Overview

Hyperthermia: an elevation of normal body temperature due to failed thermoregulation.

Heatstroke: a life-threatening condition that presents with hyperthermia > 40°C (104°F) and central nervous system dysfunction (e.g., altered mental status).

The normal physiologic response to increased body temperature is hypothalamus-mediated peripheral vasodilation (to expose blood to the cooler air) and sweating (to dissipate heat into the environment).

In heatstroke, the hypothalamic thermoregulatory response is inadequate to maintain a normal temperature.

Causes include:

• Increased heat production (e.g., strenuous exercise, sepsis, status epilepticus, cocaine and amphetamines, thyroid storm)

• Decreased heat dissipation (e.g., high ambient temperature or humidity, vasoconstrictor drugs, skin diseases, burns, reduced CNS response due to alcohol and sedatives)

• Reduced behavioral responsiveness (e.g., infants, the elderly, and chronically ill individuals who are unable to control their environment and water intake)

High body temperature → protein denaturation, phospholipid and lipoprotein damage, and membrane lipid liquefaction → cell damage and loss of function (including myocardiocytes and neurons) → cardiovascular collapse → multiorgan failure and possibly death