Changes in EEG and Bispectral Index in Children during Inhalation Anesthesia

Abstract

Objective: to estimate bispectral (BIS) index and electroencephalographic (EEG) changes during anesthesia with halothane, sevoflurane, and a successive combination of sevoflurane and isoflurane, by taking into account age. Subjects and methods. Sixty children aged 3 to 17 years, who had undergone elective surgery, were randomized to 3 groups of 20 children each: 1) halothane anesthesia; 2) sevoflurane anesthesia; and 3) a successive combination of sevoflurane and isoflurane. A 1:1 oxygen-nitrous oxide mixture was used for anesthesia in all the groups. EEG (using a 6-channel computer-assisted encephalograph) and bispectral index (XP version) was continuously recorded throughout the anesthesia, except the transition to isoflurane in Group 3. Results. In the halothane group, EEG displayed a gradual reduction in basic rhythm, an increase in slow activity with the rhythm being recovered on emergence. The BIS index changed from 96—99 to 19—36 with a spike of up to 80—87 on emergence. In Groups 2 and 3 where the induction of anesthesia used sevoflurane, EEG recorded a pointed а-rhythm, increased amplitude, and rhythm synchronization. The BIS value changed from 96—99 to 19—37. In Group 2, it was 30 to 40 on anesthesia maintenance and up to 82—87 on emergence. In Group 3, the isofluorane anesthesia stage changed EEC patterns towards rhythm synchronization and gave rise to slow fluctuations in all leads. The BIS index was 30—39 on anesthesia maintenance and 80—86 on emergence. Conclusion. EEC and BIS index monitoring values corresponded to the clinical course and depth of anesthesia. The comparison of the clinical data of the course of anesthesia and the values of EEG and BIS monitoring could lead to the conclusion that BIS technology might be of informative value in children. Key words: inhalation anesthesia, electroencephalography, BIS monitoring, isoflurane, sevoflurane, halothane.