Violation of prophylactic vancomycin administration timing is a potential risk factor for rate of surgical site infections in cardiac surgery patients: a prospective cohort study

BACKGROUND Intensivists and cardiothoracic surgeons are commonly worried about surgical site infections (SSIs) due to increasing length of stay (LOS), costs and mortality. The antimicrobial prophylaxis is one of the most important tools in the prevention of SSIs. The objective of this study was to investigate the relationship between the timing of antimicrobial prophylaxis administration and the rate of SSIs. METHODS A prospective cohort study was carried out over 1-year period in all consecutive adult patients undergoing elective cardiac surgery. The population was stratified in patients whose antimicrobial prophylaxis administration violated or not the vancomycin timing protocol (i.e., when the first skin incision was performed before the end of vancomycin infusion). To compare SSI rates, the cohort was further stratified in patients at low and high risk of developing SSIs. RESULTS Over the study period, 1020 consecutive adult patients underwent cardiac surgery and according to study inclusion criteria, 741 patients were prospectively enrolled. A total of 60 SSIs were identified for an overall infection rate of 8.1%. Vancomycin prophylaxis timing protocol was violated in 305 (41%) out of 741 enrolled patients. SSIs were observed in 3% of patients without violation of the antimicrobial prophylaxis protocol (13/436) compared with 15.4% of patients with a violation of the timing protocol (47/305) (P < 0.0001). Patients at low risk with protocol violation had a higher occurrence of SSIs (P = 0.004) and mortality (P = 0.03) versus patients at low risk without protocol violation. Similarly, patients at high risk with protocol violation had a higher occurrence of SSIs (P < 0.001) and mortality (P < 0.001) versus patients at high risk without protocol violation. The logistic regression analysis showed that internal mammary artery use (P = 0.025), surgical time (P < 0.001), intensive care unit (ICU) LOS (P = 0.002), high risk of developing SSIs (P < 0.001) and protocol violation (P < 0.001) were risk factors for SSI occurrence as well as age (P = 0.003), logistic EuroSCORE (P < 0.001), ICU LOS (P < 0.001), mechanical ventilation time (P < 0.001) and protocol violation (P < 0.001) were risk factors for mortality. CONCLUSIONS This study showed that violation of the timing of prophylactic vancomycin administration significantly increased the probability of SSIs and mortality from infectious cause in cardiac surgery patients.