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Definition

Heat exhaustion is when the body overheats when you are too active in hot temperatures. Heat stroke is a more severe illness that can be life-threatening.

Causes

Both heat exhaustion and heat stroke happen under the following conditions:

  • Very hot environment
  • Heavy activity
  • Too little fluid and salt intake
Risk Factors

Young children and older adults are at increased risk for heat exhaustion.

Factors that may increase your risk of heat exhaustion and heat stroke include:

  • Participating in a job or activity that involves long periods of outdoor activity in hot weather
  • Taking drugs that interfere with the way your body handles hot weather, including:
    • Phenothiazines
    • Anticholinergics
    • Antihistamines
    • Beta-blockers
    • Benzodiazepines
    • Amphetamines
    • Neuroleptics
    • Tricyclic antidepressants
    • Cocaine
    • Alcohol
Symptoms

Symptoms of heat exhaustion may include:

  • Temperature over 37.8°C (about 100°F)
  • Fast pulse
  • Moist skin, sweating
  • Muscle cramps and tenderness
  • Nausea, vomiting
  • Lightheadedness
  • Confusion
  • Headaches

Symptoms of heat stroke may include:

  • Temperature over 40.5° C (about 105° F)
  • Weakness, lightheadedness
  • Blurred vision
  • Confusion, delirium, unconsciousness (can progress to coma)
  • Seizures
  • No sweating
  • Pale, dry skin
  • Fast breathing, fast heartbeat
Diagnosis

You will be asked about your symptoms and medical history. A physical exam will be done.

Your bodily fluids may be tested. This can be done with blood tests.

Your heart activity may be measured. This can be done with an electrocardiogram (ECG, EKG).

ECG / EKG Wave

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Copyright © Nucleus Medical Media, Inc.

Treatment
Heat Exhaustion

Treatment for heat exhaustion includes:

  • Moving the person to a cool, shady area
  • Giving adequate fluids—it is best to give fluids that contain both salt and sugar. If the person isn't able to drink, it may be necessary to give fluids through by IV.
  • Encouraging the person to rest
Heat Stroke

Treatment for heat stroke includes:

  • Removing clothing
  • Moving the person to a cool, shady area
  • Actively cooling the person—the most effective way is called evaporative cooling. In evaporative cooling, the person is sponged with cool water or sprayed with cool mist, and fans are used to blow air onto the person.
  • Giving IV fluids
  • Giving medications—these may be necessary if the person is having seizures or uncontrollable shivering
  • Careful monitoring—People who have undergone heat stroke need regular and careful monitoring of body temperature, heart rate, blood pressure, and breathing rate. Blood tests will be repeated at regular intervals to monitor how the body's organs are responding to the shock of heat stroke.
Prevention

To help prevent heat exhaustion and heat stroke:

  • Avoid prolonged exposure to high temperatures.
  • If you have to work or exercise under hot conditions, drink lots of fluids (preferably sports drinks, which contain both salt and sugar), and take frequent breaks in the shade.
  • If you have a risk factor for heat exhaustion or heat stroke, be careful participating in activities in hot weather. Take regular rests and drink lots of fluids.
  • During heat waves, try to spend time indoors with air conditioning or go to an air conditioned shelter. This is especially important for older adults.

RESOURCES:

American Red Cross
http://www.redcross.org

Family Doctor—American Academy of Family Physicians
http://www.familydoctor.org

CANADIAN RESOURCES

Canadian Red Cross
http://www.redcross.ca

Health Canada
http://www.hc-sc.gc.ca

References:

Heat exhaustion. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated August 22, 2013. Accessed September 30, 2014.

Heat exhaustion and heatstroke. Family Doctor—American Academy of Family Physicians website. Available at: http://familydoctor.org/familydoctor/en/prevention-wellness/staying-healthy/first-aid/heat-exhaustion-an-heatstroke.html. Updated December 2010. Accessed September 30, 2014.

Heatstroke. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated August 9, 2013. Accessed September 30, 2014.



Last reviewed August 2014 by Marcin Chwistek, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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