Comparison of qNOX, pupil size and remifentanil concentration for the prediction of movement response to noxious stimulation during general anesthesia

Background and Goal of Study: The aim of this work is to compare different methods for predicting responsiveness to nociceptive stimulation: an EEG based indicator like qNOX[1] (Quantium Medical, Spain), the remifentanil predicted effect site concentration (CeRemi based on Minto model) and the baseline pupil size (iDMed, France) will be assessed as predictors of movement as a response to the tetanic stimulus (ulnar nerve, 100Hz, 60 mA) done with AlgiScan.

Materials and Methods: After the Ethics Committee of Hospital CLINIC de Barcelona approval, data were recorded from 93 patients scheduled for gynecologic surgery, under propofol-remifentanil TCI anesthesia. Intentional movement as a response to tetanic stimuli was considered a positive response. Responses to the tetanic stimuli from each patient were classified as movers (MOV) or non-movers (NMOV). The average values in the three seconds prior to tetanus of qNOX, CeRemi and the baseline pupil size (PS) (Fig.1) obtained for MOV and NMOV were compared through a t-student test and their prediction probability was assessed with the pk statistic[2]. qNOX values with signal quality index below 55 were excluded. [pic_01]

Results and discussion: 404 tetanic stimuli were obtained from 91 patients that could finally be included in data analysis. Results (Table I) show that although all indicators present statistically significant differences between MOV and NMOV, some of them have better prediction probabilities. CeRemi appeared to be the best predictor and PS showed a slightly higher pk value than qNOX, but not statistically significant as they present some overlap when considering the pk standard error. [tab_01]

Conclusion: The CeRemi proved to be the best predictor of movement response after tetanic stimulation, followed by PS and qNOX which showed a good and clinical equivalent performance.

References:
[1]Jensen EW et al. Acta Anaesthesiol Scand. 2014 Sep; 58: 933-41
[2]Smith WD, Dutton RC, Smith NT. Stat Med 1996; 15: 1199-215