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Clin J Sport Med. 2011 May;21(3):200-3. doi: 10.1097/JSM.0b013e31821a6450.

An intervention study of oral versus intravenous hypertonic saline administration in ultramarathon runners with exercise-associated hyponatremia: a preliminary randomized trial.

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  • 1Discipline of Emergency Medicine, University of Western Australia, Western Australia, Australia; Department of Medicine, Sir Charles Gairdner Hospital, Perth, Western Australia, Australia.



To determine whether asymptomatic exercise-associated hyponatremia (EAH) in ultramarathon runners can be corrected with either oral or intravenous (IV) 3% hypertonic saline (HTS).


Prospective with randomization into 1 of 2 intervention arms.


Western States (161 km) Endurance Run, California.


Forty-seven finishers in the event consented to be screened to identify those with EAH, defined as plasma sodium ([Na]p) <135 mmol/L at race end.


Participants with EAH but without symptoms were randomized to receive a single 100 mL dose of either oral or IV 3% HTS. Blood was drawn before intervention and at 60 minutes postintervention to measure [Na]p, and concentrations of plasma potassium, proteins, and arginine vasopressin (AVP). Body mass, percent total body water, and percent body fat were measured prerace and postrace using impedance scales.


Change in [Na]p.


Fourteen of 47 consenting finishers (30%) had EAH. Eight agreed to be randomized into the intervention protocol. Only in the IV group did [Na]p change significantly (from 130.8 to 134.6 mmol/L) over the 60 minutes post-HTS administration. Elevated AVP concentrations were seen at race finish in both the groups and remained so after HTS treatment.


In this preliminary trial, prompt administration of a 100 mL bolus of IV 3% HTS was associated with normalization of [Na]p in asymptomatic EAH, but a similar effect was not demonstrated for the same dose orally. Elevated AVP levels were observed and may play a part in the development of EAH but were not suppressed significantly by either intervention.

2011 by Lippincott Williams & Wilkins.

[PubMed - indexed for MEDLINE]
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