Deformability of Density Separated Red Blood Cells in Normal Newborn Infants and Adults

Abstract

SummaryThe deformability of neonatal and adult red blood cells (RBC) was studied using both unseparated and density (i.e., age) fractionated RBC. Blood samples were obtained from to normal newborn infants (placental blood) and to adults. Deformability was measured by direct microscopic observation of RBC subjected to shear stresses of 2.5-500 dynes/cm 2 using a counter-rotating Rheoscope. There was no significant difference in deformability between unseparated neonatal and adult RBC at any shear stress. The 3% least dense ("youngest") RBC showed significantly decreased hemoglobin concentrations (MCHC), increased volumes (MCV) and elevated deformability at any shear stress when compared to the 3% most dense ("oldest") cells, with the values for the unseparated RBC lying between these two extremes. The least dense neonatal RBC had a significantly lower MCHC and higher deformability than the least dense adult cells; however, the most dense neonatal RBC had lost more volume than the adult cells (33 versus 17%), had a higher MCHC, and were less deformable than the most dense adult cells. This indicates that the accelerated decrease in deformability of aging neonatal RBC is related to the more pronounced increase in MCHC, which is the principal determinant of the internal viscosity of the RBC Speculation The shortened survival time of neonatal red blood cells (RBC) is probably the consequence of accelerated aging of neonatalRBC. Differences in biochemical composition and a decrease in some RBC activities, which are important for the maintenance of membrane integrity, cell volume, and deformability might be responsible for the faster loss of membrane fragments and deformability of neonatal RBC when compared to adult cells. These alterations presumably impede the ability of aging neonatal RBC to pass the narrow splenic slits, thus promoting their eventual destruction by macrophages.

Geometry of Neonatal and Adult Red Blood Cells

“…Deformation enables RBC to adapt to high shear forces in large vessels with rapid flow and to pass through narrow capillaries and splenic slits with diameters less than that of the resting RBC. The similar surface area index (i.e., excess surface area) of the neonatal and adult RBC indicates that they have the same shape and the same deformability provided that other factors affecting RBC deformability are not different (15,16). This agrees with findings of similar deformability for neonatal and adult RBC in the rheoscope (16) and in viscometers (14), because cell deformability measured in these devices largely depends on the excess surface area (19).…”

“…The volume and diameter measurements of neonatal cells also are in agreement with other studies (16,18). Note that calculation of surface area from measured diameter and mean thickness by assuming a disc shape for the RBC overestimates the surface area: the calculated surface areas are 166 pm2 for neonatal RBC and 141 pm2 for adult cells.…”

“…The volume of RBC in full-term newborn infants is about 20% higher than in adults and the diameter of neonatal RBC is increased by about 10% compared to adults (16,18). Riegel et al (18) computed the surface area of neonatal RBC from measured diameters of dried erythrocytes and calculated mean cell thickness using a disc model.…”

Characteristics and Functional Properties of Red Cells during the First Days of Life

“…Previous rheological studies in cord blood have demonstrated that although neonatal RBC have a larger volume and greater sur face area, only a small fraction of the denser cells are less deformable than adult RBC [12][13][14], Shear rate determinations and cord blood RBC geometry confirmed that there are only small differences in deformability of adult and neonate RBC, at least at birth [15,16], Our determinations of flow rate in whole cord blood confirm previously reported find ings [12][13][14]17] of a flow rate which is not significantly different from that of adult blood. However the follow-up studies clearly indicate that the conditions observed in cord blood rapidly change during the first days of life.…”

Computational Hemodynamic Analysis in Congenital Heart Disease: Simulation of the Norwood Procedure

“…Due to the relatively large sizes of the vessels compared to individual blood cells 18 and typically great shear stress in larger arteries, 5 the blood was assumed to be a Newtonian fluid with a constant density (q = 1060 kg m À3 ) and viscosity (l = 4.0 9 10 À3 Pa s), [15][16][17] whilst the blood forces were omitted. Therefore, the N-S equations are turned into the following form:…”