Monday, 14 May 2012

Blood transfusion



Blood transfusion is the process of receivingblood products into one's circulationintravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood. Early transfusions used whole blood, but modern medical practice commonly uses only components of the blood, such as red blood cells, white blood cells,plasma, clotting factors, and platelets.
They typically are only recommended when a persons hemoglobin fall below 70-80 mg/dL.One may consider transfusion for people with symptoms of cardiovascular disease such as chest pain or shortness of breath. Globally around 85 units of blood are transfused in a given year.

Pre-transfusion procedures


Before a blood transfusion is given, there are many steps taken to ensure quality of the blood products, compatibility, and safety to the recipient.

Blood donation


Blood transfusions typically use two sources of blood: one's own (autologous transfusion), or someone else's (allogeneic transfusion). The latter is much more common than the former. Using another's blood must first start with donation of blood. Blood is most commonly donated as whole blood intravenously and collecting it with ananticoagulant. In developed countries, donations are usually anonymous to the recipient, but products in a blood bank are always individually traceable through the whole cycle of donation, testing, separation into components, storage, and administration to the recipient. This enables management and investigation of any suspected transfusion related disease transmission ortransfusion reaction. In developing countries the donor is sometimes specifically recruited by or for the recipient, typically a family member, and the donation occurs immediately before the transfusion

Processing and testing of blood products after donation


Donated blood is usually subjected to processing after it is collected, to make it suitable for use in specific patient populations. Collected blood is then separated into blood components by centrifugation: red blood cells, plasma, platelets,albumin protein, clotting factor concentrates,cryoprecipitate, fibrinogen concentrate, andimmunoglobulins (antibodies). Red cells, plasma and platelets can also be donated individually via a more complex process called apheresis.
  • All donated blood are tested for infections. The current protocol tests donated blood for HIV-1,HIV-2, HTLV-1, HTLV-2, Hepatitis B, Hepatitis C, Syphilis (T pallidum), Chagas disease (T cruzi), and West Nile Virus. In addition, platelet products are also tested for bacterial infections due to its higher inclination for contamination due to storage at room temperature. Presence of Cytomegalovirus (CMV) is also tested because of risk to certain immunocompromised recipients if given, such as those with organ transplant or HIV. However, not all blood is tested for CMV because only a certain amount of CMV-negative blood needs to be available to supply patient needs. Other than positivity for CMV, any products tested positive for infections are not used.
  • All donated blood are also tested for ABO and Rh groups, along with the presence of any red blood cell antibodies.
  • Leukoreduction is the removal of white blood cells by filtration. Leukoreduced blood products are less likely to cause HLA alloimmunization (development of antibodies against specific blood types), febrile non-hemolytic transfusion reactions, cytomegalovirus infections, and platelet-transfuion refractoriness.
  • Pathogen Reduction treatment that involves, for example, the addition of riboflavin with subsequent exposure to UV light has been shown to be effective in inactivating pathogens (viruses, bacteria, parasites and white blood cells) in blood products. By inactivating white blood cells in donated blood products, riboflavin and UV light treatment can also replace gamma-irradiation as a method to prevent graft-versus-host disease (TA-GVHD)

Compatibility testing





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