Common Causes

Exposure to cold air or cold water is the biggest cause of hypothermia. Surprisingly, it doesn’t take extremely cold weather to cause it. The only thing that matters is how cold the body gets. Chatting in the parking lot on a cool night with no coat is enough to reach mild hypothermia if you stand out there long enough. Indeed, the problem with hypothermia is that it creeps up on you.

Mild hypothermia is often not reported or treated on temperate nights because when a patient reaches his tolerance level, he usually goes inside where it’s warm and all is good. A little wind or a little water, however, can make it much worse. An incident in the Philippines demonstrates that even in the tropics, enough wind and rain can cause hypothermia.

If the weather isn’t too cold, the body can stave off hypothermia by creating its own heat. The most obvious way the body does that is by shivering, although there are other metabolic processes using fat that create heat and help avoid hypothermia.

Cold Water Immersion

The fastest cause of hypothermia is immersion in cold water. Water conducts heat away from the body much more quickly than air. Falling into cold water is well known as a medical emergency.

Climbing out of the water with soaked clothes is also a problem. The wet clothing against skin continues to pull heat away. One of the first steps in treating hypothermia is to remove wet clothing, even if it means the patient gets naked. A thin, dry blanket is better than a couple of layers of wet clothing.

However, one study found that falling in the water while clothed might be better. There is a layer of water next to the skin that acts as a thermal layer, trapping heat until the patient starts moving or trying to swim. Researchers were attempting to determine whether or not waiting for help is better than swimming to safety in cold water immersion. As it turns out, falling in with clothes on keeps the patient warmer, but trying to swim out with clothes on is more dangerous due to fatigue.3

Wind Chill Factor

A convection oven cooks faster and more evenly by moving air across the roasting turkey. Cold winds work the same way in reverse. Cold air blowing across the body removes heat faster.

Wind chill isn’t just a trick of the body feeling as if the air is colder; it actually accelerates loss of heat from the body and hastens hypothermia.


The environment isn’t always about the weather. Patients in surgical situations can develop hypothermia for two reasons. First, they’re naked. Typically, surgical patients don’t have much more than a blanket or two to keep them warm in a room often kept cooler than the average home.

Second, their guts are exposed. Skin works as a permeable insulation to keep heat in the body.

When the skin is cut open and the outside air is cooler than body temperature, the internal organs are exposed to outside air and the body is cooled very quickly.

Therapeutic Hypothermia

Not all causes of hypothermia are bad. Therapeutic hypothermia is a medical treatment modality intended to slow down metabolism in order to let healing catch up. Therapeutic hypothermia is mostly used after cardiac arrest resuscitation.

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