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Heat Exhaustion

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Medical Author:

Benjamin Wedro, MD, FACEP, FAAEM

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

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Medical Editor:

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

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Heat exhaustion facts

• Heat exhaustion is one part of the spectrum of heat-related illnesses that include, heat cramps, heat exhaustion, and heat stroke.
  
  
• The body cools itself by sweating and allowing that sweat to evaporate. This requires enough fluid in the body to make sweat, air circulating across the skin, and low air humidity to allow that sweat to evaporate.
  
  
• Activity in a hot environment can overwhelm the body's ability to cool itself, causing heat-related symptoms.
  
  
• Symptoms of heat exhaustion include profuse sweating, weakness, nausea, vomiting, headache, lightheadedness, and muscle cramps.
  
  
• Heat exhaustion can progress to heat stroke when the body's temperature regulation fails. The affected individual becomes confused, lethargic and may have a seizure, the skin stops sweating and the body temperature may exceed 106 F (41 C ). This is a life-threatening condition and emergency medical attention is needed immediately.
  
  
• Treatment for heat exhaustion includes recognizing the symptoms, stopping the activity, and moving to a cooler environment. Rehydration with water or a sports drink is the cornerstone of treatment for heat exhaustion. If nausea or vomiting prevents the affected individual from drinking enough water, intravenous fluids may be required.

What is heat exhaustion?

The body cools itself most efficiently by sweating and then the sweat evaporating. Should sweating be unable to meet the cooling demands of the body, heat-related illness can occur. This is a spectrum of conditions with minor symptoms such as prickly heat or heat rash, progressing to heat cramps, then heat exhaustion, and finally to heat stroke, a life-threatening medical condition.

The line between each diagnosis is not sharply drawn. Heat cramps tend to involve involuntary spasm of the large muscles of the body while heat exhaustion has more systemic complaints. These can include profuse sweating, weakness, nausea, vomiting, headaches, and muscle spasms. The affected individual may be a low grade fever. Heat stroke is a life-threatening situation where the body's cooling system fails. The body temperature spirals out of control usually greater than 106F (41C), sweating stops and there are mental status changes like confusion, seizure, or coma.

Heat exhaustion occurs when a person exercises or works in a hot environment and sweating cannot dissipate the heat generated within the body. Often dehydration occurs because the person hasn't replaced the water lost by sweating.