The effect of high perioperative inspiratory oxygen fraction for abdominal surgery on surgical site infection: a systematic review and meta-analysis

Guidelines from the World Health Organization strongly recommend the use of a high fraction of inspired oxygen (FiO 2 ) in adult patients undergoing general anesthesia to reduce surgical site infection (SSI). However, previous meta-analyses reported inconsistent results. We aimed to address this controversy by focusing specifically on abdominal surgery with relatively high risk of SSI. Medline, EMBASE, and Cochrane CENTRAL databases were searched. Randomized trials of abdominal surgery comparing high to low perioperative FiO 2 were included, given that the incidence of SSI was reported as an outcome. Meta-analyses of risk ratios (RR) were performed using a fixed effects model. Subgroup analysis and meta-regression were employed to explore sources of heterogeneity. We included 27 trials involving 15977 patients. The use of high FiO 2 significantly reduced the incidence of SSI (n = 27, risk ratio (RR): 0.87; 95% confidence interval (CI): 0.79, 0.95; I 2 = 49%, Z = 3.05). Trial sequential analysis (TSA) revealed that z-curve crossed the trial sequential boundary and data are sufficient. This finding held true for the subgroup of emergency operations (n = 2, RR: 0.54; 95% CI: 0.35, 0.84; I 2 = 0%, Z = 2.75), procedures using air as carrier gas (n = 9, RR: 0.79; 95% CI: 0.69, 0.91; I 2 = 60%, Z = 3.26), and when a high level of FiO 2 was maintained for a postoperative 6 h or more (n = 9, RR: 0.68; 95% CI: 0.56, 0.83; I 2 = 46%, Z = 3.83). Meta-regression revealed no significant interaction between SSI with any covariates including age, sex, body-mass index, diabetes mellitus, duration of surgery, and smoking. Quality of evidence was assessed to be moderate to very low. Our pooled analysis revealed that the application of high FiO 2 reduced the incidence of SSI after abdominal operations. Although TSA demonstrated sufficient data and cumulative analysis crossed the TSA boundary, our results should be interpreted cautiously given the low quality of evidence. Registration : https://www.crd.york.ac.uk/prospero (CRD42022369212) on October 2022.