blood component therapy

Patient care

Irradiation of blood by gamma rays (gamma irradiation) incapacitates donor lymphocytes in whole blood, RBCs, platelets, or granulocytes. These lymphocytes are blocked from proliferating in response to foreign antigens, esp. those in the bone marrow, of immunocompromised recipients, causing transfusion-associated graft-versus-host disease. In patients who are not immunocompromised, the donor white blood cells (WBCs) are destroyed. Irradiated blood is given to patients who are donating or receiving bone marrow transplants or who have hematological or lymphatic cancers. In addition, blood used for intrauterine or neonatal exchange transfusions and blood donated by a biological relative also is irradiated.

Washing blood (RBCs, platelets) in 0.9% sodium chloride removes most, but not all, of the antibodies that could trigger an adverse reaction, esp. in patients with a history of hypersensitivity reactions to blood transfusions, even when given antihistamine prophylaxis. Washed RBCs must be given within 24 hours because the risk of bacterial contamination is increased when the saline is injected into the bag of RBCs.

Use of leukocyte-poor blood reduces the risk of unwanted responses to WBCs (leukocytes), antibodies, and cytokines by the recipient. WBCs can be eliminated by using special filters in the intravenous line or through aphoresis. The process is used for patients with a history of allergic reactions to blood products or those expected to require multiple transfusions. It also prevents transmission of cytomegalovirus (CMV) to immunocompromised patients.

Screening blood for CMV and RBC antigens helps to identify CMV-negative blood, which is needed for high-risk patients. More than half of persons over 35 years of age have been infected with CMV. However, this screened blood is beneficial for premature infants; infants under age 4 weeks; recipients of intrauterine transfusion regardless of the mother’s CMV status; any patient who requires a bone marrow or organ donor transplant if the marrow or organ donor also is CMV-negative; and CMV-negative patients who are potential transplant candidates, pregnant, about to undergo splenectomy, or have AIDS/HIV or congenital immune deficiency.table; blood transfusion;