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Effect of Norepinephrine on Fetal Breathing in Sheep

Authors
  • Weintraub, Zalman
  • Alvaro, Ruben E.
  • Baier, R. John
  • Cates, Donald B.
  • Nowaczyk, Bogdan
  • Martino, Cecilia
  • Rigatto, Henrique
Type
Published Article
Journal
Neonatology
Publisher
S. Karger AG
Publication Date
Dec 19, 1997
Volume
73
Issue
1
Pages
60–68
Identifiers
DOI: 10.1159/000013961
Source
Karger
Keywords
License
Green
External links

Abstract

We tested the hypothesis that the surge of norepinephrine at birth is associated with the establishment of continuous breathing. Therefore, we studied whether the administration of norepinephrine could enhance fetal breathing during administration of oxygen, or 100% O2 plus cord occlusion, and if phenoxybenzamine would reverse these changes. Fetal sheep were instrumented in late gestation to measure electrocortical activity and diaphragmatic electromyography. These parameters and blood gases were measured before and during in utero administration of nitrogen, 100% O2, 100% O2 plus umbilical cord occlusion, and subsequently during umbilical reperfusion and recovery. Nine fetuses (14 experiments) received continuous norepinephrine (0.13 µg/kg/min) throughout the experiment while 9 other fetuses (18 experiments) underwent the same treatment without the hormonal infusion. We found that norepinephrine inhibited the breathing induced by 100% O2 plus cord occlusion, despite a significant increase in the duration of low-voltage electrocortical activity; phenoxybenzamine reverted these changes. The findings suggest that the surge of norepinephrine at birth is probably not the primary mechanism for establishment of continuous breathing.

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