• Mary Ellen McCann, Julianne Bacsik, Andrew Davidson, Susan Auble, Lorna Sullivan, and Peter Laussen.
• Department of Anesthesia, Children's Hospital, Boston and Harvard Medical School, MA 02115, USA. mccann@tch.harvard.edu
• Paediatr Anaesth. 2002 Jul 1;12(6):519-25.

BackgroundBispectral index (BIS) is a signal processing device that potentially is a pharmacodynamic measure of the effects of anaesthesia on the central nervous system.MethodsIn this prospective blinded study, we investigated the pharmacodynamic relationship between BIS, haemodynamic changes during anaesthesia and endtidal nonsteady state concentrations of sevoflurane in 30 children, mean age 3.3 +/- 1.1 years, who were undergoing tonsillectomy and adenoidectomy. A standardized anaesthetic technique was used and included induction and maintenance with sevoflurane, nitrous oxide and oxygen. BIS, heart rate, mean arterial pressure (MAP) and endtidal sevoflurane (ETsevo) concentrations were continuously recorded and specifically noted at the time of intubation, placement of Dingman gag, incision of adenoid, adenoid out, incision of tonsil, tonsil one out, tonsil two out, last agent off, first spontaneous movement, first eye opening and extubation. The anaesthetist was blinded to BIS throughout the procedure.ResultsUsing a Spearman correlation analysis, there was significant negative correlation between BIS and ETsevo concentrations (r=- 0.888, P < 0.01) and a pharmacodynamic relationship with EC50 (ETsevo at which BIS=50) of 1.48% (95% confidence interval 0.84-2.11). There was a weak negative correlation between sevoflurane and MAP (r=- 0.391, P < 0.01) but no significant correlation between sevoflurane and heart rate.ConclusionsIn preschool children undergoing sevoflurane anaesthesia for tonsillectomy and adenoidectomy, endtidal sevoflurane concentrations are more closely correlated with BIS than with MAP or heart rate.

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