Heat-Related Illnesses

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Introduction & Pathophysiology - Sizzling Science

  • Thermoregulation: Body balances heat gain (metabolism, environment) & loss (radiation, conduction, convection, evaporation).
    • Acclimatization: Physiological adaptation to heat over days/weeks (↑sweat rate, ↓electrolyte loss).
  • Pathophysiology: Excessive heat → thermoregulatory failure → hyperthermia.
    • Cellular injury (protein denaturation, membrane damage) → organ dysfunction.
    • Systemic Inflammatory Response Syndrome (SIRS) can occur.

Heat exchange mechanisms between human body and environment

  • Risk Factors:
    • Extremes of age (infants, elderly >65 yrs).
    • Chronic diseases (CVD, diabetes, respiratory).
    • Medications (diuretics, anticholinergics, β-blockers, antipsychotics).
    • Dehydration, obesity, alcohol.
    • High humidity, strenuous exertion, lack of acclimatization.

⭐ Evaporation is the primary heat loss mechanism, significantly impaired by high humidity (>75%).

Spectrum & Diagnosis - Degrees of Danger

FeatureHeat CrampsHeat SyncopeHeat ExhaustionHeat Stroke (Classic/Exertional)
Core TempNormal/Slight ↑Normal/Slight ↑<40°C>40°C
CNSAlertTransient LOC/dizzyFatigue, weakness, headache; No severe CNSSevere CNS (delirium, seizures, coma)
SkinNormalCool, moistProfuse sweat; Cool/clammyClassic: Hot, DRY. Exertional: SWEATY.
MusclesSpasms (legs, abd)-MyalgiaRhabdo (exertional)
CVSNormalOrthostatic hypotensionTachycardia, hypotensionTachycardia, hypotension → shock
GIT--Nausea, vomitingNausea, vomiting
Key FeaturesIsolated cramps; Normal tempBrief LOC post-exertionSystemic; Temp <40°C; No severe CNS. Water/salt depletion.Temp >40°C; Severe CNS. EMERGENCY.

⭐ Defining feature: Heat stroke vs. exhaustion is CNS dysfunction (AMS, seizures, coma) & core temp >40°C.

Management Principles - Chill & Conquer

  • General: ABCs, remove from heat, rest, cooling, fluid & electrolyte replacement.
  • Heat Cramps: Cool environment, ORS, gentle muscle stretching.
  • Heat Syncope: Supine, legs elevated, cool environment, oral fluids.
  • Heat Exhaustion: Cool place, oral rehydration (ORS). IV 0.9% saline if severe/vomiting. Monitor core temp.
  • Heat Stroke: ⚠️ EMERGENCY! IMMEDIATE AGGRESSIVE COOLING.
    • Target core temp: ~39°C (102.2°F).
    • Methods: Evaporative (tepid water + fan), ice packs (neck, axillae, groin), cooling blankets, cold water immersion.
    • IV isotonic crystalloids.
    • Manage complications (seizures: benzodiazepines).
    • ⚠️ Antipyretics (paracetamol, aspirin) NOT effective/harmful.

Cold water immersion for heat stroke

⭐ In heat stroke management, rapid cooling to a target core temperature of ~39°C is paramount; antipyretics are ineffective.

Prevention & Control - Beat The Heat

  • Individual Measures: Acclimatize (gradual exposure); hydrate regularly (avoid alcohol/caffeine); wear light-colored, loose-fitting clothes; schedule outdoor activities in cooler parts of day; use sunscreen; never leave children/pets in parked cars.
    • 📌 AVOID HEAT: Acclimatize, Ventilate, Overhydration (avoid, but hydrate well!), Inform (stay informed), Dress light, Hydrate, Energy (conserve), Activity (limit peak heat), Time (schedule wisely).
  • Community/Public Health Measures: Heat Action Plans (HAPs), Heat Health Warning Systems (HHWS), public cooling centers, urban planning (green spaces), awareness campaigns.
  • Focus on Vulnerable Populations: Elderly, infants/young children, pregnant women, outdoor workers, athletes, individuals with chronic conditions. Heat Illness Prevention Strategies Infographic

⭐ Acclimatization, achieved over 7-14 days of heat exposure, significantly improves physiological tolerance to heat stress by enhancing sweating efficiency and cardiovascular stability.

High‑Yield Points - ⚡ Biggest Takeaways

  • Heat stroke: life-threatening, core temp >40°C with altered mental status.
  • Heat exhaustion: core temp <40°C, fatigue, no major CNS issues.
  • Heat stroke management: immediate rapid cooling (evaporative/immersion).
  • Acclimatization over 7-14 days is key for prevention.
  • High-risk: elderly, infants, chronic diseases, certain drugs (e.g., diuretics, anticholinergics).
  • Heat cramps: painful spasms from electrolyte loss; treat with oral saline.
  • Prickly heat (miliaria): blocked sweat ducts; keep skin cool, dry.

Practice Questions: Heat-Related Illnesses

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An individual is in an environment of a temperature of 47°C. What is the mechanism of heat loss?

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Flashcards: Heat-Related Illnesses

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Most common disease post disaster is _____

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Most common disease post disaster is _____

Acute Gastroenteritis

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