Design of a prospective, multinational registry to evaluate patients hospitalized with hyponatremia: The HN Registry

Background: Hyponatremia is a prevalent condition in patients hospitalized across a broad range of conditions, including heart failure, cirrhosis, and the syndrome of inappropriate antidiuretic hormone (SIADH) secretion. Whether present on admission or developing during hospitalization, hyponatremia has been associated with increased mortality, longer hospital stays, and higher costs. Little is known, however, about its management and outcomes outside of clinical trial settings. Methods: The Hyponatremia Registry (HN Registry) is a prospective, observational, multicenter, multinational study of patients hospitalized with either hypervolemic hyponatremia (cirrhosis and heart failure) in the United States or euvolemic hyponatremia (SIADH) in both the United States and Europe. Study enrollment began in September 2010 at community, tertiary, and academic medical centers. Overall, the HN Registry is expected to enroll >5,000 patients with hyponatremia, at >280 sites. Data will be used to characterize demographic and clinical characteristics of patients hospitalized with hyponatremia, evaluate the comparative effectiveness of available treatment modalities, and document and compare length of hospital stay as a reflection of resource use associated with hospital management. Discussion: Despite better understanding of the clinical consequences, economic impact, and prognostic significance of euvolemic and hypervolemic hyponatremia, there remains a need to evaluate current "real-world" management. The HN Registry is designed to provide contemporary data on in-hospital evaluation, management, and length of stay in a large cohort of adult patients with hyponatremia. The HN Registry generated several design and analytical challenges that required unique approaches to facilitate collection of the most clinically relevant data.