HEAT AND SOLAR INJURIES - Medicine for Mountaineering and Other Wilderness Activities - page 418

During cooling, the extremities should be massaged to help propel cooled blood back
into the organs of the body and head. Oxygen should be administered if available.
After the temperature has been reduced to 102°F (39°C), active cooling should be
slowed to avoid hypothermia, but the individual must be closely monitored to ensure that
the temperature does not climb back to higher levels. Rebound is particularly common
three to four hours after cooling. Drugs do not effectively reduce body temperature, may
aggravate complications, and should not be administered.
As soon as possible the person should be evacuated to a hospital, particularly if uncon-
scious for more than a few minutes. The complications of heat stroke include failure of
essentially every organ system—particularly the heart, liver, and kidneys. Blood clotting
abnormalities, gastrointestinal ulceration with bleeding, biochemical alterations, and ex-
tensive brain damage also occur. Unconsciousness lasting more than two hours is a poor
prognostic sign that is usually followed by permanent disability or death.
Heat Cramps
Heat cramps are severe, spasmodic contractions of one or more muscles, most com-
monly the leg muscles. Cramps may last up to fifteen minutes or even longer, and the
muscles are usually painful for several days afterward.
Stretching the muscle usually can stop cramps almost immediately. For example, ex-
tendingthelegandpullingthefootupwardcanstretchthecalfmuscle.Kneadingorpound-
ing the muscle is less effective and probably contributes to residual soreness.
Cramps usually appear in the most heavily worked muscles and may be produced, in
part, by an excessive water intake without accompanying salt, resulting in dilution of the
saltintheextracellularfluid.Crampsaremorecommonincircumstancesthattendtocause
salt depletion; they can be prevented to a large extent by consuming large quantities of salt
and water.
INJURY BY SOLAR RADIATION
Sunlight has been considered beneficial because it plays a significant role in Vitamin D
synthesis. However, questions about that assumption are being raised. Some investigators
argue that all sun exposure is harmful, not just excessive exposure, because DNA can be
damaged by any amount of ultraviolet radiation. Everyone is familiar with sunburn, but
manyindividualsarenotaswellawareof—orchoosetoignore—thedegenerative changes
associated with repeated exposure that eventually lead to skin cancer. Three hundred thou-
sand new skin cancers are diagnosed every year in the United States, and the incidence is
increasing.
Much of the energy in solar radiation has shorter (ultraviolet) or longer wavelengths
(infrared) than visible light ( Fig. 27-1 ) . Most biologic damage is caused by ultraviolet ra-