Objective: Most postcesarean infections are caused by anaerobic bacteria. Oxidative killing, an important defense against surgical infections, depends on the oxygen level in contaminated tissue. Among patients undergoing colorectal surgery, perioperative supplemental oxygen decreased infection rates by 50%. We tested the hypothesis that high-concentration inspired oxygen decreases the incidence of surgical site infection in women undergoing cesarean delivery.
Methods: Using a double blind technique, 143 women undergoing cesarean delivery under regional anesthesia after the onset of labor were randomly assigned to receive low- or high-concentration inspired oxygen via nonrebreathing mask during the operation and for 2 hours after. Surgical site infection was defined clinically as administration of antibiotics for postpartum endometritis or wound infection during the initial hospital stay or within 14 days of surgery. Interim statistical analysis was performed after 25% of the planned sample size (143 of 550) accrued using intention-to-treat principle. The stopping rule P value for futility was P>.11 with two planned interim analyses.
Results: Postcesarean infection occurred in 17 (25%, 95% confidence interval [CI] 15-35%) of 69 women assigned to high-concentration oxygen compared with 10 (14%, 95% CI 6-22%) of 74 women assigned to low-concentration inspired oxygen (relative risk 1.8, 95% CI 0.9-3.7, P=.13). The P value exceeded the P value for futility, suggesting these differences were unlikely to reach statistical significance with continued recruitment.
Conclusion: High-concentration perioperative oxygen delivered through a nonrebreathing mask did not decrease the risk of postcesarean surgical site infection.