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August 15, 2019

Written by Vivian Lei

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Heatstroke is a deadly triad of hyperthermia, CNS dysfunction, and multiorgan failure. Classic (or passive) heatstroke is due to environmental exposure and poor heat dissipation, whereas exertional heatstroke is related to strenuous physical activity. Prompt recognition and treatment can be life-saving and is focused on rapid cooling.

Why does this matter?
With record-breaking temperatures around the globe, we could all use a refresher on the recognition and treatment of heatstroke.

Who gets heatstroke?

  • Heatstroke is commonly classified as classic (passive) or exertional.

    • Classic heatstroke occurs frequently among the elderly and prepubertal children as a result of environmental heat stress and impaired heat dissipation mechanisms.

      • Risk factors include exposure to heat waves, decreased physiologic compensatory mechanisms, social isolation or dependence, poor living conditions, chronic illness, and medications impairing thermoregulation.

    • Exertional heatstroke occurs due to strenuous physical activity and excessive heat production.

      • Risk factors include heavy exercise under peer or coach pressure, lack of acclimatization to heat, low level of physical fitness, protective clothing, obesity, sweat gland dysfunction, and drug abuse.

What is heatstroke?

  • Thermoregulatory needs are exceeded leading to a rise in core body temperature.

  • Increased heat stress triggers an inflammatory cascade which leads to cell anoxia, increased gastrointestinal permeability, and cardiovascular collapse.

  • Multiorgan failure results consisting of CNS dysfunction, liver dysfunction, renal failure, DIC, muscle breakdown, and cardiac dysfunction.

How is heatstroke diagnosed?

  • Prompt recognition is critical and includes an accurate measure of core (rectal) body temperature.

  • It consists of a clinical triad of hyperthermia (>40°C), neurologic abnormalities, and exposure to heat stress (either environmental or through physical exertion).

  • Tachycardia, tachypnea, and hypotension are common.

  • Sweating is typical of exertional heatstroke, whereas dry skin may be present in classic heatstroke.

  • CNS disturbances include behavioral changes, confusion, delirium, dizziness, weakness, agitation, combativeness, slurred speech, nausea, seizures, coma.

What other diseases should be considered?

  • Meningitis, encephalitis, epilepsy, drug intoxication, severe dehydration, metabolic syndromes (neuroleptic malignant syndrome, serotonin syndrome, thyroid storm, pheochromocytoma crisis)

How is heatstroke treated?

  • Rapid cooling is vital with a target temperature below 39°C.

  • In exertional heatstroke, immersion in cold water is preferred. When possible, prehospital cooling measures should be initiated prior to transport.

  • In classic heatstroke, use of conductive or evaporative cooling is recommended. This can include a combination of infusion of cold IV fluids, application of ice packs, and/or wetting the skin and fanning.

  • Antipyretics such as aspirin or acetaminophen are not effective and should not be used due to toxicity potential.

  • Perform lab studies to evaluate for organ dysfunction: CBC, glucose, urinalysis, blood cultures, electrolytes, kidney function tests, liver function tests, ABG, coagulation panel, CK, LDH, myoglobin.

  • Patients will require admission to an intensive care unit for supportive care and management of multiorgan failure, which peaks within 24 to 48 hours.

Heatstroke. N Engl J Med. 2019 Jun 20;380(25):2449-2459. doi: 10.1056/NEJMra1810762.

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