In hot weather focus on fluids, heat illnesses.

VANCOUVER, B.C. -- As the weather heats up, be prepared to deal with fluid maintenance issues and heat illnesses in young athletes, according to Dr. Michele LaBotz.

"Children are uniquely vulnerable to fluid loss," Dr. LaBotz said at a meeting on pediatric and adolescent sports medicine sponsored by the American Academy of Pediatrics. Fluid depletion not only compromises their athletic performance but also impairs their ability to disperse heat.

Before training, young athletes should replace any fluid lost during the prior workout, she recommended, adding, "this is especially important in our fall athletes, when they are going out a couple of times a day in the heat of August." A good rule of thumb for adolescents is to drink 12-16 ounces of liquids 2-3 hours before play and another 8-12 ounces shortly before play.

During training, high school athletes should drink 8-12 ounces and younger athletes should drink 4-6 ounces every 15-20 minutes. "My suggestion to you is that you make this as concrete to athletes and coaches as possible," Dr. LaBotz, a pediatric sports medicine specialist in private practice in South Portland, Maine, advised. "Have them, for instance, make marks with magic markers on their water bottles, so that everybody knows how much fluid they should be taking at what intervals."

Some athletes will resist drinking fluids because it makes them nauseous. "What you have got to do when you have an athlete like that is to talk about ways to enhance gastric emptying, to get that fluid out of the stomach and further downstream, where it can be absorbed into the circulation," she recommended. For example, they should drink low-carbohydrate drinks (such as sports drinks) instead of water, drinks containing sucrose or glucose instead of fructose, and tepid drinks instead of cold ones.

For athletes generally, water is sufficient for events lasting up to 90 minutes, whereas sports drinks are a better choice for longer events. However, Dr. LaBotz said, "if you offer kids water, they don't drink nearly as much as they would if you offered them fluids that have flavor, color, a small amount of carbs, and a small amount of sodium." "So there's added benefit to those types of fluids in kids."

Fluid type may be especially important in a newly recognized group of young athletes called "salty sweaters," who are prone to heavy sodium loss during exercise. "These are the kids who come off the practice field and they have salt dust on their skin or salt crusting on their uniforms," Dr. LaBotz said. Salty sweaters may be more likely to get muscle cramps and hyponatremia. They should be assessed for adequate sodium intake in their diets, and during events, they may benefit from drinking higher-sodium fluids, such as a liter of sports drink to which a quarter-teaspoon of salt has been added.

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When it comes to rehydrating after training, Dr. LaBotz said the amount of liquid is more important than the type. She noted that a good way to assess net fluid loss during training is to have athletes weigh themselves in their underwear before and again right after practice. These two weights should then be compared and, for every pound lost, athletes should drink about 16 ounces of fluid.

Turning to heat illnesses, Dr. LaBotz said that heat cramps should be treated with passive stretching, icing, and fluids. Athletes can return to play once the cramp has stopped and they have regained full range of motion and strength. But "if they go back into the same event or during the same day, they are at increased risk for recurrence," she said. And although theories abound regarding prevention, none have been proved.

Heat syncope typically occurs when athletes abruptly stop exercising, as at the end of a race; although it can be dramatic, it is not as serious as some other heat illnesses. "The one person who has collapsed out on the course is in far greater need of your expertise than the 20 or 30 people who are having trouble at the finish line," Dr. LaBotz said. Treatment of heat syncope entails increasing venous return, cooling, and fluids, and these athletes generally should not return to play in the same day. "Prevention here is to keep the athletes moving," she said, which can be achieved by putting drinks in a shady area away from the finish line of races and encouraging athletes to continue walking.

The predominant symptom of heat exhaustion is fatigue, but affected athletes also may have nausea and syncope. But Dr. LaBotz said that physicians evaluating athletes with these symptoms also entertain alternative diagnoses, such as hypoglycemia and hyponatremia, the latter which has been increasingly recognized in the setting of endurance and ultraendurance events. In contrast to their counterparts with heat exhaustion, athletes with hyponatremia may not be thirsty, have often had urine output in the past half-hour, have a lower core temperature, and may have CNS symptoms.

Athletes with heat exhaustion are sometimes cooled down by immersion in ice water, but that approach may cause peripheral vasoconstriction, sending hot blood back to the body core, Dr. LaBotz said.

"There's some evidence that kinder, gentler evaporative mist tents may actually be more effective for reducing core temperature," she explained. In terms of return to play, these athletes are at increased risk for further heat injury within the next 48 hours, but thereafter can usually gradually resume training.

Heat stroke, the most serious of the heat illnesses, has claimed the lives of more than 20 high school football players, according to Dr. LaBotz. "You have to remember that although mortality from heat stroke is 10%-25%, the morbidity in terms of significant neurologic sequelae and other bad things is in the 15%-20% range as well," she added. "So, for each player who has died, there has been another one who has been significantly [affected] as well."

The hallmark of heat stroke is CNS symptoms, but again, remain alert for hypoglycemia and hyponatremia, she said. In treating heat stroke, cooling should be done in moderation. "You cool the athlete until you are approaching about 38.5[degrees]C, because once they start to hit mid-38, they will start to shiver and get some thermogenesis, and then you are actually working at cross-purposes," she explained. Hydration is a secondary priority in this context, she said, "so, don't compromise cooling in the idea of trying to get an IV started."

"Heat stroke is truly a season-ending event," Dr. LaBotz said, noting that full tissue recovery takes 2-12 months. Athletes can gradually resume training when they are clinically recovered and their laboratory values return to normal. "Long term, over 90% of these kids who survive heat stroke without major morbidity or mortality actually do come back to full heat tolerance where they were before, but you want to approach it very gingerly," she said.

Preventing heat Stroke entails gradual acclimatization over a week or longer, avoiding high-risk climactic conditions, and maintaining adequate fluid intake, according to Dr. LaBotz. Evidence for any benefit of experimental measures, such as precooling rooms or ice vests, is lacking. "They are all very expensive, they are all kind of gimmicky," she said. "If someone comes to you asking about something, I would certainly educate yourself, but I would look at it with a great deal of skepticism."

Dr. LaBotz reported that she had no disclosures in association with her presentation.

BY SUSAN LONDON

Contributing Writer