Cerebral state index versus bispectral index during propofol-fentanyl-nitrous oxide anesthesia.

Purpose: The aim of this study was to compare the cerebral state index (CSI) and bispectral index (BIS) during propofol-fentanyl-nitrous oxide anesthesia.

Methods: Thirty patients scheduled for abdominal surgery, with a mean age of 30-70 years, were enrolled. Anesthesia was induced with propofol and fentanyl and was maintained with propofol, fentanyl, epidural mepivacaine, and nitrous oxide in oxygen. During surgery, the propofol infusion rate was adjusted to try to keep BIS at 40 + or - 3 for 10 min and then decreased to keep the BIS at 60 + or - 3 for 10 min.

Results: The BIS had a larger value for the time between switching on the apparatus and starting to measure at a signal quality index >75%. The recovery time from disturbance by an electric cautery event was 41 + or - 14 s for the BIS and 3 + or - 1 s for the CSI (P < 0.05). The absolute values of the BIS and CSI were not significantly different and they showed a good correlation. The bias (mean of the differences, BIS - CSI) was negative at all measurement points, but the limits of agreement and percentage error were small.

Conclusions: The absolute values of the BIS and CSI were not significantly different during propofol-fentanyl-nitrous oxide anesthesia. The start of the measurement was faster with the CSI than with the BIS after switch-on, and measurement was less disturbed by electric cautery with the CSI.