A. General principles. There are six types of blood components including packed red blood cells (RBCs), platelets, frozen plasma, fresh frozen plasma (FFP), cryoprecipitate (CRYO), and granulocytes. In some cases, whole blood, usually in the form of reconstituted whole blood, is used. However, in most cases, blood components are preferred because each component has specific optimal storage conditions and component therapy maximizes the use of blood donations. Other blood products include those used for hematopoietic stem cell transplants, such as umbilical cord blood (UCB), and derivatives purified from blood, such as intravenous immunoglobulin (IVIG).

1. Infectious diseases. A variety of infectious diseases can be transmitted by blood transfusion. In the United States, HIV, hepatitis B virus, hepatitis C virus, syphilis, human T-lymphotropic virus types I or II (HTLV I/II), Chagas disease, and West Nile virus are screened for by medical history questionnaires and laboratory tests. Medical history questionnaires alone are used to screen for other diseases such as malaria, babesiosis, and Zika virus, although tests are being developed for babesiosis and Zika virus. The risk of acquiring a transfusion-transmitted infectious disease is very low and too low to accurately measure but has
been calculated in the United States and are shown in Table 42.1. The risks vary depending on the prevalence of the disease and the testing performed and thus differ in other countries.

Cytomegalovirus (CMV) can also be transmitted by blood, but this is rare if the blood is leukoreduced and/or it tests negative for antibodies to CMV. Animal studies suggest that variant Creutzfeldt-Jakob disease (vCJD) can also be transmitted by blood transfusion, and a few probable cases of transfusion-transmitted vCJD in humans have been reported.

1. Directed or designated donor blood. Blood donated by family members or friends for specific patients is commonly known as directed or designated donor blood. Directed donations have a small increase in rate of infectious disease transmission. Additionally, in a case of hemolytic disease of the newborn or neonatal alloimmune thrombocytopenia, the neonate’s blood contains maternal antibodies that are directed against paternally inherited antigens on blood cells. In these cases, paternal relatives’ blood may carry the same antigens rendering their blood incompatible with the baby. Finally, directed donor blood from relatives can induce an immune response against human leukocyte antigen (HLA) and other antigens against those relatives. This would complicate future therapy if the relatives were to be considered as donors of other tissue for the patient later in life. For these reasons, some medical centers do not offer directed donor blood.

2. Leukoreduction and irradiation. Whole blood, platelets, and red blood cells (RBCs) can be leukoreduced by filtration and/or irradiated to reduce the incidence of specific complications.

3. Leukoreduction. Leukoreduction filters remove approximately 99.9% of the white blood cells from RBCs and platelets. In addition, most
platelets collected by apheresis are leukoreduced even without additional filtration. Benefits of leukoreduction include the following:

a. Decreased rate of febrile transfusion reactions

b. Decreased rate of CMV transmission to a negligible rate

c. Potential to reduce a possible immunomodulatory effect of blood transfusions

d. Decreased immunization to antigens on leukocytes such as HLA. This has only been shown for some oncology patients, and its importance for neonates is unknown.

Neonates, especially premature infants, often receive leukoreduced blood components to decrease CMV transmission.

4. Irradiation. Transfusion-associated graft-versus-host disease (TA-GVHD) occurs when transfused lymphocytes mount an immune response against the patient and the patient is unable to destroy the transfused lymphocytes. Irradiation of the blood component prevents proliferation of lymphocytes and thus prevents TA-GVHD. Some premature infants and children with certain congenital immunodeficiencies are at risk for TA-GVHD. Additionally, recipients of blood from firstdegree relatives are at risk for TA-GVHD. Hence, these directed donor units must be irradiated.

1. Mechanism. RBCs provide oxygen carrying capacity for patients whose blood lacks sufficient oxygen carrying capacity due to anemia, hemorrhage, or a hemoglobinopathy. Transfusion for hemoglobinopathies is unusual in the neonatal period when most patients will have significant amounts of fetal hemoglobin.

Several types of RBC units are available that vary in the preservatives added. Chemical additives delay storage damage to RBCs allowing for extended storage times. The types of units that are currently available in the United States are as follows:

a. Anticoagulant-preservative solution units. These units contain approximately 250 mL of a concentrated solution of RBCs. The hematocrit of these units is usually 70% to 80%. In addition, these units contain 62 mg of sodium, 222 mg of citrate, and 46 mg of phosphate. Three types of units are currently approved for use in the United States. These are as follows:

i. CPD. This contains 773 mg of dextrose and has a 21-day shelf life.

ii. CP2D. This contains 1,546 mg of dextrose and has a 21-day shelf life.

iii. CPDA-1. This contains 965 mg of dextrose and 8.2 mg of adenine and has a 35-day shelf life. This is the most widely used of the anticoagulant-preservative solution units but is infrequently used because most RBC units are stored in additives.

b. Additive solution units. Most RBC units used in the United States are additive units. Four additive solutions are currently approved for use
in the United States. Each of these units contains approximately 350 mL, has an average hematocrit of 50% to 60%, and has a 42-day shelf life. Neonatologists should be aware of the glucose concentrations in these units (Table 42.2) as this can significantly impact neonatal glucose homeostasis.