Heat exhaustion

Background

Results from exposure to excessive heat or exposure to extreme temperature for prolonged period of time.

• Can result from exposure to heat wave
• Predicted to increase due to increasing climate temperatures

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

Clinical Features

Man with signs of heat exhaustion, including copious sweating.

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
• Mentation is normal (in contrast to heatstroke)

Differential Diagnosis

Environmental heat diagnoses

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

Evaluation

Workup

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

Diagnosis

• Typically a clinical diagnosis

Treatment

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

Disposition

• Majority of patients can be discharged
• Consider admission in patients with CHF or severe electrolyte disturbances
• If not treated properly, may evolve to Heat Stroke

Complications

• Rhabdomyolysis

See Also

• Heat Stroke
• Heat Emergencies