Predictors of operative mortality in cardiac surgical patients with prolonged intensive care unit duration

Background: Several systems have been developed to predict mortality after intensive care unit (ICU) admission in medical and surgical patients. However, a similar tool specific to cardiac surgical patients with prolonged ICU duration does not exist. The purpose of the current study was to identify independent perioperative predictors of operative mortality among cardiac surgical patients with prolonged ICU duration. Study Design: From 2003 to 2008, a total of 13,105 cardiac surgical patients with ICU durations >48 hours were identified within a statewide database. Perioperative factors, including Society of Thoracic Surgeons Predicted Risk of Mortality, were evaluated. Univariate and multivariate analyses identified significant correlates of operative mortality and their relative strength of association as determined by the Wald chi-square statistic. Results: Mean patient age was 66.8 ± 11.2 years, median ICU duration was 76.5 hours (range 56.0 to 124.0 hours), and mean Society of Thoracic Surgeons predicted risk of mortality was 4.4% ± 6.2%. Among preoperative and operative factors, intra-aortic balloon pump use, patient age, immunosuppressive therapy, hemodialysis requirement, cardiopulmonary bypass time, and heart failure proved to be the strongest correlates of mortality (all p < 0.05) on risk-adjusted multivariate analysis. Type of cardiac procedure had no significant association with mortality after risk adjustment. Among postoperative complications, cardiac arrest, prolonged mechanical ventilation (>24 hours), and stroke were the strongest predictors of risk-adjusted mortality (all p < 0.001). Conclusions: Operative mortality can be predicted by select risk factors for cardiac surgical patients with prolonged ICU duration. Patient age, preoperative intra-aortic balloon pump, postoperative cardiac arrest, prolonged ventilation, and stroke have the strongest association with mortality. Identification of these factors in the perioperative setting can enhance resource use and improve mortality after cardiac surgery.