Blood transfusion Transfusion medicine is a specialized branch of
hematology that is concerned with the study of blood groups, along with the work of a
blood bank that provides a
transfusion service with blood and other blood products. Across the world, blood products must be prescribed by a medical doctor (licensed
physician or
surgeon) in a similar way as medicines. due to blood type mismatch. Much of the routine work of a
blood bank involves testing blood from both donors and recipients to ensure that every individual recipient is given blood that is compatible and as safe as possible. If a unit of incompatible blood is
transfused between a
donor and recipient, a severe
acute hemolytic reaction with
hemolysis (RBC destruction),
kidney failure and
shock is likely to occur, and death is a possibility. Antibodies can be highly active and can attack RBCs and bind components of the
complement system to cause massive hemolysis of the transfused blood. Patients should ideally receive their own blood or type-specific blood products to minimize the chance of a
transfusion reaction. It is also possible to use the patient's own blood for transfusion. This is called
autologous blood transfusion, which is always compatible with the patient. The procedure of washing a patient's own red blood cells goes as follows: The patient's lost blood is collected and washed with a saline solution. The washing procedure yields concentrated washed red blood cells. The last step is reinfusing the packed red blood cells into the patient. There are multiple ways to wash red blood cells. The two main ways are centrifugation and filtration methods. This procedure can be performed with microfiltration devices. Risks can be further reduced by
cross-matching blood, but this may be skipped when blood is required for an emergency. The oldest form of cross-matching involves mixing a sample of the recipient's serum with a sample of the donor's red blood cells and checking if the mixture
agglutinates or forms clumps. If agglutination is not obvious by direct vision, a blood bank technologist may check for
agglutination with a
microscope. If agglutination occurs, that donor's blood cannot be transfused to that particular recipient. In a bank transfusion service, all blood specimens must be correctly identified, so labelling has been standardized using a
barcode system known as
ISBT 128. The blood group may be included on
identification tags or historically on
tattoos worn by military personnel, in case they should need an emergency blood transfusion. Frontline German
Waffen-SS had blood group tattoos during
World War II. Rare blood types can cause supply problems for
blood banks and hospitals. For example,
Duffy-negative blood occurs much more frequently in people of African origin, and the rarity of this blood type in the rest of the population can result in a shortage of Duffy-negative blood for these patients. Similarly, for RhD negative people there is a risk associated with travelling to parts of the world where supplies of RhD-negative blood are rare, particularly
East Asia, where blood services may endeavour to encourage Westerners to donate blood.
Hemolytic disease of the newborn (HDN) A
pregnant woman may carry a
fetus with a blood type that is different from her own. Typically, this is an issue if a RhD negative mother has a child with a RhD positive father, and the fetus ends up being Rh positive. In those cases, the mother can make
IgG blood group antibodies. This can happen if some of the fetus' blood cells pass into the mother's blood circulation (e.g., a small fetomaternal
hemorrhage at the time of childbirth or obstetric intervention), or sometimes after a therapeutic
blood transfusion. This can cause
hemolytic disease of the newborn (HDN) in the current pregnancy and/or subsequent pregnancies. Sometimes this is lethal for the fetus; in these cases it is called
hydrops fetalis. If a pregnant woman is known to have anti-D antibodies, the RhD blood type of a
fetus can be tested by analysis of fetal DNA in maternal plasma to assess the risk to the fetus of Rh disease. Cell-free DNA testing can determine the fetal
RHD genotype in a sample of material plasma after 10 weeks of gestation. One of the major advances of twentieth-century medicine was to prevent this disease by stopping the formation of anti-D antibodies by D-negative mothers with an injectable medication called
Rho(D) immune globulin. Antibodies associated with some blood groups can cause severe HDN, others can only cause mild HDN and others are not known to cause HDN. According to the Association for the Advancement of Blood and Biotherapies (
AABB) and the British Chief Medical Officer's National Blood Transfusion Committee, the use of group O RhD negative red cells should be restricted to persons with O negative blood, women who might be pregnant, and emergency cases in which blood-group testing is genuinely impracticable. Type AB plasma carries neither anti-A nor anti-B antibodies and can be transfused to individuals of any blood group; but type AB patients can only receive type AB plasma. Type O carries both antibodies, so individuals of blood group O can receive plasma from any blood group, but type O plasma can be used only by type O recipients. Table note 1. Assuming the absence of strong atypical antibodies in donor plasma
Universal donors and universal recipients In transfusions of red blood cells, individuals with type O Rh D-negative blood are often called universal donors. Those with type AB Rh D-positive blood are called universal recipients. However, these terms are only generally true with respect to possible reactions of the recipient's anti-A and anti-B antibodies to transfused red blood cells, and also possible sensitization to Rh D antigens. One exception is individuals with
hh antigen system (also known as the Bombay phenotype) who can only receive blood safely from other hh donors, because they form antibodies against the H antigen present on all red blood cells. Blood donors with exceptionally strong anti-A, anti-B, or any atypical blood group antibody may be excluded from blood donation of high plasma volume blood products. In general, while the plasma fraction of a blood transfusion may carry donor antibodies not found in the recipient, a significant reaction is unlikely because of dilution. Additionally, red blood cell surface antigens other than A, B and Rh D might cause adverse reactions and sensitization, if they can bind to the corresponding antibodies to generate an immune response. Transfusions are further complicated because
platelets and
white blood cells (WBCs) have their own systems of surface antigens, and sensitization to platelet or WBC antigens can occur as a result of transfusion. For transfusions of
plasma, this situation is reversed. Type O plasma, containing both anti-A and anti-B antibodies, can only be given to O recipients. The antibodies will attack the antigens of any other blood type. Conversely, AB plasma can be given to patients of any ABO blood group, because it does not contain any anti-A or anti-B antibodies. ==Blood typing==