Amy J. Movius, MD
January 20, 2009
Frostbite is something everyone is Maine should know a thing or two about. Frostbite is when body tissues literally freeze, and ice crystals form inside cells. If the skin is the only tissue frozen it is “superficial” frostbite. Deep frostbite occurs when all tissue layers are involved. Ironically, frostbite is classified by degrees, similar to burns.
Certain areas of the body are more susceptible to frostbite. This is because, in very cold conditions, the body’s first priority is to keep the core organs and tissues warm. To do this, blood will be shifted away from the extremities/outermost parts of the body and towards the more essential central organs such as the heart and the lungs. (While you may think your fingers and toes are essential, your physiology does not!). Anywhere that skin is exposed, such as the face, is also at risk.
The first symptom of frostbite is usually numbness or loss of feeling. Affected areas may even feel frozen and hard. Also, skin can turn white, waxy or grey in appearance.
Everyone is at risk for frostbite in freezing weather if not dressed properly, if they are in the cold for too long, or if they become wet. The old and young tend to be especially vulnerable as are those with circulation problems (ex = diabetes), those who have had a previous injury from the cold, and persons using drugs such as beta – blockers or those using alcohol, caffeine, or nicotine as all these substances can decrease circulation.
So, when does frostbite occur? First, the temperatures must be at or below freezing. This is not as simple as it sounds, however, as the effective temperature is affected by wind, which cools the body at a faster rate. The colder the effective temperature (including wind chill), the faster frostbite can develop. For example, at a temperature of 0◦ with no wind, frostbite should not occur. With a wind of 15mph the wind chill factor is -19◦ and exposed skin will freeze in an average of 30 minutes. If the ambient temperature is -15◦ with the same wind of 15mph, skin will freeze in about 10 minutes. This is because the effective temperature will now be -40◦.
The best treatment for frostbite is prevention. Dress in light, loose layers that provide ventilation and insulation. Head protection is very important as 40% of body heat can be lost from the head. Protect the hands and feet also; for this purpose, mittens are superior to gloves. Don’t drink or smoke before going out in cold conditions, and if you get wet, get inside ASAP. The same goes for if any numbness develops.
If evidence of frostbite occurs, move to a warm room ASAP. Call for help. Giving/consuming warm drinks such as broth and tea may be useful. Rest and elevate the frostbitten area, and if the feet are involved, avoid walking. The area of frostbite should be immersed in warm (not hot) water until sensation/warmth returns, which may take 30-45 minutes. If there is a chance re-exposure will occur shortly after warming, do not rewarm as refreezing will cause even more damage. With return of sensation, significant pain may develop.
Frostbitten areas should never be rubbed, as this can cause further injury. Likewise, never use dry heat (heating pads, sunlamps, fireplaces etc.) when treating frostbite. Since the frostbitten areas are numb, it is easy to burn the skin of these areas with dry heat and not know it.
For more on this topic, please see the resources below:
1. Centers for Disease Control and Prevention: www.cdc.gove/nceh/hsb/extremecold
2. National Weather Service Wind Chill web page: www.nws.noaa.gov/om/windchill
3. Frostbite, C Crawford Mechem MD, MS FACEP www.emedicine.com
4. Guidelines on the Risk and Time to Frostbite during Exposure to Cold Winds, Ducharme and Brajkovic www.rto.nato.int/abstracts.asp
5. Frostbite, American Academy of Orthopaedic Surgeons, www.orthoinfo.org