EEG and Electromyogram and Somatic Response

Dr. Loyferman

Increases in Electroencephalogram and Electromyogram Variability Are Associated with an Increased Incidence of Intraoperative Somatic Response

Donald M. Mathews, MD*, Laura Clark, MD†, Jay Johansen, MD, PhD‡, Emilio Matute, MD, PhD§ and Chandran V. Seshagiri, Phd. Anesthesia & Analgesia April 2012 vol. 114 no. 4 759-770

The variability of the Bispectral Index (BIS), the variability of facial electromyogram power (EMG), and the Composite Variability Index (CVI) are 3 new measures of electroencephalogram and EMG variability. CVI is a single measure of the combined variability in BIS and EMG. This multicenter study included 120 patients undergoing elective, noncardiac surgery from 4 different sites. General anesthesia was maintained using propofol and remifentanil at 2 of the sites and sevoflurane and remifentanil at the 2 other sites. Propofol or sevoflurane was adjusted to maintain BIS between 45 and 60. Clinicians were blinded to CVI (v2.0) at all times, and remifentanil infusions were adjusted at the discretion of the clinician. The times of all intraoperative somatic events, defined as movement, grimacing, or eye opening, were recorded. To quantify how effectively each variable discriminated between somatic event segments and nonevent segments, the area under the receiver operating characteristic (ROC) curve for each variable was computed. Finally, BIS, EMG, CVI, and the HR range before each somatic event was observed and the earliest time before the somatic event at which each variable was characterized thus being able to discriminate between the somatic events and a specified set of nonevents.

BIS, EMG, and CVI, measures of electroencephalogram and EMG variability increased when intraoperative somatic events occurred. BIS, EMG, and CVI discriminated between 10-minute segments that contained a somatic event and those segments that did not contain an event better than changes in HR and mean arterial blood pressure. Furthermore, CVI increases before somatic events began earlier than HR changes and may provide caregivers with an early warning of potentially inadequate antinociception.