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Synthetic blood
From CopperWiki
Synthetic blood are currently labeled as "oxygen carriers" as they unable to mimic many of the other functions of blood. They do not contain cells, antibodies, or coagulation factors. Their main function is to replace lost blood volume and oxygen carrying capacity.
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[edit] Why should I be aware of this?
- Blood transfusion, though effective, carries its own risks. Allogeneic blood transfusion may cause fatal hemolytic reactions, transmit blood-borne infectious agents, and compromise overall immune function. For this reason an artificial oxygen carrying fluid needs to be readily available, free of infectious agents, and which can be used independent of the recipient blood type.
- In the 1980's, with the explosion of HIV, concerns about the safety of the blood supply stimulated renewed interest in the search for an artificial blood substitute.
- Today, though reduced considerably, a small percentage of risk of transmission of blood-borne pathogens such as HIV still remains. This, along with an increase in the number of elective surgeries, has served as a stimulus to develop a synthetic substitute for human blood.
[edit] All about synthetic blood
Successful experiments on mice in the 1960's, which showed that perfluorocarbon (PFC) solutions could be used to deliver oxygen, paved the way for developing PFCs as red blood cell substitutes.
[edit] Early synthetic blood
The first blood substitute to be approved by the US Food and Drug Administration was a PFC called Fluosol-DA. Another PFC-based oxygen carrier, Perftoran, was approved for use in Russia in 1996, although there is not much information about it readily available. A hemoglobin-based oxygen carrier, Hemopure, was approved for use in South Africa in 2001.
[edit] Search for ideal blood substitute
Scientists, however, learnt through these early trials that the human circulation and oxygen kinetics are more complicated than previously thought.
The ideal blood substitute could be defined by the following terms:
- Increased availability that would even surpass that of donated blood
- Oxygen carrying capacity, equalling or surpassing that of biological blood
volume expansion
- Universal compatibility: elimination of crossmatching
- Pathogen free: elimination of blood contained infections
- Minimal side effects
- Can survive over a wider range of storage temperatures
- Long shelf life
- Cost effective
The biggest problem about of blood transfusion relates to the antigenicity of donor blood and its ability to transmit infections. Hence, an ideal blood substitute should lack antigenicity and eliminate, or at least substantially reduce, the ability to transmit infections. It should also be readily available, have a long half-life, and should be capable of being stored at room temperature.
A major role for such blood substitutes is in trauma care and for elective surgeries. It would also benefit patients with medical conditions who are in need of long-term blood transfusions, such as patients with myelodysplastic syndrome and aplastic anemia.
[edit] Types of synthetic blood
- Perfluorocarbon emulsions (PFCE)
Perfluorocarbon emulsions are one of the two major classes of oxygen therapeutics currently on the market. They are composed of liquid perfluorocarbon emulsified in water and salt. It has a shelf life 2 years and minimizes the risk of infection or immunologic reaction resulting from a transfusion (i.e. mismatched blood type, mismatched Rh factor or diseases such as HIV and Hepatitis B). A number of side effects, such as flu-like symptoms (fever, muscle aches, nausea and vomiting), hepatosplenomegaly, and a decrease in blood platelet count, have been associated with PFCE.
- Hemoglobin-based oxygen carrier
Due to Hb's unique oxygen binding property and lack of blood type antigen, it has been considered as a possible universal substitute for red blood cells for almost a century. However, early attempts to use Hb-saline solution within the clinical setting failed due to renal toxicities. It was later determined that early Hb contained erythrocyte membrane stroma lipids that were contaminated with endotoxins, causing sever nephrotoxicity in patients. As a result the HBOCs being clinically tested today have been chemically or genetically engineered to produce desirable oxygen offloading characteristics.
[edit] Advantages of synthetic blood
- Although the blood supply is safe in countries like the US, it is not so in all regions of the world. Blood transfusion is the second largest source of new HIV infections in Nigeria. In certain regions of South Africa as much as 40% of the population has HIV/AIDS, and thorough testing is not financially feasible. A disease-free source of blood substitutes would be incredibly beneficial in these regions. [1]
- In battlefields it is often impossible to administer rapid blood transfusions. Medical care in the armed services would benefit from a safe, easy way to manage blood supply.
- Great benefit could be derived from the rapid treatment of patients in trauma situations.
- Transfused blood is currently more cost effective, but there are reasons to believe this may change. For example the cost of blood substitutes may fall as manufacturing becomes refined.
- Blood substitutes can be stored for much longer than transfused blood, and can be kept at room temperature. Most hemoglobin-based oxygen carriers in trials today carry a shelf life of between 1 and 3 years, compared to 42 days for donated blood, which needs to be kept refrigerated.
[edit] 90 degrees
In the US transfused blood has become much safer to us and instances of HIV infected blood has fallen to one in two million. However a concern that prions may infect the blood supply and quickly spread, causing an outbreak similar to that of HIV in the past is reason enough to continue investigation into alternate therapies.
Also, there are medical side effects even if blood from donor to recipient is matched. Such side effects can be eliminated with synthetic blood substitutes. Finally, because blood oxygen substitutes are expected to be different from blood by nature, it is expected that after approval of several different types, physicians will be able to choose which characteristics best suit their patients' needs.
[edit] Unlearn
In 2008 a review of clinical trail data found that hemoglobin-based blood substitutes increase the odds of deaths and heart attacks. [1]
