Hyponatremia in a Nursing Home Population

OBJECTIVE: To determine the prevalence of hyponatremia in a nursing home population and to identify clinical factors that increase the risk for development of hyponatremia. DESIGN: Retrospective and prospective record review. SETTING: A Veterans Affairs nursing home care unit. PATIENTS: One hundred nineteen residents, who ranged in age from 60 to 103 years. Sixty ambulatory patients, 62 to 91 years of age, who attended a geriatric medicine outpatient clinic served as a reference population. MEASUREMENTS: Most recent serum sodium, creatinine, BUN, and all serum sodium determinations during the preceding 12 months; clinical diagnoses, diet, medications, and significant events at the time of recorded hyponatremic episodes; response to acute water loading in a subset of patients; number of deaths in the 12 months following entry into the study. RESULTS: In the 119 nursing home patients, ages 60 years or older, the most recent serum sodium identified 18% who were hyponatremic, compared with a prevalence of 8% in similarly aged ambulatory patients. When all serum sodium determinations for the previous 12 months were examined, 53% of the nursing home patients had at least one episode of hyponatremia during this time period. There was a high incidence of central nervous system (CNS) and spinal cord disease in the total nursing home population. Episodes of hyponatremia were frequently associated with an increased intake of fluids, given either orally or intravenously, and with tube feeding. Water load testing revealed abnormal water handling consistent with the syndrome of inappropriate antidiuretic hormone (ADH) secretion in 18 of 23 patients who had a history of hyponatremia. Seventeen percent of the patients with hyponatremia died over the following 12 months, compared to a death rate of 21% in the normonatremic patients. CONCLUSIONS: Hyponatremia is a common occurrence in nursing home residents and may be a consequence of abnormal ADH secretion resulting from CNS disease. Exposure to increased fluid intake, or to a low sodium tube-feeding diet, can lead to the onset of hyponatremia or to a worsening of an already present low-serum sodium concentration.