Multicenter validation of a risk index for mortality, intensive care unit stay, and overall hospital length of stay after cardiac surgery

Background — A multicenter population-based study was conducted to develop and validate a risk index for mortality, intensive care unit (ICU) length of stay, and postoperative length of stay after cardiac surgery.

Methods and Results — Data were collected from 13,098 patients undergoing cardiac surgery between April 1, 1991, and March 31, 1993, at all nine adult cardiac surgery institutions in Ontario, Canada. A six-variable risk index (age, sex, left ventricular function, type of surgery, urgency of surgery, and repeat operation) was developed using logistic regression analysis to predict in-hospital mortality, ICU stay in days, and postoperative stay in days after cardiac surgery in a derivation set of 6213 patients who had cardiac surgery during fiscal year 1991 (April 1, 1991, to March 31, 1992). The index predicted mortality, prolonged ICU stay (≥6 days), and prolonged postoperative length of stay (≥17 days) after cardiac surgery with areas under the receiver-operating characteristic (ROC) curve of 0.75, 0.66, and 0.69, respectively, in an independent validation set of 6885 patients who had cardiac surgery during fiscal year 1992 (April 1, 1992, to March 31, 1993). Increasing risk scores were associated with greater mortality rates and longer ICU and postoperative stays at all nine institutions.

Conclusions — Mortality, ICU length of stay, and postoperative length of stay after cardiac surgery can be predicted using a simple six-variable risk index. The index has potential application as a risk stratification tool for comparing patient outcomes and resource use among different hospitals and surgeons.