Since the late 1930's stimulated greatly by the exigencies of war, transfusion of blood or blood fractions has become important in medicine. The main reason for blood transfusion is to replace circulating red blood cells and to restore blood volume from following severe hemorrhage. Such hemorrhage can developer spontaneously, as from duodenal ulcers, or may result from injury, major surgery or childbirth. Transfusion is also used to replenish red cells in certain types of anemia, in which an individual losses the capacity to make blood at a rate sufficient to maintain full activity or even life. Medical authorities agree that blood transfusion should not be undertaken unless there are strong indication for It, inasmuch as there is a risk of transmitting hepatitis or malaria.
Blood Typing
Before blood transfusion is undertaken, the donor and recipient must be blood type, in order to insure compatibility of the transfused blood. This has become a highly specialized activity. Small amount of red cells are added to strong antiseria containing the antibodies to specific red cell factors. Antiseria are obtained from human donors deliberately immunized with the relevant blood antigens. Agglutination of cells is detected by eye or microscopic examination. Table IV showshows how sera containing the antibodies anti-A and anti-But may be used to identify the types in the ABO system. As a double check the blood cells to be transfused may be mixed with the recipienta. The process is known as cross matching. Any degree of agglutination of donor cells by the recipient's serum indicates incompatibility.