A blood substitute (also called artificial blood or blood surrogate) is a substance used to mimic and fulfill some functions of biological blood. It aims to provide an alternative to blood transfusion, which is transferring blood or blood-based products from one person into another. Thus far, there are no well-accepted oxygen-carrying blood substitutes, which is the typical objective of a red blood cell transfusion; however, there are widely available non-blood volume expanders for cases where only volume restoration is required. These are helping doctors and surgeons avoid the risks of disease transmission and immune suppression, address the chronic blood donor shortage, and address the concerns of Jehovah's Witnesses and others who have religious objections to receiving transfused blood.[citation needed]
The main categories of "oxygen-carrying" blood substitutes being pursued are hemoglobin-based oxygen carriers (HBOC)[1] and perfluorocarbon emulsions.[2] Oxygen therapeutics are in clinical trials in the U.S. and European Union, and Hemopure is available in South Africa.
HBOC was invoked but never defined (see the help page).