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?
Ans. b. Bispectral index monitoring (Ref: Morgan 4/144-146; Lee's 12/e p146, 286, 447)Use 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 (BIS)It 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 patient's 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: awake)BISAwareness Level and Depth of Anesthesia100Awake (memory intact, respond to verbal command)85-65Sedation65-40General anesthesia (no awareness, deep hypnosis, memory function lost)<40Cortical 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 Technique)Patient 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 spectra)Stimulus-response technique of auditory evoked potential.
Color Doppler
Bispectral index monitoring
Transesophageal echocardiography
Pulse plethysmography
Miscellaneous General Anesthesia