Hyperthermia

A pathological elevation of core body temperature above the normal set point (>37.5–38.3°C or >99.5–100.9°F) due to failure of thermoregulatory mechanisms, where the body absorbs or produces more heat than it can dissipate. Unlike fever, it is not caused by a hypothalamic reset of the temperature set point.

• Heat stroke: A life-threatening medical emergency defined by a core body temperature >40°C (>104°F) and confusion due to thermoregulatory failure.

Causes

• Environmental heat exposure

• Excessive heat production: Intense exercise

• Impaired heat loss

  • Dehydration

  • Reduced sweating (hypohidrosis or anhidrosis)

  • Autonomic dysfunction affecting thermoregulation

  • Heavy or tight clothing preventing evaporation

• Medication and substance-related causes

  • Drug reactions

  • Anesthetic reactions --> malignant hyperthermia

  • Stimulants

  • Anticholinergic medications impairing sweating