Most blood collected from donors is processed as follows:
• Blood components (e.g. red blood cell and platelet concentrates; fresh frozen plasma [FFP]; cryoprecipitate) are prepared from a single donation of blood by simple separation methods such as centrifugation and are transfused without processing
• Blood products (e. g. coagulation factor concentrates; albumin and immunoglobulin solutions) are produced by complex processes using the plasma from many donors as the starting material.
In most circumstances it is preferable to transfuse only the blood component or product required by the patient (component therapy) rather than use whole blood. This is the most effective way of applying donor blood, which is a scarce resource. Besides, it reduces the risk of complications from transfusion of unnecessary components of the blood. Packed red blood cells (red blood cell suspension) Under absolutely sterile conditions some 200-250 ml of plasma are removed from whole blood to be frozen as FFP or to be further processed (preferably packed by centrifuging). Packed red cells obtained in this way must be used promptly. Devoid of white blood cells («leuco-poor») these are associated with reduced incidence of febrile reactions following transfusion
Red blood cell concentrates Virtually all the plasma is removed and replaced by approximately 100 ml of an optimal additive solution, such as SAG-M which contains sodium chloride, adenine, glucose and mannitol. The packed cell volume (PCV) is about 0,65 l/l, but the viscosity is low as there are no plasma proteins in the additive solution which allows fast administration whenever necessary. Buffy coat-depleted red cell concentrates These are prepared by removal of the buffy coat, which contains most of the leucocytes and platelets. They are useful in preventing febrile reactions in patients with a previous history of reactions and in those likely to receive multiple transfusions (e.g. patients with haematological diseases). Leucocyte-depleted red cell concentrates These are usually produced by filtration and indicated for prevention of alloimmunization to leucocyte antigens (e.g. in aplastic anaemia patients who are potential recipients of allogenic bone marrow transplants).