Blood transfusions involve the intravenous administration of blood from a donor to a patient. Use of human blood for transfusion has been practiced since the early 19th century; however, knowledge of blood-group antigens and their corresponding antibodiesÑprerequisites for safe transfusionÑhas been available only since 1900. Blood is no longer transfused as whole blood. Instead, a donated unit is separated into its cellular and plasma components and transfused according to the patient's clinical requirements. In this way blood from a single donor can provide for the needs of several patients.
The safety and effectiveness of blood transfusion relates, in large measure, to careful donor selection and to pretransfusion testing. Such testing for the compatibility of blood-group antigens and antibodies between donor and patient ensures optimum survival of the transfused red blood cells. Pretransfusion tests also assess the presence of transmissible diseases in the donor's blood. Before apparently compatible units are transfused, a major crossmatch is performed wherein red cells of the donor are matched with plasma of the patient, again to ensure optimum survival of the transfused red cells.
A patient going in for scheduled surgery may opt to have some of their blood collected in advance of an anticipated transfusion, for use during the surgery.
This procedure, called autologous transfusion, eliminates the risk of transfusion-transmitted disease and also facilitates blood provision for patients with rare blood types. No age restrictions or minimum time intervals between donations are involved. Because of concerns about AIDS, the practice of autologous transfusion increased more than tenfold during the 1980s.
The infectious complications of blood transfusion spurred efforts to reduce unnecessary transfusions. Hospitals are now required to audit transfusions of red blood cells, platelets, and plasma. This has decreased inappropriate transfusions and led to more conservative use of this form of treatment.
There is no artificial substitute for blood or the red cells, white cells, and platelets it contains. Some experimental solutions, such as fluorocarbon-containing solutions or lipid-encapsulated red cell stroma-free hemoglobin, can transport oxygen to the tissues temporarily, in a manner similar to red cells (see blood), but these have not yet proven acceptable as safe substitutes.