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1 Edgar Lerma, MD, is Clinical Professor of Medicine and Educational Coordinator for the Section of Nephrology at the University of Illinois at Chicago/Advocate Christ Medical Center, Oak Lawn, IL. Helbert Rondon-Berrios, MD, is Associate Professor of Medicine and Program Director of the Nephrology Fellowship Program in the Renal-Electrolyte Division at the University of Pittsburgh School of Medicine, PA.
The conventional first-line therapy for any patient presenting with hypotonic hyponatremia due to SIAD (syndrome of inappropriate antidiuresis) is that of fluid restriction. However, we recognize that fluid restriction alone does not always work. The Expert Panel Recommendations on Diagnosis, Evaluation, and Treatment of Hyponatremia, published in 2013, identified certain criteria that are predictive of which patients are less likely to respond to fluid restriction alone (1). These include a urine-to-plasma electrolyte ratio ([urine Na + urine K]/plasma sodium [PNa]) >1 or a high urine osmolality (>500 mOsm/kg H2O).