What are the pathology and symptoms of heat stroke?

Pathology and Symptoms of Heat Stroke

Heat stroke is a life-threatening medical emergency characterized by core body temperature above 40°C (104°F) and central nervous system dysfunction, requiring immediate cooling to prevent irreversible organ damage and death. 1

Pathophysiology of Heat Stroke

Heat stroke occurs when the body's thermoregulatory mechanisms fail, resulting in a cascade of pathological processes:

• Thermoregulatory failure: The body becomes unable to dissipate heat effectively through sweating and vasodilation
• Direct cellular damage: Excessive heat causes protein denaturation, enzyme dysfunction, and cell membrane damage
• Systemic inflammatory response: Heat exposure triggers release of inflammatory cytokines and endotoxemia
• Coagulopathy: Microvascular thrombosis and disseminated intravascular coagulation may develop
• Multi-organ dysfunction: Progressive damage affects multiple systems:
  • CNS: Most vulnerable to heat damage with cell death increasing exponentially as temperature exposure time increases 1
  • Cardiovascular: Circulatory failure and potential cardiovascular collapse 1
  • Hepatic: Liver enzyme elevations and potential liver failure 2
  • Renal: Acute kidney injury often from rhabdomyolysis 1
  • Gastrointestinal: Intestinal barrier dysfunction leading to endotoxemia 1
  • Muscular: Rhabdomyolysis with elevated CPK and myoglobinuria 2

Clinical Presentation and Symptoms

Heat stroke presents with two cardinal features:

1. Core temperature ≥40°C (104°F)
2. Central nervous system dysfunction including:
   • Altered mental status (confusion, delirium)
   • Seizures
   • Coma

Additional symptoms and signs include:

• Neurological: Dizziness, syncope, headache
• Cardiovascular: Tachycardia, hypotension
• Respiratory: Tachypnea
• Skin: May be hot and dry (classic heat stroke) or sweaty (exertional heat stroke)
• Gastrointestinal: Nausea, vomiting
• Laboratory abnormalities:
  • Elevated liver enzymes (SGOT, LDH)
  • Elevated creatine phosphokinase (CPK)
  • Hypophosphatemia
  • Coagulation abnormalities 2

Types of Heat Stroke

1. Classic (non-exertional) heat stroke:

   • Occurs in vulnerable populations (elderly, chronically ill)
   • Develops over days during heat waves
   • Often presents with dry skin (anhidrosis)
   • Mortality rates can reach 71.4% 1

2. Exertional heat stroke:

   • Occurs in healthy individuals during strenuous physical activity
   • Develops rapidly (hours)
   • Often presents with sweating still present
   • Mortality rates range from 0% to 26.5% 1

Clinical Course and Prognosis

Without prompt treatment, heat stroke can lead to:

• Mortality rates approaching 60% in patients requiring ICU care 1
• Approximately 30% of survivors experience long-term cognitive or motor dysfunction 1
• Permanent damage to brain, heart, liver, kidneys, intestine, spleen, or muscle 1

Management Principles

The most critical intervention is immediate cooling, with target core temperature below 39°C (102.2°F) within 30 minutes of symptom onset 1. Cold-water immersion (≤12°C) is the most effective cooling method 1.

Key Pitfalls to Avoid

1. Delayed recognition: Any altered mental status during heat exposure or exertion should prompt immediate evaluation for heat stroke
2. Delayed cooling: Treatment should not be delayed pending core temperature verification
3. Inadequate cooling: Using ineffective cooling methods when more effective options are available
4. Failure to monitor for complications: Multi-organ dysfunction can develop even after successful cooling

Heat stroke represents a medical emergency where rapid recognition and aggressive cooling are essential to prevent death and long-term neurological sequelae.