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Frostbite (congelatio in medical terminology) is the medical condition whereby damage is caused to skin and other tissues due to extreme cold. At or below 0° C (32° F), blood vessels close to the skin start to narrow (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. 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".
Additional recommended knowledge
Risk factors for frostbite include using beta-blockers and having conditions such as diabetes and peripheral neuropathy.
Generally, frostbite is accompanied by discoloration of the skin, along with burning and/or tingling sensations, partial or complete numbness, and possibly intense pain. If the nerves and blood vessels have been severely damaged, gangrene may follow, and amputation may eventually be required. If left untreated, frostbitten skin gradually darkens after a few hours. Skin destroyed by frostbite is completely black, and looks loose and flayed, as if burnt.
Treatment of frostbite is not initiated until it is likely that the affected areas can remain thawed, as thawing followed by re-freezing can lead to more extensive and severe damage to the frostbitten tissue. In severe cases a body part that has frozen can cause the heart to stop when it thaws as the cold blood starts to circulate and shocks the heart as it flows through it, therefore it's important to warm someone who has had severe frostbite very carefully (see below for temperatures).
If medical attention is available, the victim is moved to a warm but never hot, safe area. The frostbitten areas are dressed, but not rubbed or massaged as ice crystals that have formed in the body act as tiny knives and ruin body tissue when rubbed. Also, beating or slapping the affected area is also very harmful, although it was once done to increase blood flow to the area.
If medical attention is not immediately available, the affected areas are placed in warm, but not hot, water, until tissues are soft and sensation has returned. The water temperature must be 107.6 degrees F (42 degrees C), and any major fluctuation from this can cause serious harm. At 113 degrees F (45 degrees C) the water will scald the frostbitten tissue, and below 107.6 has also proven to cause harm. Afterward, when the tissues have reached 98.6 degrees F (37 degrees C), the tissues are wrapped in clean, sterile dressings, and moved normally. It is crucial to keep the frostbitten skin from refreezing, as this is very harmful.
Factors that contribute to frostbite include extreme cold, wet clothes, wind chill and poor circulation. This 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.
Before anticipated prolonged exposure to cold, one should not drink alcohol or smoke, and get adequate food and rest. Multiple layers of clothing, especially wind and water-proof synthetic fabrics, are the best protection against frostbite. Gloves and a hat that covers the ears are especially important. One should not wear fabrics like cotton, which retain moisture.
If caught in a severe snowstorm, one should find shelter early or increase physical activity to maintain body warmth.
"Prevention is better than cure"...people susceptible to frost bites should wear woollen socks/gloves/caps in extreme cold. For frostbites in the feet, keeping feet in warm saline water will provide relief.
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