The Medical Minute: Be cool and avoid heat-related problems

July 09, 2003

By John Messmer, M.D.
Penn State Milton S. Hershey Medical Center

Summer days are for summer fun -- picnics, sports, swimming, hiking, camping and more. Summer's heat may make the days less tolerable for some, but it also can be downright dangerous. To avoid heat-related injury, there are a few basic safety tips to keep in mind.

Heat stress injury is related to excessive water loss. As most people remember from health class, our bodies eliminate heat primarily through sweating, although we lose some heat directly from the skin into the surrounding air or cool surfaces. We also absorb heat from sunlight on our skin and when we wear darker clothing.

Our brains regulate body temperature by turning on perspiration and dilating blood vessels in our skin to radiate heat away. If sweat cannot evaporate, such as on humid days or when wearing tight clothing, we do not cool off as well. If we fail to stay properly hydrated, the body's ability to perspire and cool itself becomes impaired.

Before heading out for the day's activities, plan to have enough to drink and remember, staying cool is more important than looking cool. It's best to wear light-colored, loosely fitting clothing, which allows air to circulate.

Heavy activities such as sports or yard work require more liquid. Don't wait until you are thirsty to drink -- at that point you're already dehydrated. Drink 1-2 cups of water before heading out and another 2-4 cups of water per hour of activities depending on the heat. You should not need more than four cups per hour even in high heat. You know you're getting enough fluid if you are perspiring and need to urinate every three hours or so. Alcohol and caffeinated beverages increase the risk of heat stress by increasing water loss. Many over the counter medications such as decongestants, weight loss products and ephedra also reduce sweating and increase your risk.

Timing is another important factor in beating the heat. Exercise or do your heavy work early or late in the day when it's cooler. If you are just starting an exercise program, go slowly and rest often for the first two weeks while your body learns to tolerate the heat.

Sports drinks are not necessary for the average person. A regular diet and water are fine for all but the elite athlete or for those in desert environments. Salt tablets are dangerous and not recommended if you're simply trying to stay hydrated in hot weather; normal kidneys retain all the salt you'll need.

Early detection and treatment are key in battling heat-related injury. The first signs of trouble are usually leg and abdominal muscle cramps, often accompanied by weakness. If this happens, get to a cool place -- inside or in shade -- and drink cool liquids. Do not return to the heat until fully recovered.

Heat exhaustion is the second stage. Low fever develops, and the person is dehydrated, weak, and sometimes confused, nauseous and anxious. When this situation occurs, it's vital to get the person to a cool area, preferably indoors in air-conditioning. Keep the skin moist and run a fan to aid evaporation or apply cold towels and offer cold liquids. If recovery does not begin in an hour or if the person is confused or lethargic, call 911.

Heat stroke is the final and potentially fatal stage. About 400 people die annually from heat stress injuries. Body temperature is high, as much as 104, and typically the skin is hot and dry. Although sweating usually stops at this point, the person may have slightly damp skin. The victim is often delirious or even unconscious because they are in shock and require emergency treatment. Call 911 then apply ice packs to the victim's armpits and groins to begin cooling. Offer fluids only if the person is awake. Intravenous fluid is usually needed.

Several special cases bear mentioning. Children have less body surface for their weight than adults so they do not lose heat as effectively and are more susceptible to heat injury at temperatures when healthy adults may be fine. Older people may not feel the heat as well and do not sweat as efficiently as younger people. This combined with medical problems and medications that can affect sweating are the reason over half of all heat related deaths occur in this age group. Alcohol abuse, sunburn, eating disorders, fatigue, obesity, thyroid disease, uncontrolled diabetes and upper respiratory infections all increase the risk of developing a heat related illness.

With simple precautions your summer can be safe and healthy. For detailed information on the heat including a heat index chart, visit http://weather.noaa.gov/weather/hwave.html#HeatIndexChart

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Last Updated March 20, 2009