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2372 Part XIII: Transfusion Medicine Chapter 138: Blood Procurement and Red Cell Transfusion 2373

TABLE 138–5. Major Randomized Controlled Trials for Safe Hemoglobin Thresholds in Children
Number
Trial Patient Population Enrolled Hgb/Hct Primary End Point Conclusions
TRIPICU 27 PICU (age from 626 7/9.5 New or progressive multiple- In stable, critically ill
3 days old to 14 years organ dysfunction syndrome children, a Hgb threshold of
of age) 7 g/dL can decrease
transfusions without
increasing adverse outcomes
PINT 32 ELBW 451 6.8–11.5 g/dL (low) Death before home discharge or In ELBW, maintaining a
7.7–13.5 g/dL (high) survival with severe retinopathy, higher Hgb results in more
bronchopulmonary dysplasia or transfusions but confers little
brain injury evidence of benefit
ELBW, extremely-low-birth-weight infants; Hct, hematocrit; Hgb, hemoglobin; PICU, pediatric intensive care units; PINT, Premature Infants in
Need of Transfusion; TRIPICU, Transfusion Strategies for Patients in Pediatric Intensive Care Units.

the recurrence of cerebral infarcts in children with sickle cell disease transfusion. Transfusing to maintain a Hgb of 10 g/dL is considered suf-
(SCD). Transfusions are usually not necessary to correct baseline ficient to suppress erythropoiesis, thereby averting the bone deformities
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anemia or alleviate vasoocclusive crises. Because transfusion also cre- and other sequelae of this disease; however, some transfusion regimens
ates complications, such as iron overload, transfusion reactions, allo- call for a pretransfusion minimum of greater than 10 g/dL, with a post-
immunization, and delayed hemolytic transfusion reactions, clinicians transfusion goal of more than 15 g/dL. Thalassemia intermedia patients
should take particular care when considering transfusions for sickle cell have more varied transfusion requirements, in keeping with the wide
patients. clinical presentation of this disease. If transfusion therapy is clinically
Chronic transfusion can lead to a high rate of RBC alloimmuniza- indicated, the transfusion recommendations are similar to those for
tion in patients with SCD. Rates ranged from 18 to 47 percent, which is thalassemia major (Chap. 48).
significantly higher than found in the general U.S. population (0.5 to 1.5
percent), or the highly transfused hematology-oncology population (9
35
to 15 percent). The reasons for this high rate include number of transfu- HEMATOPOIETIC STEM CELL
sions, age at first transfusion, the inflammatory milieu created by SCD, TRANSPLANT
36
and the different RBC antigens present in donors of mostly European
descent versus sickle cell patients of African ancestry. TRANSFUSION SUPPORT
The multiple antibodies specific for RBC antigens can cause delayed
hemolytic transfusion reactions (DHTRs). DHTRs may be difficult to The duration and specificity of transfusion support for hematopoietic
37
recognize, because some occur without any detectable antibody present, stem cell transplantation (HSCT) patients depends upon the disease,
38
and with a negative direct antiglobulin test (DAT). In addition, some the source of the stem cells, the preparative regimen applied prior to
DHTRs occur without obvious clinical signs of hemolysis. Severe cases transplant, and patient factors during the post-transplant recovery
37
of DHTR result in the hyperhemolysis syndrome, defined by a drop in period. Human leukocyte antigen (HLA) matching remains an impor-
the patient’s Hgb to a level lower than the pretransfusion value. This tant predictor of success with HSCT. As a result, the ABO barrier is
steep decline in Hgb suggests hemolysis of autologous cells, as well as often crossed when searching for the best HLA match between donor
the transfused allogeneic RBCs. and patient. Crossing the ABO barrier has little or no effect upon over-
Transfusion services may attempt to ameliorate the alloimmuniza- all outcomes; however, transfusion difficulties can arise due to anti-
tion rate by prophylactically matching donor and patient for Rh (anti- genic incompatibility between the transplanted cells and the patient.
gens D, C, c, E, e) and Kell antigens. A few will also provide an extended Transfusion support can be divided into the pre- and posttrans-
phenotype match for the common Kidd, Duffy and S antigens. Both plantation periods. Prior to an HSCT, an immunocompetent patient
strategies reduce alloimmunization, yet even with matched transfu- (e.g., aplastic anemia, hemoglobinopathies) is capable of mounting an
sions, SCD patients continue to form RBC antibodies at rates up to 58 immune response to transfusions, leading to alloimmunization against
percent of chronically transfused and 15 percent of episodically trans- HLA antigens present on the surface of leukocytes. Leukoreduction
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fused SCD patients. Most of these antibodies were made against Rh reduces alloimmunization rates, but sufficient white blood cells remain
antigens, and more than half occurred in patients who received RBCs in the unit for alloimmunization to occur. Antibodies against HLA
phenotypically matched for the corresponding Rh antigen. The likely contribute to delayed engraftment and graft rejection in some patient
40
explanation for this seeming paradox is that SCD patients have variant populations. As a result, pretransplantation transfusions in immu-
RH genes. In fact, high resolution RH genotyping showed variant alleles nocompetent patients should be avoided, as they are associated with
in 87 percent of the subjects. 37,39 increased graft failure rates. 41,42 RBC transfusions can be minimized by
using a Hgb trigger of 8 g/dL for stable patients. 43
Patients who are immunocompromised, either because of their dis-
THALASSEMIA ease, or from chemotherapy, are less likely to become immunized to for-
Thalassemia major patients are chronically transfusion dependent. eign antigens. Nonetheless, using leukoreduced products to minimize
Over time, this will lead to iron overload, and can result in RBC allo- the risk of alloimmunization is still recommended. Extra care must also
immunization. No clinical trial has been staged to find the optimal be taken if the stem cell donation comes from a blood relative. In this sit-
transfusion threshold for patients with thalassemia; however, the conse- uation family members should not give directed blood donations prior
quences of anemia can be severe and must be balanced with the risks of to transplantation, as this may lead to alloimmunization against major

Kaushansky_chapter 138_p2365-2380.indd 2372 9/18/15 11:13 AM