Emergency Medicine · Environmental Emergencies
The facts most likely to be tested
Heat stroke is defined by a core body temperature >40°C (104°F) accompanied by central nervous system dysfunction.
The primary clinical distinction between heat exhaustion and heat stroke is the presence of altered mental status, such as confusion, seizures, or coma.
Rapid evaporative cooling via misting and high-flow fans is the first-line treatment for exertional heat stroke.
Cold water immersion is the gold standard and most effective method for rapid cooling in exertional heat stroke.
Antipyretics like aspirin or acetaminophen are contraindicated because they are ineffective for heat-related illness and may exacerbate coagulopathy or liver injury.
Complications of heat stroke include rhabdomyolysis, disseminated intravascular coagulation (DIC), and multi-organ failure.
Non-exertional (classic) heat stroke typically affects the elderly or chronically ill during heat waves, whereas exertional heat stroke typically affects young, healthy individuals during intense physical activity.
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A 22-year-old male marathon runner collapses near the finish line on a humid 95°F day. On arrival, he is agitated and combative, with a core rectal temperature of 105.2°F (40.7°C). His skin is hot and dry, and he is noted to have tachycardia and tachypnea. He is unable to follow commands and has slurred speech.
What is the most appropriate initial management for this patient?
Rapid cold water immersion
The patient presents with classic signs of exertional heat stroke (hyperthermia >40°C and altered mental status), for which rapid cold water immersion is the most effective cooling modality to prevent end-organ damage.
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Etiology / Epidemiology
Occurs when thermoregulation fails; exertional (athletes/laborers) vs non-exertional (elderly/infants).
Clinical Manifestations
Core temperature >40.5°C (105°F) with altered mental status. Skin may be dry or diaphoretic.
Diagnosis
Clinical diagnosis based on core temperature >40.5°C and CNS dysfunction.
Treatment
Rapid evaporative cooling is first-line. Avoid antipyretics.
Prognosis
High mortality if untreated; multi-organ failure and rhabdomyolysis are primary drivers.
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Epidemiology & Etiology
Non-exertional (classic) heat stroke typically affects the elderly or those with limited access to cooling. Exertional heat stroke occurs in young, healthy individuals performing intense physical activity in hot, humid environments. Anticholinergics and diuretics significantly increase risk by impairing sweating and volume status.
Pertinent Anatomy
The hypothalamus serves as the body's thermostat, integrating peripheral thermal input. Failure of this central control leads to systemic hyperthermia and subsequent end-organ damage.
Pathophysiology
Hyperthermia triggers a systemic inflammatory response syndrome (SIRS) leading to endothelial injury and coagulopathy. Direct thermal damage causes cellular necrosis and protein denaturation. This cascade often progresses to disseminated intravascular coagulation and multi-organ dysfunction syndrome.
Clinical Manifestations
The hallmark is core temperature >40.5°C accompanied by altered mental status (seizures, delirium, or coma). Patients may present with hypotension, tachycardia, and tachypnea. Red flags include rhabdomyolysis, acute kidney injury, and hepatic failure.
Diagnosis
Diagnosis is clinical, requiring core temperature >40.5°C and CNS dysfunction. Rectal thermometry is the gold standard for accurate core temperature measurement. Labs should include CK, LFTs, and coagulation studies to assess for systemic damage.
Treatment
Initiate rapid evaporative cooling (misting with water and fans) immediately. Do not use antipyretics (e.g., aspirin/acetaminophen) as they are ineffective and may worsen coagulopathy or liver injury. If cooling fails, consider cold water immersion. Manage hypotension with isotonic fluids, but avoid over-resuscitation.
Prognosis
Prognosis depends on the duration of hyperthermia. Monitor for rhabdomyolysis and acute renal failure as primary complications. Patients require admission to an ICU for continuous monitoring of core temperature and organ function.
Differential Diagnosis
Neuroleptic Malignant Syndrome: associated with dopamine antagonists and muscle rigidity
Serotonin Syndrome: associated with serotonergic agents and hyperreflexia
Malignant Hyperthermia: associated with volatile anesthetics and succinylcholine
Thyroid Storm: associated with tachycardia, goiter, and history of hyperthyroidism
Sepsis: associated with infectious source and typically lower core temperatures