COLD INJURIES - Medicine for Mountaineering and Other Wilderness Activities - page 390

supplied with warm blood so they can function after the rest of the body has become signi-
ficantly chilled.
PREVENTING HYPOTHERMIA
A human's greatest protection against the cold is the intellect. An ambient temperature of
about 82°F (28°C) is the thermoneutral temperature for an unclothed human body, which
means that a nude individual at rest at lower temperatures loses more heat to the envir-
onment than heat-generating processes are producing and heat-preserving mechanisms can
retain. Almost everywhere they live, humans are dependent upon intellectually devised
clothingandsheltertoprotectthemfromtheenvironmentandreduceheatlosstolevelsfor
which metabolism and physiology can compensate. Informed, intelligent behavior is more
necessary in the severe cold of high altitude and extreme latitude.
Threatening situations must be recognized in time for effective countermeasures. Pre-
paration is essential because clothing adequate for such climates can rarely be improvised.
Even when available, such clothing must be worn properly. Shelter often can be impro-
vised,butaskierwithasnowshovelisfarmorecapableofimprovisingasatisfactoryshel-
ter than a skier without one.
Water and Food
Avoidinghypothermiainacoldclimaterequireswater,food,andclothing.Failuretore-
placenormalwaterlossesthroughthekidneys,skin,andlungs,orabnormallossesbyother
routes, results in dehydration, which decreases the blood volume and, in a cold environ-
ment, impairs heat production by exercise. Dehydration can be accompanied by weakness,
fatigue,dizziness,andevenatendencytofaintwhenstanding,whichimpedeeffortstodeal
rationally with a threatening environment.
Dehydrationalsocontributestootherproblems.Constrictionofperipheralbloodvessels
so the smaller volume of blood goes to vital organs increases the risk of frostbite. Severe
shock may develop following minor injuries. Clots tend to form in the legs and can result
in pulmonary embolism ( Chapter 18: Respiratory Disorders ).
In a dehydrated state the sensation of thirst is diminished or absent, and a conscious ef-
fort to consume adequate fluids must be made. Water intake with mild exertion should be
at least two quarts per day. With heavier exertion or at high altitude, three to five quarts are
needed. In a world of snow and ice, fuel is required to melt snow for drinking water. Eat-
ing snow does not provide an adequate volume of water, and body heat is lost in warming
ingested snow to body temperature.
Anadequate fluidintakeisindicated byurinethathasalightyellowcolorandavolume
of at least one liter every twenty-four hours. Few outdoor recreationalists would measure
urinevolume,buttheyshouldbeabletoappreciateareducedfrequencyforvoiding,partic-