Supplemental Intraoperative Oxygen and Long-term Mortality: Subanalysis of a Multiple Crossover Cluster Trial

Background Whether supplemental oxygen worsens long-term mortality remains unclear, with contradictory trial results. The authors therefore tested the hypothesis that supplemental oxygen (80% vs. 30%) increases the hazard for long-term mortality. Methods The authors conducted a post hoc analysis of a large multiple crossover cluster trial in which more than 5,000 colorectal surgeries on 4,088 adults were allocated to receive either 30% or 80% inspired oxygen during general anesthesia. The authors assessed the effect of 80% versus 30% target-inspired oxygen on long-term mortality and calculated Kaplan–Meier survival estimates. Analysis was restricted to patients with a home address in Ohio because the authors could obtain reliable vital status information from the Ohio Department of Health (Columbus, Ohio) for them. Results A total of 3,471 qualifying colorectal surgeries performed in 2,801 patients were analyzed, including 1,753 (51%) surgeries in 1,577 patients given 80% oxygen and 1,718 surgeries in 1,551 patients given 30% oxygen. The observed incidence of death after a median of 3 yr was 13% (234 of 1,753) in the 80% oxygen group and 14% (245 of 1,718) in the 30% oxygen group. The estimated hazard ratio for mortality was 0.94 (95% CI, 0.78 to 1.13; P = 0.493). Conclusions In this post hoc analysis of a large, controlled trial, supplemental oxygen did not increase postoperative mortality. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New