The Effect of the Dose of Isotonic Saline on the Correction of Serum Sodium in the Treatment of Hypovolemic Hyponatremia.

Background: Overcorrection of serum sodium (SNa) during therapy of hyponatremia can result in osmotic demyelination syndrome. Our aim was to determine the relationship between the isotonic saline solution dose (ISSD) administered and the 24-h SNa increase (24SNa) in patients with hypovolemic hyponatremia (HH).

Methods: Retrospective study of HH patients treated with ISS in a tertiary hospital of Madrid, Spain, between 1 January-30 May 2019. The 24-h ISSD received and corresponding 24SNa were calculated. The latter was classified as 3 groups: ≥8 mmol/L, ≥6 mmol/L, or <4 mmol/L. Multivariate regression analyses were performed and ROC curves calculated to study the relationship between ISSD and 24SNa.

Results: Thirty patients were included, age 72 years (60-80), 50% were women. 24SNa was ≥8 mmol/L/24 h in 33%, ≥6 mmol/L/24 h in 50%, and <4 mmol/L/24 h in 30%. Median ISSD in each group was: 32 mL/kg/24 h (29-37), 31 mL/kg/24 h (25-33), and 20 mL/kg/24 h (14-22), respectively. An ISSD ≥ 30 mL/kg/24 h had an odds ratio (OR) of 16 (95% CI: 2.5-95.1; = 0.004) for a 24SNa ≥8 mmol/L, with a sensitivity and specificity of 80%.

Conclusions: The 24SNa depends on ISSD. An ISSD between 23-30 mL/kg/24 h seems to be safe and effective.