Heat-Related Illnesses

Heat Illness Intro - Body's Thermostat Glitches

• Body's thermostat: Hypothalamus (anterior preoptic area) maintains core body temperature (CBT) around 37°C (98.6°F).
• Heat balance:
  • Loss: Sweating (evaporation - primary), vasodilation, radiation, convection.
  • Gain: Metabolism, environment (↑temp, ↑humidity, ↓air movement, direct sun).
• "Glitches" occur when:
  • Heat load (exertional/environmental) overwhelms dissipation capacity.
  • Thermoregulatory mechanisms fail (e.g., impaired sweating, cardiovascular insufficiency).
• Consequences: ↑CBT, cellular damage, Systemic Inflammatory Response Syndrome (SIRS).
• Spectrum: Heat cramps → Heat exhaustion → Heat stroke.

⭐ Heat stroke is a medical emergency defined by a core body temperature > 40°C (104°F) accompanied by central nervous system dysfunction (e.g., delirium, seizures, coma).

Heat Syndromes Spectrum - From Mild to Mayhem

Heat illnesses range from minor to life-threatening. Early recognition is key.

• Core issue: Failed thermoregulation due to heat stress ± exertion.

⭐ Heat exhaustion is distinguished from heat stroke by the absence of significant CNS dysfunction (e.g., delirium, coma, seizures) and core body temperature typically below 40°C (104°F).

• Untreated exhaustion can progress to heat stroke (medical emergency).

Heat Stroke Alert - Code Red Emergency

• Definition: Core body temperature > 40°C (104°F) AND Central Nervous System (CNS) dysfunction (delirium, seizures, coma). A true medical emergency.
• Two Main Types:
  • Classic (Non-Exertional): Affects vulnerable (elderly, chronic illness). Skin: hot, red, DRY. Gradual onset.
  • Exertional: Affects young, healthy individuals during intense activity. Skin: often SWEATY. Rapid onset. High risk of rhabdomyolysis.
• Pathophysiology: Thermoregulatory failure → systemic inflammation → multi-organ damage (MODS).
• Key Diagnostic Markers:
  • Rectal temperature for accurate core temp.
  • Labs: ↑CK (esp. exertional), ↑LFTs, ↑Renal markers, coagulopathy (DIC).
• Severe Complications: ARDS, DIC, rhabdomyolysis, AKI, hepatic failure, cerebral edema.

⭐ Antipyretics (e.g., paracetamol, aspirin) are INEFFECTIVE in heat stroke as the hypothalamic set point is normal; they may worsen liver/coagulation issues.

Management & Prevention - The Chill Protocol

• Heat Cramps/Exhaustion: Oral rehydration (ORS), rest, cool down. IV fluids if severe.
• Heat Stroke: Emergency!
  • ABCs: Airway, O2, IV access.
  • Rapid Cooling: Target core temp <39°C (<102.2°F) ASAP.
    • Evaporative: Spray water + fan.
    • Immersion: Ice water (1-15°C). (Most effective)
    • Invasive: Cooled IV fluids.
  • Supportive: Monitor vitals, electrolytes. Avoid antipyretics.
  • 📌 Cool First, Transport Second (CFTS).

⭐ Antipyretics (e.g., paracetamol) are ineffective in heat stroke; the primary issue is failed thermoregulation, not a changed hypothalamic set point.

• Prevention:
  • Acclimatization (7-14 days).
  • Hydration: Adequate fluid intake.
  • Avoid peak heat; wear light, loose clothing.

High‑Yield Points - ⚡ Biggest Takeaways

• Heat cramps: Electrolyte imbalance (esp. Na+); normal core temp; oral rehydration with electrolytes.
• Heat exhaustion: Core temp < 40°C; profuse sweating, fatigue, CNS intact; cooling, IV/oral fluids.
• Heat stroke: Core temp > 40°C; altered mental status (key sign); medical emergency.
• Exertional H.S. (young, active, often sweating) vs. Classic H.S. (elderly, ill, often anhidrotic).
• Heat stroke management: Immediate rapid cooling (evaporative/ice immersion); antipyretics are contraindicated.
• Major complications: Rhabdomyolysis, DIC, ARDS, multi-organ dysfunction_