May 12, 2000 -- On this weekend of Mother's Day and heat waves, Russell Dreyer, MD, has an appropriate message: "Thank God for mothers. They do a lot of diagnosis that never gets recognized, and they do a lot of caretaking and recognition of the condition early on that they fix."
The condition Dreyer is referring to is heat exhaustion, and if the forecasts hold this weekend, many children and adults around the nation may feel some of the symptoms of heat sickness as they work or play in the sunshine.
Dreyer, who is co-director of several emergency rooms in the metro Atlanta area, has seen the symptoms many times. He and other experts say some rules of thumb for avoiding heat illness are: avoid being outside during the hottest part of the day; wear light, loose clothing; and, most important, drink plenty of fluids.
The consequences of getting overheated, Dreyer says, can be serious.
"People start off with thirst, and generally they ignore that," he tells WebMD. "But if you don't pay attention to thirst, then you start becoming a little bit weak as your electrolytes get out of balance, and your dehydration gets worse.
"One of the earlier signs would be muscle cramping, and then you progress to something like an altered mental status, you're not thinking as clearly, and that's getting to the danger point," he explains.
After that, your body's temperature-setting mechanism goes out and you quit sweating, and that means the body doesn't have any way to control the heat, Dreyer says. "It's an absolute emergency because all your tissues start to break down because your temperature goes up," says Dreyer, who adds that he has seen patients with body temperatures as high as 110 degrees.
Anyone who is outdoors -- or, for that matter, indoors without air conditioning -- is at risk of heat sickness, Dreyer says, but some categories of people are at greater risk.
They include the elderly, the young, and anyone who has mental impairments, as they may not be able to recognize when they are in danger. Alcoholics and people on medications that affect their thinking can be in danger, as can anyone in a debilitated state, like a stroke victim.
Dreyer says he sees a "fair number" of people with heat exhaustion who have been out on the baseball field or construction site for too long. But many victims of heat illness, particularly children, never get to the emergency room. "Quite a number of them are never diagnosed; they just go home feeling a little lousy, and they're real hot," he tells WebMD.
"If they're healthy, usually that's a self-limited disease. They get too tired to play, or they go home, or their mothers notice their faces are real red and they're sweating profusely and they take them home," Dreyer says.
Of course, there is a way around all this: water. It's important for everyone, but it takes on added importance for people working outside, whether they are paving roads or exercising.
David Martin has completed 29 marathons, and he's never, as he calls it, "bonked." But plenty of athletes, experienced or not, fade as they work out in temperatures high enough to make a kettle whistle.
Martin says he owes his successful track record to proper preparation -- especially the proper regulation of fluids. Of course, he also has an advantage over most people in that he has a PhD in physiology and is the chairman of sport science for U.S.A. Track and Field.
"I've always been sly enough and followed my principles of physiology," Martin tells WebMD. Those principles are quite simple, he says: If you're an athlete -- whether you're training for the Olympics or just jogging around the block -- "you really want to live a healthy lifestyle, which means not being thirsty and not being hungry."
Although avoiding the hottest parts of the day is best, that's not always possible. So week-long laborers and weekend warriors alike should make sure they never let themselves get thirsty.
"As soon as they have reached a point of thirst, they actually are dehydrated," Martin tells WebMD. "We say you never pass up a drinking fountain, or carry a small bottle and take sips to make sure your fluid levels are up."
The most dangerous condition for exercisers, Martin says, is humid heat. The evaporation of sweat helps to cool the body, but humidity limits the amount of evaporation, he explains.
If you're exercising, that can be critical. Most of the perspiration we produce comes from blood plasma. So excessive perspiration can decrease the volume of blood just when it is needed in the muscles that are working.
In times of heat stress, the body also sends blood to the skin surface to cool the body by radiant heat loss. "But at the same time, you want that same amount of blood to go into your working muscles, so that you can provide nutrition and oxygen for metabolism. And if you have to share a smaller and smaller amount of blood, because of sweating, with these two major tissue masses -- the skin for cooling, but the muscles for working -- something has to give," Martin says.
This could hurt the athlete's performance, or it could lead to heat exhaustion or even heat stress. A person racing in the heat, for instance, can lose a liter to a liter and a half of sweat an hour. But the body can absorb about a liter of water an hour, so adaptations are necessary for those who must compete or work in the heat.
"One of the training adaptations is that training in the heat stimulates storage of more fluid, so your fluid volume increases so you have more available," Martin tells WebMD. But that kind of training needs to progress gradually. Martin says it usually takes about a month for an exerciser to "acclimatize" to the heat.
Most sports drinks do work, according to Martin, as long as they aren't too high in carbohydrates, "because this can actually lessen fluid absorption." He says exercisers should stay away from beverages that contain alcohol or caffeine because they can be dehydrating.
So if preventing and rectifying heat exhaustion is as simple as drinking enough fluids, why do overheated people keep showing up in emergency rooms?
Maintaining healthy hydration (and the all-important healthy diet) doesn't always go according to plan, Martin says. "It sounds so simple; it's amazing that it's so difficult to do."
- Heat exhaustion begins with thirst and progresses to muscle cramping and an altered mental state; then the body stops sweating, temperature goes up, and tissue starts breaking down.
- The best way to prevent heat exhaustion is to drink water; once thirst sets in, you are already dehydrated.
- In healthy people, heat exhaustion may not be a serious problem, but it can be dangerous for the young and the elderly.