Pharmacodynamic comparison of ADMS index and BIS during sevoflurane anesthesia: concentration-effect modeling and agreement analysis

Monitoring hypnotic depth using electroencephalography-derived indices is essential for safe and precise titration of volatile anesthetics; however, data directly comparing newer indices with established indices such as the bispectral index (BIS) remain limited.This prospective exploratory study evaluated the pharmacodynamic relationship between the anesthetic depth monitoring for sedation (ADMS) index and end-tidal sevoflurane concentration and assessed the agreement and dynamic performance of the ADMS index relative to the BIS in adult patients undergoing elective laparoscopic gastrectomy under sevoflurane anesthesia.The ADMS index and BIS were recorded simultaneously while a standardized protocol cycled end-tidal sevoflurane between 1.0 and 4.0 vol%, and sigmoidal E max models were used to describe the concentration-effect relationships for each index.Agreement was quantified using linear regression and Bland-Altman analysis, and the dynamic performance was characterized using Varvel metrics.The index values for loss and return of consciousness were also compared.Both indices showed inverse sigmoidal concentration-effect relationships with broadly similar pharmacodynamic parameters, albeit with substantial interindividual variability.Both indices demonstrated only moderate correlation and relatively wide limits of agreement, and the residual variability was greater for the ADMS index than for the BIS, indicating a noisier signal.Varvel metrics showed a modest negative bias and moderate inaccuracy of the ADMS index relative to the BIS, whereas the mean values at loss and return of consciousness were not significantly different between the indices.Thus, the ADMS index is broadly comparable to the BIS in terms of the information regarding hypnotic depth provided during sevoflurane anesthesia; however, its variability and wide limits of agreement indicate that it should be used judiciously as a replacement for the BIS.