II. Pathophysiology

  1. Predisposing conditions alter heat balance
  2. See Temperature Regulation

III. Causes: Increased endogenous heat load

  1. Vigorous Exercise or overexertion (without adequate breaks for rest)
  2. Sympathomimetic drugs (see below)
  3. Caffeine

IV. Causes: Increased Exogenous Heat load

  1. Sun Exposure (without shelter or shade)
  2. Increased Heat Index (excessive heat and humidity)
  3. Enclosed Vehicle Excessive Heat

V. Causes: Decreased Heat Dissipation

  1. Exogenous cause
    1. Humidity
      1. Evaporation of sweat stops at 75% humidity (and sweating has no cooling effect at 95% humidity)
    2. Occlusive or excessive clothing
  2. Endogenous cause
    1. Dehydration (and lack of adequate water access)
    2. Lack of acclimatization
    3. Poor physical conditioning
    4. Healed burns
    5. Sunburn
    6. Dermatitis
    7. Sweat Gland Dysfunction
    8. See Medications Predisposing to Heat Illness

VI. Causes: Occupations and Activities

  1. Athletes (highest rates with football)
  2. Military
  3. Outdoor workers
    1. Farming
    2. Construction workers
    3. Firefighters

VII. Causes: Other predisposing factors for abnormal heat balance

  1. Medications Predisposing to Heat Illness
  2. Prior Heat Stroke
  3. Body habitus
    1. Male gender
    2. Large muscle mass
    3. Obesity
    4. Deconditioning and sedentary lifestyle
  4. Concurrent infection
    1. Upper Respiratory Infection
    2. Gastroenteritis
  5. Age over 65 years
    1. Myocardial dysfunction
    2. Vascular disease
    3. Decreased muscle mass
    4. Decreased skin blood supply
    5. Renal Insufficiency
    6. Chronic illness
    7. Decreased mobility
  6. Children (especially tightly bundled infants)
    1. See Enclosed Vehicle Excessive Heat
    2. Generate greater metabolic heat during activity and at rest (higher basal metabolic rate)
    3. Slower acclimitization
    4. Decreased sweat response and capacity
    5. Increased surface area to body mass ratio (greater heat absorption)
    6. Decreased Blood Volume to redistribute to the periphery
    7. Immature Hypothalamus (less able to Temperature regulate)
  7. Congenital disorders
    1. Ectodermal dysplasia
    2. Idiopathic anhidrosis
  8. Comorbid medical condition
    1. Anorexia
    2. Cystic Fibrosis
    3. Diabetes Insipidus
    4. Heart disease
    5. Poorly controlled Diabetes Mellitus
    6. Hypokalemia
    7. Sickle Cell Trait or Sickle Cell Anemia

VIII. References

Images: Related links to external sites (from Bing)

Related Studies (from Trip Database) Open in New Window