Evaluation of the auditory evoked potentials derived aepEX as a measure of hypnotic depth in pediatric patients receiving sevoflurane-remifentanil anesthesia

Background The aepEX is a measure of depth of hypnosis (DoH), derived from processed mid-latency auditory evoked potentials. Objectives To evaluate the aepEX as a measure of DoH in children receiving sevoflurane-remifentanil anesthesia. Methods aepEX and bispectral index (BIS) were recorded simultaneously in 75 children, (1-3, 3-6, and 6-18years), receiving sevoflurane at endtidal concentrations (ETsevo) between 1.5 and 0.5 MAC. The ETsevo at which the aepEX and BIS had a value of 50 (EC50aepEX and EC50BIS) was calculated by nonlinear regression analysis. The accuracy of aepEX and BIS to predict the DoH was assessed by prediction probability (Pk) and receiver operating characteristics (ROC) analysis. Results Seventy-four children were included for analysis. The EC50aepEX (2.68%) and EC50BIS (2.10%) were comparable; the same accounts for the EC50aepEX of the different age groups and the EC50aepEX and EC50BIS of corresponding age groups. The EC50BIS in children aged 1-3years was lower than in the older age groups (P<0.05). Pk values of the aepEX (0.32, CI 95% 0.08-0.56) and BIS (0.47, CI 95% 0.19-0.75) were comparable. The area under the ROC curve was 0.72 (CI 95%: 0.62-0.82) and 0.67 (CI95%: 0.56-0.77) for the aepEX and BIS, respectively (P=0.54). Optimal cutoff values were >60 (aepEX) and >68 (BIS), with corresponding specificities 91%, CI 95%: 80-97% (aepEX) and 66%, CI 95%: 52-77% (BIS). Conclusions In this study with children receiving sevoflurane anesthesia, the aepEX outperformed the BIS in distinguishing unconsciousness from consciousness. Both indices performed equally bad in differentiating different levels of DoH.