The correlation of the Narcotrend Index and classical electroencephalographic parameters with endtidal desflurane concentrations and hemodynamic parameters in different age groups.

BACKGROUND: The Narcotrend Index (NI) for assessment of depth of anesthesia by analysis of the electroencephalogram (EEG), is potentially a pharmacodynamic measure of the effects of desflurane on the brain.

METHODS: In this prospective study of 30 pediatric and adult patients (group 1: 3-6 years, n = 10; group 2: > 6 < 12 years; group 3: 12-40 years), undergoing ophthalmological surgery, we investigated the pharmacodynamic relationship between nonsteady state endtidal desflurane concentrations (eT(Des)), NI, classical EEG parameters (cEEG), heart rate (HR) and mean arterial pressure (MAP). The performance of the Narcotrend for differentiation between consciousness and unconsciousness was evaluated using prediction probability (P(K)).

RESULTS: Spearman correlation analysis showed significant negative correlations (P < 0.001) between eT(Des) and NI (group 1: r = -0.93, group 2: r = -0.86, group 3: r = -0.66). Correlations between eT(Des) and MAP or HR were either only weak negative (r < -0.5) or not significant. Desflurane EC(50) (eT(Des) with half maximal effect on NI) was 7.18% for group 1, 7.34% for group 2, and 4.15% for group 3 (P < 0.001 Vs groups 1 and 2). Overall awake NI values (96.7 +/- 1.4) were significantly higher (P < 0.001) than at the moment of loss of consciousness (58.3 +/- 17.5), with no overlap (P(K) 1.0), whereas P(K) values for cEEG, MAP and HR were all <0.85.

CONCLUSIONS: The pharmacodynamic relationship between eT(Des) and NI is age dependent with a significantly higher EC(50) in children than in adolescents and adults. The NI appears to be superior to cEEG, MAP and HR in differentiating consciousness from unconsciousness.