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Heat Exhaustion and Heat Stroke

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Heat exhaustion and heat stroke definition and overview

Heat exhaustion: This condition often occurs when people are exposed to high temperatures especially when combined with strenuous physical activities and humidity. Body fluids are lost through sweating, causing dehydration and overheating of the body. The person's temperature may be elevated, but not above 104 F (40 C).

Heat stroke: Heat stroke, also referred to as heatstroke or sun stroke, is a life-threatening medical condition. The body's cooling system, which is controlled by the brain, stops working and the internal body temperature rises to the point at which brain damage or damage to other internal organs may result (temperature may reach 105 F or greater [40.5 C or greater]).

The National Oceanic and Atmospheric Administration (NOAA) reported that 155 people died in 2012 as a result of extreme heat, down from 206 fatalities in 2011. An average of 119 people die each year due to extreme heat conditions in the U.S. Avoid heat exhaustion by not engaging in strenuous activity in hot, humid environments; and stay hydrated as prevention is the key.

What are the causes of heat exhaustion and heat stroke?

Heat exhaustion is typically caused when people who are not well adjusted to heat exercise or work in a hot, humid environment.

  • At high temperatures, the body cools itself largely through evaporation of sweat.
  • When it is very humid, this mechanism does not work properly.
  • If the body generates additional heat through exercise or strenuous work, the situation is worsened.
  • The body loses a combination of fluids and salts (electrolytes).
  • When this is accompanied by an inadequate replacement of fluids, disturbances in the circulation may result that are similar to a form of shock.

Heat stroke may develop rapidly.

  • Medical conditions or medications that impair the body's ability to sweat may predispose people to this problem.
  • Heat stroke happens in the following two ways:
    • The classic form occurs in people whose cooling mechanisms are impaired.
    • The exertion form occurs in previously healthy people who are undergoing strenuous activity in a hot environment.
  • Infants, children under the age of 4, the overweight, and the elderly are more likely to have this problem, as are people taking antihistamines, diuretics (water pills), and certain types of medication for high blood pressure, heart disease, or depression.
Medically Reviewed by a Doctor on 5/28/2013


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