RISKS RELATED TO SURGERY

The surgical procedure itself significantly influences perioperative risk. In virtually every study performed, emergency surgery is associated with additional risk. For example, in the study of Goldman and colleagues,^[13] emergency surgery was associated with the second highest weight (i.e., number of points), after active signs of congestive heart failure. In the same study, intrathoracic and abdominal procedures were determined to have a higher risk.

In some cases, the risk related to surgery is a function of the underlying disease processes and the stress related to the surgical procedure. Cardiovascular surgery is associated with the highest risk of any procedure. The risks related to cardiac surgery are reviewed in Chapter 50 . Vascular surgery is among the highest-risk group of the noncardiac procedures. Although aortic reconstructive surgery has traditionally been considered the procedure with highest risk, infrainguinal procedures have shown a similar rate of cardiac morbidity in several studies.^{[176] [177]} In an attempt to analyze the causes for the high complication rate on a relatively peripheral procedure, L'Italien and coworkers^[177] demonstrated that the extent of coronary artery disease is higher among patients undergoing infrainguinal procedures and most likely accounts for the excess morbidity and mortality.

Ashton and colleagues^[178] evaluated perioperative morbidity and mortality in a cohort of patients at a Veterans Hospital. Although vascular surgery was among the highest-risk procedures, amputation was associated with the highest in-hospital cardiac complication rate within this subgroup. This finding most likely represents the more severe nature of the cardiovascular disease in these patients and the prolonged hospitalization needed to facilitate recuperation. As in the study by Goldman and colleagues,^[13] intra-abdominal, thoracic, and orthopedic procedures were associated with increased risk. In another report, Ashton^[178A] evaluated the rate of perioperative myocardial infarction in patients undergoing transurethral resection of the prostate. Despite the high incidence of coronary artery disease in this population, the incidence of perioperative myocardial infarction was only 1%.

Numerous studies have evaluated the perioperative complication rate related to superficial procedures. Backer and coworkers^[179] evaluated the rate of perioperative myocardial reinfarction in patients undergoing ophthalmologic surgery. They demonstrated that the rate of perioperative cardiac morbidity after ophthalmologic surgery was extremely low, even in patients with recent myocardial infarction. Virtually all studies have confirmed that ophthalmologic surgery is very safe under anesthesia.^[180] Warner and colleagues^[181] studied patients undergoing ambulatory surgery and reported no anesthesia-related deaths in more than 45,000 cases.

Eagle and colleagues^[182] evaluated the contribution of coronary artery disease and its treatment on perioperative cardiac morbidity and mortality by surgical procedure. They evaluated patients enrolled in the Coronary Artery Surgery Study who had documented coronary artery disease and who received medical therapy or coronary revascularization and then underwent noncardiac surgery during the subsequent 10-year period. The rates of perioperative myocardial infarction and death were determined, and the surgical procedures were divided into three broad categories. Major vascular surgery was associated with the highest risk, with a combined morbidity and mortality of greater than 10%. Procedures associated with a combined complication rate of 1% to 5% included intra-abdominal, thoracic, and head and neck operations. In all of these cases, patients who had previously undergone coronary artery bypass grafting had a significantly lower combined morbidity and mortality rate than those in the medically treated group. Low-risk procedures included breast, skin, urologic, and orthopedic surgery. These broad groups of surgical procedures were the basis for the definitions of surgical risk published in the guidelines on perioperative cardiovascular evaluation for noncardiac surgery by the American Heart Association/American College of Cardiology Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures^[140] ( Table 24-19 ).