II. Pathophysiology

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

III. Causes: Increased endogenous heat load

  1. Vigorous Exercise or overexertion
  2. Sympathomimetic drugs (see below)
  3. Caffeine

IV. Causes: Increased Exogenous Heat load

V. Causes: Decreased Heat Dissipation

  1. Exogenous cause
    1. Humidity
    2. Occlusive or excessive clothing
  2. Endogenous cause
    1. Dehydration
    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: Other predisposing factors for abnormal heat balance

  1. Prior Heat Stroke
  2. Concurrent infection
    1. Upper Respiratory Infection
    2. Gastroenteritis
  3. Age over 65 years
    1. Myocardial dysfunction
    2. Decreased muscle mass
    3. Decreased skin blood supply
    4. Renal Insufficiency
    5. Chronic illness
  4. Children
    1. Generate greater metabolic heat during Exercise
    2. Slower acclimitization
    3. Decreased sweat response
    4. Increased surface area to body mass ratio
  5. Comorbid medical condition
    1. Anorexia
    2. Cystic Fibrosis
    3. Diabetes Insipidus
    4. Poorly controlled Diabetes Mellitus
    5. Obesity
    6. Hypokalemia
    7. Sickle Cell Trait or Sickle Cell Anemia

VII. References

  1. Czerkawski (1996) Your Patient Fitness 10(4): 13-20
  2. Sandor (1997) Physician SportsMed, 25(6):35-40
  3. Barrow (1998) Am Fam Physician 58(3):749-56 [PubMed]
  4. Hett (1998) Postgrad Med 103(6):107-20 [PubMed]
  5. Wexler (2002) Am Fam Physician 65(11):2307-20 [PubMed]

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