Heat Exhaustion

Aka: Heat Exhaustion

1. See Also
   1. Heat Illness
   2. Heat Edema
   3. Heat Cramps
   4. Heat Exhaustion
   5. Heat Stroke
   6. Temperature Regulation
   7. Heat Index
   8. Heat Illness Risk Factors
   9. Medications Predisposing to Heat Illness
   10. Heat Illness Prevention
2. Mechanisms
   1. Dehydration
   2. Electrolyte loss
   3. Exercise-induced Respiratory Alkalosis
3. Symptoms
   1. Fatigue
   2. Weakness
   3. Nausea and Vomiting
   4. Dizziness
   5. Myalgias
   6. Irritability
   7. Headache
   8. Dyspnea
4. Signs
   1. Temperature increased between 100.4 F (38 C) to 104 F (40 C)
   2. Hypotension or Orthostasis
   3. Syncope
   4. Sweating
   5. Cutaneous Flushing
   6. Decreased urine output
   7. Mild neurologic changes
      1. Incoordination
      2. Confusion
      3. Irritability
      4. Mental status not seriously impaired
         1. Contrast with Heat Stroke
5. Labs
   1. Evaluate for Rhabdomyolysis
      1. Urine blood positive on dipstick (but negative microscopy) suggests myoglobin
      2. Creatinine phosphokinase increased
   2. Normal Liver Function Tests (contrast with Heat Stroke)
      1. AST Normal
      2. ALT Normal
      3. LDH Normal
   3. Monitoring with fluid Resuscitation
      1. Serum Sodium
      2. Serum Potassium
      3. Serum phosphate
      4. Serum Calcium
      5. Serum Magnesium
6. Management
   1. External cooling
      1. Cool environment
      2. Remove excess clothing
      3. Spray lukewarm water on body
      4. Cool with fans
   2. Gradual rehydration
      1. Manage Hypernatremia or Hyponatremia if present
      2. Manage Rhabdomyolysis if present
      3. Oral Rehydration (Mild cases)
         1. 1 Liter per hour over several hours
      4. Intravenous Rehydration
         1. Initial isotonic fluid replacement (NS or LR)
         2. Replace 50% total water deficit in first 3-6 hours
         3. Replace remaining 50% deficit over 6-9 hours
7. Management: Playing field sideline
   1. Remove excess clothing
   2. Move to shaded environment
   3. Place supine with legs elevated
   4. Encourage oral fluids
   5. Obtain vital signs (be alert for Tachycardia or Hypotension)
   6. Persistent symptoms or signs >20 minutes should prompt emergency department care
8. Prevention
   1. See Heat Illness Prevention
9. 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
   4. Hett (1998) Postgrad Med 103(6):107-20
   5. Wexler (2002) Am Fam Physician 65(11):2307-20