12:10am February 7th, 2020 [Facebook]

I would like to talk about what I think might be some common misconceptions when it comes to treating cold stress and mild hypothermia.

When the core temperature of the body rises above its ‘set-point’ of 37C, the brain (more specifically the hypothalamus) causes heat to be sent via the blood to the skin so that it can escape into the atmosphere. When the core temperature drops below this set-point, the brain constricts the blood vessels closest to the skin so that the body stops venting ALL heat. This is an important concept to understand!

The purpose of clothing is insulation. It provides protection from heat loss from without (wind, cold surfaces, moisture), and it traps heat that is being vented via our skin so it can warm our body. Clothing does not GENERATE heat. It has to come from somewhere. So when the body is not exuding heat via the skin, there is no heat for the clothing to trap. The only benefit of the clothing at this point is hopefully preventing cold surfaces and cool air from the atmosphere from cooling the body even further.

So when treating someone experiencing cold stress or mild hypothermia (shivering, numbness in fingertips and toes), consider what you are achieving by wrapping them in blankets. Heat is not coming from their bodies any more for the blankets to trap. If anything, they will hinder efforts to warm them (more on this later). Heat can ONLY come from 3 sources at this point: external heat, muscular contraction, and food and drink.

External heat can come from fire (preferably large, warming fires, using fuel no bigger than your thumb in diameter), hot water bottles, or body heat from another person. Remember that clothes and blankets are insulators! They prevent the penetration of heat from the outside just as effectively as they trap heat coming off of our skin (think of an oven mitt). So make sure they do not prevent heat from actually reaching your patient’s skin and warming them! It may sound counter-intuitive, but as long as there is sufficient shelter from the wind you might well want to remove blankets and some layers clothing so that this can be achieved.

If it is not possible to provide them with shelter and make a fire they must at all costs be prevented from slipping further into more severe hypothermia (the medical term for the life-threatening condition where the body is losing heat faster than it can be replaced). So if fire isn’t an option AND they are best treated in situ, they must be helped to generate heat from their own bodies by means of muscular contraction (this is what shivering is, the body trying to generate some heat through involuntary muscular contraction). This of course ONLY applies to subjects that are mildly hypothermic! They must be fully conscious and lucid, and they must be able to stand and move (absolutely no sign of frostbite in either foot). They may well not WANT to, but they must be helped into a standing position and you must encourage them to walk IN PLACE, stamp their feet, swing their arms and their hips from side to side, push on a tree, etc. This must not be TOO vigorous, but it must be enough to be effective. They should be given something warm and highly-caloric to drink like hot chocolate (something to eat presents a choking hazard). This provides some heat to the core, but the law of thermodynamics dictates it would take more than a gallon to raise the core temperature of a human by just 1 degree). More importantly it provides calories for the body to provide energy to the muscles so the muscles can generate heat.

If they physically can’t move their limbs, or their level of consciousness is altered (they aren’t talking at all, or if they are they aren’t making sense, unaware of their surroundings) this means their core temperature has dropped to a point that they are MODERATELY hypothermic, and the only thing you can do is keep them warm, and CAREFULLY get them to a hospital as soon as possible.

THIS is where the burrito pictured comes in! At this stage transport to medical aid is vital, and they must be protected from further heat loss while being transported.

One item I should mention is the Ready Heat II blanket:


This one-use-only blanket provides its own heat for up to 8 hours, and is a great piece of kit and should be added when packaging a subject (keep in mind the chemicals in these blankets expire in 3-5 years).

If you don’t have these types of warming blankets you could use hot water bottles, or normal water bottles filled with hot water, and covered with a sock to prevent burns. Body heat is another option, and it should be skin to skin, or at least no more than a base-layer of clothing worn, as remember clothes will insulate heat and keep it from your patient.

I hope all this helps illustrate the fact that a subject will not get any WARMER by just lying them down and shoving them in a ‘burrito’ UNLESS of course you provide heat in the form of Ready Heat II warming blankets, or hot water bottles. If you catch them at a stage where you can warm them up and prevent them slipping into moderate hypothermia, wrapping them in a burrito without a heat source inside is NOT the way to go, and if you have a fire going they will not get the heat from it if they are wrapped up in a burrito.

So assess your subject, atmospheric conditions, shelter options, the kit available to you, the distance to medical aid and the method of transport. This will inform where and how you go about warming your patient.