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Developmental changes in regional cerebral blood flow in fetal and newborn lambs



Developmental changes in regional cerebral blood flow in fetal and newborn lambs



American Journal of Physiology 254(1 Pt 2): H52-H58



Developmental changes in regional cerebral blood flow (CBF) were determined using radioactively labeled microspheres to measure flow to the cortex, brain stem, cerebellum, white matter, caudate nucleus, and choroid plexus in three groups of chronically catheterized lambs under physiological conditions: 90- to 100-day preterm fetal lambs (n = 14), 125- to 136-day near-term fetal lambs (n = 11), and newborn lambs 5-44 days old (n = 10). We continually monitored heart rate, central venous pressure, and mean arterial blood pressure (MAP) and periodically measured arterial blood O2 and CO2 tensions (PaO2, PaCO2, respectively), pH, hemoglobin, and oxygen saturation (SaO2). The regional CBF measurements (ml .cntdot. 100 g-1 .cntdot. min-1) revealed that in all three age groups the high flow areas are the choroid lexus and caudate nucleus, whereas the lowest flow area is the white matter. There is, however, a different hierarchy of regional CBF in utero (cortex < cerebellum and brain stem) compared with extrauterine life in the newborn lamb (cortex and cerebellum > brain stem). Analysis of regional cerebral oxygen delivery [CBF times arterial oxygen content (CaO2)] demonstrated a progressively increasing oxygen transport to the cortex with increasing gestational maturity and after birth. Oxygen transport to the brain stem, cerebellum, and white matter increased with gestational age, but did not increase after birth. Relationships between regional CBF and natural physiological variations of cardiorespiratory parameters (PaO2, SaO2, CaO2 pH, PaCO2, and MAP) were assessed using regression analysis. Correlations of regional CBF with PaO2 and SaO2 suggest that cerebral perfusion is not primarily determined by CaO2 when variations occur within the physiological range. With increasing age, more brain regions developed oxygen sensitivity, whereas the white matter blood flow in the near-term fetus uniquely responded to natural variations of blood pressure.

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Accession: 005137622

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PMID: 3337259


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