Shear stress and force required for tether formation of neonatal and adult erythrocytes.

Red blood cells (RBC) of neonates have a shorter survival time and they are more susceptible to mechanical alterations than RBC of adults. Irreversible alteration of the membrane of RBC of preterm neonates, term neonates and adults due to tether formation was studied by means of a micropipette technique. Shear stress and forces were applied with this technique in an axisymmetric configuration and were calculated with an approximation method. The applied shear stress and forces that induced tether formation were lowest for RBC of preterm neonates (1.5 Pa, 1.8 pN), in between for RBC of neonates (1.7 Pa, 2.1 pN) and highest for RBC in adults (1.9 Pa, 2.6 pN). Decreased mechanical stability of the membrane of neonatal RBC may in part cause the shorter life span, the greater tendency to endocytosis and the higher amount of irregularly shaped cells of neonatal RBC compared to RBC in adults.