A 30-year-old patient undergoes treatment because of Werlhof's disease. Objectively: the patient is pale, there are petechial hemorrhages on the extension surfaces of forearms. Ps is 92 bpm, AP is 100/60 mm Hg. The lower edge of spleen is at a level with umbilicus. Blood count: erythrocytes: 2,8 × 1012/l, Hb - 90 g/l, Ht -0,38, thrombocytes - 30 × 109/l. The patient is being prepared for splenectomy. What transfusion medium should be chosen in the first place for the preoperational preparation?