Postoperative adverse events of common surgical procedures in the Medicare population

Mortality rates are the most widely used measure in assessing patient outcome from hospitalization. However, they may be an insensitive measure of quality for surgical patients because death is a relatively rare outcome. A random sample of patient data (n = 8126) selected from the Medicare files of seven states was used to identify, through chart abstraction, clinical postoperative complications of surgery that could serve as measures of quality. Four surgical procedures were studied: 1) coronary artery bypass grafting; 2) coronary angioplasty; 3) cholecystectomy; and 4) prostatectomy. Severity at admission was controlled for using severity-of-illness models developed with chart-abstracted data to predict adverse events after these four procedures. 30-day mortality rates ranged from 1.0% to 6.6%, while the prevalence of postoperative adverse events identified from chart review was greater (6.9% to 33.3%). There were significant differences between patients with and without adverse events. For example, coronary artery bypass graft patients with adverse events had prolonged postsurgical lengths of stay (18.5 +/- 13.2 vs. 13.2 +/- 6.2, P less than 0.001) and higher mortality rates (15.2% vs. 2.6%, P less than 0.001). The R-square values using clinical indicators at admission to predict the occurrence of any adverse event ranged from 0.05 to 0.13. Clinically meaningful adverse events of surgery can be successfully identified through chart abstraction and appear to be valid measures of postoperative complications among surgical patients. Severity adjustment at admission only modestly predicts the occurrence of these adverse events.