Background: Surgical site infections (SSI) occur despite antimicrobial prophylaxis and increase postoperative morbidity and mortality. This could be caused by an intraoperative decrease in antibiotic serum concentrations such as ampicillin after major abdominal surgery due to blood loss and fluid therapy, which possibly promotes SSI. This hypothesis was tested in the present study.
Methods: This pilot study was performed as a prospective observational trial between March 2018 and May 2019. Ampicillin/sulbactam was administered intravenously during anesthesia induction. Fluid replacement was guided based on hemodynamic variables, including analysis of pulse pressure variation. The primary outcome was ampicillin serum level (ASL), measured after administration and hourly within 4 hours. The incidence of SSI at hospital discharge was the secondary outcome. Linear mixed and logistic regression models were used for statistical analyses.
Results: After screening of 133 adult patients, 129 were enrolled, and 102 completed the study protocol. No correlation was found between the volume of intraoperative fluids and ASL, nor was any association found between ASL and SSI. Based on 5 SSI cases, SSI were associated with higher intraoperative fluid volume. ASL was sufficient to provide intraoperative coverage for all potential bacterial strains.
Conclusion: Intraoperative fluid replacement had no effect on ASL up to 4 hours after ampicillin/sulbactam administration. SSI were within an acceptable range, indicating adequate antimicrobial prophylaxis, so intraoperative control of ASL does not seem necessary. In conclusion, contrary to our initial hypothesis, ASL is not influenced by volume turnover or blood loss during major surgery and therefore does not affect SSI.
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