University of Alberta, Canadian Blood Services, Alberta, Canada
Background/Case Studies: Unstable newborns often require blood transfusions. Following a red blood cell concentrate (RCC) transfusion, newborns with similar oxygen (O2) saturation can have varying unbound oxygen (PaO2) levels, which represents the free O2 available to cells. Neonatal disease, including retinopathy of prematurity, is often associated with hyperoxia or overly high levels of free O2. The hemoglobin-oxygen (Hb-O2) affinity of RBCs changes as they undergo morphological and metabolic changes with age. Young RBCs (Y-RBCs) have been shown to possess a lower Hb-O2 affinity than old RBCs (O-RBCs); therefore, we hypothesize that the Y-RBCs within an adult RCCs would decrease the Hb-O2 affinity of preterm neonates more than the O-RBCs. This could increase unbounded O2 levels and potentially confound neonatal oxygen therapy . The aim of this study was to characterize changes in fetal red blood cell (fRBC) Hb-O2 affinity following mixing with Y-RBC and O-RBC adult RCCs (aRCCs).
Study
Design/Methods: Cord blood samples (n=13) were collected from discarded placentas of pre-term infants born between 24.0 and 32.6 weeks of age. O-negative aRCCs were supplied by the regional blood donor center and subjected to biological age profiling using a Percoll-based density separation approach which generates “young” and “old” subpopulations. fRBCs were mixed in a ratio of 1:1 with either of the subpopulations. Hb-O2 affinity and RBC indices of the fRBCs before and after mixing with both subpopulations were measured. A one-way ANOVA test was used to analyze the data.
Results/Findings: The p50 value (defined as the partial pressure of oxygen in the blood at which the hemoglobin is 50% saturated with oxygen) of fRBCs was found to be significantly lower when mixed with O-RBCs (22.36±1.21 mmHg), rather than Y-RBCs (23.34±1.17 mmHg) (p < 0.0001). Additionally, O-RBCs showed significantly higher mean cell of hemoglobin (p= 0.0004), hematocrit (p=0.001) and mean corpuscular hemoglobin concentration (MCHC)(p=0.0008) compared to Y-RBCs. Furthermore, Y-RBCs exhibited significantly higher MCV values when compared to O-RBCs upon mixing with fRBCs (p < 0.0001). Conclusions: This study has demonstrated that the addition of Y-RBCs to cord blood from preterm infants significantly decreases Hb-O2 affinity, leading to elevated levels of unbound O2 that may increase the risk of hyperoxia. Furthermore, the study highlights the potential impact that selecting aRCCs from donors who have a higher portion of Y-RBCs (ie. young female blood donors) as that may increase hyperoxia-associated disease in preterm infants.
Importance of research: This study provides insight into the optimal subpopulation of packed RBCs to use for transfusions in preterm infants to minimize the risk of adverse outcomes, such as retinopathy of prematurity. The results of this study suggest that selecting RBCs with a lower proportion of young RBCs may reduce the risk of hyperoxia and radical diseases of neonatology in preterm infants.
