ABSTRACT
The assessment of patient brain state during surgery has long been an objective of research in the
field of automated electroencephalogram (EEG), since EEG signals contain a wealth of information
about brain functions, there are many approaches to analyzing EEG signals with spectral
techniques. In this paper the bispectral analysis was applied to EEG signals obtained from patients
under general anesthesia by using BSA software (bispectrum analyzer software version 3.31B) [1-
4]. The bispectral values (BIS) was normalized to 100 while awake and decreasing gradually to a
level between 0 and20 as the patient was anaesthetized. The clinical signs such as heart rate (HR)
and blood pressure (BP) of the level of anesthesia were observed simultaneously. Conclusion, the
bispectral analysis of EEG signals obtained from patients under general anesthesia gives accurate
index to measure depth of anesthesia.