This phase can last several days. If the cold exposure was long enough, the tissue doesn’t revive and ulcers and gangrene can set in leading to permanent disability and even amputation. Recovery (the last phase) is characterized by a normalization of vascular responses in the foot though there may be permanent skin changes. Excessive sensitivity to the cold may persist for years and tissue damage from more severe cases can result in debilitating nerve damage and resultant pain.
True frostbite results from the actual freezing of the tissues of the body. Feet, hands, ears and nose are the most commonly affected areas of the body. Historically frostbite has gone through several classifications to enhance specific treatment approaches. One such approach is to parallel burn injury with first degree, second degree etc. We feel it is more useful to talk about this serious condition in terms of frostnip, superficial and deep frostbite as the outcomes are very different. The colder the temperature the quicker these conditions can develop. In the Artic, even very brief unprotected exposure to the environment can result in a frostbite injury.
Frostnip is the mildest form of this class of cold injury and does not involve actual tissue freezing. Almost frozen is the best way to think about this complication and therefore the outcomes of treatment are always good. Affected tissues blanch white with a lack of blood flow and sensation is lost. Treatment is common sense: get out of the cold. Tissues quickly re-establish normal blood flow, tingling occurs as nerves “wake up” and resolution is quick and complete.
Superficial frostbite is much more serious and is the result of actually freezing your living flesh. By definition it involves the skin and subcutaneous tissues. There are several technical theories as to the exact cellular injury mechanism, suffice to say having a frozen body part is a bad thing. The frozen tissue is hard and has a waxy white coloration. There is a residual softness to the underlying (non-frozen) tissues, but no sensation or blood flow to the frozen part. Think a pack of burgers in the freezer for an hour or so. The outside is crusted hard frozen, but underneath is still pliable.
The frozen body part is totally without sensation. How much tissue “revives” depends on duration and extent of the injury. It is essential that once you begin to thaw your frostbitten part, you do not allow for re-freezing. For example it's better to walk on a frozen foot for two days than to thaw at night only to have it re-freeze the next day as you are seeking help. This may sound counter intuitive, but is based on extensive observation.
Treatment is literally defrosting your body part. Over zealous exposure to campfire warmth is absolutely not the way to do this. Remember, the affected part won’t feel anything and you are most likely to add burn injury to your cold injury! Rubbing snow on the area is a hold over from Napoleon’s army and is as useful as most medical approaches from the early 1800’s.
