health

Frostbite is a disorder of the skin and underlying tissues caused by exposure
to extreme cold and freezing of tissue.

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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.

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.