A 52-year-old man with peptic ulcer disease presents to the emergency department with haematemesis and melaena. On examination, he is pale, diaphoretic, with blood pressure 88/54 mmHg, heart rate 118/min, and respiratory rate 24/min. His haemoglobin is 6.2 g/dL, and he has received 2 litres of normal saline intravenously without haemodynamic improvement. The patient is Rh-negative with an anti-D antibody titre of 1:16 (previously sensitised). What is the most appropriate blood product to transfuse at this moment?