A 71-Year-Old Man with Mild Chronic Obstructive Pulmonary Disease and Mild

A 71-year-old man with mild chronic obstructive pulmonary disease and mild hypertension is evaluated during an annual routine visit. Review of systems is notable for intermittent cough, increasing dyspnea on exertion, a 2.3-kg (5 Ib) weight loss, and fatigue. The patient takes aspirin, 81 mg/d, and hydrochlorothiazide, 50 mg/d orally. He smoked one pack of cigarettes per day for 49 years but quit smoking 2 years ago. On physical examination, distant breath sounds are audible in both lungs and there are scattered rhonchi. Chest radiograph shows a perihilar mass. Abnormal laboratory results include hemoglobin of 12.5 g/dL and a serum sodium of 127 meq/L. Endobronchial biopsy reveals small-cell lung cancer. Further staging studies suggest that the disease is limited-stage. What is the most appropriate treatment for this patient"s hyponatremia?

A) Fluid restriction to 1 L/d
B) Fluid restriction to 1 L/d and demeclocycline therapy
C) Discontinuation of hydrochiorothiazide
D) Combination chemotherapy for the small-cell lung cancer