Key Concepts
The cornerstones of an effective preoperative evaluation are the history and physical examination, which should include a complete account of all medications taken by the patient in the recent past, all pertinent drug and contact allergies, and responses and reactions to previous anesthetics.
The anesthesiologist should not be expected to provide the risk-versus-benefit discussion for the proposed procedure; this is the responsibility and purview of the responsible surgeon or “proceduralist.”
By convention physicians in many countries use the American Society of Anesthesiologists’ classification to identify relative risk prior to conscious sedation and surgical anesthesia.
In general, the indications for cardiovascular investigations are the same in surgical patients as in any other patient.
Adequacy of long-term blood glucose control can be easily and rapidly assessed by measurement of hemoglobin A1c.
In patients deemed at high risk for thrombosis (eg, those with certain mechanical heart valve implants or with atrial fibrillation and a prior thromboembolic stroke), warfarin should be replaced by intravenous heparin or, more commonly, by intramuscular heparinoids to minimize the risk.
Current guidelines recommend postponing all but mandatory emergency surgery until at least 1 month after any coronary intervention and suggest that treatment options other than a drug-eluting stent (which requires prolonged dual antiplatelet therapy) be used in patients expected to undergo a surgical procedure within 12 months after the intervention.
There are no good outcomes data to support restricting fluid intake (of any kind or any amount) more than 2 h before induction of general anesthesia in healthy patients undergoing elective procedures; indeed, there is evidence that nondiabetic patients should be encouraged to drink glucose-containing fluids up to 2 h before induction of anesthesia.
To be valuable, preoperative testing must discriminate: an increased perioperative risk exists when the results are abnormal (and unknown); a reduced risk exists when the abnormality is absent or detected (and perhaps corrected).
The utility of a test depends on its sensitivity and specificity. Sensitive tests have a low rate of false-negative results and rarely fail to identify an abnormality when one is present, whereas specific tests have a low rate of false-positive results and rarely identify an abnormality when one is not present.
Premedication should be given purposefully, not as a mindless routine.
Incomplete, inaccurate, or illegible records unnecessarily complicate defending a physician against otherwise unjustified allegations of malpractice.
Preoperative Evaluation
The cornerstones of an effective preoperative evaluation are the medical history and physical examination, which should include a complete account of all medications taken by the patient in the recent past, all pertinent drug and contact allergies, and responses and reactions to previous anesthetics. Additionally, this evaluation should include any indicated diagnostic tests, imaging procedures, or consultations from other physicians. The preoperative evaluation guides the anesthetic plan: inadequate preoperative planning and incomplete patient preparation are commonly associated with anesthetic complications.
The preoperative evaluation serves multiple purposes. One purpose is to identify those few patients whose outcomes likely will be improved by implementation of a specific medical treatment (which in rare circumstances may require that the planned surgery be rescheduled). For example, a 60-year-old patient scheduled for elective total hip arthroplasty who also has unstable angina from left main coronary artery disease would more likely survive if coronary artery bypass grafting is performed before the elective procedure. Another purpose is to identify patients whose condition is so poor that the proposed surgery might only hasten death without improving the quality of life. For example, a patient with severe chronic lung disease, end-stage kidney failure, liver failure, and heart failure likely would not survive to derive benefit from an 8-hour, complex, multilevel spinal fusion with instrumentation.
The preoperative evaluation can identify patients with specific characteristics that likely will influence the proposed anesthetic plan (Table 18-1). For example, the anesthetic plan may need to be reassessed for a patient whose trachea appears difficult to intubate, one with a family history of malignant hyperthermia, or one with an infection near where a proposed regional anesthetic would be administered. Another purpose of the evaluation is to provide the patient with an estimate of anesthetic risk. 
However, the anesthesiologist should not be expected to provide the risk-versus-benefit discussion for the proposed procedure; this is the responsibility and purview of the responsible surgeon or “proceduralist.” For example, a discussion of the risks and benefits of robotic prostatectomy versus radiation therapy versus “watchful waiting” requires knowledge of both the medical literature and the morbidity-mortality statistics of an individual surgeon, and it would be most unusual for an anesthesiologist to have access to the necessary data for this discussion. Finally, the preoperative evaluation is an opportunity for the anesthesiologist to describe the proposed anesthetic plan in the context of the overall surgical and postoperative plan, provide the patient with psychological support, and obtain informed consent for the proposed anesthetic plan from the surgical patient.
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By convention, physicians in many countries use the American Society of Anesthesiologists’ (ASA) classification to define relative risk prior to conscious sedation and surgical anesthesia (Table 18-2). The ASA physical status classification has many advantages over all other risk classification tools: it is time honored, simple, reproducible, and, most importantly, it has been shown to be strongly associated with perioperative risk. But, many other risk assessment tools are available.
| Class | Definition |
|---|---|
| 1 | Normal healthy patient |
| 2 | Patient with mild systemic disease (no functional limitations) |
| 3 | Patient with severe systemic disease (some functional limitations) |
| 4 | Patient with severe systemic disease that is a constant threat to life (functionality incapacitated) |
| 5 | Moribund patient who is not expected to survive without the operation |
| 6 | Brain-dead patient whose organs are being removed for donor purposes |
| E | If the procedure is an emergency, the physical status is followed by “E” (for example, “2E”) |
Patients presenting for elective surgery and anesthesia typically require a focused preoperative medical history emphasizing cardiac and pulmonary function, kidney disease, endocrine and metabolic diseases, musculoskeletal and anatomic issues relevant to airway management and regional anesthesia, and responses and reactions to previous anesthetics. The ASA publishes and periodically updates general guidelines for preoperative assessment (see Guidelines).
Guidelines for preoperative cardiac assessment are available from the American College of Cardiology/American Heart Association and from the European Society of Cardiology (see Guidelines). A more complete discussion of cardiovascular assessment is provided in Chapter 21. The focus of preoperative cardiac assessment should be on determining whether the patient’s condition can and must be improved prior to the scheduled procedure, and whether the patient meets criteria for further cardiac evaluation prior to the scheduled surgery. Clearly the criteria for what must be done before elective arthroplasty will differ from what must be done before an operation for resectable pancreatic cancer, given the benign results of a delay in the former procedure and the potential life-shortening effects of a delay in the latter procedure. 
In general, the indications for cardiovascular investigations are the same in surgical patients as in any other patient. Put another way, the fact that a patient is scheduled to undergo surgery does not change the indications for such measures as noninvasive stress testing to diagnose coronary artery disease.
Perioperative pulmonary complications, most notably postoperative respiratory depression and respiratory failure, are vexing problems that have become seemingly more common as severe obesity and obstructive sleep apnea have increased in incidence. A recent guideline developed by the American College of Physicians takes an aggressive stance; it identifies patients 60 years of age or older, those with chronic obstructive lung disease, those with markedly reduced exercise tolerance and functional dependence, and those with heart failure as potentially requiring preoperative and postoperative interventions to avoid complications. The risk of postoperative pulmonary complications is closely associated with these factors, and with the following: ASA class (class 3 and 4 patients have a markedly increased risk of pulmonary complications relative to class 1 patients), cigarette smoking, longer surgeries (>4 h), certain types of surgery (abdominal, thoracic, aortic aneurysm, head and neck, and emergency surgery), and general anesthesia (compared with cases in which general anesthesia was not used).
Efforts at prevention of pulmonary complications should focus on cessation of cigarette smoking prior to surgery and on lung expansion techniques (eg, incentive spirometry) after surgery in patients at risk. Patients with asthma, particularly those receiving suboptimal medical management, have a greater risk for bronchospasm during airway manipulation. Appropriate use of analgesia and monitoring are key strategies for avoiding postoperative respiratory depression in patients with obstructive sleep apnea. Further discussion of this topic appears in Chapter 44.
Appropriate targets for control of diabetes mellitus and of blood glucose in critically ill patients have been subjects of great debate over the past decade. “Tight” control of blood glucose, with a target level in the normal range, was shown in the Diabetes Control and Complications Trial to improve outcomes in ambulatory patients with type 1 diabetes mellitus. It has become the usual practice to obtain a blood glucose measurement on the morning of elective surgery. Unfortunately, many diabetic patients presenting for elective surgery do not maintain blood glucose within the desired range. Other patients, who may be unaware that they have type 2 diabetes, present with blood glucose measurements above the normal range. 
Adequacy of long-term blood glucose control can be easily and rapidly assessed by measurement of hemoglobin A1c. In patients with abnormally elevated hemoglobin A1c, referral to a diabetology service for education about the disease and adjustment of diet and medications to improve metabolic control may be beneficial. Elective surgery should be delayed in patients presenting with marked hyperglycemia; this delay might consist only of rearranging the order of scheduled cases to allow insulin infusion to bring the blood glucose concentration closer to the normal range before surgery begins. A more complete discussion of diabetes mellitus and other perioperative endocrine concerns is provided in Chapter 34.
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