Emergency War Surgery NATO Handbook: Part I: Types of Wounds
and Injuries: Chapter IV: Cold Injury
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Cold is the primary etiologic agent in producing these injuries,
although wetness, duration of exposure, and other associated in
juries may add to the severity or eventual outcome of a particular
cold exposure. Long-term exposure in wetlands, even in tropical rice
paddies, swamps, and jungles, with its prolonged cooling of the feet
and constant wetness can produce an immersion-type injury. These
injuries represent a continuum of insult making the definition
between one type and another somewhat artificial. The spectrum of
cold injury in order of increasing seriousness includes chilblain,
trenchfoot, immersion foot, frostbite (including high-altitude
frostbite), and systemic hypothermia.
All of these conditions represent progressive degrees of a
fundamental pathologic process, which, irrespective of environmental
and other modifying factors, are all related to the common factor of
cold. Although the distinctions among the various types of cold
injury are often artificial, particularly the distinction between
trenchfoot and immersion foot, the following definitions are in
fairly general use:
- Chilblain, which frequently affects the hands as well as the
feet, may result from exposure to air temperatures from just above
freezing to as high as 60°F (16°C); is more likely to
occur in dry, cold, windy air; but can also be associated with
high humidity. It is not of major clinical significance in
military operations.
- Immersion foot implies an injury caused by exposure, usually
in excess of 12 hours, to water at a temperature of about
50°F (10°C). This injury is common in wet jungles and in
exposed life rafts.
- Trenchfoot, which may also occur in the hands, results from
prolonged exposure to cold at temperatures ranging from just above
freezing to 50°F (10°C), often in a damp environment,
and usually in connection with immobilization and dependency of
the extremities. The blunt trauma of walking on wet feet hastens
this injury.
- Frostbite implies the crystallization of tissue fluids in the
skin or subcutaneous tissues after exposure to temperatures of
32°F (0°C) or lower. Depending upon the ambient
temperature and wind velocity, the exposure necessary to produce
frostbite varies from a few minutes to several hours. Frostbite
may occur at various altitudes. Special attention has been given
to high altitude frostbite. The ambient temperature decreases
approximately 35°F (2°C) for every 1,000 feet of
increase in altitude. The temperature becomes stable at about
-67°F (-55°C) at an altitude of 35,000 feet or higher,
and exposure to these very low temperatures may instantaneously
result in severe injuries to exposed parts of the body.
- Systemic Hypothermia is a condition associated with a drop of
the core temperature below 94°F (34.4°C). This
life-threatening, non-freezing cold injury is usually the result
of either long-term exposure to cold air or immersion in cold
water. It should be noted that freezing temperatures are not
necessary to produce hypothermia, because wind, rain, and cool
temperatures increase body heat loss significantly.
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