Acute pulmonary edema

A 62-year-old man presents with a three-day history of progressive dyspnea, nonproductive cough, and low-grade fever. He had been hospitalized two years earlier for congestive heart failure. His blood pressure is 95/55 mm Hg, his heart rate 110 beats per minute, his temperature 37.9 degrees C, and his oxygen saturation while breathing ambient air 86 percent. Chest auscultation reveals rales and rhonchi bilaterally. A chest radiograph shows bilateral pulmonary infiltrates consistent with pulmonary edema and borderline enlargement of the cardiac silhouette. How should this patient be evaluated to establish the cause of the acute pulmonary edema and to determine appropriate therapy?