The present study is designed to compare whether sBIS, sEMG, or CVI can be used to predict unwanted intraoperative somatic responses to stimulation, and to determine whether these values are related to patient-assessed postoperative pain scores. Our hypothesis is that increases in these variability measures are associated with increased probability of somatic responses. If our hypothesis is confirmed, these variability measures may help clinicians by highlighting periods of inadequate analgesia.