Dr. Clif Cleaveland, Commentary

The risk of heat injury accompanies the early arrival this summer of hot, humid weather. Regardless of our levels of fitness, all of us are potentially vulnerable to three heat-related conditions. Dehydration and over-heating are common to each.

Heat cramps. Typically these cramps affect muscles groups most involved in exertion calf or thigh muscles in runners and cyclists, shoulder and arm muscles in gardeners and builders. Thirst and weakness usually accompany cramps. Rest, cooling, gentle massage, and drinking water should relieve cramping.

Heat exhaustion. This represents more severe fluid deficiency and over-heating. Symptoms vary and may include dizziness, nausea, confusion, headache, and profound weakness. Intense thirst is usual. Some victims will have a flushed appearance; others may appear pale.

Two problems compound the recognition of heat exhaustion:

n Athletes are often urged to ignore pain and continue competing,

n Confusion resulting from heat exhaustion may interfere with how the victim perceives and reports his or her symptoms. Treatment involves immediate rest in a cool, shady environment, and careful fluid replacement with water or electrolyte solution such as Gatorade. A victim of heat exhaustion should not resume strenuous exertion until fully evaluated and free of symptoms. Heat exhaustion is a forerunner of heat stroke.

n Heat stroke. The most serious form of heat-injury constitutes a medical emergency. Heat stroke can be fatal without prompt and aggressive treatment. Heat stroke results from a failure of sweating, which in turn leads to a rapid rise in body temperature to 104 degrees and above. Symptoms range from weakness, dizziness, confusion to loss of consciousness and seizures. Rapid, shallow breathing and rapid pulse rate are typical. The skin may be hot and dry or wet from previous sweating. This is a 911 situation.

While awaiting the emergency-response team, victims should be moved immediately to a cool, shady place. Tight garments should be removed, the skin moistened with wet towels or sheets, and the body fanned. If the victim is conscious, he should be given sips of water. Ice should not be applied to the body because this may cause shivering which may increase heat production. Survivors of heat stroke seem prone to recurrent heat injury. They should not resume physical activity until given clearance by a physician.

The risk of heat-injury rises with environmental temperature, relative humidity and level of exertion. Since our bodies depend upon evaporation of sweat for heat loss, high humidity will lessen the effectiveness of this process. In a very dry environment such as the Arizona desert, sweat may evaporate so rapidly that we will not be aware when sweating ceases. Exercise very careful in hot, dry climates.

With careful conditioning, most people can build their tolerance to heat and humidity. Studies of Israeli soldiers showed an ability with training and access to large amounts of fluids to tolerate body temperatures up to 106 without ill effects. Training, however, never entirely removes the risk of serious heat injury.

Water replacement is vital to preventing heat injury. Water should be consumed prior to exertion. A rule-of-thumb is to drink a cup of water every 20 to 30 minutes during exertion. Salt tablets should not be used. Following sustained exertion, such as long-distance running, care must be used in the speed with which water is consumed. Excessive water can drop the sodium level of the blood to the point that seizures and brain injury may result.

One technique involves weighing before and after competition and replacing fluids until pre-competition weight is restored. The use of electrolyte-containing fluids should be left to the recommendations of personal or team trainers.

Infants and children are especially vulnerable to heat injury. They should never be left unattended in an automobile, especially in hot weather.

Obese persons are at increased risk because there fatty tissue promotes heat retention. Elderly persons are vulnerable due to lower levels of fitness, impaired sweating, and use of such medications as diuretics, which reduce body fluid levels, and anti-cholinergics (used in treating asthma, digestive problems, and Parkinson’s disease), which impair sweating. Elderly residents of apartments may not be able to afford air conditioning. Even with minimal exertion, they will be susceptible to heat injury in their over-heated and under-ventilated dwellings. Neighbors or family should monitor them regularly and be prepared to move them to cooler quarters.

All of us should use caution when working in hot environments with poor air circulation such as attics, basements, and garages.

Clip and save the accompanying heat index chart which allows calculations of risks for summertime activities. The heat index combines air temperature and relative humidity. When the heat index is 92 or above, exercise caution for your teammates, your friends, your family and yourself. Provide water and intervals of rest.

When the index exceeds 105, consider postponing scheduled outdoor or high-intensity exertion. Media weather forecasts should regularly provide heat-indices to us in hot weather.

For personal safety and the safety of those for whom you are responsible, read the section on heat injury in a first-aid manual, such as the excellent 2004 edition published by the American College of Emergency Physicians. Each of us must be knowledgeable in preventing and treating heat-related injury.

Contact Clif Cleaveland at cleaveland1000@comcast.net.

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