Oral Hypertonic Saline Is Effective in Reversing Acute Mild-to-Moderate Symptomatic Exercise -Associated Hyponatremia.

OBJECTIVES: To determine whether oral administration of 3% hypertonic saline (HTS) is as efficacious as intravenous (IV) 3% saline in reversing symptoms of mild-to-moderate symptomatic exercise-associated hyponatremia (EAH) in athletes during and after a long-distance triathlon.

DESIGN: Noninferiority, open-label, parallel-group, randomized control trial to IV or oral HTS. We used permuted block randomization with sealed envelopes, containing the word either "oral" or "IV."

SETTING: Annual long-distance triathlon (3.8-km swim, 180-km bike, and 42-km run) at Mont-Tremblant, Quebec, Canada.

PARTICIPANTS: Twenty race finishers with mild to moderately symptomatic EAH.

INDEPENDENT VARIABLES: Age, sex, race finish time, and 9 clinical symptoms.

MAIN OUTCOME MEASURES: Time from treatment to discharge.

METHODS: We successfully randomized 20 participants to receive either an oral (n = 11) or IV (n = 9) bolus of HTS. We performed venipuncture to measure serum sodium (Na) at presentation to the medical clinic and at time of symptom resolution after the intervention.

RESULTS: The average time from treatment to discharge was 75.8 minutes (SD 29.7) for the IV treatment group and 50.3 minutes (SD 26.8) for the oral treatment group (t test, P = 0.02). Serum Na before and after treatment was not significantly different in both groups. There was no difference on presentation between groups in age, sex, or race finish time, both groups presented with an average of 6 symptoms.

CONCLUSIONS: Oral HTS is effective in reversing symptoms of mild-to-moderate hyponatremia in EAH.