A 35-year-old man from Mumbai with a history of recurrent hemolytic episodes presents with acute jaundice, dark urine, and abdominal pain. Laboratory investigations reveal Hb 7.2 g/dL, reticulocyte count 18%, indirect bilirubin 5.8 mg/dL, haptoglobin <10 mg/dL, and LDH 1200 U/L. Direct antiglobulin test (DAT) is negative. Peripheral blood smear shows schistocytes and polychromasia. Renal function is normal (creatinine 0.9 mg/dL). What is the most appropriate immediate next step?