Anesthesia

Modern anesthesia is extremely safe. In a review of over 100,000 procedures under anesthesia,

patient and surgical risk factors were much more important in predicting seven day mortality than the anesthesia factors studied The duration of anesthesia, experience of the anesthesiologist, and inhalation techniques were not associated with increased

mortality.

The American Society of Anesthesiology Classification of Preoperative Risk is shown in table 1 below.

Sources of anesthetic risk

Even healthy patients have a small unavoidable risk of adverse events during surgery. Anesthetic risks include stress responses to anesthetic drugs (e.g., myocardial ischemia), adverse and idiosyncratic reactions to anesthetic agents (e.g., malignant hyperthermia, halothane-induced hepatitis), and mechanical or operator error (e.g., esophageal intubation). In addition, there are predictable organ system effects from anesthesia:

• Inhalational anesthetics are myocardial depressants.

• here is a decrease in functional residual capacity below closing volumes with resulting atelectasis and V/Q mismatch. There is also a decrease in mucociliary clearance, loss of sighing breaths, depression of the response to hypoxia and hypercarbia, and an alteration in diaphragmatic movement.

Table 1 - ASA classes and risk of mortality

Please note that this chapter deals with the healthy patient proceeding for surgery _ Assessment of cardiac risk for patients undergoing non- cardiac surgery is discussed separately.

While these may not be important in the healthy individual they contribute to morbidity in certain situations.

Type of anesthesia

There is no difference in cardiac or overall perioperative mortality between general and spinal anesthesia. In a study of over 500 patients who had internal fixation surgery for fracture of the upper femur the 28 day mortality rate was 6.6 and 5.9 percent for subarachnoid spinal and general anesthesia, respectively; this difference was not significant. Regional anesthesia, such as an axillary block for hand surgery with conscious sedation, is associated with a lower risk. Since the type of anesthesia does not influence mortality, the , family physician should not recommend a particular anesthetic technique.