Figure 24-3 Timing of perioperative events in patients undergoing ambulatory surgery. Many of the events occur within the first 48 hours and probably are related to the stress of surgery. A subset of events occurring after this period may be related to background event rates. The overall rate of morbidity was lower than expected for a similar cohort of age-matched nonsurgical patients. (From Warner MA, Shields SE, Chute CG: Major morbidity and mortality within 1 month of ambulatory surgery and anesthesia. JAMA 270:1437, 1993.)