Current Treatment Practice and Outcomes. Report of the Hyponatremia Registry.

Current management practices for hyponatremia (HN) are incompletely understood. The HN Registry recorded diagnostic measures chosen and utilization, efficacy, and outcomes of therapy for eu- or hypervolemic HN in 5 028 adult patients with serum sodium concentration ([Na+]) ≤130 mEq/L, 4 191 from 146 US and 837 from 79 EU sites. After adjudication, 3 087 patients were assessed. The most common initial monotherapy treatments were fluid restriction (35%), isotonic (15%) or hypertonic saline (2%), and tolvaptan (5%); 17% received no active agent. Median (interquartile range) [Na+] increases during the first day were: no treatment, 1.0 (4.0) mEq/L; fluid restriction, 2.0 (4.0) mEq/L; isotonic saline, 3.0 (5.0) mEq/L; hypertonic saline, 5.0 (8.0) mEq/L; tolvaptan, 4.0 (7.0) mEq/L. Adjusting for initial [Na+] with logistic regression, relative likelihoods (95% CI) for correction by ≥5 mEq/L (referent, no therapy) were 0.92 (0.84-1.01) for fluid restriction, 0.87 (0.61-1.23) for hypertonic saline, and 2.17(1.53-3.08) for tolvaptan. At discharge, [Na+] was <135 mEq/L in 78% of patients and ≤130 mEq/L in 49%. Overly rapid correction occurred in 7.9%. Initial HN treatment often employs maneuvers of limited efficacy. Despite an association with poor outcomes and availability of effective therapies, most patients with HN are discharged from hospital still hyponatremic. Future studies to assess short and long-term benefits of correction of HN with effective therapies are indicated.