Failure of Two Commercial Indexes and Spectral Par

Authors: Sascha Kreuer Jörgen Bruhn Richard Ellerkmann Stephan Ziegeler Darius Kubulus Wolfram Wilhelm

Publish Date: 2008/03/27

Volume: 22, Issue: 2, Pages: 149-158

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Abstract

We compared two PK/PD models one with and one without a plateau effect Bispectral BIS Aspect Medical Systems Natick MA version XP and Narcotrend™ NCT MonitorTechnik Bad Bramstedt Germany Version 40 indices were used as an electroencephalographic measure of desflurane drug effectWith IRB approval and informed consent we investigated 20 adult patients scheduled for radical prostatectomy At least 45 minutes after induction of general anaesthesia endtidal concentrations of desflurane was varied between 3 and 10 vol To evaluate the relationship between concentrations and EEG indices two different pharmacodynamic models were applied A conventional model based on a single sigmoidal curve and a novel model based on two sigmoidal curves for BIS and NCT values with and without burst suppression The parameters of the models␣were estimated by NONMEM V GloboMax Hanover USA by minimizing log likelihood Statistical significance between the two models was calculated by the likelihood ratio testThe maximum endtidal desflurane concentration during the two concentrations ramps was 100 ± 14 vol The mean BIS and NCT values decreased significantly but slightly with increasing endtidal desflurane concentrations between 4 and 8 vol Therefore a two sigmoidal curves PK/PD model including a plateau describes the effects of desflurane on BIS and Narcotrend better than a single sigmoidal curve model The difference between the log likelihood values of the new PK/PD model with two connected sigmoidal curves and the classical E max model with one sigmoidal curve is 634 P 0001 for the BIS monitor and 4089 P 0001 for the NCT

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