Immersion Hypothermia

Why is hypothermia dangerous?

Hypothermia may be mild, moderate, or severe. The presentation may range from shivering and piloerection (“goosebumps”), to profound confusion, irreversible coma and death. Significant hypothermia begins at temperatures of 95 degrees F and below. The lowering of the body temperature occurs as the body is robbed of heat by the surroundings. Water conducts body heat away up to 26 times faster than air of the same temperature. Normal body functions slow down with decreasing heart rate, decreasing respiratory and metabolic rate. Thinking is impaired and speech becomes confused. Reflexes are slowed and muscles become stiff and unusable. Then dangerous life-threatening heart rhythms develop which are hard to reverse.

What is a ‘diving reflex’?

On immersion in very cold water, reflex actions occur right away. There is sudden hyperventilation, an involuntary gasp, and a varying amount of diving response follows. The diving response is more evident in the very young (infants and toddlers); it consists of a slowing of the heart beat, a decrease or cessation of respiration and a dramatic change in the circulation of the blood with circulation only to the most inner core of the body, the heart, lungs and brain. The casual observer sees this victim as cold, blue and not breathing. These victims appear dead. Cold water immersion victims have been fully resuscitated when treated carefully with a variety of rewarming techniques ranging from warm blankets to complete cardiopulmonary bypass techniques in major hospitals.

Differences in cooling rates occur depending on the age of the victim, sex, body weight, protection worn, nutritional status, general health, specific diseases, water temperature, length of exposure, areas of exposed heat loss, rough versus calm seas, circumstances of the immersion and the “will to live”.

*Remember: Immersion hypothermia should be considered part of most dive accidents.

The body loses its temperature in a variety of ways: in the water, after removal and during transport. Cold water immersion victims may look dead but may be entirely resuscitatable.

How can hypothermia victims be recognized?



What can be done to assist the hypothermic victim?


The basic goals of early care are to prevent cardiopulmonary arrest, stabilize the core temperature, then carefully transport the victim to definitive medical care.
1. Removethe patient from the cold environment.
2. Check the ABC’s of airway adequacy, breathing and circulation. If acceptable, then we add a “D” as in ABCD: DEGREES – what is the body temperature? A low reading thermometer is commercially available (most clinical thermometers read to 94 degrees F only) and this should be part of an emergency kit. As always, if the patient is not breathing and the heart not beating, standard cardiopulmonary resuscitation (CPR) should be started immediately.
3. Prevent further heat loss. This is done by removing wet clothing, gentle drying of the skin, remove or cut off suits, covering the high heat loss areas of the body, e.g., the head and neck (accounts for 50% of the heat loss), the lateral thorax and groin areas.
4. Gentle handling is a must. As the body rewarms it gets colder first for a short time; this is known as afterdrop.

Why is ‘afterdrop’ so dangerous?

During this period the heart is very vulnerable to developing life threatening rhythm disturbances. Immediately after rescue the victim should be removed horizontally from the water and kept that way. A litter or stretcher should be used to carry the victim since unnecessary exercising, jumping, climbing or exertion may trigger the heart rhythm disturbance.

Victims may deny they are ill and want to decline medical care, or want to climb into ambulances or helicopters on their own. Remember their judgement may be clouded, and yours should prevail.

Afterdrop can be worsened by certain types of “field treatments”, such as a cigarette, a hot cup of coffee and a drink of alcohol, all time-honored treatments. These all prolong the afterdrop and may not help the hypothermic victim recover. They should not be given to hypothermic individuals with core temperatures below 95 degrees F.


Ernest S. Campbell, M.D., FACS

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