Page 2057 - Hematology_ Basic Principles and Practice ( PDFDrive )

1826 Part XI Transfusion Medicine

but data supporting or refuting this practice are scant and further entire procedure. Procedures to accomplish this are usually only
research is needed. available at centers that perform apheresis on relatively large numbers
of pediatric patients.
Autoimmune Hemolytic Anemia
Special Processing and Prevention of Adverse Events
Autoimmune hemolytic anemia in children occurs predominantly in in Pediatric Patients
young children, with a median age of 3.8 years, and 53% are associ-
ated with other immunologic diseases, according to one study in Special processing of blood products is performed more frequently
which 74% of the cases had both immunoglobulin G (IgG) and C3d for children than for adults. This is especially true for the preterm
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on their surface. Like adult cases, most cases of autoimmune infant population, specifically in very low-birth-weight (VLBW)
hemolytic anemia in children have antibody reactivity to all RBCs infants weighing less than 1500 g and extremely low-birth-weight
from all donors. infants weighing less than 1000 g.
Children also may develop autoimmune hemolytic anemia associ-
ated with a Donath-Landsteiner antibody, which is rarely seen in
adults. Classically the Donath-Landsteiner antibody is associated Leukocyte-Reduced Blood Components
with paroxysmal cold hemoglobinuria, a disease in which patients
developed paroxysms of hemoglobinuria following exposure to cold Leukoreduced cellular blood products are used in greater than 80%
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temperatures. However, some children with a Donath-Landsteiner of blood components transfused to children in the United States.
antibody develop symptoms of anemia that are not obviously associ- The rationale behind the use in pediatric patients has primarily been
ated with exposure to cold. The syndrome often develops following extrapolated from adult studies. In general, leukoreduction reduces
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an infection such as a respiratory infection. transmission of CMV, decreases HLA alloimmunization, and
The Donath-Landsteiner antibody is an IgG antibody that binds decreases the frequency of febrile nonhemolytic transfusion reactions.
erythrocytes, usually recognizing the P antigen, at cold temperatures The benefits of leukoreduction for neonates differ from the benefits
(<20°C [68°F]) and fixes early components of complement. The fixed for older patients. While neonates younger than 4 months of age
complement does not cause significant hemolysis at cold tempera- rarely develop transfusion reactions and rarely become HLA alloim-
tures, but upon warming, the entire complement complex binds and munized, some neonates, especially premature infants, are at risk for
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lyses the erythrocytes. Initial testing in the blood bank may be entirely transfusion-transmitted CMV. Additionally, one study of premature
normal or may reveal a positive DAT for C3. The Donath-Landsteiner infants found that implementation of universal leukoreduction was
antibody can be detected only by special testing in which the patient’s associated with decreased incidences of retinopathy, prematurity, and
plasma is incubated with erythrocytes in cold temperatures followed bronchopulmonary dysplasia, and decreased length of hospitalization. 33
by warm temperatures.
Cytomegalovirus-Seronegative Blood Components
Hematopoietic Cellular Transplant Patients
Some immunosuppressed pediatric patients, including premature
Transfusion support for HPC transplant patients is similar to that for infants, are at risk of significant disease from CMV infection.
adult patients, although there are few published studies on transfu- Transfusion-transmitted CMV can occur because many healthy
sion of pediatric HPC transplant patients. RBC transfusions are often blood donors have been infected at some point and their leukocytes
not needed in these patients whose hemoglobin level is at least 7 g/ harbor the virus. Approaches to reduce the risk of transfusion trans-
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dL. No studies in the modern era have been published on platelet mission of CMV include transfusion of blood components that test
transfusions in these patients, but use of a transfusion trigger of negative for antibodies to CMV (CMV seronegative), are leukore-
10,000 platelets/µL, like that used for adults, seems reasonable for duced, or both. Although each of these approaches is highly effective,
those patients without a significant bleeding risk other than none of these approaches provides zero risk of transfusion-transmitted
thrombocytopenia. CMV since blood from donors who were recently infected can lack
antibodies to CMV and can contain cell-free virions that are not
removed by leukoreduction. The risk of transfusion-transmitted
Apheresis CMV in VLBW infants (<1500 g) is less than 1% when the units
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are leukoreduced and CMV seronegative. This approach has not
Pediatric apheresis is used for many of the same indications as for been directly compared to using only CMV seronegative or using
adults. However, additional aspects need to be considered in treating only leukoreduced units. However, results from older studies found
pediatric patients. Many children require vascular access through a that the residual risk for transfusion-transmitted CMV in adults from
central vein because the peripheral veins of many children are too CMV seronegative blood components to be between 1% and 3% but
small. In addition, peripheral access requires patients to remain seated current risks are likely lower, and one study found no infants acquir-
or reclining with limited arm movement for the procedure duration, ing transfusion-transmitted CMV from transfusion of CMV sero-
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and younger patients are often unable to comply with this given that negative blood components. Leukoreduction is also very effective,
procedures usually last at least 2 hours. During the procedures, reducing the rate of transfusion-transmitted CMV to less than 1%
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children are susceptible to symptomatic hypocalcemia from citrate in immunosuppressed patients of all ages. Some have recommended
anticoagulation. For this reason, some pediatric centers use heparin the combined approach of using leukoreduced CMV seronegative
to anticoagulate patients, although prophylactic cation replacement units for prevention of transfusion-transmitted CMV for some of the
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can successfully prevent most symptoms in pediatric apheresis most at-risk patients. Despite confidence in the safety of using
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patients. Apheresis procedures subject the patient to volume shifts, CMV seronegative units, it may not be practical and cost effective to
which are usually a loss of less than 200 mL of fluid during the rely on CMV seronegative donors as they often constitute less than
procedure and a gain of up to 300 mL at the end of the procedure. or equal to one-half of the blood donor pool.
The actual fluid shifts depend on the machine, the procedure, and
the parameters for that procedure. In some cases, the volume shifts
may be too large to be safe for the patient. In these cases, most Irradiation
machines can be primed with 5% albumin, an RBC unit, or recon-
stituted whole blood. Using a prime solution, it is possible to minimize Mortality rates associated with TA-GVHD are as high as 80% to
fluid shifts so that the patient is effectively volume neutral for the 90%, with no effective treatments. As a result, identifying neonates