Heat Stroke
🌡️ Heat stroke = life-threatening emergency defined by core temperature >40°C with cerebral dysfunction (delirium, seizures, coma). ⚡ Mortality is high if not rapidly recognised and cooled.
🔥 Types of Heat Stroke
- 🌞 Non-exertional (classic):
– Highest risk in elderly, very young, chronically unwell, or socially vulnerable (e.g. no access to air conditioning).
– Triggered by prolonged exposure to hot, humid conditions.
– Risk factors: obesity, immobility, Parkinson’s drugs, diuretics, anticholinergics.
- 🏃 Exertional heat stroke:
– Affects young, fit people in hot, humid environments (athletes, military, outdoor labourers).
– Exacerbated by clothing/equipment limiting cooling.
– Symptoms: altered mental status, ataxia, coma, nuchal rigidity, posturing.
– Profuse sweating is typical, though sweating may cease in later stages.
– Drugs: cocaine, amphetamines, LSD, alcohol withdrawal can contribute.
🩺 Clinical Features
- 🌡️ Core body temperature >40°C
- 🧠 CNS dysfunction: anxiety, confusion, delirium, bizarre behaviour, hallucinations, seizures, coma
- 💦 Sweating may be present (exertional) or absent (classic/late presentation)
- ❤️ Hypotension, tachycardia, shock in severe cases
🔎 Investigations
- 🧪 FBC: raised WCC (exclude infection)
- 🧪 U&E: AKI, hypokalaemia, hypophosphataemia
- 💪 CK: ↑ in exertional heat stroke (rhabdomyolysis)
- 🩸 LFTs: ↑ AST = poor prognostic indicator
- 🫁 VBG/ABG: respiratory alkalosis ± lactic acidosis (exertional)
⚠️ Complications
- 🧠 Encephalopathy, cerebral oedema
- 💪 Rhabdomyolysis → renal failure
- 🫁 Acute respiratory distress syndrome (ARDS)
- ❤️ Myocardial injury, circulatory collapse
- 🩸 Disseminated intravascular coagulation (DIC)
- 🧪 Hepatic & pancreatic injury
- 🩻 Intestinal ischaemia & infarction
🔍 Differentials
- 💉 Malignant hyperthermia (post-anaesthesia)
- 🧠 Neuroleptic malignant syndrome (antipsychotics)
- 💊 Drug-induced hyperthermia (stimulants, serotonergic drugs)
- 🦠 Infection: meningitis, encephalitis, sepsis
- 🦴 Endocrine: thyroid storm, phaeochromocytoma
- 🧠 CNS lesions: hypothalamic bleed, hydrocephalus
🛡️ Prevention
- 💧 Stay hydrated; avoid alcohol excess
- 🚫 Limit strenuous activity in hot/humid weather
- 🧢 Rest in cool, shaded, or air-conditioned areas
- 👕 Wear lightweight, loose clothing
- ⏳ Gradually acclimatise to heat exposure
- 👀 Monitor for early symptoms of heat illness and intervene promptly
💊 Management
- 🫁 ABCs, IV access, monitor core body temperature (rectal probe)
- 💧 IV fluids for dehydration and shock
- ❄️ Rapid cooling = main treatment goal
– Immersion in ice water baths (fastest, but poorly tolerated long-term)
– Tepid water spray (≈40°C) + fans for evaporative cooling
– Ice packs to axillae, groin, neck
- 🎯 Target core temperature: <39°C (safe threshold)
- 💊 Dantrolene is not indicated (used in malignant hyperthermia, not heat stroke)
- 🩸 Monitor/treat rhabdomyolysis (fluids, urine alkalinisation if severe)
- ⚠️ ICU support may be required for multiorgan failure
📌 Exam Pearl: The key difference is that exertional heat stroke often has profuse sweating and occurs in young fit individuals, whereas classic heat stroke often occurs in elderly/comorbid patients with impaired heat dissipation.
