Repercussions of acidosis on postnatal erythrocyte deformability in term and preterm newborns

Erythrocyte deformability in newborns, a determining factor in neonatal blood hyperviscosity, is also often responsible for decreased blood flow in the microcirculation of several organs, such as the brain, kidneys, and digestive tract. In 70 neonates classified by gestational age and by the presence or absence of acidosis, we analyzed the filterability of erythrocytes in suspension through 5 polycarbonate membranes and its relation with gasometric determinations, Anion-GAP, plasma viscosity, plasma osmolality, erythrocyte volumes, and plasma lipids. Using a logistic regression analysis, controlling gestational age (p = 0.17), mean corpuscular volume (MCV) (p = 0.63), and mean corpuscular hemoglobin concentration (MCHC) (p = 0.21), the presence of acidosis (p = 0.0049, odds ratio: 3.60) is a risk factor for an increased rigidity index in newborns. Metabolic and respiratory acidosis were significantly related with lower erythrocyte deformability in the early neonatal period (below 5 days of age). Decreased plasma bicarbonate and increased Anion-GAP (even in compensated metabolic acidosis), as well as increased pCO(2) in respiratory acidosis, were significantly related with decreased erythrocyte filterability. In newborns under 32 weeks of gestational age the increase in erythrocyte rigidity index is more related to the low gestational age and increased MCV than to the presence of acidosis. These factors can produce changes in the microcirculation of these patients.