New Statement on Exercise-Associated Hyponatremia Issued

Main Category: Sports Medicine / Fitness
Article Date: 25 Jul 2005 - 0:00 PDT

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Athletes who drink excessive amounts of fluids during prolonged exercise-particularly novice marathon runners-can develop dangerously low sodium levels, called exercise-associated hyponatremia (EAH). Awareness of EAH is increasing, but athletes, coaches, and medical professionals need reliable information on the causes, recognition, prevention, and treatment of this potentially fatal condition.

To address this need, the July/August Clinical Journal of Sport Medicine presents a position statement on current understanding of EAH in endurance athletes. The statement summarizes the conclusions of a panel of medical and scientific experts who met at the 1st International Exercise-Associated Hyponatremia Consensus Development Conference, held in Cape Town, South Africa, in March, 2005.

Exercise-associated hyponatremia happens when the body's sodium level drops too low during prolonged exercise. When mild, EAH may have no symptoms. If sodium levels continue to drop, symptoms such as bloating, "puffiness," nausea and vomiting, and headache develop. At later stages, confusion/disorientation, seizures, and breathing problems may occur, caused by swelling of the brain.

Without appropriate treatment, severe EAH can be rapidly fatal. Appropriate treatment includes the use of highly concentrated (hypertonic) intravenous sodium solutions in small volumes to raise the blood sodium concentration.

The report summarizes known risk factors for EAH, including low body weight and female sex. Novice athletes and those running at a slow pace-especially with race times over four hours-are also at high risk.

However, the main factor leading to EAH is drinking too much fluid during exercise. Hyponatremia may occur whether the athlete drinks water or sodium-containing sport drinks. Excessive fluid dilutes the body's sodium level, interfering with the body's normal regulatory processes.

The key to preventing EAH is to avoid drinking a larger volume of fluid than the body loses in the form of sweat and urine. Formulas are available for estimating hourly sweat loss during exercise-however, a good rule of thumb is to drink only when thirsty. Increasing sodium intake through sport drinks or salt tablets does not appear to reduce the risk of EAH in those who overdrink during exercise.

Planners of marathons and other endurance events can discourage over-consumption of fluid by making sure water stations aren't placed too close together. Information on pre-race weights should be available to medical personnel evaluating collapsed athletes-an increase in body weight is an important clue to EAH. The report includes up-to-date recommendations for doctors and other health professionals involved in evaluating and treating athletes with possible EAH.

Recent years have seen growing concern about the risk of EAH in endurance athletes, particularly with the increased popularity of marathon running for previously sedentary people. The panel members hope their consensus statement will "curtail the growing problem of EAH by disseminating the most current information on the prevalence, nature and treatment of this disorder." The report provides a "snapshot in time" of the current state of knowledge regarding EAH-the position statement will be revised as new information is discovered. Suggested research priorities include the establishment of an international registry to include all new cases of EAH.

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