Abstract
Cardiac electrophysiological variables during thoracic epidural lidocaine (TEL) were compared with those during continuous intravenous lidocaine (IVL) infusion in 14 mongrel dogs anaesthetized with enflurane in order to investigate the combined effects of thoracic epidural anaesthesia (TEA) and enflurane anaesthesia on intracardiac conduction. Thoracic epidural lidocaine suppressed intracardiac conduction. Sinus cycle length (SCL) and Atrium-His (AH) interval increased by 9 and 11 per cent respectively (P < 0.05), 30 min after TEL. Intravenous lidocaine did not increase either SCL or AH. The functional refractory period of the atrioventricular node increased five per cent above the control value 15 min after TEL (P < 0.05), while it was unchanged in the IVL group. The mean plasma concentrations of lidocaine ranged from 0.48 ± 0.07 to 1.00 ± 0.14 μg · ml−1 in the TEL group and from 0.98 ± 0.13) to 1.21 ± 0.15 μg · ml−1 in the IVL group. There were no significant differences in plasma concentrations of lidocaine in both groups during the observation period. Therefore, it is concluded that the depressant effects of TEA on intracardiac conduction were caused by blocking of the sympathetic efferent activity. Caution may be advised in administering TEA when cardiac conduction is already compromised.
Résumé
Les variables electrophysiologiques cardiaques lors d’une anesthésie thoracique épidurale avec la lidocaïne (TEL) ont été comparées avec celles obtenues lors d’une perfusion intraveineuse de lidocaine (IVL) chez 14 chiens bâtards anesthésiés avec l’enflurane afin d’investiguer les effets combinés de l’anesthésie épidurale thoracique (TEA) et l’anesthésie à l’enflurane sur la conduction intracardiaque. La lidocaine administrée par voie épidurale thoracique a supprimé la conduction intracardiaque. La longueur du cycle sinusal (SCL) et l’intervalle de His auriculaire (AH) ont augmenté de 9 et 11 pour cent, respectivement (P < 0,05), 30 minutes après TEL. La perfusion intraveineuse de lidocaïne n’a augmenté ni le SCL ni le AH. La période réfractaire fonctionnelle du nœud atrioventriculaire augmenta de cinq pour cent de la valeur de contrôle 15 minutes après TEL (P < 0,05) alors qu’elle fut inchangée dans le groupe IVL. Les concentrations plasmatiques moyennes de lidocaïne variaient entre 0,48 ± 0,07 à 1,00 ± 0,14 μg · ml−1 pour le groupe TEL et de 0,98 ± 0,13 à 1,21 ± 0,15 μg · ml−1 pour le groupe IVL. Il n’y avail aucune différence significative dans les concentrations plasmatiques de lidocaïne dans les deux groupes pendant la période de surveillance. Ainsi on conclut que les effets dépresseurs de la TEA sur la conduction intracardiaque sont causés par le blocage de l’activité efférente sympathique. La prudence est conseillée lors de l’administration de la TEA quand la conduction cardiaque est déjà compromise.
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This study was supported in part by a Research Grant from the Ministry of Education, Science and Culture, 1989, Japan.
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Sato, K., Yamamura, T., Murakami, F. et al. Thoracic epidural anaesthesia combined with enflurane anaesthesia reduces atrioventricular conduction in dogs. Can J Anaesth 37, 813–818 (1990). https://doi.org/10.1007/BF03006544
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DOI: https://doi.org/10.1007/BF03006544