Introduction: Bispectral index (BIS) is a promising method for monitoring a
naesthetic depth in humans. Inhalational and intravenous anaesthetics produ
ce dose-dependent effects on electroencephalogram-derived parameters, such
as bispectral index (BIS). Significant correlations between decrease of BIS
values in humans and end-tidal concentrations of volatile anaesthetics hal
othane, isoflurane, desflurane and sevoflurane and plasma propofol concentr
ations have been reported in several investigations. We have investigated t
he effect of xenon anaesthesia on bispectral index (BIS) in pigs.
Materials and Methods: BIS index was measured under total intravenous, xeno
n and halothane anaesthesia: in 8 pigs. Each animal received 1 MAC halothan
e before or after xenon anaesthesia in randomized cross over design to elim
inate systemic errors. Between xenon and halothane anaesthesia total intrav
enous anaesthesia was applied to eliminate the effects of the anaesthetic g
as first applied. Surgical stimuli were not present during xenon and haloth
ane anaesthesia, surgical preparations were completed in TIVA. BIS levels m
easured during preparation phase were used as reference values to assure ad
equate level of anaesthesia. BIS was measured using an BIS EEG monitor (Asp
ect A 2000, Aspect Medical Systems Inc., Natick, MA, USA).
Results: We found no significant difference between BIS scores in anaesthet
ized pigs with I MAC of halothane or 70% xenon or in total intravenous anae
sthesia. In addition, we found no significant difference in BIS during the
whole anaesthesia with halothane or xenon. BIS levels during halothane and
xenon anaesthesia were comparable to those measured under TIVA and surgical
preparation. BIS values remained unchanged during xenon anaesthesis as com
pared with TIVA and halothane anaesthesia.
Conclusion: As a conclusion the BIS EEG is a very promising tool for measur
ing depth of xenon, halothane and total intravenous anaesthesia also in ani
mals.