Hypothermia

What Is Hypothermia?

Hypothermia is a potentially dangerous drop in body temperature, usually caused by prolonged exposure to cold temperatures. The risk of cold exposure increases as the winter months arrive. But if you're exposed to cold temperatures on a spring hike or capsized on a summer sail, you can also be at risk of hypothermia.

Normal body temperature averages 98.6 degrees. With hypothermia, core temperature drops below 95 degrees. In severe hypothermia, core body temperature can drop to 82 degrees or lower.

How Does Cold Exposure Cause Hypothermia?

During exposure to cold temperatures, most heat loss -- up to 90% -- escapes through your skin; the rest, you exhale from your lungs. Heat loss through the skin happens primarily through radiation and speeds up when skin is exposed to wind or moisture. If cold exposure is due to being immersed in cold water, heat loss can occur 25 times faster than it would if exposed to the same air temperature.

The hypothalamus, the brain's temperature-control center, works to raise body temperature by triggering processes that heat and cool the body. During cold temperature exposure, shivering is a protective response to produce heat through muscle activity. In another heat-preserving response -- called vasoconstriction -- blood vessels temporarily narrow.

Normally, the activity of the heart and liver produce most of your body heat. But as core body temperature cools, these organs produce less heat, in essence causing a protective "shut down" to preserve heat and protect the brain. Low body temperature can slow brain activity, breathing, and heart rate.

Confusion and fatigue can set in, hampering a person's ability to understand what's happening and make intelligent choices to get to safety.

What Are the Symptoms of Hypothermia?

Hypothermia symptoms for adults include:

• Shivering, which may stop as hypothermia progresses (shivering is actually a good sign that a person's heat regulation systems are still active. )
• Slow, shallow breathing
• Confusion and memory loss
• Drowsiness or exhaustion
• Slurred or mumbled speech
• Loss of coordination, fumbling hands, stumbling steps
• A slow, weak pulse
• In severe hypothermia, a person may be unconscious without obvious signs of breathing or a pulse

Hypothermia symptoms for infants include:

• Cold-to-touch, bright red skin
• Unusually low energy

What Causes Hypothermia?

Possible causes of hypothermia include:

Cold exposure. When the balance between the body's heat production and heat loss tips toward heat loss for a prolonged period, hypothermia can occur. Accidental hypothermia usually happens after cold temperature exposure without enough warm, dry clothing for protection. Mountain climbers on Mount Everest avoid hypothermia by wearing specialized, high-tech gear designed for that windy, icy environment.

However, much milder environments can also lead to hypothermia, depending on a person's age, body mass, body fat, overall health, and length of time exposed to cold temperatures. A frail, older adult in a 60-degree house after a power outage can develop mild hypothermia overnight. Infants and babies sleeping in cold bedrooms are also at risk.

Other causes. Certain medical conditions such as diabetes and thyroid conditions, some medications, severe trauma, or using drugs or alcohol all increase the risk of hypothermia.

What Are the Risk Factors for Hypothermia?

People at increased risk for hypothermia include:

• The elderly, infants, and children without adequate heating, clothing, or food
• People with mental illness
• People who are outdoors for extended periods
• People in cold weather whose judgment is impaired by alcohol or drugs

How Is Hypothermia Diagnosed?

Recognizing the symptoms is the first step in diagnosing hypothermia. A specialized thermometer, available in most hospital emergency rooms, can detect very low core body temperatures and confirm a diagnosis.

Temperatures for mild, moderate, and severe hypothermia generally range from:

Mild hypothermia: 90-95 degrees Fahrenheit

Moderate hypothermia: 82-90 degrees Fahrenheit

Severe hypothermia: Lower than 82 degrees Fahrenheit

Because response to hypothermia varies among individuals, temperatures may differ.

What Is the Treatment for Hypothermia?

Hypothermia is a potentially life-threatening condition that needs emergency medical attention.

If medical care isn't immediately available:

• Remove any wet clothes, hats, gloves, shoes, and socks.
• Protect the person against wind, drafts, and further heat loss with warm, dry clothes and blankets.
• Move gently to a warm, dry shelter as soon as possible.
• Begin rewarming the person with extra clothing. Use warm blankets. Other helpful items for warming are: an electric blanket to the torso area and hot packs and heating pad on the torso, armpits, neck, and groin; however, these can cause burns to the skin. Use your own body heat if nothing else is available.
• Take the person's temperature if a thermometer is available.
• Offer warm liquids, but avoid alcohol and caffeine, which speed up heat loss. Don't try to give fluids to an unconscious person.

If the hypothermic person is unconscious, or has no pulse or signs of breathing, call for emergency help right away. CPR (cardiopulmonary resuscitation) should be given immediately if a pulse can’t be felt and there is no sign of breathing. Feel for the pulse for up to a whole minute before starting CPR, because the heart rate may be extremely slow and you should not start CPR if there is any heartbeat present.

CPR should be continued, in the absence of signs of breathing or a pulse, until paramedics arrive or the person is taken to a hospital.

In cases of advanced hypothermia, hospital treatment is required to rewarm the core temperature. Hypothermia treatment may include warmed IV fluids, heated and humidified oxygen, peritoneal lavage (internal "washing" of the abdominal cavity), and other measures. Complications during recovery can include pneumonia, heart arrhythmias, ventricular fibrillation (a dangerous "fluttering" rhythm of the heart), cardiac arrest (a sudden stopping of the heartbeat), and death.

Seek immediate medical help for anyone with hypothermia. Call 911 if you suspect severe hypothermia.

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