Sunday, August 06, 2006

How Heat Kills

I descend from people who sweat easily. My mom sweats easily. I sweat easily. My son and daughter sweat easily. I suppose some of my grandchildren will sweat easily too. Thailand's hot and humid weather does not help us at all. After an hour of exercise, I sometimes sweat up to one hour afterward, even in an air-conditioned room.

Today, I found an interesting article about the mechanism of how heat kills people and how, if I don't sweat enough, I can die*:

On a very hot, sticky day, you may not be able to radiate any heat from the surface of your skin, and your sweat won't evaporate fast enough to keep you cool. (You'll have an even bigger problem if you're dehydrated.) The heart responds by pumping more blood away from the internal organs. This deprives the intestines of oxygen, which damages their linings and makes them more permeable to endotoxins. (The strain on the heart can also lead to arrhythmia or cardiac arrest.) At the same time, an overheated core causes an inflammatory response throughout the body. The combination of the inflammatory response and the endotoxins in the bloodstream can suppress the body's natural mechanism for cooling down.

Once your core gets above about 104 degrees, you're in serious danger. High internal temperatures lead to increased pressure in your skull and decreased blood flow to your brain. (Doctors diagnose "heatstroke" when the heat starts to affect your central nervous system.) Damaged tissue may also enter your bloodstream and lead to kidney failure. Very high internal temperatures—like 120 degrees—can destroy the cells in your body through direct heat damage.

Of course, there is an antidote: How to Cool Yourself Without Air Conditioning.

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*To convert F degrees fahrenheit** to C degrees celsius***, use the relationship (F-32)/9 = C/5. Therefore, 104 degrees fahrenheit is 40 degrees celsius while 120 degrees fahrenheit = 48.9 degrees celsius.

**Degree fahrenheit is named after Daniel Gabriel Fahrenheit, a German physicist who invented the mercury thermometer and developed the scale of temperature that bears his name (1686-1736).

***Degree celsius is named after Anders Celsius, a Swedish astronomer who devised the centigrade thermometer (1701-1744).

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