HEAT EXHAUSTION AND EXERTIONAL HEATSTROKE
Heat Exhaustion
Abstract
Introduction
Heat illness is a major cause of preventable morbidity worldwide, especially in regions characterized by high ambient temperatures. The major heat-related illnesses, heat exhaustion and heatstroke, involve varying degrees of thermoregulatory failure that occur when individuals are exposed to elevated temperatures. Heat exhaustion is characterized by moderately increased body temperature (101-102 degrees F), paleness, dizziness, nausea, vomiting, as result of excessive heat and dehydration. It may rapidly progress to heatstroke when the body's thermoregulatory mechanisms become overwhelmed. Heat stroke is defined as a core body temperature in excess of 40.5ºC (105ºF) with associated central nervous system dysfunction in the extreme environmental heat [1]. Exertional heat stroke generally occurs in healthy individuals who engage in heavy exercise during heat waves when air temperatures exceed 102.5°F (39.2°C) for 3 or more consecutive days. In classic exertional heat stroke, rate of heat production exceed to the capacity of the body to dissipate heat and the arterial carbon dioxide tension is often less than 20 mm Hg [2]. Patients with nonexertional heat stroke usually have respiratory alkalosis. In contrast, those with exertional heat stroke nearly always have both respiratory alkalosis and lactic acidosis [2]. It occurs in younger patients who are unable to avoid extreme environmental conditions. Typical patients are athletes, military cadets and soldiers during basic training [3]. In both cases, thermoregulatory mechanisms fail if the stress becomes too great, which results in accelerated hyperthermia. Heat stroke is associated with a systemic inflammatory response, which leads to end-organ damage with involvement of the CNS and end-organ dysfunction [4].
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