Sunday, January 15, 2006

heat index

The heat index is the combined effect of high temperature and humidity on exposed skin. When temperatures are in the 90s and the humidity is also high, the apparent temperature, or how it feels, is well over 100 degrees. If the heat index is in the 90- to 105-degree range, sunstroke, heat cramps, and heat exhaustion are possible with prolonged exposure or physical activity, especially in the elderly or those in other high-risk groups. The elderly are highly susceptible to a rise in central temperature because of their inability to sweat readily. This is probably the main factor of increased mortality among the elderly during a heat wave. Mortality rates increase with the rise of body temperatures. The average rectal temperature on fatal cases of heat-related deaths has been reported as 106.4 degrees F. When the heat index is over 105 degrees, sunstroke, heat cramps, and heat exhaustion are very likely to occur and heatstroke is possible.
The most common heat-related illness is heat exhaustion. It is caused by the loss of fluid and salts through excessive sweating. Symptoms include fatigue, weakness, dizziness, blurred vision, nausea, muscle cramps, and possible vomiting and fainting.
Treatment for heat exhaustion consists of moving the victim to lie down in the shade, loosening clothing, and elevating the feet eight to 12 inches. Place a cool, wet cloth on the victim's forehead and body and move him or her to an air-cooled room as soon as possible. If the victim is not vomiting, give clear juice or sips of cool water every 15 minutes for one hour. Stop liquids if vomiting occurs. If symptoms become severe or last longer than one hour seek medical help. Heat cramps occur in the group of muscles under stress. The first muscles affected are those in the stomach and legs. Cramps results from a loss of salt. The victim will experience painful cramping, spasms, heavy sweating, and possible convulsions. The affected muscles should be gently massaged with firm hand pressure and liquids should be administered slowly if no vomiting occurs. Heatstroke is the most serious heat-related illness and is a life-threatening emergency. Body temperature may be as high as 106 degrees and the victim may be confused or unconscious and have a rapid pulse rate. A physician should be called immediately.
See also HYPERTHERMIA.
Brocklehurst, J. C. Textbook of Geriatric Medicine and Gerontology, 3rd ed. New York: Churchill Livingstone, 1985.
Coverage. Blue Cross and Blue Shield of Arkansas Publication, 18:1987.

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