A 52-year-old man with newly diagnosed acute myeloid leukemia (AML) presents to the emergency department with severe headache, confusion, and spontaneous bleeding from gums and venipuncture sites. Laboratory investigations show: hemoglobin 7.8 g/dL, WBC 185,000/μL (85% blasts), platelet count 12,000/μL, PT 18 s (normal 12–14), aPTT 52 s (normal 24–36), fibrinogen 85 mg/dL (normal 200–400), D-dimer markedly elevated. What is the most appropriate immediate management?