Friday, February 10, 2012

Ketamine For Acute Pain Control

So, there's effective.  And then there's effective, but insane.  I am aware that low-dose continuous infusions of ketamine are excellent adjunctive therapies to decrease narcotic use in trauma and orthopedic patients, but I have never seen ketamine used in bolus form to treat acute pain in the out-of-hospital setting.

But, that's what we have.  After an initial 5mg IV bolus of morphine, patients were randomized to receive either additional morphine or ketamine boluses - 1 to 5mg of morphine every five minutes, or 10 to 20mg of ketamine every three minutes.  Pain medication was given per protocol until relief or adverse events.  And, the ketamine group was superior - pain scores dropped 5.6 points on the numerical verbal scale with ketamine and 3.2 with morphine.

However, the ketamine group also had a 39% incidence of adverse effects, compared with 14% of the morphine group.  The morphine group had mostly nausea, with one patient exhibiting a change in level of consciousness.  However, the ketamine group had multiple patients with decreased consciousness, disorientation, and emergence phenomena.  So, while the editor capsule summary states "Supplementing out-of-hospital opiods with low-dose ketamine is an effective strategy to mitigate trauma pain" he is technically correct, but the insanity of this strategy is trying to make an evidence-based decision about intracranial imaging after iatrogenically altering your patients prehospital.

What I appreciate best about this paper is how aggressive the paramedics were with treating pain - the patients receiving morphine averaged 14.4mg, with a standard deviation of 9.4mg!  I see my residents ordering 2mg at a time and it drives me nuts.

"Morphine and Ketamine Is Superior to Morphine Alone for Out-of-Hospital Trauma Analgesia: A Randomized Controlled Trial"
www.ncbi.nlm.nih.gov/pubmed/22243959

6 comments:

  1. Definitely agree that bolus dose ketamine for pain control sounds like a misapplication, but I've always thought it would be wonderful to have in the field for the rarer instances of entrapped patients with painful injuries. Yes, you can knock down their pain a bit with opiates, but extricating them is still going to be a miserable experience, and if I were in that position, I would definitely appreciate a dissociative agent to take me out of the moment.
    What's your take on such an indication, and would it mess with your exam in the department too much? As always, thanks.

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  2. What's lovely about medicine is that there's no one-size-fits-all strategy for individual patients - it's the invigorating challenge and the infuriating curse of the profession. We wouldn't make as many mistakes if it were consistent, but it also wouldn't be intellectually rewarding.

    I have no issue with considering the use of analgesic/dissociatives in individual scenarios in which the benefit outweighs the risks. In the case you describe, severe pain vs. potentially confounding assessment of mental status in the Emergency Department (plus the side effects of ketamine) - and for some patients it might be a reasonable course of action.

    For routine use in prehospital pain control, I'm sure we can do better than they did in their morphine cohort - but I'm not sure ketamine is that answer.

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  3. Those are some pretty relaxed morphine protocols for Paramedics! It is also unsurprising given they're not practicing in the US. Australia is not quite like the States in terms of their prehospital setup, as they're also more likely to get a Doc in the field. Some of the nastier effects of ketamine could be assuaged with judicious benzo administration. But I agree it seems odd to use ketamine like that prehospital.

    In NC, where I practice, we're pretty agressive prehospital but we're still 2-4mg morphine with 2mg reboluses. The 2012 protocols are adding weight based fentanyl finally...any sort of real pain control prehospital would be nice in my opinion.

    I'm with Vi--err Medial approach--extrication is a nice use for ketamine prehospital in the US. Also for delayed sequence intubation I'd enjoy having ketamine (a struggling CHF'er or bad asthmatic).

    Good review as always!

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  4. Hi Ryan

    Ketamine as a primary prehospital analgesic is commonplace in some European services, and the London HEMS now has a couple of decades of experience with it. The trick (to avoid the complications seen in the paper you've quoted) is subdissociative doses with a tiny dose of benzo (usually 0.5-2mg midazolam) to prevent dysphoria and nausea.
    I've given it many times myself without to my knowledge being insane, although lack of insight is of course a hallmark of insanity.

    The London guys published a retrospective look at their ketamine use. Methodologically (very) limited, but interesting. They note: "...in the small number of cases in which an oxygen desaturation occurred, there was usually an explanation unrelated to the administration of ketamine and desaturation was never critical. Emergence phenomena were not noted by attending physicians."

    P P Bredmose, D J Lockey, G Grier, B Watts, G Davies
    Pre-hospital use of ketamine for analgesia and procedural sedation
    Emerg Med J. 2009 Jan;26(1):62-4
    http://www.ncbi.nlm.nih.gov/pubmed/19104109

    Cheers mate!

    Cliff Reid
    http://resus.me

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  5. Well! Thanks for the feedback! Seems like prehospital ketamine might not truly be as entertaining an experience as this paper makes it out to be - and only seems crazy to us because of our narrow experience. Perhaps as a sub-dissociative loading dose to decrease the narcotic requirements? I just hate altered trauma patients - I'm a bit of a minimalist, and I like to try to keep the imaging reasonable, but I need a reliable patient to do so.

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  6. Like Cliff Reid said, Ketamine is commonplace as a primary prehospital analgesic. It is also used by the doctor manned air ambulance in Norway, and also coming into paramedic practice as well as for pain control in remote GP ERs. It's a great drug as it is haemodynamically stable, doesn't really depress respiration and has a shorter onset time and duration than morphine, so it's easier to titrate.
    At analgesic doses I've had no problems getting patients to comply and communicate, even if they might tell me they're feeling a little funny. If they get a little too far into a dissociative state, they will emerge again not much later.

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