Le coup de chaleur

Heatstroke is a potentially fatal disorder caused by an extreme increase in body temperature. It can result in widespread damage to the cardiovascular system, liver, kidney and blood clotting function. Classical heatstroke can occur during heat waves or as a result of intense environmental heat in persons in whom the thermoregulatory functions fail to adapt to a sudden increase in temperature, as during a heat wave, or to a high regional temperature. Exertional heatstroke can occur as a result of strenuous exercise, especially in hot, humid conditions, and may affect young, healthy individuals such as athletes during severe physical exertion and military recruits during training. A significant number of the histopathological and clinical characteristics described in persons with heatstroke indicate that these changes are a consequence of hyperthermia per se. A new hypothesis is that splanchnic vasoconstriction following heat stress leads to an increase in epithelial permeability and endotoxic translocation. The inflammatory factors involved could be similar to those observed in sepsis. Classical heatstroke is characterized by the following triad: rectal temperature 0≥40.6°C (> 105° F); neurological dysfunction with coma; and anhydrosis. Exertional heatstroke is characterized by a sudden collapse and loss of consciousness during exercise. The internal body temperature often exceeds 40.6 °C at the time of collapse, but hyperthermia is not indispensable to the diagnosis. Following heatstroke, rhabdomyolysis, renal damage, hepatic disorders and blood clotting dysfunction rapidly occur. An early diagnosis, the prompt institution of body cooling, and the rapid transportation of patients to an intensive care unit are essential for a favorable outcome. The mortality rate in these patients can be as low as 5% or less in centers where appropriate facilities for whole body cooling and emergency treatment are available.