Hemopure

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. 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-based oxygen carriers (PFBOC). Oxygen therapeutics are in clinical trials in the U.S. and Europe, 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 (17th century) 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. The emergence of HIV in the 1980s renewed impetus for development of infection-safe blood substitutes. Public concern about the safety of the blood supply was raised further by mad cow disease. The continuous decline of blood donation combined with the increased demand for blood transfusion (increased ageing of population, increased incidence of invasive diagnostic, chemotherapy and extensive surgical interventions, terror attacks, international military conflicts) and positive estimation of investors in biotechnology branch made for a positive environment for further development of blood substitutes. Efforts to develop blood substitutes have been driven by a desire to replace blood transfusion in emergency situations, in places where infectious disease is endemic and the risk of contaminated blood products is high, where refrigeration to preserve blood may be lacking, and where it might not be possible or convenient to find blood type matches. Efforts have focused on molecules that can carry oxygen, and most work has focused on recombinant hemoglobin, which normally carries oxygen, and perfluorocarbons (PFC), chemical compounds which can carry and release oxygen. The first approved oxygen-carrying blood substitute was a perfluorocarbon-based product called Fluosol-DA-20, manufactured by Green Cross of Japan. It was approved by the Food and Drug Administration (FDA) in 1989. Because of limited success, complexity of use and side effects, it was withdrawn in 1994. However, Fluosol-DA remains the only oxygen therapeutic ever fully approved by the FDA. As of 2017 no haemoglobin-based product had been approved. Perfluorochemicals are not water soluble, so will not mix with blood, therefore emulsions must be made by dispersing small drops of PFC in water. This liquid is then mixed with antibiotics, vitamins, nutrients and salts, producing a mixture that contains about 80 different components, and performs many of the vital functions of natural blood. PFC particles are about 1/40 the size of the diameter of a red blood cell (RBC). This small size can enable PFC particles to traverse capillaries through which no RBCs are flowing. In theory this can benefit damaged, blood-starved tissue, which conventional red cells cannot reach. PFC solutions can carry oxygen so well that mammals, including humans, can survive breathing liquid PFC solution, called liquid breathing.