Wavelet transform-based mode decomposition for EEG signals under general anesthesia.
PeerJ
Background:Mode decomposition methods are used to extract the characteristic intrinsic mode function (IMF) from various multidimensional time series signals. We analyzed an electroencephalogram (EEG) dataset for sevoflurane anesthesia using two wavelet transform-based mode decomposition methods, comprising the empirical wavelet transform (EWT) and wavelet mode decomposition (WMD) methods, and compared the results with those from the previously reported variational mode decomposition (VMD) method. Methods:To acquire the EEG data, we used the software application EEG Analyzer, which enabled the recording of raw EEG signals the serial interface of a bispectral index (BIS) monitor. We also created EEG mode decomposition software to perform empirical mode decomposition (EMD), VMD, EWT, and WMD operations. Results:When decomposed into six IMFs, the EWT enables narrow band separation of the low-frequency bands IMF-1 to IMF-3, in which all central frequencies are less than 10 Hz. However, in the upper IMF of the high-frequency band, which has a center frequency of ≥ 10 Hz, the dispersion within the frequency band covered was widespread among the individual patients. In WMD, a narrow band of clinical interest is specified using a bandpass filter in a Meyer wavelet filter bank within a specific mode-decomposition discipline. When compared with the VMD and EWT methods, the IMF that was decomposed WMD was accommodated in a narrow band with only a small variance for each patient. Multiple linear regression analyses demonstrated that the frequency characteristics of the IMFs obtained from WMD best tracked the changes in the BIS upon emergence from general anesthesia. Conclusions:The WMD can be used to extract subtle frequency characteristics of EEGs that have been affected by general anesthesia, thus potentially providing better parameters for use in assessing the depth of general anesthesia.
10.7717/peerj.18518
Electroencephalographic bispectral index correlates with intraoperative recall and depth of propofol-induced sedation.
Liu J,Singh H,White P F
Anesthesia and analgesia
The bispectral (BIS) index and 95% spectral edge frequency (SEF) of the electroencephalograph (EEG) have been used to study the anesthetic and sedative effects of intravenously (i.v.) administered drugs. This prospective study was designed to evaluate the effectiveness of the BIS index and 95% SEF for assessing the level of propofol-induced sedation and amnesia during regional anesthesia. Ten consenting adult patients undergoing surgery with regional anesthesia were administered propofol in increments of 10-20 mg i.v., every 5-10 min until they became unresponsive to tactile stimulation (i.e., mild prodding or shaking). The BIS index and 95% SEF were continuously recorded from a bifrontal montage (Fp1-Cz and Fp2-Cz) using the Aspect B500 monitor. The depth of sedation was assessed clinically at 5- to 10-min intervals using the observer's assessment of alertness/sedation (OAA/S) scale, with 1 = no response to tactile stimulation to 5 = wide awake. Each patient was shown a picture of an animal (cat) prior to administration of an initial dose of propofol, 40 mg i.v.. Subsequently, patients were administered intermittent bolus doses of propofol, 10-20 mg i.v., and shown different pictures upon achieving OAA/S scores of 4, 3, and 2 during the onset of and recovery from propofol-induced sedation. Picture recall was tested upon arrival of the patient in the postanesthesia care unit (PACU). Of the two EEG variables studied, the BIS index exhibited a better correlation with the OAA/S scores during both the onset (Spearman's rho = 0.744) and recovery (Spearman's rho = 0.705) phases of propofol-induced sedation. With the increasing depth of sedation, there was a progressive decrease in the BIS index (OAA/S score of 5, BIS = 94.5 +/- 2.9; 4, 93.3 +/- 3.3; 3, 89 +/- 6.1; 2, 80.1 +/- 8.7; 1, 75.6 +/- 7.5; mean +/- SD). Conversely, there was a progressive increase in the BIS value during recovery from propofol sedation (OAA/S score of 1, BIS = 75.6 +/- 7.5; 2, 82.4 +/- 10.5; 3, 84.9 +/- 5.9; 4, 93.8 +/- 0.8). Although the changes in the 95% SEF values were less consistent during the onset phase, this EEG variable increased from 16.4 +/- 5.0 to 19.3 +/- 5.6 as the OAA/S score increased from 1 to 4 during the recovery phase. Patient recall of the intraoperative pictures decreased with increasing depth of sedation and decreasing BIS values (OAA/S:% BIS:% recall = 5:94.5 +/- 2.9:100%; 4:93.4 +/- 3:63%; 3:87.3 +/- 6.1:40%; 2:80.8 +/- 8.3:0%; 1:75.6 +/- 7.5:0%). The BIS index appears to be a useful variable for assessing the depth of propofol-induced sedation. Increasing depth of sedation was associated with a significant decrease in intraoperative picture recall.
10.1097/00000539-199701000-00033
Bispectral index and anaesthesia in the elderly.
Renna M,Venturi R
Minerva anestesiologica
BACKGROUND:Due to pharmacokinetic and pharmacodynamic reasons, the elderly are at particular risk of incurring unwanted side effects of drugs commonly used in anaesthesia. The bispectral index (BIS) is an EEG-derived value that measures the sedative component of the anaesthetic state. The BIS could be useful in guiding titration of anaesthetic drugs in the elderly. METHODS:A review of the published data was performed by the authors in order to assess the suitability of BIS technology application to the geriatric population. RESULTS:Age-related EEG differences exist in the normal population but they do not affect the BIS. The BIS correlates with depth of sedation independently of age. Senile dementia may be associated with significantly lower BIS values. CONCLUSIONS:The BIS is a useful guidance for titration of anaesthetic drugs in the elderly. The presence of senile dementia may be a confounding factor in the interpretation of the BIS values during anaesthesia.
EEG-bispectral index changes with ketamine versus thiamylal induction of anesthesia.
Wu C C,Mok M S,Lin C S,Han S R
Acta anaesthesiologica Sinica
BACKGROUND:The EEG-Bispectral Index (BIS) is a processed EEG information that has been validated as a means to measure the hypnotic effect of anesthetic drugs. In this study we evaluated the BIS changes in induction of anesthesia with ketamine in comparison with that of thiamylal. METHODS:Forty ASA class I and II adult female patients undergoing elective gynecologic surgeries were enrolled into this randomized, prospective study. No premedication was given to the patient. In each patient EEG was recorded continuously from the frontal electrodes using Aspect A-1050 monitor after his arrival at the operating room. Blood pressure and heart rate were also recorded throughout the surgery. After steady baseline recordings of all necessary parameters having been accomplished Group K patients (n = 20) were given an induction dose of ketamine 1.5 mg/kg i.v., whereas Group T patients (n = 20) received thiamylal 5 mg/kg i.v. When loss of consciousness was ascertained, intubation was performed after administration of succinylcholine 1 mg/kg i.v. and anesthesia was maintained with isoflurane-nitrous oxide-oxygen. Demographics, BIS values, HR, BP were analyzed and compared. RESULTS:The demographics were comparable between the two groups. Both groups showed a mean value of BIS of 96 with comparable BP and HR before induction. After study drug the post-induction BIS for ketamine was 94 as against 51 for thiamylal (P < 0.05), 91 against 43 post-succinylcholine (P < 0.05), 92 against 53 post-intubation (P < 0.05) and 45 against 37 five min after isoflurane. BIS remained below 60 throughout the entire course of anesthesia and returned to above 95 on emergence in both groups. None of the patients reported awareness, recall, delirium or hallucination during anesthesia. CONCLUSIONS:Ketamine-induced dissociative anesthesia produces persistently elevated BIS index which is different from thiamylal and those reported with other conventional anesthetic agents. The established range of BIS index appears not to be applicable in patients under ketamine anesthesia. Monitoring the depth of ketamine anesthesia remains to be a challenging problem.
The use of bispectral analysis to monitor outpatient sedation.
Sandler N A
Anesthesia progress
The bispectral (BIS) index has been used to interpret partial EEG recordings to predict the level of sedation and loss of consciousness in patients undergoing general anesthesia. The author has evaluated BIS technology in determining the level of sedation in patients undergoing outpatient deep sedation. These experiences are outlined in this review article. Initially, the correlation of the BIS index with traditional subjective patient evaluation using the Observer's Assessment of Alertness and Sedation (OAA/S) scale was performed in 25 subjects. In a second study, the recovery profile of 39 patients where the BIS was used to monitor sedation was compared with a control group where the monitor was not used. A strong positive relationship between the BIS and OAA/S readings was found in the initial subjects. From the recovery study, it appears that use of the BIS monitor may help titrate the level of sedation so that less drugs are used to maintain the desired level of sedation. A trend to earlier return of motor function in BIS-monitored patients was also demonstrated. BIS technology offers an objective, ordinal means of assessing the depth of sedation. This can be invaluable in comparing studies of techniques. The BIS index provides additional information to standard monitoring techniques that helps guide the administration of sedative-hypnotic agents. The trend to earlier return of motor function in BIS-monitored patients warrants further investigation.
Bispectral index monitor: an evidence-based analysis.
Ontario health technology assessment series
The objective of this analysis was to evaluate the effectiveness and cost-effectiveness of the bispectral index (BIS) monitor, a commercial device to assess the depth of anesthesia. Conventional methods to assess depth of consciousness, such as cardiovascular and pulmonary measures (e.g., heart rate, systolic/diastolic blood pressure, mean arterial pressure, respiratory rate, and level of oxygen in the blood), and clinical signs (e.g., perspiration, shedding of tears, and limb movement) are not reliable methods to evaluate the brain status of anesthetized patients. Recent progress in understanding the electrophysiology of the brain has led to the development of cerebral monitoring devices that identify changes in electrophysiologic brain activity during general anesthesia. The BIS monitor, derived from electroencephalogram (EEG) data, has been used as a statistical predictor of the level of hypnosis and has been proposed as a tool to reduce the risk of intraoperative awareness. Anesthesia that is too light can result in the recall of events or conversations that happen in the operation room. Patients have recalled explicit details of conversations that happened while under anesthesia. This awareness is frightening for patients and can lead to post-traumatic stress disorder. Conversely, anesthesia that is too deep can cause hemodynamic disturbances necessitating the use of vasoconstrictor agents, which constrict blood vessels, to maintain normal blood pressure and cardiac output. Overly deep anesthesia can also result in respiratory depression requiring respiratory assistance postoperatively. Monitoring the depth of anaesthesia should prevent intraoperative awareness and help to ensure that an exact dose of anaesthetic drugs is given to minimize adverse cardiovascular effects caused by overly large doses. Researchers have suggested that cerebral monitoring can be used to assess the depth of anesthesia, prevent awareness, and speed early recovery after general anesthesia by optimizing drug delivery to each patient. Awareness is a rare complication in general anesthesia. The risk of intraoperative awareness varies among countries, depending on their anesthetic practices. In the United States, the incidence of intraoperative awareness is 0.1% to 0.2% of patients undergoing general anesthesia. The incidence of intraoperative awareness depends on the type of surgery. Trauma patients have reported the highest incidence of intraoperative awareness (11%-43%) followed by patients undergoing cardiac surgery (1.14%) and patients undergoing Cesarean section (0.9%). The BIS monitor, licensed by Health Canada, is the first quantitative EEG index used in clinical practice as a monitor to assess the depth of anesthesia. It consists of a sensor, a digital signal converter, and a monitor. The sensor is placed on the patient's forehead to pick up the electrical signals from the cerebral cortex and transfer them to the digital signal converter. A BIS score quantifies changes in the electrophysiologic state of the brain during anesthesia. In patients who are awake, a typical BIS score is 90 to 100. Complete suppression of cortical activity results in a BIS score of 0, known as a flat line. Lower numbers indicate a higher hypnotic effect. Overall, a BIS value below 60 is associated with a low probability of response to commands. There are several alternative technologies to quantify the depth of anesthesia, but only the BIS and SNAP monitors are licensed in Canada. The list price of the BIS monitor is $13,500 (Cdn). The sensors cost $773 (Cdn) for a box of 25. Because intraoperative awareness and recall happen rarely, only 1 randomized controlled trial of all the studies reviewed, was adequately powered to show the impact of BIS monitoring. This was a large prospective, randomized, double-blinded, multicentre study that was designed to investigate if BIS-guided anesthesia reduces the incidence of intraoperative awareness. The study confirmed 2 cases of intraoperative awareness in the BIS group and 11 cases in the standard practice group. This difference was statistically significant (P =.022). There were 36 reports of possible awareness that were not confirmed by the study group (20 patients in the BIS group and 16 in the standard practice group). Additionally, the results of small randomized controlled trials and prospective cohort studies show that, overall, BIS monitoring is relatively good at indicating the state of being alert; however, its algorithm does not accurately predict an unconscious state. BIS monitoring has low sensitivity for the detection of the state of being asleep, and it may show values higher than 60 in those already asleep. Therefore, an unknown percentage of patients will not be identified as being asleep and will receive anesthetics unnecessarily. Based on the literature review, the Medical Advisory Secretariat concludes the following: Prevention of awareness should remain a clinical decision for anesthesiologists to make based on their experience with intraoperative awareness in their practices.Although BIS monitoring may have a positive impact on reducing the incidence of intraoperative awareness in the general population, its negative impact on individual patients may overshadow this positive outcome.BIS monitoring is good at indicating an "alert" state, which is why it can reduce the incidence of intraoperative awareness; however, its algorithm does not accurately predict an "asleep" state. This means an unknown percentage of patients who are already asleep will not be identified because of falsely elevated BIS values. These patients will receive unnecessary dosage of anesthetics resulting in a deep hypnotic state.Adherence to the practice guidelines will reduce the risk of intraoperative awareness.
Quantifying cortical activity during general anesthesia using wavelet analysis.
Zikov Tatjana,Bibian Stéphane,Dumont Guy A,Huzmezan Mihai,Ries Craig R
IEEE transactions on bio-medical engineering
This paper reports on a novel method for quantifying the cortical activity of a patient during general anesthesia as a surrogate measure of the patient's level of consciousness. The proposed technique is based on the analysis of a single-channel (frontal) electroencephalogram (EEG) signal using stationary wavelet transform (SWT). The wavelet coefficients calculated from the EEG are pooled into a statistical representation, which is then compared to two well-defined states: the awake state with normal EEG activity, and the isoelectric state with maximal cortical depression. The resulting index, referred to as the wavelet-based anesthetic value for central nervous system monitoring (WAV(CNS)), quantifies the depth of consciousness between these two extremes. To validate the proposed technique, we present a clinical study which explores the advantages of the WAV(CNS) in comparison with the BIS monitor (Aspect Medical Systems, MA), currently a reference in consciousness monitoring. Results show that the WAV(CNS) and BIS are well correlated (r = 0.969) during periods of steady-state despite fundamental algorithmic differences. However, in terms of dynamic behavior, the WAV(CNS) offers faster tracking of transitory changes at induction and emergence, with an average lead of 15-30 s. Furthermore, and conversely to the BIS, the WAV(CNS) regains its preinduction baseline value when patients are responding to verbal command after emergence from anesthesia. We conclude that the proposed analysis technique is an attractive alternative to BIS monitoring. In addition, we show that the WAV(CNS) dynamics can be modeled as a linear time invariant transfer function. This index is, therefore, well suited for use as a feedback sensor in advisory systems, closed-loop control schemes, and for the identification of the pharmacodynamic models of anesthetic drugs.
10.1109/TBME.2006.870255
When is a bispectral index of 60 too low?: Rational processed electroencephalographic targets are dependent on the sedative-opioid ratio.
Manyam Sandeep C,Gupta Dhanesh K,Johnson Ken B,White Julia L,Pace Nathan L,Westenskow Dwayne R,Egan Talmage D
Anesthesiology
BACKGROUND:Opioids are commonly used in conjunction with sedative drugs to provide anesthesia. Previous studies have shown that opioids reduce the clinical requirements of sedatives needed to provide adequate anesthesia. Processed electroencephalographic parameters, such as the Bispectral Index (BIS; Aspect Medical Systems, Newton, MA) and Auditory Evoked Potential Index (AAI; Alaris Medical Systems, San Diego, CA), can be used intraoperatively to assess the depth of sedation. The aim of this study was to characterize how the addition of opioids sufficient to change the clinical level of sedation influenced the BIS and AAI. METHODS:Twenty-four adult volunteers received a target-controlled infusion of remifentanil (0-15 ng/ml) and inhaled sevoflurane (0-6 vol%) at various target concentration pairs. After reaching pseudo-steady state drug levels, the modified Observer's Assessment of Alertness/Sedation score, BIS, and AAI were measured at each target concentration pair. Response surface pharmacodynamic interaction models were built using the pooled data for each pharmacodynamic endpoint. RESULTS:Response surface models adequately characterized all pharmacodynamic endpoints. Despite the fact that sevoflurane-remifentanil interactions were strongly synergistic for clinical sedation, BIS and AAI were minimally affected by the addition of remifentanil to sevoflurane anesthetics. CONCLUSION:Although clinical sedation increases significantly even with the addition of a small to moderate dose of remifentanil to a sevoflurane anesthetic, the BIS and AAI are insensitive to this change in clinical state. Therefore, during "opioid-heavy" sevoflurane-remifentanil anesthetics, targeting a BIS less than 60 or an AAI less than 30 may result in an unnecessarily deep anesthetic state.
10.1097/00000542-200703000-00011
Depth of anesthesia monitoring.
Bowdle T Andrew
Anesthesiology clinics
Depth-of-anesthesia monitoring with EEG or EEG combined with mLAER is becoming widely used in anesthesia practice. Evidence shows that this monitoring improves outcome by reducing the incidence of intra-operative awareness while reducing the average amount of anesthesia that is administered, resulting in faster wake-up and recovery, and perhaps reduced nausea and vomiting. As with any monitoring device, there are limitations in the use of the monitors and the anesthesiologist must be able to interpret the data accordingly. The limitations include the following. The currently available monitoring algorithms do not account for all anesthetic drugs, including ketamine, nitrous oxide and halothane. EMG and other high-frequency electrical artifacts are common and interfere with EEG interpretation. Data processing time produces a lag in the computation of the depth-of-anesthesia monitoring index. Frequently the EEG effects of anesthetic drugs are not good predictors of movement in response to a surgical stimulus because the main site of action for anesthetic drugs to prevent movement is the spinal cord. The use of depth-of-anesthesia monitoring in children is not as well understood as in adults. Several monitoring devices are commercially available. The BIS monitor is the most thoroughly studied and most widely used, but the amount of information about other monitors is growing. In the future, depth-of-anesthesia monitoring will probably help in further refining and better understanding the process of administering anesthesia.
10.1016/j.atc.2006.08.006
When the bispectral index (bis) can give false results.
Duarte Leonardo Teixeira Domingues,Saraiva Renato Angelo
Revista brasileira de anestesiologia
BACKGROUND AND OBJECTIVES:The bispectral index (BIS) is a multifactorial parameter derived from the electroencephalogram (EEG), which allows monitoring of the hypnotic component of anesthesia. It was obtained from the algorithm based on the analysis of a large number of EEGs from volunteers and patients undergoing sedation and general anesthesia with different anesthetic agents. The use of BIS to monitor the depth of anesthesia reduces the incidence of intraoperative awakening and recall, among other benefits. The objective of this review was to present clinical situations in which the BIS gives false results, either elevated or decreased, due to conditions related to the patient or anesthetic actions unforeseen when the algorithm was elaborated. CONTENTS:The bispectral index can be altered and influenced in different clinical situations in which abnormal EEG patterns are present; the effects of different anesthetics and other drugs not included when the algorithm was elaborated; interference from electrical equipment; as well as peculiarities of the monitor. CONCLUSIONS:Although the BIS algorithm underwent several changes since its first version, the anesthesiologist should be aware of situations that cause false BIS readings to avoid complications, may it be secondary to anesthetic overdose or underdosing, which might cause intraoperative awakening and recall.
10.1590/s0034-70942009000100013
Analysis of pharmacodynamic interaction of sevoflurane and propofol on Bispectral Index during general anaesthesia using a response surface model.
Diz J C,Del Río R,Lamas A,Mendoza M,Durán M,Ferreira L M
British journal of anaesthesia
BACKGROUND:Propofol and sevoflurane act on the GABA(A) receptor, modulating the function of this receptor in an additive manner. The pharmacodynamic interaction of both drugs considering their effect on EEG activity analysed by the bispectral index (BIS) was identified as additive, but this has not been studied in a clinical setting. The objective of this study was to analyse the pharmacodynamic interaction of propofol and sevoflurane on BIS using a surface response model in patients undergoing general anaesthesia with i.v. induction and inhalation maintenance. METHODS:We performed a prospective study in 24 patients undergoing general anaesthesia with propofol induction and sevoflurane maintenance. Anaesthetic depth was measured with a BIS VISTA Bilateral monitor. Propofol biophase concentration was determined using a three-compartment pharmacokinetic model, and sevoflurane end-tidal concentration was measured continuously. The response surface model described by Minto and colleagues was used to analyse the interaction. Statistical analysis was performed with Excel 2002 and SPSS v11.0. RESULTS:The mean value of U(50)(theta) was 0.956 (sd 0.029) in the overall estimated data, and remained within the predefined range for all ratios of the drugs, fulfilling the criterion of additivity. The median of the weighted residuals between the actual BIS value and the BIS value predicted by the model was -5.926%. CONCLUSIONS:Under the study conditions, it was confirmed that sevoflurane and propofol have an additive effect on BIS, with no evidence suggesting the existence of a synergistic effect for the concentrations of both drugs typically used in clinical practice.
10.1093/bja/aeq081
Wide inter-individual variability of bispectral index and spectral entropy at loss of consciousness during increasing concentrations of dexmedetomidine, propofol, and sevoflurane.
Kaskinoro K,Maksimow A,Långsjö J,Aantaa R,Jääskeläinen S,Kaisti K,Särkelä M,Scheinin H
British journal of anaesthesia
BACKGROUND:The bispectral index (BIS) and the spectral entropy (state entropy, SE, and response entropy, RE) are depth-of-anaesthesia monitors derived from EEG and have been developed to measure the effects of anaesthetics on the cerebral cortex. We studied whether they can differentiate consciousness from unconsciousness during increasing doses of three different anaesthetic agents. METHODS:Thirty healthy male volunteers aged 19-30 yr were recruited and divided into three 10-volunteer groups to receive either dexmedetomidine, propofol, or sevoflurane in escalating concentrations at 10 min intervals until loss of consciousness (LOC) was reached. Consciousness was tested at 5 min intervals and after drug discontinuation at 1 min intervals by requesting the subjects to open their eyes. LOC was defined as unresponsiveness to the request and pre-LOC as the last meaningful response. The first meaningful response to the request after drug discontinuation was defined as regaining of consciousness (ROC). For the statistical analysis, pre-LOC and ROC values were pooled to represent the responsive state while LOC values represented the unresponsive state. Prediction probability (P(K)) was estimated with the jack-knife method. RESULTS:The lowest mean values for BIS, SE, and RE were recorded at LOC with all three drugs. The P(K) values were low for dexmedetomidine (BIS 0.62, SE 0.58, RE 0.59), propofol (BIS 0.73, SE 0.72, RE 0.72), and sevoflurane (BIS 0.70, SE 0.52, RE 0.62). CONCLUSIONS:Because of wide inter-individual variability, BIS and entropy were not able to reliably differentiate consciousness from unconsciousness during and after stepwise increasing concentrations of dexmedetomidine, propofol, and sevoflurane.
10.1093/bja/aer196
Assessment of depth of anesthesia: PRST score versus bispectral index.
Smajic Jasmina,Praso Mirsada,Hodzic Mirsad,Hodzic Samir,Srabovic-Okanovic Amna,Smajic Nedim,Djonlagic Zinka
Medicinski arhiv
UNLABELLED:Assessment of depth of anesthesia is the basis in anesthesiologists work because the occurrence of awareness during general anesthesia is important due to stress, which is caused in the patient at that moment, and due to complications that may arise later. There are subjective and objective methods used to estimate the depth of anesthesia. The aim of this study was to assess the depth of anesthesia based on clinical parameters and on the basis bispectral index, and determine the part of bispectral monitoring in support to clinical assessment. MATERIAL AND METHODS:Sixty patients divided into two groups were analyzed in a prospective study. In first group (group 1), the depth of anesthesia was assessed by PRST score, and in the second group (group 2) was assessed by bispectral monitoring with determination PRST score concurrently. In both groups PRST score was assessed in four periods, while bispectral monitoring is used continuously. For analysis were used the BIS index values from the equivalent periods as PRST scores. PRST score value 0-3, and BIS index 40-60 were considered as adequate depth of anesthesia. The results showed that in our study were not waking patients during the surgery. In the group where the depth of anesthesia assessed clinically, we had a few of respondents (13%) for whom at some point were present indicators of light anesthesia. Postoperative interview excluded the possibility of intraoperative awareness. In the second group of patients and objective and clinical assessment indicated at all times to adequate depth of anesthesia. CONCLUSION:The use of BIS monitoring with clinical assessment allows anesthesiologists precise decision-making in balancing and dosage of anesthetics and other drugs, as well as treatment in certain situations.
10.5455/medarh.2011.65.216-220
Closed loop anaesthesia at high altitude (3505 m above sea level): Performance characteristics of an indigenously developed closed loop anaesthesia delivery system.
Puri Goverdhan D,Jayant Aveek,Tsering Morup,Dorje Motup,Tashi Motup
Indian journal of anaesthesia
BACKGROUND:Closed loop anaesthesia delivery systems (CLADSs) are a recent advancement in accurate titration of anaesthetic drugs. They have been shown to be superior in maintaining adequate depth of anaesthesia with few fluctuations as compared with target-controlled infusion or manual titration of drug delivery. METHODS:Twenty patients scheduled to undergo general abdominal or orthopaedic procedures under general anaesthesia at Leh (3505 m above sea level) were recruited as subjects. Anaesthesia was delivered by a patented closed loop system that uses the Bispectral Index (BIS™) as a feedback parameter to titrate the rate of propofol infusion. All vital parameters, drug infusion rate and the BIS™ values were continuously recorded and stored online by the system. The data generated was analysed for the adequacy of anaesthetic depth, haemodynamic stability and post-operative recovery parameters. RESULTS:The CLADS was able to maintain a BIS™ within ±10 of the target of 50 for 85.0±7.8% of the time. Haemodynamics were appropriately maintained (heart rate and mean arterial blood pressure were within 25% of baseline values for 91.2±2.2% and 94.1±3% of the total anaesthesia time, respectively). Subjects were awake within a median of 3 min from cessation of drug infusion and achieved fitness to recovery room discharge within a median of 15 min. There were no adverse events or report of awareness under anaesthesia. CONCLUSIONS:The study demonstrates the safety of our CLADS at high altitude. It seeks to extend the use of our system in challenging anaesthesia environments. The system performance was also adequate and no adverse events were recorded.
10.4103/0019-5049.98765
Change in auditory evoked potential index and bispectral index during induction of anesthesia with anesthetic drugs.
Matsushita Sachiko,Oda Shinya,Otaki Kei,Nakane Masaki,Kawamae Kaneyuki
Journal of clinical monitoring and computing
The aim of this study was to evaluate the efficacy of the auditory evoked potential (AEP) index (aepEX) as an assessment tool for hypnosis during induction of various anesthetic drugs, and to compare its performance to that of the bispectral index (BIS). A total of 45 cases were divided into three groups based on the drugs used for anesthesia. Before anesthetic induction, BIS and AEP monitors were initiated. Anesthesia was induced through intravenous injection (IV) as follows: MP (n = 15) group, midazolam (0.1 mg/kg IV); TP (n = 15) group, thiopental (4 mg/kg IV); and KP (n = 15) group, ketamine (2 mg/kg IV). After loss of response (LOR), an infusion of 3 μg/ml propofol via a target-controlled infusion was initiated in all groups. AepEX and BIS were measured in the waking state (baseline) and at LOR (1 min after LOR), pre-intubation (1 min after previous intubation) and post-intubation (1 min after tracheal intubation finished). The value of aepEX significantly decreased in all groups with LOR and that of BIS also decreased except of KP group. No significant difference were observed in BIS values between baseline and LOR in the KS group. The aepEX might be more useful than BIS for hypnosis monitoring during anesthetic induction, particularly when drugs such as ketamine are used.
10.1007/s10877-014-9643-x
Comparison of the effect of electromyogram activity during emergence on anesthetic depth monitoring between phase lag entropy and bispectral index: a prospective observational study.
Annals of palliative medicine
BACKGROUND:The bispectral index (BIS) is the most widely used algorithm for measuring anesthetic depth. The BIS has been demonstrated as inaccurate when neuromuscular blocking drugs (NMBDs) are used. Compared with BIS, phase lag entropy (PLE), which measures the anesthetic depth based on a 4-channel EEG signal, is less affected by EMG. The purpose of this study was to compare the effect of EMG activity during emergence on anesthetic depth monitoring between PLE and BIS. METHODS:Twenty five consecutive patients with physical status I-II of American Society of Anesthesiologists undergoing general anesthesia (age range, 20-60 years). The anesthesiologist attached the sensors of BIS and PLEM 100 on the patient's forehead. NMB reversal was performed by intravenously injecting sugammadex after confirmation of shallow NMB (TOF count 1-4) under neuromuscular monitoring. The BIS and PLE scores were recorded with neuromuscular monitoring at 1-min intervals for 5 min after administration of sugammadex. RESULTS:The BIS and BIS-EMG measured at 1 min after sugammadex injection were significantly higher at 1 min [51.650 (46.100, 62.225) (P<0.001); 28.500 (27.800, 31.075) (P=0.003)] than at 0 min. However, there was no between-time point difference in the PLE score and PLE-EMG (P=0.0843, P=0.329). CONCLUSIONS:In general anesthesia using propofol-remifentanil, the BIS at 1 min after sugammadex reversal during emergence appears to be more affected by EMG activity than the PLE score. Therefore, immediately after sugammadex administration (within 1 min), it may be clinically useful to evaluate the consciousness status through the PLE score.
10.21037/apm-21-847
Assessment of Anesthesia Depth Using Effective Brain Connectivity Based on Transfer Entropy on EEG Signal.
Basic and clinical neuroscience
INTRODUCTION:Ensuring an adequate Depth of Anesthesia (DOA) during surgery is essential for anesthesiologists. Since the effect of anesthetic drugs is on the central nervous system, brain signals such as Electroencephalogram (EEG) can be used for DOA estimation. Anesthesia can interfere among brain regions, so the relationship among different areas can be a key factor in the anesthetic process. METHODS:In this paper, by combining the Wiener causality concept and the conditional mutual information, a nonlinear effective connectivity measure called Transfer Entropy (TE) is presented to describe the relationship between EEG signals at frontal and temporal regions from eight volunteers in three anesthetic states (awake, unconscious and recovery). This index is also compared with Granger causality and partial directional coherence methods as common effective connectivity indexes. RESULTS:Based on a statistical analysis of the probability predictive value and Kruskal-Wallis statistical method, TE can effectively fallow the effect-site concentration of propofol and distinguish the anesthetic states well, and perform better than the other effective connectivity indexes. This index is also better than Bispectral Index (BIS) as commercial DOA monitor because of the faster response and higher correlation with the drug concentration effect-site, less irregularity in the unconscious state and better ability to distinguish three states of anesthestesia. CONCLUSION:TE index is a confident indicator for designing a new monitoring system of the two EEG channels for DOA estimation.
10.32598/bcn.12.2.2034.2
Hierarchical Deep Reinforcement Learning-Based Propofol Infusion Assistant Framework in Anesthesia.
IEEE transactions on neural networks and learning systems
This article aims to provide a hierarchical reinforcement learning (RL)-based solution to the automated drug infusion field. The learning policy is divided into the tasks of: 1) learning trajectory generative model and 2) planning policy model. The proposed deep infusion assistant policy gradient (DIAPG) model draws inspiration from adversarial autoencoders (AAEs) and learns latent representations of hypnotic depth trajectories. Given the trajectories drawn from the generative model, the planning policy infers a dose of propofol for stable sedation of a patient under total intravenous anesthesia (TIVA) using propofol and remifentanil. Through extensive evaluation, the DIAPG model can effectively stabilize bispectral index (BIS) and effect site concentration given a potentially time-varying target sequence. The proposed DIAPG shows an increased performance of 530% and 15% when a human expert and a standard reinforcement algorithm are used to infuse drugs, respectively.
10.1109/TNNLS.2022.3190379
Feasibility of intelligent drug control in the maintenance phase of general anesthesia based on convolutional neural network.
Heliyon
Background:The growth and aging process of the human population has accelerated the increase in surgical procedures. Yet, the demand for increasing operations can be hardly met since the training of anesthesiologists is usually a long-term process. Closed-loop artificial intelligence (AI) model provides the possibility to solve intelligent decision-making for anesthesia auxiliary control and, as such, has allowed breakthroughs in closed-loop control of clinical practices in intensive care units (ICUs). However, applying an open-loop artificial intelligence algorithm to build up personalized medication for anesthesia still needs to be further explored. Currently, anesthesiologists have selected doses of intravenously pumped anesthetic drugs mainly based on the blood pressure and bispectral index (BIS), which can express the depth of anesthesia. Unfortunately, BIS cannot be monitored at some medical centers or operational procedures and only be regulated by blood pressure. As a result, here we aim to inaugurally explore the feasibility of a basic intelligent control system applied to drug delivery in the maintenance phase of general anesthesia, based on a convolutional neural network model with open-loop design, according to AI learning of existing anesthesia protocols. Methods:A convolutional neural network, combined with both sliding window sampling method and residual learning module, was utilized to establish an "AI anesthesiologist" model for intraoperative dosing of personalized anesthetic drugs (propofol and remifentanil). The fitting degree and difference in pumping dose decision, between the AI anesthesiologist and the clinical anesthesiologist, for these personalized anesthetic drugs were examined during the maintenance phase of anesthesia. Results:The medication level established by the "AI anesthesiologist" was comparable to that obtained by the clinical anesthesiologist during the maintenance phase of anesthesia. Conclusion:The application of an open-loop decision-making plan by convolutional neural network showed that intelligent anesthesia control is consistent with the actual anesthesia control, thus providing possibility for further evolution and optimization of auxiliary intelligent control of depth of anesthesia.
10.1016/j.heliyon.2022.e12481
A Transformer-Based Prediction Method for Depth of Anesthesia During Target-Controlled Infusion of Propofol and Remifentanil.
IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society
Accurately predicting anesthetic effects is essential for target-controlled infusion systems. The traditional (PK-PD) models for Bispectral index (BIS) prediction require manual selection of model parameters, which can be challenging in clinical settings. Recently proposed deep learning methods can only capture general trends and may not predict abrupt changes in BIS. To address these issues, we propose a transformer-based method for predicting the depth of anesthesia (DOA) using drug infusions of propofol and remifentanil. Our method employs long short-term memory (LSTM) and gate residual network (GRN) networks to improve the efficiency of feature fusion and applies an attention mechanism to discover the interactions between the drugs. We also use label distribution smoothing and reweighting losses to address data imbalance. Experimental results show that our proposed method outperforms traditional PK-PD models and previous deep learning methods, effectively predicting anesthetic depth under sudden and deep anesthesia conditions.
10.1109/TNSRE.2023.3305363
Using the TI.VA algorithm to titrate the depth of general anaesthesia: a first-in-humans study.
BJA open
Background:The dose of anaesthetic and opioid drugs must be continuously adjusted after the induction of general anaesthesia to maintain an adequate depth of anaesthesia. The TI.VA algorithm is a multiple-input/multiple-output algorithm designed to optimise the balance between anaesthetic and opioid concentrations during general anaesthesia. It applies vector analysis to a two-dimensional matrix to quantify any inadequacy of the depth of anaesthesia at any given moment and determine any drug dose adjustments required to achieve an adequate depth of anaesthesia. This study aimed to capture preliminary data on the performance and safety of the TI.VA algorithm during total i.v. anaesthesia in patients. Methods:This prospective study enrolled nine patients with breast cancer scheduled to undergo surgery. General anaesthesia was induced under manual control using propofol and remifentanil. Anaesthesia was guided using the TI.VA algorithm from skin incision until surgical resection was completed. The quality of anaesthesia was assessed through an analysis of performance errors. A bispectral index global score (GS) <50 was considered an acceptable target for algorithm performance. Results:All nine procedures were completed without any adverse events and none of the patients recalled any intraoperative event. Overall, we analysed 3417 monitoring points corresponding to 285 min of surgery. All patients presented a GS below the cut-off value of 50. Conclusions:The TI.VA algorithm provides adequate control of clinical anaesthesia. A more sophisticated prototype needs to be developed before the trial is expanded to include larger patient populations. Clinical trial registration:NCT05199883.
10.1016/j.bjao.2023.100203
Response of the GE Entropy™ monitor to neuromuscular block in awake volunteers.
British journal of anaesthesia
BACKGROUND:The GE Entropy™ monitor analyses the frontal electroencephalogram (EEG) and generates two indices intended to represent the degree of anaesthetic drug effect on the brain. It is frequently used in the context of neuromuscular block. We have shown that a similar device, the Bispectral Index monitor (BIS), does not generate correct values in awake volunteers when neuromuscular blocking drugs are administered. METHODS:We replayed the EEGs recorded during awake paralysis from the original study to an Entropy monitor via a calibrated electronic playback system. Each EEG was replayed 30 times to evaluate the consistency of the Entropy output. RESULTS:Both State Entropy and Response Entropy decreased during periods of neuromuscular block to values consistent with anaesthesia, despite there being no change in conscious state (State Entropy <60 in eight of nine rocuronium trials and nine of 10 suxamethonium trials). Entropy values did not return to pre-test levels until after the return of movement. Entropy did not generate exactly the same results when the same EEG was replayed multiple times, which is primarily because of a cyclical state within the Entropy system itself. CONCLUSIONS:The GE Entropy™ monitor requires muscle activity to generate correct values in an awake subject. It could therefore be unreliable at detecting awareness in patients who have been given neuromuscular blocking drugs. In addition, Entropy does not generate the same result each time it is presented with the same EEG.
10.1016/j.bja.2023.08.013
Comparison of the bispectral indices of patients receiving remimazolam and propofol for general anesthesia: a randomized crossover trial.
Anaesthesia, critical care & pain medicine
BACKGROUND:Remimazolam is a safe and effective new benzodiazepine sedative that has unique advantages in anesthesia induction and maintenance. The differences in the electroencephalogram bispectral index (BIS) during general anesthesia between propofol and remimazolam deserve further exploration. METHODS:Single-center randomized crossover study. Patients who required multiple hysteroscopic surgery were randomly assigned to use remimazolam (0.27 mg/kg for induction and 1 mg/kg/h for maintenance) first and then propofol (2.0 mg/kg for induction and 6 mg/kg/h for maintenance) during hysteroscopic surgery again 3 months later, or in the opposite order. Both drugs were used at the latest ED for unconsciousness. The BIS values (primary endpoint), intraoperative conditions, and incidence of adverse reactions (secondary endpoints) were compared at each time point. BIS values were analyzed with a mixed model of repeated measurements (MMRM). RESULTS:Seventeen patients completed the study. The lowest BIS value in the remimazolam regimen was significantly higher than that in the propofol regimen (p = 0.001). The MMRM analysis of the BIS values revealed significant differences between the regimens at each time point (p < 0.001). The intraoperative diastolic blood pressure and heart rate changes were smaller, the recovery was faster, and there were fewer adverse reactions and less injection pain, but a greater incidence of intraoperative body movement and hiccups, in the remimazolam regimen. CONCLUSION:The trial indicated that remimazolam maintained a higher BIS level than propofol. The correlation between the BIS and the depth of anesthesia induced by remimazolam needs to be further studied. TRIAL REGISTRATION:This trial is registered at ClinicalTrials.gov: ChiCTR2200064551.
10.1016/j.accpm.2024.101377
Bispectral index-guided comparison of dexmedetomidine and fentanyl as an adjuvant with propofol to achieve an adequate depth for endotracheal intubation - A double-blind randomised controlled trial.
Indian journal of anaesthesia
Background and Aims:Laryngoscopy and tracheal intubation require an adequate depth of anaesthesia. The study's primary objective was to compare the time needed to achieve the bispectral index (BIS)-guided adequate depth of anaesthesia for endotracheal intubation using fentanyl and dexmedetomidine. Methods:After institutional ethics committee clearance and written informed consent, this randomised study was conducted on 140 patients of either gender between 18 and 60 years who were scheduled for elective surgeries under general anaesthesia. Patients were randomised to intravenous dexmedetomidine 1 μg/kg (Group D) or fentanyl 2 μg/kg (Group F). The drugs were given as an intravenous infusion over 10 min before induction of anaesthesia. The primary outcome was the time required to achieve BIS 50. Normally distributed variables were compared using Student's test, and non-normally distributed variables were compared using the Mann-Whitney U test. Qualitative data were analysed using Chi-square/Fisher's exact test. A value <0.05 was considered significant. Results:The time to achieve BIS 50 was lesser in Group F, 1546 (27) as compared to Group D, 1558 (11) s [mean difference (95% confidence interval (CI) 12[5.11, 18.89]), < 0.001]. Haemodynamic parameters were comparable at all time points between both the groups, except heart rate, which was significantly lower. Propofol consumption was significantly less in group D than in group F [125.9 (25.36) versus 157.3 (42.80) mg, respectively, mean difference (95% CI) 31.4 (-44.16 to -20.63) < 0.001)]. Conclusion:Dexmedetomidine achieves BIS 50 faster and has a propofol-sparing effect as compared to fentanyl.
10.4103/ija.ija_884_23
Age-dependent cross frequency coupling features from children to adults during general anesthesia.
Liang Zhenhu,Ren Na,Wen Xin,Li Haiwen,Guo Hang,Ma Yaqun,Li Zheng,Li Xiaoli
NeuroImage
BACKGROUND:The frequency coupling characteristics in electroencephalogram (EEG) induced by anesthetics have been well studied in adults, but the investigation of the age-dependent cross frequency coupling features from children to adults is still lacking. METHODS:We analyzed EEG signals recorded from pediatric to adult patients (n = 131), separated into six age groups: <1 year (n = 15), 1-3 years (n = 23), 3-6 years (n = 19), 6-12 years (n = 18), 12-18 years (n = 16), and 18-45 years (n = 40). Age related EEG power and cross frequency coupling analysis (phase amplitude coupling (PAC) and quadratic phase coupling) of data from maintenance of a surgical state of anesthesia (MOSSA) was conducted. Also, for patients of ages less than 6 years, we analyzed the performance of cross frequency coupling derived indices in distinguishing the states of wakefulness, MOSSA, and recovery of consciousness (ROC). RESULTS:(1) During MOSSA, EEG power substantially increased with age from infancy to 3-6 years then decreased with age in the theta-gamma frequency bands. The infant group (<1 year) had the highest slow oscillation (SO) power among all age groups. (2) The distinct PAC pattern is absent in patients less than 1 year of age both in SO-alpha and delta-alpha frequency band coupling during propofol induced unconsciousness. The modulation index between delta and alpha oscillations in MOSSA increased with age. (3) Wavelet bicoherence derived indices reach their peaks in the 3-6 years group and then decrease with age growth. (4) The Diag_En index (normalized entropy of the diagonal bicoherence entries of the bicoherence matrix) performed the best at distinguishing different states for ages less than 6 years (p<0.05). CONCLUSIONS:The combination of propofol induction and sevoflurane maintenance exhibited age-dependent EEG power spectra, PAC, and bicoherence, likely related to brain development. These observations suggest new rules for infant and child brain state monitoring during general anesthesia are needed.
10.1016/j.neuroimage.2021.118372
Tracking the effects of propofol, sevoflurane and (S)-ketamine anesthesia using an unscented Kalman filter-based neural mass model.
Journal of neural engineering
. Neural mass model (NMM) has been widely used to investigate the neurophysiological mechanisms of anesthetic drugs induced general anesthesia (GA). However, whether the parameters of NMM could track the effects of anesthesia still unknown.We proposed using the cortical NMM (CNMM) to infer the potential neurophysiological mechanism of three different anesthetic drugs (i.e. propofol, sevoflurane, and (S)-ketamine) induced GA, and we employed unscented Kalman filter (UKF) to track any change in raw electroencephalography (rEEG) in frontal area during GA. We did this by estimating the parameters of population gain [i.e. excitatory/inhibitory postsynaptic potential (EPSP/IPSP, i.e. parameter/in CNMM) and the time constant rate of EPSP/IPSP (i.e. parameter/in CNMM). We compared the rEEG and simulated EEG (sEEG) from the perspective of spectrum, phase-amplitude coupling (PAC), and permutation entropy (PE).. Under three estimated parameters (i.e., andfor propofol/sevoflurane orfor (S)-ketamine), the rEEG and sEEG had similar waveforms, time-frequency spectra, and PAC patterns during GA for the three drugs. The PE curves derived from rEEG and sEEG had high correlation coefficients (propofol: 0.97 ± 0.03, sevoflurane: 0.96 ± 0.03, (S)-ketamine: 0.98 ± 0.02) and coefficients of determination () (propofol: 0.86 ± 0.03, sevoflurane: 0.68 ± 0.30, (S)-ketamine: 0.70 ± 0.18). Except for parameterfor sevoflurane, the estimated parameters for each drug in CNMM can differentiate wakefulness and non-wakefulness states. Compared with the simulation of three estimated parameters, the UKF-based CNMM had lower tracking accuracy under the simulation of four estimated parameters (i.e.and) for three drugs.The results demonstrate that a combination of CNMM and UKF could track the neural activities during GA. The EPSP/IPSP and their time constant rate can interpret the anesthetic drug's effect on the brain, and can be used as a new index for depth of anesthesia monitoring.
10.1088/1741-2552/acc2e8
Application of Fast Perturbational Complexity Index to the Diagnosis and Prognosis for Disorders of Consciousness.
Wang Yong,Niu Zikang,Xia Xiaoyu,Bai Yang,Liang Zhenhu,He Jianghong,Li Xiaoli
IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society
OBJECTIVE:Diagnosis and prognosis of patients with disorders of consciousness (DOC) is a challenge for neuroscience and clinical practice. Transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) is an effective tool to measure the level of consciousness. However, a scientific and accurate method to quantify TMS-evoked activity is still lacking. This study applied fast perturbational complexity index (PCIst) to the diagnosis and prognosis of DOC patients. METHODS:TMS-EEG data of 30 normal healthy participants (NOR) and 181 DOC patients were collected. The PCIst was used to assess the time-space complexity of TMS-evoked potentials (TEP). We selected parameters of PCIst in terms of data length, data delay, sampling rate and frequency band. In addition, we collected Coma Recovery Scale-Revised (CRS-R) values for 114 DOC patients after one year. Finally, we trained the classification and regression model. RESULTS:1) PCIst shows the differences among NOR, minimally consciousness state (MCS) and unresponsive wakefulness syndrome (UWS) and has low computational cost. 2) Optimal parameters of data length and delay after TMS are 300 ms and 101-300 ms. Significant differences of PCIst at 5-8 Hz and 9-12 Hz bands are found among NOR, MCS and UWS groups. PCIst still works when TEP is down-sampled to 250 Hz. 3) PCIst at 9-12 Hz shows the highest performance in diagnosis and prognosis of DOC. CONCLUSIONS:This study confirms that PCIst can quantify the level of consciousness. PCIst is a potential measure for the diagnosis and prognosis of DOC patients.
10.1109/TNSRE.2022.3154772
EEG Changes during Propofol Anesthesia Induction in Vegetative State Patients Undergoing Spinal Cord Stimulation Implantation Surgery.
Brain sciences
OBJECTIVE:To compare the EEG changes in vegetative state (VS) patients and non-craniotomy, non-vegetative state (NVS) patients during general anesthesia with low-dose propofol and to find whether it affects the arousal rate of VS patients. METHODS:Seven vegetative state patients (VS group: five with traumatic brain injury, two with ischemic-hypoxic VS) and five non-craniotomy, non-vegetative state patients (NVS group) treated in the Department of Neurosurgery, Peking University International Hospital from January to May 2022 were selected. All patients were induced with 0.5 mg/kg propofol, and the Bispectral Index (BIS) changes within 5 min after administration were observed. Raw EEG signals and perioperative EEG signals were collected and analyzed using EEGLAB in the MATLAB software environment, time-frequency spectrums were calculated, and EEG changes were analyzed using power spectrums. RESULTS:There was no significant difference in the general data before surgery between the two groups ( > 0.05); the BIS reduction in the VS group was significantly greater than that in the NVS group at 1 min, 2 min, 3 min, 4 min, and 5 min after 0.5 mg/kg propofol induction ( < 0.05). Time-frequency spectrum analysis showed the following: prominent α band energy around 10 Hz and decreased high-frequency energy in the NVS group, decreased high-frequency energy and main energy concentrated below 10 Hz in traumatic brain injury VS patients, higher energy in the 10-20 Hz band in ischemic-hypoxic VS patients. The power spectrum showed that the brain electrical energy of the NVS group was weakened R5 min after anesthesia induction compared with 5 min before induction, mainly concentrated in the small wave peak after 10 Hz, i.e., the α band peak; the energy of traumatic brain injury VS patients was weakened after anesthesia induction, but no α band peak appeared; and in ischemic-hypoxic VS patients, there was no significant change in low-frequency energy after anesthesia induction, high-frequency energy was significantly weakened, and a clear α band peak appeared slightly after 10 Hz. Three months after the operation, follow-up visits were made to the VS group patients who had undergone SCS surgery. One patient with traumatic brain injury VS was diagnosed with MCS-, one patient with ischemic-hypoxic VS had increased their CRS-R score by 1 point, and the remaining five patients had no change in their CRS scores. CONCLUSIONS:Low doses of propofol cause great differences in the EEG of different types of VS patients, which may be the unique response of damaged nerve cell residual function to propofol, and these weak responses may also be the basis of brain recovery.
10.3390/brainsci13111608
The Characteristics of Electroencephalogram Signatures in Minimally Conscious State Patients Induced by General Anesthesia.
IEEE transactions on bio-medical engineering
OBJECTIVE:General anesthesia (GA) is necessary for surgery, even for patients in a minimally conscious state (MCS). The characteristics of the electroencephalogram (EEG) signatures of the MCS patients under GA are still unclear. METHODS:The EEG during GA were recorded from 10 MCS patients undergoing spinal cord stimulation surgery. The power spectrum, phase-amplitude coupling (PAC), the diversity of connectivity, and the functional network were investigated. Long term recovery was assessed by the Coma Recovery Scale-Revised at one year after the surgery, and the characteristics of the patients with good or bad prognosis status were compared. RESULTS:For the four MCS patients with good prognostic recovery, slow oscillation (0.1-1 Hz) and the alpha band (8-12 Hz) in the frontal areas increased during the maintenance of a surgical state of anesthesia (MOSSA), and "peak-max" and "trough-max" patterns emerged in frontal and parietal areas. During MOSSA, the six MCS patients with bad prognosis demonstrated: increased modulation index, reduced diversity of connectivity (from mean±SD of 0.877 ± 0.003 to 0.776 ± 0.003, p < 0.001), reduced function connectivity significantly in theta band (from mean±SD of 1.032 ± 0.043 to 0.589 ± 0.036, p < 0.001, in prefrontal-frontal; and from mean±SD of 0.989 ± 0.043 to 0.684 ± 0.036, p < 0.001, in frontal-parietal) and reduced local and global efficiency of the network in delta band. CONCLUSIONS:A bad prognosis in MCS patients is associated with signs of impaired thalamocortical and cortico-cortical connectivity - as indicated by inability to produce inter-frequency coupling and phase synchronization. These indices may have a role in predicting the long-term recovery of MCS patients.
10.1109/TBME.2023.3287203
Information Integration and Mesoscopic Cortical Connectivity during Propofol Anesthesia.
Liang Zhenhu,Cheng Lei,Shao Shuai,Jin Xing,Yu Tao,Sleigh Jamie W,Li Xiaoli
Anesthesiology
BACKGROUND:The neurophysiologic mechanisms of propofol-induced loss of consciousness have been studied in detail at the macro (scalp electroencephalogram) and micro (spiking or local field potential) scales. However, the changes in information integration and cortical connectivity during propofol anesthesia at the mesoscopic level (the cortical scale) are less clear. METHODS:The authors analyzed electrocorticogram data recorded from surgical patients during propofol-induced unconsciousness (n = 9). A new information measure, genuine permutation cross mutual information, was used to analyze how electrocorticogram cross-electrode coupling changed with electrode-distances in different brain areas (within the frontal, parietal, and temporal regions, as well as between the temporal and parietal regions). The changes in cortical networks during anesthesia-at nodal and global levels-were investigated using clustering coefficient, path length, and nodal efficiency measures. RESULTS:In all cortical regions, and in both wakeful and unconscious states (early and late), the genuine permutation cross mutual information and the percentage of genuine connections decreased with increasing distance, especially up to about 3 cm. The nodal cortical network metrics (the nodal clustering coefficients and nodal efficiency) decreased from wakefulness to unconscious state in the cortical regions we analyzed. In contrast, the global cortical network metrics slightly increased in the early unconscious state (the time span from loss of consciousness to 200 s after loss of consciousness), as compared with wakefulness (normalized average clustering coefficient: 1.05 ± 0.01 vs. 1.06 ± 0.03, P = 0.037; normalized average path length: 1.02 ± 0.01 vs. 1.04 ± 0.01, P = 0.021). CONCLUSIONS:The genuine permutation cross mutual information reflected propofol-induced coupling changes measured at a cortical scale. Loss of consciousness was associated with a redistribution of the pattern of information integration; losing efficient global information transmission capacity but increasing local functional segregation in the cortical network.
10.1097/ALN.0000000000003015
Propofol modulates neural dynamics of thalamo-cortical system associated with anesthetic levels in rats.
Cognitive neurodynamics
The thalamocortical system plays an important role in consciousness. How anesthesia modulates the thalamocortical interactions is not completely known. We simultaneously recorded local field potentials(LFPs) in thalamic reticular nucleus(TRN) and ventroposteromedial thalamic nucleus(VPM), and electrocorticographic(ECoG) activities in frontal and occipital cortices in freely moving rats ( = 11). We analyzed the changes in thalamic and cortical local spectral power and connectivities, which were measured with phase-amplitude coupling (PAC), coherence and multivariate Granger causality, at the states of baseline, intravenous infusion of propofol 20, 40, 80 mg/kg/h and after recovery of righting reflex. We found that propofol-induced burst-suppression results in a synchronous decrease of spectral power in thalamus and cortex ( < 0.001 for all frequency bands). The cross-frequency PAC increased by propofol, characterized by gradually stronger 'trough-max' pattern in TRN and stronger 'peak-max' pattern in cortex. The cross-region PAC increased in the phase of TRN modulating the amplitude of cortex. The functional connectivity (FC) between TRN and cortex for α/β bands also significantly increased (< 0.040), with increased directional connectivity from TRN to cortex under propofol anesthesia. In contrast, the corticocortical FC significantly decreased ( < 0.047), with decreased directional connectivity from frontal cortex to occipital cortex. However, the thalamothalamic functional and directional connectivities remained largely unchanged by propofol anesthesia. The spectral powers and connectivities are differentially modulated with the changes of propofol doses, suggesting the changes in neural dynamics in thalamocortical system could be used for distinguishing different vigilance levels caused by propofol. Supplementary Information:The online version contains supplementary material available at 10.1007/s11571-022-09912-0.
10.1007/s11571-022-09912-0
Monitoring anesthesia using simultaneous functional Near Infrared Spectroscopy and Electroencephalography.
Vijayakrishnan Nair Vidhya,Kish Brianna R,Yang Ho-Ching Shawn,Yu Zhenyang,Guo Hang,Tong Yunjie,Liang Zhenhu
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology
OBJECTIVE:This study aims to understand the neural and hemodynamic responses during general anesthesia in order to develop a comprehensive multimodal anesthesia depth monitor using simultaneous functional Near Infrared Spectroscopy (fNIRS) and Electroencephalogram (EEG). METHODS:37 adults and 17 children were monitored with simultaneous fNIRS and EEG, during the complete general anesthesia process. The coupling of fNIRS signals with neuronal signals (EEG) was calculated. Measures of complexity (sample entropy) and phase difference were also quantified from fNIRS signals to identify unique fNIRS based biomarkers of general anesthesia. RESULTS:A significant decrease in the complexity and power of fNIRS signals characterize the anesthesia maintenance phase. Furthermore, responses to anesthesia vary between adults and children in terms of neurovascular coupling and frontal EEG alpha power. CONCLUSIONS:This study shows that fNIRS signals could reliably quantify the underlying neuronal activity under general anesthesia and clearly distinguish the different phases throughout the procedure in adults and children (with less accuracy). SIGNIFICANCE:A multimodal approach incorporating the specific differences between age groups, provides a reliable measure of anesthesia depth.
10.1016/j.clinph.2021.03.025
Propofol Anesthesia Decreased the Efficiency of Long-Range Cortical Interaction in Humans.
Liang Zhenhu,Jin Xing,Ren Ye,Yu Tao,Li Xiaoli
IEEE transactions on bio-medical engineering
OBJECTIVE:Phase-amplitude coupling (PAC) has recently been used to illuminate cross-frequency coordination in neurophysiological activity of electroencephalogram. However, the PAC at a meso-scale (electrocorticogram, ECoG) and PAC between different areas have still not been fully clarified. METHODS:In this study, we analyzed ECoG data recorded from surgical patients (n = 9) with pharmaco-resistant epilepsy during the surgical treatment. The modulogram and a genuine modulation index, based on a Kullback-Leibler distance and permutation test method, were developed and used to measure the slow oscillation (SO) (0.15-1 Hz)-α (8-13 Hz) PAC of within-lead and cross-lead during transitions from states of wakefulness to unconsciousness during propofol induced general anesthesia. RESULTS:In within-lead SO-α PAC, the modulation index increased in the unconscious state (p < 0.05, Tukey's test), the percentages of genuine modulation indices also increased in the unconscious state (p < 0.001 in the frontal area and p < 0.01 in the parietal area), and distinct PAC patterns emerged more often. In cross-lead SO-α PAC, there are fewer PAC patterns compared to within-lead, and the percentages of genuine modulation indices decreased significantly (p < 0.001). CONCLUSION:The increased modulation index of within-lead and cross-lead SO-α PAC is associated with a reduction of information integration and the efficiency of long distance synchronization. These findings demonstrate that the propofol causes the neuronal populations to enter a 'busy' state in a local scale, which prevents the information integration in long-range areas.
10.1109/TBME.2021.3090027
Age-dependent neurovascular coupling characteristics in children and adults during general anesthesia.
Biomedical optics express
General anesthesia is an indispensable procedure in clinical practice. Anesthetic drugs induce dramatic changes in neuronal activity and cerebral metabolism. However, the age-related changes in neurophysiology and hemodynamics during general anesthesia remain unclear. Therefore, the objective of this study was to explore the neurovascular coupling between neurophysiology and hemodynamics in children and adults during general anesthesia. We analyzed frontal electroencephalogram (EEG) and functional near-infrared spectroscopy (fNIRS) signals recorded from children (6-12 years old, n = 17) and adults (18-60 years old, n = 25) during propofol-induced and sevoflurane-maintained general anesthesia. The neurovascular coupling was evaluated in wakefulness, maintenance of a surgical state of anesthesia (MOSSA), and recovery by using correlation, coherence and Granger-causality (GC) between the EEG indices [EEG power in different bands and permutation entropy (PE)], and hemodynamic responses the oxyhemoglobin (Δ[HbO]) and deoxy-hemoglobin (Δ[Hb]) from fNIRS in the frequency band in 0.01-0.1 Hz. The PE and Δ[Hb] performed well in distinguishing the anesthesia state (p > 0.001). The correlation between PE and Δ[Hb] was higher than those of other indices in the two age groups. The coherence significantly increased during MOSSA (p < 0.05) compared with wakefulness, and the coherences between theta, alpha and gamma, and hemodynamic activities of children are significantly stronger than that of adults' bands. The GC from neuronal activities to hemodynamic responses decreased during MOSSA, and can better distinguish anesthesia state in adults. Propofol-induced and sevoflurane-maintained combination exhibited age-dependent neuronal activities, hemodynamics, and neurovascular coupling, which suggests the need for separate rules for children's and adults' brain states monitoring during general anesthesia.
10.1364/BOE.482127
Emergence EEG pattern classification in sevoflurane anesthesia.
Liang Zhenhu,Huang Cheng,Li Yongwang,Hight Darren F,Voss Logan J,Sleigh Jamie W,Li Xiaoli,Bai Yang
Physiological measurement
OBJECTIVE:Significant spectral electroencephalogram (EEG) pattern characteristics exist in individual patients during the re-establishment of consciousness after general anesthesia. However, these EEG patterns cannot be quantitatively identified using commercially available depth of anesthesia (DoA) monitors. This study proposes an effective classification method and indices to classify these patterns among patients. APPROACH:Four types of emergence EEG patterns were identified based on the EEG data set from 52 patients undergoing sevoflurane general anesthesia from two hospitals. Then, the relative power spectrum density (RPSD) of five frequency sub-bands of clinical interest (delta, theta, alpha, beta and gamma) were selected for emergence state analysis. Finally, a genetic algorithm support vector machine (GA-SVM) was used to identify the emergence EEG patterns. The performance was reported in terms of sensitivity (SE), specificity (SP) and accuracy (AC). MAIN RESULTS:The combination of the mean and mode of RPSD in the delta and alpha band (P (delta)/P (alpha) performed the best in the GA-SVM classification. The AC indices obtained by GA-SVM across the four patterns were 90.64 ± 7.61, 81.79 ± 5.84, 82.14 ± 7.99 and 72.86 ± 11.11 respectively. Furthermore, the emergence time of the patients with EEG emergence patterns I and III increased as the patients' age increased. However, for patients with EEG emergence pattern IV, the emergence time positively correlates with the patients' age when they are under 50, and negatively correlates with it when they are over 50. SIGNIFICANCE:The mean and mode of P (delta)/P (alpha) is a useful index to classify the different emergence EEG patterns. In addition, these patterns may correlate with an underlying neural substrate which is related to the patients' age. Highlights ► Four emergence EEG patterns were found in γ-amino-butyric acid (GABA)-ergic anesthetic drugs. ► A genetic algorithm combined with a support vector machine (GA-SVM) was proposed to identify the emergence EEG patterns. ► The relative power spectrum density (RPSD) was used as a feature to classify the emergence EEG patterns and good accuracy was achieved. ► The statistics shows that the emergence EEG patterns are age-related and may have value in assessing postoperative brain states.
10.1088/1361-6579/aab4d0
EEG entropy measures in anesthesia.
Liang Zhenhu,Wang Yinghua,Sun Xue,Li Duan,Voss Logan J,Sleigh Jamie W,Hagihira Satoshi,Li Xiaoli
Frontiers in computational neuroscience
HIGHLIGHTS:► Twelve entropy indices were systematically compared in monitoring depth of anesthesia and detecting burst suppression.► Renyi permutation entropy performed best in tracking EEG changes associated with different anesthesia states.► Approximate Entropy and Sample Entropy performed best in detecting burst suppression. OBJECTIVE:Entropy algorithms have been widely used in analyzing EEG signals during anesthesia. However, a systematic comparison of these entropy algorithms in assessing anesthesia drugs' effect is lacking. In this study, we compare the capability of 12 entropy indices for monitoring depth of anesthesia (DoA) and detecting the burst suppression pattern (BSP), in anesthesia induced by GABAergic agents. METHODS:Twelve indices were investigated, namely Response Entropy (RE) and State entropy (SE), three wavelet entropy (WE) measures [Shannon WE (SWE), Tsallis WE (TWE), and Renyi WE (RWE)], Hilbert-Huang spectral entropy (HHSE), approximate entropy (ApEn), sample entropy (SampEn), Fuzzy entropy, and three permutation entropy (PE) measures [Shannon PE (SPE), Tsallis PE (TPE) and Renyi PE (RPE)]. Two EEG data sets from sevoflurane-induced and isoflurane-induced anesthesia respectively were selected to assess the capability of each entropy index in DoA monitoring and BSP detection. To validate the effectiveness of these entropy algorithms, pharmacokinetic/pharmacodynamic (PK/PD) modeling and prediction probability (Pk) analysis were applied. The multifractal detrended fluctuation analysis (MDFA) as a non-entropy measure was compared. RESULTS:All the entropy and MDFA indices could track the changes in EEG pattern during different anesthesia states. Three PE measures outperformed the other entropy indices, with less baseline variability, higher coefficient of determination (R (2)) and prediction probability, and RPE performed best; ApEn and SampEn discriminated BSP best. Additionally, these entropy measures showed an advantage in computation efficiency compared with MDFA. CONCLUSION:Each entropy index has its advantages and disadvantages in estimating DoA. Overall, it is suggested that the RPE index was a superior measure. Investigating the advantages and disadvantages of these entropy indices could help improve current clinical indices for monitoring DoA.
10.3389/fncom.2015.00016
The EEG complexity, information integration and brain network changes in minimally conscious state patients during general anesthesia.
Journal of neural engineering
General anesthesia (GA) can induce reversible loss of consciousness. Nonetheless, the electroencephalography (EEG) characteristics of patients with minimally consciousness state (MCS) during GA are seldom observed.We recorded EEG data from nine MCS patients during GA. We used the permutation Lempel-Ziv complexity (PLZC), permutation fluctuation complexity (PFC) to quantify the type I and II complexities. Additionally, we used permutation cross mutual information (PCMI) and PCMI-based brain network to investigate functional connectivity and brain networks in sensor and source spaces.Compared to the preoperative resting state, during the maintenance of surgical anesthesia state, PLZC decreased (< 0.001), PFC increased (< 0.001) and PCMI decreased (< 0.001) in sensor space. The results for these metrics in source space are consistent with sensor space. Additionally, node network indicators nodal clustering coefficient (NCC) (< 0.001) and nodal efficiency (NE) (< 0.001) decreased in these two spaces. Global network indicators normalized average path length (Lave/Lr) (< 0.01) and modularity () (< 0.05) only decreased in sensor space, while the normalized average clustering coefficient (Cave/Cr) and small-world index (σ) did not change significantly. Moreover, the dominance of hub nodes is reduced in frontal regions in these two spaces. After recovery of consciousness, PFC decreased in the two spaces, while PLZC, PCMI increased. NCC, NE, and frontal region hub node dominance increased only in the sensor space. These indicators did not return to preoperative levels. In contrast, global network indicatorsLave/Lrandwere not significantly different from the preoperative resting state in sensor space.GA alters the complexity of the EEG, decreases information integration, and is accompanied by a reconfiguration of brain networks in MCS patients. The PLZC, PFC, PCMI and PCMI-based brain network metrics can effectively differentiate the state of consciousness of MCS patients during GA.
10.1088/1741-2552/ad12dc
Age-dependent coupling characteristics of bilateral frontal EEG during desflurane anesthesia.
Physiological measurement
The purpose of this study is to investigate the age dependence of bilateral frontal electroencephalogram (EEG) coupling characteristics, and find potential age-independent depth of anesthesia monitoring indicators for the elderlies.We recorded bilateral forehead EEG data from 41 patients (ranged in 19-82 years old), and separated into three age groups: 18-40 years (= 12); 40-65 years (= 14), >65 years (= 15). All these patients underwent desflurane maintained general anesthesia (GA). We analyzed the age-related EEG spectra, phase amplitude coupling (PAC), coherence and phase lag index (PLI) of EEG data in the states of awake, GA, and recovery.The frontal alpha power shows age dependence in the state of GA maintained by desflurane. Modulation index in slow oscillation-alpha and delta-alpha bands showed age dependence and state dependence in varying degrees, the PAC pattern also became less pronounced with increasing age. In the awake state, the coherence in delta, theta and alpha frequency bands were all significantly higher in the >65 years age group than in the 18-40 years age group (< 0.05 for three frequency bands). The coherence in alpha-band was significantly enhanced in all age groups in GA (< 0.01) and then decreased in recovery state. Notably, the PLI in the alpha band was able to significantly distinguish the three states of awake, GA and recovery (< 0.01) and the results of PLI in delta and theta frequency bands had similar changes to those of coherence.We found the EEG coupling and synchronization between bilateral forehead are age-dependent. The PAC, coherence and PLI portray this age-dependence. The PLI and coherence based on bilateral frontal EEG functional connectivity measures and PAC based on frontal single-channel are closely associated with anesthesia-induced unconsciousness.
10.1088/1361-6579/ad46e0
Evaluation of brain function in adult patent ductus arteriosus surgery: A multimodal monitoring approach.
Current problems in cardiology
Adult patent ductus arteriosus (PDA) repair surgery often involves hypothermic cardiopulmonary bypass (CPB) and is associated with postoperative neurological complications. Our study evaluates brain function during PDA surgery using regional cerebral oxygen saturation (rSO) and bispectral index (BIS) monitoring to mitigate these complications. Patients were categorized into moderate (26-31 ℃) and mild (32-35 ℃) hypothermia groups. Findings indicate a positive correlation between PDA diameter and pulmonary artery systolic blood pressure, and a strong correlation between delirium and average rSO2-AUC. The mild hypothermia group had longer extubation and hospitalization times. During CPB, rSO levels fluctuated significantly, and EEG analysis revealed changes in brain wave patterns. One case of nerve injury in the mild hypothermia group showed incomplete recovery after a year. Our results advocate for moderate hypothermia during CPB in adult PDA repair, suggesting that combined rSO and BIS monitoring can reduce neurological complications post-surgery.
10.1016/j.cpcardiol.2023.102334
The applied principles of EEG analysis methods in neuroscience and clinical neurology.
Military Medical Research
Electroencephalography (EEG) is a non-invasive measurement method for brain activity. Due to its safety, high resolution, and hypersensitivity to dynamic changes in brain neural signals, EEG has aroused much interest in scientific research and medical fields. This article reviews the types of EEG signals, multiple EEG signal analysis methods, and the application of relevant methods in the neuroscience field and for diagnosing neurological diseases. First, three types of EEG signals, including time-invariant EEG, accurate event-related EEG, and random event-related EEG, are introduced. Second, five main directions for the methods of EEG analysis, including power spectrum analysis, time-frequency analysis, connectivity analysis, source localization methods, and machine learning methods, are described in the main section, along with different sub-methods and effect evaluations for solving the same problem. Finally, the application scenarios of different EEG analysis methods are emphasized, and the advantages and disadvantages of similar methods are distinguished. This article is expected to assist researchers in selecting suitable EEG analysis methods based on their research objectives, provide references for subsequent research, and summarize current issues and prospects for the future.
10.1186/s40779-023-00502-7
Changes in information integration and brain networks during propofol-, dexmedetomidine-, and ketamine-induced unresponsiveness.
British journal of anaesthesia
BACKGROUND:Information integration and network science are important theories for quantifying consciousness. However, whether these theories propose drug- or conscious state-related changes in EEG during anaesthesia-induced unresponsiveness remains unknown. METHODS:A total of 72 participants were randomised to receive i.v. infusion of propofol, dexmedetomidine, or ketamine at a constant infusion rate until loss of responsiveness. High-density EEG was recorded during the consciousness transition from the eye-closed baseline to the unresponsiveness state and then to the recovery of the responsiveness state. Permutation cross mutual information (PCMI) and PCMI-based brain networks in broadband (0.1-45 Hz) and sub-band frequencies were used to analyse drug- and state-related EEG signature changes. RESULTS:PCMI and brain networks exhibited state-related changes in certain brain regions and frequency bands. The within-area PCMI of the frontal, parietal, and occipital regions, and the between-area PCMI of the parietal-occipital region (median [inter-quartile ranges]), baseline vs unresponsive were as follows: 0.54 (0.46-0.58) vs 0.46 (0.40-0.50), 0.58 (0.52-0.60) vs 0.48 (0.44-0.53), 0.54 (0.49-0.59) vs 0.47 (0.42-0.52) decreased during anaesthesia for three drugs (P<0.05). Alpha PCMI in the frontal region, and gamma PCMI in the posterior area significantly decreased in the unresponsive state (P<0.05). The frontal, parietal, and occipital nodal clustering coefficients and parietal nodal efficiency decreased in the unresponsive state (P<0.05). The increased normalised path length in delta, theta, and gamma bands indicated impaired global integration (P<0.05). CONCLUSIONS:The three anaesthetics caused changes in information integration patterns and network functions. Thus, it is possible to build a quantifying framework for anaesthesia-induced conscious state changes on the EEG scale using PCMI and network science.
10.1016/j.bja.2023.11.033
State-related Electroencephalography Microstate Complexity during Propofol- and Esketamine-induced Unconsciousness.
Anesthesiology
BACKGROUND:Identifying the state-related "neural correlates of consciousness" for anesthetics-induced unconsciousness is challenging. Spatiotemporal complexity is a promising tool for investigating consciousness. The authors hypothesized that spatiotemporal complexity may serve as a state-related but not drug-related electroencephalography (EEG) indicator during an unconscious state induced by different anesthetic drugs (e.g., propofol and esketamine). METHODS:The authors recorded EEG from patients with unconsciousness induced by propofol (n = 10) and esketamine (n = 10). Both conventional microstate parameters and microstate complexity were analyzed. Spatiotemporal complexity was constructed by microstate sequences and complexity measures. Two different EEG microstate complexities were proposed to quantify the randomness (type I) and complexity (type II) of the EEG microstate series during the time course of the general anesthesia. RESULTS:The coverage and occurrence of microstate E (prefrontal pattern) and the duration of microstate B (right frontal pattern) could distinguish the states of preinduction wakefulness, unconsciousness, and recovery under both anesthetics. Type I EEG microstate complexity based on mean information gain significantly increased from awake to unconsciousness state (propofol: from mean ± SD, 1.562 ± 0.059 to 1.672 ± 0.023, P < 0.001; esketamine: 1.599 ± 0.051 to 1.687 ± 0.013, P < 0.001), and significantly decreased from unconsciousness to recovery state (propofol: 1.672 ± 0.023 to 1.537 ± 0.058, P < 0.001; esketamine: 1.687 ± 0.013 to 1.608 ± 0.028, P < 0.001) under both anesthetics. In contrast, type II EEG microstate fluctuation complexity significantly decreased in the unconscious state under both drugs (propofol: from 2.291 ± 0.771 to 0.782 ± 0.163, P < 0.001; esketamine: from 1.645 ± 0.417 to 0.647 ± 0.252, P < 0.001), and then increased in the recovery state (propofol: 0.782 ± 0.163 to 2.446 ± 0.723, P < 0.001; esketamine: 0.647 ± 0.252 to 1.459 ± 0.264, P < 0.001). CONCLUSIONS:Both type I and type II EEG microstate complexities are drug independent. Thus, the EEG microstate complexity measures that the authors proposed are promising tools for building state-related neural correlates of consciousness to quantify anesthetic-induced unconsciousness. EDITOR’S PERSPECTIVE:
10.1097/ALN.0000000000004896