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 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. Ebi KL, Capon A, Berry P, et al. Hot weather and heat extremes: health risks. Lancet 2021; 398:698. Epstein Y, Yanovich R. Heatstroke. N Engl J Med 2019; 380:2449. 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. Khosla R, Guntupalli KK. Heat-related illnesses. Crit Care Clin 1999; 15:251. 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