Editors: Shields, Thomas W.; LoCicero, Joseph; Ponn, Ronald B.; Rusch, Valerie W.
Title: General Thoracic Surgery, 6th Edition
Copyright 2005 Lippincott Williams & Wilkins
> Table of Contents > Volume I - The Lung, Pleura, Diaphragm, and Chest Wall > Section VI - Anesthetic Management of the General Thoracic Surgical Patient > Chapter 21 - Preanesthetic Evaluation and Preparation
Chapter 21
Preanesthetic Evaluation and Preparation
Hak Yui Wong
It can be said that the flourishing of modern surgery, in particular thoracic surgery, was closely linked to the advancement in anesthesia, artificial ventilation, and intensive care. For it was not until the middle of 20th century that a patient's ability to survive the anesthetic ceased to be the major limiting factor when an operation was contemplated. The contemporary armamentarium of knowledge, drugs, and techniques has enabled anesthetizing virtually any patient and maintaining vital physiologic functions for an indeterminate length of time, thus allowing increasingly complex surgical procedures to proceed at ease. Parenthetically, this increasing sophistication and facility of anesthesia techniques have certainly played a permissive role in the development of less invasive forms of thoracic surgical operations, such as video-assisted thoracic surgery (VATS).
Perhaps because of this notion of enhanced anesthetic capability, and in parallel with the aging of the population, patients being considered for thoracic surgery are increasingly older and have greater complexity of their medical problems. At the same time, secular trend in health care and economic demands have shifted presurgical preparation that was previously performed in the hospital setting to an ambulatory, and most likely more fragmented, setting. The anesthesiologist as a perioperative physician, therefore, is expected not only to provide a complex anesthetic but also to be actively involved in the increasingly complex medical care required by the patient, all the while with diminishing time available to become acquainted with the patient's medical problems and the proposed operation. Current standard of practice, in addition, calls for explaining the procedure and risks to the patient and obtaining a specific informed consent for the care to be provided by the anesthesia team. In this current environment, the patient is often afforded little time to absorb and adjust to the newly acquired information or to explore any questions that may arise.
ANESTHESIA PREOPERATIVE EVALUATION CLINIC
In an effort to counter this problem, many hospital departments of anesthesia have established outpatient preoperative evaluation clinics staffed by anesthesiologists and nurse anesthetists to initiate preanesthetic evaluation for patients not requiring preoperative hospitalization. The venue allows time to conduct additional tests and evaluations (if unsuspected abnormalities are uncovered), for consultations between specialists, and to initiate necessary diagnostic and corrective measures. It often also serves as a centralized location to integrate and coordinate multiple administrative functions such as admission, registration, insurance authorization, and patient education and instruction. In this manner, the shuttling of patients between geographically fragmented services can be reduced, and cancellations and delays on the day of operation can be minimized.
SCOPE OF PREANESTHETIC EVALUATION
Thoracic operations are distinguished from other surgical operations in that the structure and function of the vital life-sustaining organs (i.e., the heart, the airway, and the lungs) are directly and physically encrouched on during the surgical procedure, and this encrouchment quite often extends into the postoperative period. Therefore, besides a good general history and physical examination, which supply much of the factual information sought by the anesthesiologist, the preanesthetic evaluation should place the patient in the context of the proposed operation: the extent and nature of the operation, the degree and manner by which the operation and the anesthetic will stress the patient, and the residual physiologic defects that will be present postoperatively. This calls for significant familiarity with various thoracic operations on the part of the persons performing the evaluation.
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There are four general objectives in a preanesthetic evaluation:
To detect problems and factors in the patient's physical condition that may compromise the patient's ability to cope with perioperative stress or that can be aggravated by such stress
To assess the impact of specific pathology that necessitates the surgery
To appraise several concerns peculiar to the practice of anesthesia
To assess the risk-to-benefit ratio of specific anesthetic techniques and operation
General Physical Condition
It is not within the scope of this text to describe general history taking, physical examination, and appropriate laboratory screening tests that would be customarily necessary for all patients undergoing surgery and anesthesia. Given that many aging thoracic patients have concomitant chronic medical conditions, the focus of the general examination should be to ascertain that the patient is receiving optimal treatment and is at the best possible baseline. Because of the significant prevalence and the potential impact of these diseases on surgical and anesthetic outcome, cardiovascular disease, chronic obstructive airway disease, and renal impairment are conditions that warrant special attention.
The screening, evaluation, and diagnostic and therapeutic interventions for coexisting cardiac disease before thoracic operations is the subject of detailed discussion in Chapter 20. Because many thoracic patients have symptoms (such as shortness of breath) or limitations (such as inability to carry out physical activity) that are common findings in cardiac disease, an informative cardiac evaluation may require invasive modalities and the input of a consultant cardiologist. Nonetheless, it is crucial to ascertain before undertaking anesthesia and surgery that the patient is not in an unstable state, such as acute coronary syndrome, congestive heart failure, or uncontrolled cardiac arrhythmias. Therapeutic devices that are increasingly seen in elderly patients, such as pacemakers and automatic implantable cardiac defibrillators (AICDs), require advanced planning for preoperative evaluation and programming by the specialist service. As part of risk-reduction strategy, the institution of -adrenergic blockade, even starting just before the surgery, is now increasingly promulgated, as noted by Fleisher and Eagle (2001). Although there is as yet no firm evidence that this practice benefits patients undergoing noncardiac, nonvascular procedures, many thoracic surgical patients may now be given beta-blocking drugs during their preoperative cardiac evaluation, a practice that may have some impact on the intraoperative management of this group of patients who are at increased risk for developing bronchospasm and being subjected to mechanical disturbance of intrathoracic structures.
The evaluation of lung functions and dysfunctions from the standpoint of assessing operability is also the subject of Chapter 19. The focus of preanesthetic evaluation on the respiratory system should be to determine whether the patient has had a reasonable period of cessation of smoking and whether there is intercurrent atelectasis, exacerbation of bronchospasm, or infection that warrants a period of treatment before surgical procedure is undertaken. The possible disposition of the patient in terms of postoperative ventilatory support should also be considered at this point.
The presence of renal dysfunction before major thoracic surgery is predictive of postoperative development of renal failure, which carries a high mortality rate, as reported by Golledge and Goldstraw (1994). Other contributing factors for postoperative renal dysfunction may include diuretic therapy, infection, and extensive blood loss. The finding of preoperative renal dysfunction will therefore underscore the importance of meticulous fluid management and drug therapy in the intraoperative period.
One of the simplest and most enduring instruments that can be used to summarize the patient's preoperative physical condition is the American Society of Anesthesiologists (ASA) Physical Status classification (Table 21-1). Although this scale was originally conceived simply as a classification of the patient's physical status at the time of
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Table 21-1. American Society of Anesthesiologists Classification of Physical Status (ASA PS) | ||||||||||||
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Impact of Specific Pathology
Every surgical condition poses unique stress on the body and presents a different set of problems to the surgical and anesthesia team. This is particularly true in thoracic surgery because the surgical pathology often involves or impinges on the vital life-sustaining organs, that is, the heart and the lungs. From the standpoint of pathophysiology and anesthetic implications, general thoracic surgical conditions can be categorized into three groups: (a) esophageal diseases, (b) surgical diseases of the lungs, and (c) diseases of the mediastinum and pleura. Esophageal diseases can be divided into two groups: (i) obstructive disorders that predispose patients to preoperative dehydration and malnourishment; and (ii) refluxing and obstructive disorders that predispose patients to pulmonary aspiration (either chronically or in the course of the surgical procedure). Surgical diseases of the lungs may be divided into (i) abnormal sources of fluids, such as abscess and hemoptysis, posing risks for contamination of normal lung tissues; (ii) abnormal solid tissues, such as tumors and consolidation, which may constitute right-to-left shunting; and (iii) obstructive lesions, preventing normal airflow and facilitating the development of consolidation and abnormal fluid collection. Diseases of the mediastinum and pleura include (i) obstruction of airways or large veins, such as the superior vena cava syndrome; (ii) abnormal paths of communication, such as bronchopleural fistula; and (iii) abnormal collections of fluid, such as empyema (Table 21-2).
Anesthetic Concerns
In addition to evaluating general physical condition and specific medical and surgical problems, the preanesthetic evaluation addresses a set of issues best described as of unique concern to the practice of anesthesia.
Anesthetic History
A review of the patient's experience with previous anesthetics and examination of available prior anesthetic records, with special notice given to previous difficulties such as difficult endotracheal intubation, prolonged apnea, or postoperative jaundice, can avert potential disasters. Careful and pertinent family history may alert one to the possibility of rare but important problems such as malignant hyperpyrexia or pseudocholinesterase deficiency.
Medication History
Concurrent use of multiple medications is a fact of modern medical life. It is more likely in the older patients, who may take upward of five or six medications daily. In addition, the use of complementary and alternative medications is increasing, especially among those coping with chronic
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Table 21-2. An Anesthetic Classification of General Thoracic Surgical Conditions | ||||||||||||||||||||||||||||
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Table 21-3. Examples of Significant Drug Interactions During Anesthesia | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Status of the Upper Airway
The assessment of the upper airway is an integral part of any preanesthetic evaluation, but it is of special importance for the thoracic surgery patients. Frequent need for special airway instrumentation, such as rigid bronchoscopy and endobronchial tube insertion, makes the anatomy of the upper airway an important factor to consider. Many thoracic surgical patients are at higher risk for pulmonary aspiration because of their surgical pathologies. Many have coexisting ischemic heart disease as well as lung disease, which limit the size of their oxygen reserve. For these reasons, unanticipated difficulty in maintaining airway patency or endotracheal intubation is especially damaging and should best be avoided. Evaluation of the upper airway includes not only physical dimensions and configurations but also the functional aspect of the temporomandibular joints and the cervical spine, including the vertebrobasilar arteries. Occasionally, special studies, such as computed tomography and magnetic resonance imaging of the airway, are necessary to achieve a complete evaluation.
Intravascular Access
The condition of peripheral veins should be assessed in relation to the extent and site of the proposed operation. Patients with inadequate peripheral venous access should be prepared for central venous cannulation. Potential arterial cannulation sites are examined and tested for the presence of adequate collateral circulation.
Postoperative Ventilation
The probability of requiring postoperative tracheal intubation and mechanical ventilation is often predictable, based on the nature of the proposed surgical procedure, anticipated further impairment of the patient's respiratory reserve, condition of the cardiovascular system, and anesthetic technique chosen. This assessment may influence the choice of endotracheal tubes and routes of intubation as well as the choice of anesthestic drugs. Parenthetically, an anesthetic technique using longer-acting respiratory depressants and sedatives may be indicated for a patient requiring postoperative ventilation. The patient and family should also be apprised of this assessment and psychologically prepared for this stressful event.
Postoperative Pain Relief
At the time of preanesthetic evaluation, patients should be given a realistic appraisal of anticipated postoperative discomfort,
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ASSESSMENT OF RISK
Risk is defined as the chance of adverse outcome, including death and serious morbidities. With few exceptions, adverse outcomes after surgical procedures are multifactorial in etiology. In contemporary practice, adverse outcomes that can be attributed solely and directly to anesthesia per se are rare; most of these rare occurrences can be thought of as accidents, by-and-large unpredictable by and unrelated to the patient's preoperative state of health. Thus, as summarized by Goldstein and Keats (1970), epidemiologic studies of anesthetic risk have widely varying results and severe limitations. Indeed, it would be nearly impossible to nominate distinct conditions that would constitute unacceptable anesthetic risks that would preclude a patient from receiving anesthesia in order to undergo an indicated operative procedure.
Risk assessment in the course of preanesthetic evaluation would concentrate on factors that are imminently threatening to the patient's chance of coming through and recovering from the operation. For this purpose and attempts at risk reduction, adverse outcomes after thoracic surgery can be divided broadly into two groups. The first group of adverse outcomes is dictated by the nature of the procedure and the skill of the personnel involved and is relatively unrelated to the preoperative state of the patient. The thoracic location of the surgical procedure by itself imposes a higher risk for intraoperative and postoperative complications. In addition, four intraoperative threats are constantly present during thoracic surgery: (a) sudden hemorrhage, (b) cardiac arrhythmia, (c) mechanical interference with mediastinal structures, and (d) ventilation or oxygenation difficulties. Other accidental risks, not necessarily unique to thoracic surgery, include adverse drug interaction, anaphylaxis, and rare occurrences such as malignant hyperpyrexia.
The second group of adverse outcomes is fairly predictable from the preoperative state of the patient in the context of the proposed operation. Interventions that modify the patient's preoperative state, or alter the surgical procedure chosen, may influence the occurrence of these outcomes. These adverse outcomes include pulmonary complications, such as atelectasis, infection, and respiratory failure; and cardiovascular complications, including congestive heart failure, acute myocardial ischemia, and serious arrhythmias. There is now extensive literature that details the prediction of these events, the prognostication, and the effect of preoperative interventions.
Risk for Pulmonary Complications
Pulmonary complications are common after thoracic and abdominal surgical procedures. Anderson and associates (1963) have shown the well-known relationship between the site of operation and the incidence of complications. Thoracic surgery carries the highest risk. Respiratory insufficiency secondary to the loss of lung tissue by surgical resection is quite predictable based on preoperative pulmonary function and the extent of surgical resection. This topic is discussed in detail in Chapter 19.
Pulmonary complications not due to the loss of lung tissue are related to the effect of surgery and anesthesia on various aspects of the respiratory system: mucociliary transport, mechanics of breathing, and decrease in the functional reserve volume and forced vital capacity. Atelectasis is said to affect 10% to 50% of all surgical patients. Risk estimation based on early epidemiologic studies is less than helpful: in these early studies, patients and case mix were often undefined, varying end points were used in morbidity measurement, the bias of preoperative treatment was ignored, and the effects of retrospective and prospective design were often not delineated in such reports. In addition, the focus of thoracic surgical literature has been on tuberculosis and cancer; the risk of other types of thoracic surgical procedures therefore has to be extrapolated from data collected from these conditions. Nonetheless, chronic respiratory disease (including chronic obstructive pulmonary disease and asthma), cigarette smoking, morbid obesity, and age older than 70 years, are accepted as risk factors for postoperative pulmonary complications. Severely abnormal forced vital capacity, maximum voluntary ventilation of less than 50% of the predicted value, and forced expiratory volume in 1 second of less than 1 L have been shown to be sensitive predictors of severe morbidity and death, but no agreement exists about the cutoff point for prohibitive risks.
Extrapulmonary factors may also influence the risk for postoperative pulmonary complications. Forrest and associates (1992) found that cardiac failure, myocardial ischemia,
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Preoperative treatment of conditions such as infection, acute exacerbation of bronchospasm, and bronchorrhea may reduce postoperative pulmonary complications, as shown by Stein (1962), Tarhan (1973), and Gracey (1979) and their colleagues. Warner and associates (1989) have shown the value of stopping smoking before coronary artery bypass surgery. Other prophylactic measures, such as incentive spirometry, may be of value, especially in the high-risk patients.
Risk for Cardiovascular Complications
General thoracic operations, excluding pneumonectomy, carry intermediate risk in terms of occurrence of perioperative cardiovascular complications. However, because of the age of the thoracic surgical population and predisposing risk factors common to both lung and heart diseases, cardiovascular complications are second only to pulmonary complications as leading causes of postoperative morbidity and mortality. Much effort has been expended on predicting and modifying the risk for perioperative cardiovascular morbidity and mortality. The significance of existing coronary artery disease (using previous myocardial infarction as a marker) has long been recognized since early reports such as those by Topkins and Artusio (1964) and Tarhan and colleagues (1972) and in more recent reports by Rao (1983), Foster (1986), and Shah (1990) and their associates. Of interest also is the peak incidence of perioperative myocardial infarction during the second and third postoperative days when many patients are no longer under close surveillance.
Besides previous myocardial infarction, signs of congestive heart failure, aortic valvular disease, and abnormal cardiac rhythm are consistent and powerful predictors of perioperative cardiovascular complications, as highlighted by Goldman and associates (1977) in their seminal Multifactorial Cardiac Risk Index (Tables 21-4 and 21-5). Adequate preoperative treatment of congestive heart failure, acute myocardial ischemia, and abnormal cardiac rhythm compromising hemodynamics would almost certainly be beneficial. In contrast, the value and choice of different treatment options for stable coronary artery disease before noncardiac surgery is much less certain. Data from retrospective studies such as those by Mahar (1978), Foster (1986), and Reul (1986) and their associates suggested that coronary artery bypass graft surgery might confer protective influence in patients undergoing noncardiac surgery. A more recent study by
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Table 21-4. Factors Correlated with Cardiac Risk in Surgical Patients | ||||||||||||||||||||||||||||||||||
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Table 21-5. Correlation of Cardiac Risk with Total Points | ||||||||||||||||||||||||||||||||
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The use of medical therapy as a risk-reducing measure has gained much attention, in particular the use of -adrenergic blocking drugs and 2-agonists. The evidence supporting the beneficial effect of these drugs has been gathered from studies of high-risk patients, most of whom were undergoing vascular surgery. There is as yet no firm evidence that this practice is equally beneficial for other patients, including those undergoing thoracic surgery. Nevertheless, continuation of previously indicated beta-blocking drugs and the institution of new therapy in the high-risk patient just before surgery are now considered class I indications.
The occurrence of cardiac arrhythmia, especially supraventricular arrhythmia, is not uncommon in thoracic surgery patients, particularly those undergoing pulmonary resection. Shields and Ujiki (1968) and Deutsch and Dalen (1969) have discussed preoperative digitalization. As discussed by Jakobsen (1997) and Bayliff (1999) and their associates, contemporary practice appears to move away from digitalis and toward beta-blocking drugs, both for reducing the incidence of arrhythmia and for controlling the ventricular rate and facilitating conversion to sinus rhythm.
After careful review of the medical record, laboratory tests, patient interview, and examination, and after taking into consideration the nature and demand of the proposed operation, a patient can usually be assigned to one of the following three categories: (a) the patient is in optimal condition and not at excessive risk, and anesthesia and surgical intervention can proceed; (b) the patient's condition is questionable in some areas, and specialist consultation and investigation are needed; (c) the patient is obviously receiving less than optimal treatment, and further preoperative treatment and follow-up evaluation are needed.
PREANESTHETIC TREATMENT AND PREPARATION
Preanesthetic treatment of coexisting diseases uncovered during preanesthetic evaluation must be considered in the timeframe of urgency of the proposed surgical procedure. In the best of circumstances, the objective would be to treat acute reversible disorders, return the patient with a chronic disorder to an optimal baseline, and act to minimize the postoperative functional derangement. Although the primary responsibility for implementing treatment rests with the primary physician and the surgeon, the anesthesiologist has a vested interest because the result of such treatment may have a significant impact on the patient's intraoperative course.
INTERDISCIPLINARY CONSULTATION
Because the anesthesiologist approaches the patient-operation complex from a perspective somewhat different from that of other physicians, he or she frequently uncovers problems that may have been overlooked or ignored. It is important that the anesthesia and surgical teams maintain open and equitable communication so that such problems can be satisfactorily resolved before the surgical procedure.
When diagnostic or therapeutic uncertainty exists outside the defined expertise of both the surgeon and the anesthesiologist, specialist consultation is indicated. Examples are evaluation of chest pain and borderline electrocardiogram, diagnosis of complex arrhythmias, testing of pacemakers, and control of severe bronchospasm. Occasionally, a preoperative consultation is sought in anticipation of a likely postoperative problem that will require specialist management, such as renal failure or total parenteral nutrition. Cohen (1998) and Merli and Weitz (1993) have reiterated the importance of effective communication between the consultant and others involved in the patient's care, addressing specific questions regarding the patient. The concept of medical clearance as a consultation should be abandoned because not only is it unhelpful to the anesthesia and surgical teams but also it is patronizing and misleading. During the intraoperative and immediate postoperative period, the anesthesiologist alone has to shoulder the responsibility for the care and support of the patient's physiology. The anesthesiologist, therefore, in consultation with the surgeon, must be the final arbiter on the patient's suitability for the procedure and the anesthetic technique of choice. Del Guercio and Cohn (1980) presented data that indirectly support this position. Of 148 elderly patients who had been cleared medically for operation, subsequent invasive hemodynamic data showed 23.5% to have had increased risks. All those in this group who had the proposed procedure died. Of special interest, these patients were readily identified by experienced anesthesiologists using ASA Physical Status classification (see Table 21-1).
PSYCHOLOGICAL PREPARATION OF THE PATIENT
Evaluation of the patient's preoperative psychological state is an important part of the preanesthetic evaluation. For the patient, the impending operation naturally generates anxiety and a whole host of other emotions. An interesting
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INFORMED CONSENT
Before making the final preparation to begin anesthesia and the operation, the patient should be adequately informed about the potential benefits and risks of the chosen course and give explicit consent to proceed. The subject of informed consent is a complex one and cannot be explicated here. From the humanistic standpoint, one of the major perceived difficulties of informed consent is in striking a balance between providing enough information and unduly alarming the patient, given the inherent risks of any anesthetic and operative procedure, not the least thoracic surgery. However, the information age may have helped blunt the imagined terror of fact disclosure. Kerrigan and associates (1993) found that a group of men given detailed information and possible adverse outcomes related to their upcoming hernia operation did not have increased anxiety. The task of informed consent may be eased in part by highlighting problems and risks that are amenable to preoperative correction, advising the patient in general terms that any anesthetic poses risks, and then inquiring if the patient wishes to know the specifics of all the possible risks. Many patients would then guide the anesthesiologist as far as their coping would allow. The essence of such discussion should be documented as part of the proof of informed consent. An occasional patient may decline any discussion of risks, or the physician may find the patient in a state unsuitable to bear such an ordeal. These should also be documented.
PREANESTHETIC MEDICATION
The aims of preanesthetic medication are to decrease anxiety without producing excessive drowsiness; facilitate a smooth, rapid induction without prolonging emergence; provide amnesia for the perioperative period while maintaining cooperation before loss of consciousness; and relieve preoperative pain. Classes of drugs commonly used for this purpose include (a) sedatives, hypnotics, and tranquilizers; (b) opioids; (c) anticholinergics; and (d) antihistamines and antacids. The appropriate drugs and doses can be chosen only after taking into consideration the psychological and physiologic conditions of the patient, the type and extent of the operation, the expected postoperative course, and the anesthetic technique chosen. As reviewed by Kanto and associates (1996), in contemporary practice, routine heavy premedication is avoided, but emphasis is placed on anxiolysis as the main objective. Interestingly, Egbert and associates (1963) found that a good preanesthetic visit may be as effective as administration of sedatives in decreasing the level of anxiety. Several categories of patients should very rarely receive preanesthetic medication before arriving in the operating room. These are patients who have not given informed consent and those with marginal cerebral function, uncorrected hypovolemia, or severe heart disease, lung disease, or both, and those in whom the respiratory and sympathetic drives are crucial.
CONCLUSION
Preanesthetic evaluation and preparation are integral parts of good anesthetic practice. It is essential for establishing physician-patient rapport and ensuring that the patient is in an optimal state for the proposed operation. By being thoroughly familiar with the patient and the operation, the anesthesiologist can take steps to minimize intraoperative risk and postoperative problems and facilitate the performance of the surgical procedure. The choice of monitoring an anesthetic technique follows rationally and provides optimal safety for the patient.
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