AABB2025: The Impact of Reconstituted Whole Blood Products

There is no observational difference in post-exchange transfusion total serum bilirubin levels or survival outcomes between neonates who received lower versus higher hematocrit blood products, according to data from a recent study presented during the “Pediatric Transfusion Practice” oral abstract session on Saturday morning. The study results, presented by Yembur Ahmad, MD, examined neonatal exchange transfusions, focusing on whether the hematocrit of the reconstituted whole blood product used has any impact on bilirubin removal. 

Ahmad noted that double volume exchange transfusions (ETs) are a rare but critical intervention in newborns, performed to remove bilirubin and/or other pathogenic substances such as antibodies. The ET uses reconstituted whole blood manufactured in the blood bank to achieve a hematocrit specified by the NICU team. “Although uncommon, they remain the most effective and immediate method for rapidly reducing bilirubin levels and preventing kernicterus. To explore how we might improve the effectiveness of exchange transfusions in removing bilirubin, we first need to understand the underlying mechanism,” Ahmad told the audience. 

She explained that the American Academy of Pediatrics 2022 guidelines recommend using a product hematocrit of 40%, whereas the AABB Technical Manual recommends using a hematocrit of 45–60%, with the option to go higher if clinically indicated. 

“So, which of these recommendations is correct, and what evidence do we have to guide us?” she asked. “Unfortunately, there are no contemporary studies examining how the hematocrit of the exchange transfusion product affects outcomes. The AAP’s 40% recommendation is based on a 1960s study that modeled bilirubin kinetics but did not compare different hematocrits directly.” 

To address this knowledge gap, Ahmad and her colleagues conducted a retrospective review at Children’s Hospital Los Angeles (CHLA) to assess whether the hematocrit of the exchange transfusion product impacts clinical or laboratory outcomes, particularly total serum bilirubin (TSB) reduction. The team reviewed all neonatal exchange transfusions between 2018-2024 at CHLA, collecting data from blood banks and patient records, including clinical outcomes.  

In total, the researchers identified 42 exchange transfusions in 31 neonates, with some requiring more than one exchange. Throughout the six-year period, 25 ETs were performed for 20 neonates with hyperbilirubinemia. Patients were divided into two groups based on product hematocrit: low hematocrit group (<45%) and high hematocrit group (≥45%). Blood product Hcts ranged from 25.3% to 60.2%, with a mean of 45.8% (SD 7.4%). 

Ahmad noted that baseline characteristics differed notably between groups. For example, infants in the low hematocrit group had lower gestational ages and birth weights and were more likely to show signs of acute bilirubin encephalopathy. The only significant difference was that the post-exchange hematocrit was, as expected, lower in the low-hematocrit group. The findings also demonstrated no significant differences in pre- or post-exchange bilirubin levels and in survival at 30 days or one year, or long-term neurologic outcomes. 

Ahmad explained that the study was limited by small sample size, retrospective design, the HDT threshold of 45% used to divide two groups and the lack of direct measurement of bilirubin content in waste blood. 

“We believe this justifies that larger studies are warranted to further investigate the impact of blood product hematocrit on exchange transfusion outcomes,” Ahmad concluded.