Timing of Cefazolin Prophylaxis in Clean Surgery: Prophylaxis Administered After Incision Results in a Higher...

The timing of antibacterial prophylaxis in the hour before incision remains undecided because of inadequate clinical outcome data. The purpose of this study was to determine if the timing of cefazolin prophylaxis in the hour before surgery influences the surgical site infection (SSI) rate in clean procedures.

We conducted a prospective SSI surveillance in 16 Southern Cross Healthcare hospitals in New Zealand, from 2005 through 2023. The timing of cefazolin antibacterial prophylaxis was recorded, in minutes, with respect to incision time. Patients were followed for 30 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. Uni- and multivariable analyses were performed.

A total of 52,368 procedures had the timing of prophylaxis recorded in minutes against incision time. There were 694 (1.3%) SSIs. For all procedures, the lowest SSI rate was for prophylaxis given 21-30 minutes before surgery; however, after multivariate analysis, timing within the hour before incision was not significant. Prophylaxis given after incision had a higher SSI rate, with an odds ratio of 1.8 (95% CI: 1.2-2.8, P = 0.01).

The SSI rates for prophylaxis increased when cefazolin prophylaxis was given after incision, but no optimal time before incision was observed. The results may not be applicable to non-clean procedures or non-cefazolin prophylaxis.