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 aller-gies, and responses and reactions to previous anes-thetics. Additionally, this evaluation should include any indicated diagnostic tests, imaging procedures, or consultations from other physicians. The pre-operative 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 has-ten 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 diffi-cult to intubate, one with a family history of malig-nant 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 anestheticrisk. However, the anesthesiologist should not be expected to provide the risk-versus-benefitdiscussion for the proposed procedure; this is the responsibility and purview of the responsible sur-geon or “proceduralist.” For example, a discussion of the risks and benefits of robotic prostatectomy ver-sus radiation therapy versus “watchful waiting” requires knowledge of both the medical literature and the morbidity–mortality statistics of an individ-ual surgeon, and it would be most unusual for an anesthesiologist to have access to the necessary data for this discussion. Finally, the preoperative evalua-tion is an opportunity for the anesthesiologist to describe the proposed anesthetic plan in the context of the overall surgical and postoperative plan, pro-vide the patient with psychological support, and obtain informed consent for the proposed anesthetic plan from the surgical patient.
By convention, physicians in many coun-tries 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.