Hyperthermia
Basics
Description
Description
- Range of progressively more severe illnesses due to increasingly overwhelming heat stress
- Begins with dehydration and electrolyte abnormalities and progresses to thermoregulatory dysfunction and multisystem organ failure
- Body temperature is maintained within a narrow range by balancing heat production with heat dissipation
- Oxidative phosphorylation becomes uncoupled and essential enzymes cease to function above 108°F (42°C)
Heat Stroke
- Core body temp >105°F (40.5°C)
- Failure of thermoregulatory function leads to severe central nervous system (CNS) dysfunction and multisystem organ failure
- Classic heat stroke (nonexertional):
- Occurs in patients with compromised thermoregulation or an inability to remove themselves from a hot environment (e.g., extremes of age, debilitated)
- Develops over days to weeks, usually during heat waves
- Severe dehydration, skin warm and dry
- Exertional heat stroke:
- Younger, athletic patients with combined environmental and exertional heat stress (e.g., military recruits)
- Develops over hours
- Internal heat production overwhelms dissipating mechanisms, often despite persistent sweating
Heat Exhaustion
- Core temp moderately elevated but usually <104°F (40°C)
- Fluid and/or salt depletion occurs secondary to heat stress
- Thermoregulatory function is maintained and CNS function is preserved
- Variable nonspecific symptoms including malaise, headache, fatigue, and nausea
- If left untreated, progresses to heat stroke
Etiology
Etiology
- Pre-existing conditions that hinder the body's ability to dissipate heat predispose for heat-related illness:
- Age extremes
- Dehydration (incl. gastroenteritis, inadequate fluid intake)
- Cardiovascular disease (incl. CHF, CAD)
- Obesity
- Diabetes mellitus, hyperthyroidism, pheochromocytoma
- Febrile illness
- Skin diseases that hinder sweating (incl. psoriasis, eczema, cystic fibrosis, scleroderma)
- Pharmacologic contributors:
- Sympathomimetics
- LSD, PCP, cocaine
- MAO inhibitors, antipsychotics, anxiolytics
- Anticholinergics
- Antihistamines
- β-blockers
- Diuretics
- Laxatives
- Drug or alcohol withdrawal
- Environmental factors:
- Excessive heat/humidity
- Prolonged exertion
- Lack of mobility
- Lack of air conditioning
- Lack of acclimatization
- Occlusive, nonporous clothing
Pediatric Considerations
Children are at increased risk of heat illness due to increased body surface area to mass ratio and lower sweat production
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Citation
Schaider, Jeffrey J., et al., editors. "Hyperthermia." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307363/all/Hyperthermia.
Hyperthermia. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307363/all/Hyperthermia. Accessed November 3, 2024.
Hyperthermia. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307363/all/Hyperthermia
Hyperthermia [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2024 November 03]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307363/all/Hyperthermia.
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