Special requirements

Phenotyped red cells

Some patients develop red cell alloantibodies when exposed to foreign red cell antigens during transfusion, or during pregnancy where fetal hemorrhage at delivery sensitizes the mother. Before transfusion, all patients are screened for red cell alloantibodies. The antibody is defined and ABO- and RhD-compatible red cells lacking the corresponding antigen are selected to prevent a hemolytic transfusion reaction. Identification of the antibody (if not previously known) may take several hours. In an emergency, if there is a high risk of the patient dying immediately through lack of red cell transfusion, it is preferable to give red cells which are simply ABO and RhD compatible, and to treat any subsequent hemolysis later. This should be discussed with transfusion medical staff.

Leukocyte-depleted (filtered) red cells

Leukodepletion may be performed within a closed system in the laboratory or using a bedside leukocyte filter. Non-hemolytic febrile transfusion reactions are mostly due to the development of HLA antibodies in the recipient which react with HLA antigens on donor leukocytes. Therefore leukocyte-depleted components may be used prophylactically to prevent HLA sensitization in patients who are chronically transfusion dependent, or who are potential recipients of organ transplants. Similarly, leukodepleted red cells may be used to lessen reactions in patients with a history of severe non-hemolytic febrile transfusion reactions. Leukocyte depletion of red cells can also be used to prevent transmission of cytomegalovirus infection if cytomegalovirus seronegative red cells are not available.

Irradiated red cells

Red cell irradiation can prevent graft versus host disease in severely immunodeficient patients (e.g. following bone marrow transplantion, intrauterine (fetal) transfusions, and those with cellular immune deficiencies). Irradiated red cells are also indicated in patients receiving red cells from a first-degree relative, where donor leukocytes may not be recognized as foreign by recipient leukocytes as many HLA antigens are common to both. Following irradiation, the potassium content rises; therefore, once irradiated, red cells should be transfused as soon as possible.

Cytomegalovirus-negative red cells

These are indicated for cytomegalovirus-seronegative patients in whom cytomegalovirus infection could be severe, for example bone marrow transplant recipients who have received marrow from a cytomegalovirus-seronegative donor, cytomegalovirus-seronegative HIV-positive patients, and neonates weighing less than 1.5 kg. All patients who may in future require a bone marrow transplant and who are cytomegalovirus seronegative, or whose status is unknown, require cytomegalovirus-negative blood components.

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