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.
Highlights
Sedation often involves greater prevalence of recall as defined by the nature of the targeted clinical condition[13,16,17]
We have previously assessed the relationship between anterior and posterior auditory evoked potentials (EP) as a measure of integrated brain function identifying that anterior brain activity is associated with attention processes, while the posterior brain activity is more related to perception processes[23,24]
This study focuses on alpha anteriorization, which may relate to attention and perception processes, as a measure of depth of anesthesia
Summary
Sedation often involves greater prevalence of recall as defined by the nature of the targeted clinical condition[13,16,17]. This study focuses on alpha anteriorization, which may relate to attention and perception processes, as a measure of depth of anesthesia. To measure attention and perception processes which are displayed in evoked potentials (EP) activity, we used a simple auditory oddball stimulus, which do not require patient’s response, in order to evoke and evaluate the electrophysiological activity. In this proof of concept study, we assessed EP response and generated a novel P/A index based on computerized analysis of the relation between the EP posterior alpha activity to the EP anterior alpha activity. We analyzed the P/A index in these two groups as another objective evaluation of an index, which is expected to be associated with recall
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