Journal Club – June 2018

Isopropyl Alcohol Nasal Inhalation for Nausea in the Emergency Department: A Randomized Controlled Trial.  Beadle et al.

Study question: Does nasally inhaled isopropyl alcohol reduce nausea when compared to placebo?

Methods: The authors conducted a randomized, double-blind trial with a convenience sample of patients based on chief compliant of nausea/vomiting. Patients were randomized into isopropyl alcohol group vs saline as placebo. Patient nausea and pain were measured with an 11-point verbal numeric response score, and patient satisfaction with treatment was measured by a 5 point Likert scale. The primary outcome was improvement in nausea 10 minutes after start of treatment. Secondary outcomes included improvement in pain and patient satisfaction.

Results: 80 of 84 recruited patients completed the study. At 10 minutes after administration of isopropyl alcohol, the median nausea response scale was 3 in the treatment arm and 6 in the placebo arm. The median patient satisfaction score was 4 in the treatment group and 2 in the placebo group. No significant difference was found between the two groups in terms of pain scale score or the use of rescue antiemetics.

Author’s conclusions:Nasally inhaled isopropyl alcohol effectively decreases nausea in a 10 minute period when compared to placebo.

Discussion: Isopropyl alcohol has been studied in the use of post-operative nausea in anesthesiology literature. It is not well studied in undifferentiated nausea and vomiting as commonly seen in the ED. Commonly used antiemetics have not been shown to be effective when compared to placebo in the existing ED literature. However, this study is limited in that the primary outcome measures symptom relief after only 10 minutes post treatment, and may not affect duration of ED stay or overall patient disposition. The nature of the study may not be perfectly blinded due to the scent of isopropyl alcohol. In addition, the outcomes measured are subjective. Future studies are needed to measure duration of effect and comparison to traditional therapies for nausea in the ED, such as ondansetron.

Bottom line: Isopropyl alcohol inhalation may be an effective short-term therapy for undifferentiated nausea and vomiting in the ED, as shown in this article. Aromatherapy may be particularly useful in terms of the quick onset of action, particularly in a busy ED, instances of difficult IV access, etc. Further research is needed to identify possible adverse effects, investigate the duration of symptom relief, and compare aromatherapy to conventionally used antiemetics.

EBM question: The authors propose two mechanisms to explain the antinausea effect of isopropyl alcohol.  Using the findings in the trial and explain why one of those mechanisms is refuted and the other is supported.

Olfactory distraction and controlled breathing are both proposed mechanisms for the antiemetic effect of inhaled isopropyl alcohol.   Olfactory distraction may be supported by their finding that the inhalation of an agent with a strong scent vs an agent with essentially no scent renders benefit. Because identical technique was used to inhale the two agents, controlled breathing was identically employed in both placebo and isopropyl groups. If controlled breathing had benefit, one should expect to see benefit in the placebo group.

Effect of Use of a Bougie vs Endotracheal Tube and Stylet on First-Attempt Intubation Success Among Patients With Difficult Airways Undergoing Emergency Intubation. Driver et al.

Study question: Does a bougie facilitate first attempt success in orotracheal intubation compared to endotracheal tube + stylet in ED patients with difficult airway characteristics?

Methods: Patients were randomly assigned to undergo initial intubation attempt with or without the use of a bougie. Intubations were performed by PGY3 or PGY4 EM residents, or EM attendings. Patients were eligible for study if 18 years or older, without known distortion of the upper airway (eg, angioedema), pregnant, or prisoners. Intubating physicians were allowed to use a Macintosh blade and either direct or video laryngoscopy, and identified difficulty airway characteristics. The primary outcome was first attempt success in intubation in a patient with at least 1 difficult airway characteristic, defined as airway obstruction, edema, obesity, short neck, small mandible, large tongue, facial trauma, body fluids obscuring view, or C-spine immobilization. Secondary outcomes included first attempt success in all patients, first attempt intubation success without hypoxemia, duration of first attempt, esophageal intubation, and hypoxemia.

Results: 757 patients were included in the randomized study, of which 380 patients had at least one difficult airway characteristic. First attempt intubation success was higher in the bougie group, 96%, compared to the ETT + stylet group, 87%. This is reported as an absolute between-group difference of 14% First attempt success in the bougie group was higher among all patient as well, with an absolute difference of 11%. The duration of the first attempt and incidence of hypoxemia was similar among both groups.

Author’s conclusions:Use of the bougie resulted in significantly higher first-attempt success in patients with a difficulty airway characteristic undergoing intubation in the ED.

Discussion: Limitations of this study include biased blinding, subjective assessment of difficult airway characteristics, use of straight bougie, and postrandomization analysis without stratification of difficult airways. This article suggests that the use of the bougie improves first-attempt success, however, the reporting of results as absolute versus relative difference calls into question the statistical significance of the findings in this paper. In addition, at our particular institution, the first attempt at intubation is generally performed by a less experienced provider compared to those of this study, which limit the generalizability of these results to our residency program specifically.

Bottom line: Interesting idea, but it’s not clear these results will apply in our environment or population.

EBM question: When comparing first attempt success rate between bougie (96%) and ETT+stylet (82%) groups, the authors found that when at least one difficult airway characteristic is present the absolute between-group difference was 14%, with a 95% confidence interval of 8-20%.  The relative difference between groups is 96/82 = 1.2%. Why might the authors choose to report their results as an absolute difference?  What does the confidence interval tell you about the likelihood that the difference they found reflects reality?

In this case, the absolute difference is a bigger and more eye-catching number than relative difference.  This is academic click-bait.  Be aware of the use of absolute and relative differences.  If this study was undertaken with really, really difficult airways, they might have found first-pass success rates of 15% and 1%.  In this case the absolute difference is still 14%, but the relative difference is 15%.

The confidence interval is a mathematical estimation of noise or entropy in the universe.  Because we are only able to study a small sample of the whole population, we are limited in our quest for the true value of a population parameter.  The sample we study is likely to share characteristics with the entire population, but may not perfectly represent the whole.  Thus, the confidence interval is the statistical range of values in which we expect the true population parameter to lie. The 95% confidence level is a statement that the researcher expects that 95% of the time the calculated confidence interval will contain the true value of the sought population parameter.