The Canadian four-centre study of anaesthetic outcomes: III. Are anaesthetic complications predictable in day surgical practice?

To understand better the factors important to the safety of anaesthesia provided for day surgical procedures, we analyzed the intraoperative and immediate postoperative course of patients at four Canadian teaching hospitals' day treatment centres. After excluding those who received only monitored anaesthesia care, there were 6,914 adult (non-obstetrical) patients seen over a twelve-month period in 1988-89. The rate of adverse outcome consequent to their care was identified by a comprehensive surveillance system which included review of anaesthetic records (four hospitals) and follow-up telephone calls (two hospitals). The relationship between adverse events and preoperative factors was determined by using a multiple logistic regression analysis that included age, sex, duration of the procedure and the hospital care. There were no deaths during the study period and major morbid events were infrequent. Patient preoperative disease was predictive of some intraoperative events relating to the same organ system, but not to events in the PACU. Some unexpected relationships emerged including preoperative hypertension being related to a greater risk of difficult intubation, and neurological disease to perioperative cardiac abnormalities. Patients judged obese, or inadequately fasted, were found to experience a greater rate of recovery problems as well as discomfort. While the low response rate (36%) to the telephone interviews created a sampling bias, the high rate of patient dissatisfaction among those reached is disconcerting. We conclude that day surgical patients with preoperative medical conditions, even when optimally managed, are at higher risk for adverse events in the perioperative period.