A 28-year-old woman presents to the emergency department with severe bleeding, petechiae, and gum bleeding. Laboratory studies show pancytopenia with hemoglobin 7.2 g/dL, platelets 15,000/µL, and WBC 2,800/µL. Coagulation studies reveal prolonged PT/aPTT, low fibrinogen (95 mg/dL), and elevated D-dimer. Bone marrow examination shows abnormal promyelocytes with abundant cytoplasmic granules and multiple Auer rods. Karyotype reveals t(15;17)(q22;q12). The structure marked **B** in the diagram — the PML-RARA fusion oncogene — is responsible for blocking myeloid differentiation at the promyelocyte stage. Given this molecular abnormality and the clinical presentation of disseminated intravascular coagulation, which of the following is the most appropriate IMMEDIATE management?