Does a gentamicin-impregnated collagen sponge reduce sternal wound infections in high-risk cardiac surgery patients?

OBJECTIVES Sternal wound infections occurring after cardiac surgery have a critical impact on morbidity, mortality and hospital costs. This study evaluated the efficacy of a gentamicin-collagen sponge in decreasing deep sternal-wound infections in high-risk cardiac surgery patients. METHODS We conducted a quasi-experimental single-centre prospective cohort study in diabetic and/or overweight patients undergoing coronary-artery bypass surgery with bilateral internal mammary artery grafts. The end-point was the rate of reoperation for deep sternal wound infection. The period from January 2006 to October 2008, before the introduction of the gentamicin sponge, was compared with the period from November 2008 to December 2010. RESULTS Of 552 patients (median body mass index, 31.5; 37.7% with diabetes requiring insulin), 68 (12.3%) had deep sternal wound infections. Reoperation for deep sternal wound infections occurred in 40/289 (13.8%) preintervention patients and 22/175 (12.6%) patients managed with the sponge. Independent risk factors were female sex and longer time on mechanical ventilation, but not use of the sponge (adjusted odds ratio, 0.95; 95% confidence interval, 0.52-1.73; P = 0.88). The group managed with the sponge had a higher proportion of gentamicin-resistant micro-organisms (21/27, 77.8%) compared with the other patients (23/56, 41.1%; P < 0.01). The median time to reoperation for wound infection was higher with the sponge (21 vs 17 days, P < 0.01). CONCLUSIONS A gentamicin-collagen sponge was not effective in preventing deep sternal wound infections in high-risk patients. Our results suggest that a substantial proportion of wound contaminations occur after bypass surgery with bilateral internal mammary artery grafts.