Current issues for nurse practitioners: Hyponatremia

PURPOSE: To review the assessment, diagnosis, and management of hyponatremia (serum sodium <135 mEq/L), the most common electrolyte disturbance as a result of dysregulation of water balance in hospitalized or institutionalized patients. DATA SOURCES: Comprehensive search using keywords AVP receptor antagonists, hyponatremia, SIADH, conivaptan, tolvaptan, lixivaptan, nurse practitioner, and others was carried out using the National Library of Medicine (PubMed) Web site from which full-text articles were obtained. Meeting abstracts were obtained from scientific sessions including the American Society of Nephrology Renal Week 2004 and the Endocrine Society's 87th Annual Meeting (2005). The Vaprisol (conivaptan hydrochloride injection) package insert was referenced and obtained from FDA.gov. CONCLUSIONS: A diagnosis of hyponatremia requires thorough investigation for underlying causes and prompt treatment to prevent poor patient outcomes. In clinical trials, a new class of drugs called the arginine vasopressin (AVP) receptor antagonists or aquaretics has been shown to be safe and effective for the treatment of hyponatremia. Among this class of agents, intravenous conivaptan hydrochloride, indicated for the treatment of euvolemic hyponatremia in hospitalized patients, is the first drug in class approved for use. IMPLICATIONS FOR PRACTICE: Elderly patients, and those with certain conditions such as heart failure, tuberculosis, cirrhosis, and head injury, may be at increased risk for hyponatremia. In hospitalized patients following surgery and the use of certain medications, hyponatremia is a common condition. A thorough understanding of the physiology of water balance and the risk factors associated with hyponatremia is essential for prompt and effective intervention. Awareness of the limitations of conventional therapies and the availability of new treatment options for hyponatremia allows clinicians to optimize patient care.