Timing of antibacterial prophylaxis and surgical site infection rates in clean orthopaedic and cardiac surgery.

BACKGROUND

The timing of antibacterial prophylaxis in the hour before incision is unsettled due to inadequate clinical outcome data. The aim of this study was to determine whether the timing of antibacterial prophylaxis in the hour before surgery influences the surgical site infection (SSI) rate in orthopaedic and cardiac surgery procedures.

METHODS

Prospective SSI surveillance was undertaken in all 20 publicly funded hospitals in New Zealand for patients undergoing hip and knee arthroplasties and cardiac surgery procedures. The timing of antibacterial prophylaxis was recorded, in minutes (min), with respect to incision time. Patients were followed for 90 days after surgery. Standard definitions for SSIs were used. The SSI rate with respect to the timing of antibacterial prophylaxis was analysed in 10-minute periods. Cefazolin was the prophylactic antibiotic used in vast majority of patients.

RESULTS

The timing of prophylaxis, recorded in minutes, against incision time was available for 66 292 procedures. For all procedures, the lowest SSI rate was for prophylaxis given 21-30 min before surgery, with higher rates for prophylaxis given ≥ 31 min or more before incision. After multivariable analysis, the risk for SSI increased during the time period but only remained significant when prophylaxis was given 51-60 min before incision (odds ratio 1.7; 95% confidence interval 1.3 to 2.3) or earlier (odds ratio 2.01; 95% confidence interval 1.33 to 3.04).

CONCLUSION

The SSI rates for prophylaxis increased if antibacterial prophylaxis was given more than 50 min before incision. The results may not be applicable to non-clean procedures or non-antibacterial prophylaxis. More outcome data are required before firm recommendations can be made for fine-tuning antibacterial prophylaxis within the 60 minutes before clean surgery.