Did you know that at least 240 people in the United States die of heat-related illness every year? In fact, during the prolonged heat wave of 1980, 1,700 people died as a direct result of those increased temperatures. Unfortunately, heat stroke is also the third ranked cause of death in high school athletes–behind head and neck trauma and cardiac disorders. Additionally, babies and young children (in whom effective heat regulatory mechanisms have not developed), the elderly, people taking certain medications (e.g. antihistamines, diuretics, laxatives, some blood pressure medications, and some antidepressants), and people who are ill (ESPECIALLY those who have diarrhea and/or vomiting) are also at higher risk for heat-related illness. With summer temperatures continuing to soar into the month of August, I thought a few heated remarks would be appropriate this week.
The mildest form of heat-related illness is called heat edema. It’s the swelling people can get in their legs and feet (or dependent body parts) during the hot, muggy, summer months. This problem is caused by transient peripheral vasodilation from the heat and subsequent pooling of the blood during periods of prolonged sitting and standing. One can decrease this tendency simply by getting up and walking with regularity, wearing light weight compression stockings or socks, and of course, by elevating the legs when seated.
Heat cramps are a more serious form of heat-related illness. They are painful muscle spasms that may occur in the calves, abdomen and thighs. They are due to a loss of water and electrolytes and can occur in people who are in good shape but who have simply overexerted themselves. Use of diuretics and lack of acclimatization (the adjustments one’s body makes over time to chronic exposures to higher heat and humidity) are certainly predisposing factors. Treatment for heat cramps includes rest in the shade, increased proper fluid intake (avoiding caffeine and alcohol. . .which BOTH act as diuretics), gentle stretch and massage to the area cramping, and application of ice to the area to break the muscle cramp. Water and “sports drinks” are generally the best forms of rehydration. If you’re as old as I am, you remember the coaches recommending use of salt tablets too. . .but they aren’t a recommended form of treatment anymore.
Heat exhaustion is due to dehydration. Poorly conditioned people are more susceptible to this form of heat illness. Usually, the person has sweated excessively in a hot, humid environment with resultant depletion of body fluids. Remember, during heavy exertion, one can lose up to 3 quarts of sweat! Core body temperatures may rise above 100.4F but remain below 105Fin this form of heat illness. Symptoms may include profuse sweating, headache, pale, clammy skin, extreme thirst and lightheadedness. Treatment again involves moving to a cool place, cool compresses, and oral rehydration (preferable over intravenous rehydration if the person is coherent and not nauseated or vomiting) of approximately 2 pints/hr. for several hours, and elevation of the legs. The person should recover rapidly and feel better in two to three hours. If this improvement is not seen, seek a medical opinion.
Heat stroke is the worst heat related injury; it is a serious life threatening condition. The core body temperature rises to at least 104F and acute mental status changes occur. In this setting, the body’s thermoregulatory mechanism breaks down–with heat production exceeding the body’s ability to dissipate the heat. Signs of this form of heat illness include hot, flushed skin, minimal sweating, vomiting, and mental status changes that can range from disorientation and hallucinations, to seizures and even coma. This is a true medical emergency with a mortality rate up to 10%, and can cause permanent damage to kidneys, heart, and liver if not managed swiftly and properly. If you find someone in this condition, call an ambulance, and try fanning and cool compresses while awaiting emergency transport to a hospital. Rapid cooling of the person’s body temperature to at least 101.8F or below is essential to avoid permanent organ damage.
The key in all of the above scenarios is prevention. A person should gradually acclimatize to summer heat and humidity over 7–10 days rather than all at once. Proper fluid replacement is very important. . .remembering that caffeine and alcohol have diuretic effects. . .and remembering too that THIRST should not be relied upon as the indication for fluid replacement; we are ALREADY 5% or more dehydrated when we’re thirsty. Wear light colored, lightweight, loose-fitting, cotton clothing to help keep your body cool; avoid direct sunlight when possible, and try to schedule heavy outdoor work in early mornings or late evenings. Remember, sweating is our body’s mechanism for cooling us off–as we perspire, our sweat evaporates into the air and this cools us down. However, when the humidity reaches 65%, sweat evaporation is impaired, and at 75% humidity, sweat evaporation essentially ceases.
Pre-hydrate before exercise (including heavy yard work) with 16 oz. of fluid, and then try to consume 8 oz. every 20 minutes during continuous exercise, with the goals of: 1) not experiencing thirst and 2) voiding light yellow urine at least four times per day. Dehydration is generally not a problem for exertion lasting less than 20 to 60 minutes. So, enjoy yourself in the warmth of summer, but do prepare wisely. Sweating it the RIGHT WAY, will protect you from harmful dehydration and overheating.
Stephen L. Hines, M.D.
August 2001
