Sternal wound infection after coronary artery bypass graft surgery: validation of existing risk scores.

OBJECTIVE: Prediction of surgical site infection and mortality after cardiac surgery might allow for interventions to reduce adverse outcomes. We sought to evaluate existing risk scores.

METHODS: We included 809 consecutive patients undergoing coronary artery bypass surgery. Data were collected prospectively. Infections were defined as deep sternal wound infection or mediastinitis by using established criteria and evaluated 60 days after surgical intervention. All-cause mortality was assessed at 30 days and 6 months. We assessed the ability of the National Nosocomial Infections Surveillance risk index, the EuroSCORE, and the Society of Thoracic Surgeons risk score to predict infection and mortality. Discrimination was assessed using the area under the receiver operating curve.

RESULTS: The rate of surgical site infection was 3.6% (29/809 patients). The National Nosocomial Infections Surveillance risk index showed moderate discrimination for infection (area under the receiver operating curve of 0.64) and poor ability to stratify patients into infection risk groups. The EuroSCORE predicted infection and 30-day and 6-month mortality with good discrimination (area under the receiver operating curve of 0.72, 0.78, and 0.77, respectively). Ranking patients by the EuroSCORE and dividing the cohort into 3 roughly equal risk groups yielded an ascending risk for infection of 0.7%, 3.0%, and 7.2%. The preoperative and intraoperative Society of Thoracic Surgeons risk scores showed good discrimination for surgical site infection (area under the receiver operating curve of 0.72 and 0.76, respectively) and excellent discrimination for early and late mortality (area under the receiver operating curve of >0.80). Risk grouping based on the Society of Thoracic Surgeons score yielded an ascending risk for infection of 0.7%, 3.6%, and 6.4%.

CONCLUSIONS: The EuroSCORE and the Society of Thoracic Surgeons risk score can be used for joint risk stratification for surgical site infection and mortality. Both scores performed better than the National Nosocomial Infections Surveillance risk index.