Fig. 2. A shows a scatter plot demonstrating the relation between the Bispectral Index (BIS), the measured end-tidal sevoflurane concentration, and the clinical sedation score. Each point represents an assessment after target concentrations of the drug were achieved. Open circles represent observations classified as conscious (volunteers responded to verbal command, Observer’s Assessment of Alertness/Sedation [OAA/S] score ≥ 3), whereas filled circles are considered unconscious. B shows a similar plot for the relation between the BIS, the predicted effect site concentration of remifentanil, and the clinical sedation score. C and D show similar plots for the relation between the A-Line Auditory Evoked Potential Index (AAI), the clinical sedation score, and the measured end-tidal sevoflurane concentration ( C ) or the predicted effect site concentration of remifentanil.