Frequency, characteristics, and predictors of microbiologically documented nosocomial infections after cardiac surgery

Abstract

Nosocomial infections still remain a serious problem in patients undergoing open heart surgery. The objective of this study was to evaluate frequency, characteristics, and predictors of nosocomial infections after cardiac surgery. This prospective case-control study was conducted in adult patients who underwent open heart surgery with use of extracorporeal circulation over a period of 16 months. Cases were patients who developed microbiologically documented nosocomial infection. Controls were patients who had open heart surgery within a randomly selected two-month period of the study (defined before the start of the study) and did not develop nosocomial infection. Various variables, available before, during or within the first two days after operation, were examined as possible risk factors of nosocomial infections in bi-variable analysis. Then, variables that were found to be statistically associated with nosocomial infections in the bi-variable analysis were included in a multivariable logistic regression model to identify independent risk factors associated with nosocomial infections after open heart surgery. One hundred and seven of 2122 (5.0%) patients developed microbiologically documented nosocomial infection after open cardiac surgery. The majority of nosocomial infections were respiratory tract infections (45.7%) and central venous catheter-related infections (25.2%). All cause hospital mortality was 16.8% in patients with nosocomial infection and 3.5% in the control group (p=0.005). Out of 20 variables studied as possible risk factors, 12 had a statistically significant association with postoperative infection. History of immunosuppression (OR=3.6, 95% CI 1.2-11.0%), transfusion of more than five red blood cell units in both the operating room and during the first ICU postoperative day (OR=21.2, 95% CI 11.9-37.8%), and development of acute renal failure within the first two days after operation (OR=49.9, 95% CI 22.4-111.0%), were found to be independent predictors of nosocomial infections after cardiac surgery in a multivariable logistic regression model. Postoperative nosocomial infections are a considerable problem in cardiac surgery patients. The identified independent predictors of nosocomial infection may be useful in identifying those at high risk for development of such infection in cardiac surgery patients.