilateral, and the use of positive pressure ventilation can rapidly increase its size, causing hemodynamic compromise. It should be suspected if the patient exhibits an increase in peak airway pressures, hypotension, dysrhythmias, deviation of the trachea, or unilateral absence of breath sounds. A chest radiograph can be obtained to confirm the diagnosis if time permits. If the patient exhibits hemodynamic instability, rapid placement of a chest tube is indicated.

Postoperative Concerns

Dyspnea and respiratory difficulty may occur in the initial postoperative period. Intraoperative bleeding or edema can cause compression of the airway, especially in patients with tracheomalacia.218 Raising the head of the bed improves ventilatory mechanics, facilitates venous return, and decreases edema. Damage to the recurrent laryngeal nerve during mediastinoscopy does not become evident until after extubation. If injury to the recurrent laryngeal is suspected, the vocal cords should be visualized during extubation with the patient breathing spontaneously. Unilateral nerve damage without airway obstruction is managed conservatively.220,223 Bilateral nerve injury requires reintubation to prevent airway obstruction. Laryngeal nerve injury during these conditions is permanent in 50% of patients.224

Anesthesia for Patients with Mediastinal Masses

Patients with mediastinal masses may experience catastrophic complications during general anesthesia. Some of the most terrifying moments in the practice of anesthesiology occur while caring for patients who have mediastinal masses and undergo diagnostic procedures, especially those in the pediatric age group.

The mediastinum is divided into the superior, anterior, middle, and posterior mediastina. The most common tumors in the anterior mediastinum are thymomas, mesenchymal tumors, dermoid cysts, thyroid and parathyroid tumors, and lymphomas (Fig. 54-31 and Table 54-16). In the middle and posterior mediastinum, tumor pathologies include pericardial cysts, bronchogenic cysts, lymphomas, neurogenic tumors, and aortic aneurysms.

Figure 54-31.

Anatomic location of commonly encountered mediastinal masses.

Table 54-16 Mediastinal Mass Location

Table 54-16 Mediastinal Mass Location

Superior

Posterior

Children

Lymphoma

Neurogenic tumors

Thymoma

Teratoma

Tuberculous nodes

Esophageal duplication cysts

Retrosternal thyroid

Cystic hygroma

Diaphragmatic hernia (Bochdalek)

Parathyroid tumor

Thymoma

Pericardial cysts

Diaphragmatic hernia (Morgagni)

Adults

Lymphoma

Neurogenic tumors

Thymoma

Metastatic carcinoma

Lymphoma

Retrosternal thyroid

Teratoma

Hernia (Bochdalek)

Metastatic carcinoma

Bronchogenic cyst

Aortic aneurysm

Parathyroid tumors

Aortic aneurysm

Zenker diverticulum

Pericardial cyst

Aortic aneurysm

Signs and Symptoms

The mechanisms postulated for the clinical symptoms of respiratory and cardiovascular compromise in awake patients include (Table 54-17) (1) progressive airway obstruction caused by compression of the distal trachea or bronchi, (2) loss of lung volume, (3) compression of the pulmonary artery or the heart, (4) superior vena cava obstruction, (5) involvement of the important nervous system elements in the mediastinum (eg, recurrent laryngeal nerves, sympathetic chain), and (6) spinal cord compression from intraspinal extension of neurogenic tumors of the posterior mediastinum.

Table 54-17 Clinical Findings in Patients with Mediastinal Masses

Table 54-17 Clinical Findings in Patients with Mediastinal Masses

History

Physical Examination

Laboratory

Airway

Cough

Decreased breath sounds

Chest radiograph (posteroanterior and lateral to look for tracheal deviation or compression)

Cyanosis

Wheezing

Flow-volume loops, supine and sitting

Dyspnea

Stridor

Orthopnea

Cyanosis

Cardiovascular

Fatigue

Neck or facial edema

Chest radiographic changes in cardiac silhouette

Faintness

Jugular distension

Echocardiogram, supine and sitting

Headache

Papilledema

Shortness of breath, orthopnea

Blood pressure changes or pallor with postural changes

Cough

Pulsus paradoxus

The incidence of perioperative complications generally is related to the size of the mediastinal mass and to the extent of disease within the thoracic cavity. In 1 large series, clinical manifestations included (1) cough and pain, 40% each; (2) weight loss and fever, 24% each; (3) dyspnea and dysphagia, 20% each; (4) superior vena caval obstructions, 16%; (5) tracheal deviation, 12%; (6) Horner syndrome, 7%; (7) spinal cord compression, 5%; and (8) cyanosis, mediastinal widening, and hoarseness, 3% each. Twenty percent of patients were asymptomatic. Not all patients with mediastinal masses who have acute life-threatening airway complications during anesthesia are symptomatic preoperatively. Some are asymptomatic and show no airway compression on chest radiographs. Therefore, the severity of the patient's preoperative respiratory symptoms may be unrelated to the extent of respiratory or cardiovascular compromise encountered during anesthesia.225-227

Diagnostic Evaluation

A careful preoperative diagnostic evaluation should be performed, even in the asymptomatic patient, to determine the extent of mediastinal pathology. A flow chart describing the preoperative evaluation of patients with mediastinal masses is shown in Fig. 54-32. Most patients with mediastinal masses require scans to delineate the tumor size and location. The anesthesiologist should evaluate the extent of compression of the airway, heart, and vascular structures preoperatively.228,229 The extent of tracheal compression is a reliable predictor of whether difficulty with the airway may be expected. In 1 series, all of the patients who developed total or near-total airway obstruction during induction or emergence from anesthesia had greater than a 50% decrease in tracheal cross-sectional area as measured on CT scan.230

Figure 54-32.

Flow chart describing the preoperative evaluation of the patient with an anterior mediastinal mass. +, positive finding; −, negative workup. [From Neuman GG, Weingarten AE, Abramowitz RM, et al. The anesthetic management of the patient with an anterior mediastinal mass. Anesthesiology. 1984;60:144.]

In addition to the chest radiograph and CT scan, a series of noninvasive studies may be performed to evaluate the risk of occult airway or cardiac involvement. Upright and supine flow-volume loops are simple, noninvasive, and sensitive studies for the diagnosis of occult airway obstruction. The dynamic nature of this study makes it an extremely sensitive tool for evaluating obstructive lesions of major airways. The inspiratory limb of the flow-volume loop is useful in diagnosing extrathoracic airway obstruction, whereas the expiratory limb is sensitive to intrathoracic airway obstruction. Maximal inspiratory and expiratory flow-volume loops obtained with the patient in the upright and supine positions enable the extent of functional impairment to be quantitated and help distinguish fixed from variable intrathoracic airway obstruction.231 A disproportionate reduction in maximal expiratory flow should alert the physician to the presence of tracheomalacia and the inherent risk of airway collapse after extubation of the trachea. In addition, echocardiography in the upright and supine positions can reveal encroachment of tumor on the heart and intrathoracic vessels. Flexible fiberoptic bronchoscopy is another method of evaluating dynamic airway obstruction (Fig. 54-33). It allows assessment of the functional anatomy of the entire airway and the response of the airway to variations in intrathoracic pressure and position.

Figure 54-33.

Fiberoptic bronchoscopic appearance of lower trachea with patient in supine position (A) exhibiting almost total obstruction of trachea in the anteroposterior plane. With patient in sitting position (B), lumen appears normal. [From Prakash UBS, Abel MD, Hubmayr RD. Mediastinal mass and tracheal obstruction during general anesthesia. Mayo Clin Proc. 1988;63:1004.]

Pretreatment with radiotherapy or chemotherapy to reduce the size of the tumor decreases the risk of perioperative complications. Several investigators have suggested that patients receive empiric treatment of mediastinal pathology for the presumed diagnosis.232 Dramatic decrease in postoperative respiratory complications and improvement in risk category were achieved by preoperative radiation therapy for patients with severe clinical or radiologic findings.233 Such views are controversial, and most clinicians advocate obtaining a biopsy before initiating therapy, even if this requires administration of general anesthesia with its inherent risks. An accurate pathologic diagnosis may be compromised if patients are empirically pretreated. In addition, the option of administering radiotherapy or chemotherapy to reduce the size of the mediastinal mass is not applicable to all patients. Some patients have large, benign mediastinal masses, such as a large dermoid cyst that cannot be managed except by surgical excision. Transcarinal aspiration of a large cystic subcarinal mass can be performed through a fiberoptic bronchoscope. This technique can be used preoperatively in patients who have cystic subcarinal masses to decrease the size of the mass before anesthetic induction. It has been reported to facilitate anesthetic management intraoperatively when a patient developed airway obstruction after induction of anesthesia.234

Anesthetic Implications and Management

Symptomatic and asymptomatic patients are at risk of developing severe, life-threatening complications after induction of general anesthesia (Table 54-18). Infants and small children may have obstructive symptoms earlier than adults because their small airway size increases the magnitude of airway resistance produced by decreases in airway dimensions. To avoid the risk of complications inherent with general anesthesia, alternate diagnostic techniques can be used. Alternative methods that can be performed in awake, sedated patients include percutaneous needle aspiration of the hilum and mediastinum, mediastinotomy, and thoracoscopy.235

Table 54-18 Anesthetic Guidelines for Mediastinal Mass

Table 54-18 Anesthetic Guidelines for Mediastinal Mass

Indication

Biopsy or resection of mediastinal mass

Monitors

Standard monitors, arterial catheter

Anesthesia

Preferably awake, sedated using local anesthesia

If general anesthesia is necessary, spontaneous ventilations should be maintaineda

Additional equipment

Fiberoptic and rigid bronchoscope

Multiple-sized endotracheal tube

Standby of cardiopulmonary bypass or extracorporeal membrane oxygenation239

Ventilation

Spontaneous ventilation preferred

Intubation does not guarantee a secure patent airway

Use of flexible bronchoscope to evaluate and intubate airway

Position

As tolerated by patient (sitting, semirecumbent, or supine)

Incision

Depends on location and size of tumor

Surgical options include biopsy during local anesthesia, mediastinoscopy, mediastinotomy, median sternotomy

Unique considerations

Inability to ventilate

Risk of cardiovascular collapse

Superior vena cava syndrome (increased risk of airway edema, bleeding, placement of IV access in lower extremity)

Avoid use of muscle relaxants

Maintenance of spontaneous ventilation

Intraoperative complications

Hypoxia

Bleeding

Hypotension

Obstruction of airway

Postoperative morbidity

Airway edema, inability to extubate

Postoperative care

Monitor in intensive care environment

aUntil one can demonstrate that controlled ventilation does not cause airway obstruction or cardiovascular instability.

When the surgical procedure requires general anesthesia, the anesthesiologist and surgeon should discuss the plan and confirm the availability of equipment for emergency airway management (eg, fiberoptic and rigid bronchoscopes). Difficulties may occur during induction when the patient position is changed, when positive pressure is applied, after the administration of muscle relaxants, after intubation, during emergence, or after extubation. The patient should undergo a slow, controlled inhalational induction, with a staged approach that confirms an adequate airway before progressing. Induction may begin in a semirecumbent or seated position and progress to the supine position. After a deep anesthetic plane has been achieved, the anesthesiologist should attempt to gradually control ventilation. If wheezing or stridor ensues, the patient should be returned to spontaneous ventilation. If muscle relaxation is required to facilitate tracheal intubation, an ultrashort-acting relaxant such as succinylcholine should be used. The anesthetic technique should include the use of short-acting agents and avoidance of bolus administration of large doses of drugs. Intubation does not eliminate the risk of complications. Obstruction may even occur distal to a properly placed endotracheal tube that interferes with the normal protective glottic mechanism of physiologic PEEP that increases the tracheal distending pressure and reduces the possibility of dynamic collapse. Dynamic collapse of a tracheal segment also may occur with rapid respirations or cough during awakening from anesthesia.

Compression of the Tracheobronchial Tree

Neither the presence nor the severity of the patient's preoperative respiratory symptoms reliably predicts the extent of respiratory compromise that could be encountered during anesthesia, although most patients with severe respiratory symptoms have dramatic decreases in tracheal cross-sectional area.230 The supine position, anesthesia, and muscle paralysis are associated with decreased dimensions of the rib cage, cephalad displacement of the dome of the diaphragm, and a reduction in thoracic volume limiting the space available for the trachea.236-238 At low lung volumes, the decreased tracheal distending pressure can lead to tracheal collapse, particularly with tracheomalacia. Spontaneous ventilation is preferred to positive-pressure ventilation because the negative intrapleural pressure of spontaneous ventilation exerts a distending force that opposes bronchial and tracheal collapse. The supine position increases the central blood volume, which can further increase tumor volume and size. Edema, bleeding, and hematoma formation in the tumor as a result of surgical biopsy also can contribute to airway compromise.

Compression of Pulmonary Artery and Heart

Compression of the main pulmonary artery is relatively rare, partly because of the protective effect of the aorta. Compression of the pulmonary trunk or one of the main pulmonary arteries can result in sudden hypoxemia, hypotension, and cardiac arrest. Syncope during forced Valsalva maneuvers, such as occurs with a bowel movement, should alert the physician to the possibility of cardiovascular compression. Important factors contributing to a reduction in right ventricular output, hypotension, and severe hypoxemia include patient position, induction of anesthesia, and gravitational effects of the tumor on the heart and pulmonary artery.

Superior Vena Cava Syndrome

Pathophysiology

Superior vena cava syndrome occurs in approximately 6% to 7% of patients with lung carcinoma. Other causes include bronchial carcinoma, malignant lymphoma, and benign conditions that include multinodular goiter, mediastinal granulomas, idiopathic mediastinal fibrosis, and catheter-induced thrombosis of the superior vena cava.240 Obstruction of the superior vena cava impedes venous flow from the head and upper extremities. Clinical features are reviewed in Box 54-9. The symptoms of dyspnea, dysphasia, and stridor may be associated with ruddy complexion and dilated veins across the upper chest and neck (Fig. 54-34). The severity of clinical manifestations depends on the rate at which the SVC is occluded. Slow gradual obstruction is associated with mild signs and symptoms, whereas more severe symptoms occur with rapid onset of obstruction. The severity also depends on the extent of obstruction, site of obstruction (above or below the azygous vein), and integrity of the azygous venous system. Occlusion of the azygous venous system often is symptomatic and may require surgery to bypass the spinal vein and to resect the obstructing lesion.

Box 54-9

Box 54-9

Clinical Features of Superior Vena Caval Syndrome

Neurologic

Headache, dizziness, decreased mentation, visual changes, restlessness, agitation, Horner syndrome, stupor, convulsions

Pathophysiology

Low cardiac output, decreased cerebral perfusion, increased cerebral venous pressure, cerebral edema

Respiratory

Shortness of breath, cough, hoarseness, hypoxemia, tachypnea, stridor

Pathophysiology

Upper airway edema, tracheal obstruction, vocal cord paralysis

Cardiac

Tachycardia; thoracic and cervical venous distention; plethoric face; edema of the face, neck, upper extremities, and trunk; cyanosis; distended veins over chest wall

Pathophysiology

Decreased venous return, development of collateral venous circulation, increased peripheral venous circulation, increased peripheral venous pressure, as high as 40 mm Hg

Gastrointestinal

Nausea, vomiting, dysphagia

Pathophysiology

Fluid imbalance, upper airway edema

Renal

Decreased urine output

Pathophysiology

Low cardiac output

Figure 54-34.

Bronchogenic carcinoma producing superior vena caval obstruction. Superior vena cava syndrome is characterized by edema and rubor of face, neck, and upper chest. Arm veins fail to empty on elevation.

Choice of therapy depends on etiology. Therapeutic options include radiation, chemotherapy, and thrombectomy. Once obstruction has produced complete thrombosis, thrombectomy is of little benefit. Patients having total or near total obstruction are at risk for cerebral vascular and airway compromise, both predictors of poor outcome. A tissue diagnosis should be obtained before the institution of therapy if possible. This can be done in most patients, noninvasively by bronchoscopy or lymph node biopsy. Occasionally, an open procedure requiring general anesthesia is necessary. Magnetic resonance imaging (MRI) and contrast venography are used to define the type and location of obstruction. If biopsy of the mediastinal mass is required, an open mediastinotomy should be performed instead of mediastinoscopy because the increased venous pressure increases the risk of bleeding during cervical exploration.

Anesthetic Management

Patients with superior vena cava syndrome are at increased risk of airway compromise resulting from acute laryngospasm, bronchospasm, and airway edema caused by tumor edema or surgical manipulation.241 Venous distention and symptoms are exacerbated by changes in positioning (supine or Trendelenburg) and by administration of intravenous fluids, especially through a catheter placed in the upper extremity. All venous access should be placed in the lower extremity, and an arterial catheter should be placed to monitor blood gases and blood pressure. Venous congestion increases the risk of airway compromise, bleeding, and hypotensive episodes. The preoperative evaluation should include a careful assessment of the airway. Edema of the oral pharynx, larynx, and trachea may be more severe than the external edema and swelling of the face and neck. Venous engorgement and tumor may involve the recurrent laryngeal nerve and cause external compression of the airway. These patients should be regarded in a manner similar to those with mediastinal masses. Premedication should be limited to the administration of an antisialagogue, and the patients should be transported in a semiseated position to decrease airway edema and facilitate venous drainage. If major airway edema is present, general anesthesia should be induced in a sitting position, and fiberoptic bronchoscopy may be required for airway access. Intraoperative management may be complicated by an abnormal response to the use of muscle relaxants related to a paraneoplastic myasthenic syndrome.242 Many of these patients remain intubated postoperatively until edema of the airways and laryngeal structures is decreased.

Anesthesia for Patients with Thoracic Outlet Syndrome

Thoracic outlet syndrome refers to neurologic and vascular symptoms affecting the upper extremity resulting from compression of the neurovascular bundle at the thoracic outlet between the first rib and the clavicle or between the anterior scalene muscle and the medial scalene muscle.73,243,244 The etiology is classified either as noncancerous or cancerous.

Most noncancerous causes are related to either trauma or the presence of a cervical rib. A less frequent etiology is hypertrophy of the scalene and subclavian muscles. Clinical manifestations usually are vague and obscure, and may be misinterpreted as angina. Pain may be localized to the shoulder or extend along the medial aspect of the arm and forearm, along the proximal shoulder girdle, or to the neck and face. Symptoms may include weakness, numbness, and paresthesias. Conservative management includes rehabilitation exercises, anti-inflammatory drugs, and analgesics. In those with vascular insufficiency or if symptoms are refractory to medical therapy, operation may be indicated. Surgical approaches include resection of the first rib, partial resection of the scalene muscles, or removal of anomalous fibromuscular bands.

The presentation of lung cancer with symptoms of thoracic outlet syndrome is known as Pancoast syndrome. The most common etiology is a bronchogenic carcinoma originating in or near the superior pulmonary sulcus. These tumors invade the lymphatic system and spread by direct extension to entwine the brachial plexus intercostal arteries, stellate ganglia, and sympathetic chain, thereby producing Horner syndrome. If the tumor is considered resectable, the pulmonary tumor and extension into the chest wall and brachial plexus should be excised.

Anesthetic management includes the use of routine monitoring and may require 1-lung isolation (Table 54-19). The patient is placed in the lateral decubitus position, and an incision is made in the lower margin of the anterior axilla. Intraoperative complications include hemorrhage, pneumothorax, brachial nerve injury with resulting nerve dysfunction, temporary phrenic nerve palsy, injury to the subclavian artery, and cervical sympathectomy on the ipsilateral side. Because of the position of the nondependent arm and the site of surgery, stretch and surgical trauma to the brachial plexus is a major risk.

Table 54-19 Anesthetic Guidelines for Thoracic Outlet Syndrome

Table 54-19 Anesthetic Guidelines for Thoracic Outlet Syndrome

Indication

Therapeutic (syndrome characterized by lateral upper extremity weakness, numbness, paresthesias, pain)

Monitors

Standard monitors

Noninvasive cuff on opposite side

Ipsilateral pulse oximetry

Anesthesia

General anesthesia

Ventilation

Single-lumen or double-lumen endotracheal tube

Position

Supine or lateral decubitus position, determined by surgical approach

Incision

Cervical region (partial resection of first rib)

Scalene muscles

Unique considerations

Intravenous access on opposite side

Intraoperative complications

Pneumothorax

Pleural effusion

Vascular injury

Neural injury

Cervical sympathectomy

Blood loss

Minimal <500 mL

Postoperative analgesia

Parenteral opiates

Postoperative morbidity

Temporary phrenic nerve palsy

Pneumothorax

Brachial plexus neuralgia or palsy

Injury to long thoracic nerve and T1 roots

Postoperative care

Chest radiography

Anesthesia for Patients Undergoing Thymectomy: Myasthenia Gravis

Clinical Features

The thymus is a central lymphoid gland that functions in the development and maintenance of immunologic competence. Surgical resection of the thymus most often is performed for myasthenia gravis and less often for primary neoplasm, carcinoid tumor, or multiple endocrine neoplasm syndrome. Seventy-five percent of the patients with myasthenia gravis have associated thymic hyperplasia or thymomas.

One-third of myasthenic patients have bulbar symptoms including difficulty swallowing and clearing secretions, which predispose to pulmonary aspiration (Table 54-20).

Table 54-20 Clinical Classification of Myasthenia Gravis

Table 54-20 Clinical Classification of Myasthenia Gravis

Stage

Term

Description

I

Ocular myasthenia

Involvement of ocular muscles only; mild symptoms of ptosis and diplopia

II

Mild to moderate generalized myasthenia

Slow onset; usually ocular, spreading to skeletal and bulbar muscles; no respiratory involvement; good response to drug

III

Acute fulminating myasthenia

Rapid onset of severe bulbar and skeletal weakness with involvement of respiratory muscles; poor response to therapy

IV

Late severe myasthenia

Severe disease developing 2 years after onset of stage I or II symptoms; poor response to therapy and poor prognosis

Therapy for myasthenia gravis includes anticholinesterase drugs, corticosteroids, other immunosuppressants, plasmapheresis, and thymectomy. These therapies may be used individually or in combination. Anticholinesterase drugs, such as neostigmine or pyridostigmine, most often are selected because they provide immediate symptomatic relief. These drugs inhibit the enzyme responsible for hydrolysis of acetylcholine and thereby increase the concentration of neurotransmitter at the neuromuscular junction.245,246 Surgical resection of the thymus gland may result in complete remission or dramatic improvement in symptoms.247

Anesthetic Considerations

Management of anesthesia for patients with myasthenia gravis should consider the severity of symptoms, presence of other associated disorders (Box 54-10), and preoperative drug therapy. Considerations for the perioperative period are presented in Table 54-21. An assessment of preoperative pulmonary function should be obtained as a baseline for comparison. The patient's preoperative medications should be reviewed for those drugs that could interfere with neuromuscular function (Box 54-11). Drugs that have the potential to exacerbate muscle weakness in these patients include calcium channel blockers, aminoglycosides, and antiarrhythmic agents.248-250 Most authors recommend that patients continue their usual dose of anticholinesterase therapy the night before surgery. On the day of operation, patients who are severely symptomatic should receive a full morning dose. Those patients who are only mildly affected should receive half a dose or none at all. The rationale for withholding the morning dose is to prevent antagonism of muscle relaxants that may be used to facilitate tracheal intubation. Patients receiving systemic steroids should continue their steroid supplementation on the day of surgery.

Box 54-10

Box 54-10

Disorders Associated With Myasthenia Gravis

Thyroid disease

Hyperthyroidism
Hypothyroidism
Thyroiditis

Thymoma

Anemias pernicious

Multiple sclerosis

Ulcerative colitis

Leukemia

Lymphoma

Autoimmune disorders

Systemic lupus erythematosus

Idiopathic thrombocytopenic purpura
Rheumatoid arthritis
Scleroderma
Polymyositis
Sjögren syndrome

Table 54-21 Anesthetic Guidelines for Thymectomy: Myasthenia Gravis

Table 54-21 Anesthetic Guidelines for Thymectomy: Myasthenia Gravis

Indication

Therapeutic (myasthenia gravis, thymoma, multiple endocrine neoplasm syndrome)

Monitors

Standard monitors

Anesthesia

General anesthesia

Preoperative considerations

Review use of anticholinesterase medications

Evaluate strength

Assess respiratory function

Ventilation

Usually single-lumen ETT

Double-lumen ETT if by video-assisted thoracoscopic surgery

Position

Supine with shoulder roll

Occasionally by left lateral decubitus (thoracoscopy)

Incision

Sternotomy, transcervical

Portals for video-assisted thoracoscopic surgery

Unique considerations

Myasthenia gravis (increased sensitivity to muscle relaxants, risk of remaining intubated postoperatively, avoid neuromuscular blocking effects of antiarrhythmics, diuretics, and aminoglycosides)

Intraoperative complications

Myasthenia gravis (residual weakness or sedation leading to inability to extubate)

Blood loss

Minimal

Postoperative analgesia

Parenteral opiates, epidural

Postoperative morbidity

Respiratory insufficiency (inadequate reversal of muscle relaxants, excessive sedation, not received daily dose of anticholinesterase)

Postoperative care

Chest radiography

Optimize respiratory function (analgesics, raise head of bed)

Observe in monitored environment

ETT, endotracheal tube.

Box 54-11

Box 54-11

Drugs That Can Exacerbate Myasthenia Gravis

Acetylcholinesterase in high doses

Aminoglycosides

Other antibiotics (eg, clindamycin, colistin, polymyxin B, tetracycline, trimethaphan)

Antidysrhythmics (eg, procainamide, quinidine, propranolol, lidocaine)

Thyroid hormones

Quinine (tonic water)

Phenytoin (Dilantin)

Special attention should be given to the psychological preparation of these patients. They should be told about the increased risk of prolonged muscle weakness and respiratory depression that may uncommonly require temporary postoperative ventilation.

All patients undergoing thymectomy require general anesthesia regardless of the surgical approach. In patients undergoing a transmediastinal approach, the use of an epidural block as an adjunct to general anesthesia has been found to decrease the intraoperative MAC, lessen postoperative analgesic requirements, improve respiratory mechanics, and dramatically decrease the frequency of prolonged intubation.251 Use of a muscle relaxant is not required but may facilitate tracheal intubation. Patients with myasthenia gravis have a marked sensitivity to nondepolarizing muscle relaxants, increasing their sensitivity and duration of action. If muscle relaxation is required, a small dose of a short-acting nondepolarizing drug such as cisatracurium should be used. Although muscle relaxation is usually less sensitive to succinylcholine in patients receiving anticholinergic therapy, its duration of action may be extended. If succinylcholine is to be used, the dose should be reduced to avoid prolongation of the response and associated phase-2 block.251-254 Halogenated inhaled anesthetics have muscle relaxing properties. One study found that patients with myasthenia gravis were more sensitive to the neuromuscular depressant effects of isoflurane.255 Recovery of the electromyographic response was still incomplete 1 hour after terminating isoflurane, despite satisfactory clinical recovery.

The most common surgical approaches are the transcervical and transsternal approaches; a minority of cases is performed by thoracotomy or VAT. The transcervical approach has the advantage of avoiding the immediate postoperative alterations in pulmonary mechanics.252,256,257 Mediastinotomy may be necessary when resecting a hypertrophied thymus that extends substernally. If mediastinotomy or the cervical approach is to be used, a single-lumen tube is appropriate. Alternatively, a double-lumen endotracheal tube or bronchial blocker is indicated if lateral thoracotomy is planned.

Postoperative Concerns

Improvement in myasthenic symptoms after thymectomy may take weeks to months. Therefore, the patient should receive any missed dose of anticholinesterase from the morning of operation. At the end of the operation, neuromuscular transmission is assessed using a nerve stimulator; nondepolarizing muscle relaxants are reversed. Residual weakness from an inhaled anesthetic can cause fade in the response to tetanic stimulation. Suitability for extubation is judged by measuring the patient's pulmonary function and comparing the results with preoperative values. Negative inspiratory force, tidal volume, and vital capacity should be measured immediately before induction and used as the basis for comparison. To improve respiratory mechanics, the patient is placed in a semirecumbent position with the head of the bed raised about 30 degree, is suctioned for secretions, and receives adequate analgesia without inducing respiratory depression. The patient should be monitored closely for 18 to 24 hours after operation. A chest radiograph is obtained immediately postoperatively to rule out the presence of a pneumothorax.

Anesthesia for Patients Undergoing Tracheal Resection and Tracheobronchial Reconstruction

Indications for tracheal resection include

Tracheal tumors, most of which are malignant
Carinal tumors or carinal involvement with a bronchogenic carcinoma
Tracheal involvement with a thyroid carcinoma
Traumatic disruption of the trachea and bronchi, which may occur as a result of blunt trauma, penetrating injuries, iatrogenic manipulations, and aspirated sharp foreign bodies
Tracheal stenosis after prolonged intubation, trauma, etc

Patients undergoing surgical resection of the trachea, main bronchi, or both impose special anesthetic management problems. The surgical procedure often is prolonged, and episodes of ventilatory insufficiency may be unavoidable. Communication between the anesthesia and surgical teams, with emphasis on the ventilatory treatment of the patient during each phase of the procedure, is imperative. The most challenging aspect of these procedures is to design an effective method of ventilating the lungs during the resection and reconstruction of the airway that does not interfere with surgical exposure and that provides adequate ventilation and oxygenation. Patients with large intratracheal or carinal masses may develop total airway obstruction on the induction of anesthesia. Fortunately, many of these patients undergo laser debulking procedures before undergoing surgical resection. Because an inflated cuff and positive-pressure ventilation adjacent to the suture line may interfere with healing or cause disruption of the anastomosis, after the procedure the patient should breathe spontaneously and be extubated in the operating room or shortly thereafter.

Surgical techniques may include resection and primary anastomosis, resection, and reconstruction with prosthetic material or with the insertion of a T-tube stent.

Therapeutic adjuncts may include radiotherapy (preoperatively or postoperatively), radioactive seed implantation, and preoperative laser debulking.

Surgical Considerations

Surgery on the trachea and bronchi usually is done through a right thoracotomy to avoid the aortic arch, although if the left bronchus is involved or a left pulmonary resection may be done, a left thoracotomy may be performed. The surgical procedure requires extensive hilar dissection, mobilization of the lungs, and possibly opening of the pericardium. The omentum, serratus muscle, or intercostal muscle may have to be used to wrap the anastomosis or to cover defects in the tracheobronchial tree. Mobilization of the omentum requires an additional abdominal incision. Thoracoabdominal exposure substantially increases fluid requirements. On occasion, pericardium may be used to patch sections of the pulmonary artery involved with tumor. Every effort should be made to maintain normothermia and minimize heat loss. After the procedure, to decrease tension on the anastomosis, it may be necessary to maintain the patient's neck in a flexed position by suturing the skin and soft tissues of the chin to the anterior chest wall. Even in this situation, it is advantageous to extubate the trachea as soon as possible after surgery to minimize airway pressures. Therefore, the anesthetic should be planned with the goal of rapid emergence and recovery from muscle relaxants. Thorough suctioning of the tracheobronchial tree, via a fiberoptic bronchoscope if indicated, should be performed immediately before emergence from anesthesia.

Postoperative complications, particularly pulmonary infections and air leaks through the airway anastomosis, can lead to the development of a bronchopleural fistula and respiratory failure. Factors that predispose to poor healing of the tracheobronchial anastomosis include cancer, previous steroid and antineoplastic chemotherapy, preoperative radiotherapy, extensive dissection and devascularization of the tracheobronchial stump, and poor nutritional status and debilitation. In selecting the technique for airway management, the anesthesiologist should consider the need to provide appropriate surgical conditions. Constant cooperation and communication between the surgical and anesthesia team are extremely important during these procedures.

Perioperative Management Issues

Preoperative Assessment and Preparation

Patients should be evaluated for airway patency and cardiopulmonary reserve. Unless airway obstruction is imminent, requiring emergency surgery, pulmonary function studies should be obtained (Figs. 54-35 and 54-36). Flow-volume loops are very helpful in detecting fixed or variable intrathoracic or extrathoracic obstructions. Most of these patients have serious underlying pulmonary disease that may further compromise gas exchange intraoperatively and postoperatively. Reversible conditions that alter pulmonary function should be managed with antibiotics and bronchodilators preoperatively. All considerations that apply to patients with airway obstruction resulting from extrinsic compression by mediastinal masses also apply to patients with intrinsic obstruction of the airways. Preoperative ABG values should be obtained. Mucosal edema frequently contributes to airway obstruction in these patients, and preoperative steroids and diuretics may be beneficial.

Figure 54-35.

Idealized flow-volume loop. During forced expiration, the rate of airflow increases rapidly at volume close to TLC. As lung volume decreases, flow progressively falls in a near-linear fashion caused by increasing airway resistance. With maximum inspiratory effort, flow normally peaks at a lung volume near the midportion of FVC. At midpoint lung volume, the forced inspiratory flow (FIF50) and forced expiratory flow (FEF50) should normally be equal. When the ratio (FIF50/FEF50) is less than unity, it suggests an extrathoracic obstruction, compromising inspiratory flow. If greater than 1, it supports a diagnosis of intrathoracic airway obstruction.

Figure 54-36.

Maximal inspiratory and expiratory flow-volume curves in fixed obstruction (intrathoracic or extrathoracic), in which airway diameter does not change with inspiration or expiration, extrathoracic variable obstruction, or intrathoracic variable obstruction. The dotted line indicates 50% of the vital capacity; the ratio of expired-to-inspired flow at this point is the mid-VC ratio and is normally 0.9 to 1.0. A. With a fixed obstruction, expiratory and inspiratory flows are equally altered, and the mid-VC ratio remains normal. B. With a variable extrathoracic obstruction, forced expiration results in a slightly positive (+) intratracheal pressure that is greater than the pressure around the airway (atmospheric or 0), resulting in a decrease of the obstruction (airway dilates). During forced inspiration, when pressure around the airway (0) exceeds the intratracheal pressure (−), the obstruction is increased (airway narrows). Because the expiratory curve is normal and the inspiratory curve is altered, the mid-VC ratio is much greater than normal. C. With a variable intrathoracic obstruction, forced expiration results in a very positive (++) pleural pressure that is greater than the slightly positive (+) intratracheal pressure, resulting in an increase of the obstruction (airway narrows). During forced inspiration, the intratracheal pressure (−) is greater than the pleural pressure (− −), thus decreasing the obstruction (airway dilates). Because the inspiratory curve is normal and the expiratory curve is attenuated, the mid-VC ratio is much less than normal. Normal flow-volume curve (A) is a composite of the inspiratory curve in B and the expiratory curve in C. TLC, total lung capacity; RV, residual volume. [Benumof JL. Anesthesia for special elective therapeutic procedures. In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]

Induction of Anesthesia

Induction of anesthesia follows the same guidelines as discussed in the section on anesthesia for patients with mediastinal masses. The anesthesiologist should know precisely the site and the size of the lesion and the extent of airway lumen compromise before induction of anesthesia. The anesthesiologist should review the chest radiographs, tomograms, CT scans, flow-volume loops, and results of bronchoscopy or bronchography preoperatively. A skilled endoscopist usually can pass a small-diameter ventilating bronchoscope past the lesion, allowing ventilation of at least 1 lung. Once ventilation and oxygenation have been satisfactorily established, intubation of the trachea may be attempted, perhaps over a stylet introduced via the rigid bronchoscope.

Modes of Ventilation

The major challenge during operation for tracheobronchial resection and reconstruction is the maintenance of ventilation. The options include (1) a single-lumen endotracheal tube; (2) a single endobronchial tube or 2 endobronchial tubes, 1 into each mainstem bronchus distal to the area of resection; (3) low-frequency jet ventilation; (4) high-frequency ventilation to 1 or both lungs, above the site of the lesion; or (5) cardiopulmonary bypass through the femoral approach during resection of the carina.258,259 Because of the risk of intrapulmonary hemorrhage with heparinization, cardiopulmonary bypass should be used only in selected patients when absolutely necessary.

Use of Conventional Ventilation for Tracheobronchial Reconstruction

When planning to use conventional ventilation during tracheobronchial reconstructive surgery, the anesthesiologist should have several different sizes of armored endotracheal tubes available, some of them still sterile. A long, sterile anesthesia circuit is required because it often is necessary for the surgeon to intubate the trachea or bronchus within the sterile field. Airway management depends on the location of the lesion and its distance from the carina.

Resection of a High Tracheal Lesion

A single-lumen, uncut endotracheal tube is placed above the tracheal lesion after induction of general anesthesia. If the obstruction is mild or if the area of obstruction can be bypassed, mechanical positive-pressure ventilation is safe. The surgeon may help guide the endotracheal tube past the area of stenosis when the trachea is open. Alternatively, a sterile tube can be passed through the field into the distal trachea after the trachea has been transsected below the lesion. That tube is then connected, via sterile anesthesia hoses and Y piece, to the anesthesia machine. Armored endotracheal tubes should be used to decrease the possibility of kinking and obstruction. If the distal segment of the trachea is short, the tip of the endotracheal tube can be cut distal to the cuff to allow the tube to remain above the carina (Fig. 54-37).

Figure 54-37.

Procedure for resection of high tracheal lesion. [Modified from Geffin B, Bland J, Grillo HC, et al. Anesthetic management of tracheal resection and reconstruction. Anesth Analg. 1969;48:884.]

Repair of a high tracheal lesion usually is done through a cervical incision, possibly combined with a median sternotomy. After excision of the tracheal lesion and placement of the posterior tracheal suture line, the distal endotracheal or endobronchial tube is removed from the trachea. The proximal endotracheal tube then is advanced past the anastomotic lines and reconnected to the anesthesia circuit, and the anastomosis is completed.

Resection of a Low Tracheal Lesion

This usually is performed through a right thoracotomy incision. A single-lumen endotracheal tube is placed with its tip above the lesion. If sufficient length of trachea distal to the area of resection is available, a Foley catheter with its tip removed just distal to the balloon may be used as a single-lumen endotracheal tube. It is inserted by the surgeon and maintained in place above the carina, thereby avoiding endobronchial intubation and the need for 1-lung ventilation. If the distal tracheal stump is very short, the tube should be advanced into the bronchus of the dependent (usually the left) lung. If oxygenation is inadequate, the shunt can be decreased by temporarily clamping the pulmonary artery of the nondependent side (Fig. 54-38).260,261 When the posterior tracheal suture line has been completed, the distal endobronchial tube or Foley catheter is removed, and the original orotracheal tube is advanced across the suture line into the bronchus of the dependent lung. The anterior suture line then is completed. The endotracheal tube is then pulled proximally so that its tip lies above the suture line.

Figure 54-38.

Procedure for resection of lower tracheal lesions. [Modified from Geffin B, Bland J, Grillo HC, et al. Anesthetic management of tracheal resection and reconstruction. Anesth Analg. 1969;48:884.]

For carinal resection, a single-lumen endotracheal tube is inserted through the larynx (Fig. 54-39). After the carina is resected, the surgeon places a second endotracheal tube into the bronchus of the dependent lung, usually the left. The tube is connected by a set of sterile anesthesia hoses and Y piece to the anesthesia machine. The left lung is ventilated through the endobronchial tube, whereas the right lung is collapsed as the right bronchus is attached to the trachea. After the right mainstem bronchus has been reattached to the trachea, the original translaryngeal endotracheal tube is advanced past the suture line into the right mainstem bronchus. Cutting the tip of this endotracheal tube helps to prevent obstruction of the right upper-lobe bronchus. The left endobronchial tube then is removed, and the left mainstem bronchus is attached to the trachea by an end-to-side anastomosis. The endotracheal tube then is pulled proximally so that its tip is above both anastomotic lines.

Figure 54-39.