Comparative Evaluation of the Cerebral State Index Tm and Bispectral Index Tm Monitoring during Propofol -remifentanil Anesthesia for Open Heart Surgery

Objective: The Cerebral State index (CSI) is a new index based on electroencephalogram to monitor depth of anesthesia. Transferring guidelines for titration of the Bispectral index (BIS) to the CSI depends on their compatibility. We compared the relationship between BIS and CSI values during propofol-remifentanil anesthesia. Methods: Forty one adult patients about to have open heart surgeries were enrolled. The skin was prepped and electrodes of both monitors were applied according to the manufacturers’ recommendations. The anesthesia was induced by midazolam, propofol, remifentanil and pancuronium and maintained by propofol and remifentanil and 50% nitrous oxide in oxygen. The BIS and CSI values were recorded in 37 pre-determined milestones during the operation and the anesthetic drugs were adjusted according to clinical signs of light anesthesia regardless of the CSI or BIS values. Results: The BIS and CSI values decreased progressively from pre induction values of 93.15 (55-100) and 88.86 (52-100) to post induction values of 38.72(16-71) and 40.27(5-69), respectively. These values showed good linear correlation during laryngoscopy, before and after surgical incision and during CPB; R=0.695 with determination coefficient of 0.483. Conclusions: We found a good correlation between BIS and CSI values. Our results might serve as a blue print for a rational “translation” of BIS into CSI values.