If you are in EMS and do any continuing education of your own, or subscribe to one of the few EMS magazines, you have probably heard of induced hypothermia. I first learned of induced hypothermia at a clinical conference in 2007. Brent Myers, the medical director of Wake County EMS was the speaker. This was an Eagles conference topic, so it struck a particular interest with me.
Over the years, since the conception of EMS, cardiocerebral resuscitation has been an evolving concept. Treatments have been tried, researched, and protocols have been written and rewritten. The American Heart Association (AHA) has updated their recommendations multiple times. The aim has been to return spontaneous circulation (give the patient their own pulse back). We have successfully discovered what we think works best. BLS before ALS, more chest compressions with less interruptions (see Why Can't Medics Resuscitate by Rogue Medic). The ResQPod has received a class IIA AHA recommendation, and Amiodarone has become the all-in-one dysrhythmic (selective cardiotoxin, thanks AD). More patients are making it to the hospital with a pulse.
But how many more patients are walking out of the hospital?
Almost none. Well until this revolutionary treatment came. The research is still relatively new in the world of medicine, so as you can imagine, it is still a great debate amongst physicians. The research that we do have shows incredible results. In fact, AHA has been recommending the use of induced hypothermia for a few years now.
Okay, what is it?
The treatment is used in hopes to improve cerebral outcome in a post-arrest patient. The hypothermic state is thought to slow cellular metabolism. This slows cerebral hypoxia, necrosis, and anaerobic metabolism which slows impending acidosis.
Number needed to treat or NNT is simply how many patients it takes to show one with improvement from a specific treatment modality. So if your NNT is 45, as it is with Lopressor (metoprolol), out of 45 STEMI patients treated with Lopressor, only one will show improvement. This is obviously an average and doesn't mean that you can't have two or three of the 45 show improvement.
The NNT for induced hypothermia following return of spontaneous circulation (ROSC) is six. That's right, out of every six patients that have been treated with induced hypothermia, one has walked out of the hospital.
Wake County EMS has done some great research on this topic. Take a look at the graphs below.
The first graph* (above) shows neurological improvement in about 21% more patients when treated with induced hypothermia, and a reduction in mortality of about 22%. Those numbers are incredible.
This second graph* (above) shows an obvious improvement in maintaining ROSC, patients making it to admission, patients being discharged, and neurological improvement.
So why isn't everyone doing this?
The simple answer: It is still a new concept and is not universally accepted despite what research we have.