Lung resections are usually carried out for the diagnosis and treatment of pulmonary tumors, and, less commonly, for traumatic lung injury, bullae, complications of necrotizing pulmonary infections, or bronchiectasis.
Pulmonary tumors can be either benign or malignant, and, with the widespread use of bronchoscopic sampling (often guided by endobronchial ultrasound), diagnosis is usually available prior to surgery. Hamartomas account for 90% of benign tumors; they are usually peripheral pulmonary lesions and represent disorganized normal pulmonary tissue. Bronchial adenomas are usually central pulmonary lesions that are typically benign, but occasionally may be locally invasive and rarely metastasize. These tumors include pulmonary carcinoids, cylindromas, and mucoepidermoid adenomas. They often obstruct the bronchial lumen and cause recurrent pneumonia distal to the obstruction in the same area. Primary pulmonary carcinoids may secrete multiple hormones, including adrenocorticotropic hormone (ACTH) and arginine vasopressin; however, manifestations of the carcinoid syndrome are uncommon and are more likely with metastatic disease.
Malignant pulmonary tumors are divided into small (“oat”) cell and non–small cell carcinomas. The latter group includes squamous cell (epidermoid) tumors, adenocarcinomas, and large cell (anaplastic) carcinomas. Epidermoid and small cell carcinomas usually present as central masses with bronchial lesions; adenocarcinoma and large cell carcinomas are more typically peripheral lesions that often involve the pleura.
Symptoms may include cough, hemoptysis, wheezing, weight loss, productive sputum, dyspnea, or fever. Pleuritic chest pain or pleural effusion suggests pleural extension. Involvement of mediastinal structures is suggested by hoarseness that results from compression of the recurrent laryngeal nerve, Horner’s syndrome caused by involvement of the sympathetic chain, an elevated hemidiaphragm caused by compression of the phrenic nerve, dysphagia caused by compression of the esophagus, or the superior vena cava syndrome caused by compression or invasion of the superior vena cava. Pericardial effusion or cardiomegaly suggests cardiac involvement. Extension of apical (superior sulcus) tumors can result in either shoulder or arm pain, or both, because of involvement of the C7–T2 roots of the brachial plexus (Pancoast syndrome). Distant metastases most commonly involve the brain, bone, liver, and adrenal glands.
Lung carcinomas—particularly small cell—can produce remote effects that are not related to malignant spread (paraneoplastic syndromes). Mechanisms include ectopic hormone production and immunological cross-reactivity between the tumor and normal tissues. Cushing’s syndrome, hyponatremia (syndrome of inappropriate antidiuretic hormone secretion [SIADH]), and hypercalcemia may be encountered, resulting from ectopic secretion of ACTH, arginine vasopressin, and parathyroid hormone, respectively. Lambert–Eaton (myasthenic) syndrome is characterized by a proximal myopathy in which muscle strength increases with repeated effort (in contrast to myasthenia gravis). Other paraneoplastic syndromes include peripheral neuropathy and migratory thrombophlebitis.
Surgery is the treatment of choice to reduce the tumor burden in nonmetastatic lung cancer. Various perioperative chemotherapy and radiation treatments are likewise employed, but there is wide variation among tissue types in their sensitivity to chemotherapy and radiation.
Resectability & Operability
Resectability is determined by the anatomic stage of the tumor, whereas operability is dependent on the interaction between the extent of the procedure required for cure and the physiological status of the patient. Anatomic staging is accomplished using chest radiography, computed tomography (CT) or magnetic resonance (MR) imaging, bronchoscopy, and (sometimes) mediastinoscopy. The extent of the surgery should maximize the chances for a cure but still allow for adequate residual pulmonary function postoperatively. Lobectomy via a posterior thoracotomy, through the fifth or sixth intercostal space, or (more commonly) using video-assisted thoracoscopic surgery (VATS), is the procedure of choice for most lesions. Segmental or wedge resections may be performed for initial diagnosis or for definitive treatment of small peripheral lesions. Pneumonectomy is necessary for curative treatment of lesions involving the left or right main bronchus or when the tumor extends toward the hilum. A sleeve resection may be employed for patients with proximal lesions and limited pulmonary reserve as an alternative to pneumonectomy; in such instances, the involved lobar bronchus, together with part of the right or left main bronchus, is resected, and the distal bronchus is reanastomosed to the proximal bronchus or the trachea. Sleeve pneumonectomy may be considered for tumors involving the trachea.
The incidence of pulmonary complications after thoracotomy and lung resection is about 30% and is related not only to the amount of lung tissue resected, but also to the disruption of chest wall mechanics due to the thoracotomy. Postoperative pulmonary dysfunction seems to be less after VATS than “open” thoracotomy. The mortality rate for pneumonectomy is generally more than twice that for a lobectomy. Mortality is greater for right-sided than left-sided pneumonectomy, possibly because of greater loss of lung tissue.
Evaluation for Lung Resection
A comprehensive preoperative assessment is necessary to assess and modify perioperative risk; minimize perioperative complications, hospital length-of-stay, and hospital readmission risk; and optimize outcomes. Preoperative assessment of respiratory function may include determinations of respiratory mechanics, gas exchange, and cardiorespiratory interaction. Spirometry and diffusion capacity are initially assessed and can be used to predict postoperative values. In a fit, younger patient undergoing VATS for a peripheral “coin” lesion, not all of these tests will be needed. For example:
Postoperative FEV1 = preoperative FEV1 × (1 – the percentage of functional lung tissue removed divided by 100)
Removal of extensively diseased lung (nonventilated but perfused) does not necessarily adversely affect pulmonary function and may actually improve oxygenation. Mortality and morbidity are significantly increased if postoperative FEV1 is less than 30% to 40% of normative FEV1. Gas exchange will sometimes be characterized by diffusion lung capacity for carbon monoxide (DLCO). DLCO correlates with the total functioning surface area of the alveolar–capillary interface. Predictive postoperative DLCO can be calculated in the same fashion as postoperative FEV1. If both the predicted DLCO and FEV1 are greater than 60%, the patient is generally at lower risk for lung resection. Cardiopulmonary exercise testing is warranted when either of the tests is less than 30%. Ventilation/perfusion (V̇/Q̇) scintigraphy provides the relative contribution of each lobe to overall pulmonary function and may further refine the assessment of predicted postoperative lung function in patients when pneumonectomy is the indicated surgical procedure and there is concern about whether a single lung will be adequate to support life.
Patients considered at greater risk of perioperative complications (predicted FEV1 or DLCO between 60% and 30%) based on standard spirometry testing and calculation of postoperative function should undergo exercise testing for evaluation of cardiopulmonary interaction. Stair climbing is the easiest way to assess exercise capacity and cardiopulmonary reserve. Patients capable of climbing two or three flights of stairs have decreased mortality and morbidity. Conversely, the ability to climb less than two flights of stairs is associated with increased perioperative risk. The gold standard for evaluating cardiopulmonary interaction is by cardiopulmonary exercise testing (CPET) and measurement of maximal minute oxygen consumption. V̇O2 of greater than 20 mL/kg is not associated with a significant increase in perioperative mortality or morbidity, whereas minute consumption of less than 10 mL/kg is associated with an increased perioperative risk.
A combination of tests to evaluate the patient for thoracotomy and major pulmonary resection is recommended by the American College of Chest Physicians (Figure 25–10).
Physiological evaluation resection algorithm. (a) For pneumonectomy candidates, we suggest using Q scan to calculate predicted postoperative (PPO) FEV1 or DLCO values (PPO values = preoperative values × [1 – fraction of total perfusion for the resected lung]), where the preoperative values are taken as the best measured postbronchodilator values. For lobectomy patients, segmental counting is indicated to calculate PPO FEV1 or DLCO values (PPO values = preoperative values × [1 – y/z]), where the preoperative values are taken as the best measured postbronchodilator value and the number of functional or unobstructed lung segments to be removed is y and the total number of functional segments is z. (b) ppoFEV1 or ppoDLCO cutoff values of 60% predicted values have been chosen based on indirect evidence and expert consensus opinion. (c) For patients with a positive high-risk cardiac evaluation deemed to be stable to proceed to surgery, we suggest performing both pulmonary function tests and cardiopulmonary exercise testing (CPET) for a more precise definition of risk. (d) Definition of risk is as follows: Low risk: The expected risk of mortality is below 1%. Major anatomic resections can be safely performed in this group. Moderate risk: Morbidity and mortality rates may vary according to the values of split lung functions, exercise tolerance, and extent of resection. Risks and benefits of the operation should be thoroughly discussed with the patient. High risk: The risk of mortality after standard major anatomic resections may be higher than 10%. Considerable risk of severe cardiopulmonary morbidity and residual functional loss is expected. Patients should be counseled about alternative surgical (minor resections or minimally invasive surgery) or nonsurgical options. m, meters; ppoDLCO, predicted postoperative diffusion capacity for carbon monoxide; ppoDLCO%, percent predicted postoperative diffusion capacity for carbon monoxide; ppoFEV1, predicted postoperative FEV1; ppoFEV1%, percent predicted postoperative FEV1; SCT, stair climb test; SWT, shuttle walk test; VO2max, maximal oxygen consumption. (Reproduced with permission from Brunelli A, Kim A, Berger K, et al. Physiologic evaluation of the patient with lung cancer being considered for resectional surgery: Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2013 May;143(5 Suppl):e166S-e190S.)
Pulmonary infections may present as a solitary nodule or cavitary lesion (necrotizing pneumonitis). VATS may be carried out to exclude malignancy and diagnose the infectious agent. Lung resection is also indicated for cavitary lesions that are refractory to antibiotic treatment, are associated with refractory empyema, or result in massive hemoptysis. Responsible organisms include both bacteria and fungi.
Bronchiectasis is a permanent dilation of bronchi. It is usually the end result of severe or recurrent inflammation and obstruction of bronchi. Causes include cigarette smoking; a variety of viruses, bacteria, nontuberculous mycobacteria, and fungi; as well as inhalation of toxic gases, aspiration of gastric acid, and defective mucociliary clearance (cystic fibrosis and disorders of ciliary dysfunction). Bronchial muscle and elastic tissue are typically replaced by very vascular fibrous tissue. The latter predisposes to bouts of hemoptysis. Pulmonary resection is usually indicated for massive hemoptysis when conservative measures have failed and the disease is localized. Patients with diffuse bronchiectasis have a chronic obstructive ventilatory defect.
1. Preoperative Management
The majority of patients undergoing pulmonary resections have underlying lung disease. It should be emphasized that smoking is a risk factor for both chronic obstructive pulmonary disease and coronary artery disease; both disorders commonly coexist in patients presenting for thoracotomy. Echocardiography is useful for assessing baseline cardiac function and may suggest evidence of cor pulmonale (right ventricular enlargement or hypertrophy) in patients with poor exercise tolerance. Stress echocardiography (exercise or dobutamine) may be useful in diagnosing coronary artery disease when indicated by suggestive signs and symptoms.
Patients with tumors should be queried regarding signs and symptoms of local extension of the tumor and paraneoplastic syndromes (see above). Preoperative chest radiographs and CT or MR images should be reviewed. Tracheal or bronchial deviation can make tracheal intubation and proper positioning of bronchial tubes much more difficult. Moreover, airway compression can lead to difficulty in ventilating the patient following induction of anesthesia. Pulmonary consolidation, atelectasis, and large pleural effusions predispose to hypoxemia. The location of any bullous cysts or abscesses should be noted.
Patients undergoing thoracic procedures are at increased risk of postoperative pulmonary and cardiac complications. Perioperative arrhythmias, particularly supraventricular tachycardias, are common and thought to result from surgical manipulations or distention of the right atrium following reduction of the pulmonary vascular bed. The incidence of arrhythmias increases with age and the amount of pulmonary resection.
2. Intraoperative Management
As with anesthesia for cardiac surgery, optimal preparation may help to prevent potentially catastrophic problems. Limited pulmonary reserve, anatomic abnormalities, or compromise of the airways, and the need for one-lung ventilation predispose these patients to the rapid onset of hypoxemia. A well-thought-out plan to deal with potential difficulties is necessary. Moreover, in addition to items for basic airway management, specialized and properly functioning equipment—such as multiple sizes of single- and double-lumen tubes, a flexible (pediatric) fiberoptic bronchoscope, a small-diameter “tube exchanger” of adequate length to accommodate a double lumen tube, a continuous positive airway pressure (CPAP) delivery system, and an anesthesia circuit adapter for administering bronchodilators—should be immediately available.
Patients undergoing open-lung resections (segmentectomy, lobectomy, and pneumonectomy) often receive postoperative thoracic epidural analgesia, unless there is a contraindication. However, patients are increasingly being treated with numerous antiplatelet and anticoagulant medications, which may preclude epidural catheter placement. Opioid-sparing, multimodal analgesia regimens, including paravertebral blocks, local injection of liposomal bupivacaine, and wound infusion catheters, are increasingly a part of enhanced recovery programs for thoracic surgery patients.
At least one large-bore (14- or 16-gauge) intravenous line is mandatory for all open thoracic surgical procedures. A blood warmer and a rapid infusion device are also desirable if extensive blood loss is anticipated.
Direct monitoring of arterial pressure is indicated for resections of large tumors (particularly those with mediastinal or chest wall extension), and any procedure performed in patients who have limited pulmonary reserve or significant cardiovascular disease. Central venous access (preferably on the side of the thoracotomy to avoid the risk of pneumothorax on the side that will be ventilated intraoperatively) with monitoring of central venous pressure (CVP) is commonly used for pneumonectomies and resections of large tumors; however, less invasive measures of cardiac output through use of thoracic bioimpedance, pulse contour analysis, or transpulmonary thermodilution provide better estimates of cardiac function and volume responsiveness (see Chapter 5). Pulmonary artery catheters are very rarely used. In patients with significant coronary artery disease or pulmonary hypertension, intraoperative diagnosis of hypovolemia or reduced right or left ventricular performance can be easily accomplished with transesophageal echocardiography.
The selection of an induction agent should be based on the patient’s preoperative status. All patients should receive adequate preoxygenation before induction. An adequate depth of anesthesia will help prevent reflex bronchospasm and exaggerated cardiovascular pressor responses to laryngoscopy. This may be accomplished by incremental doses of the induction agent, an opioid, or deepening the anesthesia with a volatile inhalation agent (the latter is particularly useful in patients with reactive airways). Moreover, volatile anesthetic agents may protect the lung from injury during one-lung ventilation.
Tracheal intubation with a single-lumen tracheal tube (or with a laryngeal mask airway [LMA]) may be necessary, if the surgeon performs diagnostic bronchoscopy (see below) prior to surgery. Once the bronchoscopy is completed, the single-lumen tracheal tube (or LMA) can be replaced with a double-lumen bronchial tube (see above). Controlled positive-pressure ventilation helps prevent atelectasis, paradoxical breathing, and mediastinal shift; it also allows control of the operative field to facilitate the surgery.
Following induction, intubation, and confirmation of correct tracheal or bronchial blocker position, additional venous access and monitoring may be obtained before the patient is positioned for surgery. Most lung resections are performed with the patient in the lateral decubitus position. Proper positioning avoids injuries and facilitates surgical exposure. The lower arm is flexed and the upper arm is extended in front of the head, pulling the scapula away from the operative field (Figure 25–11). Pillows are placed between the arms and legs, and an axillary (chest) roll is usually positioned just beneath the dependent axilla to reduce pressure on the inferior shoulder (it is assumed, but not proven, that the axillary roll helps protect the brachial plexus); care is taken to avoid pressure on the eyes and the dependent ear.
Proper positioning for a lateral thoracotomy. (Reproduced with permission from Gothard JWW, Branthwaite MA. Anesthesia for Thoracic Surgery. Oxford, UK: Blackwell; 1982.)
Maintenance of Anesthesia
All current anesthetic techniques have been successfully used for thoracic surgery, but the ideal techniques must provide the ability to administer high concentrations of inspired oxygen and all must permit rapid adjustments in anesthetic depth. Potent halogenated agents (isoflurane, sevoflurane, or desflurane) are often used in North American practice. Advantages of the halogenated agents versus total intravenous techniques include potent, dose-related bronchodilation and consistent depression of airway reflexes. Halogenated agents generally have minimal effects on HPV in doses less than 1 minimum alveolar concentration (MAC). Advantages of opioids include (1) generally minimal hemodynamic effects; (2) depression of airway reflexes; and (3) residual postoperative analgesia. If epidural or intrathecal opioids are to be used for postoperative analgesia, intravenous opioids should be minimized during surgery to prevent excessive postoperative respiratory depression. Maintenance of neuromuscular blockade with a nondepolarizing neuromuscular blocker (NMB) during surgery facilitates rib spreading as well as anesthetic management. Excessive fluid administration in thoracic surgical patients has been associated with acute lung injury in the postoperative period. Excessive fluid administration in the lateral decubitus position may promote a “lower lung syndrome” (ie, gravity-dependent transudation of fluid into the dependent lung). The latter increases intrapulmonary shunting and promotes hypoxemia, particularly during one-lung ventilation. While we manage lung resections with a relative fluid restriction, we acknowledge that definitive studies on an ideal goal-directed fluid management strategy are lacking.
The collapsed lung may be prone to acute lung injury due to surgical retraction during the procedure and possible ischemia–reperfusion injury. During lung resections, the bronchus (or remaining lung tissue) is usually divided with an automated stapling device. The bronchial stump is then tested for an air leak under water by transiently sustaining 30 cm of positive pressure to the airway. Prior to completion of chest closure, all remaining lung segments should be fully expanded manually under direct vision. Controlled mechanical ventilation is then resumed and continued until thoracostomy tubes are connected to suction.
Management of One-Lung Ventilation
Although still an intraoperative problem, hypoxemia has become less frequent due to better lung isolation methods, ventilation techniques, and the use of anesthetic agents with less detrimental effects on hypoxic pulmonary vasoconstriction. Attention has currently shifted toward avoidance of acute lung injury (ALI). Fortunately, ALI occurs infrequently, with an incidence of 2.5% of all lung resections combined, and an incidence of 7.9% after pneumonectomy. However, when it occurs, ALI is associated with a risk of mortality or major morbidity of about 40%.
Based on current data, it seems that protective lung ventilation strategies may minimize the risk of ALI after lung resection. This ventilatory strategy includes the use of lower tidal volumes (<6 mL/kg), lower FiO2 (50–80%) and lower ventilatory pressures (plateau pressure <25 cm H2O; peak airway pressure <35 cm H2O) through the use of pressure-controlled ventilation. Permissive hypercapnia is reasonable for those rare patients with elevated CO2 tensions despite adequate oxygen saturation and a reasonable minute ventilation. The use of tidal volumes less than 3 mL/kg per lung may lead to lung derecruitment, atelectasis, and hypoxemia. Lung derecruitment may be avoided by application of PEEP and recruitment maneuvers. Although the management of one-lung ventilation has long included the use of 100% oxygen, evidence for oxygen toxicity has accumulated both experimentally and clinically. Although there is no unequivocal evidence that one mode of ventilation may be more beneficial than the other, pressure-controlled ventilation may diminish the risk of barotrauma by limiting peak and plateau airway pressures, and the flow pattern results in a more homogenous distribution of the tidal volume and reduced dead space ventilation.
At the end of the procedure, the operative lung is inflated gradually to a peak inspiratory pressure of less than 30 cm H2O to prevent disruption of the staple line. During reinflation of the operative lung, it may be helpful to clamp the lumen serving the dependent lung to limit overdistention.
Periodic arterial blood gas analysis is helpful to ensure adequate ventilation. End-tidal CO2 measurement is useful as a trend monitor but may not be accurate due to increased dead-space and an unpredictable gradient between the arterial and end-tidal CO2 partial pressure.
Hypoxemia during one-lung anesthesia requires one or more of the following interventions:
Adequate position of the bronchial tube (or bronchial blocker) must be confirmed, as its position relative to the carina can change as a result of surgical manipulations or traction; repeat fiberoptic bronchoscopy through the tracheal lumen can quickly detect this problem. Both lumens of the tube should also be suctioned to exclude excessive secretions or obstruction as a factor.
Increase FiO2 to 1.0.
Recruitment maneuvers on the dependent, ventilated lung may eliminate atelectasis and improve shunt.
Ensure that there is sufficient (but not excessive) PEEP to the dependent, nonoperative lung to eliminate atelectasis.
CPAP or blow-by oxygen to the operative lung will decrease shunting and improve oxygenation. However, uncontrolled inflation of the operative lung during VATS will make identification and visualization of the lung structures difficult for the surgeon; therefore, such maneuvers should be applied carefully and cautiously.
Two-lung ventilation should be instituted for severe hypoxemia. If possible, pulmonary artery clamp can also be placed during pneumonectomy to eliminate shunt.
In patients with chronic obstructive lung disease, one should always be suspicious of pneumothorax on the dependent, ventilated side as a cause of severe hypoxemia. This complication requires immediate detection and treatment by aborting the surgical procedure, reexpanding the operative lung, and immediately inserting a chest tube in the contralateral chest.
If other causes and maneuvers have failed to improve oxygen saturation and one-lung anesthesia is required to complete the anesthetic, one can discontinue all medications known to inhibit HPV (inhalation anesthetics, vasodilators, β-agonists, etc) in favor of alternative drugs and techniques (eg, total intravenous anesthesia, labetalol, etc).
Alternatives to One-Lung Ventilation
Ventilation can be stopped for short periods if 100% oxygen is insufflated at a rate greater than oxygen consumption (apneic oxygenation) into an unobstructed tracheal tube. Adequate oxygenation can often be maintained for prolonged periods, but progressive respiratory acidosis limits the use of this technique to 10 to 20 min in most patients. Arterial PCO2 rises 6 mm Hg in the first minute, followed by a rise of 3 to 4 mm Hg during each subsequent minute.
High-frequency positive-pressure ventilation and high-frequency jet ventilation have been used during thoracic procedures as alternatives to one-lung ventilation. A standard tracheal tube may be used with either technique. Small tidal volumes (<2 mL/kg) allow decreased lung excursion, which may facilitate the surgery but still allow ventilation of both lungs. Unfortunately, mediastinal “bounce”—a to-and-fro movement—often interferes with the surgery.
3. Postoperative Management
Most patients are extubated shortly after surgery to decrease the risk of pulmonary barotrauma (particularly “blowout” [rupture] of the bronchial suture line). All patients (and especially those with marginal pulmonary reserve) should remain intubated until standard extubation criteria are met. When postoperative mechanical ventilation will be required, double-lumen tubes should be replaced with a regular single-lumen tube at the end of surgery. We routinely use a catheter guide (“tube exchanger”) for this purpose and always use this technique when the original laryngoscopy was difficult.
Patients are observed in the postanesthesia care unit, and, in most instances, at least overnight in a monitored or intensive care unit. Atelectasis and shallow breathing (“splinting”) from incisional pain commonly lead to hypoxemia and respiratory acidosis. Gravity-dependent transudation of fluid into the intraoperative dependent lung may also be contributory. Reexpansion edema of the collapsed nondependent lung can also occur.
Postoperative hemorrhage complicates about 3% of thoracotomies and may be associated with up to 20% mortality. Signs of hemorrhage include increased chest tube drainage (>200 mL/h), hypotension, tachycardia, and a falling hematocrit. Postoperative supraventricular tachyarrhythmias are common and usually require immediate treatment. Routine postoperative care should include semiupright (>30°) positioning, supplemental oxygen (40–50%), incentive spirometry, electrocardiographic and hemodynamic monitoring, a postoperative chest radiograph (to confirm proper position of all thoracostomy tube drains and central lines and to confirm expansion of both lung fields), and adequate analgesia.
The importance of adequate pain management in the thoracic surgical patient cannot be overstated. Inadequate pain control in these high-risk patients will result in splinting, poor respiratory effort, and the inability to cough and clear secretions, with an end result of airway closure, atelectasis, shunting, and hypoxemia. Irrespective of the modality used, there must be a comprehensive plan for pain management.
A balance between comfort and respiratory depression in patients with marginal lung function is difficult to achieve with parenteral opioids alone. Patients who have undergone thoracotomy clearly benefit from the use of other techniques (described later) that may reduce the need for parenteral opioids. If parenteral opioids are used alone, they are best administered via a patient-controlled analgesia device.
In the absence of an epidural catheter, intercostal or paravertebral nerve blocks with long-acting local anesthetics may facilitate extubation and contribute to postoperative analgesia, but have a limited duration of action, so additional means of pain management must be employed. Alternatives to epidural, intercostal, or paravertebral techniques include infusion of local anesthetic through a catheter placed in the surgical wound during closure or injection of liposomal bupivacaine into the wound, which will markedly reduce the requirement for parenteral opioids and improve the overall quality of analgesia relative to parenteral opioids alone.
Epidural analgesia provides excellent pain relief and continuous therapy and avoids side effects associated with administration of systemic opioids. On the other hand, epidural techniques require around-the-clock attention from the acute pain team for the duration of the infusion and subject the patient to the long list of epidural-related side effects and complications Most practitioners use a combination of opioid (fentanyl, morphine, hydromorphone) and local anesthetic (bupivacaine or ropivacaine), with the epidural catheter placed at a thoracic level. Gabapentin and low-dose ketamine and lidocaine intravenous infusions have all been employed as a part of multimodal analgesia regimens following thoracotomy. Oral or intravenous acetaminophen and oral or intravenous nonsteroidal antiinflammatory agents are likewise routinely used in combination with other modalities to reduce or eliminate opioid use for postoperative analgesia.
Postoperative complications following thoracotomy are relatively common, but fortunately most are minor and resolve uneventfully. Blood clots and thick secretions may obstruct the airways and result in atelectasis; suctioning may be necessary. Therapeutic bronchoscopy should be considered for persistent atelectasis, particularly when associated with thick secretions. Air leaks from the operative hemithorax are common following segmental and lobar resections. Most air leaks stop after a few days. Bronchopleural fistula presents as a sudden large air leak from the chest tube that may be associated with an increasing pneumothorax and partial lung collapse. When it occurs within the first 24 to 72 h, it is usually the result of inadequate surgical closure of the bronchial stump. Delayed presentation is usually due to necrosis of the suture line associated with inadequate blood flow or infection.
Some complications are rare, but deserve special consideration because they can be life-threatening and require immediate exploratory thoracotomy. Postoperative bleeding is reviewed above. Torsion of a lobe or segment can occur as the remaining lung on the operative side expands to occupy the hemithorax. The torsion usually occludes the pulmonary vein to that part of the lung, causing venous outflow obstruction. Hemoptysis and infarction can rapidly follow. The diagnosis is suggested by an enlarging homogeneous density on the chest radiograph and a closed lobar orifice on bronchoscopy. Acute herniation of the heart into the operative hemithorax can occur through the pericardial defect that may remain following a pneumonectomy. A large pressure differential between the two hemithoraces is thought to trigger this catastrophic event. Cardiac herniation into the right hemithorax results in sudden severe hypotension with an elevated CVP because of torsion of the central veins. Cardiac herniation into the left hemithorax following left pneumonectomy results in sudden compression of the myocardium, resulting in hypotension, ischemia, and infarction. A chest radiograph shows a shift of the cardiac shadow into the operative hemithorax.
Extensive mediastinal dissections can injure the phrenic, vagus, and left recurrent laryngeal nerves. Postoperative phrenic nerve palsy presents as elevation of the ipsilateral hemidiaphragm together with difficulty in weaning the patient from the ventilator. Large chest wall resections may include part of the diaphragm, causing a similar problem, in addition to a flail chest. If an epidural catheter has been placed, any loss of motor function or unexplained back pain should immediately trigger imaging to rule out epidural hematoma.
SPECIAL CONSIDERATIONS FOR PATIENTS UNDERGOING LUNG RESECTION
Massive Pulmonary Hemorrhage
Massive hemoptysis is usually defined as more than 500 to 600 mL of blood loss from the tracheobronchial tree within 24 h. The etiology is usually tuberculosis, bronchiectasis, a neoplasm, a complication of transbronchial or transthoracic biopsies, or (more commonly in the past) pulmonary artery rupture from overinflation of a pulmonary artery catheter balloon. Emergency surgical management with lung resection is reserved for potentially lethal massive hemoptysis. In most cases, surgery is carried out on an urgent rather than on a true emergent basis whenever possible; even then, operative mortality may exceed 20% (compared with >50% for medical management). Embolization of involved bronchial arteries may be attempted. The most common cause of death is asphyxia secondary to blood or clot in the airway. Patients may be brought to the operating room for rigid bronchoscopy when localization is not possible with fiberoptic flexible bronchoscopy. A bronchial blocker or Fogarty catheter (see earlier discussion) may be placed to tamponade the bleeding, or laser coagulation may be attempted.
Multiple large-bore intravenous catheters should be placed. Sedating drugs should not be given to awake, nonintubated, spontaneously ventilating patients because they are usually already hypoxic; 100% oxygen should be given continuously. If the patient is already intubated and has bronchial blockers in place, sedation is helpful to prevent coughing. The bronchial blocker should be left in position until the lung is resected. When the patient is not intubated, a rapid sequence induction (ketamine or etomidate with succinylcholine) is used. Patients usually swallow a large amount of blood and must be considered to have a full stomach. A large double-lumen bronchial tube is ideal for protecting the normal lung from blood and for suctioning each lung separately. If any difficulty is encountered in placing the double-lumen tube, or its relatively small lumens occlude easily, a large (>8.0-mm inner diameter) single-lumen tube may be used with a bronchial blocker to provide lung isolation.
Pulmonary cysts or bullae may be congenital or acquired as a result of emphysema. Large bullae can impair ventilation by compressing the surrounding lung. These air cavities often behave as if they have a one-way valve, predisposing them to progressively enlarge. Lung resection may be undertaken for progressive dyspnea or recurrent pneumothorax. The greatest risk of anesthesia is rupture of the air cavity during positive-pressure ventilation, resulting in tension pneumothorax; the latter may occur on either side prior to thoracotomy or on the nonoperative side during the lung resection. Induction of anesthesia with maintenance of spontaneous ventilation is desirable until the side with the cyst or bullae is isolated with a double-lumen tube, or until a chest tube is placed; most patients have a large increase in dead space, so assisted ventilation is necessary to avoid excessive hypercarbia. Nitrous oxide is contraindicated in patients with cysts or bullae because it can expand the air space and cause rupture. The latter may be signaled by sudden hypotension, bronchospasm, or an abrupt rise in peak inflation pressure and requires immediate placement of a chest tube.
Lung abscesses result from primary pulmonary infections, obstructing pulmonary neoplasms (see earlier discussion), or, rarely, hematogenous spread of systemic infections. The two lungs should be isolated to prevent contamination of the healthy lung. A rapid-sequence intravenous induction with tracheal intubation with a double-lumen tube is generally recommended, with the affected lung in a dependent position. As soon as the double-lumen tube is placed, both bronchial and tracheal cuffs should be inflated. The bronchial cuff should make a tight seal before the patient is turned into the lateral decubitus position, with the diseased lung in a nondependent position. The diseased lung should be frequently suctioned during the procedure to decrease the likelihood of contaminating the healthy lung.
Bronchopleural fistulas occur following lung resection (usually pneumonectomy), rupture of a pulmonary abscess into a pleural cavity, pulmonary barotrauma, or spontaneous rupture of bullae. The majority of patients are treated (and cured) conservatively; patients come to surgery when chest tube drainage has failed. Anesthetic management may be complicated by the inability to effectively ventilate the patient with positive pressure because of a large air leak, the potential for a tension pneumothorax, and the risk of contaminating the other lung if an empyema is present. The empyema is usually drained, prior to closure of the fistula.
A correctly placed double-lumen tube greatly simplifies anesthetic management by isolating the fistula and allowing one-lung ventilation to the normal lung. The patient should be extubated as soon as possible after the repair.