CEREBROSPINAL FLUID AND BLOOD ACID-BASE RELATIONSHIPS IN FETAL AND NEONATAL LAMBS AND PREGNANT EWES

The acid-base relationships between CSF and blood were studied in fetal, newborn and adult sheep to assess changes which might affect the initiation of breathing at birth. Baseline values in the fetal lambs during the last third of gestation showed a relative acidosis in the CSF of the same degree as found in the adult. During induced metabolic acidosis, the blood became acid with respect to the CSF. The CSF [HCO3-] remained unchanged and was occasionally twice the plasma level. During induced metabolic alkalosis, changes in both blood and CSF occurred. The CSF [HCO3-] remained at approximately 70-80% of the plasma level. The distribution ratio of [HCO3-] (CSF/plasma) was similar for fetal, newborn and adult sheep during large changes in plasma [HCO3-]. Alterations of CSF pH did not stimulate respiration in the fetus. © 1968.