Induced Hypothermia Part I

"Arctic Alert"

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.

The Concept

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.

The Results

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.

*All images courtesy of Google searches

1 comment:

Shaggy said...

The hospital I work at has been doing it a while now, and one of I attended one of our Tools and the Talent one day conferences for ED nurses and EMS folks when we were intoduced to the ED protocol, back in 2006, I believe. Since then, there is debate here as to the effectiveness of prehospital therapeatic hypothermia. Right now a trial is being done locally here in Pittsburgh in conjunction with UPMC to determine if we should have a state protocol (we have statewide protocols). Until then, the rest of us have been just using ice packs at pressure points and some services have been purchasing the coolers for the IV fluids. We do not allow medics to give paralytics so we are relegated to just giving benzos for the control of shivering and we need to ensure the BP is adequate or get it there before inducing the hypothermia.
Though I am envious of Wake County, I still think we need the evidence to support actively inducing hypothermia in the prehospital setting.
Funny thing was while training a new EMT on his first arrest, I kept stressing to keep the patient warm. We transported and upon arrival staff were rushing to keep the patient warm, until a few moments later we got ROSC, then there was an immediate reversal to cool the patient.