Analgesic efficacy of nitrous oxide in adults in the emergency department: A meta-analysis of randomized controlled trials

Background: Nitrous oxide (N2O) has a rapidly analgesic effect, but evidence regarding its role in managing pain in adults in the emergency department (ED) is conflicting. The purpose of this meta-analysis is to investigate the analgesic efficacy and safety of N2O in adults in ED. Methods: We systematically searched PubMed, the Cochrane Library, Embase, Web of science, China National Knowledge Infrastrusture (CNKI) and Wanfang Database up to August 10th, 2021. Randomized controlled trials (RCTs) were included if they compared N2O/O-2 to placebo or other analgesic methods for management of pain in adults in ED or prehospital. The primary outcome was the analgesic efficacy of N2O. Secondary outcomes included adverse events, satisfaction of patients and the duration of procedure. Results: 14 RCTs with 1751 patients were included. Pooled analysis suggested that N2O had better analgesia than placebo in the pain score (WMD = -3.00, 95% CI = -3.99 to -2.02, P < 0.00001, I-2 = 91%) and the number of patients with pain relief (OR = 6.18, 95% CI = 3.22 to 11.85, P < 0.00001, I-2 = 0%), while there were no significant difference in the pain score (WMD = 0.93, 95% CI = -1.09 to 2.95, P = 0.37, I-2 = 97%) or the number of patients with pain relief (OR = 0.07, 95% CI = 0.00 to 3.47, P = 0.18, I-2 = 86%) between the N2O group and the other analgesic method group. Although N2O did not increase nausea (OR = 1.52, 95% CI = 0.44 to 5.21, P = 0.50, I-2 = 54%) or satisfaction of patients (OR = 1.06, 95% CI = 0.16 to 7.18, P = 0.96, I-2 = 81%), it was associated with higher tendency of vomiting (OR = 6.50, 95% CI = 2.07 to 20.42, P = 0.001, I-2 = 29%) and dizziness (OR = 4.54, 95% CI = 2.27 to 9.09, P < 0.0001, I2 = 26%), and shorter procedure time (WMD = -5.73 min, 95% CI = -10.14 min to -1.32 min, P = 0.01, I-2 = 98%). Conclusions: The present meta-analysis suggested that N2O could provide better analgesia than placebo and similar analgesia to other methods with more vomiting and dizziness in adults in ED. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

This meta-analysis investigated the analgesic efficacy and safety of nitrous oxide (N2O) in managing pain in adults in the emergency department (ED). The results showed that N2O had better analgesia compared to placebo and similar analgesia to other methods. However, N2O use was associated with a higher tendency of vomiting and dizziness.