ABSTRACT
Despite various structural and functional adaptations for survival in warm environments, human beings have been plagued by heat-related illnesses throughout history. Heat stroke has claimed casualties since as early as King Edward's war against the Arabs for the Holy Land to the U.S. Army's loss of 125 soldiers during basic training for World War II.1-3 Heat stroke is the most serious manifestation of heatrelated illness, and is a true medical emergency that results from an overload or impairment of heat-dissipating mechanisms. Left untreated, this disorder is universally fatal if body temperature is not rapidly lowered.4 Older adults, obese patients, infants, patients with hyperthyroidism, and those taking certain medications are at the greatest risk, although the true risk for any patient is difficult to quantify since many patients with heat stroke are misidentified because of other disorders associated with an excessively high body temperature.4,5
HEAT PRODUCTION Metabolic processes throughout the body normally produce body heat; most body heat production is increased by the metabolic activity of skeletal muscle. In an average adult male, 1700 kilocalories (kcal) are produced each day, increasing to 2500 to 3000 kcal per day with moderate physical activity.1 Heat production can be increased by up to ten times above normal with excess shivering, tremor, or exertion.6 In addition to endogenous heat production, heat can be gained by radiation from the sun, ground, or reflected radiation from the sky.
