• Maria Høybye, Peter C Lind, Mathias J Holmberg, Maria Bolther, Marie K Jessen, Mikael F Vallentin, Frederik B Hansen, Johanne M Holst, Andreas Magnussen, Niklas S Hansen, Cecilie M Johannsen, Johannes Enevoldsen, Thomas H Jensen, Lara L Roessler, Maibritt P Klitholm, Mark A Eggertsen, Philip Caap, Caroline Boye, Karol M Dabrowski, Lasse Vormfenne, Jeppe Henriksen, Mathias Karlsson, Ida R Balleby, Marie S Rasmussen, Kim Paelestik, Asger Granfeldt, and Lars W Andersen.
• Research Center for Emergency Medicine, Aarhus University Hospital, Aarhus, Denmark.
• Acta Anaesthesiol Scand. 2022 Sep 1; 66 (8): 923933923-933.

BackgroundControversy exists regarding the effects of a high versus a low intraoperative fraction of inspired oxygen (FiO2 ) in adults undergoing general anesthesia. This systematic review and meta-analysis investigated the effect of a high versus a low FiO2 on postoperative outcomes.MethodsPubMed and Embase were searched on March 22, 2022 for randomized clinical trials investigating the effect of different FiO2 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.ResultsThis review included 25 original trials investigating the effect of a high (mostly 80%) versus a low (mostly 30%) FiO2 . Risk of bias was intermediate for all trials. A high FiO2 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.ConclusionsIn adults undergoing general anesthesia for non-cardiac surgery, a high FiO2 did not improve outcomes including surgical site infections, length of stay, or mortality. However, the certainty of the evidence was assessed as low.© 2022 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.

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