Blood substitute

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. The main categories of "oxygen-carrying" blood substitutes being pursued are hemoglobin-based oxygen carriers (HBOC) and perfluorocarbon emulsions. Oxygen therapeutics are in clinical trials in the U.S. and European Union, and Hemopure is available in South Africa. After William Harvey discovered blood pathways in 1616, many people tried to use fluids such as beer, urine, milk, and non-human animal blood as blood substitute. Sir Christopher Wren suggested wine and opium as blood substitute. At the beginning of the 20th century, the development of modern transfusion medicine initiated through the work of Landsteiner and co-authors opened the possibility to understanding the general principle of blood group serology. Simultaneously, significant progress was made in the fields of heart and circulation physiology as well as in the understanding of the mechanism of oxygen transport and tissue oxygenation. Restrictions in applied transfusion medicine, especially in disaster situations such as World War II, laid the grounds for accelerated research in the field of blood substitutes. Early attempts and optimism in developing blood substitutes were very quickly confronted with significant side effects, which could not be promptly eliminated due to the level of knowledge and technology available at that time.