Supplemental oxygen and surgical-site infections: an alternating intervention controlled trial

Background: The main defence against bacterial infection is oxidative killing by neutrophils, which requires molecular oxygen in wounded tissues. High inspired-oxygen fractions increase tissue oxygenation. But, whether improving tissue oxygenation actually reduces surgical-site infection (SSI) remains controversial. We therefore tested the primary hypothesis that supplemental oxygen (80% vs 30%) reduces the risk of a 30-day composite of deep tissue or organespace SSI, healing-related wound complications, and mortality. Methods: In an isolated suite of operating rooms, the inspired-oxygen concentration was alternated between 30% and 80% at 2-week intervals for 39 months. The analysis was restricted to patients who had major intestinal surgery lasting at least 2 h. Qualifying operations (5749) were analysed, including 2843 (49%) colorectal resections, 1866 (32%) lower gastrointestinal therapeutic procedures, 373 (6%) small-bowel resections, and 667 (13%) other colorectal procedures. Results: The 80% and 30% oxygen groups were well balanced on all of the demographic, baseline, and procedural variables. The oxygen intervention had no effect on the composite primary outcome or any of its components. The overall observed incidence of the composite outcome was 10.8% (314/2896) in the 80% oxygen group and 11.0% (314/2853) in the 30% group. The estimated relative risk was 0.99 (95% CI: 0.85, 1.14) for 80% vs 30%, P = 0.85. Conclusions: Supplemental oxygen does not prevent major infection and healing-related complications after major intestinal surgery. Clinical trial registration: NCT01777568.