<prompt> A 40-year female has to undergo incisional surgery under general anesthesia. She complains of awaken during her past cesarean section. Which of the following monitoring techniques can be used to prevent such awareness?Color DopplerBispectral index monitoringTransesophageal echocardiographyPulse plethysmography  <response>: Ans. b. Bispectral index monitoring Ref: Morgan 4144-146; Lees 12e p146, 286, 447Use of the bispectral index BIS, developed front a processed electroencephalogram, has been reported to decrease the incidence of anesthesia awareness when the BIS value is maintained below 60.Bispectral Index Scale BISIt is based on the principle of EEGQBispectral imaging analyses EEC date and quantitate anesthetic effects on the brain, specifically the hypnotic component.It is a composite numerical index, which represents a dimensionless numerical value that has been correlated with the patients current hypnotic state or depth of anaesthesia and provides some assurance that paralyzed anesthetized patient is also asleep unaware.BIS analysis may reduce chances of patient awareness during anesthesia. It may also reduce resource utilization because lesser drug is required to ensure amnesia, facilitating a faster wake up time and a shorter stay in recovery room.The BIS number decreases with increasing hypnosis.The BIS is derived from complex EEG analysis incorporating weighted information derived from the degree of burst suppression, spectral b band power and the bispectrum coherence.To make the EEG signals easier to interpret it uses 2 principles which are, which are, spectral analysis power and fast fourier analysis.It uses 3 EEG electrodes placed on frontal, parietal and temporal lobesQBIS is used to monitor: Intraoperative aw arenessQ. Depth of anesthesiaQIts value ranges from 0-100 0: coma: 100: awakeBISAwareness Level and Depth of Anesthesia100Awake memory intact, respond to verbal command85-65Sedation65-40General anesthesia no awareness, deep hypnosis, memory function lost40Cortical suppression becomes discernible, increasing burst suppression0Cortical silence isoelectric, deeply anesthetizedTarget intra-operative BIS: 40-60QTarget sedation BIS: 60-80QMethods used for Assessing Consciousness IntraoperativelyBispectral index BIS analysisNarcotrend monitor Monitor TechniquePatient state index PSI, Physiometrix is based on quantitative EEG signal relationship between frontal and occipital brain regionsEntropy monitors measure state entropy response over the range of 0.8-32 Hz, reflecting EEG dominant spectrum and response entropy response over range of 0.8-47 Hz, reflecting both EEG and EMG spectraStimulus-response technique of auditory evoked potential. 