Case Study: Symptomatic Exercise-Associated Hyponatremia in an Endurance Runner Despite Sodium Supplementation

Abstract

Symptomatic exercise-associated hyponatremia (EAH) is known to be a potential complication from overhydration during exercise, but there remains a general belief that sodium supplementation will prevent EAH. We present a case in which a runner with a prior history of EAH consulted a sports nutritionist who advised him to consume considerable supplemental sodium, which did not prevent him from developing symptomatic EAH during a subsequent long run. Emergency medical services were requested for this runner shortly after he finished a 17-hr, 72-km run and hike in Grand Canyon National Park during which he reported having consumed 9.2-10.6 L of water and >6,500 mg of sodium. First responders determined his serum sodium concentration with point-of-care testing was 122 mEq/L. His hyponatremia was documented to have improved from field treatment with an oral hypertonic solution of 800 mg of sodium in 200 ml of water, and it improved further after significant aquaresis despite in-hospital treatment with isotonic fluids (lactated Ringer's). He was discharged about 5 hr after admission in good condition. This case demonstrates that while oral sodium supplementation does not necessarily prevent symptomatic EAH associated with overhydration, early recognition and field management with oral hypertonic saline in combination with fluid restriction can be effective treatment for mild EAH. There continues to be a lack of universal understanding of the underlying pathophysiology and appropriate hospital management of EAH.

Exercise-Associated Hyponatremia: 2017 Update

“…Hoffman et al found that hyponatremia, as well as exercise-associated muscle cramping, dehydration, and nausea or vomiting, was unrelated to total sodium intake in participants of a 161 km ultramarathon (67, 68). This was confirmed in a case study which demonstrated that oral sodium supplementation does not necessarily prevent symptomatic EAH associated with overhydration (69). On the other hand, another study demonstrated that longer term (10 days) reduction in dietary sodium intake can cause reductions in plasma sodium concentration before as well as during exercise when fluid losses and ingestion are large and may consequently have adverse effects on physiological and functioning during such exercise (70).…”

“…A case report has been recently published in which a runner with a prior history of EAH consulted a sports nutritionist who advised him to consume considerable amounts of supplemental sodium, which did not prevent him from developing symptomatic EAH during a subsequent long run (69). A study involving 156 participants of a 161 km race found a weakly positive relationship between sodium supplementation and post-race serum sodium concentrations; the authors concluded that sodium supplementation had a minimal contribution on the prevention of hyponatremia (68).…”

Is Sodium Supplementation Necessary to Avoid Dehydration During Prolonged Exercise in the Heat?

“…Excessive sodium intake during exercise may also increase the risk for development of pulmonary edema (23) and has even been seen associated with exercise-associated hyponatremia (13,18), effects possibly resulting from overhydration mediated by gastrointestinal or hepatic portal osmoreceptors that provide an early stimulus of thirst without elevation in blood osmolality (20,34,35). Therefore, sodium use during exercise should be with regard for some potential risks.…”

Description of Three Female 24-h Ultra-Endurance Race Winners in Various Weather Conditions and Disciplines

“…Case 3, who had the highest average percent decrease in GFR, did not ingest any NSAIDs, and neither did Case 2. The effects of using of NSAIDs remain unresolved (11,33), although in a study of Cairns and Hew-Butler (10) seven out of 10 hyponatremic and none out of five normonatremic ultra-endurance runners consumed NSAIDs. There is a general belief that sodium supplementation prevents EAH.…”