Frostbite is a disorder of the skin and underlying tissues caused by exposure to extreme cold and freezing of tissue.
Frostbite is most likely to affect the face, hands, and feet; however, the shins, knees, and the outer portions of the eyes may also be affected. Freezing of exposed tissues results in the formation of ice crystals inside the cell wall.
Frostbite is most likely to occur among soldiers, people who work outdoors in cold weather, mountain climbers, skiers and other winter sports participants, homeless people, travelers stranded outside in cold weather, and people who live close to the polar regions. In a few cases frostbite is caused by industrial accidents, when workers who must handle liquid nitrogen or other liquefied gases fail to protect their hands or use proper safety equipment. It is estimated that frostbite in North America and northern Europe causes 2.5 hospital admissions per 100,000 people. The true rate is unknown because there is no standardized reporting system for this disorder.
Most frostbite victims are male, but this ratio is thought to reflect occupational choices and interest in outdoor sports rather than a genetic factor.
According to U.S. military statistics, African American male soldiers are four times as likely and African American female soldiers 2.2 times as likely to suffer frostbite as their Caucasian counterparts. Other ethnic and racial groups from warmer climates are also thought to be more likely to suffer frostbite. In addition to race, certain diseases, including diabetes, thyroid disorders, arthritis, and some infections increase a person's risk of developing frostbite during exposure to cold.
Most frostbite victims are middle-aged adults between the ages of thirty-five and fifty; one study found the average age of patients treated for frostbite was forty-one.
Frostbite is caused by exposure of skin and underlying tissues to extreme cold. When the skin is exposed to temperatures at or below 32°F (0°C), the blood vessels in the skin start to constrict. This closing down of the
blood flow in the extremities is the body's protective strategy for preserving normal body temperature in the body core (the heart and other internal organs).
The early stage of frostbite is sometimes called frostnip. Short-term symptoms include loss of feeling or aching pain in the affected part, followed by redness of the skin and tissue swelling. Long-term symptoms include intense pain in the affected part, tingling sensations, cracks in the skin, dry skin, loss of fingernails, joint stiffness, loss of bone or muscle tissue, and increased sensitivity to cold. If left untreated, frostbitten skin gradually darkens and blisters after a few hours. Skin destroyed by frostbite is completely black, looks burned, and may hang loosely from the underlying tissues.
Diagnosis is usually made in the field on the basis of the appearance of the frostbitten parts of the body. Some doctors use a four-degree classification of injuries:
- First-degree: The epidermis (outermost layer of the skin) is reddened, swollen, and may look waxy. There is also a loss of sensation in the affected skin.
- Second-degree: The skin is reddened, swollen, and has formed blisters filled with a clear or milky fluid.
- Third-degree: The blisters are filled with blood and the skin begins to turn black.
- Fourth-degree: The epidermis, dermis, and underlying muscles, tendons, and bones are damaged.
The High Cost of Mountain Climbing
Many famous mountain climbers have lost fingers or toes to frostbite on their expeditions. One of the most tragic cases involved Maurice Herzog (1919–), a French climber who was the first to climb Annapurna, the tenth-highest mountain in the world. Herzog and his fellow climber, Louis Lachenal (1921–1955), lost all of their toes and Herzog most of his fingers as a result of frostbite. The two men had chosen boots that were too thin in order to reach the summit of the mountain as quickly as possible, and Herzog lost his gloves near the summit in a freak accident. The gangrene suffered by both men meant that the expedition's doctor had to amputate their fingers and toes in the field without benefit of anesthesia.
Willi Unsoeld (1926–1979) was an American climber who was famous for getting to the top of Mount Everest in 1963 by a previously untried route even though he was not the first person to reach the summit. Unsoeld developed frostbite in his feet on the way down from the summit of Everest; he lost all his toes and had to spend several months in the hospital. Unsoeld later taught courses at Evergreen State College in Washington. He died in an avalanche while climbing Mount Rainier in March 1979.
A technique that can be used to diagnose the extent of soft-tissue injury after frostbite is technetium scintigraphy. This is a technique in which radioactive technetium is administered intravenously. The radioactive element is taken up differently by healthy and damaged tissue, and
the pattern of “hot spots” and “cold spots” as traced by a scanner allows the doctor to tell whether and where deep tissues have been damaged by frostbite. Scintigraphy can also be used to monitor the recovery of the injured tissues following emergency treatment.
X rays and other imaging studies will not help in diagnosing frostbite but may be used to evaluate the injured person for broken or fractured bones.
Treatment at the scene begins with treating any life-threatening conditions first (internal injuries, etc.). The injured person should have wet clothing replaced with soft dry clothing to prevent further heat loss. Rewarming of the injured part should not be attempted if there is any danger of refreezing; in addition, the injured areas should not be rubbed with either snow or warm hands, as such rubbing may make the injury worse by pushing the ice crystals in the frozen skin through the cell wall. Last, the injured person should not be given alcohol or tranquilizers, as these will increase loss of body heat.
The injured person should then be taken to a hospital emergency room as soon as possible. Treatment begins with fluid replacement to speed up blood flow to the frostbitten tissues. The person will then be rewarmed either with warm wet packs or with a whirlpool bath at 104–108°F (40–42°C). Dry heat is not used for rewarming. The patient may be given morphine for pain. Thawing of frozen tissue takes about twenty to forty minutes, after which the injured part is placed on a sterile sheet, raised, and splinted. Blisters filled with clear fluid can be debrided (surgically removed), but blood-filled blisters are allowed to remain in order to prevent infection.
If frostbitten skin is not treated and its blood vessels are affected, gangrene may set in. Gangrene is the death of soft tissue due to loss of blood supply. It may be treated by surgical removal of the affected tissue if caught early; otherwise, the surgeon may have to amputate the affected digit or limb in part to prevent bacterial infections from spreading from the dead tissue to the rest of the body. People with frostbite may be given penicillin or other antibiotics in the emergency room to prevent infection of the damaged tissue, and ibuprofen to treat inflammation.
It may take from one to three months for the frostbitten tissue to heal. In most cases, amputation can be delayed for that length of time to see whether the affected body part will recover.
Patients with early recovery of sensation in the affected part, blisters filled with clear fluid, and healthy-appearing skin color have a better prognosis for full recovery than those whose skin has turned bluish, has blood-filled blisters, and looks frozen.
People who have recovered from frostbite have an increased risk of another episode during future exposures to cold. They should take extra precautions to dress properly for extreme cold or avoid it altogether. They may also notice that the frostbitten parts of their body are more sensitive to ordinary cold weather, and ache or tingle whenever they are outdoors.
About 65 percent of people with severe frostbite will eventually develop arthritis in the affected hand, foot, or leg.
Frostbite can be prevented by wearing suitable clothing for weather conditions; wise preparation for dressing appropriately includes obtaining a weather forecast before going outdoors for work or recreation in cold weather. The head, neck, and face should be kept covered, and clothing should be loosely fitted and layered rather than tight-fitting; mittens are better than gloves for keeping hands warm. Hands and feet should be kept dry.
Other precautions include increasing calorie and fluid intake when outdoors in cold weather and avoiding the use of alcohol and tobacco. People who are hiking or skiing should use a buddy system in case one person is injured and must be evacuated quickly.
It is difficult to predict whether the incidence of frostbite will increase in the future. Better patient education and more accurate long-term weather forecasting may help; however, many victims of frostbite are alcoholics, drug abusers, and mentally ill homeless people who are unaware of the dangers of exposure to cold or are too intoxicated to move indoors.
Some experimental treatments are being investigated to improve the flow of blood to frostbitten tissue or to treat the inflammation caused by frostbite; however, none of these treatments have been shown to be effective.
SEE ALSO Gangrene; Hypothermia
WORDS TO KNOW
Amputation: Surgical removal of a limb.
Debridement: The medical term for the surgical removal of dead or damaged soft tissue.
Dermis: The layer of skin just below the epidermis.
Epidermis: The outermost layer of the skin.
Gangrene: Decay and death of soft tissue due to loss of blood supply.
Scintigraphy: A technique for detecting the location and extent of soft-tissue injury by injecting a small quantity of a radioactive element and following its distribution in the tissue with a scanner.
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