Filterability of Erythrocytes and Whole Blood in Preterm and Full-Term Neonates and Adults

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Abstract
Filtration techniques are widely used to assess red blood cell (RBC) deformability and flow behavior of RBC in microcirculation. In this study filtration rates of RBC from 10 very low birth weight infants (24–30 wk gestation), 10 more mature preterm infants (31–36 wk gestation), 10 full-term neonates, and 10 adults were measured by using Nucleopore filters with pore diameters of µm and filtration pressures of 1, 2, 5, and 10 cm H2O. The major results follow: 1) At each of four filtration pressures, filtration rates of washed RBC were significantly (p2O. 2) The filtration rates increased with decreasing MCV (r=–0.86). 3) The filter flow resistance (computed as ratio of filtration pressure and filter flow rate) decreased as the filtration pressure was raised from 1 to 10 cm H2O. The largest drop, 31% (p0.05), was seen in adults. 4) At pressure of 1 cm H2O the calculated mean transit time for RBC through the 5–µm pores was on an average 3.7 times longer in the smallest preterm infants than in the adults (19.7 ± 7.8 and 5.3 ± 1.4 ms, respectively), whereas the factor was only 2.7 at a pressure of 10 cm H2O (13 ± 0.4 and 0.5 ± 0.1 ms, respectively). 5) Filtration rates of whole blood were determined at a pressure of 10 cm H2O. These filtration rates were significantly (p<0.05) less compared with filtration rates of washed RBC. The largest difference was observed in the smallest preterm infants (–77%), the smallest difference in adults (–41%). In conclusion, the filtration rate of RBC from preterm and term neonates may be lower than that of adults because of the larger size of neonatal RBC. At high pressure, filterability of neonatal RBC improves, possibly because of decreased resistance of neonatal RBC to elastic deformation. Filtration of whole blood from neonates may, in addition, be impaired because of the higher number of poorly deformable leukocytes and erythroblasts.