Timing of vancomycin prophylaxis for cardiac surgery patients and the risk of surgical site infections

Background: Increased incidence of methicillin-resistant Staphylococcus species has required some hospitals to choose vancomycin for surgical prophylaxis. Guidelines for appropriate timing of vancomycin prophylaxis state that the infusion should begin within 120 min before the first surgical incision. However, no studies have investigated the proper timing of vancomycin prophylaxis in relationship to surgical site infections (SSI). The objective of the present study was to assess the effect of vancomycin prophylaxis timing in relation to the first surgical incision on the incidence of SSI. Methods: We prospectively monitored vancomycin prophylaxis timing and incidence of SSI in 2048 patients undergoing coronary bypass graft or valve replacement surgery. The timing of vancomycin was categorized into five groups based on the relation between the start of the infusion and the surgical cut time. Study hypotheses were tested using logistic analysis and further validated using a Heckman two-stage model. Results: The incidence of SSI were lowest in the 176 patients given vancomycin between 16 and 60 min before the surgical incision (3.4%) compared with 15 patients given vancomycin between 0 and 15 min [26.7%; relative risk (RR): 7.8; 95% CI: 2.5-24.7], 888 patients given vancomycin between 61 and 120 min (7.7%; RR: 2.2; 95% CI: 0.99-5.09), 700 patients given vancomycin between 121 and 180 min (6.9%; RR: 2.0; 95% CI: 0.87-4.62) or 269 patients given vancomycin > 180 min (7.8%; RR: 2.3; 95% CI: 0.94-5.56) (P = 0.0119 by chi(2) analysis). Stepwise logistic regression analysis and a Heckman two-stage model confirmed that vancomycin administration between 16 and 60 min before the first surgical incision was associated with the lowest incidence of SSI. Conclusions: Vancomycin administration within 16-60 min before the first surgical incision reduced the risk of SSI in cardiac surgery patients.