Fever and Hyperthermia (revised)
• The maximum normal temperature in adults is 37.7oC (should be late afternoon)
• For temperatures > 104oC (40oC), think about heat stroke, malignant hyperthermia, and
neuroleptic malignant syndrome.
In emergency settings, begin external cooling measures for temperatures > 105oF (40.5oC).
• In normal individuals, body temperature is lowest at 6am, highest between 4 and 6pm
• The maximum normal temperature (99th percentile) is 37.2oC in the am and 37.7oC in the pm
• During a fever, pyrogens act at the hypothalamus to shift the “set-point” upward
♦ The body responds with vasoconstriction and shivering to raise the core body temp.
♦ With treatment, the set-point goes down with resulting sweating and vasodilation
• Elevation of core body temperature from a failure of thermoregulation (not pyrogens)
• Often with temperatures > 104oF (40oC)
• The 3 most important causes are:
♦ Heat Stroke
♦ Neuroleptic malignant syndrome
♦ Malignant hyperthermia
• Other causes are infectious, endocrine, CNS, toxic . . . .
• It is temps > 40.5oC with CNS dysfunction from inability to dissapate environmental heat
• Can be exertional in young individuals during heavy exercise in high heat and humidity
• Non-exertional heat stroke is from impaired thermoregulation (drugs) or prolonged exposure
• Clinical presentation
♦ Cutaneous vasodilatation, tachypnea, noncardiogenic pulmonary edema, DIC, altered
mental status, seizures, acute renal failure, leukocytosis, etc.
♦ Skin my be moist OR dry depending on cause
Neuroleptic malignant syndrome
• Idiosyncratic reaction to antipsychotic agents
♦ Most common: haldol, stelazine, thorazine, navane, etc.
• Hyperthermia, “lead pipe” rigidity, altered mental status, tremors
• Also see autonomic dysfunction: diaphoresis, labile blood pressure, etc.