Frostbite

Frostbite Overview

Frostbite occurs when tissues freeze. This condition happens when you are exposed to temperatures below the freezing point of skin.

The condition has long been recognized. A 5000-year-old pre-Columbian mummy discovered in the Chilean mountains offers the earliest documented evidence of frostbite. More recently, Napoleon’s chief surgeon, Baron Dominique Larrey, provided the first description of the mechanisms of frostbite in 1812, during his army’s retreat from Moscow. He also noted the harmful effects of the freeze-thaw-freeze cycle endured by soldiers who would warm their frozen hands and feet over the campfire at night only to refreeze those same parts by the next morning.

Although frostbite used to be a military problem, it is now a civilian one as well. Most people who get frostbite are males aged 30-49 years. The nose, cheeks, ears, fingers, and toes (your extremities) are most commonly affected. Everyone is susceptible, even people who have been living in cold climates for most of their lives.

Frostbite Causes

Your body works to stay alive first and to stay functioning second.

  • In conditions of prolonged cold exposure, your body sends signals to the blood vessels in your arms and legs telling them to constrict (narrow). By slowing blood flow to the skin, your body is able to send more blood to the vital organs, supplying them with critical nutrients, while also preventing a further decrease in internal body temperature by exposing less blood to the outside cold.

  • As this process continues and your extremities (the parts farthest from your heart) become colder and colder, a condition called the hunting response is initiated. Your blood vessels are dilated (widened) for a period of time and then constricted again. Periods of dilatation are cycled with times of constriction in order to preserve as much function in your extremities as possible. However, when your brain senses that you are in danger of hypothermia (when your body temperature drops significantly below 98.6°F), it permanently constricts these blood vessels in order to prevent them from returning cold blood to the internal organs. When this happens, frostbite has begun.

  • Frostbite is caused by 2 different means: cell death at the time of exposure and further cell deterioration and death because of a lack of oxygen.

    • In the first, ice crystals form in the space outside of the cells. Water is lost from the cell’s interior, and dehydration promotes the destruction of the cell.

    • In the second, the damaged lining of the blood vessels is the main culprit. As blood flow returns to the extremities upon rewarming, it finds that the blood vessels themselves are injured, also by the cold. Holes appear in vessel walls and blood leaks out into the tissues. Flow is impeded and turbulent, and small clots form in the smallest vessels of the extremities. Because of these blood flow problems, complicated interactions occur, and inflammation causes further tissue damage. This injury is the primary determinant of the amount of tissue damage you will have in the end.

    • It is rare for the inside of the cells themselves to be frozen. This phenomenon is only seen in very rapid freezing injuries, such as those produced by frozen metals.

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Frostbite Symptoms

A variety of frostbite classification systems have been proposed. The easiest to understand, and perhaps the one that gives the best clues to outcome, divides frostbite into 2 main divisions: superficial and deep.

  • In superficial frostbite, you may experience burning, numbness, tingling, itching, or cold sensations in the affected areas. The regions appear white and frozen, but if you press on them, they retain some resistance.

  • In deep frostbite, there is an initial decrease in sensation that is eventually completely lost. Swelling and blood-filled blisters are noted over white or yellowish skin that looks waxy and turns a purplish blue as it rewarms. The area is hard, has no resistance when pressed on, and may even appear blackened and dead.

  • You will experience significant pain as the areas are rewarmed and blood flow reestablished. A dull continuous ache transforms into a throbbing sensation in 2-3 days. This may last weeks to months until final tissue separation is complete.

  • At first the areas may appear deceptively healthy. Most people do not arrive at the doctor with frozen, dead tissue. Only time can reveal the final amount of tissue damage.

When to Seek Medical Care

A doctor must be able to see and examine the affected area. A simple telephone call is probably not sufficient in all but the mildest cases of cold injury to hands and feet. You need to see a doctor for care.

At the time of initial evaluation, it is very difficult to categorize the injury as superficial or deep, and even more difficult to ascertain the amount of tissue damage. Therefore, all people should be seen by a doctor, who will supervise the rewarming process, attempt to classify the injury, and further guide the treatment process. Someone with frostbite will need evaluation for, and possible treatment of, hypothermia and dehydration.

Exams and Tests

The doctor will take a history in order to gather information on the events of the exposure and the medical condition prior to the cold injury.

  • The doctor will take note of the vital signs, including temperature, pulse, blood pressure, and respiratory rate in order to exclude or treat any immediate life threats such as hypothermia or severe infection.

  • X-rays may be performed, but they probably will be deferred until weeks later when they are more useful to the treatment team.

  • The doctor will collect data in order to classify the injury as superficial or deep and the prognosis as favorable or poor.

    • A good prognosis is heralded by intact sensation, normal skin color, blisters with clear fluid, the ability to deform the skin with pressure, and the skin becoming pink when thawed.

    • Blisters with dark fluid, skin turning dark blue when thawed, and an inability to indent the skin with pressure indicate a poor prognosis.

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Frostbite Treatment - Self-Care at Home

  • First, call for help.

  • Keep the affected part elevated in order to reduce swelling

  • Move to a warm area to prevent further heat loss.

  • Note that many people with frostbite may be experiencing hypothermia. Saving their lives is more important than preserving a finger or foot.

  • Remove all constrictive jewelry and clothes because they may further block blood flow.

  • Give the person warm, nonalcoholic, noncaffeinated fluids to drink.

  • Apply a dry, sterile bandage, place cotton between any involved fingers or toes (to prevent rubbing), and take the person to a medical facility as soon as possible.

  • Never rewarm an affected area if there is any chance it may freeze again. This thaw-refreeze cycle is very harmful and leads to disastrous results.

  • Also, avoid a gradual thaw either in the field or in the transport vehicle. The most effective method is to rewarm the area quickly. Therefore, keep the injured part away from sources of heat until you arrive at a treatment facility where proper rewarming can take place.

  • Do not rub the frozen area with snow (or anything else, for that matter). The friction created by this technique will only cause further tissue damage.

  • Above all, keep in mind that the final amount of tissue destruction is proportional to the time it remains frozen, not to the absolute temperature to which it was exposed. Therefore, rapid transport to a hospital is very important.

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Medical Treatment

  • After initial life threats are excluded, rewarming is the highest priority.

    • This is accomplished rapidly in a water bath heated to 40-42°C (104-107.6°F) and continued until the thaw is complete (usually 15-30 minutes).

    • Narcotic pain medications may be given because this process is very painful.

    • Because dehydration is very common, IV fluids may also be given.
  • After rewarming, post-thaw care is undertaken in order to prevent infection and a continuing lack of oxygen to the area.

    • Small clear blisters are left intact. Large, clear blisters may be removed while bloody ones are often drained but left intact so as not to disturb the underlying blood vessels and to decrease the risk of infection.

    • A tetanus booster is given if needed.
  • People with frostbite are hospitalized for at least 1-2 days to determine the extent of injury and to receive further treatment.

    • Aloe vera cream is applied every 6 hours, and the area is elevated and splinted.

    • Ibuprofen may be given twice per day to combat inflammation and an antibiotic may be given if an infection develops.

    • For deep frostbite, daily water therapy in a 37° to 39°C (98.6° to 102.2°F) whirlpool bath will be performed in order to remove any dead tissue.
  • A number of experimental therapies exist, many of which aim to further treat the inflammation or decreased blood flow seen in frostbite.

Next Steps - Follow-up

Symptoms follow a predictable pathway. Numbness initially is followed by a throbbing sensation that begins with rewarming and may last weeks to months. This is then typically replaced by a lingering feeling of tingling with occasional electric-shock sensations. Cold sensitivity, sensory loss, chronic pain, and a variety of other symptoms may last for years.

The treatment of frostbite is done over a period of weeks to months. Definitive therapy, possibly in the form of surgery, may not be performed for up to 6 months after the initial injury. Therefore, establish a working relationship between you and your doctor that will continue throughout the healing process.

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Prevention

The first step in preventing frostbite is knowing whether you are at increased risk for the injury.

  • Many cases of frostbite are seen in alcoholics, people with psychiatric illness, car accidents or car breakdowns in bad weather, and recreational drug misuse.

  • All of these conditions share the problem of cold exposure and either the unwillingness or inability of a person to remove himself or herself from this threat.

  • Tobacco smokers and people with diseases of the blood vessels also are at increased risk because they have an already decreased amount of blood flow to their arms and legs.

  • Homelessness, fatigue, dehydration, improper clothing, and high altitude are additional risk factors.

Although people don't always know or acknowledge these dangers, many of the dangers can be reduced or prevented.

  • Dress for the weather.

  • Layers are best, and mittens are better than gloves (keeps your warm fingers together while warming each other).

  • Wear 2 pairs of socks, with the inner layer made of synthetic fiber, such as polypropylene, to wick water away from the skin and the outer layer made of wool for increased insulation.

  • Shoes should be waterproof.

  • Cover your head, face, nose, and ears at all times.

  • Clothes should fit loosely to avoid a decrease in blood flow to the arms and legs.

  • Always travel with a friend in case help is needed.

  • Avoid smoking and alcohol.

People with diabetes and anyone with vessel disease should take extra precautions, as should the very young, very old, and unconditioned.

Be especially wary of wet and windy conditions. The "feels like" temperature (windchill) is actually much lower than the stated air temperature.

Outlook

A common saying among surgeons who have treated people with frostbite is "frostbite in January, amputate in July." It often takes months before the final separation between healthy and dead tissue may be determined. If surgery is performed too early, the risks of removing tissue that may eventually recover or leaving behind tissue that may eventually die are great. Some radiographic techniques currently are being investigated that may be able to make this division much sooner, thus permitting earlier definitive treatment. In some cases, bone scans are used to help predict the viability of tissue.

Beyond this waiting period, 65% of people will suffer long-term symptoms because of their frostbite. Common symptoms include pain or abnormal sensations in the extremity, heat or cold sensitivity, excessive sweating, and arthritis.

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Synonyms and Keywords

frostbite, frostnip (often used to refer to the precursor of frostbite), trench foot, chilblains, pernio, dead skin, dead tissue, cold weather, extremities

WebMD Medical Reference from eMedicineHealth Reviewed by Laura J. Martin, MD on May 01, 2016

Sources

SOURCE:

Frostbite from eMedicineHealth

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