The correlation of the Narcotrend Index with endtidal sevoflurane concentrations and hemodynamic parameters in children

Background: The Narcotrend Index (NI) of anesthetic depth is potentially a pharmacodynamic measure of the effects of sevoflurane on the brain. Methods: In this prospective observational study of 30 pediatric surgical patients (1-11 years), we investigated the correlation between nonsteady-state endtidal sevoflurane (eT(Sevo)), NI, mean arterial pressure (MAP), and heart rate (HR). The performance of the Narcotrend for differentiation between consciousness and unconsciousness was evaluated using prediction probability (P-K). Results: Spearman correlation analysis showed significant correlations (P < 0.01) between eT(Sevo) and NI (r = -0.85) and MAP (r = -0.43). P-K-values for differentiation between consciousness and unconsciousness were 1.0 for NI and < 0.85 for MAP and HR. During the surgical procedure, NI-values showed a constant rise with each 0.5% step of lowering eT(Sevo) (P < 0.03), whereas MAP remained unaltered and HR showed a constant decline (P < 0.03), except between 1.5 and 1%. Conclusions: In children, nonsteady-state eT(Sevo) concentrations are more closely related with NI than with MAP or HR. In this study, only NI reliably differentiated consciousness from unconsciousness.