Timing of Antibiotic Prophylaxis Prior to Abdominal Surgery Has No Impact on Infectious Complications: A Retrospective Matched Cohort Study.

Abstract

To evaluate the impact of perioperative antibiotic prophylaxis (PAP) timing on postoperative infectious complications in abdominal surgery. Current guidelines advocate strict adherence to predefined PAP timing, yet evidence on its optimal window remains inconclusive. This single-center, retrospective matched cohort study, conducted at a high-volume university hospital in Germany (2013-2018), included 1,193 patients undergoing open elective CDC II-III abdominal surgeries. PAP timing was categorized as "on time" (OT: ≥30 m before incision) or "not on time" (NT:<30 m before incision). Propensity score matching (PSM) was applied to both the real-world (RW) cohort and optimized group (10-39 m NT, or 40-69 m OT, excluding infusion time). The primary outcome was the incidence of in-hospital postoperative infectious complications. Of 1,193 patients, 750 (62.9%) received NT and 443 (37.1%) OT-PAP. Infectious complications occurred in 196 patients (16.4%; 229 events), with 41.9% of infection-causing organisms resistant to PAP. Despite matching, differences in ASA grade, malignancy, procedure type, and duration remained. Multivariable analysis identified procedure duration as independent predictor of surgical site infections. PAP timing did not significantly affect outcomes in RW, RW-PSM, or optimized-PSM cohorts, though fewer complications occurred with OT in procedures >200 minutes. Antimicrobial resistance did not alter observed associations. PAP timing did not significantly affect in-hospital infectious complications following elective open abdominal surgery, and antimicrobial resistance did not confound this association. A rigid time-based approach may be less critical than assumed, warranting individualized strategies based on procedure length and resistance profiles.