Diagnosing and Treating the Syndrome of Inappropriate Antidiuretic Hormone Secretion.

Abstract Background The syndromeof inappropriate antidiuretic hormone secretionis the most common cause of hyponatremiain clinical practice, but current management of hyponatremiaand outcomes in patients with syndromeof inappropriate antidiuretic hormone secretionare not well understood. The objective of the HyponatremiaRegistry was to assess the current state of management of hyponatremiadue to syndromeof inappropriate antidiuretic hormone secretionin diverse hospital settings, specifically which diagnostic and treatment modalities are currently used and how rapidly and reliably they result in an increase in serum sodium concentration ([Na + ]). A secondary objective was to determine whether treatment choices and outcomes differ across the United States and the European Union. Methods The HyponatremiaRegistry recorded selected diagnostic measures and use, efficacy, and outcomes of therapy for euvolemic hyponatremiadiagnosed clinically as syndromeof inappropriate antidiuretic hormone secretionin 1524 adult patients with [Na + ] ≤130 mEq/L (1034 from 146 US sites and 490 from 79 EU sites). A subgroup of patients with more rigorously defined syndromeof inappropriate antidiuretic hormone secretionvia measurement of relevant laboratory parameters was also analyzed. Results The most common monotherapy treatments for hyponatremiain syndromeof inappropriate antidiuretic hormone secretionwere fluid restriction (48%), isotonic(27%) or hypertonic (6%) saline, and tolvaptan(13%); 11% received no active agent. The mean rate of [Na + ] change (mEq/L/d) was greater for all active therapies than no active treatment. Hypertonic saline and tolvaptanproduced the greatest mean rate of [Na + ] change ( interquartile range, both 3.0 [6.0] mEq/L/d) compared with lower interquartile rangerates of [Na + ] change for isotonic saline(1.5 [3.0] mEq/L/d) and fluid restriction (1.0 [2.3] mEq/L/d). The general pattern of responses was similar in both the US and EU cohorts. At discharge, [Na + ] was Conclusions Current treatment of hyponatremiain syndromeof inappropriate antidiuretic hormone secretionoften uses therapies with limited efficacy; the most commonly chosen monotherapy treatments, fluid restriction and isotonic saline, failed to increase the serum [Na + ] by ≥5 mEq/L in 55% and 64% of monotherapy treatment episodes, respectively. Appropriate laboratory tests to diagnose syndromeof inappropriate antidiuretic hormone secretionwere obtained in