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

Host Factors

United States Department of Defense

The following are host factors that may or may not influence the development of cold injury:

1. Age. There is no convincing evidence that age is a significant epidemiologic factor in cold injury among combat troops.

2. Smoking. There is very clear evidence that the vasoconstrictor action of nicotine causes increased cooling of the extremities and an increased likelihood of frostbite. A significant number of severe injuries in military populations occur in heavy tobacco users.

3. Previous Cold Injury. Individuals with previous cold injuries are at a higher-than-normal risk of subsequent cold injury. The fact that such repetitive injury does not usually occur at the same site suggests that this relates to the individual's lower resistance to cold rather than as a result of the previous injury.

4. Branch of Service. Trenchfoot, immersion foot, and frostbite have a high selectivity for frontline riflemen, especially for riflemen of lower ranks. In World War II, approximately 90% of all casualties from cold occurred in riflemen.

5. Fatigue. Both physical and mental weariness contribute to apathy which leads to neglect of all acts except those vital to survival. Fatigue is most evident in troops who are not rotated and must remain exposed and in combat for prolonged periods of time. Three days of being cold and wet appears to be a prudent timeframe within which to consider rotation of troops.

6. Racial Susceptibility. In all studies from World War II, Korea, and recent experiences in Alaska, blacks had four to six times the incidence of cold injury of their white counterparts, matched for geographic origin, training, and education. This increased susceptibility is related to two factors: (a) differences in anatomic configuration, and (b) differences in physiologic response to cold. Because long, thin fingers and toes cool more rapidly than short, fat ones, blacks' hands tend to cool faster than those of whites. However, more importantly, once cold, blacks stay cold longer because of a less potent CIVD response to their extremities. This does not say, however, that blacks themselves must be more vigilant in cold exposure and must take measures sooner to protect themselves from cold injury. Place of origin has a significant role in cold injury susceptibility. Individuals raised in northern-tier states (i.e., cold climates) have a more protective CIVD response. This response also improves in blacks from northern climates. This is not only a physiologic improvement in response to cold but a behavioral response as well. Knowing what clothes to wear, knowing when one's extremities are too cold, not being frightened of the cold, and knowing how to deal with cold extremities all add up to make cold-experienced individuals less likely to have cold injuries. Individuals with labile vasomotor conditions, such as Raynaud's, are also susceptible to cold injury.

7. Psychological Factors. Cold injury tends to occur in passive, negative individuals. Such persons show less muscular activity in situations in which activity is unrestricted and are careless about precautionary measures when cold injury is a threat. Fear also may increase the incidence of cold injury by reducing the spontaneous rewarming known as CIVD.

8. Other Injuries. Concomitant injuries that result in a reduction of circulating volume or a localized reduction in blood flow predispose the individual to cold injury. In addition, immobilization associated with a concurrent injury increases the risk of frostbite in cold environments if adequate additional insulating protection is not provided. Poor hydration and hypovolemia decrease perfusion of the extremities.

9. Drugs and Medication. Any drug modifying autonomic nervous system responses, altering sensation, or modifying judgment can have disastrous effects on an individual's performance and survival in the cold. These factors must be impressed upon medical officers involved in the care of troops in cold environments and must be impressed upon individual unit commanders and their men. In the civilian community, alcohol use is the single most common factor associated with hypothermia.

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Operational Medicine 2001

Health Care in Military Settings

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