So the other dayI read the TTM trial (http://www.nejm.org/doi/full/10.1056/NEJMoa1310519?query=featured_home#t=article) with great interest, as cardiac arrest and the post-resuscitation phase have always been among my pet topics.
First of all this is a big trial. Bigger that the previous ones that established hypothermia as a standard of care. Does it obviate those previous results? Absolutely not. Those trials were not 32/33 vs 36 but 32/33 vs “whatever happens.”
Hypothermia makes a lot of sense physiologically, but of course that doesn’t mean that it might not have some harmful side effects that have not yet been clearly delineated (besides the current known hemodynamic ones and relatively benign electrolyte and renal alterations).
However, it is pretty clear that, compared to 33 degrees, 36 does just as well, which leans towards saying that all we have to do is avoid fever, or stay in a very mild hypothermia.
Avoiding secondary injury in brain pathology is key (no desat, no hypotension, and no fever), and in anoxic encephalopathy, it is no different. The key thing is that in this trial, the temperature was controlled – ie it would not be acceptable to do no cooling, and just chase the fever (which is very common) with acetaminophen, which would invariably result in significant time spent above 36 (oops, tylenol didn’t really work, ok lets put the blanket, etc …this is gonna be hours).
So is this the end of aggressive cooling? Not necessarily.
For anyone interested in the topic, I suggest reviewing Peter Safar‘s data on dogs and cold aortic flushes – it is absolutely unbelievable to see dogs who had an arrest, got the cold aortic flush (brain temp below 10 degrees), are left stone cold dead for 45 minutes, then resuscitated and are then able to go around a few days later and do doggie things like run and bark and eat… So I don’t think that cooler isn’t necessarily better, but that we haven’t yet delineated what are the pros and cons of each temperature range or how to get there practically and safely.