EEG bispectrum predicts movement during thiopental/isoflurane anesthesia.
OBJECTIVE
The objective of our study was to test the efficacy of the bispectral index (BIS) compared with spectral edge frequency (SEF), relative delta power, median frequency, and a combined univariate power spectral derivative in predicting movement to incision during isoflurane/oxygen anesthesia.


METHODS
A total of 42 consenting patients were assigned to 3 groups, isoflurane 0.75, 1.0, and 1.25 minimal alveolar concentration (MAC). Anesthesia was induced with thiopental and maintained with the appropriate end-tidal concentration of isoflurane. The electroencephalogram (EEG) was recorded using a microcomputer system, and data were analyzed off-line. The EEG during the 2 min before incision was analyzed. Following skin incision, each patient was carefully observed for 60 sec to detect occurrence of purposeful movement.


RESULTS
For all groups combined, there was a statistically significant difference for BIS (p < 0.0001) and also for relative delta power (p < 0.016) between movers and nonmovers. There was a statistically significant difference between movers and nonmovers at 1.25 MAC isoflurane for BIS (p < 0.01). There were no other significant differences for any other EEG variable at any concentration of isoflurane. No EEG variable showed a relationship to isoflurane concentration.


CONCLUSIONS
When bispectral analysis of the EEG was used to develop a retrospectively determined index, there was an association of the index with movement. Thus, it may be a useful predictor of whether patients will move in response to skin incision during anesthesia with isoflurane/oxygen.
Sebel
P S
PS
Department of Anesthesiology, Emory University School of Medicine, Crawford W. Long Hospital, Atlanta, GA, USA.
Bowles
S M
SM
Saini
V
V
Chamoun
N
N
D000328:Adult; D000768:Anesthesia, General; D000771:Anesthesia, Intravenous; D004569:Electroencephalography / Q000379:methods*; D005583:Fourier Analysis; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage; D016343:Monitoring, Intraoperative / Q000379:methods*; D009068:Movement; D012815:Signal Processing, Computer-Assisted; D013874:Thiopental
D007530:Isoflurane; D013874:Thiopental