Here Comes the Sun
By Debbie Gilbert
JUNE 21, 1999: The first heat wave of the summer hit Memphis in early June, prompting TV news anchors to begin chanting their hot-weather mantras: Drink plenty of water. Take frequent rest breaks. Blah blah blah. We've heard the warnings so often that we tune them out -- just like we don't listen when flight attendants try to "take a moment to point out the safety features of this aircraft."
Wrong, according to Dr. Stephen Winbery, an emergency-room physician at The Med. He estimates that on a typical summer day, 10 percent of the patients seeking treatment in the ER have heat-related problems. But the root cause of their suffering is poor judgment; in most cases, their illness could have been prevented by using common sense.
"Too often we see people trying to lose weight by sweating, and they'll be wearing these plastic or rubber suits," says Winbery. "And believe it or not, [some] people take saunas in the summer."
Most of us overestimate our ability to withstand the heat. We think it's a question of mind over matter -- that if we just use our willpower and tough it out, we'll be okay. But we are prisoners of our own physiology; we survive only because our bodies have a built-in cooling system. If that temperature-regulating mechanism goes haywire, we're in big trouble -- and there are a lot of things that can make it malfunction.
When that cooling system breaks down completely, death can come in as little as 30 minutes. Everything that your body does -- from the beating of your heart to the blinking of your eyes -- generates heat. If the system didn't have a way to dissipate heat, basal metabolism alone (the energy you burn just sitting still) would cause your temperature to increase by 1.5 degrees Farenheit every hour. Combine that with exercise and environmental factors, and in no time you'd be past the point of no return: 106 degrees or above, where irreversible brain damage and death occur.
Fortunately, there's a wonderful phenomenon called sweat, which is responsible for 90 percent of the body's cooling ability. In hot weather, your goal should be to encourage sweating and to avoid anything that inhibits it. That means drinking water constantly, even if you don't feel thirsty. And it means staying away from diuretics -- including alcohol -- which send water to your bladder instead of to the surface of your skin where it can help you.
If you're feeling overheated, the culprit could be in your medicine cabinet. Many drugs decrease sweat production, including anticholinergics (such as medicines that treat Parkinson's disease), antihistamines, tranquilizers, and tricyclic antidepressants. Other drugs restrict blood flow to the skin, preventing the body from releasing heat; these include vasoconstrictors (e.g., for migraine) and beta blockers (for high blood pressure). And illegal drugs like LSD, cocaine, and amphetamines can rev up metabolism, raising body temperature to dangerous levels.
Even if you're sweating freely, it may not be enough if the atmosphere doesn't cooperate. When the humidity level is high, the air is already saturated with water, so moisture doesn't evaporate from your skin. That's why an 80-degree day with 100 percent humidity feels as hot as a 100-degree day with no humidity.
Your body tries to compensate for the heat by diverting blood to the surface of your skin -- which means that eventually there's not enough blood supplying the brain and internal organs. That's when you start to feel weak and nauseated (heat exhaustion) or even hallucinate and go into shock (heatstroke). "Classic" heatstroke is what oftens happens to elderly individuals who are cooped up inside their homes with no air conditioning; it's fatal in 50 percent of cases. But exertional heatstroke can happen to anyone -- yes, even you. You're more at risk if you're obese, diabetic, malnourished, dehydrated, or have heart disease.
How does heat kill? By damaging the kidneys, liver, and brain, and destroying the body's blood-clotting mechanism. People often use cooking analogies to describe how heat affects them, as in, "I feel like I'm baking out here." But Winbery says "melting" is a better word choice.
"When you thaw out ice cream and refreeze it, it's not ice cream anymore. It has the same molecules, but its texture has been lost," he explains. "That's what happens to the proteins in your body [at high internal temperatures]."
Winbery's advice: Once you're feeling symptoms of heat exhaustion, you need to take it easy for the rest of the day. "I see people all the time who get out of the heat for about an hour, then think they're over it and get back to that environment [where they became ill]. Those folks can progress pretty rapidly [to heatstroke]. Once you've experienced heat exposure, it can take at least overnight to recover."
So pay attention to the health warnings -- there's a reason for them. Drink water. Don't overexert yourself. Stop if you feel sick.
And for sweltering Memphians, the best advice of all may be: Call your travel agent and book a flight to Canada; the exchange rate is really good right now.
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