The safety of blood transfusions.

Blood transfusion therapy carries a small risk of complications-usually minor-which include allergic reactions, hemolysis, and the transmission of infections. Fatal hemolytic transfusion reactions are rare and are usually due to human error resulting in administration of ABO incompatible blood. Viral hepatitis (usually non-A, non-B) remains the major infectious complication, with a risk of two to five percent. The transmission by transfusion of AIDS has also been reported, but the risk is much lower-about 0.001%. As yet, no blood substitute is available for clinical use. Routine hepatitis B testing and the volunteer blood donor system ensure that transfusion risks are minimal in Canada. By limiting transfusion to those patients who truly need it, a high therapeutic index can be maintained.