Facts:  Hypothermia can and does kill.  Humans are designed to function normally at a body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit).  Hypothermia is defined as a core temperature (internal organs in the body) less than 35 degrees Celsius. People suffer hypothermia when they lose body temperature in cold weather as a result of exposure. This can occur at temperatures that many wouldn’t think of as threatening.  Most hypothermia cases develop in air temperatures between 30 and 50 degrees.  Most people can’t believe that temperatures in this range are dangerous. It is important that you have an understanding of hypothermia and how to treat it.  This is essential to your survival and the survival of others with you.

Cold Kills in Two Distinct Steps – Exposure and Exhaustion

The moment your body begins to lose heat faster than it produces it, you are undergoing exposure.  Two things happen:  1) you voluntarily exercise to stay warm.  That is you consciously decide to engage in exercise to warm up; and 2) your body makes involuntary adjustments to preserve normal temperature in vital organs, and you start shivering.  Either response drains your energy reserves.  The only way to stop the drain is to reduce the degree of exposure.

Heat Loss Causes:

  1. Radiation – loss of heat to the environment due to a temperature gradient (ambient temperature less than 98.6F).
  2. Conduction – occurs through direct contact between objects, molecular transfer of heat energy. NOTE: Water conducts heat away from the body 25 to 30 times faster than air because it has a greater density.  Generally conductive heat loss accounts for only 2% of overall loss; however with wet clothes the loss is increased by five times.
  3. Convection – a process of conduction where one of the objects is in motion. Air moving over your body draws heat away from your body.  Wind chill is an example of convection.
  4. Evaporation – occurs when water is converted from a liquid state to a gas.
  5. Respiration – inspired air raised to body temperature and then exhaled.

Recognizing the Signs and Symptoms of Hypothermia

Impending Hypothermia – Due to physiological, medical, environmental or other factors the person’s core temperature has decreased to 36 degrees Celsius (96.8°F).  The person will increase physical activity in an attempt to warm up.  The skin may become pale, numb and waxy.  Muscles become tense, shivering may begin but can be overcome by activity.  Fatigue and signs of weakness may begin to show.

Treatment: Seek or build a shelter.  Get person out of the cold, windy, wet environment.  Start a fire or get a cook stove going to provide warmth. Provide the person with a hot drink (no alcohol, coffee or tea). Halt further heat loss by insulating the person with extra clothes, etc.  With this treatment a victim should recover quickly.

Mild Hypothermia – The person has now become a victim of hypothermia.  Core temperature (the internal body organs, particularly the heart, lungs, and brain) has decreased to 35°Celcius (95° degrees F).  Uncontrolled intense shivering begins—not under voluntary control. Can’t do complex motor functions (fumbling hands, can’t zip a coat).  Vasoconstriction to the periphery, particularly capillary vessels occurs.  Movements become less coordinated and the coldness is creating some pain and discomfort.

Treatment:  Remove or insulate the victim from the cold environment, keeping the head and neck covered.  This prevents further heat loss and allows the body to re-warm itself.  Provide a warm, sweetened drink (no alcohol, coffee or tea) and some high-energy food. Limited exercise may help to generate some internal heat, but it depletes energy reserves.

Moderate Hypothermia – The victim’s core temperature has now dropped to 33°Celcius (91.4°F).  Shivering slows or stops, muscles begin to stiffen and mental confusion and apathy set in.  Speech becomes slow, vague and slurred, breathing becomes slower and shallow. Drowsiness and strange behavior may occur.

Treatment: Remove or insulate the victim from the cold environment, keeping the head and neck covered. Apply mild heat (comfortable to your elbow) to the head, neck, chest, armpits and groin of the patient.  Use hot water bottles, wrapped Thermos-Pads, or warm moist towels. You may have to continue this treatment for some time. Offer sips of warm sweetened liquids [no alcohol, tea or coffee] (dilute jello is good in that it has glucose and protein) if the patient is fully conscious, beginning to re-warm and able to swallow.  A physician should see patient.

Severe Hypothermia – Core temperature is now below 31°Celcius (87.8°F).  Skin is cold, may be bluish-gray in color, eyes may be dilated. Victim is very weak, displays a marked lack of coordination, slurred speech is present.  May appear to be drunk, denies problem and may resist help. There is a gradual loss of consciousness.  There may be little or no apparent breathing, victim may be very rigid, unconscious, and may appear dead.

Treatment: (1) Hypothermia Wrap provides a shell of total insulation for the patient.  Make sure the patient is dry, and (ideally) has a polypropylene layer to minimize sweating on the skin.  The person must be protected from any moisture in the environment.  Use multiple sleeping bags, wool blankets, wool clothing, Ensolite pads to create a minimum of 4” of insulation all the way around the patient, especially between the patient and the ground. Include an aluminum space blanket to help prevent radiant heat loss, and wrap the entire ensemble in plastic to protect from the wind and water.  (2) Add fuel and fluids. Give warm sugar water for people in severe hypothermia. The stomach has shut down and will not digest food but can absorb water and sugars. Give a diluted mixture of warm water with sugar every 15 minutes. Dilute Jello™ works best since it is part sugar and part protein.  This will be absorbed directly into the blood stream providing the necessary calories to allow the person to re-warm themselves. One box of Jello™ = 400 Kilocalories of heat energy. Do not give full strength Jello even in liquid form as it is too concentrated and will not be absorbed.  (3) Add Heat. Heat can be applied to transfer heat to major arteries—at the neck for the carotid, at the armpits for the brachial, at the groin for the femoral, at the palms of the hands for the arterial arch.  Chemical heat packs such as the Heat Wave™ provide 110°F for 6-10 hours.  Hot water bottles, warm rocks, towels, and compresses can be used.  For a severely hypothermic person, rescue breathing can increase oxygen and provide internal heat.

After Drop – This is a situation in which the core temperature actually decreases during re-warming.  This is caused when peripheral vessels in the arms and legs dilate when they are re-warmed.  This dilation sends this very cold, stagnate blood from the periphery to the core further decreasing the core temperature, which can lead to death.  In addition, this blood also is very acetic which may lead to cardiac arrhythmias and death.  After drop can be best be avoided by not re-warming the periphery.  Re-warm the core only! Do not expose a severely hypothermic victim to extremes of heat.

Hypothermia in Water – Loss of body heat to the water is a major cause of deaths in boating accidents and other incidents resulting in immersion in water. The cause of death may be listed as drowning; but often the primary cause is hypothermia. It should also be noted that alcohol lowers the body temperature around two or three degrees by dilating the blood vessels. Prior to hunting or fishing around cold water, a person should avoid consuming alcohol.

The following chart shows the effects of hypothermia in water:

Water Temperature Exhaustion Survival Time
32.5°F Under 15 minutes Under 15 to 45 minutes
32.5-40°F 15 to 30 minutes 30 to 90 minutes
40-50°F 30 to 60 minutes 1 to 3 hours
50-60°F 1 to 2 hours 1 to 6 hours
60-70°F 2 to 7 hours 2 to 40 hours
70-80°F 3 to 12 hours 3 hours to indefinite
Over 80°F Indefinite Indefinite