Evaluation of Timing of Antimicrobial Surgical Prophylaxis on Rates of Surgical Site Infections.

Background: Surgical site infections (SSIs) are common healthcare-associated infections, and national guidelines recommend that antimicrobial prophylaxis (AP) be administered 60 min prior to incision. However, there are limited data regarding the "most optimal" time for administration within the 60-min window. Patients and Methods: This was a multicenter, retrospective study of adult (≥18-year-old) patients that underwent an abdominal hysterectomy, colorectal surgery, or craniotomy and received AP within 60 min of incision. Incidence of SSI was compared between patients who received AP 0-30 versus 31-60 min of incision. In addition, a predefined subgroup analysis evaluated incidence of SSI for 15-min intervals within the 60-min timeframe. Results: Of the 277 patients included in the primary analysis, 233 (84.1%) and 44 (15.9%) received AP 0-30 min and 31-60 min prior to incision, respectively. SSIs were documented in 6.0% (14/233) versus 4.5% (2/44) of patients in the primary analysis (p = 0.703). In the secondary analysis, 137 (49.5%), 95 (34.3%), 34 (12.3%), and 11 (4.0%) patients received AP 0-15, 16-30, 31-45, and 46-60 min prior to incision, respectively. There was no difference in incidence of SSIs among the 15-min intervals (4.4% vs. 8.4% vs. 2.9% vs. 9.1%, p = 0.487). Of the 16 patients in this study that incurred a SSI, 5 patients had positive cultures, of which 3 contained bacteria that proved to be resistant to the antibiotic used for AP. Conclusions: The results of our analysis support current national guidelines. Future investigation of different intervals (e.g., AP 15-45 min prior to incision) may be beneficial on the basis of pharmacokinetics of routinely prescribed AP.