Efficacy of oral versus intravenous hypertonic saline in runners with hyponatremia.

OBJECTIVES

To determine more conclusively whether intravenous (IV) administration of 3% saline is more efficacious than oral administration in reversing below normal blood sodium concentrations in runners with biochemical hyponatremia.

DESIGN

Randomized controlled trial.

METHODS

26 hyponatremic race finishers participating in the 161-km Western States Endurance Run were randomized to receive either an oral (n=11) or IV (n=15) 100mL bolus of 3% saline. Blood sodium concentration (Na(+)), plasma protein (to assess %plasma volume change), arginine vasopressin (AVP), blood urea nitrogen (BUN) and urine (Na(+)) were measured before and 60 min following the 3% saline intervention.

RESULTS

No significant differences were noted with respect to pre- to post-intervention blood [Na(+)] change between intervention groups, although blood [Na(+)] increased over time in both intervention groups (+2 mmol/L; p<0.0001). Subjects receiving the IV bolus had a greater mean (± SD) plasma volume increase (+8.6 ± 4.5% versus 1.4% ± 5.7%; p<0.01) without significant change in [AVP] (-0.2 ± 2.6 versus 0.0 ± 0.5 pg/mL; p=0.49). 69% of subjects completing the intervention trial were able to produce urine at race finish with a mean (± SD) pre-intervention urine [Na(+)] of 15.2 ± 8.5 mmol/L (range 0-35; NS between groups). [BUN] of the entire cohort pre-intervention was 30.7 ± 10.5mg/dL (range 13-50).

CONCLUSIONS

No group difference was noted in the primary outcome measure of change in blood [Na(+)] over 60 min of observation following a 100mL bolus of either oral or IV 3% saline. Administration of an oral hypertonic saline solution can be efficacious in reversing low blood sodium levels in runners with mild EAH.