A 48-year-old male patient with a 2-year history of poor appetite and fatigue, accompanied by intermittent epistaxis and gingival bleeding, developed abdominal distension over the past month. Four hours after eating pancakes, he suddenly experienced palpitations, sweating, and vomited 200ml of dark red blood. On emergency examination: BP 80/55 mmHg, heart rate 120 bpm, splenomegaly with spleen palpable 3.0 cm below the costal margin. The most immediate intervention for this patient is: