A 28-year-old woman presents with fever, petechiae, and gum bleeding for 5 days. CBC shows WBC 85,000/μL with 70% blasts, Hb 6.2 g/dL, and platelets 15,000/μL. Bone marrow aspirate confirms acute myeloid leukemia (AML) with t(15;17). Coagulation studies show PT 18 s, aPTT 52 s, fibrinogen 80 mg/dL, and D-dimer markedly elevated. What is the most appropriate immediate next step in management?