• Jesse H Morris, Nicole M Bohm, Branden D Nemecek, Rachel Crawford, Denise Kelley, Bhavna Bhasin, Paul J Nietert, and Velez Juan Carlos Q JCQ Department of Nephrology, Ochsner Clinic Foundation, New Orleans, LA. Electronic address: juancarlos.velez@ochsner.org..
• Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, SC.
• Am. J. Kidney Dis. 2018 Jun 1; 71 (6): 772-782.

BackgroundTolvaptan effectively corrects hyponatremia due to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), but undesired overcorrection can occur. We hypothesized that pretherapy parameters can predict the rapidity of response to tolvaptan in SIADH.Study DesignMulticenter historical cohort study.Setting & ParticipantsAdults with SIADH or congestive heart failure (CHF) treated with tolvaptan for a serum sodium concentration ≤ 130 mEq/L at 5 US hospitals.PredictorsDemographic and laboratory parameters.OutcomesRate of change in serum sodium concentration.MeasurementsSpearman correlations, analysis of variance, and multivariable linear mixed-effects models.Results28 patients with SIADH and 39 patients with CHF treated with tolvaptan (mean baseline serum sodium, 120.6 and 122.4 mEq/L, respectively) were studied. Correction of serum sodium concentration > 12 mEq/L/d occurred in 25% of patients with SIADH compared to 3% of those with CHF (P<0.001). Among patients with SIADH, the increase in serum sodium over 24 hours was correlated with baseline serum sodium concentration (r=-0.78; P<0.001), serum urea nitrogen concentration (SUN; r=-0.76; P<0.001), and estimated glomerular filtration rate (r=0.58; P=0.01). Baseline serum sodium and SUN concentrations were identified as independent predictors of change in serum sodium concentration in multivariable analyses. When patients were grouped into 4 categories according to baseline serum sodium and SUN median values, those with both low baseline serum sodium (≤121 mEq/L) and low baseline SUN concentrations (≤10mg/dL) exhibited a significantly greater rate of increase in serum sodium concentration (mean 24-hour increase of 15.4 mEq/L) than the other 3 categories (P<0.05). Among patients with CHF, only baseline SUN concentration was identified as an independent predictor of change in serum sodium concentration over time.LimitationsLack of uniformity in serial serum sodium concentration determinations and documentation of water intake.ConclusionsBaseline serum sodium and SUN values are predictive of the rapidity of hyponatremia correction following tolvaptan use in SIADH. We advise caution when dosing tolvaptan in patients with both low serum sodium and SUN concentrations.Copyright © 2018 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

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