Transfusion of one or more of the components of whole blood. The blood components mayhave been taken from the patient previously (autologous transfusion) or donated by someone else (homologous transfusion). Except in the case of acute hemorrhage, the transfusion of whole blood is rarely needed. Use of a component rather than whole blood permits several patients to benefit from a single blood donation. Blood components used in clinical medicine include packed red blood cells (RBCs); leukocyte-poor RBCs; frozen glycerolized RBCs; thawed deglycerolized RBCs; washed RBCs; whole blood; heparinized whole blood; granulocytes; platelets; and plasma and plasma fractions. The latter include antihemophilic factor (Factor VIII), prothrombin complex (Factors VII, IX, and X), gamma globulin, and albumin.