Plasma volume studies in low birth weight infants

An average plasma volume of 46.8 ± 7.1 ml/kg and blood volume of 87.9 ± 13.6 ml/kg was found in 69 true premature infants studied during the first 12 hours of life. Respiratory distress syndrome in these infants was not associated with an altered plasma or blood volume. However, the degree of maturity, estimated by either birth weight or gestational age, was found to be inversely related to the plasma volume. Intra-uterine growth retardation, defined on the basis of disproportionately low birth weight in relation to gestational age, was associated with an elevated average plasma volume (52.0 ± 7.8 ml/kg) during the 4 hours after birth. Despite rapid adjustment of this volume to normal between 4 and 12 hours of age, the average blood volume in this group of infants was significantly elevated (102.0 ± 18.7 ml/kg). These studies reveal direct, objective and measurable differences between growth-retarded and true premature low birth weight infants and represent an attempt toward more accurate definition and understanding of intra-uterine growth retardation.