Effects of high versus low inspiratory oxygen fraction on postoperative clinical outcomes in patients undergoing surgery under general anesthesia: A systematic review and meta-analysis of randomized controlled trials

To determine whether high perioperative inspired oxygen fraction (FiO2) compared with low FiO2 has more deleterious postoperative clinical outcomes in patients undergoing non-thoracic surgery under general anesthesia. Meta-analysis of randomized controlled trials. Operating room, postoperative recovery room and surgical ward. Surgical patients under general anesthesia. High perioperative FiO2 (≥0.8) vs. low FiO2 (≤0.5). The primary outcome was mortality within 30 days. Secondary outcomes were pulmonary outcomes (atelectasis, pneumonia, respiratory failure, postoperative pulmonary complications [PPCs], and postoperative oxygen parameters), intensive care unit (ICU) admissions, and length of hospital stay. A subgroup analysis was performed to explore the treatment effect by body mass index (BMI). Twenty-six trials with a total 4991 patients were studied. The mortality in the high FiO2 group did not differ from that in the low FiO2 group (risk ratio [RR] 0.91, 95% confidence interval [CI] 0.42–1.97, P = 0.810). Nor were there any significant differences between the groups in such outcomes as pneumonia (RR 1.19, 95% CI 0.74–1.92, P = 0.470), respiratory failure (RR 1.29, 95% CI 0.82–2.04, P = 0.270), PPCs (RR 1.05, 95% CI 0.69–1.59, P = 0.830), ICU admission (RR 0.94, 95% CI 0.55–1.60, P = 0.810), and length of hospital stay (mean difference [MD] 0.27 d, 95% CI -0.28–0.81, P = 0.340). The high FiO2 was associated with postoperative atelectasis more often (risk ratio 1.27, 95% CI 1.00–1.62, P = 0.050), and lower postoperative arterial partial oxygen pressure (MD −5.03 mmHg, 95% CI -7.90– -2.16, P 30 kg/m2, these parameters were similarly affected between the groups. The use of high FiO2 compared to low FiO2 did not affect the short-term mortality, although it may increase the incidence of atelectasis in adult, non-thoracic patients undergoing surgical procedures. Nor were there any significant differences in other secondary outcomes. •The meta-analysis of 26 RCTs with 4991 patients did not show a deleterious effect on clinical outcomes, such as mortality, ICU admission and length of hospital stay following the use of high inspired oxygen concentrations.•While the high inspired oxygen concentrations significantly increased the risk of atelectasis and lowered postoperative PaO2, it did not affect the incidence of pneumonia, respiratory failure, and PPCs.•The results should be interpreted carefully because of the limited numb