Emergency War Surgery NATO Handbook: Part I: Types of Wounds and Injuries: Chapter IV: Cold Injury

Classification

United States Department of Defense

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:

1. 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.

2. 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.

3. 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.

4. 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.

5. 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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Operational Medicine 2001

Health Care in Military Settings

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