March 24, 2010

     Frostbite occurs when tissues freeze. Most people who get frostbite are males aged 30 to 49 years old. The nose, cheeks, ears, fingers and toes are the most commonly affected body parts.  Everyone is vulnerable to this condition, even people who have lived in cold conditions their whole life.

     When you are exposed to cold, the body reacts by constricting the blood vessels that supply your extremities. This enables your body to send more blood to your vital organs. This can also serve to minimize continued heat loss from your exposed arms and legs. With continued exposure to the cold, the blood vessels to the arms and legs dilate (or widen) for a short period of time, then constrict again. This is your body’s strategy to preserve as much function as possible until you can find warmth. If the cold exposure continues to the point where your body cannot maintain its normal core temperature, and it drops several degrees below normal (hypothermia), then your blood vessels will constrict and remain constricted. This is usually how frostbite begins.

     There are two mechanisms involved in frostbite. The first is the cell damage that can occur when ice crystals form in the space outside of the cells in the body. This can cause water to be lost from the inside of the cell, and the resulting dehydration can lead to the ultimate destruction of the cell. The second mechanism is related to the damage that ice crystals can do to the lining of the blood vessels in the extremities. When the frozen area is re-warmed, these injured blood vessels can leak blood or plasma into the tissues. This impaired circulatory problem causes inflammation, and can seriously impede the healing process.      

     When frostbite is superficial, you may experience numbness, burning, tingling, or itching. The tissues appear white, but if you press on them, they retain some resistance. When frostbite is deep, there is a partial or total loss of all sensation. The area eventually swells up and blood-filled blisters may form. The skin looks white or yellowish, then turns purplish blue as it is re-warmed. Also, the area is hard to the touch and does not offer resistance when you push on it.

     If you suspect frostbite, seek medical care immediately. Keep the affected body part elevated to minimize swelling. Get to a warm area as soon as possible and treat for hypothermia, since it often accompanies frostbite. Apply a dry, sterile bandage, and place cotton between fingers or toes (to prevent rubbing). Never re-warm the affected area if there is any chance it could freeze again. Thawing and refreezing is very harmful to the tissues. Do not rub the frozen area with snow (or anything else), since the friction can cause further tissue damage. Remember that the final amount of tissue destruction depends much more on how long the body part was frozen, and not as much on how low the temperature was. So, rapid transport to a medical facility is essential.

Brian W. Donnelly, M.D.

Dr. Donnelly is a Board Certified Pediatrician at the North Hills Division
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