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Preservation of electrocortical brain activity during hypoxemia in preterm lambs

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Abstract

Adequate cerebral perfusion is necessary to preserve cerebral O2 supply in order to maintain brain cell function. Our aim was to assess the influence of gestational age on the response of cerebral hemodynamics to hypoxemia and to determine thresholds of cerebral O2 supply for preservation of brain cell function in preterm born lambs. Lambs were delivered by hysterotomy at 141 (n=5), 134 (n=5) or 127 (n=7) days of gestation. Decreases in arterial oxygen content (CaO2) were induced by stepwise reduction of the fraction of O2 in inspired air (FiO2). Mean arterial blood pressure (MABP), carotid artery blood flow (Qcar), and electrocortical brain activity as a measure of brain cell function, were continuously recorded. Cerebral arterial blood gases were analyzed at the end of each hypoxemic level to calculate CaO2 and cerebral O2 supply. In contrast to 141-day lambs, MABP could not be maintained in 134-day and 127-day lambs at levels of severe hypoxemia. Increases in Qcar were observed at levels of moderate hypoxemia in all gestational age-groups. Albeit Qcar increased further at levels of severe hypoxemia in the 141-day lambs, Qcar declined under these conditions in the 134-day and 127-day lambs. The threshold of cerebral O2 supply for the preservation of brain cell function was however similar in all gestational age-groups (1.7 ml/min). It is concluded that the ability to maintain cerebral function during hypoxemia depends upon the ability to preserve cerebral O2 supply by means of cerebral hemodynamic compensatory mechanisms, which are not fully matured until 96% of gestation.

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Acknowledgements

We thank Alex Hanssen and Theo Arts, Central Animal Laboratory Nijmegen, for their advice and surgical assistance.

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Authors and Affiliations

  1. Division of Neonatology, Department of Pediatrics, 435, University Medical Center Nijmegen, PO Box 9101, 6500 HB, Nijmegen, The Netherlands

    Sandra Van Os, Djien Liem & Margot Van de Bor

  2. Clinical Physics, Department of Pediatrics, University Medical Center Nijmegen, Nijmegen, The Netherlands

    John Klaessens & Jeroen Hopman

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  1. Sandra Van Os
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  2. John Klaessens
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  3. Jeroen Hopman
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  4. Djien Liem
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  5. Margot Van de Bor
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Correspondence to Sandra Van Os.

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Van Os, S., Klaessens, J., Hopman, J. et al. Preservation of electrocortical brain activity during hypoxemia in preterm lambs. Exp Brain Res 151, 54–59 (2003). https://doi.org/10.1007/s00221-003-1469-6

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  • DOI: https://doi.org/10.1007/s00221-003-1469-6

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