A New Index of Coordinated Posterior and Anterior Evoked EEG to Detect Recall Under Sedation – A Pilot Study

Abstract

EEG-based technologies may be limited in identifying recall under sedation (RUS). We developed a novel index, posteriorization/anteriorization (P/A) index, based on auditory evoked EEG signal and assessed whether it could differentiate between patients with or without RUS. Methods: EEG and BIS were sampled from 3 groups: 1. Patients undergoing sedation (n = 26); 2. Awake volunteers (n = 13, positive control for recall) 3. Patients undergoing general anesthesia (GA, n = 12, negative control for recall). In recovery, recall was assessed using the BRICE questionnaire. Of the 26 sedated patients, 12 experienced recall. Both The P/A index and BIS differentiated between patients with recall and no recall. However, BIS differentiation may have been sensitive to the main drug used for sedation (midazolam vs. propofol) and the P/A index did not show similar drug-based sensitivity. Furthermore, only BIS results were correlated with EMG. Conclusion: This pilot study provided support for the association between P/A index and recall after sedation. Further research is needed in integrating the index into clinical use: (1) it should be derived by an easy-to-use EEG system with a better signal-to-noise ratio; (2) its applicability to other drugs must be shown.

Identifying Recall Under Sedation by a Novel EEG Based Index of Attention—A Pilot Study

“…The study was approved by the Institutional Review Board (IRB), and written informed consent was obtained from all subjects. As an expansion of a previous study ( 47 ), we sampled additional 38 patients at Rambam healthcare campus, Haifa, Israel. Patients were recruited if they were: (1) undergoing sedation for various procedures (liver chemoembolization, biliary duct drainage); (2) were undergoing abdominal surgery under general anesthesia (GA).…”

“…In this pilot study, our objective was to test whether the CEI marker can be used in identifying recall under sedation. We previously showed a marker for RUS, but it was too cumbersome to use with multiple electrodes above hairline, with a poor signal to noise ratio ( 47 ). The use of CEI, which is easily extracted from below hairline electrodes, and has a good signal-to-noise ratio, was intended to overcome these limitations.…”

Intraoperative EEG-based monitors: are we looking under the lamppost?

“…For some time now, evidence suggests that in certain conditions, e.g. sedation, the currently-used markers are affected significantly by changes in EMG and therefore might not differentiate well in such settings between the effects of anesthesia and muscle activity [13,14–16,17 ▪ ,18 ▪ ,19,20]. Taken together, it is certainly possible to study the applicability of monitors for the reduction of AUA with further drug combinations and anesthesia protocols, but it seems safe to deduce clinical value for a set of rather prevalent drugs and protocols, but not so for other drugs and protocols…”