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.