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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