Irradiated, Washed and CMV Safe Blood

Irradiated, washed and cytomegalovirus safe components are modifications of ordinary red cells and platelets. They are not separate drugs. Each modification targets one specific risk: transfusion associated graft versus host disease (irradiation), plasma protein reactions (washing) and transmission of cytomegalovirus (leucodepletion or seronegative donors). The modification must be written into the prescription, because the blood bank will not apply it unless asked.

Irradiated components. Cellular components exposed to gamma or X-ray irradiation, with a minimum dose of 25 Gy to the centre of the bag and no part under 15 Gy. This inactivates donor T lymphocytes so they cannot engraft. Irradiation does not remove leucocytes, does not prevent cytomegalovirus transmission and does not prevent febrile reactions.

Effect on storage. Irradiation damages the red cell membrane and increases potassium leak. Irradiated red cells are usually transfused within 14 days of irradiation and never beyond the original expiry. For intrauterine transfusion, neonatal exchange transfusion and large volume neonatal transfusion, red cells are irradiated as close to use as possible, usually within 24 hours. Platelets keep their usual shelf life after irradiation.

Washed components. Red cells or platelets washed with 0.9% sodium chloride to remove plasma proteins, with some loss of cells (about 10 to 20% of red cells) and, for platelets, some loss of function. Washed red cells are usually used within 24 hours of washing and washed platelets within a few hours, because the open washing process shortens shelf life and raises bacterial risk.

Cytomegalovirus safe components. Components from cytomegalovirus seronegative donors, or leucodepleted components, which have a similar risk reduction in most settings because the virus is carried in leucocytes. Leucodepletion usually means fewer than 1 x 10⁶ leucocytes in each unit.

Special groups. Neonates, pregnant women and immunosuppressed patients need these products most. In East Africa, most adult donors are cytomegalovirus seropositive, so seronegative units are scarce and leucodepleted units are the practical option. Where blood from family or replacement donors is used, shared HLA types between relatives raise the risk of transfusion associated graft versus host disease, so irradiation is particularly important if it is available.

Irradiated components are required for:

• Congenital cellular immunodeficiency (for example severe combined immunodeficiency, DiGeorge syndrome with T cell defect).

• Hodgkin lymphoma, for life.

• Treatment with purine analogues (fludarabine, cladribine, pentostatin, clofarabine, nelarabine, bendamustine), and alemtuzumab or antithymocyte globulin, from the start of treatment, with the duration set by the haematologist.

• Allogeneic haematopoietic stem cell transplant, from the start of conditioning and for at least 6 months after, and longer with chronic graft versus host disease or continued immunosuppression.

• Autologous stem cell transplant, from the start of conditioning, or about 7 days before harvest, to at least 3 months after (6 months after total body irradiation).

• Intrauterine transfusion, and neonatal exchange transfusion, and large volume transfusion in very low birth weight infants as the neonatal service directs.

• Granulocyte transfusion, HLA matched platelets, and any component from a blood relative.

Irradiation is not needed for: routine transfusion in HIV infection, solid organ transplant recipients (unless the transplant team requires it), preterm neonates in general, and patients with ordinary haematological malignancy not on the drugs that call for irradiation.

Washed components are used for:

• Repeated severe allergic or anaphylactic reactions that continue despite plasma reduced products.

• IgA deficiency with anti-IgA antibodies, where IgA deficient donors are not available.

• Neonatal alloimmune thrombocytopenia, using washed maternal platelets, to remove maternal antibody.

• Selected large volume neonatal transfusion, to remove potassium, as the neonatal service directs.

Cytomegalovirus safe components are preferred for:

• Intrauterine transfusion and pregnant women who are seronegative or of unknown status.

• Neonates (preterm and low birth weight, especially if the mother is seronegative or unknown).

• Seronegative recipients and candidates for allogeneic haematopoietic stem cell transplant, and seronegative transplant recipients of organs from seronegative donors.

• Advanced HIV infection with seronegative status, where products are available.

How to prescribe. Write the product, the modification and the reason, for example: red cells, irradiated and leucodepleted, for allogeneic stem cell transplant. Repeat the requirement on every request, because the blood bank flag may not carry forward.

Dose, rate and time limit. Doses match those for unmodified products. Irradiated red cells: one adult unit over 2 to 4 hours, completed within 4 hours of leaving controlled storage, and neonatal volumes of 10 to 20 mL/kg at about 2 to 5 mL/kg/hour. Washed red cells must be transfused soon after collection from the blood bank, because the shelf life is hours. Washed platelets are given immediately on arrival.

Compatibility and testing. ABO and RhD compatibility and crossmatch rules are unchanged. The unit must carry a label showing irradiation date and expiry for irradiated products, and the bedside check must confirm that the label matches the prescription.

Delay and cost. Irradiation requires an irradiator, which may be at a distant blood centre, and washing needs laboratory time. Plan early and tell the blood bank about the urgency. In an emergency, do not delay a life-saving transfusion for irradiation, and give the clinical reason in the record.

Special groups.

• Neonates: irradiate close to use, use fresh red cells (within 24 hours of irradiation), and consider washing when large volumes of irradiated stored cells are given.

• Pregnancy: cytomegalovirus safe products for transfusion in pregnancy, and for intrauterine transfusion also irradiated.

• Sickle cell disease and thalassaemia: irradiation is not routine unless a transplant or drug indication exists.

Expected effects. Same haemoglobin or platelet response as unmodified products. Irradiation is silent, and washed products give a slightly lower yield.

Serious complications.

• Transfusion associated graft versus host disease in unirradiated products given to at risk patients: fever, rash, diarrhoea, liver dysfunction and pancytopenia 2 to 30 days after transfusion, with a fatality rate over 90%. Prevention is the only effective measure.

• Hyperkalaemia after transfusion of old irradiated red cells to neonates or with rapid large volumes.

• Bacterial contamination of washed products, given the open washing step.

• Cytomegalovirus infection (fever, pneumonitis, hepatitis, retinitis) in seronegative recipients despite leucodepletion, which is uncommon.

Immediate interruption criteria. Fever with rigors, hypotension, dyspnoea, urticaria with systemic signs, chest or back pain or unexplained deterioration. Stop the transfusion, assess the patient, keep intravenous access, recheck identity of patient and unit, and inform the blood bank. Do not restart without authorised clinical evaluation.

Follow up. Monitor potassium in neonates and in massive transfusion, and monitor for fever, rash and cytopenia in the weeks after unirradiated transfusion in an at risk patient.

Referral and escalation. Haematology and the blood bank for any at risk patient who received an unirradiated unit, and for suspected transfusion associated graft versus host disease (urgent, with skin and marrow assessment).