Red-Blood-Cells In Preterm And Term Neonates Show Decreased Resistance To Plastic-Deformation When Compared To Adults

The mechanical fragility of red blood cells (RBC) in term neonates is increased compared with adult RBC. We studied tether formation (i.e., small area membrane rupture) of single RBC from preterm infants, term neonates and adults using a new micropipette technique. Point attached RBC were aspired at different negative pressures into a large micropipette with an internal diameter of about 7.8 μm.We measured (1) the critical presure to start membrane tether formation, (2) the onset of tether formation, (3) the lenth of membrane tethers after 2, 5, 10, 15, 20, 25, 30 s and (4) the relaxation behavior of the membrane tethers after releasing the RBC. At a pressure of −3mm H2O. Only RBC of preterm infants began to form tethers earlier (3.7s) than term neonates (8.2s). The tether elongation rate was also increased in preterm infants. At a pressure of −5mm H2O, We observed also tether formatoin in adult RBC. Tether formation at a pressure of −5mm H2O began after 10.2 s in adults, 4.1 s in term neonats and 3.2 s in preterm infants. 10 s after the begining of tether formation, the tether lengts were 22.15 ± 8.05 μm in preterm neonats, 11.8 ± 3.62 μm in term neonats, and 10.63 ± 4.97 μm in adults. The relaxation behavior of the tethers was similar in the three groups. Repeated tether formation of the same poi attached RBC changed the pattern of tether formation. This indicates irreversible of the cell membrane during tether formation. We conclude, the RBC in preterm infants show decreased mechanical resistance compared with full term neonats. Decreased resistance of neonatal RBC to tether formation may contribute to the shortened RBC life span, particularly in preterm infants.