Emergency War Surgery NATO Handbook: Part I: Types of Wounds and Injuries: Chapter IV: Cold Injury
United States Department of Defense
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Trenchfoot, frostbite, immersion foot, and hypothermia are the cold injuries of greatest military significance. It is believed that frostbite will continue to be the cold injury of major importance, but the use of rubberized, insulated footwear and specific training techniques and procedures will limit the trenchfoot injuries in future combat settings. It is noted that the introduction of the insulated vapor-barrier boot to U.S. forces in Korea almost eliminated cold injury as a reason for hospital admission. This insulated vapor-barrier boot revolutionized footwear for combat soldiers and played the key role in preventing of cold injury of the feet. The type of cold injury incurred is dependent upon the exposure temperature, the duration of exposure, and other environmental factors, such as wind and water, which intensify the effect of the temperature. On exposure to cold, there is an initial peripheral vasoconstriction in an attempt to conserve core heat. This vasoconstrictive episode, which is of short duration, is overcome by a physiologic protective mechanism termed cold induced vasodilation (CIVD). CIVD intervenes to cause arteriovenous shunting to the skin. This allows relatively large volumes of blood to flow through cold extremities. Repeated cold exposures are said to improve this CIVD response, but it may be suppressed or absent when the individual is chilled, frightened, exhausted, or malnourished. This mechanism appears to be blunted in blacks and perhaps in other races.
Trenchfoot and immersion foot are essentially the same injury, the major differences being the temperatures involved and the duration of exposure. The colder it is, the shorter the duration necessary to produce trenchfoot, whereas the longer the duration and the warmer the temperature, the more likely one is to develop an immersion foot injury. The average duration of exposure in trenchfoot is three days, but the exposure may range from a few hours to many days, with individual susceptibility apparently playing a considerable role. The average duration of exposure in frostbite is ten hours, but this varies with ambient temperature, moisture, clothing, activity, and other factors which will be discussed below (in this chapter).
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