[Electroencephalographic change during induction of high-dose fentanyl anesthesia--evaluation by LIFESCAN EEG monitor].

The relation between the patient's consciousness level and the change in electroencephalographic (EEG) activity during general anesthesia has not been well understood. In the present study, we evaluated such relationship quantitatively during the induction of high-dose fentanyl anesthesia in adult open-heart cases. There are significant increase in delta activity and significant decrease in alpha and beta activity in response to the induction of anesthesia. The loss of consciousness coincided with the sharp reduction in delta ratio and edge frequency (80%). Such reduction was more prominent in delta ratio than in edge frequency. These findings suggest that delta ratio could indicate the consciousness level during the induction of high-dose fentanyl anesthesia. Further study is needed to clarify the EEG response during inhalation and intravenous anesthesia in relation to EEG activity.