• Stefanie Y Lee and John R Tamale.
• Department of Radiology, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada stefanieylee@gmail.com.
• Emerg Med J. 2023 Sep 1; 40 (9): 660665660-665.

BackgroundNausea and vomiting is a common ED chief complaint. However, randomised trials comparing antiemetic agents to placebo have not demonstrated superiority. This systematic review investigates the efficacy of inhaled isopropyl alcohol (IPA) compared with usual care or placebo in adults presenting to the ED with nausea and vomiting.MethodsWe searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials, other relevant trial registries, journals, and conference proceedings up to September 2022. Randomised controlled trials using IPA to treat adult ED patients with nausea and vomiting were included. The primary outcome was change in severity of nausea, measured by a validated scale. A secondary outcome was vomiting during the ED stay. We used a random-effects model for the meta-analysis, and assessed certainty of evidence using the Grades of Recommendation, Assessment, Development and Evaluation system.ResultsTwo trials comparing inhaled IPA to saline placebo and including a total of 195 patients were pooled for meta-analysis of the primary outcome. A third study comparing a group receiving inhaled IPA and oral ondansetron to another group receiving inhaled saline placebo and oral ondansetron did not qualify for the original registered protocol, but was included in a secondary analysis. All studies were judged to be at low or unclear risk of bias. The pooled mean difference for the primary analysis was a reduction in reported nausea of 2.18 on a 0-10 scale (95% confidence interval (CI) 1.60 to 2.76), favouring IPA over placebo, where the minimum clinically significant difference was defined as 1.5. The evidence level was graded as moderate, due to imprecision from low patient numbers. Only the study included in the secondary analysis assessed the secondary outcome of vomiting, and did not find a difference between intervention and control.ConclusionThis review suggests that IPA likely has a modest effect in reducing nausea in adult ED patients, compared with placebo. Larger multicentre trials are needed, as the evidence is limited by few trials and patients.Prospero Registration NumberCRD42022299815.© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.

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