 Several methods based on the electroencephalogram have been tested to avoid these problems, but the results have been disappointing so far, so the BIS Monitor an dthe Entropy monitor.We have previously shown that the time-locked cortical response to standard external stimuli long-latency auditory evoked potentials or event-related potentials; ERPs can discriminate between clinically relevant light to moderate and deep sedation levels in healthy volunteers, when sedation is induced with a combination of propofol or midazolam with remifentanil. 