How to avoid hypothermia this winter

Avoiding the cold is something most of us try to do, but winter brings prolonged stretches of low temperatures that are difficult to escape. Bundling up, limiting time outdoors and planning ahead for activities like skiing or snowmobiling can all help, but unexpected exposures still happen every year. 

A stalled car, getting caught in the rain or snow , a sudden cold-weather snap or even living in an under-heated home can all cause body temperature to drop faster than many people think. 

When that happens, the risk of hypothermia rises sharply. Although numbers can vary, more than 1,000  hypothermia-related deaths occur annually in the United States, and thousands more nonfatal cases are treated in emergency rooms across the country and beyond.

Here's what hypothermia is, what causes it and how it is typically treated if it affects you or someone you love.

What is hypothermia? 

Hypothermia occurs when the body loses heat faster than it can produce it, causing core temperature to fall below what the body needs to function normally. "Mild cases occur when internal temperature falls to 90 to 95 degrees Fahrenheit (32 to 35 degrees Celsius), moderate cases are when it hits 82 to 90 degrees F (28 to 32 degrees C), severe cases are when internal temperature is in the 77 to 82 degrees F (25 to 28 degrees C) range, and extreme cases are when your temperature falls below 77 degrees Fahrenheit or 25 degrees Celsius," explains Dr. Laleh Gharahbaghian, an emergency medicine physician at Stanford Health Care. Such drops can quickly disrupt how the brain, heart and nervous system function.

Symptoms may be subtle in the early stages. Mild hypothermia "typically presents with rapid heart rate , fast breathing, apathy and sometimes frequent urination," says Dr. Kevin Watkins, an emergency medicine physician at Cleveland Clinic Akron General. 

But as internal temperature continues to fall, shivering may stop altogether – an especially dangerous shift because shivering is one of the body's primary mechanisms for generating heat through involuntary muscle contractions and increased metabolic activity. At that point, "symptoms can escalate to lack of coordination, confusion, unconsciousness and even death by cardiac arrest," says Gharahbaghian. "Severe cases are also often accompanied by frostbite , which can result in additional life- or limb-threatening complications," adds Watkins.

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What causes low body temperature?

Hypothermia develops when environmental or physiological conditions push heat loss beyond what the body can replace. "Prolonged exposure to either cold air or cold water or snow are the primary culprits," says Gharahbaghian. Indeed, water is particularly hazardous because it "conducts heat away from the body much faster than air, even in warm weather," says Watkins. 

Because of this, hypothermia can set in at temperatures well above freezing if a person is wet. Ditto for if a person is inadequately dressed or exposed to wind that strips away the thin insulating layer of warm air near the skin.

Certain medical conditions and environmental factors also increase susceptibility to hypothermia. Endocrine disorders such as hypothyroidism, diabetes or adrenal insufficiency "can impact temperature regulation of your brain," says Gharahbaghian. Malnutrition, dehydration, stroke and spinal cord injuries can similarly impair heat regulation. Low body fat or muscle mass reduces insulation, and age-related physiological changes make both infants and older adults more vulnerable.

Medications such as sedatives that slow metabolism or impair awareness can also interfere with the body's ability to sense cold and mount a protective response. "And substances like alcohol may make you feel warmer but actually accelerate heat loss," adds Watkins.

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How to treat hypothermia 

Regardless of the cause, hypothermia is often treatable, but treatment depends on severity. Care focuses on preventing further heat loss and gradually restoring core temperature, explains Gharahbaghian.

For mild hypothermia, "treatment begins with removing the individual from the cold environment and taking off any wet or cold clothing" before providing warm, dry layers, says Watkins. Offering warm (not hot) fluids if the person is alert and applying blankets or skin-to-skin contact can further help gently raise core temperature. " Providing calories , if the person can safely swallow, is also important, as shivering consumes significant energy," adds Watkins. 

Some of these steps can be taken at home if symptoms are limited to shivering and the person is fully alert. But immediate medical care is critical if shivering stops while still exposed to the cold, confusion sets in or if the person cannot warm up quickly. "Without timely treatment, symptoms of hypothermia can worsen, the core temperature can further decrease and people can lose limbs, have organ failure and die," says Gharahbaghian.

In the hospital, clinicians may use active external rewarming techniques such as heated blankets, forced warm air systems or warmed IV fluids. "If needed, more invasive core temperature measures may be recommended," says Gharahbaghian. "And if extreme hypothermia with severe symptoms occurs, placing tubes in the chest and abdomen to give warmed fluids and in the circulation through cardiopulmonary bypass" may be necessary to stabilize the patient.

But prevention remains the most effective protection. " Wear layers of warm, dry clothing that includes head, hand and feet covering when going into a cold environment," advises Gharahbaghian. It's also important to change out of wet clothes promptly and to "anticipate weather changes, to avoid alcohol and drugs and to stay hydrated and nourished," says Watkins. "Proper hydration and nutrition help your body cope with cold stress more effectively."

This article originally appeared on USA TODAY: What is hypothermia? And how to avoid it this winter