Frostbite

Frostbite (congelatio in medical terminology) is the medical condition wherein localized damage is caused to skin and other tissues due to extreme cold.

Frostbite is most likely to happen in body parts farthest from the heart and those with a lot of surface area exposed to cold. The initial stages of frostbite are sometimes called "frostnip". Mountains or high altitudes with snow are often where the most serious cases of frostbite occur.

Mechanism
At or below 0º C (32°F), blood vessels close to the skin start to constrict. This helps to preserve core body temperature. In extreme cold, or when the body is exposed to cold for long periods, this protective strategy can reduce blood flow in some areas of the body to dangerously low levels. The combination of cold temperature and poor blood flow can cause severe tissue injury by freezing the tissue.

If frostbite is not treated immediately then the damage and the frostbite becomes permanent. Nerve damage will occur due to oxygen deprivation. Frostbitten areas will turn discolored, purplish at first, and soon turn black. After a while nerve damage becomes so great that feeling is lost in the frostbitten areas. Blisters will also occur. If feeling is lost in the damaged area, checking it for cuts and breaks in the skin is vital. Infected open skin can lead to gangrene and amputation may be needed.

Risk factors
Risk factors for frostbite include using beta-blockers and having conditions such as diabetes and peripheral neuropathy.



Treatment
Treatment of frostbite centers, on rewarming (and possibly thawing) of the affected tissue. This can be achieved in one of two ways:

Passive rewarming involves using body heat or ambient room temperature to aid the patient's body in rewarming itself. This includes wrapping the patient in blankets, moving him/her into a warmed enclosure, or applying body heat via skin contact with another person.

Active rewarming is the direct addition of heat to the patient or tissue, usually in addition to the treatments included in passive rewarming. Active rewarming is more difficult to perform properly and has some added risks, so it is not considered appropriate for treating more serious cases of frostbite outside of a hospital. When performed, active rewarming seeks to thaw the injured tissue as quickly as possible without burning the patient. This is desirable because thawing frostbitten tissue is extremely painful and because the faster tissue is thawed, the less tissue damage occurs. This is achieved by immersing the injured tissue in a water-bath that is held just above body temperature.

Excessive movement of frostbitten tissue can cause ice crystals that have formed in the tissue to do further damage. Splinting and/or wrapping frostbitten extremities is therefore recommended to prevent such movement. For this reason, rubbing, massaging, shaking, or otherwise applying physical force to frostbitten tissues in an attempt to rewarm them can be very harmful and is not recommended.

The use of hyperbaric oxygen therapy as an adjunctive therapy can assist in the salvaging of a greater amount of tissue by increasing the viability of cells bordering necrotic tissue by preventing hypoxia and reducing edema. There have been case reports but few actual research studies to show the effectiveness.

Prevention
Factors that contribute to frostbite include extreme cold, inadequate clothing, wet clothes, wind chill, and poor circulation. Poor circulation can be caused by tight clothing or boots, cramped positions, fatigue, certain medications, smoking, alcohol use, or diseases that affect the blood vessels, such as diabetes.

People working in chemical laboratories should take precautions to wear gloves and other safety equipment as liquid nitrogen and other cryogenic liquids can cause frostbite even with brief exposure.

It is important to find shelter early if caught in a severe snowstorm or other outdoor situation in very cold weather. This is especially important if the weather is windy, as wind chill can greatly reduce the time it takes for frostbite to set in. Even a small cave, ditch, hollow tree, or vehicle can help reduce the chances of frostbite. It is also important to increase physical activity to maintain body warmth, especially in the hands and feet. If without gloves or with inadequate gloves, hands should be kept inside clothing next to the body to stay warm. Extra clothing such as scarves or underwear can be placed around the toes. The face, especially the nose, should be covered with a scarf or other garment. Contrary to popular belief sharing a sleeping bag or blanket with one or more other people, or even dogs, doesn't help to keep warm. If one person has hypothermia or frostbite, it is recommended that person has a sleeping bag or blanket in close proximity to victim.(after removing boots, outer clothing, wet clothing, etc.) to gradually warm the victim. This is because the victim will absorb the heat from the warm person, therefore possibly causing 2 cold injury casualties.

People susceptible to frostbite should wear woolen socks, gloves, and caps in extreme cold. For frostbite in the feet, keeping feet in warm saline water will provide relief. Diabetes can also sometimes lead to frostbite, so diabetics should take precautions as to avoid trips to ice-cold places.