Hypothermia
Unlike other warm-blooded animals that have a layer of hair to keep them warm, humans need an extra layer of clothing to keep them warm when it's cold outside. Without that extra layer of clothing, more heat escapes from the body than the body can produce. If too much heat escapes, the result is hypothermia.
The cause of hypothermia usually is extended exposure to cold temperatures or a cool, damp environment. Other contributing causes include inadequate clothing and neglecting to adequately cover your extremities, particularly your head — a disproportionate amount of heat is lost through your head.
Hypothermia can happen not just in cold winter weather, when there are low temperatures or low wind chill factors, but under more mild conditions as well. A rain shower that soaks you to the skin on a cool day can lead to hypothermia if you don't move inside to warm up and dry off. If you stay outside, evaporation of the water from your skin further cools your body, dropping your internal temperature. A wind blowing over the wet parts of your body greatly increases evaporation and cooling.
Signs and Symptoms
Hypothermia usually comes on gradually. As the body temperature of a cold-exposed person decreases, impaired consciousness, confusion, or disorientation may occur. Often, people aren't aware that they need medical attention. Common signs to look for are uncontrollable shivering, which is your body's attempt to generate heat through muscle activity, and the "-umbles" — stumbles, mumbles, fumbles and grumbles.
These behaviors may be a result of changes in consciousness and motor coordination caused by hypothermia.
Other signs and symptoms may include:
- Slurred speech
- Abnormally slow rate of breathing
- Cold, pale skin
- Fatigue, lethargy or apathy
Seek immediate medical care for any person who has been exposed to cold air or water and who is shivering, appears disoriented, and shows a lack of coordination, has cold and pale skin, appears tired, and is slurring speech. Try to keep the person warm and dry, preferably indoors or at least out of the wind, until help arrives.
Risk factors
Being in extreme cold, wearing wet clothes — especially in the presence of wind — and being in cold water can all play a part in increasing your chances of hypothermia. People who are elderly, very young, mentally impaired, intoxicated or who have certain health issues are especially vulnerable. In addition, a variety of medications, principally sedative-hypnotics, may predispose users to hypothermia; ethanol and neuroleptic medications particularly increase susceptibility to cold.
- Advanced age. People age 65 and older are especially vulnerable because they may have other illnesses or take medications that can interfere with the body's ability to regulate temperature.
- Very young age. Children usually lose heat faster than adults do. Children have a larger head-to-body ratio than adults do, making them more prone to heat loss through the head. Infants may have a special problem with the cold because they have less efficient mechanisms for generating heat.
- Alcohol and drug use. Alcohol may make your body feel warm inside, but it lowers your body's ability to retain heat. Both alcohol and drugs such as marijuana can keep your blood vessels dilated, restrict your shivering response, impair your judgment and alter your awareness of weather conditions.
- Certain medical conditions. Some health disorders affect the body's ability to respond to cold or to produce heat. Examples include untreated under active thyroid (hypothyroidism), stroke, severe arthritis, Parkinson's disease, trauma, spinal cord injuries, burns, blood vessel or nerve disorders that affect sensation in your extremities (for example, peripheral neuropathy in people with diabetes), dehydration and any condition that limits activity or restrains the normal flow of blood. Older adults are more likely to have one or more of these risk factors.
Prevention
Avoid alcohol consumption and the use of illegal substances, because these may increase your risk of hypothermia.
Before you or your children step out into cold air, remember the advice that follows with the simple acronym COLD:
- C for cover. Wear a hat or other protective covering to prevent body heat from escaping from your head, face and neck. Cover your hands with mittens instead of gloves. Mittens are more effective than gloves because mittens keep your fingers in closer contact with one another.
- O for overexertion. Avoid activities that would cause you to sweat a lot. The combination of wet clothing and cold weather can give you chills.
- L for layers. Wear loose fitting, layered, lightweight clothing. Outer clothing made of tightly woven, water-repellent material is best for wind protection. Wool, silk or polypropylene inner layers hold more body heat than cotton does.
- D for dry. Stay as dry as possible. In the winter, pay special attention to places where snow can enter, such as in loose mittens or snow boots.
