Fraction of inspired oxygen during general anesthesia for non-cardiac surgery: Systematic review and meta-analysis

Background Controversy exists regarding the effects of a high versus a low intraoperative fraction of inspired oxygen (FiO(2)) in adults undergoing general anesthesia. This systematic review and meta-analysis investigated the effect of a high versus a low FiO(2) on postoperative outcomes. Methods PubMed and Embase were searched on March 22, 2022 for randomized clinical trials investigating the effect of different FiO(2) levels in adults undergoing general anesthesia for non-cardiac surgery. Two investigators independently reviewed studies for relevance, extracted data, and assessed risk of bias. Meta-analyses were performed for relevant outcomes, and potential effect measure modification was assessed in subgroup analyses and meta-regression. The evidence certainty was evaluated using GRADE. Results This review included 25 original trials investigating the effect of a high (mostly 80%) versus a low (mostly 30%) FiO(2). Risk of bias was intermediate for all trials. A high FiO(2) did not result in a significant reduction in surgical site infections (OR: 0.91, 95% CI 0.81-1.02 [p = .10]). No effect was found for all other included outcomes, including mortality (OR = 1.27, 95% CI: 0.90-1.79 [p = .18]) and hospital length of stay (mean difference = 0.03 days, 95% CI -0.25 to 0.30 [p = .84). Results from subgroup analyses and meta-regression did not identify any clear effect modifiers across outcomes. The certainty of evidence (GRADE) was rated as low for most outcomes. Conclusions In adults undergoing general anesthesia for non-cardiac surgery, a high FiO(2) did not improve outcomes including surgical site infections, length of stay, or mortality. However, the certainty of the evidence was assessed as low.