Evaluation of Anesthetic Specific EEG Dynamics during State Transitions between Loss and Return of Responsiveness

Purpose: electroencephalographic (EEG) information is used to monitor the level of cortical depression of a patient undergoing surgical intervention under general anesthesia. The dynamic state transitions into and out of anesthetic-induced loss and return of responsiveness (LOR, ROR) present a possibility to evaluate the dynamics of the EEG induced by different substances. We evaluated changes in the EEG power spectrum during anesthesia emergence for three different anesthetic regimens. We also assessed the possible impact of these changes on processed EEG parameters such as the permutation entropy (PeEn) and the cerebral state index (CSI). Methods: we analyzed the EEG from 45 patients, equally assigned to three groups. All patients were induced with propofol and the groups differed by the maintenance anesthetic regimen, i.e., sevoflurane, isoflurane, or propofol. We evaluated the EEG and parameter dynamics during LOR and ROR. For the emergence period, we focused on possible differences in the EEG dynamics in the different groups. Results: depending on the substance, the EEG emergence patterns showed significant differences that led to a substance-specific early activation of higher frequencies as indicated by the “wake” CSI values that occurred minutes before ROR in the inhalational anesthetic groups. Conclusion: our results highlight substance-specific differences in the emergence from anesthesia that can influence the EEG-based monitoring that probably have to be considered in order to improve neuromonitoring during general anesthesia.

Processed Electroencephalogram-Based Monitoring to Guide Sedation in Critically Ill Patients: A Systematic Review and International Expert Panel-Based Consensus Recommendations

BackgroundThe literature related to the use of processed EEG (pEEG) for depth of sedation (DOS) monitoring is increasing, however it is unclear how to use this type of monitoring for critical care patients within the intensive care unit (ICU).MethodsWe performed a systematic review of the literature according to the Grade of Recommendation assessment, Development, and Evaluation (GRADE) approach. The modified Delphi method was utilised by a team of experts to produce statements and recommendations derived from study questions. Three separate online rounds discussing 89 statements categorized into four domains were formulated. The panelists rated the appropriateness of each statement and were able to suggest modifications or addition of statements. An analysis of anonymised ratings of the statements by part of the panel followed each Delphi round and previously validated criteria were used to define appropriateness and consensus.ResultsLevel of evidence regarding the four domains was very low. Fourteen panelists participated in the Delphi rounds and consensus was reached for 28 out of 89 statements, from which the reccomendations were created. The main findings were that DOS monitoring should be performed in critically ill patients whenever clinical evaluation is not possible, it should be performed by continuous pEEG techniques and the resulting data depicted with graphical tools to facilitate detection of excessive sedation, a potential cause of burst-suppression, and finally, structured training is suggested to achieve a basic pEEG competency.ConclusionsAlthough evidence on using DOS monitors in ICU is scarce and further research is required in order to better define the benefits of using pEEG, the results of this consensus highlight the general agreement that critically-ill patients would benefit from this type of neuromonitoring.

Cerebral hemorrhagic infarction was diagnosed subsequently after high-amplitude slow waves detected on processed electroencephalogram during sedation: a case report

Background Continuous electroencephalogram (EEG) monitoring is useful for assessing the level of sedation and detecting non-convulsive epileptic seizures and cerebral ischemia in the intensive care unit. This report describes a case of cerebral hemorrhagic infarction diagnosed after the detection of high-amplitude slow waves on processed EEG during sedation. Case presentation A 68-year-old man who underwent cardiac surgery was sedated in the intensive care unit following an invasive procedure. High-amplitude slow waves appeared on processed EEG monitoring before the detection of anisocoria. Computed tomography revealed a cerebral hemorrhagic infarction. Conclusions In the management of critically ill patients, continuous EEG monitoring with forehead electrodes may be useful in the early detection of brain lesions.

Association Between Processed Electroencephalogram-Based Objectively Measured Depth of Sedation and Cerebrovascular Response: A Systematic Scoping Overview of the Human and Animal Literature

Background: Current understanding of the impact that sedative agents have on neurovascular coupling, cerebral blood flow (CBF) and cerebrovascular response remains uncertain. One confounding factor regarding the impact of sedative agents is the depth of sedation, which is often determined at the bedside using clinical examination scoring systems. Such systems do not objectively account for sedation depth at the neurovascular level. As the depth of sedation can impact CBF and cerebral metabolism, the need for objective assessments of sedation depth is key. This is particularly the case in traumatic brain injury (TBI), where emerging literature suggests that cerebrovascular dysfunction dominates the burden of physiological dysfunction. Processed electroencephalogram (EEG) entropy measures are one possible solution to objectively quantify depth of sedation. Such measures are widely employed within anesthesia and are easy to employ at the bedside. However, the association between such EEG measures and cerebrovascular response remains unclear. Thus, to improve our understanding of the relationship between objectively measured depth of sedation and cerebrovascular response, we performed a scoping review of the literature.Methods: A systematically conduced scoping review of the existing literature on objectively measured sedation depth and CBF/cerebrovascular response was performed, search multiple databases from inception to November 2020. All available literature was reviewed to assess the association between objective sedation depth [as measured through processed electroencephalogram (EEG)] and CBF/cerebral autoregulation.Results: A total of 13 articles, 12 on adult humans and 1 on animal models, were identified. Initiation of sedation was found to decrease processed EEG entropy and CBF/cerebrovascular response measures. However, after this initial drop in values there is a wide range of responses in CBF seen. There were limited statistically reproduceable associations between processed EEG and CBF/cerebrovascular response. The literature body remains heterogeneous in both pathological states studied and sedative agent utilized, limiting the strength of conclusions that can be made.Conclusions: Conclusions about sedation depth, neurovascular coupling, CBF, and cerebrovascular response are limited. Much further work is required to outline the impact of sedation on neurovascular coupling.

Comparison of the combination of propofol and etomidate versus propofol or etomidate alone for induction of general anesthesia: a double-blind, randomized controlled trial

IntroductionHemodynamic fluctuation during the induction of general anesthesia is a common event and adversely affect patients’ outcomes. The aim of this study is to investigate the impacts of different anesthesia induction agents: propofol, etomidate, and propofol-etomidate combination on patient hemodynamics and processed electroencephalography (EEG).Material and methodsSeventy-five patients undergoing elective non-cardiac surgery were randomly assigned to three groups of anesthesia induction agents: the group P received 2 mg/kg propofol, the group E received 0.3 mg/kg etomidate, and the group PE received the combination of 1mg/kg propofol plus 0.15mg/kg etomidate. Hemodynamic variables and processed EEG were measured during induction.ResultsHeart rate (HR) was significantly increased at intubation and 1 min after intubation compared with baseline in all three groups. Mean arterial pressure (MAP) decreased significantly after induction, at 5, and 10 min after intubation in group P (79.1±12.6, 77.0±14.2, 76.6±11.4 versus 93.2±9.9 mmHg; all P＜0.001). MAP increased significantly at intubation and 1 min after intubation in group E (104.7±13.0, 103.8±12.8 versus 92.9±10.2; P＜0.001, P=0.001 respectively). The incidence of myoclonus was lower in groups PE (4.0%) and P (4.0%) compared with that in group E (24.0%) (P=0.033). The incidence of pain at injection was higher in group P (28.0%) than that in groups PE and E (4.0% and 0.0%) (P=0.025).ConclusionsThe combination of propofol and etomidate used during induction of anesthesia provided a more stable BP profile, less pain at site of injection, and decreased myoclonic movements compared with propofol or etomidate alone.

Extended neuromonitoring in aortic arch surgery

Background Aortic arch repair for aortic dissection is still associated with a high mortality rate. Providing adequate means of neuromonitoring to guide cerebral hemodynamics is advantageous, especially during selective anterior cerebral perfusion (SACP). Objective We aimed to investigate an easy multimodal neuromonitoring set-up consisting of processed electroencephalography (EEG), near infrared spectroscopy (NIRS), and transcranial doppler sonography (TCD). Material and methods We collected intraoperative data from six patients undergoing surgery for aortic dissection. In addition to standard hemodynamic monitoring, patients underwent continuous bilateral NIRS, processed EEG with bispectral index (BIS), and intermittent transcranial doppler sonography of the medial cerebral artery (MCA) with a standard B‑mode ultrasound device. Doppler measurements were taken bilaterally before cardiopulmonary bypass (CPB), during CPB, and during SACP at regular intervals. Results Of the patients four survived without neurological deficits while two suffered fatal outcomes. Of the survivors two suffered from transient postoperative delirium. Multimodal monitoring led to a change in CPB flow or cannula repositioning in three patients. Left-sided mean flow velocities of the MCA decreased during SACP, as did BIS values. Conclusion Monitoring consisting of BIS, NIRS, and TCD may have an impact on hemodynamic management in aortic arch operations.

Common neural bases for processing speech prosody and music: An integrated model

It is shared notion that speech and music processing share some commonalities. Brain bioelectrical activity was recorded in healthy participants listening to music obtained by digitally transforming real speech into melodies played by viola. Sentences were originally pronounced with a positive or negative affective prosody. The research's aim was to investigate if the emotional content of music was extracted similarly to how the affective prosody of speech is processed. EEG was recorded from 128 electrodes in 20 healthy students. Participants had to detect rare neutral piano sounds while ignoring viola melodies. Stimulus negative valence increased the amplitude of frontal P300 and N400 ERP components while a late inferior frontal positivity was enhanced in response to positive melodies. Similar ERP markers were previously found for processing positive and negative music, vocalizations and speech. Source reconstruction applied to N400 showed that negative melodies engaged the right superior temporal gyrus and right anterior cingulate cortex, while positive melodies engaged the left middle and inferior temporal gyrus and the inferior frontal cortex. An integrated model is proposed depicting a possible common circuit for processing the emotional content of music, vocalizations and speech, which might explain some universal and relatively innate brain reaction to music.