Wilderness Medical Society Clinical Practice Guidelines for the Management of Exercise-Associated Hyponatremia: 2019 Update

Abstract

Exercise-associated hyponatremia (EAH) is defined by a serum or plasma sodium concentration below the normal reference range of 135 mmol$L-1 that occurs during or up to 24 h after prolonged physical activity. It is reported to occur in individual physical activities or during organized endurance events conducted in environments in which medical care is limited and often not available, and patient evacuation to definitive care is often greatly delayed. Rapid recognition and appropriate treatment are essential in the severe form to increase the likelihood of a positive outcome. To mitigate the risk of EAH mismanagement, care providers in the prehospital and in hospital settings must differentiate from other causes that present with similar signs and symptoms. EAH most commonly has overlapping signs and symptoms with heat exhaustion and exertional heat stroke. Failure in this regard is a recognized cause of worsened morbidity and mortality. In an effort to produce best practice guidelines for EAH management, the Wilderness Medical Society convened an expert panel in May 2018. The panel was charged with updating the WMS Practice Guidelines for Treatment of Exercise-Associated Hyponatremia published in 2014 using evidence-based guidelines for the prevention, recognition, and treatment of EAH. Recommendations are made based on presenting with symptomatic EAH, particularly when point-of-care blood sodium testing is unavailable in the field. These recommendations are graded on the basis of the quality of supporting evidence and balanced between the benefits and risks/burdens for each parameter according to the methodology stipulated by the American College of Chest Physicians.

Hiking Time Trial Performance in the Heat with Real-Time Observation of Heat Strain, Hydration Status and Fluid Intake Behavior

“…Having one finisher dehydrate (hiker 12) and one overhydrate (hiker 10) is comparable to the aforementioned 2013 study by Noe et al [2] where the ratio of clinical hypohydration to hyponatremia HRI incidents was 1 to 0.76. Other hikers in our HOT condition may have been at risk for EAH due to high hypotonic fluid consumption (≥1000 mL/h) or by failing to replenish appropriate amounts of electrolytes via food or sport drinks [19]. Our study did not seek to test for EAH, and the duration of the hike was probably insufficient to elicit symptoms, so these specific results should be interpreted with caution.…”

Rehydration during Endurance Exercise: Challenges, Research, Options, Methods

“…Nevertheless, the aim of rehydration should be to consume a volume of fluid that not only avoids dehydration greater than 2-4% of body mass, but also avoids overhydration. Although no single recommendation will suffice for all individuals (e.g., across a range of ambient temperatures, and with varied sweat rates, body masses, and exercise durations/intensities) [123], the following 9 recommendations are appropriate for most endurance and ultraendurance activities.…”

“…Multiple regression analysis indicated that the amount of sodium consumed during a 161 km race accounted for only 6-8% of the variance in post-race serum Na + . This recommendation also is supported by the Wilderness Medical Society Clinical Practice Guidelines [123], which advise that sodium and/or salty snacks be consumed along with an appropriate fluid volume. Salt intake should not be combined with overdrinking, which increases the risk of EHN despite sodium consumption; see recommendations 2-4 above.…”

Incidence of exercise-associated hyponatremia during a high-altitude 161-km ultramarathon

“…EAH is biochemically defined as a serum sodium ([Na + ]) concentration level <135 mmol/L, documented during or immediately after exercise 3-5 . The EAH has been reported to occur in <1-51% of the participants after different sporting events [3][4][5][6][7] . EAH can be asymptomatic or symptomatic, with life-threatening complications, such as seizures and death in severe cases 3,5,8, 9 .…”

“…One of the most serious and preventable medical derangements seen after endurance sports is exercise-associated hyponatremia (EAH). EAH is biochemically defined as a serum sodium ([Na + ]) concentration level <135 mmol/L, documented during or immediately after exercise [ 3 - 5 ]. The EAH has been reported to occur in <1-51% of the participants after different sporting events [ 3 - 7 ].…”