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HYPOTHERMIA (Part 1)
- Introduction -

It is essential to decrease heat loss AND increase the body's production of heat in a cold environment.

Hypothermia (lower than normal body temperature) does not mean that the body has "frozen" and it is not the same as frostbite. Hypothermia is a serious, life-threatening condition which occurs when the body loses heat faster than it can be generated. Body heat is produced by the metabolism of the food that we eat, the liquids that we drink and, especially, by exercise. Body heat can also be acquired externally from a heat source such as a fire or another warm body. Blankets and sleeping bags will not warm a chilled body, they will only act as an insulator for the heat that is produced naturally be a person's biological processes. This is the reason that people die of hypothermia even when covered with lots of thick blankets.

The normal body temperature of humans is 37 C (98.6 F). The naked human body is able to continuously maintain this body temperature only when the ambient temperature is above 28 C (82 F). Below this temperature, we are dependent on clothing and shelter to insulate us from the environment and to reduce heat loss. It is a frequently unrecognized fact that hypothermia is an immediate risk when the temperature in homes is less than 15.5 C (60 F). People who are more susceptible to becoming victims of hypothermia include children, pregnant women, the elderly, people who are sick or injured and people who are taking drugs or medications. However, strong, healthy, active people in their prime can also fall victim to hypothermia. In both the wilderness and in the urban environment, knowledgeable, intelligent behavior is essential to avoid hypothermia, but preparation may be the most important factor for survival in the cold. The potential of hypothermia is a situation where it is extremely important to "look out for each other."

There are two forms of hypothermia, both of which must be recognized and treated promptly. Although there are a number of characteristic symptoms of hypothermia, a definitive diagnosis can only be confirmed by measuring the victim's body temperature. Unfortunately, most clinical thermometers do not measure a decrease in body temperature below 34.4 C (94 F). In any case, it is more important to define hypothermia by a person's symptomatic condition, rather than by any particular body temperature, and to act rapidly based on that information.

Hypothermia is a progressive condition that can develop rapidly and which becomes increasingly serious as the body temperature decreases. It is important to immediately treat mild hypothermia because mild hypothermia leads to severe hypothermia which frequently results in death. Hypothermia causes physiological, biochemical and hormonal changes which affect the victim's ability to think clearly and rationally. If it is cold and a person is displaying inappropriate behaviors or is stumbling, fumbling, mumbling and grumbling, this person is in trouble and require assistance. Victims may refuse assistance when they obviously require it or they may neglect to help themselves although they appear to be capable of dealing with the situation. Rescuers, friends and relatives should resist the natural reaction to be annoyed and frustrated in the face of this behavior. The failure to act, and uncooperative and irrational behavior are symptoms of hypothermia which are easily mistaken for stubbornness, foolishness, stupidity or "psychological" problems.

Severe hypothermia and cold water immersion are immediate medical emergencies. The victim is incapable of vigorous exercise sufficient to restore normal body temperature. Many victims of severe hypothermia do not survive even when treated in the hospital, but there have been extraordinary accounts of revival of apparently hopeless cases. Nobody should be considered cold and dead until he is warm and dead!

See also:
Part 2: Decreasing Heat Loss
Part 3: Increasing Heat Production
Part 4: Mild Hypothermia and Treatment
Part 5: Severe Hypothermia and Treatment

CC Austin, PhD

© 1998 SAREC - All rights reserved (Updated 98/01/20) http://www.sarec.ca/ice
Contact CC Austin, PhD, to obtain special permission to freely reproduce and distribute this safety bulletin during the current ice storm disaster.
This copyright notice must be included with all reproductions of this safety bulletin. Telephone: (514) 989-3720 Email: caustin@sarec.ca