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Formulating an anesthetic plan begins with a thorough evaluation of the patient. The starting point for this evaluation is the complete history and physical examination. In October 2001, the ASA published a Practice Advisory for Preanesthesia Evaluation.2 This advisory provides guidelines regarding minimum requirements for the history, physical examination, testing, and timing of the preoperative assessment. Throughout this chapter we invoke principles of this advisory when specific issues relate to the healthy patient.
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In the context of the healthy patient, the purpose of the history and physical examination is 4-fold:
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- To fully elucidate the nature of the proposed operation and the problem for which the operation is being performed
- To ascertain the presence or absence of comorbidities or conditions that can heighten perioperative risk (to verify that the patient is, in fact, healthy)
- To ascertain whether the patient has a history of perioperative complications
- To educate the patient and then devise a plan that takes into account his or her preferences
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The preoperative history and physical examination is typically a joint effort between the surgeon and the anesthesiologist. Following are specific goals and methods for the conduct of such a preoperative history and physical examination, which are well summarized in the ASA Practice Advisory for Preoperative Evaluation.2
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Type of Surgical Disease and Planned Surgical Procedure
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In planning an anesthetic, the primary goals of the anesthesiologist are patient safety and satisfaction, and the provision of ideal operating conditions. The starting point for development of this plan is a thorough understanding of the surgical problem. The physical problem that necessitates operation can often have a significant impact on the provision of safe anesthesia. For example, patients presenting for surgical correction of temporomandibular joint disease may have significant issues with airway management. In addition, operations that achieve the same end point are often performed using different approaches and techniques. For example, otherwise healthy men may undergo prostatectomy using either a laparoscopic or an open approach. Surgical technique alone can alter the anesthetic choice.
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Much information regarding the surgical condition and planned procedure is obtained from the surgical history and physical examination, which is performed by the surgeon or a clinical "extender" of the surgeon (physician assistant, resident, nurse practitioner). It is critical that effective communication be maintained between members of the surgical and anesthesia teams to develop an optimal anesthetic plan. Computerized medical records aid greatly in achieving this goal. Most healthy patients do not require an anesthetic evaluation in advance of their operation. However, the surgical team must recognize when an advance visit with an anesthesiologist is appropriate, ensuring that such visits occur when indicated. To this end, preoperative anesthesia assessment clinics have evolved, along with screening criteria to aid surgical teams in deciding who needs this consultation. Preoperative clinics are discussed in subsequent sections.
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"Healthy" patients are considered to be ASA physical status classification I and II.3 By definition, these patients either have no disease or have minor disease processes that are well controlled and cause no physical limitation. Menke and colleagues demonstrated in 1993 that ASA classification independently predicted overall perioperative risk and that this risk was low in ASA I and II patients.4 Similar findings have been verified by other authors, and the classification is still in common use5 (Table 7-1).
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After the surgical condition and the specifics of the operation have been clarified, the next goal of the anesthesia provider is verification that the patient is, in fact, free of disease. This constitutes the bulk of the preoperative history and physical in healthy patients, and it is a joint venture between surgical and anesthetic teams. A comprehensive review of systems is the method of choice for this purpose, which is generally obtained by a member of the surgical team. It is good practice for anesthesiologists to verify and further explore these findings when pertinent for provision of safe anesthesia. Assessment tools and guidelines are helpful for this purpose. The American College of Cardiology/American Heart Association guidelines are useful for patients with suspected cardiovascular disease.6 Similar guidelines exist for evaluation of the respiratory system. The review of systems is also a valuable tool for careful screening of other organ systems including the coagulation system.
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Occasionally, findings from the review of systems (eg, history of gastroesophageal reflux disease, neuropsychiatric disorders, clotting abnormalities) can alter the anesthetic plan in otherwise "healthy" patients. In addition, medical disease (hypertension, diabetes, coronary artery disease, asthma, obstructive pulmonary disease, etc) is occasionally diagnosed in surgical patients previously assumed to be "healthy"; such patients may require further evaluation and treatment before operation. Communication with the referring surgeon is important because this evaluation and treatment can delay the planned procedure.
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Identifying Potential Anesthetic Complications
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Even patients who lack comorbidities may have a spectrum of potential anesthetic complications (Table 7-2).
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In healthy patients, a primary determinant of the success of an anesthetic is avoidance of these complications. Hence a major focus of the anesthesiologist's medical history in healthy patients is identification of potential complications. Patients may have a personal or a family history of complications, and when such a history is elicited, the patient should always be asked to provide a thorough account of the events and their consequences. In addition, it is important to obtain the medical records if possible. Once the complication has been identified and elucidated, the anesthetic plan should be altered to minimize the risk of that complication recurring. This plan should be clearly documented and the patient informed that steps have been taken for prevention. Next is a discussion of common anesthetic complications and steps that can be taken to minimize or eliminate them.
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Postoperative Nausea and Vomiting
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The most common complication associated with anesthesia is postoperative nausea and vomiting (PONV). This complication is highly distressing yet amenable to prevention.7 Recognition of this problem, followed by alteration in the anesthetic plan, has resulted in marked improvements in patient outcome and satisfaction.8 Untreated nausea occurs in as many as 40% of patients undergoing general anesthesia.9 Golembiewski's excellent review of this subject outlines patient characteristics that heighten risk (Table 7-3).
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When these characteristics, or a strong history of PONV, are encountered, the anesthetic plan should include use of anesthetics with less likelihood of causing the disorder (eg, total intravenous anesthesia [TIVA] with propofol).8 In addition, strong consideration should be given to prophylactic use of antiemetic drugs that are highly effective.8 The PONV algorithms used at the University of Michigan are illustrated in Figs. 7-1 and 7-2. Note that, after induction, droperidol (0.625 mg intravenously [IV]) is included as a primary prophylactic agent in high-risk patients. The US Food and Drug Administration (FDA) has placed a "black box" warning on droperidol, given its propensity to prolong the QT interval, which may be associated with serious cardiac rhythm disturbances.10 Subsequent investigations have challenged this measure, citing remarkable safety at typical dosages used in modern anesthetic practice.11 It is therefore controversial whether there should be a limit on the use of droperidol, given its track record of safety and efficacy.
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Finally, anxiety as a possible causative factor can often be effectively addressed by a frank acknowledgment to the patient that the problem has been recognized and that steps are in place for prevention.
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History of Difficult Airway
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When difficult airway management is known or suspected, a thorough account of the findings and management must be sought from both patient and old medical records. "Difficult airway" usually means that airway anatomy was such that standard laryngoscopy was either difficult or impossible. When this is identified in the preoperative history, subsequent management via an awake technique should be considered. Patients with difficult airways are often otherwise healthy, but this alone presents significant anesthetic risk. The prospect of awake airway management usually provokes anxiety. The possibility of awake intubation is best communicated well in advance of the operative date. Explanation of the plan in a slow, reassuring fashion serves to inform and prepare the patient and thus minimize anxiety on the day of operation. A brief overview of airway assessment follows in the physical examination section, but a full review is considered in greater detail in Chapter 36.
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Malignant Hyperthermia
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A rare anesthetic complication that must be recognized and planned for is malignant hyperthermia (MH). Estimates of the incidence of this complication range from 1 in 20000 to 1 in 70000.17 Recognition, prevention, and treatment of MH have been a major success story in anesthesia. (See Chapter 87 for an in-depth review of MH; it is considered only briefly here, but detailed knowledge is required by all anesthesia practitioners.) Patients with potential MH risk must be seen well in advance of operation so that a complete clinical history is obtained and a plan of care can be devised and communicated to the patient and other providers.
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Nearly uniformly fatal in the past, this disorder now has a mortality rate of less than 10%.19 When patients present with either a personal or family history of the disorder, the anesthesiologist is confronted with decisions regarding testing and perioperative management. Muscle biopsy testing for the disorder is available at a diminishing number of centers and is costly, time consuming, and not completely reliable.20 Although genetic testing appears promising, it is not widely available currently. Many anesthesiologists therefore proceed with the assumption that the patient is at risk and provide a nontriggering anesthetic. In some cases, regional anesthesia or conscious sedation may be appropriate. In others where these are not appropriate, a nontriggering general anesthetic is provided. Bryson et al demonstrated recently that even general anesthesia could be safely provided to MH susceptible outpatients, as long as "triggers" were avoided.21 "Nontriggering" in this sense means avoidance of the only 2 reliable MH triggers: succinylcholine and potent inhaled anesthetics. This is typically accomplished with TIVA (see Chapter 43), which includes propofol, nondepolarizing neuromuscular blocking agents, and opiates. A minimum of 4 hours of observation are recommended following an uneventful anesthetic.22
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Pseudocholinesterase Deficiency
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Pseudocholinesterase (butyrylcholinesterase) is a plasma enzyme with no known physiologic function. Deficiency of this enzyme is attributable to alterations in the gene that codes for it. In 2003 Yen and colleagues estimated the incidence of homozygous (affected) individuals to be approximately 1 in 1800.23 Deficiency is usually identified when an anesthetized patient has prolonged recovery from the depolarizing neuromuscular blocking agent succinylcholine. Suspicion of this deficiency first arose in 1953 when Nilsson gave a patient succinylcholine, who then failed to resume spontaneous ventilation after completion of a short operation,24 hence the colloquial name "suxamethonium apnea." Mivacurium, a short-acting nondepolarizing neuromuscular blocking agent, has also been shown to depend on this enzyme for elimination.25 Despite being far more common than its inherited counterpart MH, pseudocholinesterase deficiency poses far less danger to patients. In addition, testing for the disorder is far simpler and more widely available than that for MH. Once identified, safe management entails ventilatory support combined with sedation until the drug is eliminated via the kidney (after several hours in homozygous recessive patients). Identification of this condition in advance allows for alteration of the anesthetic plan so that use of these drugs can be avoided. (More extensive review of MH is provided in Chapter 87.)
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There has been growing public concern about intraoperative awareness and so-called awake paralysis, leading to increased anxiety in patients undergoing general anesthesia. Unfortunately, the true incidence of intraoperative awareness under general anesthesia, reported to range from 0.2% to 1.0%, is probably underestimated15 because not all patients who are aware in the operating room remember the fact afterward. This can be a particularly bothersome experience for many patients, and lasting adverse sequelae are common.26 Domino and colleagues, using analysis of litigation records, identified awareness as a common root cause for legal action against anesthesiologists.27
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As with other complications, a thorough account of the events from both the patient and their records should be sought. Occasionally, patients misinterpret the goals of conscious sedation and label this as intraoperative awareness. It is important to clarify this distinction to patients preoperatively, so that expectations are realistic. In light of the recent focus on intraoperative awareness, the Bispectral Index Sensor (BIS) monitor has evolved.28 Although use of BIS monitoring may reduce the incidence of awareness, recent reports by Mychaskiw and Rampersad cast doubt on this technology. Both demonstrated awareness despite BIS values that were maintained in the "anesthetized" (low value) range.29,30 Use of this device is reviewed more thoroughly in the monitoring section that follows. Whenever strong suspicion of awareness under general anesthesia exists, plans must be made to alter the anesthetic to prevent recurrence. In his concise review, Kazanjian outlines several methods to reduce the incidence of awareness and provides steps to respond to this complication31 (Table 7-4).
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Recent ASA guidelines on intraoperative awareness and brain function monitoring also provide clinicians with useful information for evaluation and treatment plans to prevent this worrisome complication.32 These include careful preoperative evaluation because certain patient features such as drug resistance may be predictive.27 In addition, various types of surgery (cardiac, obstetric, trauma) as well as anesthetic techniques may place patients at particular risk.33 The ASA recognizes that processed electroencephalogram (EEG) devices, which assign a numeric value to a patient's level of sedation, are marketed to minimize the risk of intraoperative awareness, and they state, "We are interested in following their continued evolution and in conducting further research in this area." Hence the ASA concludes, "Brain function monitors are an option to be used when the anesthesiologist deems it appropriate, just as he or she makes choices about specific drugs, dosages, warming devices, and other types of monitors depending on the individual patient."
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Additional Complications
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Additional perioperative complications exist, and recognition of these complications is critical in preventing their reoccurrence. In a 2004 review, Mertes and Laxenaire found that serious drug reactions are surprisingly common in anesthetic practice,34 and in many cases alternative drugs can be selected (antibiotics, local anesthetics, opiates, others) or avoided altogether (succinylcholine in the case of pseudocholinesterase deficiency). Pulmonary aspiration of acidic gastric contents has the potential to complicate any anesthetic, even in otherwise healthy patients. Gastroesophageal reflux disease (GERD) and a full stomach are potential risk factors in healthy patients. If general anesthesia is being contemplated when aspiration risk exists, the anesthetic plan is altered in two ways:
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Prophylactic antiaspiration measures should be taken (gastric motility drugs, pharmacologic stomach acid reduction, and rapid sequence induction).
Laryngeal mask airway should not be used.
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Finally, even in the absence of anticipated risks or complications, many patients simply have high anxiety levels. It is appropriate for these patients to visit with an anesthesiologist in advance of their operative date to address and ameliorate this anxiety. There is even evidence to suggest that nonpharmacologic strategies, such as psychological support or soothing music, may play a significant role in treating both pain and anxiety.35
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A thorough drug history must be obtained from all patients undergoing elective surgery. Even healthy patients may take a variety of prescription and nonprescription medications. All medications must be recorded, and reasons for their use must be assessed. Patients must also be questioned carefully about drug allergies and intolerances, and clear a distinction between the two must be documented in the medical record. When obtaining a drug history, it is important to ask that all regularly ingested exogenous compounds, including over-the-counter medications, herbal preparations, and vitamin supplements, be reported. Several of these compounds have been associated with serious perioperative complications and drug interactions.36 Planning for a safe anesthetic usually entails discontinuation of many of these preparations well in advance of the planned procedure, which the ASA recommends.37 Table 7-5 contains a list of common herbal preparations and adverse interactions that have been associated with them.
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Finally, it is important to determine whether patients are using illicit drugs because many of these drugs have also been associated with anesthetic complications.38 Patients must be advised to abstain from all forms of illicit drugs well in advance of an elective procedure.
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The purpose of the physical examination in healthy surgical patients is to corroborate and augment findings from the medical history. Thus the first goal of the physical examination is to rule out disease. The second goal is to identify physical features that may make provision of anesthesia difficult or potentially lead to complications. In actuality, the physical examination begins while the history is being obtained. This direct interaction is a good time to observe the gross physical appearance and mental status of the patient. It is also a good time to look for obvious skin (jaundice, cyanosis, signs of dehydration, rashes) or musculoskeletal abnormalities (especially spine deformities) that may give clues to underlying pathologic conditions. This examination begins with a set of vital signs, including room-air oxygen saturation. Even if previously documented from the surgical history and physical examination, it is important for anesthesiologists to perform baseline examinations of both the cardiovascular and respiratory systems before elective surgery. Finally, a meticulous examination of the airway must be performed to assess for features that predict difficult airway management if the need for general anesthesia should arise.
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Even in the presence of a negative medical history, abnormal vital signs can be an important first clue to the presence of underlying disease. In fact, potential medical risks such as hypertension and thyroid disease are occasionally diagnosed during the preoperative history and physical examination. The so-called white coat phenomenon is responsible for hypertension in many preoperative patients.39 Significant elevations in blood pressure or heart rate, however, especially on repeated measures, warrant further investigation and possible therapy. Rather than simply asking, height and weight should be accurately measured. Arterial blood pressure should be determined either via sphygmomanometry or oscillometry, using an appropriate-size cuff. It is desirable to obtain blood pressure in both arms. We feel strongly that baseline room-air oxygen saturation should be measured via pulse oximetry in every patient.
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Cardiorespiratory Examination
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Examination of cardiovascular and respiratory systems also begins with observation of the patient, which is conveniently accomplished while obtaining the history. Findings such as labored breathing, wheezing, coughing, clubbing of the nails, jugular venous distention, and cyanosis are typically identified while simply conversing with a patient. Obviously, these are signs of potentially serious pathologic conditions and should be investigated further by more in-depth examination. Physical examination of the cardiovascular system aids in ruling out hypertension, valvular heart disease, and heart failure. Palpation and auscultation of the heart should be performed to identify heaves, rubs, extra heart sounds, and murmurs. Peripheral pulses should be assessed for both quality and magnitude. The chest should be examined for wheezes, rales, and rhonchi.
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Regardless of the anesthetic chosen for a particular operation, it is important that careful examination of the airway be performed in every patient. Although much of the remainder of the physical examination represents a combined or even redundant effort between anesthesiologists, surgeons, and internists, a complete airway evaluation is generally not the purview of other medical specialists. The anesthesiologist is solely responsible for securing the airway and establishing ventilation. Difficulty with these processes may place the patient in great peril. This is borne out by the fact that airway management problems account for a relatively large proportion of anesthesia-related morbidity and mortality. In ASA closed claims analyses, both Caplan et al and Domino et al demonstrated that loss of the airway is a frequent cause of litigation associated with severe injury or death.40,41 If a patient is known to have a difficult airway, alternative management plans are available (eg, awake fiberoptic intubation). Identifying patients with difficult airways, followed by these alternative induction techniques, should eliminate the "unconscious patient, can't intubate, can't ventilate" scenario. It is therefore a major goal of anesthesiologists to predict the potentially difficult airway in advance of anesthetic induction.
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Tests to Predict Difficult Laryngoscopy
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Preoperative airway assessment, with the aim of detecting and thus anticipating the difficult airway, has evolved over the years. Currently, a number of strategies exist for systematic evaluation of the airway, and various guidelines endorse the use of such strategies.48 Key elements of the airway examination include neck anatomy, neck flexion and extension, thyromental distance, mouth opening, Mallampati score, and, more recently, jaw protrusion and the presence of a beard. Excellent reviews are available on the various tests and strategies commonly used by anesthesiologists to assess physical and symptomatic features that may predict difficult laryngoscopy49 (Table 7-6).
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Mandibular displacement (upper lip bite test) was correlated with the difficulty of laryngoscopy and may have clinical utility.43 Although these various tests and maneuvers are simple to perform, they have questionable sensitivity and specificity, and hence unreliable predictive value.14 This explains the occasional finding of the "unanticipated difficult airway" after seemingly reliable testing preoperatively predicted otherwise.14 Typically, the goal of these tests is to correlate symptomatic (eg, sleep apnea) and anatomic patient features with difficult laryngoscopy.49
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Difficult Mask Ventilation
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Although successful laryngoscopy followed by endotracheal intubation constitutes definitive management for an unconscious and apneic patient, ventilation by mask can be a lifesaving maneuver. Despite this fact, the historical precedent for investigators with an interest in predicting the difficult airway has been to focus on laryngoscopy alone. Given the potentially lifesaving importance of mask ventilation, however, investigators have begun to stress both laryngoscopy and mask ventilation in their predictive strategies. Langeron and colleagues, in 2000, estimated the incidence of difficult mask ventilation and identified several predictive physical features: history of snoring, body mass index (BMI) higher than 26, lack of teeth, age older than 55 years, and beard.42 In 2004 Han et al devised a scale for categorizing the difficulty of mask ventilation. This 4-point scale elaborates on the work by Langeron, who only noted difficult and impossible ventilation. In contrast, the Han scale describes four degrees of assessment of ventilation, similar to scales used for laryngoscopy (Table 7-7).
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Han et al found an incidence of difficult mask ventilation of 1.5% in the 3000 patients they studied.50 More recently, a study of more than 41,000 patients confirmed the incidence of difficult ventilation to be approximately 1.5% and that the incidence of impossible ventilation was 0.5%.51 This large study by Kheterpal et al found 6 independent predictors (4 of Langeron's) of difficult mask ventilation: history of snoring, age older than 58 years, BMI higher than 30, Mallampati class III or IV, limited jaw protrusion, and the presence of a beard (Table 7-8).
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Of these, the only modifiable risk factor is the presence of a beard. This suggests that anesthesiologists should consider recommending that patients shave prior to elective procedures if they possess other risk factors for difficult mask ventilation. Table 7-9 illustrates the standard preoperative airway features that we assess and record via electronic data entry at the University of Michigan.
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Anticipated Difficult Airway Strategy
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When a potential difficult airway is identified, it is the anesthesiologist's responsibility to develop a management strategy, in the event that general anesthesia becomes necessary. When a truly difficult airway is known or strongly suspected, and general anesthesia is necessary, the usual management plan entails placement of an oral or nasal endotracheal tube while the patient is awake and spontaneously breathing. Techniques for awake endotracheal intubation are reviewed in Chapter 36. Several important steps in planning and patient preparation, however, are worth mentioning.
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The very thought of a potential airway problem can be anxiety provoking. The source of this anxiety often stems from patients' perception that theirs is a rare problem that places them in danger. To allay this anxiety, it is helpful to have a frank discussion with patients to fully inform them about the nature of the problem, and the rationale and plan for safely dealing with it. Patients are reassured knowing that the difficult airway is relatively common and that appropriate management poses no untoward danger. Careful anxiolytic sedation is appropriate preoperatively, to the extent that airway compromise is avoided. Antisialagogue premedication (typically glycopyrrolate 0.4-0.6 mg IV) aids greatly in the ability to anesthetize airway mucosa (typically with 2%-4% lidocaine). Profound topical anesthesias of upper airway mucosa, combined with judicious sedation, are the key elements in conducting a safe, effective, and comfortable awake intubation.
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Special Preoperative Considerations
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Preoperative Anesthesia Assessment Clinics
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Currently, the vast majority of patients presenting for elective surgery present to the hospital on the day of their procedure. Fortunately, most healthy patients can be seen and assessed by the anesthesia team immediately before their operation. The ASA Practice Advisory on Preanesthesia Evaluation recommends that timing of the preoperative evaluation be based not only on the health of the patient but also the invasiveness of the surgical procedure.52 They recommend that all patients undergoing highly invasive surgical procedures be seen before the day of surgery. These patients require evaluation, counseling, and possibly therapy in advance of their surgical date. An appropriate and convenient place to coordinate this workup is the preoperative anesthesia assessment clinic (PAC). To derive the most benefit from PACs, surgeons need to use them discriminately. We find it helpful to provide screening criteria to our surgeons in the form of a patient self-assessment sheet.53 This screening questionnaire is filled out by the patient using a series of checkboxes. The boxes are aligned to a back page such that positive answers will check (via carbon copy) the recommended preoperative laboratories and whether a PAC consultation is suggested. For example, if an affirmative answer is recorded for the question "Do you have heart disease?" an electrocardiogram is ordered (if not recently done) and the patient may be referred for further evaluation (Table 7-10).
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Obesity and Obstructive Sleep Apnea
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Obesity is a well-established public health problem in developed countries. More specifically, obesity presents a major problem for practitioners who care for patients in the perioperative period. Obese patients have alterations in physiology at baseline that result in major lifestyle limitations, but they also have a well-documented increase in perioperative risk.54 This would seem to justify an ASA Physical Status classification of at least II, and perhaps III. Multiple physiologic comorbidities exist in obese patients (diabetes mellitus, obstructive sleep apnea [OSA], cardiovascular disease, osteoarthritis, and others).55 In addition, anatomic alterations of the airway also place these patients at increased risk for difficult mask ventilation and laryngoscopy.53 IV access can be extremely difficult in obese patients, and in some cases central access must be considered. Some consider obesity a risk factor for gastric aspiration, and preventive measures should be considered. Obesity clearly heightens risk for adverse perioperative respiratory outcomes.56 Blum et al reviewed the quality assurance events recorded from 25767 anesthetics. They found a statistically significant increase in failed intubation, reintubation, dental injury, and airway obstruction associated with increasing BMI.54
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Short of substantial weight loss prior to elective surgery (which has a dismal success rate), the perioperative risks just listed generally are not modifiable. Hence a key element for practitioners to consider in preparation for elective operation in obese patients is counseling, specifically with regard to weight loss (if time permits) and full disclosure of significantly heightened perioperative risks.57
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It may also be beneficial to prepare obese patients for practical issues such as difficult IV access and the possible need for awake intubation. OSA is a syndrome commonly associated with obesity and is characterized by periodic, partial, or complete airway obstruction during sleep. It is estimated that approximately 9% of women and 24% of men have some degree of OSA; severe symptomatic disease is present in approximately 2% of women and 4% of men.58 In October 2005 the ASA published a practice guideline, "Perioperative Management of Patients With Obstructive Sleep Apnea." This practice guideline comprehensively reviews the preoperative and postoperative management of patients with this disorder.59 On occasion, patients who are considered to be healthy may have undiagnosed OSA, and therefore it is important to get a complete history, specifically as it relates to snoring and daytime somnolence. If the patient is indeed suspected of having the syndrome, then they should be evaluated before an elective procedure as recommended by the practice guideline.
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The US population is aging rapidly, and an increasing proportion of surgical procedures are performed in the elderly. In 1986 Tiret et al provided evidence that the elderly have higher perioperative complication rates and higher risk than their younger counterparts, even in the absence of comorbidities.60 The issue of perioperative risk, as it relates solely to advancing age, however, is far from settled.61 Some would therefore assert that anesthetizing "healthy" elderly patients poses no significant elevation in perioperative risk. But even "healthy" elderly patients may have marked diminution in the function of major organ systems.62 This would cause some to assign the ASA classification of II or even III to all such patients. Aside from the universal physiologic changes seen in all elderly patients ("aging"), elderly patients definitely tend to accumulate coexisting disease. Importantly, Kim and colleagues clearly demonstrated that coexisting disease in the elderly is a strong predictor of complications.63 Elderly patients often have additional and unique perioperative challenges. Many have poor hearing and eyesight, and some suffer from cognitive impairment. This can make communication difficult. Simple issues like transportation home after conscious sedation can become logistical problems in the elderly. Another important effect of aging is altered drug disposition. Elderly patients have diminished volumes of distribution, decreased clearance, and heightened sensitivity to nearly all medications. This explains why elderly patients are more sensitive to the therapeutic actions of most drugs and markedly more susceptible to side effects. In summary, despite changes attributable to normal aging, there is no strong association between age itself and perioperative risk. Thus chronologic age per se should not be a contraindication to surgery. Finally, to avoid complications and dissatisfaction in the elderly, anesthesia providers need to understand the altered pharmacology, physiology, and special needs that accompany the normal aging process.
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Approximately one in five adult Americans currently smoke, and millions of elective surgical procedures are performed each year on these individuals. This is unfortunate because cigarette smoking is independently responsible for an alarming increase in the rate of perioperative pulmonary complications.64 Cigarette smoking is an addictive disease that adversely alters the lifestyle of those affected. This fact, coupled with the well-known perioperative risks that smoking confers,65 should result in otherwise healthy smokers being classified as at least ASA II and, in many cases, ASA III. A 2000 US Public Health Service guideline advised all physicians to "strongly advise every patient who smokes to quit because evidence shows that physician advice to quit smoking increases abstinence rates."66 Further, anesthesiologists are uniquely positioned to give such advice. The preoperative interaction has been described by Warner as a "teachable moment" that not only lowers immediate perioperative risk but is also of great benefit to the long-term health of smokers.67 Quitting smoking immediately before surgery has not been shown to heighten risk, produce untoward anxiety, or consistently precipitate nicotine withdrawl.68 Hence patients who smoke should not be considered "healthy." These patients should be advised of the elevation in perioperative risk that is attributable to their habit and be encouraged to quit as soon as possible before their elective surgical procedure.
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Preoperative Testing in Healthy Patients
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Billions of dollars are wasted in the United States each year on unnecessary preoperative testing.69 In the case of healthy patients, this testing is almost always unnecessary.70 It is generally accepted that healthy patients undergoing low-risk surgical procedures require no specific laboratory testing unless clinically indicated.71 Little evidence exists regarding the propriety of such routine testing in healthy patients undergoing more complicated procedures with the potential for major blood loss (eg, major corrective orthopedic procedures, brain aneurysm clipping). Many recommend obtaining a preoperative hematocrit level in menstruating women, but there is little evidence to support this.72 Women of childbearing age should be given pregnancy tests if it cannot be ascertained for certain whether or not they are pregnant. It is our institutional policy that women 18 years of age and older be asked, "Is it possible that you could be pregnant?" If they answer "no," they are not tested. This is in general agreement with the ASA stance on this issue: "The task force believes that the literature is inadequate to inform patients or physicians on whether anesthesia causes harmful effects on early pregnancy. Pregnancy testing may be offered to female patients of childbearing age and for whom the result would alter the patient's management."54
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The indiscriminate ordering of batteries of routine tests, even in patients with serious comorbidity, has been the subject of intense recent review and been found to be excessively expensive and ineffective.31 In fact, batteries of routine tests and their subsequent interpretations were found to predict morbidity more poorly than simple use of either the ASA physical status classification or the ACC/AHA6 guidelines. The ASA Practice Advisory recommends that "specific tests and their timing should be individualized and based upon information obtained from sources such as the patient's medical record, interview, physical examination, and the types and invasiveness of the planned procedure."54 These concepts were well summarized by Halaszynski et al, in their 2004 article addressing this issue31 (see Table 7-11).
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They suggest that age be used as a basic criterion for testing, with the additional components of surgical complexity and medical illness allowing for layers of flexibility. According to this paradigm, healthy patients younger than 45 years having uncomplicated operations require no testing. As patients deviate from this healthy/uncomplicated baseline, testing may be indicated but in a directed and temporally related fashion (if a test has been done recently, it does not generally need to be repeated). Thus if it can be ascertained from a history and physical examination that a patient is healthy, "routine" testing is rarely indicated in patients having uncomplicated surgical procedures. Age-based thresholds (men >45 years, women >55 years) for obtaining preoperative ECGs were recently called into question due to their arbitrary nature and unsatisfactory yield.73