Patients and method. A series of 677 patients were studied prospectively in terms of 12 physiological factors prior to surgery and six surgical factors assessed postoperatively. The morbidity and mortality of the series was recorded and the predictable morbidity and mortality rates were calculated using the POSSUM system.
Results. Of the 677 patients studied, 184 (27.2%) underwent emergency surgery and 493 (72.8%) had elective surgery. The mean physiological score was 15.27 points (range: 12 to 40 points), while the mean surgical score was 8.94 points (range: 6 to 33 points). Postoperative morbidity was detected in 126 patients (18.6%) and 17 patients (2.5%) died during the postoperative period. According to the predictive formulas of the POSSUM system, 112 patients (16.55%) should present postoperative morbidity and 18 (2.61%) should die. There were no statistically significant differences. There was only one case of overprediction.