Effect of low vs high intraoperative fraction of inspired oxygen on postoperative organ complications: a systematic review and meta-analysis of randomized controlled trials

Purpose Intraoperative supplemental oxygen may induce postoperative organ complications by aggravating oxidative stress and vasoconstriction. This meta-analysis was to determine whether the higher fraction of inspired oxygen (FiO 2 ) would increase the risk of organ complications among patients under general anesthesia. Methods We performed a systematic literature review for randomized controlled studies among surgical patients receiving ≥ 60% FiO 2 compared with ≤ 40% FiO 2 and meta-analysis of risk ratios (RR) comparing higher FiO 2 against lower for pulmonary, cardiac, neurological, and kidney complications. We systematically explored MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials to December 2024. Results We included 20 qualifying randomized controlled trials with a total of 5,793 patients. Low FiO 2 was associated with less atelectasis (RR, 0.78; 95% CI, 0.63–0.97), lower percentage of atelectasis (mean difference, –1.80; 95% CI, –3.30 to –0.57), and more acute kidney injury (RR, 1.64; 95% CI, 1.15–2.34). No evidence of association with low FiO 2 was found for other complications in this meta-analysis: cardiac complications (RR, 1.15; 95% CI, 0.96–1.53) and delirium (RR, 1.13; 95% CI, 0.87–1.46). Conclusions The current study indicated that lower intraoperative oxygen reduced postoperative incidence and severity of atelectasis but result in more acute kidney injury. More high-quality trials are warranted regarding the optimal fraction of intraoperative inspired oxygen. Registration Prospectively registered at the International Prospective Registry of Systemic Reviews (CRD42023479131).