Two Trials, 195 Patients, One Pooled Answer: Appraising a Meta-Analysis of Inhaled Isopropyl Alcohol for Emergency Department Nausea
Student Name
RN to BSN Program, Aspen University
N494: Essentials of Nursing Research
Instructor Name
Month Day, Year
Two Trials, 195 Patients, One Pooled Answer: Appraising a Meta-Analysis of Inhaled Isopropyl Alcohol for Emergency Department Nausea
Systematic reviews and meta-analyses sit at the top of most evidence hierarchies because they combine the results of several studies using explicit, reproducible methods. Their position does not guarantee quality. A review built on few or weak studies, or conducted with shortcuts, can give a false sense of certainty. This paper appraises a systematic review and meta-analysis by Lee and Tamale (2023) of inhaled isopropyl alcohol for nausea in adult emergency department patients, the population in the clinical question developed in Module 1. The appraisal uses selected domains of AMSTAR 2, a widely used tool for judging the confidence one can place in a systematic review (Shea et al., 2017).
The Review in Brief
The review asked whether inhaled isopropyl alcohol reduces nausea, compared with usual care or placebo, in emergency department adults whose chief complaint is nausea or vomiting. The authors registered a protocol in PROSPERO, searched MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, trial registries, journals, and conference proceedings through September 2022, and included only randomized controlled trials. Its main endpoint was how much nausea severity changed on a validated scale; the secondary outcome was vomiting during the emergency department stay. Certainty of evidence was rated with the GRADE system (Lee & Tamale, 2023).
Two trials comparing inhaled isopropyl alcohol with saline placebo, with a total of 195 patients, were pooled for the primary analysis. The pooled mean reduction in nausea was 2.18 points on a 0 to 10 scale in favor of isopropyl alcohol (95% CI [1.60, 2.76]), above the minimum clinically important difference of 1.5 that the authors had defined. A third trial, which compared isopropyl alcohol plus ondansetron with saline plus ondansetron, did not meet the registered protocol and was included only in a secondary analysis. The authors graded the evidence as moderate because of imprecision from small numbers and concluded that isopropyl alcohol likely has a modest effect compared with placebo (Lee & Tamale, 2023).
Strengths Against AMSTAR 2
Several critical AMSTAR 2 domains are met. The review was registered in advance, which protects against changing methods after seeing the data (Shea et al., 2017). The search was broad, covering multiple databases, trial registries, and conference proceedings, which reduces the chance of missing unpublished trials. Risk of bias was assessed for each included study, and all were judged at low or unclear risk. Certainty was rated with GRADE, and the authors downgraded it for imprecision rather than overstating it.
The handling of the third trial deserves credit. Because that trial compared two active combinations rather than isopropyl alcohol with placebo, it did not fit the registered question, and the authors kept it out of the primary analysis while reporting it separately. Honoring the protocol when a relevant study does not quite fit is exactly the discipline that registration is meant to enforce.
Limitations
The review's main limitation is the size of its evidence base. Two trials and 195 patients cannot establish how consistent the effect is across settings, and heterogeneity statistics mean little with so few studies. Both pooled trials compared isopropyl alcohol with saline placebo, so the review cannot answer the comparison most relevant to practice: whether isopropyl alcohol is as good as or better than a standard antiemetic. The trials were also short, measuring nausea over minutes rather than hours.
A second limitation comes from the included studies rather than the review. Isopropyl alcohol has a distinctive odor that saline lacks, so patients in the included trials could often tell which treatment they received, and nausea is a subjective outcome. The review's risk-of-bias ratings of low or unclear should be read with that in mind. Finally, the vomiting outcome was assessed in only one trial, which found no difference, so the review offers no evidence that isopropyl alcohol reduces vomiting (Lee & Tamale, 2023). A full AMSTAR 2 appraisal would also confirm, from the full text, whether study selection and data extraction were done in duplicate and whether the list of excluded studies was reported.
Overall Confidence and Implications
Under AMSTAR 2, a review is rated by the number and severity of weaknesses in its critical domains rather than by a total score (Shea et al., 2017). Based on the domains assessed here, this review appears methodologically sound, and the main reason for caution is the thin evidence it had to work with rather than flaws in how it was done. Its conclusion that isopropyl alcohol likely has a modest benefit over placebo is appropriately hedged.
The GRADE rating deserves a closer look, because nurses often read "moderate" as a weak endorsement. In GRADE, moderate certainty means the true effect is probably close to the estimate but could be substantially different. Here the downgrade came from imprecision, not from bias or inconsistency, so readers can be fairly sure which way the effect points and the uncertainty lies mostly in its size. The lower end of the confidence interval, 1.60 points, still exceeds the minimum clinically important difference of 1.5, so even the most pessimistic estimate consistent with the data describes a benefit patients would notice.
For the clinical question, the review supports the idea that inhaled isopropyl alcohol provides quick, clinically meaningful short-term relief compared with doing nothing, which is essentially the situation of a patient waiting in a fast-track area. Combined with a Cochrane review showing faster relief and less need for rescue antiemetics than standard treatment in postoperative patients (Hines et al., 2018), and with the emergency department trial that compared it directly with ondansetron (April et al., 2018), the evidence is consistent in direction. It is not yet strong enough to replace antiemetics, but it is strong enough to consider isopropyl alcohol as a first step offered at triage while evaluation proceeds.
Conclusion
Lee and Tamale's (2023) review is a well-conducted synthesis of a small body of evidence. It was registered, searched broadly, assessed bias, rated certainty honestly, and kept to its protocol. Its conclusions are limited by two trials, 195 patients, a placebo rather than active comparison, short follow-up, and imperfect blinding in the underlying studies. Appraised with AMSTAR 2, it earns reasonable confidence in its methods and appropriate caution about its answer.
References
April, M. D., Oliver, J. J., Davis, W. T., Ong, D., Simon, E. M., Ng, P. C., & Hunter, C. J. (2018). Aromatherapy versus oral ondansetron for antiemetic therapy among adult emergency department patients: A randomized controlled trial. Annals of Emergency Medicine, 72(2), 184-193. https://doi.org/10.1016/j.annemergmed.2018.01.016
Hines, S., Steels, E., Chang, A., & Gibbons, K. (2018). Aromatherapy for treatment of postoperative nausea and vomiting. Cochrane Database of Systematic Reviews, (3), Article CD007598. https://doi.org/10.1002/14651858.CD007598.pub3
Lee, S. Y., & Tamale, J. R. (2023). Isopropyl alcohol inhalation for the treatment of nausea in adult emergency department patients: A systematic review and meta-analysis. Emergency Medicine Journal, 40(9), 660-665. https://doi.org/10.1136/emermed-2022-212871
Shea, B. J., Reeves, B. C., Wells, G., Thuku, M., Hamel, C., Moran, J., Moher, D., Tugwell, P., Welch, V., Kristjansson, E., & Henry, D. A. (2017). AMSTAR 2: A critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both. BMJ, 358, Article j4008. https://doi.org/10.1136/bmj.j4008
How this N 494 Module 5 example is structured
N494 teaches students to critically evaluate research across designs, and in many sections a middle module turns to appraising a systematic review or meta-analysis. Aspen does not publish module deliverables, so follow the prompt and tool your classroom names. This example summarizes the review accurately, judges it against named AMSTAR 2 domains, separates limitations of the review from limitations inherited from its trials, and places its answer within the rest of the evidence gathered for the course's clinical question.
N494 Module 5 questions, answered
What does N494 Module 5 usually ask for?
N494 moves through appraisal of different kinds of evidence, and a middle module commonly focuses on higher-level evidence such as systematic reviews, along with how evidence-based practice is supported in organizations. Aspen does not publish module deliverables, so your classroom's instructions set the exact task.
What is AMSTAR 2?
A critical appraisal tool for systematic reviews of healthcare interventions. It covers items such as protocol registration, search comprehensiveness, duplicate selection and extraction, risk-of-bias assessment and appropriate meta-analysis, and it rates overall confidence based on weaknesses in critical domains rather than a total score.
Can a well-done systematic review still give a weak answer?
Yes. Methods and evidence are separate questions. The sample's review follows sound methods but pools only two trials and 195 patients, so its answer is modest and its certainty moderate. Good appraisals say both things clearly.
Write yours, or have the desk draft it
This paper is an original model document written by our desk, not a submitted student paper and not an official Aspen University document. Read it for the moves, then write your own to the instructions in your classroom. If you want one built to your exact prompt and rubric, the first custom sample is free and arrives in 24 to 48 hours.