Transfusion of red blood cells is a lifesaving measure in the management of a variety of medical and surgical conditions. The acquired immunodeficiency syndrome epidemic has raised the level of apprehension regarding the transmission of infectious disease by transfusion. This has stimulated a reexamination of the benefit-to-risk relationship for transfusion therapy. For many patients, homologous red blood cell transfusion carries great benefits, permitting surgical procedures that otherwise would not be possible and allowing medical therapies for patients who are or may become anemic. Blood transfusions once were believed to be relatively safe, but many physicians and patients recently have come to regard them as potentially dangerous. As with all potent and effective therapies, homologous blood transfusion carries risks along with benefits.
About two thirds of all red blood cell transfusions are given in the perioperative period. Newer knowledge of physiology and of the effects of anemia during and after surgery