blood transfusion blood transfusion blood transfusion is the process of transferring blood products into a person's circulation intravenously. transfusions are used for various 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. blood transfusionplastic bag with 0.5–0.7 liters containing packed red blood cells in citrate, phosphate, dextrose, and adenine (cpda) solutionicd-9-cm99.0meshd001803ops-301 code8-80medlineplus000431 red blood cells (rbc) contain hemoglobin, and supply the cells of the body with oxygen. white blood cells are not commonly used during transfusion, but they are part of the immune system, and also fight infections. plasma is the "yellowish" liquid part of blood, which acts as a buffer, and contains proteins and important substances needed for the body's overall health. platelets are involved in blood clotting, preventing the body from bleeding. before these components were known, doctors believed that blood was homogeneous. because of this scientific misunderstanding, many patients died because of incompatible blood transferred to them. medical uses red cell transfusion main article: packed red blood cells the patient receives a blood transfusion through the cannula canned blood during the blood transfusion process as the person receives their blood transfusion, the bag slowly empties, leaving behind blood that has clotted before it could be administered. historically, red blood cell transfusion was considered when the hemoglobin level fell below 100g/l or hematocrit fell below 30%. because each unit of blood given carries risks, a trigger level lower than that, at 70 to 80g/l, is now usually used, as it has been shown to have better patient outcomes. the administration of a single unit of blood is the standard for hospitalized people who are not bleeding, with this treatment followed with re-assessment and consideration of symptoms and hemoglobin concentration. patients with poor oxygen saturation may need more blood. the advisory caution to use blood transfusion only with more severe anemia is in part due to evidence that outcomes are worsened if larger amounts are given. one may consider transfusion for people with symptoms of cardiovascular disease such as chest pain or shortness of breath. in cases where patients have low levels of hemoglobin due to iron deficiency, but are cardiovascularly stable, parenteral iron is a preferred option based on both efficacy and safety. other blood products are given where appropriate, e.g., to treat clotting deficiencies. procedure illustration depicting intravenous blood transfusion before a blood transfusion is given, there are many steps taken to ensure quality of the blood products, compatibility, and safety to the recipient. in 2012, a national blood policy was in place in 70% of countries and 69% of countries had specific legislation that covers the safety and quality of blood transfusion. blood donation main article: blood donation blood transfusions use as sources of blood either one's own (autologous transfusion), or someone else's (allogeneic or homologous 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 obtained intravenously and mixed with an anticoagulant. 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 or transfusion 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. it is unclear whether applying alcohol swab alone or alcohol swab followed by antiseptic is able to reduce contamination of donor's blood. processing and testing a bag containing one unit of fresh frozen plasma 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, and immunoglobulins (antibodies). red cells, plasma and platelets can also be donated individually via a more complex process called apheresis. the world health organization (who) recommends that all donated blood be tested for transfusion-transmissible infections. these include hiv, hepatitis b, hepatitis c, treponema pallidum (syphilis) and, where relevant, other infections that pose a risk to the safety of the blood supply, such as trypanosoma cruzi (chagas disease) and plasmodium species (malaria). according to the who, 25 countries are not able to screen all donated blood for one or more of: hiv, hepatitis b, hepatitis c, or syphilis. one of the main reasons for this is because testing kits are not always available. however the prevalence of transfusion-transmitted infections is much higher in low income countries compared to middle and high income countries. all donated blood should also be tested for the abo blood group system and rh blood group system to ensure that the patient is receiving compatible blood. in addition, in some countries 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) may also be tested because of the 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. leukocyte reduction 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 reaction, cytomegalovirus infection, and platelet-transfusion 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 illustration of labeled blood bag main article: blood compatibility testing before a recipient receives a transfusion, compatibility testing between donor and recipient blood must be done. the first step before a transfusion is given is to type and screen the recipient's blood. typing of recipient's blood determines the abo and rh status. the sample is then screened for any alloantibodies that may react with donor blood. it takes about 45 minutes to complete (depending on the method used). the blood bank scientist also checks for special requirements of the patient (e.g. need for washed, irradiated or cmv negative blood) and the history of the patient to see if they have previously identified antibodies and any other serological anomalies. interpretation of antibody panel to detect patient antibodies towards the most relevant human blood group systems. further information: blood compatibility testing a positive screen warrants an antibody panel/investigation to determine if it is clinically significant. an antibody panel consists of commercially prepared group o red cell suspensions from donors that have been phenotyped for antigens that correspond to commonly encountered and clinically significant alloantibodies. donor cells may have homozygous (e.g. k+k+), heterozygous (k+k-) expression or no expression of various antigens (k−k−). the phenotypes of all the donor cells being tested are shown in a chart. the patient's serum is tested against the various donor cells. based on the reactions of the patient's serum against the donor cells, a pattern will emerge to confirm the presence of one or more antibodies. not all antibodies are clinically significant (i.e. cause transfusion reactions, hdn, etc.). once the patient has developed a clinically significant antibody it is vital that the patient receive antigen-negative red blood cells to prevent future transfusion reactions. a direct antiglobulin test (coombs test) is also performed as part of the antibody investigation. if there is no antibody present, an immediate spin crossmatch or computer-assisted crossmatch is performed where the recipient serum and donor rbc are incubated. in the immediate spin method, two drops of patient serum are tested against a drop of 3–5% suspension of donor cells in a test tube and spun in a serofuge. agglutination or hemolysis (i.e., positive coombs test) in the test tube is a positive reaction and the unit should not be transfused. if an antibody is suspected, potential donor units must first be screened for the corresponding antigen by phenotyping them. antigen negative units are then tested against the patient plasma using an antiglobulin/indirect crossmatch technique at 37 degrees celsius to enhance reactivity and make the test easier to read. in urgent cases where crossmatching cannot be completed, and the risk of dropping hemoglobin outweighs the risk of transfusing uncrossmatched blood, o-negative blood is used, followed by crossmatch as soon as possible. o-negative is also used for children and women of childbearing age. it is preferable for the laboratory to obtain a pre-transfusion sample in these cases so a type and screen can be performed to determine the actual blood group of the patient and to check for alloantibodies. compatibility of abo and rh system for red cell (erythrocyte) transfusion this chart shows possible matches in blood transfusion between donor and receiver using abo and rh system. donor o-o+b-b+a-a+ab-ab+ recipientab+ ab- a+ a- b+ b- o+ o- adverse effects in the same way that the safety of pharmaceutical products is overseen by pharmacovigilance, the safety of blood and blood products is overseen by haemovigilance. this is defined by the world health organization (who) as a system "...to identify and prevent occurrence or recurrence of transfusion related unwanted events, to increase the safety, efficacy and efficiency of blood transfusion, covering all activities of the transfusion chain from donor to recipient." the system should include monitoring, identification, reporting, investigation and analysis of adverse events near-misses and reactions related to transfusion and manufacturing. in the uk this data is collected by an independent organisation called shot (serious hazards of transfusion). transfusions of blood products are associated with several complications, many of which can be grouped as immunological or infectious. there is controversy on potential quality degradation during storage. immunologic reaction acute hemolytic reactions are defined according to serious hazards of transfusion (shot) as "fever and other symptoms/signs of haemolysis within 24 hours of transfusion; confirmed by one or more of the following: a fall of hb, rise in lactate dehydrogenase (ldh), positive direct antiglobulin test (dat), positive crossmatch" this is due to destruction of donor red blood cells by preformed recipient antibodies. most often this occurs because of clerical errors or improper abo blood typing and crossmatching resulting in a mismatch in abo blood type between the donor and the recipient. symptoms include fever, chills, chest pain, back pain, hemorrhage, increased heart rate, shortness of breath, and rapid drop in blood pressure. when suspected, transfusion should be stopped immediately, and blood sent for tests to evaluate for presence of hemolysis. treatment is supportive. kidney injury may occur because of the effects of the hemolytic reaction (pigment nephropathy). the severity of the transfusion reaction is depended upon amount of donor's antigen transfused, nature of the donor's antigens, the nature and the amount of recipient antibodies. delayed hemolytic reactions occur more than 24 hours after a transfusion. they usually occur within 28 days of a transfusion. they can be due to either a low level of antibodies present prior to the start of the transfusion, which are not detectable on pre-transfusion testing; or development of a new antibody against an antigen in the transfused blood. therefore, delayed haemolytic reaction does not manifest until after 24 hours when enough antibodies are available to cause a reaction. the red blood cells are removed by macrophages from the blood circulation into liver and spleen to be destroyed, which leads to extravascular haemolysis. this process usually mediated by anti-rh and anti-kidd antibodies. however, this type of transfusion reaction is less severe when compared to acute haemolytic transfusion reaction. febrile nonhemolytic reactions are, along with allergic transfusion reactions, the most common type of blood transfusion reaction and occur because of the release of inflammatory chemical signals released by white blood cells in stored donor blood