Friday, 19 September 2014

Are antiemetics efficacious in the Emergency Department?

Giving antiemetics in the Emergency Department is a very common ritual that we perform without much thought. But it might be surprising to know that there is very little evidence as to their efficacy. Most studies looking at antiemetics have been performed in patients who are post-operative or in those undergoing chemotherapy.

Ironically, conducting a well-designed trial should be a reasonably simple and feasible undertaking. Nausea is a near ubiquitous complaint in the ED and intuitively it should be easy to create a double blind randomized controlled trial with adequate power to make reasonable conclusions.

These authors sought to compare ondansetron 4mg, metoclopramide 20mg and placebo in adult patients in whom the treating doctor thought they needed an antiemetic. There were lots of sensible exclusion criteria. The primary outcome was a reduction of 30mm on a VAS recorded half an hour after drug administration. There were lots of secondary outcomes investigated.

They ended up with 258 patients for analysis. Mean decrease in VAS score was 27mm for ondansetron, 28mm for metoclopramide, and 23 for placebo. This was not statistically significant. The authors state that this study adds weight to the recommendation that drug use not be routine for nausea and to focus on other specific treatments or supportive care.

However, I am not so sure we can make any conclusions that suggest we throw away our antiemetics. This study was powered to find a 30mm reduction in VAS from baseline. Trends clearly favoured the antiemetics over placebo; therefore a larger study with more statistical power could very likely demonstrate a difference.

The authors seemed to down play the importance of the administration of rescue medications as meaningful outcome measure. In reality, this may actually be the most objective outcome measure as it does not rely on self-reporting of nausea. Many less people in the metoclopramide group required rescue medication.

The limitations section rightfully point out that one could easily argue over the doses of drugs chosen in this study. Why not 8mg of ondansetron and 10mg of metoclopramide?

One important aspect not mentioned in the limitations is the effect of placebo. As I have mentioned before, remember that placebo is not “nothing.” It can have substantial physiologic and psychological effect especially when it comes to pain and nausea. It would have been interesting if they had a “nothing” arm.

Is this study practice changing? Definitely not. But it does raise some interesting questions. A study of many more patients would be necessary to make any meaningful conclusions. I won’t throw away my antiemetics quite yet. But perhaps I am kidding myself.


Covering:

Egerton-Warburton D, Meek R, Mee MJ, et al. Antiemetic Use for Nausea in Adult Emergency Department Patients: Randomized Controlled Trial Comparing Ondansetron, Metoclopramide, and Placebo. Ann Emerg Med. 2014;?:1-7 [article in press]




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