EEG Characteristics of Different Sedation Depths in Neurosurgery Patients

Prior to anesthesia induciton, EEG signatures will be recorded at Observer's Assessment of Alertness/Sedation (OAA/S) score of 5 (awake, eye-close state) for few minutes.

Given sedative anesthetics (propofol, midazolam or dexmetomidine), EEG signatures will be recorded after reaching steady state of OAA/S=3 (responds only after name called loudly and/or repeatedly) for few minutes.

Increasing drug concentration, EEG signatures will be recorded after reaching steady state of OAA/S=1 (does not respond to noxious stimuli) for few minutes.