What are the symptoms, signs, and diagnosis of heat exhaustion vs heat stroke?

Heat Exhaustion vs Heat Stroke: Symptoms, Signs, and Diagnosis

Heat exhaustion and heat stroke represent different points on the heat illness spectrum, with heat stroke being a life-threatening emergency requiring immediate cooling and medical intervention, while heat exhaustion is a moderate condition characterized by cardiovascular strain without central nervous system dysfunction. 1

Heat Exhaustion

Symptoms and Signs

• Weakness
• Dizziness
• Nausea
• Syncope (fainting)
• Headache
• Fatigue
• Heavy sweating 1
• Inability to maintain blood pressure and sustain adequate cardiac output 2
• Core body temperature up to 104°F (40°C) 2, 1
• Normal mental status (key distinguishing feature from heat stroke) 1

Diagnosis

Heat exhaustion is diagnosed clinically based on:

• Exposure to environmental heat or strenuous physical activity
• Presence of characteristic symptoms
• Core temperature ≤104°F (40°C)
• Absence of central nervous system dysfunction 3

Heat Stroke

Symptoms and Signs

• All symptoms of heat exhaustion plus:
• Central nervous system abnormalities (key diagnostic feature)
  • Delirium
  • Confusion
  • Convulsions
  • Coma 2, 1
• Core temperature ≥104°F (≥40°C) 2, 1, 4
• Endotoxemia
• Circulatory failure
• Temperature-control dysregulation
• Potential organ and tissue damage 2
• May lead to cardiac arrest, rhabdomyolysis, and acute renal failure 4

Diagnosis

Heat stroke is diagnosed when the following are present:

• Core body temperature ≥104°F (≥40°C)
• Central nervous system dysfunction
• History of heat exposure or strenuous activity 5

Key Differences Between Heat Exhaustion and Heat Stroke

Feature	Heat Exhaustion	Heat Stroke
Mental Status	Normal	Altered (confusion, delirium, seizures, coma)
Core Temperature	Up to 104°F (40°C)	≥104°F (≥40°C)
CNS Involvement	No	Yes
Severity	Moderate	Severe, life-threatening
Organ Dysfunction	No	Potential multi-organ failure
Mortality Risk	Low with proper treatment	High if not rapidly treated

Management Approach

Heat Exhaustion Treatment

1. Move to a cool place
2. Remove excess clothing
3. Lie down in a cool place
4. Apply cool water spray to skin
5. Drink cool fluids containing electrolytes and carbohydrates 2, 1
6. Monitor for progression to heat stroke 3

Heat Stroke Treatment

1. Activate emergency medical services immediately 2, 1
2. Begin rapid cooling without delay:
   • Cold/ice-water immersion (preferred method) 2, 1
   • If immersion not possible: apply ice packs to neck, axillae, and groin 2
   • Continue cooling until core temperature reaches just under 39°C (102°F) or neurological symptoms improve 2, 1
3. Remove protective equipment and clothing 2
4. Monitor for complications (cardiac arrest, organ failure) 4

Important Clinical Considerations

• Speed of cooling is directly related to survival in heat stroke - faster cooling results in better outcomes 1, 6
• Rectal temperature measurement is the preferred method for accurate core temperature assessment 2
• Do not delay treatment while waiting for core temperature verification 2
• High-risk populations include:
  • Children and adolescents
  • Elderly
  • Obese individuals
  • Those with chronic diseases
  • Individuals taking certain medications (diuretics, antihypertensives) 2, 7
• Heat stroke can occur in previously cooler regions during heat waves, so awareness is crucial even in temperate climates 7

Prevention Strategies

• Acclimatization to heat (may take 12-14 days) 2, 1
• Adequate hydration before, during, and after exercise 2
• Avoiding strenuous activity during extreme heat 2
• Wearing appropriate loose-fitting, light-colored clothing 2, 1
• Taking regular breaks in cool environments 1
• Adjusting exercise intensity based on environmental conditions 2

Remember that heat stroke is a true medical emergency with high mortality if not treated promptly. The key distinguishing feature between heat exhaustion and heat stroke is the presence of central nervous system dysfunction in heat stroke.