Abstract
In a previous study, we examined the effects of halothane on the normal foetal lamb in utero. The most significant finding was a 33 per cent fall infoeial mean arterial blood pressure (MABP). Cardiac output and placental blood flow were not affected. To determine if the asphyxiated foetus would respond similarly, the following study was performed. Seven pregnant ewes were surgically prepared two days prior to study with maternal and foetal indwelling arterial and venous cannulas. An inflatable occlusion loop was secured around the umbilical cord.
On the day of study, a tracheostomy was performed on each ewe. Microspheres were injected into the foetal circulation during the control period. The occlusion loop was inflated to produce foetal asphyxia and microspheres were again injected. The ewe was then anesthetized with halothane; and after 15 minutes, microspheres were injected into the asphyxiated foetus and halothane levels were measured.
The asphyxiated foetuses showed a significant rise in MABP, fall in heart rate and fail in cardiac output from control. Blood flow to the brain was significantly increased and flow to the placenta and gut decreased. Exposure of the asphyxiated foetus to haiothane resulted in a fall of MABP to control but no significant change in cardiac output or brain blood flow. The mean haltithane level in the foetus was 46.0 mg.l-1 or 0.32 vol%. Exposure of the asphyxiated foetus to halothane for 15 minutes does not produce significant further deterioration of the foetal lamb in utero.
Résumé
Lors d’une étude antérieure, les auteurs avaient étudié les effets de l’halothane sur le fœtus de brebis in utero. La constatation la plus significative a été une chute de 33 pour cent de la pression artérielle moyenne. Le débit cardiaque et le débit placentaire n’ont pas été affectés. Pour déterminer si le fœtus asphyxié répondrait de façon similaire, l’étude suivante a été réalisée. Sept brebis gravides ont subi une préparation chirurgicale comprenant l’insertion de sondes maternelles et fœtales à demeure tant du côté artériel que veineux. Un lacet insufflable a été installé autour du cordon ombilical.
Le jour de l’étude on a trachéotomisé chacune des brebis. On a ensuite injecté des microsphères dans la circulation fœtale pendant la période de contrôle. Le lacet fut insufflé pour produire l’asphyxie fœtale et des microsphères ont été réinjectées. La brebis fut ensuite anesthésiée à l’haiothane; après 15 minutes, on a injecté de nouveau des microsphères dans la circulation du fœtus asphyxié et on a mesuré la concentration de i’halothane dans le sang.
Les fœtus asphyxiés ont montré une élévation significative de la pression artérielle majeure, une chute de la fréquence et du débit cardiaque comparativement aux contrôles. Le débit sanguin cérébral a été augmenté de façon significative et les débits sanguins placentaire et intestinal diminués. L’exposition à l’haiothane des fœtus asphyxiés a causé une baisse de la pression artérielle moyenne comparativement aux contrôles mais pas de changement significatif du débit cardiaque et du débit cérébral. La concentration sanguine de l’haiothane dans le fœtus a été de 46.0 mg.l-1 ou 0.32 vol. pour cent.
L’exposition du fœtus en étal d’asphyxie pendant 15 minutes ne produit pas de façon significative une détérioration plus marquée du fœtus de la brebis in utero.
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Supported in part by the St. Boniface Research Foundation, Grant Number: RF79-3 and the Medical Research Council of Canada, Grant Number MA-6735.
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Yarnell, R., Biehl, D.R., Tweed, W.A. et al. The effect of halothane anaesthesia on the asphyxiated foetal lambin utero . Can Anaesth Soc J 30, 474–479 (1983). https://doi.org/10.1007/BF03007080
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DOI: https://doi.org/10.1007/BF03007080