Regardless of the weather or season, one threat remains ever present when it comes to backcountry skiing: hypothermia.

The human body operates most efficiently at or very near a core body temperature of 37 C (98.6 F), and the threshold for mild hypothermia rests at 35 C (95 F). In the emergency room or the physiology laboratory, this information is readily accessible, but in the field, recognition of hypothermia does not come from a thermometer. Instead, it comes from an array of early and subtle clues.

Cold response is a normal reaction to feeling cold and begins well before the onset of hypothermia. To combat the cold response, your body begins to shiver, which increases heat production from muscle activity. Shivering is a very effective form of heat production but requires a tremendous amount of energy, which comes from food and fluids. If a person’s cold response is inadequate, hypothermia may begin.

Early clues of hypothermia include slurred speech, apathy, a case of the umbles (mumbling, fumbling, stumbling, grumbling), and an impaired ability to perform even simple tasks. Management of a cold skier in the backcountry begins with your ability to recognize an altered mental status. If we catch the early show, hypothermia is much easier to treat—and may even be a field-fix.

Prevention, however, is the best cure. This means being vigilant and remaining aware of your physical state as well as the others’ in your backcountry ski group. Of the utmost importance is adequate hydration and nutrition. In order to maintain our core temperature, we need a constant supply of energy. This can be achieved by consuming both easily digestible simple sugars to kick the body’s thermostat into gear, and then through proteins and fats that will allow for a slow and steady source of fuel. It’s also crucial to dress for the conditions. Heat loss is similar in all areas of the body, however an uncovered head can lose a large percentage of the body’s total heat production. Conversely, wet layers should be changed in order to limit evaporative heat loss, the most energy-efficient form of thermoregulation.

In most backcountry skiing situations, the onset of hypothermia is insidious. It tends to progress slowly and quietly in a patient who has been cold for a long time. Hypothermia is a common complication in trauma patients who have remained immobile, after a fall or an avalanche, for hours while waiting for evacuation. Rescue team members or others in the ski party may also succumb to hypothermia themselves while waiting for assistance or instructions. 

The treatment for these mildly hypothermic patients must remain simple. Our goal is assist the patient in generating their own heat, thus we must give them fuel. If you have a steaming hot tea in your thermos or an ice cold Coca-Cola what should you give your patient? The Coke! This patient needs sugars to fuel their internal fire. Assisting a patient in generating their own internal heat is Just like building a fire. Start with the simple sugars or kindling, then add some carbohydrates, our medium logs, and top that off with the proteins and fats, our large, slow burning logs.

Next, we want to create a hypothermia wrap to trap the heat this patient generates. Rescuers must remove cold wet clothing from the patient and ideally replace it with warm dry clothing. Wrap a tarp around the patient to create an internal vapor barrier, trap in any generated heat, and keep the patient protected and dry. Pack it with insulation via sleeping bags, down jackets, or anything else you have in the field. Note that body-to-body rewarming is no longer encouraged; in fact this just creates two cold patients. After vigorous and uncontrollable shivering generates enough heat that the patient’s mental status begins to return to baseline, it is safe to allow exercise with the goal of continued heat production.

Despite our best efforts, if you are helping a patient who does not warm after repeated attempts or is severely hypothermic, field-rewarming becomes quite challenging. It is best to initiate an evacuation to the hospital where this patient can be rewarmed in a clinical setting. The hypothermia wrap is still essential treatment, however, and should remain in place during evacuation. Transport of this patient must be done gently and carefully in order to avoid cardiovascular collapse.

To learn more, take a wilderness medicine course (click here for a schedule), and check out our other articles about how to build a med kit, how to treat and prevent frostbite, and how to care for a patient post-rescue.