Chronic Hyponatremic Encephalopathy in Postmenopausal Women

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Abstract
Chronic hyponatremia is a common clinical problem in the elderly, particularly among women.1 Although the mortality among such patients is substantial,2-5 it is unclear if these patients die of hyponatremia, the effects of therapy, or associated medical conditions. It is now well accepted that acute symptomatic hyponatremia (hyponatremic encephalopathy) in menstruant women can result in death or permanent brain damage.6-9 While failure to institute active therapy (intravenous [IV] sodium chloride) in such patients may lead to increased morbidity, IV hypertonic sodium chloride therapy is both safe and effective in preventing hyponatremic brain damage.10-13 However, for the past decade it has been suggested that there are important clinical distinctions between acute and chronic hyponatremia in regard to indications for active therapy and propensity for permanent brain damage.2,7,14 Furthermore, it has been suggested that much of the brain damage associated with chronic hyponatremia may be a consequence of improper therapy rather than hyponatremic encephalopathy.2,3,15 In general, studies of patients with chronic hyponatremia usually have not included information on whether the patients were symptomatic.1-5 In the vast majority of instances, chronic hyponatremia occurs in postmenopausal women, often in association with thiazide therapy or the syndrome of inappropriate secretion of antidiuretic hormone.2,4,5,16 As a result, it is widely believed that postmenopausal women are in little danger of morbidity associated with chronic hyponatremia, and that initiation of therapy with IV sodium chloride is potentially hazardous.2,3