Types of Heat Stroke

There are two types of heat stroke: classic and exertional. Classic heat stroke occurs in individuals who don't sweat normally, either because of a disease or certain medications. Without normal sweating, it's difficult for a person to handle hot, humid weather. The typical victim of classic heat stroke is an older adult who lives without air conditioning and has underlying health problems, such as heart disease or diabetes.

Classic heat stroke can take two or three days to develop, but it is very dangerous. Studies have shown that even a few hours of air conditioning each day can prevent the condition.

Exertional heat stroke, on the other hand, happens quickly--often after only a few hours of exercise. The skin is able to sweat, but the body still overheats because of the combination of hot weather, extra activity, and dehydration. Exertional heat stroke victims are usually young, otherwise healthy people, such as runners and football players.

Exertional heat stroke has long been studied by the military. The U.S. Marines at Parris Island, S.C., for example, have studied heat illness among new recruits. They found that even though soldiers train in the early morning and are required to drink lots of water, as many as 2 percent of them will suffer heat illnesses during the summer months, and about 1 percent in the winter. The risk of exertional heat injuries depends on the heat and humidity, the soldier's fitness level, and whether or not the person is used to hot weather.

Treatment of Heat Stroke

The treatment for both classic and exertional heat stroke is the same: Cool the victim as quickly as possible with whatever means available--for example, wet sheets, a fan, or ice under the armpits. (While the military routinely uses ice to cool heat stroke victims, some studies have shown this can also cause frostbite.) Give the victim liquids, if possible, and get medical attention immediately. Early treatment increases a heat stroke victim's chance of survival.

Who's at Risk?

Certain health conditions increase a person's risk of heat illness. Obesity, sweat gland diseases, diabetes, dehydration (a shortage of body fluids), malnutrition, low blood pressure, and heart disease all make it difficult for the body to regulate heat. In many instances, patients have more than one of these conditions. Older adults, especially, are more likely to have multiple health problems.

Older adults also are more likely to take medicines that impair the body's ability to regulate heat. Some drugs slow sweat production. These include anticholinergics (used to treat Parkinson's disease), antihistamines (for allergies), phenothiazines (tranquilizers), tricyclic antidepressants, and diuretics (for high blood pressure). Some restrict blood flow to the skin, impairing the body's ability to release heat. These include cardiovascular drugs, such as vasoconstrictors and beta blockers.

If you or someone you know lives without air conditioning and takes any of these medicines, ask a doctor or pharmacist about the medicine's possible ill effects in hot weather.

Also at risk are people who use illicit drugs, such as LSD, cocaine and amphetamines. These drugs increase muscle activity and body heat. Excessive alcohol use greatly increases a person's risk for heat illness, too. Alcohol causes the body to excrete water, leading to dehydration.

People who are unable to move about easily--for example, disabled, homeless, and very poor people--are at a higher risk for heat illness because they often cannot afford air conditioning or get to a place that has it. Also, children under 2 can be prone to heat illness because their small bodies cannot regulate body heat as efficiently as older children or adults can. They also may not be able to escape hot places; every summer there are tragic reports of young children who die of heat stroke because they are left in locked automobiles even for short periods.

A victim of heat exhaustion or heat stroke needs immediate medical attention. The important thing is speed: The faster the victim is cooled and rehydrated, the better his or her chance for survival.

Says FDA's Koller, "If people have heat stroke, they really need to get care quickly. This is truly a medical emergency." 

What Causes Heat Stroke?

1. hot weather

2. exercise, especially if you're not physically fit

3. heavy clothing

4. living on upper floors of a building without air-conditioning

5. not drinking enough fluids, leading to dehydration (shortage of body fluids)

6. drinking too much alcohol

7. obesity

8. tiredness

9. older age (65 and over)

10. high outdoor humidity

11. lack of wind

12. medical conditions: alcoholism, neurologic lesions, cardiovascular disease, skin or sweat gland diseases that inhibit the skin's ability to sweat, diabetes, chronic obstructive pulmonary disease, hyperthyroidism, hypokalemia (potassium deficiency), infections that cause fever, and taking certain medications for psychiatric illnesses.

Prevention of Heat Stroke

Take it easy, especially if you are over 65, on any heart or blood medication, or are overweight. Don't make any changes with your medications without your doctor's OK. Don't exert yourself in the summer heat. Exercise in an air-conditioned building if possible.

If you exercise outdoors in the summer, do so in the early morning or late evening hours when it's cooler.

Get used to hot weather slowly. When exercising or doing some other activity outdoors in hot weather, start slowly and gradually increase the time each day. Studies have shown that getting used to the hot weather gradually increases the body's ability to sweat freely without losing salts. It takes about two to four weeks of exercising in the heat before you'll become acclimatized.

Drink lots of water in the summer. If you're exercising, that means about 1 liter (about 1 quart) every hour. If you're just puttering in the garden, take a large jug of water with you, and sip it continuously. Don't rely on thirst to tell you when to drink; people often don't feel thirsty until they're a little dehydrated. Sports drinks and special rehydration fluids are OK, but studies have shown that water alone, combined with a normal amount of dietary salt prevents dehydration in most people. Do not take salt tablets, unless advised to by a doctor, because the excess amount of sodium in them can increase the risk of kidney damage.

Wear a hat with a broad brim to protect you from the sun and loose clothing to allow sweat to evaporate.

Wear sunscreen. A sunburn will inhibit your skin's ability to sweat.

Stay in an air-conditioned environment on hot days. If that's not possible, take cool baths, spray yourself with water frequently, and sit in front of a fan. If you feel faint, call for emergency medical attention.

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