Performance of the Cerebral State Index During Increasing Levels of Propofol Anesthesia: A Comparison with the Bispectral Index

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Abstract

BACKGROUND:

The cerebral state monitor is a new device to measure depth of anesthesia. In this study we compared the cerebral state monitor with the bispectral index (BIS) monitor during propofol anesthesia.

METHODS:

Fifteen healthy patients received a continuous infusion of propofol (300 mL/h). The cerebral state index (CSI) and the BIS values were recorded until burst suppression ratio ≥60%. Baseline variability, prediction probability, and agreement analysis between indices were evaluated. Clinical markers of loss of consciousness were also assessed.

RESULTS:

Mean awake BIS and CSI values were 95.6 and 91.6, respectively (P = 0.01). BIS and CSI prediction probability values (mean ± sd) were estimated to be 0.87 ± 0.08 and 0.86 ± 0.08, respectively (NS). The CSI tended to stabilize at values of 60–40 when estimated propofol concentrations at the effect site increased from 5 to 8 μg/mL. The BIS stabilized at values of 40–20 when the propofol concentrations at the effect site increased from 7 to 10 μg/mL. The mean BIS-CSI difference was −7.4 with 95% limits of agreement of 22.2 and −36.9. The BIS and CSI correlation with the burst suppression ratio was −0.60 and −0.97, respectively (P < 0.01). Predicted BIS and CSI values for loss of eyelash reflex in 50% and 95% of the patients were different (P < 0.05).

CONCLUSION:

The overall performance of both monitors during propofol induction was similar. However, the different dynamic profiles of these monitors indicate that BIS may be a more useful index for evaluating intermediate anesthetic levels, whereas CSI may be better for evaluating deeper anesthetic levels.

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