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).

Treatment

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.

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

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

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.