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Cerebral haemodynamics in growth-retarded preterm infants during the first 3 days of life
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Neonatal Society Meeting/Early Human Development41 (1995) 221-233
Cerebral haemodynamics in growth-retarded preterm infants during the first 3 days of life. J.H. Meek, C.E. Elwell, E.O.R. Reynolds, J.S. Wyatt, Department of Paediatrics, University College London, London, WCIE 6JJ, UK. We have previously demonstrated significant increases in cerebral blood flow (CBF) and cerebral blood volume (CBV) after birth in normally grown preterm infants undergoing intensive care. The purpose of this study was to test the hypothesis that fetuses with indirect evidence of chronic intrauterine hypoxia would fail to demonstrate these adaptive changes after birth. Twenty preterm infants were studied by near infrared spectroscopy (NIRS) on 1-3 occasions during the first 3 days of life. Ten were growth retarded with birth weights less than the third centile for gestational age and seven of these had evidence of absent or reversed end-diastolic umbilical artery flow before delivery. Their median birthweight was 663 (range 460-1243) g and their median gestational age was 28 (range 26-30) weeks. The other 10 infants had birthweights above the third centile, median 927 (700-1443) g and median gestational age 28 (24-33) weeks. (Cranial ultrasounds in all infants showed no significant abnormality at the time of the study.) The normally grown infants demonstrated a rise in CBF of median 3.8 (1.4-8.9) ml. 100 g-i .min-t per day, whereas two of the growth retarded fetuses had abnormally high cBF on the first day and in four out of the seven with repeated observations, CBF decreased by a median of 6.53 (1.3-11.8) ml. 100 g-I .min-J per day (P < 0.05 compared with normal infants). Similar changes were observed in CBV and abnormalities were more pronounced in the more mature infants. We conclude that some growth retarded preterm infants fail to demonstrate normal adaptive changes in cerebral haemodynamics after birth, possibly due to a 'head sparing' response to chronic intrauterine hypoxia. The effect of pH on neonatal brain cilia. C. O'Callaghan, S.S. Jandu, B.J. Mohammed, Department of Child Health, University of Leicester, Leicester, UK. Introduction: The function of ciliated ependymal cells which line the ventricular surface of the brain is unknown. We have developed a method to study brain cilial beat frequency (CBF) in vitro and have assessed the effect of pH on cilial function. Methods: Thin ependymal sections (Lester hooded rats) were mounted in a perfusion chamber at 37°C. Images from a water immersion lens (Leitz) were transferred to a high resolution monitor. CBF was determined by using a modified photodiode technique. Samples were perfused for 30 min in artificial CSF, followed by medium 199 (pH 7.4) for 30 min. Medium 199 at a chosen pH (6, 6.5, 6.8, 7, 7.4, or 8) was then perfused for 2 h followed by a 60-min washout phase (pH 7.4). Results: The mean (S.D.) CBF in artificial CSF was 19.5 (1) Hz and in medium 199, 20.2 (1.1) Hz. CBF decreased markedly with pH values below 7 (pH 6, CBF = 0; pH 6.5, CBF = 4.4 (4); pH 6.8, CBF = 5 (5)). There was no change in CBF at pH 7 and 7.4. A pH of 8 caused a decrease in CBF to 15 Hz (2). CBF returned towards normal following re-perfusion with medium 199, pH 7.4. The co-efficient of variation for brain CBF was 5.5% (pH 7.4). Conclusion: Changes in pH have a profound effect on brain ciliary beat frequency. We assume that this effect is directly related to change in intracellular pH. [ll
Worthington,F. (1963): Science, 139, 221-224.
Neonatal Society Meeting/Early Human Development41 (1995) 221-233
Cerebral haemodynamics in growth-retarded preterm infants during the first 3 days of life. J.H. Meek, C.E. Elwell, E.O.R. Reynolds, J.S. Wyatt, Department of Paediatrics, University College London, London, WCIE 6JJ, UK. We have previously demonstrated significant increases in cerebral blood flow (CBF) and cerebral blood volume (CBV) after birth in normally grown preterm infants undergoing intensive care. The purpose of this study was to test the hypothesis that fetuses with indirect evidence of chronic intrauterine hypoxia would fail to demonstrate these adaptive changes after birth. Twenty preterm infants were studied by near infrared spectroscopy (NIRS) on 1-3 occasions during the first 3 days of life. Ten were growth retarded with birth weights less than the third centile for gestational age and seven of these had evidence of absent or reversed end-diastolic umbilical artery flow before delivery. Their median birthweight was 663 (range 460-1243) g and their median gestational age was 28 (range 26-30) weeks. The other 10 infants had birthweights above the third centile, median 927 (700-1443) g and median gestational age 28 (24-33) weeks. (Cranial ultrasounds in all infants showed no significant abnormality at the time of the study.) The normally grown infants demonstrated a rise in CBF of median 3.8 (1.4-8.9) ml. 100 g-i .min-t per day, whereas two of the growth retarded fetuses had abnormally high cBF on the first day and in four out of the seven with repeated observations, CBF decreased by a median of 6.53 (1.3-11.8) ml. 100 g-I .min-J per day (P < 0.05 compared with normal infants). Similar changes were observed in CBV and abnormalities were more pronounced in the more mature infants. We conclude that some growth retarded preterm infants fail to demonstrate normal adaptive changes in cerebral haemodynamics after birth, possibly due to a 'head sparing' response to chronic intrauterine hypoxia. The effect of pH on neonatal brain cilia. C. O'Callaghan, S.S. Jandu, B.J. Mohammed, Department of Child Health, University of Leicester, Leicester, UK. Introduction: The function of ciliated ependymal cells which line the ventricular surface of the brain is unknown. We have developed a method to study brain cilial beat frequency (CBF) in vitro and have assessed the effect of pH on cilial function. Methods: Thin ependymal sections (Lester hooded rats) were mounted in a perfusion chamber at 37°C. Images from a water immersion lens (Leitz) were transferred to a high resolution monitor. CBF was determined by using a modified photodiode technique. Samples were perfused for 30 min in artificial CSF, followed by medium 199 (pH 7.4) for 30 min. Medium 199 at a chosen pH (6, 6.5, 6.8, 7, 7.4, or 8) was then perfused for 2 h followed by a 60-min washout phase (pH 7.4). Results: The mean (S.D.) CBF in artificial CSF was 19.5 (1) Hz and in medium 199, 20.2 (1.1) Hz. CBF decreased markedly with pH values below 7 (pH 6, CBF = 0; pH 6.5, CBF = 4.4 (4); pH 6.8, CBF = 5 (5)). There was no change in CBF at pH 7 and 7.4. A pH of 8 caused a decrease in CBF to 15 Hz (2). CBF returned towards normal following re-perfusion with medium 199, pH 7.4. The co-efficient of variation for brain CBF was 5.5% (pH 7.4). Conclusion: Changes in pH have a profound effect on brain ciliary beat frequency. We assume that this effect is directly related to change in intracellular pH. [ll
Worthington,F. (1963): Science, 139, 221-224.