HEAT STRESS

Sheldon R. Braun, M.D., Wayland N. McKenzie, Ph. D., and Mary Andersen
Occupational Medicine, UMC

Heat rash occurs when the sweat glands of the skin become clogged due to extreme sweating. Usually this looks like red "pimples" on skin that is kept sweaty. White "goosebumps" occur if the sweat glands below the skin are affected. Skin feels prickly. Heat rash disappears when the person is returned to cooler temperatures. Infection can occur if the problem is not corrected.

Heat cramps are caused by loss of salt and electrolytes (magnesium, potassium, calcium) during strenuous exercise in the heat. This is helped by replacing the lost salt and electrolytes, usually taken together with lots of water as well.

Fainting due to heat is caused by the same factors that cause other fainting. People most likely to faint in the heat are those unused to working in it.

Heat exhaustion is caused by excessive sweating. Nausea, giddiness, thirst and headache are common symptoms of this problem. Body temperature may or may not be higher than normal. People vary widely in how much tolerance they have for heat, making it sometimes difficult to foresee this problem. Treatment includes cooling the victim and giving liquids. Take the victim to a cool place, resting in a head-low position. Keep the victim warm enough to avoid shock. Keep at rest. The victim should be watched for further problems.

Heatstroke is a life-threatening situation. Body temperature above 105 degrees F, irritability, staggering, unconsciousness or convulsions, and lack of sweating are the common symptoms. Immediate efforts must be made to cool the victim to 103 degrees F and move to a hospital immediately. Keep the head elevated. Heatstroke occurs when the body's central control mechanisms fail. Because of this general failure, the entire body can be damaged. Especially severe can be the damage to the blood-clotting, liver and kidney functions. A survivor may have permanent damage to these organs, and may also be unable to bear heat as well as in the past.

Healthy people get used to working in a hot environment within 2-3 days. The complete change takes place within 7-10 days. Similarly, after 2-3 days working at a moderate temperature, the adjustment is lost. Adapting to heat is harder for those who are malnourished, elderly, children, overweight, diabetic, or have heart or circulatory problems. However, there is no difference between women and men in heat tolerance, when differences in body size are taken into account. Because it is so hard to predict how a particular person may tolerate heat, the U.S. Department of Health and Human Services has made several recommendations, based on experience and known facts about heat stress.

1. When working in a hot environment, thirst is not a strong enough urge to make a worker to drink enough water to replace up to one quart that may be lost per hour. Therefore, workers in hot environments must be encouraged to drink cool water or non- carbonated, low-sodium beverages about a cupful at a time every 15- 20 minutes. Separate drinking containers help workers keep track of the amount they drink. Still, workers may be a little dehydrated after a work shift. They usually recover overnight.

2. The salt lost from sweat can be replaced by slightly increasing the use of table salt. Those not used to working in hot environments may need to increase their salt intake a little more than others, but this need lasts only 2-3 days. Salt tablets are NOT recommended.

3. Potassium is unlikely to be depleted by anyone eating a healthy diet, due to the abundance of it in meat and fruits. A person taking diuretics, however, may have problems, and may need medical supervision. Depletion of potassium can lead to heatstroke.

4. A normal diet should satisfy the needs of workers in hot environments.

5. Alcohol reduces heat tolerance, and is a common factor in heatstroke. It should not be consumed just before or while working in heat.

6. Many prescription drugs interfere with the body's ability to endure heat. Diuretics and antihistamines are common examples. Ask your doctor's advice if you are taking prescription drugs and working in a hot environment.

Generally, the body must work harder to maintain itself in hot weather. As a result, it is unreasonable to expect to accomplish as much on a very hot day as on a mild weather day. If you have predisposing factors for heat illnesses, be aware of them, and take it easier. Be sure to keep an eye on others working with you, and be alert for headaches, nausea, staggering, dizziness, or other unusual behavior that may mean a heat illness. If you have an infant to care for, remember that they become dehydrated easily. Likewise, children have more difficulty controlling their body temperature than mature adults, and should be encouraged to drink more in hot weather. Children should also be supervised more closely during hot weather, and watched for signs of heat illnesses.