BIS monitoring made real time.
When the original monitor display was created by Aspect Medical Systems, the decision to display only the BIS trace was made to be esthetically pleasing to the eye. Since the BIS value is a derived value, the algorithm requires 15-30 seconds to calculate. Trying to titrate anesthetics in real time with a 15-30 seconds delayed value is akin to trying to drive an automobile with only the information from the rear view mirror.
The electromyogram (EMG) is a real time, direct physiologic parameter available to trend as a secondary trace to the BIS trace. By selecting this value, two traces will appear on the monitor screen. By responding to EMG spikes as if they were heart rate or blood pressure changes, the BIS monitor is then transformed into a real time monitor with dramatically improved utility. Titrating anesthetics with BIS/EMG is akin to driving an automobile looking through the front windshield.
1. Mathews DM, Clark L, Johansen J, et al. Increases in Electroencephalogram and Electromyogram Variability Are Associated with Increased Incidence of Intraoperative Somatic Response. Anes Analg 2012;114:759-770.
2. Friedberg BL: The effect of a dissociative dose of ketamine on the bispectral (BIS) index during propofol hypnosis. J Clin Anes 1999;11:4-7.
3. Friedberg BL: Propofol ketamine with bispectral (BIS) index monitoring chapter in Friedberg BL, ed.: Anesthesia in Cosmetic Surgery. Cambridge University Press, New York 1-13, 2007.