Heat Exhaustion and Heat Stroke
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- A continuum of increasingly severe heat illnesses caused by dehydration, electrolyte losses, and failure of the body’s thermoregulatory mechanisms:
- Heat exhaustion is an acute heat injury with hyperthermia owing to dehydration.
- Heat stroke is extreme hyperthermia with thermoregulatory failure and profound CNS dysfunction.
- System(s) affected: Endocrine/Metabolic; Nervous
- Synonym(s): Heat illness; Heat injury; Hyperthermia; Heat collapse; Heat prostration
Elderly persons are more susceptible.
Children are more susceptible.
Pregnant women may be more susceptible to volume depletion with heat stress.
- Predominant age: More likely in children or elderly
- Predominant sex: Male = Female
Depends on intensity of heat; estimate of 20/100,000 persons per season
- Depends on predisposing conditions in combination with environmental factors
- Roughly 240 deaths/year in the US
- Poor acclimatization to heat or poor physical conditioning
- Salt or water depletion
- Acute febrile or GI illnesses
- Chronic illnesses: Uncontrolled diabetes mellitus or hypertension, cardiac disease
- Alcohol and other substance abuse
- High heat and humidity, poor air circulation in environment
- Heavy, restrictive clothing
- Nutritional supplementation that includes ephedra
- The most important factor in preventing heat stress is adequate fluid replacement.
- Allow acclimatization to hot weather through proper conditioning and activity modification.
- Dress appropriately with loose-fitting, open-weave, light-colored clothing.
Direct cellular toxicity of heat, imbalance between inflammatory and anti-inflammatory cytokines, and vascular endothelial damage causing end-organ dysfunction.
Interplay between failure of heat-dissipating mechanisms, an overwhelming heat stress, and an exaggerated acute-phase inflammatory response.