Figure 31-21 A, Clinical correlations of the bispectral (BIS) index. Maintaining the BIS index from 45 to 60 during general anesthesia appears to ensure unconsciousness with a hypnotic/opioid anesthetic technique while providing for rapid emergence (Adapted from Johansen JW, Sebel PS: Development and clinical application of electroencephalographic bispectrum monitoring. Anesthesiology 93:1336, 2000.) B, Electroencephalographic (EEG) changes observed with increasing depth of anesthesia. (Redrawn From Kelley SD: Monitoring Level of Consciousness during Anesthesia and Sedation. Natick, MA, Aspect Medical Systems, 2003.)