Young, healthy individuals (athletes, military recruits, outdoor laborers).
Strenuous physical exertion in hot/humid environments with inadequate acclimation.
Non-Exertional / Classic Heat Stroke (NEHS):
Extremes of age (elderly, infants), poor socioeconomic status (lack of air conditioning during heatwaves), chronic medical illness (CVD, psychiatric illness).
ECG: Sinus tachycardia, conduction abnormalities, QT prolongation, or signs of hyperkalemia.
Chest X-ray: Rule out noncardiogenic pulmonary edema (ARDS) or aspiration.
CT Head / Lumbar Puncture: Indicated only if CNS dysfunction persists post-cooling to rule out alternative intracranial pathology or meningitis.
Differential Diagnostics
Heat Exhaustion vs. Heat Stroke:
Diff by core temp < 40°C and normal mental status in heat exhaustion.
Neuroleptic Malignant Syndrome (NMS):
Diff by history of dopamine antagonists (e.g., haloperidol, fluphenazine), “lead-pipe” muscle rigidity, hyporeflexia, and leukocytosis.
Serotonin Syndrome (SS):
Diff by history of serotonergic agents (SSRIs, SNRIs, MAOIs, tramadol), hyperreflexia, neuromuscular clonus (ocular/ankle), and prominent GI symptoms (diarrhea).
Malignant Hyperthermia (MH):
Diff by intraoperative or immediate postoperative onset following volatile halogenated inhalational anesthetics (e.g., sevoflurane) or succinylcholine; severe generalized rigidity and hypercapnia.
Thyroid Storm:
Diff by signs of hyperthyroidism (goiter, exophthalmos, high lid lag, atrial fibrillation), suppressed TSH, elevated free T4/T3.
Anticholinergic Toxicity:
Diff by classic toxidrome: “Blind as a bat, mad as a hatter, red as a beet, hot as a hare, dry as a bone, full as a flask” (mydriasis, decreased bowel sounds, acute urinary retention).
Sepsis / Meningitis:
Diff by infectious source, meningeal signs (nuchal rigidity, Kernig/Brudzinski), and CSF pleocytosis.
Management
Immediate Priorities (ABCDE):
Airway protection (intubation if GCS ≤ 8 or active status epilepticus), high-flow supplemental oxygen, aggressive IV access.
Rapid Cooling (Target: Core temp < 39°C / 102.2°F within 30 minutes; discontinue cooling at 38.5°C to avoid rebound hypothermia):
Exertional Heat Stroke (EHS):
First-line: Ice water immersion (cold water immersion bath is gold standard).
Second-line / Alternative: Evaporative/convective cooling if immersion tub is unavailable.
Non-Exertional Heat Stroke (NEHS):
First-line: Evaporative and convective cooling (continuous misting with lukewarm water [20–25°C] combined with large electric fans).
Note: Ice water immersion is poorly tolerated and associated with higher mortality in elderly patients due to severe shivering, peripheral vasoconstriction, and precipitation of arrhythmias.
Fluid Resuscitation & Supportive Care:
Moderate room-temperature/cold IV crystalloids (0.9% Normal Saline or Ringer’s Lactate); avoid over-aggressive boluses in NEHS to prevent pulmonary edema.
Shivering control: IV Benzodiazepines (e.g., Lorazepam, Diazepam) to prevent secondary endogenous heat production and rhabdomyolysis.
Contraindication: Antipyretics (Acetaminophen, Aspirin) are ineffective (hypothalamic set point is normal) and contraindicated due to worsened hepatotoxicity and bleeding diathesis.
Refractory / Invasive Cooling:
Cold peritoneal lavage, gastric lavage, or extracorporeal life support (ECMO) in severe refractory cases.
Complications
Rhabdomyolysis with myoglobinuria leading to Acute Tubular Necrosis (ATN) / AKI.
Disseminated Intravascular Coagulation (DIC) due to thermal endothelial damage and systemic inflammatory response.