Friday, November 28, 2008

Prognosis after the hypothermia protocol

Neurology has a paper looking at predictors of poor prognosis in patients who receive 'induced mild hypothermia' after cardiac arrests. Called 'the hypothermia protocol' at my institution - this is a procedure which involves cooling patients' core temperature (to ~34 degrees C) after a cardiac arrest to minimize anoxic brain damage. It's been shown to lead to modest improvements in mortality and neurologic recovery. While there are some pretty good criteria to predict very poor neurologic recovery after an anoxic brain injury, this study (a retrospective case series of 37 consecutive patients from a single institution) tries to answer the question of if this has changed after the advent of hypothermia therapy. The patients all were comatose after arrests, survived at least 3 days, and were examined on days 3-6 post arrest (hypothermia is continued only for 12-24 hours so its effects had worn off by the time these patients were examined). Their main outcome was documentation of 'awareness' before hospital discharge (following simple commands).

They found that no patients with unreactive pupils, absent corneal reflexes, or who had myoclonic status epilepticus on days 3-6 regained interactivity. Two of 14 patients who had no motor responses better than extensor posturing on day 3 recovered interactivity before discharge - none of the rest did.

Some cautions about what was not measured: long-term recovery or even how long these people stayed in the hospital (ie were most of the patients with fixed pupils discharged to hospice/palliative units in just a few days, etc.?). That said, this is preliminary (one institution, small N, vague follow-up, no standardized assessment although most of these things are done routinely anyway) but suggestive data that many of the 'standard' predictors of dismal neurologic outcomes after ABIs are still relevent for people who receive hypothermia treatment: absent pupillary and corneal reflexes on day 3, myoclonus status epilepticus. No-better-than-extensor posturing on day 3 is still dismal but perhaps not so much.

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