A 52-year-old man with metastatic adenocarcinoma of the pancreas is admitted with acute onset of severe abdominal pain, hemoptysis, and hematuria. Laboratory findings show: PT 22 s (control 13 s), aPTT 52 s (control 30 s), fibrinogen 110 mg/dL, platelets 45,000/μL, D-dimer 8000 ng/mL, and hemoglobin drop from 11 g/dL to 8.5 g/dL over 6 hours. Peripheral blood smear shows schistocytes. The patient is currently on no anticoagulation. What is the most appropriate next step?