Fetal erythrocyte deformability—physiologic, rheologic, and clinical considerations

Abstract

Investigation of fetal red blood cell (RBC) deformability by filtration and viscosimetry has shown that the fetal RBC varies significantly from the adult. Cord blood from 15 newborns was compared with 14 adults. Triple washed RBC's in Eagle's albumin buffer with a hematocrit of 10 ± .5% were passed through a polycarbonate filter with a 3 μ × 13.5 μ cylindrical pore under constant pressure. Flow velocity (μl/sec) was calculated. Cell suspensions were modified by adjusting temperature, pH and pO2 prior to filtration. Mean corpuscular volume (MCV), reticulocyte count and fibrinogen were measured. Viscosity of whole blood, 40% cells in autologous plasma and 80% washed cells was deterined. Filterability, as a measure of RBC deformation, was markedly decreased in newborn samples. Mean flow velocity was 2.2 μl/sec Lowered pH or pO2 in the prefiltrate resulted in significantly decreased filterability in newborn samples only. Filterability correlated poorly with MCV. Two infants with polycythemic hyperviscosity syndrome showed increased viscosity of whole blood, 80% cell suspension and markedly decreased filterability. An infant with pyknocytosis and markedly decreased filterability. An infant with pyknocytosis showed decreased filterability and elevated viscosity of an 80% suspension compared to normal newborns. Decreased deformability of the fetal RBC may be related to shortened newborn RBC survival involving diminished ability to pass through the splenic microcirculation. The decreased fetal RBC deformability which can be aggravated by acidosis and hypoxia contributes to hyperviscosity in newborns with high hematocrits. The decrease in red cell survival and anemia in infantile pyknocytosis may also be related to altered RBC deformability.