Chanques G, et al. - This study entails the validity and performance assessment of the Analgesia Nociception Index (ANI) which varies from 0 (minimal parasympathetic tone, maximal stress-response and pain) to 100 (maximal parasympathetic tone, minimal stress-response and pain). It is an electrophysiological monitoring tool based on the spectral analysis of heart rate variability. According to findings, ANI displayed low sensitivity/specificity but ANIi≥43 had a Negative-Predictive-Value of 90%. Therefore, ANIi may be of highest benefit for excluding significant pain.