Individual intraoperative awareness is evaluated by-

A bispectral index (BIS) monitor is commonly utilized to assess depth of sedation when administering sedative, hypnotic, or anesthetic agents during surgical and medical procedures. The depth of sedation is calculated by measuring cerebral electric activity an electroencephalogram (EEG). The BIS algorithm processes the frontal EEG and conves the signal to a waveform on the BIS monitor 100 to 90-awake and responding appropriately to verbal stimulation 80 to 70-responsive to loud commands or mild shaking 70 to 60-intense tactile stimulation is needed for a response 60 to 40-unresponsive to verbal stimulus; general anesthesia obtained with a low chance for explicit recall less than 40-deep hypnotic state; possible protective responses still intact. less than 20-burst suppression (EEG pattern characterized by cycles of high-voltage electrical movement alternating with cycles of no activity in the brain); respiratory drive is limited, but possible protective responses still intact. 0-totally suppressed EEG (flat line). Ref: Miller's anesthesia 8th edition Ref: Morgan & Mikhail's clinical anesthesiology 6e