• P S Sebel, S M Bowles, V Saini, and N Chamoun.
• Department of Anesthesiology, Emory University School of Medicine, Crawford W. Long Hospital, Atlanta, GA, USA.
• J Clin Monit. 1995 Mar 1;11(2):83-91.

ObjectiveThe 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.MethodsA 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.ResultsFor 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.ConclusionsWhen 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.

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