Abstract
This study examined the relationship between the EEG (spectral edge frequency 90 — SEF90) and the occurrence of awareness defined for the purpose of this study as responsiveness to verbal commands. Fifty women undergoing general anaesthesia for elective Caesarean section were examined. Responsiveness to verbal commands was detected every minute in the period from the induction of anaesthesia to the delivery of the newborn using the Tunstall isolated forearm technique and correlated with the SEF90 value. The patients were assigned by a randomized code to receive either thiopentone (4 mg · kg− 1) or ketamine (1 mg · kg− 1)for induction of anaesthesia. Before the administration of succinylcholine a tourniquet was applied to the free arm, and inflated to 200 mmHg, to maintain motor function to one arm. The EEG recordings started five minutes before induction and were recorded throughout anaesthesia. The incidence of responsiveness to verbal commands was lower in the ketamine group (24%) where the average SEF90 was 12.0 ± 3 Hz, than in the thiopentone group (52%), where the average SEF90 was 18.09 ± 3 Hz(P = 0.01). The results suggest that SEF values of ≤ 8.6 Hz were sufficient to avoid responsiveness to verbal commands.
Résumé
Cette ’etude évalue la relation entre l’analyse de fréquence spectrale (spectral edge frequency 90 — SEF90) sur l’EEG et l’éveil intra-opératoire défini dans cette étude comme une réponse à un ordre verbal. L’étude inclut 50 parturientes opérées sous anesthésie générale pour une césarienne élective. Nous avons décelé les réponses à un ordre verbal a chaque minute en corrélation avec les valeurs du SEF90 pendant l’induction jusqu’à la naissance, en utilisant sur l’avant-bras la technique de Tunstall du garot isolant. Les patientes ont été réparties au hasard pour recevoir soit du thiopentone (4 mg · kg− 1) soit de la kétamine (1 mg · kg− 1)pour l’induction. Avant l’administration intraveineuse de succinylcholine, un garot isolant a été appliqué sur l’avant-bras et gonflé à 200 mmHg pour conserver l’activité motrice de l’avant-bras. L’EEG a éte enregistré 5 min avant l’induction et pendant l’anesthésie. L’incidence des réponses à des ordres verbaux a été inférieure dans le groupe kétamine (24%) (SEF90 moyenne 12,0 ± 3 Hz) comparativement au groupe thiopentone (52%) (SEF90 moyenne 18,09 ± 3). Ces résultats suggèrent qu’une valeur de SEF inférieure à 8.6 Hz suffit pour prévenir la réponse aux ordres verbaux.
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Gaitini, L., Vaida, S., Collins, G. et al. Awareness detection during Caesarean section under general anaesthesia using EEG spectrum analysis. Can J Anaesth 42, 377–381 (1995). https://doi.org/10.1007/BF03015480
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DOI: https://doi.org/10.1007/BF03015480