How to beat the heat

Walking on the beach, biking in the blazing sun, resting in a city apartment on a sweltering summer afternoon – all these activities can put you at risk of heat-related health problems. But you can avoid trouble by watching out for the signs of dehydration and taking some commonsense steps to avoid it.

he Human Thermostat

T The body generates its own heat, which accounts for the average, or "core" temperature of 98.6°F. Based on external cues, the brain tries to keep the core at about that temperature, though a particular person’s internal temperature can range throughout the day from 97°F to 100°F.

When the mercury rises, the body’s main defense is perspiration. Sweat glands in the skin pump fluids to the surface, where they evaporate and carry the heat away. Obviously, your internal air-conditioning system needs a ready supply of fluids to keep the flow going. And that’s why the answer to avoiding most heat-related health problems is quite simple: "Hydration, hydration, hydration," says Andy Jagoda, MD, professor of Emergency Medicine, Mount Sinai School of Medicine, in New York.

Effects Of Dehydration

Hydration refers to your reserve of body fluids – inside cells, between cells, and in blood plasma. When the reserves dip too low, you become dehydrated. "If your body gets dehydrated, it loses the ability to sweat," Dr. Jagoda explains. "If you lose the ability to sweat, you lose the ability to cool yourself." The effects of overheating and dehydration depend on how low your fluids dip and how hot your core temperature becomes. The two most serious conditions are heat exhaustion and heatstroke.

Heat exhaustion occurs when your body fluids are 5 to 10 percent below normal. "It’s a generalized weakened state brought on by dehydration," Dr. Jagoda says. As heat exhaustion comes on, you may feel weak, dizzy, lightheaded, achy, or nauseated. Many people who think they have "summer colds" or flu are actually suffering from heat exhaustion.

As fluid levels fall, you may become flushed and red-faced as blood vessels dilate to shunt warm blood toward the skin to be cooled. As the situation worsens, the vessels might subsequently constrict to force blood back toward the brain and other organs. As a result, you may turn pale and cool to the touch.

Heat exhaustion is unpleasant but not life-threatening. But if you don’t head things off at this point, you could progress to heatstroke.

Heatstroke occurs when your core temperature rises so much that the body begins to lose the ability to control it. ("Sunstroke" is just heatstroke caused by exposure to the sun). As heatstroke comes on, you may stop sweating altogether, making the skin warm and dry to the touch.

Due to the drop in blood volume and pressure, blood flow to vital organs is reduced. "You’re not getting blood to your brain, your kidneys, your liver, your heart, and you actually sustain damage as a result of that," Dr. Jagoda explains.

There is no specific core temperature that pushes you into heatstroke, but "once you get above 105°F, you’re getting to a dangerous level," Dr. Jagoda says. As the heat builds up, you become more and more incapacitated. You may experience racing pulse, nausea, cramps in the stomach, and confusion. Slurred speech and convulsions may follow. Heatstroke is life-threatening; people can and do die of it.

Know The Danger Signs

Symptoms of dehydration and overheating include the following:

• Severe thirst and dry tongue • Headache

• Feeling of impatience or irritability

• Rapid yet weak pulse

• Lightheadedness • Nausea and vomiting

• Heavy sweating • Diarrhea

• Pale, cold, clammy skin • Cramps in the stomach, legs, or arms

• Dizziness, fainting

Who’s At Risk

Everyone is at risk of heat-related illness if they allow dehydration to occur. But some people are more vulnerable than others. When heat wave strikes, it is often the oldest among us who gets into trouble. Some people may be unable to move around freely due to arthritis pain or prior hip injury. Older adults are more susceptible to low blood pressure in hot weather because of the general age-related decline in the ability to regulate blood pressure. The sensation of thirst is also impaired with aging, and the body’s water reserves decrease.

Medications also interfere with the body’s cooling systems. For example, older adults on diuretic medications for hypertension and heart failure are susceptible to dehydration because these medications eliminate water from the body. People on beta-blockers may not be able to maintain blood pressure in the heat due to the heart’s weakened pumping ability. >

Top Off The Tank

To keep your fluids "topped off," Dr. Jagoda recommends that you drink until your thirst is satisfied – and then drink more. "People tend to underestimate their volume needs," he says. "You should always drink 20 percent more than you think you need."

But how much is enough? This depends on the temperature, your level of activity, and your body size. But there is a simple way to monitor your fluid intake: Look at the color of your urine. If it’s coming out dark yellow, you’re dehydrated. It should be clear. You can also help keep your fluids topped off by continuously sipping water throughout the day, instead of drinking only when you are thirsty.

Other than drinking lots of fluids, rely on common sense to prevent overheating. That means wearing light-colored clothing with breathable fibers, such as cotton; wearing a hat in full sun; carrying a water bottle when walking or hiking in the heat; exercising early in the morning, when it is cooler; and avoiding heavy consumption of beverages with alcohol or caffeine, which can interfere with your body’s cooling system.

What You Can Do

• If you begin to feel the signs of overheating, get out of the sun, drink cool fluids, spray or splash yourself with water if you can, and rest until you feel better. Don’t tough it out.

• If you are attending to a companion who has become ill, lay the victim down, loosen any type clothing, and elevate the legs.

• Give the victim small amounts of cool liquids. Be prepared for vomiting.

• If the symptoms worsen, get to an emergency room fast. Heatstroke is life-threatening.

• Lower the victim’s body temperature as quickly as possible. One way is to wet the victim’s exposed skin and fan vigorously. If possible, immerse the person in cool water – such as in a bathtub – although don’t leave the person unattended.

The take-home message is this: Whether you’re out in the summer sun for a game of tennis or beach volleyball, remember that the risk of heat-related illness rises along with the temperature and humidity. Commonsense precautions and an awareness of symptoms can help prevent – or get prompt treatment for – heat exhaustion and heatstroke.