A 19-year-old male presents with a 4-month history of progressive nasal obstruction, recurrent epistaxis requiring blood transfusion, and facial pain. Endoscopy reveals a large, bleeding mass in the nasopharynx. CT imaging shows a heterogeneously enhancing mass with widening of the pterygopalatine fossa and erosion of the pterygoid plates. The patient is scheduled for endoscopic resection. What is the most appropriate preoperative intervention to reduce intraoperative hemorrhage?