BLOOD BANK

organization that collects, stores, processes, and transfuses blood. The fact that stored blood could safely be used was demonstrated in World War I. Before the first blood banks came into operation, the physician determined the blood types of the patient's relatives and friends until the proper type was found, performed the crossmatch, bled the donor, and gave the transfusion to the patient. The discovery of many new blood types important in transfusions, and of several new crossmatching techniques, led in the 1940s to the rapid development of blood banking as a specialized field and to a gradual shift of responsibility for the technical aspects of transfusion from practicing physicians to technicians and clinical pathologists. The practicality of storing fresh blood and blood components for future needs made possible such innovations as artificial kidneys, heart-lung pumps for open-heart surgery, and exchange transfusions for infants suffering from erythroblastosis fetalis. Whole blood can be stored only for a limited time, but various components (e.g., red blood cells and plasma) can be frozen and stored for a year or longer. Therefore, most blood donations are separated and stored as components by the blood bank. These components include platelets to control bleeding; concentrated red blood cells to correct anemia; and plasma fractions, such as fibrinogen to aid clotting, gamma globulin to prevent or modify a number of infectious diseases, and albumin to augment the blood volume in cases of shock. Thus it is possible to serve the varying needs of five or more patients with a single blood donation. In some areas blood replacement programs have been established whereby persons can donate a unit (450 ml) of blood (or an equivalent monetary payment) and become enrolled in a blood bank cooperative from which they can draw unlimited blood benefits over a specified period of time, in case of future need. Despite such replacement programs, many blood banks face continual problems in obtaining sufficient donations. The chronic shortage of donors has been alleviated somewhat by the development of hemapheresis, a technique by which only a desired blood component is taken from the donor's blood, with the remaining fluid and blood cells immediately transfused back into the donor. This technique allows the collection of large amounts of a particular component, such as platelets, from a single donor. See also blood transfusion.