HYPONATREMIA IN A NURSING-HOME POPULATION

OBJECTIVE: To determine the prevalence of hyponatremia in a nursing ho me 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. PA TIENTS: One hundred nineteen residents, who ranged in age from 60 to 1 03 years. Sixty ambulatory patients, 62 to 91 years of age, who attend ed a geriatric medicine outpatient clinic served as a reference popula tion. 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 re corded hyponatremic episodes; response to acute water loading in a sub set of patients; number of deaths in the 12 months following entry int o the study. RESULTS: In the 119 nursing home patients, ages 60 years or older, the most recent serum sodium identified 18% who were hyponat remic, compared with a prevalence of 8% in similarly aged ambulatory p atients. When all serum sodium determinations for the previous 12 mont hs were examined, 53% of the nursing home patients had at least one ep isode of hyponatremia during this time period. There was a high incide nce of central nervous system (CNS) and spinal cord disease in the tot al nursing home population. Episodes of hyponatremia were frequently a ssociated with an increased intake of fluids, given either orally or i ntravenously, and with tube heeding. Water load testing revealed abnor mal water handling consistent with the syndrome of inappropriate antid iuretic 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 occu rrence 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.