An Elderly Patient with Chronic Hyponatremia

Abstract

SummaryHyponatremia is the most common electrolyte disorder. With the aging of the population and the greater propensity of the elderly to develop hyponatremia, this electrolyte disorder is of increasing importance to the practicing nephrologist. In this Attending Rounds, an illustrative patient with hyponatremia is presented. The reasons for the increased incidence and prevalence of hyponatremia in the elderly are discussed, with emphasis on the effects of aging on urinary dilution, the frequently multifactorial nature of hyponatremia in this population, and the absence of a definite cause for inappropriate and persistent vasopressin release in many such patients. The rationale for treating the hyponatremia, even when apparently asymptomatic, is discussed, with attention to cognitive function, gait, and bone structure disturbances that increase the risk for fractures. The various available treatment approaches, including water restriction, demeclocycline, loop diuretics with NaCl supplementation, urea, and vasopressin antagonists are summarized, with emphasis on the efficacy and limitations of each of these therapies.Clin J Am Soc Nephrol 8: 469-475, 2013469-475, . doi: 10.2215 Case Description L.G. is a 73-year-old woman referred for management of chronic hyponatremia. She was known to have had hyponatremia for several years, with serum sodium levels in the range of 121-127 mEq/L. She has had four pulmonary bacterial infections during the last 7 years and was found to have radiologic evidence of bronchiectasis. She has also had several episodes of transient cerebral ischemia leading to numbness and weakness. In the last year she has had increased gait instability and sustained a fall that resulted in a pelvic fracture. She had no history of cardiac or liver disease. She has long-standing rheumatoid arthritis. Medications included omeprazole, 20 mg daily; conjugated estrogens (Premarin), 0.3 mg daily; folic acid, 0.4 mg three times daily; aspirin, 81 mg daily; and monthly vitamin B 12 injections. On physical examination she appeared to be a fragile elderly woman in no acute distress. BP was 148/78 mmHg, pulse rate was 98 beats/min, and she weighed 65 kg. She appeared to be euvolemic by examination. There were deformities of the proximal interphalangeal joints. Her neurologic examination revealed that she was fully oriented, with no focal findings, but she had an obvious gait disturbance that necessitated a walker for ambulation. Laboratory results were as follows: serum sodium, 124 mEq/L; chloride, 95 mEq/L; potassium, 4.1 mEq/L; bicarbonate, 22 mEq/L; creatinine, 0.7 mg/dl; glucose, 66 mg/dl; and uric acid, 3.8 mg/dl. Urinary sodium concentration was 75 mEq/L with a urine osmolality of 382 mOsm/kg. Result of a cosyntropin stimulation test was normal, with a baseline cortisol level of 9.2 mg/dl and a stimulated level of 18.7 mg/dl. Thyroid-stimulating hormone was normal at 3.29 mIU/L. Magnetic resonance imaging of the brain and pituitary revealed no significant abnormalities. DiscussionGiven the absence of liv...

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