Episode 917: Heat-Related Illnesses

Contributor: Megan Hurley, MD

Educational Pearls:

• Heat cramps

• Occur due to electrolyte disturbances

• Most common electrolyte abnormalities are hyponatremia and hypokalemia

• Heat edema

• Caused by vasodilation with pooling of interstitial fluid in the extremities

• Heat rash (miliaria)

• Common in newborns and elderly

• Due to accumulation of sweat beneath eccrine ducts

• Heat syncope

• Lightheadedness, hypotension, and/or syncope in patients with peripheral vasodilation due to heat exposure

• Treatment is removal from the heat source and rehydration (IV fluids or Gatorade)

• Heat exhaustion

• Patients have elevated body temperature (greater than 38º C but less than 40º C)

• Symptoms include nausea, tachycardia, headache, sweating, and others

• Normal mental status or mild confusion that improves with cooling

• Treatment is removal from the heat source and hydration

• Classic heat stroke

• From prolonged exposure to heat

• Defined as a core body temperature > 40.5º C, though not required for diagnosis or treatment

• Presentation is similar to heat exhaustion with the addition of neurological deficits including ataxia

• Patients present "dry"

• Exertional heat stroke

• Prolonged exposure to heat during exercise

• Similar to classic heat stroke but the patients present "wet" due to antecedent treatment in ice baths or other field treatments

• Management of heat-related illnesses includes:

• Cooling

• Rehydration

• Evaluation of electrolytes

• Antipyretics are not helpful because heat-induced illnesses are not due to hypothalamic dysregulation

References

1. Casa DJ, McDermott BP, Lee EC, et al. Cold water immersion: the gold standard for exertional heatstroke treatment. Exerc Sport Sci Rev 2007; 35:141.

2. Ebi KL, Capon A, Berry P, et al. Hot weather and heat extremes: health risks. Lancet 2021; 398:698.

3. Epstein Y, Yanovich R. Heatstroke. N Engl J Med 2019; 380:2449.

4. Gardner JW, JA K. Clinical diagnosis, management, and surveillance of exertional heat illness. In: Textbook of Military Medicine, Zajitchuk R (Ed), Army Medical Center Borden Institute, Washington, DC 2001.

5. Khosla R, Guntupalli KK. Heat-related illnesses. Crit Care Clin 1999; 15:251.

6. Lipman GS, Gaudio FG, Eifling KP, et al. Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2019 Update. Wilderness Environ Med 2019; 30:S33.

Summarized by Jorge Chalit, OMSIII | Edited by Meg Joyce, MS1

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