Heat Exhaustion

Other Names

• Heat Exhaustion

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Background

• This page refers to heat exhaustion, characterized by trouble continuing exercise, hyperthermia with normal neurological status

Epidemiology

• Most common form of heat related illness (need citation)

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Pathophysiology

• General
  • Characterized by the inability to maintain adequate cardiac output due to strenuous physical exercise and environmental heat stress
  • Most often this manifests as physical collapse during exercise
  • Body temperature is elevated, typically less than exertional heat stroke, but the patient is neurologically intact
  • Can be thought of as a more common, less severe form of Exertional Heat Stroke
• Clinical criteria
  • Athlete has obvious difficulty continuing with exercise
  • Core body temperature is usually 101 to 104ºF (38.3 to 40.0ºC) at the time of collapse
  • No significant neurological dysfunction (eg, seizure, altered consciousness, persistent delirium)

Associated Conditions

• Heat Syncope
  • Conditions may be difficult to distinguish clinically

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Risk Factors

• Unclear specifically for heat exhaustion
• See: Heat Related Illness Risk Factors

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Differential Diagnosis

Differential Diagnosis Heat Illness

• Minor
  • Milaria
  • Heat Edema
  • Sunburn
  • Heat Tetany
  • Heat Cramps
• Major
  • Heat Syncope
  • Heat Exhaustion
  • Exertional Heat Stroke
  • Rhabdomyolysis

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Clinical Features

• History
  • Patients endorse discomfort, anxiety,
  • Dizziness, lightheadedness, syncope may or may not occur
  • Weakness may be extreme
  • Profuse sweating, pallor, "prickly heat" sensations
  • Headache
  • Abdominal cramps, nausea, vomiting, diarrhea
  • Persistent muscle cramps
  • Dehydration and thirst
• Physical Exam
  • Tachycardia, hypotension
  • Core temperature: >37°C (98.6°F) but <40°C (104°F)
  • The patient should be neurologically intact
  • Ataxia and coordination problems can be mild and should rapidly improve

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Evaluation

• Clinical diagnosis
  • Based on history, physical exam and presence of hyperthermia

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Classification

• Not applicable

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Management

• General
  • Remove any athlete from play
  • Move them to a shaded, cool or air-conditioned area
  • Place the patient supine with their feet elevated above the level of their head (ie, raise their legs)
  • Remove excess clothing and equipment
  • Cool the patient until their rectal temperature is approximately 101ºF (38.3ºC).
• Cooling
  • Mode of cooling less important for heat exhaustion compared to heat stroke (goal: comfort rather than life-saving)
  • Any technique may be used (cold water immersion, running cool water over them using a shower or hose, evaporative cooling measures)
  • Time to reach the goal temperature shorter than with heat stroke
• Hydration
  • Rehydrate the patient with chilled water or a sports drink if they will tolerate orallly
  • Give IV fluid if the athlete is unable to drink
• Monitor
  • Continuously observe and re-evaluate patient for mental status changes
  • Monitor vitals: heart rate, blood pressure, respiratory rate, rectal temperature
• Transport to Emergency Department
  • Indicated if patient does not rapidly improve with appropriate treatment
  • Also indicated if patient is altered or has evidence of end neurological dysfunction
• Transition to Exertional Heat Stroke
  • If core temperature rises above 40ºC or if patient develops altered mentation, the physician should transition to EHS care algorithm

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Rehab and Return to Play

Rehabilitation

• Not applicable

Return to Play/ Work

• General
  • There are no clear and validated guidelines for return to play
  • Individuals should abstain from exercise for at least 24 hours following the resolution of all symptoms and laboratory abnormalities.

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Complications and Prognosis

Prognosis

• Generally considered a self limited condition

Complications

• Exertional Heat Stroke
  • Some patients may have early EHS

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See Also

• Heat Related Illness Main

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