Abstract
The effects of anaesthetic agents, per se, on the asphyxiated foetus are difficult to quantitate clinically. Anaesthesia is often necessary in foetal distress, however, to effect a rapid delivery. To investigate the effect of general anaesthetic agents commonly used for Caesarean section we administered these agents to 18 chronically prepared pregnant ewes with asphyxiated foetuses in utero. The foetuses were asphyxiated by partial occlusion of the umbilical cord until foetal arterial pH had decreased from 7.30 to a range of 7.08–7.13. The animals were divided into three groups: Group A which received no anaesthesia and thus served as a control, Group B which received thiopentone (3 mg·kg-1) intravenously followed by 50 per cent nitrous oxide and 0.5 per cent halothane in oxygen for 15 minutes, and Group C which received thiopentone (3 mg·kg-1 ) followed by one per cent halothane in oxygen for 15 minutes. Foetal cerebral, myocardial, and renal blood flows were measured by injection of radioactive microspheres after production of asphyxia and after 5 and 15 minutes of anaesthesia. General anaesthesia in both groups B and C abolished the hypertension and bradycardia produced by foetal asphyxia secondary to umbilical cord occlusion. There were no significant differences between Groups B and C in foetal pH, PCO2, or PO2. Two foetuses in the nitrous oxide group died after ten minutes of anaesthesia, but the aetiology of the sudden demise is unclear. We conclude that general anaesthesia abolishes the foetal response to umbilical cord occlusion and does not improve foetal oxygenation or acid-base status.
Résumé
Les effets des agents anesthésiques comme tels sur le fcetus asphyxié sont difficiles à quantifier cliniquement. L’anesthésie est souvent nécessaire lors de la détresse fœtale afin de procéder à un accouchement rapide. Afin d’investiguer les effets des agents anesthésiques utilisés fréquemment lors des césariennes, on a administré ces agents à 18 brebis gravides. Les fœtus de ces brebis ont été préparés chroniquement de façon à les asphyxier in utero. Ces foetus ont été asphyxiés par une occlusion partielle de la corde ombilicale jusqu’à ce que le pH artériel fœtal diminue de 7.30 à des valeurs s’éendant de 7.08 à 7.13. Ces brebis ont été divisées en trois groupes: groupe A n’a reçu aucune anesthésie et ainsi a servi comme groupe témoín. Groupe B a reçu du thiopentone (3 mg·kg-1) en injection intraveineuse suivi de 50 pour cent de protoxyde d’azote et 0.5 pour cent halothane dans l’oxygène pour 15 minutes, et group C a reçu du thiopentone (3mg·kg-1) suivi de un pour cent d’halothane dans I’oxygène pour 15 minutes. Les flots sanguins cérébral, myocardique et rénal chez les fœtus ont été mesurés par injection de microsphères radioactives après production de l’asphyxie 5 et 15 minutes après l’anesthésie. L’anesthésie générale dans les deux groupes B et C a enrayé l’hypertension et la bradycardie produite par l’asphyxie fœtale secondaire à l’occlusion de la corde ombilicale. Les changements les plus marqués sont survenus dans le groupe B qui a reçu du protoxyde d’azote. Deux des six fœtus de ce groupe sont morts après dix minutes de l’anesthésie. Il n’y avait cependant aucune différence significative pour le pH, la PCO2 et la PO2 chez les survivants de ce groupe et le groupe tiémoín. De ces résultats on arrive à la conclusion que le protoxyde d’azote est inapproprié pour l’anesthésie dans des situations de détresse fœtale sévère.
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Swartz, J., Cummings, M., Pucci, W. et al. The effects of general anaesthesia on the asphyxiated foetal lamb in utero. Can Anaesth Soc J 32, 577–582 (1985). https://doi.org/10.1007/BF03011402
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DOI: https://doi.org/10.1007/BF03011402