Fraction of Inspired Oxygen During General Anesthesia for Non-Cardiac Surgery: Systematic Review and Meta-Analysis

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 VormfenneJeppe Henriksen, Mathias Karlsson, Ida R. Balleby, Marie S. Rasmussen, Kim Pælestik, Asger Granfeldt, Lars W. Andersen

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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.

Original languageEnglish
JournalActa Anaesthesiologica Scandinavica
Issue number8
Pages (from-to)923-933
Number of pages11
Publication statusPublished - Sept 2022

Bibliographical note

© 2022 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.


  • complications
  • fraction of inspired oxygen
  • general anesthesia
  • meta-analysis
  • outcomes
  • systematic review
  • Anesthesia, General
  • Oxygen
  • Humans
  • Adult
  • Surgical Wound Infection


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