Emergency War Surgery NATO Handbook: Part I: Types of Wounds
and Injuries: Chapter IV: Cold Injury
Host Factors
United States Department of Defense
Peer Review Status: Internally Peer
Reviewed
The following are host factors that may or may not influence the
development of cold injury:
- Age. There is no convincing evidence that age is a significant
epidemiologic factor in cold injury among combat troops.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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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