A 30-year-old man with acute lymphoblastic leukemia is evaluated for fever, chills, rigors, and dyspnea, which started toward the end of a platelet transfusion given for chemotherapy-induced thrombocytopenia.

On physical examination, the patient is lethargic, flushed, and clammy. Temperature is 39.4 °C (102.9 °F), blood pressure is 90/42 mm Hg, pulse rate is 150/min, and respiration rate is 24/min (before transfusion, temperature was 37.2 °C [99.0 °F], blood pressure was 140/76 mm Hg, and pulse rate was 90/min). Oxygen saturation is 94% breathing ambient air. Rigors are noted, and skin is warm to the touch without skin changes. Head, neck, and pulmonary examinations are unremarkable. Cardiac examination reveals tachycardia but no murmurs.

In addition to stopping the transfusion and administering intravenous fluids, which of the following is the most appropriate treatment?