[Changes in erythrocyte rigidity and neonatal relative viscosity during the adaptation of the newborn to extrauterine life. Observations on term and premature newborns].
BACKGROUND
The deformability of the red blood cell is a important factor in the blood viscosity and it is related with the blood viscosity and it is modified by the plasma biochemical characteristics and the composition of hemoglobin in the red blood cell. In this study, we want to compare the rheologic characteristics in the blood of cord umbilical in term and preterm newborns during the first 24 hours of life and we want to evaluate that hemorheologic modifications are explained because of the different gestational age.


METHODS
We studied 191 newborns in our maternity from 1989 until 1990. We analyzed four groups: In the first group (n = 40) of preterm newborn (gestational age < 37 weeks); in the second group (n = 72) of term newborns (gestational age > 37 weeks); the samples were obtained from umbilical artery immediately after the umbilical cord clamp; in the third group (n = 38) of preterm newborn and the fourth group of term newborns (n = 41) was studied during 24 hours after delivery. We analyzed the plasma viscosity, the viscosity of red blood cell (RBC) content and the RBC rigidity calculated by Taylor's coefficient.


RESULTS
The RBC rigidity is greater during the post-delivery period, which could be in relation with the greater values of plasma viscosity and the RBC content during the postnatal period. The comparisons between umbilical cord of term and preterm newborn they did not show differences for the RBC content viscosity and the relative viscosity. The plasma viscosity of the umbilical cord was discretely greater in the term newborn though in meaning limits statistics. In umbilical cord the hematocrit does not defer significantly between term and preterm newborns.


CONCLUSIONS
Following our data we can make firm that the RBC rigidity is increased after the delivery in term and preterm newborns and the greater relative viscosity observed in newborn to term during the first life extrauterine days in related fundamentally to the corporal liquids readjustment that occurs after of delivery.
Uberos-Fernández
J
J
Departamento de Pediatría, Hospital Universitario, Granada.
Muñoz-Hoyos
A
A
Molina-Carbayo
A
A
Ruiz-Cosano
C
C
Valenzuela-Ruiz
A
A
Molina-Font
J A
JA
D000222:Adaptation, Physiological; D001809:Blood Viscosity; D004907:Erythrocyte Deformability; D005312:Fetal Blood / Q000502:physiology; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn / Q000097:blood*; D007234:Infant, Premature / Q000097:blood*