What Is the Role of Red Blood Cell Transfusion Threshold on Number of Transfusions in Pediatric Patients After Hematopoietic Stem Cell Transplant?
Authors: Bercovitz Rachel S. , Dietz Andrew C. , Magid Rhamy N. , Zantek Nicole D. , Smith Angela R. , Quinones Ralph R. 
Published: October 2019

Abstract
Abstract 1263

Background:
Hematopoietic stem cell transplant (HSCT) is offered as curative therapy for many childhood cancers, hematologic disorders, and metabolic diseases. Modern supportive care includes transfusion of red blood cells (RBCs) until hematopoietic recovery. Most pediatric institutions have a pre-determined threshold at which patients are transfused to avoid complications of anemia.
The Transfusion Strategies for Patients in Pediatric Intensive Care Units (TRIPICU) trial showed that lowering the RBC transfusion threshold to a hemoglobin (Hb) of 7 g/dl, down from 9.5 g/dl, resulted in 50% fewer patients receiving a transfusion. There was no difference in outcome with respect to worsened multi-organ dysfunction (Lacroix et al, 2007).
Unlike the majority of PICU patients, HSCT patients have a prolonged period of marrow aplasia, which makes it difficult to extrapolate the results of the TRIPICU study to this patient population. The objective of this study was to evaluate the impact of a difference in transfusion threshold of 2 g/dl (8 g/dl vs. 10 g/dl) on RBC utilization in the first 28 days post-transplant. We hypothesized that while a lower transfusion threshold will be associated with fewer RBC transfusions, it will not change the overall percent of patients who receive an RBC transfusion.

Methods:
This study was an IRB-approved retrospective chart review of patients 1–21 years old who had their first HSCT at either Children's Hospital Colorado at the University of Colorado, Aurora, CO (UCD) or Amplatz Children's Hospital at the University of Minnesota, Minneapolis, MN (UMN) between 1999–2009. During this time, the RBC transfusion threshold at UCD was 10 g/dl and at UMN was 8 g/dl. Transfusion events were defined as those resulting from a single order regardless of number of units or ml/kg transfused.
Patients were divided into 5 groups: 1) autologous (auto) transplant for lymphoma, 2) auto transplant for solid tumor (excluding brain tumors), 3) cord-blood allogeneic (allo) transplant, 4) bone marrow allo transplant, and 5) peripheral blood stem cell (PBSC) allo transplant. The Mann-Whitney U test was used to determine a difference in the means between groups.

Results:
Overall, more than 98% of patients had ≥1 RBC transfusions. In all groups, patients at UCD had a higher average daily Hb than at UMN. This difference was also seen pre-transplant; at UCD Day 0 average Hb was 11.0 g/dl (range: 8.2–13.9) and at UMN, 9.4 g/dl (6.5–13.7). In both the auto groups, patients at UCD received significantly more RBC transfusions than patients at UMN (Table 1). In allo patients, irrespective of stem cell source, there was no difference in the number of RBC transfusions at UCD and UMN. There was no signficant difference in the time to engraftment between the 2 institutions (data not shown).

Conclusion:
Almost all patients in this study received at least 1 RBC transfusion in the first 28 days post-transplant. A 2-g/dl difference in RBC transfusion threshold resulted in a ∼1.3-g/dl difference in average daily Hb in the patients at UMN versus UCD. However, there was only a difference in the number of RBC transfusion events between the patients undergoing auto transplant; patients at UCD received about 1.3 transfusions more than their counterparts at UMN. There was a non-significant trend toward increased transfusions in allo patients at UCD receiving either cord blood or PBSC. These data suggest that RBC transfusion trigger is not the sole predictor of RBC utilization in pediatric HSCT patients. Other variables (e. g., patient and disease factors, pre-transplant Hb, and institutional transfusion strategies) likely contribute to a patient's RBC utilization post-transplant. Prospective studies are needed to investigate these and other factors that affect number of RBC transfusions pediatric HSCT patients receive in the initial post-transplant period.

Disclosures:
No relevant conflicts of interest to declare.