National surveillance of surgical site infections after coronary artery bypass grafting in Norway: incidence and risk factors

Abstract

Objective: A mandatory national surveillance system for surgical site infections (SSIs) following certain surgical procedures, including coronary artery bypass grafting (CABG), was introduced in Norway in 2005. The objectives of this study were to measure national baseline incidence rates of SSIs after CABG, describe the characteristics of the patients and procedures, and identify possible risk factors for infection. Methods: In 2005–2009, all hospitals that performed CABG were invited to assess all patients undergoing CABG surgery in 3-month periods for SSIs. The hospitals evaluated infection status at discharge and 30 days after surgery by sending post-discharge questionnaires to all patients. We calculated incidence proportions and risk ratios for different risk factors. We applied the National Nosocomial Infection Surveillance (NNIS) risk index to the data. Results: In total, 2440 patients were included. Altogether, 124 sternal and 217 harvest site infections were registered, giving incidence proportions of 5.1% and 8.9%, respectively. Over 95% of infections occurred post-discharge from the hospital. No risk factors were identified. Incidence did not significantly increase with higher NNIS risk index; however, 93% of the patients fell into the same risk category. Conclusions: We have provided a baseline rate for SSIs after CABG procedures in Norway. The results show the importance of post-hospital discharge follow-up. The NNIS risk index did not adequately stratify CABG patients. We recommend that more potential risk variables should be included in the surveillance, such as the European System for Cardiac Operative Risk Evaluation (EuroSCORE), height, weight, and diabetes.