Heat Stroke

1. Hyperthermia - core temperature >40°C (>104°F)
2. Altered mental status

Types

The clinical distinction between the two types is not critical for management - immediate cooling is the priority for both.

Clinical Features

• The cerebellum is highly heat-sensitive; ataxia is an early sign
• Irritability, confusion, bizarre behavior, combativeness, hallucinations
• Decorticate/decerebrate posturing, hemiplegia, status epilepticus, coma
• Seizures are common, especially during cooling

• Tachycardia, widened pulse pressure, arrhythmia
• Hypotension (common initial finding)

• Tachypnea (PaCO2 often <20 mmHg from hyperventilation)
• Nausea/vomiting, oliguria
• Rhabdomyolysis, muscle cramps, flaccidity
• Lactic acidosis and hypoglycemia in exertional type

Diagnosis

• CBC, comprehensive metabolic panel, ABG
• Coagulation profile (PT, PTT, fibrinogen)
• CPK, myoglobin, urinalysis (rhabdomyolysis screen)
• ECG, chest X-ray
• Head CT and LP if needed to rule out other causes

Management

Prehospital

• Remove from hot environment immediately
• Remove clothing
• Start cooling: spray water + airflow (preferred), wet towels/sheets, or ice packs
• IV normal saline 1-2 L bolus if hypotensive
• Check point-of-care glucose

Emergency Department

• Monitor core temperature continuously (rectal thermometer, Foley thermistor, or esophageal probe)
• Target: reduce core temperature to ~39°C (102.2°F) - avoid overshoot hypothermia

Cooling Techniques (none proven superior):

• Shivering during cooling: treat with short-acting benzodiazepines (first-line) or phenothiazines (second-line - note: lower seizure threshold, cause hypotension)
• Seizures: benzodiazepines

Hemodynamics:

• IV fluids for hypotension; if low cardiac output + elevated CVP persists after 20 mL/kg bolus - add dopamine or dobutamine
• Avoid norepinephrine (alpha-adrenergic vasoconstriction redirects blood away from skin, impairing cooling)

Complications

Early

• Hypotension, hypothermic overshoot, hyperthermic rebound
• Rhabdomyolysis, oliguria
• Delirium/coma, seizures
• Heart failure, pulmonary edema
• Hypokalemia, hypernatremia/hyponatremia

Late

• Renal failure (direct thermal injury + rhabdomyolysis + volume depletion)
• DIC (thermal endothelial injury → platelet aggregation, clotting factor deactivation)
• Hepatic dysfunction - centrilobular necrosis; peaks at 24-72 hours post-insult (usually reversible)
• ARDS
• Cerebral edema, persistent neurologic deficits
• Myocardial injury, intestinal ischemia, pancreatic injury
• Hyperkalemia (from AKI + rhabdomyolysis), hypocalcemia, hyperuricemia

Disposition

• Heat stroke → ICU admission (especially if intubated, hemodynamically unstable, requiring invasive monitoring, or ongoing cooling)
• Minor heat emergencies (heat cramps, heat edema, heat stress) → ED treatment + discharge with instructions

Special Populations

• Elderly: Higher mortality; impaired thermoregulation, immobility, polypharmacy (diuretics, anticholinergics), poor housing insulation
• Young children: Immature thermoregulatory system; cannot self-rescue from hot environments (e.g., closed cars)
• Adolescents/athletes: Poor judgment in heat; require 10-14 days of acclimatization before intense activity - most early-season deaths occur in the first 4 days of practice

Prevention

1. Reschedule strenuous activity to cooler times of day
2. Wear light, loose-fitting clothing
3. Increase carbohydrates, decrease protein intake (reduces endogenous heat production)
4. Drink fluids proactively (even when not thirsty)
5. Avoid alcohol
6. Avoid direct sunlight; use shade
7. Allow adequate acclimatization (10-14 days for athletes)