<prompt> A 60 year old female patient underwent modified radical mastectomy under general anesthesia. She is very anxious preoperatively. What monitor anesthetist might have used during surgery so that she does not remember anything intraoperative event.Color dopplerEnd tidal co2Bispectral indexEvoked potentials  <response>: Monitors used to assess depth of anesthesia: Electroencephalography EEG Bispectral index BIS Entropy Evoked responses EP - Motor EP, sensory EP Auditory, visual, brain stem evoked potential Patient safety index Narcotrend The bispectral index BIS is an empirically derived scale which helps to monitor the depth of anesthesia and intraoperative awareness. It processes the EEG and provides an index value between 0 and 100 that indicates the patients level of consciousness. BIS index values range: 100 - Awake Responds to normal voice 0 - Flatline EEG Deep coma Recommended range of BIS index values for anesthesia- 40-60. 