Abstract
Atropine-induced heart rate (HR) changes were studied in 19 patients (ASA physical status I) during anaesthesia maintained predominantly with propofol-N2O or thiopentone-enflurane-N2O. Ten patients (Group A) received midazolam (0.07 mg · kg−1), fentanyl (1 μg · kg−1), propofol (2 mg · kg−1) and succinylcholine (1 mg · kg−1). Following tracheal intubation, anaesthesia was maintained with propofol (6 mg · kg−1 · hr−1), N2O (67 per cent) and O2 (33 per cent). In nine patients (Group B) thiopentone (4 mg · kg−1) was substituted for propofol and anaesthesia maintained with N2O (67 per cent) O2 (33 per cent), and enflurane (0.5 per cent inspired concentration). The study was non-randomised because Group B patients were only included if HR before administration of atropine < 90 beats · min−1. IPPV was performed in all patients using a Manley ventilator (minute vol. 85 ml · kg−1; tidal vol. 7 ml · kg−1). Ten minutes after tracheal intubation, incremental doses of atropine (equivalent cumulative doses: 1.8, 3.6, 7.2, 14.4, 28.8 μg · kg−1) were administered at two-minute intervals and HR responses calculated during the last 45 sec of each intervening period. No differences were observed between the groups following 1.8 and 3.6 μg · kg−1 atropine, but propofol-N2O anaesthesia was associated with reduced responses (P < 0.01) following 7.2, 14.4 and 28.8 μg · kg−1 atropine. These results suggest that there is a predominance of parasympathetic influences during propofol-N2O anaesthesia compared with thiopentone-enflurane-N2O anaesthesia.
Résumé
Les changements de la fréquence cardiaque induits par l’atropine ont éte étudiés chez 19 patients (Classe ASA I) durant l’anesthésie maintenu surtout avec du propofol-N2O ou thiopentone-enflurane-N2O. Dix patients (Groupe A) ont reçu du midazolam (0.07 mg · kg−1), fentanyl (1 μg · kg−1), propofol (2 mg · kg−1) et succinylcholine (1 mg · kg−1). Après l’intubation, l’anesthésie a été maintenue avec du propofol (6 mg · kg−1 · hr−1), N2O (67 pour cent), O2 (33 pour cent). Chez neuf patients (Groupe B) du thiopentone (4 mg · kg−1) a été substitué pour du propofol et l’anesthésie fut maintenue avec du N2O (67 pour cent), O2 (33 pour cent) et enflurane (0,5 pour cent fraction inspirée). Cette étude n’était pas randomisée car les patients du groupe B ont été inclus seulement si la fréquence cardiaque avant l’administration de l’atropine était <90 batt · min−1. La ventilation fut assurée par un ventilateur Manley chez tous les patients (vol. minute 85 ml · kg−1; volume courant 7 ml · kg−1). Dix minutes après l’intubation, des doses croissantes d’atropine (doses cumulatives: 1,8, 3,6, 7,2, 14,4, 28,8 μg · kg−1) ont été administrées à deux minutes d’intervalle et les réponses de la fréquence cardiaque furent calculées durant les dernières 45 secondes après chaque période d’intervention. Aucune différenc e fut obserée entre les groupes après 1,8 et 3,6 μg · kg−1 d’atropine mais l’anesthésie au propofol-N2O était associée avec une réponse réduite (P < 0.01) aprés 7,2, 14,4 et 28,8 μg · kg−1 d’atropine. Ces résultats suggèrent qu’il y a une prédominance de l’influence du système parasympathique lors de l’anesthésie au propofol-N2O comparativement à l’anesthésie au thiopentone-enflurane-N2O.
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This study was supported in part by ICI Pharmaceuticals (UK).
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Cross, G., Gaylard, D. & Lim, M. Atropine-induced heart rate changes: a comparison between midazolam-fentanyl-propofol-N2O and midazolam-fentanyl-thiopentone-enflurane-N2O anaesthesia. Can J Anaesth 37, 416–419 (1990). https://doi.org/10.1007/BF03005617
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DOI: https://doi.org/10.1007/BF03005617