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

Abstract

OverviewRecall is an accepted consequence of sedation. But due to the very low prevalence of the more devastating awareness under anesthesia (AUA), it might be of value to assess first the efficacy of new markers for AUA by their efficacy in discovering the more prevalent recall under sedation (RUS). In this pilot study we assessed whether a novel index for attentional effort, the cognitive effort index (CEI), derived in real-time from one forehead EEG channel, could differentiate between patients with or without RUS.MethodsEEG was sampled from 2 groups: (1) Patients who underwent deep sedation (n = 25) (using drugs according to the anesthesiologist preference, but generally combining either Midazolam or Propofol together with either Fentanyl or Remifentanil). (2) Patients who underwent general anesthesia (GA, n = 13, a negative control for recall). In recovery, recall was assessed using the BRICE questionnaire.ResultsOf the 25 sedated patients, 11 experienced recall. The CEI marker was high during significantly longer periods in patients with recall, compared to sedated patients, or patients under GA, without recall. Moreover, the increase in CEI was evident mainly toward the end of the procedure.ConclusionRUS seems to associate with higher level of attention, which is identified in real-time by the easy-to-extract CEI marker.

Evaluating a Novel EEG-Based Index for Stroke Detection Under Anesthesia During Mechanical Thrombectomy

“…We previously reviewed the literature on this topic 27 and have also demonstrated the ability to extract an EEG marker of attention during anesthesia from prefrontal delta activity. 28 We further showed that induced asymmetric focal brain injury leads to interhemispheric dissimilarity in this activity. 29 Following these earlier studies, we developed a novel EEG marker of prefrontal symmetry of activity, which might be attention-related; this is the lateral interconnection ratio (LIR).…”

“…It seems that the answer is yes. We previously reviewed the literature on this topic 27 and have also demonstrated the ability to extract an EEG marker of attention during anesthesia from prefrontal delta activity 28 . We further showed that induced asymmetric focal brain injury leads to interhemispheric dissimilarity in this activity 29 …”

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

“…This renders them less practical for ongoing real-time monitoring. More recently, algorithms have been developed to extract real-time markers of attentional processes from single channels, necessitating short measurement times, at the scale of seconds [56,57,58,59 ▪ ,60 ▪ ,61,62 ▪ ,63,64,65 ▪ ,66,67].…”

“…As stated above, it seems that mainly selective attention markers, which are related to the perception of external stimuli, might be clearly identifiable under effective anesthesia, while markers for the more entailing sustained attention might be reduced [24 ▪ ] (see a discussion of the differences among attention processes in [71]). Therefore, when markers for sustained attention are actually noted under anesthesia, it might indicate awareness [62 ▪ ]. Thus, the use of relevant attention-related monitoring might be applicable not only to prevention of delirium, but also as a marker for awareness under anesthesia.…”

“…Thus, the use of relevant attention-related monitoring might be applicable not only to prevention of delirium, but also as a marker for awareness under anesthesia. Furthermore, this modality should be generally applicable to all types of anesthetic drugs and protocols, and might not be significantly impacted by EMG activity, or its lack (elaboration on the impact of EMG on the single channel prefrontal real-time markers can be found in [62 ▪ ] – relevant methods section). This generality is due to the fact that, regardless of the drug or protocol, awareness under anesthesia will evoke an intense activity of sustained attention.…”