DOI: 10.1093/bja/aeh182 Advance Access publication June 11, 2004 Comparability of NarcotrendTM index and bispectral index during propofol anaesthesia

version 4.0), from 100 (awake) to 0, is a new index based on electroencephalogram pattern recognition. Transferring guidelines for titrating the Bispectral IndexTM (BIS, Aspect Medical Systems, USA, version XP) to the NCT index depends on their comparability. We compared the relationship between BIS and NCT values during propofol anaesthesia. Methods. Eighteen adult patients about to have radical prostatectomy were investigated. An epidural catheter was placed in the lumbar space and electrodes for BIS and NCT were applied as recommended by the manufacturers. After i.v. fentanyl 0.1 mg, anaesthesia was induced with a propofol infusion. After intubation, patients received bupivacaine 0.5 % 15 ml via the epidural catheter. Forty-five minutes after induction, the propofol concentration was increased to sub-stantial burst suppression pattern and then decreased. This was done twice in each patient, and BIS andNarcotrend values were recorded at intervals of 5 s. The efficacy of NCT and BIS in predicting consciousness vs unconsciousness was evaluated using the prediction probability (PK). Results. We collected 38 629 artefact-free data pairs of BIS and NCT values from the respective 5-s epochs. Because of artefacts, another 5008 epochs had been excluded from data analysis (3855epochs for theNCTindexalone, 245epochs for theBIS aloneand908epochs forboth indices)