Thursday, 30 June 2016

IV Ketamine vs. Morphine for analgesia in the ED: an RCT

Here we go again...

This is another small study comparing ketamine to morphine conducted by investigators trying to validate their preconceived notions. The lead author has been encouraging the “opiate free ED” for years and now has his home grown “evidence” to back him up.

Perhaps they believe opiates are agents of evil and should be replaced by a drug related to PCP. Let’s have a look further at this evidence.

This was prospective, randomized, double-blind trial of very much a convenience sample of ED patients with acute pain rated >5 on a NRS. The intervention was a K-hole dose of 0.3mg/kg of ketamine vs. morphine at 0.1mg/kg.

The primary outcome was a reduction of pain at 30 minutes.

They had a whopping 45 patients in each group. Pain scores were very similar at baseline at about 8.5 on the NRS. They went down to approximately 4.0 at the 30 minute mark in both groups.

So ketamine is just as good as morphine for acute pain in the ED. Ring the bells!  

Not so fast.

Observer bias was very likely an issue due to lack of blinding. It is very easy to clinically tell the difference between the effects of ketamine vs. morphine. My guess is most of the K-hole group had nystagmus and were babbling away with the fairies. Whether conscious or not, these authors clearly wanted to prove their point.

It could also be argued that they were comparing ketamine to an inadequate straw-man dose of morphine. This opiate is meant to be titrated to effect. 0.1mg/kg is a good starting dose in most patients whereby about half will have adequate analgesia.

Side effects were of course more common in the ketamine group. Not surprising since previous studies have found rates of up to 80%. To be fair, this study demonstrated lower rates but had investigators not blinded to the study hypothesis.

So what are we to do?

Although not specifically investigated in this study, ketamine for analgesia in the ED is probably fine for patients that cannot get adequate doses of opiates or in those chronically habituated.

We should not be replacing a medication that is well established, well known, effective when titrated appropriately and has a perfectly good reversal agent. This is most certainly not with a drug that has questionable efficacy and has a worse side effect profile.



Covering:

Motov S, Rockoff B, Cohen V, et al. Intravenous subdissociative-dose ketamine versus morphine for analgesia in the Emergency Department: a randomized controlled trial. Ann Emerg Med 2015;66:222-229.




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