Central nervous system dysfunction defines heat stroke
Expansion
| Heat exhaustion | Heat stroke | |
|---|---|---|
| Temperature | Under 40 | Above 40 |
| Consciousness | Normal | Altered: confusion, seizures, coma |
| Sweating | Present | May be absent in classical form |
| Organ damage | None | Multi-organ: rhabdomyolysis, AKI, DIC, liver failure |
| Prognosis | Good | Life threatening |
“Confusion makes it heat stroke.” Central nervous system dysfunction with a temperature above 40 is the defining combination.
Two forms: classical, in the elderly and chronically unwell during a heatwave, often with dry skin; and exertional, in young athletes and soldiers, often still sweating.
Management is rapid active cooling, targeting a temperature below 39 within 30 minutes: remove clothing, cold water immersion (the most effective for exertional heat stroke), evaporative cooling with fans and tepid water, ice packs to the axillae and groins, and cold intravenous fluids.
Antipyretics are useless: paracetamol and NSAIDs lower a raised hypothalamic set point, and in heat stroke the set point is normal, so they do nothing and risk hepatic and renal harm.
Look for complications: rhabdomyolysis with a raised creatine kinase, acute kidney injury, DIC, and hepatic failure.
Consider the mimics: neuroleptic malignant syndrome, serotonin syndrome, malignant hyperthermia, thyroid storm and anticholinergic toxicity, each with a drug history and specific treatment.