Thursday, February 25, 2010

Demerol is Not Bad, It Treats Shivering.

2D structure of analgesic drug pethidineImage via Wikipedia
If you have spent anytime with a palliative care team in a hospital you will know of their efforts to essentially blacklist Demerol (meperidine) from use in the hospital.  Some hospitals have removed it or restricted it from the formulary all together.  In medical culture, demerol has been a go to opioid peri-OR and mostly favored by surgeons.  The drug has been purported to be less likely to cause billiary spasm, but this seems to be impacted more by cultural inertia in medicine and bench evidence and not clinical results.

But with the growth of induced hypothermia protocols in resuscitation efforts, palliative care teams are likely to be seeing Demerol to be used as a medication to prevent shivering.

So what is a palliative care team to do?  We don't want a patient to shiver!  Shivering is a symptom and an unpleasant one at that.  And we want control symptoms, right?  Shivering, oddly enough is not in the index of the 4th ed of the Oxford Textbook of Medicine. (Hint: If anyone needs me to write a chapter/pamphlet on shivering for the next edition I will!)

But we know Demerol is likely to cause delirium, myoclonus and seizures, especially in renal patients.  And your induced hypothermia patient may be likely to have renal failure.  So why do we even use Demerol for shivering?

I asked a lot of people in the hospital and no one had a decent explanation besides some versions of :
"It works for shivering."
"We use it in post-op. We always have."
And interestingly when pressed to tell me the second-line anti-shivering medication, the best I got was 'a warm blanket.' (Hopefully that should be first line for shivering.)  So is a potentially dangerous medication like Demerol used for shivering merely based on anecdotal experience and medical cultural inertia?

Treatment of shivering and the larger reduction of extreme vasoconstriction and sympathetic nervous system activation caused by induced hypothermia has been well studied...mostly in animal models.  The reason for shivering is basically a thermoregulatory defense taht needs to be attenuated.  And demerol reduces the shivering threshold, allowing patients to tolerate lower temps without shivering.

So what we do know about meperidine? It is active at the mu and kappa opioid receptors and is anticholinergic.  Different articles cite the anti-shivering effect to be at either the mu-opioid, kappa-opioid or the alpha2-adrenorecptor (anti-cholinergic).  So frankly we do not know how Demerol reduces anti-shivering, but we do have studies in healthy volunteers and anecdotal evidence to suggest it has a role in anti-shivering.

I hate to say more study is needed, and I REALLY don't want to say there is a paucity of data, but now at least we can all talk a little more intellectually about the drug choice for hypothermia protocols when palliative care is consulted.  Maybe I should ask Drew if I can write a Palliative Care Aspects of Hypothermia Protocols EPERC Fast Fact.

And does anyone know the Latin (read Fancy Medical Term) for shivering?

ResearchBlogging.orgDoufas, A. (2003). Dexmedetomidine and Meperidine Additively Reduce the Shivering Threshold in Humans Stroke, 34 (5), 1218-1223 DOI: 10.1161/01.STR.0000068787.76670.A4

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