Arduous Exercise: Salt-Sapping Danger

A new set of guidelines for treating exercise-associated hyponatremia calls attention to the potentially dangerous complications of the condition.

Most people know that it’s prudent to replace electrolytes when exercising. Still, many may be unaware of how serious electrolyte imbalance can become. Few know that heavy exercise can lead to exercise-associated hyponatremia (EAH) during or up to 24 hours after arduous physical activity such as hiking, biking, or military training. When serum sodium concentrations fall below 135 mEq/L, patients are at risk for adverse outcomes.

A set of evidence-based guidelines for treating EAH written by an expert panel convened by the Wilderness Medical Society and published in the September 2013 issue of Wilderness & Environmental Medicine discusses the critical nature of rapid recognition of and appropriate treatment for this electrolyte imbalance. Failure to recognize and treat instances of EAH may lead to serious complications including death.

The Wilderness Medical Society panel used a consensus approach in developing the guidelines. After identifying excessive fluid intake and impaired urinary water excretion as the 2 major causes of EAH, the panel recommended that athletes should avoid overdrinking and excessive sodium supplementation during exercise. They also recommend monitoring body weight closely during periods of high-intensity training to prevent over-hydration. If hyponatremia is suspected, the panel recommends taking serious precautions before treatment with IV fluids, which can worsen hyponatremia if carried out inappropriately, and avoiding hypotonic fluids. Overall, the panel pointed out an ongoing need for education to ensure that participants in intense exercise activity understand the risk of over-hydration.

In a follow-up letter to the editor, Grant S. Lipman, MD, of the Stanford University School of Medicine expresses concern that the guidelines do not provide ample evidence to support several of the panel’s recommendations. Specifically, he points out that the panel’s assertion that unstable blood pressure is an indication for IV fluids in dehydrated athletes implies an inappropriately high threshold and argues that early intervention with isotonic fluids is clinically indicated. Dr. Lipman also suggests that some of the panel’s evidence may be insufficient to support their recommendations. His letter—a comprehensive review of the original paper—points out that EAH patients may experience a transient decrease in serum sodium with both isotonic and hypertonic IV therapy. In concluding his letter, Dr. Lipman argues that hypertonic saline should be preferred if the patient has a risk of neurologic impairment, a fact that was not highlighted in the panel’s published findings.

The guideline authors, in a reply to Dr. Lipman, provide additional information that clarifies the evidence and underscores an important issue: Many clinicians still do not understand EAH and continue to debate its appropriate treatment. The Wilderness Medical Society panelists note that Dr. Lipman concurs with their recommendations for the most part and emphasize that they stand by their recommendations. The entire series makes for interesting and educational reading.

Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a freelance writer from Virginia.