The cardiac anesthesiologist is challenged with the requirements of maintaining general anesthesia while also serving as the patient's intensivist and diagnostician, facilitating the surgery and maintaining vital organ function. The objectives of a general anesthetic are analgesia, amnesia, and unconsciousness while supporting vital physiologic function and creating satisfactory operating conditions. An effective general anesthetic blunts the physiologic responses to surgical trauma and hemodynamic perturbations while permitting recovery at a predictable time after the operation. To accomplish this, the anesthesiologist must act as the patient's medical intensivist: support life with mechanical ventilation; control the circulation; and diagnose and treat acute emergencies that may occur during surgical incision, rapid changes in body temperature, extracorporeal circulation, and acute shifts in intravascular volume. The cardiac anesthesiologist must provide complex diagnostics in order to facilitate surgery by determining the competency of heart reconstructive procedures and measuring the cardiovascular response to altered cardiac anatomy and physiology. The task in cardiac surgery is unique because of the nature of the operations and the narrow tolerance for hemodynamic alterations in patients with critical cardiac disease. Anesthetic management of the cardiac surgical patient is intimately related to the planned operative procedure and the anticipated timing of intraoperative events.
The preoperative visit by the anesthesiologist is aimed at the formulation of an anesthetic plan based on the patient's surgical illness, scheduled operation, and concomitant medical problems. The medical history is elicited by questioning the patient and reviewing the medical records. The anesthesiologist must know the status of the cardiovascular system, related morbidity, and concurrent medications to design the anesthetic safely for a patient undergoing heart surgery. All anesthetic drugs have a direct effect on cardiac function, vascular tone, and/or the autonomic nervous system. The American Society of Anesthesiologists (ASA) has developed a physical status classification as a general measure of the patient's severity of illness (Table 10-1).1
Table 10-1 American Society of Anesthesiologists, Physical Status Classification |Favorite Table|Download (.pdf)
Table 10-1 American Society of Anesthesiologists, Physical Status Classification
Class 1: Normal healthy patient
Class 2: Systemic disease without end-organ dysfunction
Class 3: Systemic disease with end-organ dysfunction that is not incapacitating (eg, diabetes mellitus with abnormal renal function)
Class 4: Systemic disease with end-organ dysfunction that is incapacitating (eg, diabetes mellitus with renal failure and ketoacidosis)
Class 5: Moribund patient unexpected to survive beyond 24 yours (eg, diabetes mellitus with renal failure, ketoacidosis, and infarcted bowel requiring vasopressor support)
E*: Emergency surgery
In addition to contributing to postoperative morbidity, concurrent medical illness often defines an acceptable range for monitored parameters that are controlled during cardiac surgery. Acceptable intraoperative blood pressure may be altered based on several preoperative findings. The brain of a patient with long-standing severe hypertension may perfuse inadequately if the blood pressure during surgery is maintained only within what is typically considered a “normal” range because of ...