Heat Stroke 

Heat stroke is a life-threatening medical emergency characterized by:

• Core temperature ≥ 40°C
• Central nervous system dysfunction
• Multiorgan failure
• Systemic inflammatory response resembling sepsis

Definition

Heat stroke = Failure of thermoregulation leading to extreme hyperthermia and organ dysfunction.

Core temperature > 40°C + altered mental status is diagnostic in appropriate clinical context.

Classification

1. Classical (Non-Exertional) Heat Stroke

• Occurs during heat waves
• Affects elderly, children, chronically ill
• Develops gradually over hours–days
• Impaired sweating common

2. Exertional Heat Stroke (EHS)

• Occurs in young healthy individuals
• Intense physical activity in hot/humid climate
• Sweating may be present
• Rapid onset
• Severe rhabdomyolysis common

Seen in:

• Marathon runners
• Military recruits
• Construction workers
• Athletes

 Pathophysiology

Heat stroke is not just hyperthermia — it is cytokine-mediated multiorgan failure.

Step 1: Thermoregulatory Failure

Normally regulated by hypothalamus.
In heat stroke:

• Heat gain > heat dissipation
• Core temp rises uncontrollably

Step 2: Direct Thermal Injury

Proteins denature above 41–42°C → cellular dysfunction.

Affected organs:

• Brain
• Liver
• Kidneys
• Endothelium

Step 3: Systemic Inflammatory Response (SIRS-like)

Similar to sepsis:

• TNF-α
• IL-1
• IL-6
• Endotoxin translocation from gut

→ Endothelial injury
→ Capillary leak
→ Microthrombosis
→ DIC

Step 4: Coagulation Abnormality

• Platelet consumption
• ↑ PT/INR
• ↑ D-dimer
• ↓ Fibrinogen

DIC is common in severe cases.

Clinical Features

CNS Dysfunction (Universal)

• Agitation
• Delirium
• Seizures
• Coma
• Cerebellar signs (late)

Persistent cerebellar dysfunction is classic.

Skin

Sweating does NOT rule out heat stroke.

Cardiovascular

• Tachycardia
• Hypotension
• Vasodilation initially
• Later shock

Respiratory

• Hyperventilation
• ARDS in severe cases

Renal

• AKI
• Rhabdomyolysis (very common in EHS)
• Myoglobinuria

Hepatic

• Acute liver injury
• Acute liver failure
• ↑ AST/ALT (often > 1000)

 Laboratory Findings

• Core temp > 40°C
• Elevated CK (often > 10,000 in EHS)
• Metabolic acidosis
• Hyperkalemia
• Elevated creatinine
• Transaminitis
• Coagulopathy
• Hypoglycemia (may occur)
• Lactate elevated

 Differential Diagnosis of Hyperthermia

 Management 

 Rapid Cooling (Most Important Step)

Target:-Reduce core temp to 38.5–39°C ASAP

 Cold Water Immersion (Best for Exertional)

• Most effective
• Cooling rate: 0.15–0.2°C/min
• Stop when temp reaches 38.5°C

2️⃣ Evaporative Cooling

• Spray lukewarm water
• High airflow fan
• Ice packs (axilla, groin, neck)
• Cooling blankets

 What NOT to Do

• Do NOT give antipyretics (ineffective; not hypothalamic set-point problem)
• Avoid shivering (may require benzodiazepines)

 ICU Management

Airway

• Intubation if GCS < 8
• Prevent aspiration

Breathing

• Oxygen
• ARDS protocol if needed

Circulation

• IV crystalloids
• Vasopressors if shock persists

Rhabdomyolysis

• Aggressive IV fluids
• Maintain urine output > 1–2 mL/kg/hr
• Monitor potassium

DIC

• FFP, platelets as indicated

AKI

• RRT if needed

Acute Liver Failure

• Early transplant center referral

 Complications

• ARDS
• AKI
• DIC
• Acute liver failure
• Seizures
• Cerebellar damage
• Death

Mortality:

• Classical: up to 30–50%
• Exertional: lower if rapid cooling

 Prognostic Factors

Poor prognosis:

• Delay in cooling
• Temp > 42°C
• Persistent coma
• Severe coagulopathy
• Lactate > 4–6
• Acute liver failure

 Prevention

• Hydration
• Acclimatization
• Avoid peak heat hours
• Light clothing
• Occupational policies
• Early recognition of heat exhaustion

 Heat Stroke vs Heat Exhaustion