This past week our Regional Medical Advisory Committee voted unanimously to suspend our prehospital therapeutic hypothermia guidelines in light of two recent studies.
The first, Effect of prehospital induction of mild hypothermia on survival and neurological status among adults with cardiac arrest: a randomized clinical trial, published in the January 2014 Journal of the American Medical Association, showed that while there was no difference in neurologically intact survival between those patients who were cooled prehospitally and those who were cooled in the hospital, those who were cooled prehospitally were more likely to rearrest and more likely to suffer side effects such as pulmonary edema.
The second study, Targeted Temperature Management at 33 degrees C versus 36 degrees C, published in the December 2013 New England Journal of Medicine, showed that there was no difference in survival between those patients who were cooled to 33 degrees Centigrade and those who were kept normothermic at 36 C.
It is now speculated that it was not necessarily cooling patients that was leading to improvements in survival, but keeping them from getting a fever that is likely the reason for better outcomes.
We have been cooling patients in the field in our area for about five years, but we have lacked any real ability to track our resuscitation rates, much less factor in hypothermia. Some services have been doing it, others partially, others not at all. When i was in the suburban contract town, we carried chilled saline in a cooler. In the city, we have been making do with ice packs and Versed if the BP is okay. In place of ice packs, I have often raided refrigerators for frozen vegetables. I don’t know if we saved any lives or not. Many of our area services and hospitals are joining the CARES registry so hopefully we will be better able to track our cardiac arrest outcomes in the future.
Bottom line for us. Cooling may not be all it has been cracked up to be. The evidence has yet to show a benefit to starting cooling in the field versus waiting to start it in the hospital. And while there is no evidence of benefit to starting cooling prehospitally, there is now evidence of harm. Thus, with that evidence of harm, we are suspending the procedure until there is good evidence of benefit.
I would like to say that we apply this approach to every medication or intervention that we use. We don’t, but we are making strides. Many are aware that there is no evidence that epinephrine improves functional neurological outcomes in cardiac arrest. And that the preponderance of the evidence suggests it may actually cause harm. Given its strong foothold in ACLS, we were unprepared to act to banish epinephrine, but we did vote to alter our epinephrine dosing during cardiac arrest from 1 mg every 3-5 minutes, to 1 mg every 5 minutes.