Exercise-Associated Hyponatremia Management

Primary Treatment Recommendations

For a collapsed marathon runner with severe hyponatremia and high urine sodium, the American College of Sports Medicine recommends immediately administering 3% hypertonic saline as bolus therapy, specifically 100 mL boluses given over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms resolve 1, 2
The target correction is a 4-6 mEq/L increase within the first 6 hours, with a maximum correction limit of 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome 1, 3

Exercise-associated hyponatremia (EAH) is a dilutional hyponatremia resulting from increased total body water relative to exchangeable sodium stores, not primarily from sodium loss, according to the American College of Sports Medicine 4, 5
The high urine sodium reflects physiologic natriuresis in response to volume expansion from excessive fluid intake during the race 4
EAH is characterized as euvolemic to hypervolemic hyponatremia, not hypovolemic, despite the runner appearing dehydrated from exertion 4, 5

Marathon running time typically greater than 4 hours is a risk factor for EAH 4
Excessive fluid consumption during the race is a key risk factor for developing EAH 4, 5
Altered renal function from prolonged exercise can contribute to the development of EAH 4

Serum sodium should be checked every 2 hours during the initial correction phase 3
Monitoring for symptom resolution and watching for signs of overcorrection are crucial in managing EAH 1, 2, 3

EAH has caused deaths in the USA and UK, making rapid recognition and appropriate treatment critical, with an incidence among marathon runners ranging from 3-22% 4
Severe hyponatremia with altered mental status can progress to cerebral edema, seizures, coma, and death if untreated 4, 5

Patients with severe symptoms, including altered mental status, confusion, or decreased level of consciousness, require immediate emergency room evaluation and treatment, as recommended by the American College of Sports Medicine, due to the risk of cerebral edema, coma, and death 6
Seizures or tonic-clonic activity in patients with suspected water intoxication necessitate emergency department evaluation and treatment, according to the American College of Sports Medicine 6
Collapse with mental status changes in patients with water intoxication requires emergency room evaluation and treatment, as per the American College of Sports Medicine 6, 7

The American College of Sports Medicine is not cited for the administration of 3% hypertonic saline, however, point-of-care serum sodium testing is crucial for confirming diagnosis and guiding treatment in emergency rooms 6
Airway management is essential for patients with altered mental status or seizures, as recommended by the American College of Sports Medicine 7, 8

Endurance athletes with exercise duration >4 hours, patients with known excessive fluid consumption, and female athletes or those with low body mass index warrant immediate ER evaluation even with milder symptoms, according to the American College of Sports Medicine 6, 9
The incidence of exercise-associated hyponatremia ranges from 3-22% among marathon runners, making this a common and serious concern, as reported by the American College of Sports Medicine 6, 9