Myth#9

Frozen Mythbusters: Myth #9 of 13.
There are a variety of myths regarding human response to cold exposure.  These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO.  After posting the thirteen myths, a complete article from the Wilderness Medicine Newsletter will be loaded for anyone interested in all the chilly little details.
Myth #9  
           If a hypothermia victim is found pulseless and breathless, you should immediately begin CPR and access ACLS as soon as possible.
           There are several problems with this myth. The first: is the patient truly breathless and pulseless or simply in a metabolic icebox due to a low core temperature? The human body will continue to shiver, in an effort to rewarm itself, until its core temperature has dropped below 86ºF (30ºC), or until it runs out of blood sugar (fuel to burn) which typically takes many hours.
           As the core temperature drops below 90ºF (32ºC), shivering will occur in short bursts and slowly fail completely around 86ºF (30C). At this point patients go into a state of suspended animation, similar to a hibernating bear. Respirations slow to 3 – 6 per minute, the demand for O2 greatly decreases because of the slowed metabolism, and the heart rate also slows to about 40 beats per minute. Respirations, being very slow and shallow, are difficult to observe; the heart rate has slowed; blood pressure has dropped; and the blood is now 190% thicker than normal making it very hard to palpate a pulse and impossible to hear the heart valves close. So, the patients may appear breathless and pulseless when they are not. They will most likely be curled up into the fetal position to help protect core temperature. If you gently pull on their arm, it will slowly extend, and if you let it go, it will curl back in, because it takes life to contract a muscle.
              If you place a cardiac monitor on these folks, it will show a sinus bradycardia possibly with Osborn, “J” waves. Do not misinterpret this as pulseless electrical activity. The problem is simple: once you begin CPR, you will most likely cause ventricular fibrillation. The cold myocardium is very fragile and does not like to be jostled and bumped around.
              If they go into ventricular fibrillation, you have a major problem because it is very hard to defibrillate a cold heart through a cold chest wall. Additionally, no one knows how cardiac medications behave in these cold temperatures. All medication research is done at normal core temperature so we do not know how these drugs will react at subnormal core temperatures. Circulation is very poor at best, so any ACLS drugs given tend to first accumulate in the central circulation, then are released as a bolus causing a drug overdose as the patient approaches normal core temperature.
           Busted – Do not begin CPR unless you are certain that they are in asystole or ventricular fibrillation. Once you do start CPR, you have now set the clock to definitive care because if they are not there already, they will most likely go into ventricular fibrillation from the chest compressions.
           So, what should you do? First and foremost, DO NOT HURRY. Handle the patient gently as rough handling can precipitate ventricular fibrillation. Protect them from the environment, and place them in a hypothermia wrap. If conscious give them warm, sickly sweet fluids; if unconscious, do gentle, slow rescue breaths, one every 10 seconds. This will provide them with warm (98.6ºF/37ºC), moist (100%) air. Remember that the rescue breaths need to be long and slow as the chest wall is cold and slow to expand.

This blog is powered by the Wilderness Medicine Newsletter, now celebrating 20 years of publication. The WMN is published and distributed online six times each year by TMC Books, and subscriptions cost as little as $10 per year. To find out more, or to subscribe online, click here.