Description

• 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

Geriatric Considerations
Elderly persons are more susceptible.

Pediatric Considerations
Children are more susceptible.

Pregnancy Considerations
Pregnant women may be more susceptible to volume depletion with heat stress.

Epidemiology

• Predominant age: More likely in children or elderly
• Predominant sex: Male = Female

Incidence
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

Risk Factors

• Poor acclimatization to heat or poor physical conditioning
• Salt or water depletion
• Obesity
• 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

General Prevention

• 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.

Pathophysiology

Direct cellular toxicity of heat, imbalance between inflammatory and anti-inflammatory cytokines, and vascular endothelial damage causing end-organ dysfunction.

Etiology

Interplay between failure of heat-dissipating mechanisms, an overwhelming heat stress, and an exaggerated acute-phase inflammatory response.