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Updated 25 July 2012

Hypothermia

Hypothermia occurs when the body's core temperature drops below 37°C.

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Summary
  • Hypothermia occurs when the body's core temperature drops below 37°C.
  • This typically results from prolonged exposure to cold conditions, especially in damp, wet or snowy weather.
  • Early signs: shivering; listlessness; cold, pale, puffy face; impaired speech and impaired judgment.
  • Later signs: drowsiness, weakness, slow pulse, shallow breathing, confusion, altered behaviour, stumbling, unsteadiness.
  • Move person to warmer area, shield from cold, passive rewarming with space blanket etc., give warm fluids and high energy foods if possible.

What is hypothermia and what causes it?
Hypothermia occurs when the body's core temperature drops below 37°C. This happens when more heat is lost than the body can produce through shivering and muscle contractions.

Hypothermia is the result of prolonged exposure to cold conditions, especially in damp, wet or snowy weather. Inadequate clothing during winter or at night in the wilderness, or falling into cold water, are examples of situations which commonly cause hypothermia. Inactivity rapidly leads to heat loss and this is worse if the person is injured.

Symptoms and signs of hypothermia
Hypothermia has a gradual onset and the affected person might lose heat to a critical level before becoming aware of the problem. Early signs include shivering (shivering stops once body temperature falls to below 32°C); listlessness; a cold, pale, puffy face; slurred or incoherent speech and impaired judgment. This decrease in mental sharpness typically results in someone becoming unaware of the gravity of the situation.

Later signs, indicating severe hypothermia, include an overwhelming drowsiness and weakness, slow pulse and shallow breathing, confusion, altered behaviour such as aggressiveness, stumbling when walking and unsteadiness when standing.

Infants, the very lean and the elderly are at particular risk. Elderly people may become hypothermic at temperatures as mild as 10 to 15°C, particularly if they are malnourished, have heart disease or an underactive thyroid, or if they take certain medications or abuse alcohol.

Hypothermia can be fatal and therefore needs prompt treatment. Severe hypothermia may be difficult to distinguish from death because pulses become very difficult or impossible to feel and breathing may be too shallow to notice.

First aid for hypothermia

  • Call for an ambulance if the person's level of consciousness is dropping, or you have any doubt about the severity of the condition.
  • If possible, move the person to a warmer area, shielded from the cold and wind. Remove wet clothing.
  • Passively re-warm the person by wrapping him in a space blanket, blankets, clothing or newspapers, and cover the head. If outdoors, insulate the person from the ground and lie next to him.
  • If the person is conscious, give warm fluids and high-energy foods, unless he is vomiting. Don't give any alcohol or caffeinated drinks.
  • Keep the person still as movement draws blood away from the vital organs. Don't massage or rub someone with severe hypothermia, or jostle them during transport. (Cold can interfere with the electric conduction system of the heart, making it prone to irregular rhythms which may lead to cardiac arrest.)
  • Do not apply direct heat, such as a hot bath, heating pad or electric blanket. (This is called active re-warming and should not be done unless the person is very far from definitive care, as it carries a risk of burns.)

Prevention of hypothermia

  • If you're going to be doing outdoor sports like hiking, research the conditions first and speak to experienced people who know the area. Ask them what they would recommend in terms of gear and available shelter. As a general rule: take along several layers of warm clothing (layers help trap warmed air) and keep the head, hands and feet covered.
  • Change out of wet clothes as soon as you can. Being wet and in the wind rapidly speeds up heat loss from the body.
  • Take along sufficient food, especially carbohydrates, and snack regularly. It's also important to stay hydrated, even in cold weather.
  • Carry a space blanket; these are available at outdoor and camping shops.

Reviewed by Barry Milner, Instructor, Blue Star Academy of First Aid, BLS National Faculty and First Aid Representative (Resuscitation Council of Southern Africa)

 
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