Heatstroke is a life-threatening medical emergency that requires immediate treatment. A review published in June 2005 in "American Family Physician" found that up to 10 percent of people who develop heatstroke die. The same review notes that the condition is responsible for 240 or more deaths in the U.S. each year. Heatstroke disrupts the central nervous system, potentially causing seizures and coma. Muscle, kidney, liver and heart damage may also occur.
Heatstroke develops when your body is unable to rid itself of excess heat and your core temperature rises above 104 F. People who perform strenuous work or exercise in high temperatures are at risk of exertional heatstroke, particularly if they become dehydrated.
The condition also strikes people -- typically children, the elderly and the chronically ill -- with preexisting health problems that make it difficult to control body temperature in hot weather. Alcohol, cocaine, amphetamines and prescription medications, including high blood pressure medications and diuretics, can increase your risk of heatstroke.
When your internal body temperature rises above 104 F, cellular functions break down and energy production is disrupted. High temperatures change the structure of proteins, a process called denaturing. This causes the proteins to function abnormally or cease functioning completely. Cells become leaky, allowing potassium to escape and disrupting the body's acid-base balance. As cells stop functioning and die, organs begin to fail, ultimately affecting nearly every organ system in the body.
The brain is particularly vulnerable to heat damage. Heatstroke commonly causes ataxia, which is the loss of muscle coordination. Deliriousness, seizures and coma are other manifestations of heatstroke. According to the review in "American Family Physician," heatstroke causes permanent central nervous system damage in about 20 percent of patients. In severe cases, central nervous system disruption can be fatal.
High body temperature also causes rhabdomyolosis, which is severe muscle tissue damage. As muscle tissue breaks down, a chemical called myoglobin is released into the bloodstream. High levels of myoglobin can cause kidney injury or failure.
Heatstroke also damages the liver. The heart is also vulnerable. Excessive potassium can cause heart rhythm abnormalities and high body temperature may directly damage the heart muscle. In severe cases, the heart may stop beating.
Treatment and Prevention
Heatstroke requires immediate medical attention. The cornerstone of treatment is cooling the body through external methods, such as ice baths or spraying the body with cool water. Medications and other treatments are used to halt or alleviate heatstroke complications.
To prevent exertional heatstroke, avoid exercising too long or too hard in hot or humid conditions. Wear loose clothing and drink enough fluids to avoid dehydration. The American College of Sports Medicine suggests that athletes gradually acclimatize to exercising in hot weather over a period of 10 to 14 days. The group also recommends athletes avoid exercising in hot weather when they are ill.