The syndrome of inappropriate antidiuresis

A 62-year-old woman noted an unpleasant, sweet taste in her mouth. She otherwise felt well and was taking no medications. Because dysgeusia is a rare manifestation of hyponatremia, her serum sodium level was tested and was 122 mmol per liter. The serum osmolality was 250 mOsm per kilogram of water, the urinary osmolality 635 mOsm per kilogram of water, the urinary sodium 85 mmol per liter, and the urinary potassium 40 mmol per liter. Her thyroid function and adrenal function were normal. A computed tomographic (CT) scan of the thorax showed a mass in the lower lobe of the left lung, which proved to be a small-cell carcinoma. How should her hyponatremia be treated?