Background: Nitrous oxide (N 2 O) is a common adjuvant to general anaesthesia. It is also a potent greenhouse gas and causes ozone depletion. We sought to quantify the influence of N 2 O as an adjuvant to general anaesthesia on postoperative patient outcomes.
Methods: We searched Medline, EMBASE, and Cochrane Central for works published from inception to July 6, 2023. RCTs comparing general anaesthesia with or without N 2 O were included. Risk ratios (RRs) and standardised mean differences (SMDs) were calculated, along with 95% confidence intervals (CIs), using a random-effects model. Outcomes were derived from the Standardised Endpoints for Perioperative Medicine (StEP) outcome set. Primary outcomes were mortality and organ-related morbidity, and secondary outcomes were anaesthetic and surgical morbidity.
Results: Of 3305 records, 179 full-text articles were assessed, and 71 RCTs, totalling 22 147 patients, were included in the meta-analysis. Addition of N 2 O to general anaesthesia did not influence postoperative mortality or most morbidity outcomes. N 2 O increased the incidence of atelectasis (RR 1.62, 95% CI 1.24 to 2.12) and postoperative nausea and vomiting (RR 1.27, 95% CI 1.15 to 1.40), and decreased intraoperative opioid consumption (SMD -0.19, 95% CI -0.35 to -0.04) and time to extubation (MD -2.17 min, 95% CI -3.32 to -1.03 min).
Conclusions: N 2 O did not influence postoperative mortality or most morbidity outcomes. Considering the environmental effects of N 2 O, these findings confirm that current policy recommendations to limit its use do not affect patient safety.
Systematic Review Protocol: PROSPERO CRD42023443287.
(Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)