hypertermia

Hypertermia, also called hyperthermia, is a medical condition in which the body's core temperature rises above normal due to excessive heat gain or impaired heat loss, not from a change in the hypothalamic set point as occurs with fever. It encompasses conditions such as heat stroke, heat exhaustion, and, in certain contexts, malignant hyperthermia.

Causes include environmental heat exposure (hot weather, high humidity, inadequate cooling), strenuous physical activity, dehydration, and medications or substances that impair sweating or vasoregulation (anticholinergics, sympathomimetics, recreational drugs). Genetic conditions like malignant hyperthermia trigger a rapid rise in temperature in response to certain anesthetics or muscle relaxants.

Pathophysiology involves excessive heat production or reduced dissipation, leading to rapid core temperature increase. Impaired sweating, skin vasoconstriction, and dehydration contribute to organ dysfunction, including the nervous system, kidneys, and coagulation system.

Clinical features vary by severity. Heat exhaustion presents with fatigue, dizziness, headache, nausea, pale skin, sweating, and elevated heart rate. Heat stroke is more severe and is characterized by core temperature typically above 40°C, altered mental status, confusion, seizures, and sometimes dry or minimally sweating skin.

Diagnosis relies on measuring core temperature and evaluating clinical context, with laboratory tests used to assess complications such as electrolyte disturbances, rhabdomyolysis, and organ injury.

Management is time-critical. Immediate cooling is essential—ice-water immersion or evaporative cooling with fans—along with removing clothing, providing freely available fluids, and correcting electrolyte disturbances. Treat complications and underlying causes; malignant hyperthermia requires dantrolene. Prevention focuses on hydration, acclimatization, avoiding excessive heat exposure, and recognizing early symptoms.