BJA Advance Access originally published online on August 23, 2006
British Journal of Anaesthesia 2006 97(5):676-680; doi:10.1093/bja/ael235
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Bispectral index is a topographically dependent variable in patients receiving propofol anaesthesia
1 Department of Anesthesiology, Erasmus Hospital, Free University of Brussels Brussels, Belgium
2 Division of Anesthesiology, Cantonal University Hospital Geneva, Switzerland
*Corresponding author: Department of Anesthesiology, Erasmus Hospital, Lennik drive 808, B-1070 Brussels, Belgium. E-mail: ppandin{at}ulb.ac.be
Background. As very strong agreement has been reported between bispectral index (BIS) values measured from the occipital and frontal skull areas, we compared BIS values measured from central and parietal areas with those from frontal area to investigate whether BIS is really a topographically dependent or topographically independent variable.
Methods. Twenty patients, ASA III, non-obese, aged 1862 yr and with no neurological disorders were enrolled. Based on the 1020 international landmarks, five silver dome electrodes were positioned: F7, C3, P7, Cz (common reference) and Fp1 (ground). Using frontal (F7Cz), central (C3Cz) and parietal (P7Cz) electrode montages, the corresponding BIS values were simultaneously recorded with an Aspect A-1000 monitor (software v3.12). The BIS values were recorded at the propofol concentration allowing laryngeal mask insertion, which was maintained during the 10 min data collection period in absence of additional external stimuli. Data were analysed using the KruskallWallis, Wilcoxon paired sign with Bonferroni correction, BlandAltman and linear correlation tests.
Results. At the predicted effect target propofol concentration 48 µg ml1, the 10 min mean BIS (median [minmax]) were 32 [2044], 46 [2868] and 58 [4172] for the frontal, central and parietal leads, respectively. Differences between these BIS recordings were statistically significant (P<0.0001, KruskallWallis; P<0.005, Wilcoxon paired sign test).
Conclusions. The present results provide evidence that BIS index is a topographically dependent variable in patients receiving propofol anaesthesia.