Heat exhaustion

Background

Known heat exposure with temperature 37-40C with:

• Tachycardia
• Sweating (especially when associated with exercise)
• Nausea or vomiting
• Headache
• Fatigue, weakness
• Dizziness
• Orthostatic hypotension with normal mental status

Etiology

• Occurs via water depletion or sodium depletion or combination
• Water depletion occurs in elderly and persons working in hot environments
• Salt depletion occurs when fluid losses are replaced with hypotonic solutions

Diagnosis

Labs

• Evidence of hemoconcentration
• May be hyponatremic, isotonic or hypernatremic
  • Depending on ratio of fluid and electrolyte loss to intake

Differential Diagnosis

Environmental heat diagnoses

• Heat cramps
• Heat edema
• Heat exhaustion
• Heat tetany
• Heat stroke
• Heat syncope
• Miliaria
• Hyperthermia

Treatment

• Removal from heat-stressed environment
• Volume and electrolyte replacement
  • Oral versus IV depending on severity
• Aggressive cooling to 39C if patient does not respond to 30min of fluid replacement

Disposition

• Majority of patients can be discharged
• Consider admision in pts with CHF or severe electrolyte disturbances

Complications

Rhabdomyolysis

See Also

• Heat Stroke
• Heat Emergencies

Source

Waters T. Heat Emergencies In: Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. McGraw Hill Medical. 2011: 1339