BJA Advance Access originally published online on October 24, 2007
British Journal of Anaesthesia 2007 99(6):858-863; doi:10.1093/bja/aem300
Differential electroencephalographic response to tracheal intubation between young and elderly during isoflurane– and sevoflurane–nitrous oxide anaesthesia
1 Department of Anesthesiology and Intensive Care Medicine
2 Department of Public Health, Graduate School of Medicine, Osaka City University, 1-5-7 Asahimachi, Abeno-ku, Osaka 545-8586, Japan
* Corresponding author. E-mail: odayou{at}msic.med.osaka-cu.ac.jp
Background: Age-associated differences in the electroencephalographic (EEG) response to noxious stimuli with the presence of nitrous oxide (N2O) are unknown. We compared the EEG response with tracheal intubation between young and elderly.
Methods: Sixty young (<40 yr) and elderly (>70 yr) patients were randomly allocated to one of the four groups. Anaesthesia was induced with 66% N2O and isoflurane in oxygen (Young-isoflurane and Elderly-isoflurane groups) or 66% N2O and sevoflurane in oxygen (Young-sevoflurane and Elderly-sevoflurane groups). Inhaled isoflurane and sevoflurane concentrations were gradually increased and the end-tidal concentrations were maintained at 1.1% and 1.7%, respectively. Tracheal intubation was performed 12 min after induction of anaesthesia.
Results: There were significant differences in the overall changes in bispectral index (BIS) and 95% spectral edge frequency (SEF95) between young and elderly (P<0.001 for both), but not between patients receiving isoflurane and sevoflurane (P=0.4 and 0.3, respectively). Both BIS and SEF95 were significantly decreased after tracheal intubation in Young-isoflurane and Young-sevoflurane groups (P<0.05 for all). In sharp contrast, BIS and SEF95 remained unchanged in Elderly-isoflurane and Elderly-sevoflurane groups (P>0.7 for all). These results suggest that both BIS and SEF95 significantly decreased, despite the presence of increased sympathetic activity after tracheal intubation in young patients.
Conclusions: A significant difference was detected in EEG response to tracheal intubation between young and elderly. BIS does not reflect the depth of anaesthesia after tracheal intubation during anaesthesia with isoflurane or sevoflurane with 66% of N2O in young patients.
Keywords: anaesthetics volatile, isoflurane; anaesthetics volatiles sevoflurane; intubation; monitoring, bispectral index; monitoring, electroencephalogram