Phase lag entropy as a hypnotic depth indicator during propofol sedation

Comparative Analysis of the Performance of Electroencephalogram Parameters for Monitoring the Depth of Sedation During Remimazolam Target-Controlled Infusion

BACKGROUND

The changes in hypnotic indicators in remimazolam sedation remain unclear. We investigated the correlation of the electroencephalogram (EEG) parameters with the effect-site remimazolam concentration and the depth of sedation in patients receiving a target-controlled infusion of remimazolam.

METHODS

This prospective observational study enrolled 35 patients (32 analyzed) who underwent lower extremity varicose vein surgery or lower extremity orthopedic surgery under spinal anesthesia. We administered remimazolam by target-controlled infusion using the pharmacokinetic model introduced by Schüttler et al. The EEG data were continuously recorded, including the bispectral index (BIS), patient state index (PSI), spectral edge frequency (SEF), and raw EEG signals. The relative beta ratio (RBR), defined as log (spectral power [30-47 Hz]/spectral power [11-20 Hz]), was obtained by analyzing raw EEG. The level of sedation corresponding to each effect-site remimazolam concentration was assessed using the Modified Observer's Assessment of Alertness/Sedation (MOAA/S). The prediction probability (Pk) and Spearman's correlation coefficients (R) were calculated between effect-site remimazolam concentration, MOAA/S, and EEG parameters.

RESULTS

BIS and PSI showed significantly higher Pk for effect-site remimazolam concentration (Pk = 0.76 [0.72-0.79], P < .001 for BIS; Pk = 0.76 [0.73-0.79], P < .001 for PSI) compared to RBR (Pk = 0.71 [0.68-0.74], P < .001) and SEF (Pk = 0.58 [0.53-0.63], P = .002). BIS, PSI, and RBR showed significantly higher correlation coefficients for effect-site remimazolam concentration (R = -0.70 [-0.78 to -0.63], P < .001 for BIS; R = -0.72 [-0.79 to -0.66], P < .001 for PSI; R = -0.61 [-0.69 to -0.54], P < .001 for RBR) compared to SEF (R = -0.22 [-0.36 to -0.08], P = .002). BIS and PSI also had significantly higher Pk and correlation coefficients for MOAA/S (Pk = 0.81 [0.79-0.83], P < .001; R = 0.84 [0.81-0.88], P < .001 for BIS) (Pk = 0.80 [0.78-0.83], P < .001; R = 0.82 [0.78-0.87], P < .001 for PSI) compared to RBR (Pk = 0.74 [0.72-0.77], P < .001; R = 0.72 [0.65-0.78], P < .001) and SEF (Pk = 0.55 [0.50-0.59], P = .041; R = 0.13 [-0.01 to 0.27], P = .067).

CONCLUSIONS

BIS, PSI, and RBR showed an acceptable correlation with the effect-site remimazolam concentration and depth of sedation in this study, suggesting that these EEG-derived parameters are potentially reliable hypnotic indicators during remimazolam sedation. BIS and PSI showed superior performance as hypnotic indicators to RBR and SEF in patients receiving target-controlled infusion of remimazolam.

The Characteristics of Electroencephalogram Signatures in Minimally Conscious State Patients Induced by General Anesthesia

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.

EEG Connectivity Diversity Differences between Children with Autism and Typically Developing Children: A Comparative Study

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social interaction and communication, and repetitive or stereotyped behaviors. Previous studies have reported altered brain connectivity in ASD children compared to typically developing children. In this study, we investigated the diversity of connectivity patterns between children with ASD and typically developing children using phase lag entropy (PLE), a measure of the variability of phase differences between two time series. We also developed a novel wavelet-based PLE method for the calculation of PLE at specific scales. Our findings indicated that the diversity of connectivity in ASD children was higher than that in typically developing children at Delta and Alpha frequency bands, both within brain regions and across hemispheric brain regions. These findings provide insight into the underlying neural mechanisms of ASD and suggest that PLE may be a useful tool for investigating brain connectivity in ASD.

Comparison of bispectral index and phase lag entropy during general anesthesia: Sevoflurane or propofol anesthesia

BACKGROUND

Phase-lag entropy (PLE) based on functional connectivity between different regions of the brain may be superior to conventional depth of anesthesia (DoA) methods for monitoring changes in consciousness. However, few studies have compared the PLE and bispectral index (BIS) methods for monitoring consciousness during clinical anesthesia, such as total intravenous anesthesia (TIVA) or anesthesia via inhalation. Therefore, we evaluated differences between the PLE and BIS methods in clinical anesthesia, including TIVA using propofol and anesthesia with sevoflurane.

METHODS

The observational trial included 60 patients scheduled for elective surgery under general anesthesia. The BIS and PLE electrodes were placed together on the left temporal-frontal area of all patients. During anesthesia, anesthetic levels were adjusted using the BIS values, which are generally used to monitor the DoA; the level of anesthesia was maintained at between 40 and 60. BIS- and PLE-derived values were recorded continuously. Anesthetic events, the concentration of each anesthetic, and standard monitoring values were recorded. The patients included were divided into 2 groups, the TIVA and sevoflurane groups, with 30 patients in each. For the TIVA group, anesthesia was induced and maintained using propofol and remifentanil target-controlled infusion. For the sevoflurane group, anesthesia was induced using propofol and maintained using sevoflurane and remifentanil.

RESULTS

From loss of consciousness until the anesthetic maintenance period, PLE values were higher than BIS values at several time points. During the recovery period, BIS values were higher than PLE values (all P < .001). Spaghetti plots showed that there was more variation among the BIS values than among the PLE values.

CONCLUSIONS

For monitoring DoA during general anesthesia and surgery, PLE values vary less than BIS values; thus, PLE may be more reliable for monitoring changes in consciousness. However, further studies are needed to evaluate the clinical application of these methods in general anesthesia.

Comparison of the performance of phase lag entropy and bispectral index for monitoring the depth of sedation under dexmedetomidine sedation: A prospective, observational, and non-inferiority trial

STUDY OBJECTIVE

Although the performance of phase lag entropy (PLE), a new depth-of-sedation monitor based on the diversity of temporal patterns in the phase relationships in electroencephalogram (EEG) data, during propofol sedation has been proven through several studies, since different sedatives have different effects on EEG, we aimed to evaluate the performance of the PLE in comparison with the bispectral index (BIS) during dexmedetomidine sedation.

DESIGN

A prospective, observational, and non-inferiority trial.

SETTING

Tertiary university hospital operating room.

PATIENTS

Forty-two patients aged 20-80 years who were scheduled to undergo elective surgery under spinal anesthesia and had American Society of Anesthesiologists (ASA) physical status I to III were enrolled in this study.

INTERVENTIONS

Dexmedetomidine was administered with a loading dose of 0.5-1 μg/kg for 10 min, followed by a maintenance dose of 0.3-0.6 μg/kg/h.

MEASUREMENTS

The depth of sedation was assessed using the modified observer's assessment of alertness/sedation (MOAA/S) scale; the data for PLE and BIS were collected; and vital signs, including blood pressure, heart rate, EKG, and pulse oximetry, were evaluated.

MAIN RESULTS

215,082 data points for the MOAA/S score and PLE and BIS values were analyzed. The baseline variabilities of PLE and BIS were 4.53% and 7.02%, respectively. The Spearman correlation coefficients of the MOAA/S score with PLE and BIS were 0.599 and 0.566, respectively. The prediction probabilities of the MOAA/S score with PLE and BIS were 0.647 and 0.636, respectively. When the MOAA/S score was 3 points, the mean (SD) values of PLE and BIS were 68.35 (15.68) and 75.85 (9.81), respectively, However, the mean (SD) values of PLE and BIS for an MOAA/S score of 1 point were 56.08 (12.49) and 68.29 (12.65), respectively.

CONCLUSIONS

PLE shows potential as a hypnotic depth indicator during dexmedetomidine sedation, and its performance was not inferior to that of BIS.

The influence of neuromuscular blockade on phase lag entropy and bispectral index: A randomized, controlled trial

The aim of this study is to compare the effects of neuromuscular blockade (NMB) on phase lag entropy (PLE) and the bispectral index (BIS). We recorded the BIS, electromyograph (EMG) activity on a BIS monitor (EMG_BIS), PLE, and EMG activity on a PLE monitor (EMG_PLE) in 40 patients receiving general anesthesia. During the awake state, we analyzed the changes in parameters before and 2 min after the eyes were closed. During sedation, we compared the changes in the parameters before and at 4 min after injecting rocuronium (group R) or normal saline (group C) between the two groups. During anesthesia, we compared the changes in parameters before and at 4 min after injecting sugammadex (group B) or normal saline (group D) between the two groups. During the awake state, the BIS, EMG_BIS, and EMG_PLE, but not PLE, decreased significantly with closed eyes. An effect of EMG on the BIS was evident, but not on PLE. During sedation, the BIS decreased with the decrease in EMG_BIS regardless of NMB caused by rocuronium, but NMB decreased PLE, although the degree of the decrease in EMG_PLE after NMB was similar to that after placebo. To determine the effect of NMB on electroencephalograms (EEGs) in groups R and C, we plotted the power spectra before and at 4 min after injecting rocuronium or normal saline. Changes in slow and delta frequency bands were observed at 4 min after injecting rocuronium relative to before injecting rocuronium. There was no effect of EMG on either the BIS or PLE during anesthesia. In conclusion, the effect of electromyograph activity and/or neuromuscular blockade on BIS or PLE depends on the level of consciousness.

The relationship between the effect-site concentration of propofol and sedation scale in children: a pharmacodynamic modeling study

Background

Continuous infusion of propofol has been used to achieve sedation in children. However, the relationship between the effect-site concentration (C_e) of propofol and sedation scale has not been previously examined. The objective of this study was to investigate the relationship between the C_e of propofol and the University of Michigan Sedation Scale (UMSS) score in children with population pharmacodynamic modeling.

Methods

A total of 30 patients (aged 3 to 6 years) who underwent surgery under general anesthesia with propofol and remifentanil lasting more than 1 h were enrolled in this study. Sedation levels were evaluated using the UMSS score every 20 s by a 1 μg/mL stepwise increase in the C_e of propofol during the induction of anesthesia. The pharmacodynamic relationship between the C_e of propofol and UMSS score was analyzed by logistic regression with nonlinear mixed-effect modeling.

Results

The estimated C_e50 (95% confidence interval) of propofol to yield UMSS scores equal to or greater than n were 1.84 (1.54–2.14), 2.64 (2.20–3.08), 3.98 (3.66–4.30), and 4.78 (4.53–5.03) μg/mL for n = 1, 2, 3, and 4, respectively. The slope steepness for the relationship of the C_e versus sedative response to propofol (95% confidence interval) was 5.76 (4.00–7.52).

Conclusions

We quantified the pharmacodynamic relationship between the C_e of propofol and UMSS score, and this finding may be helpful to predict the sedation score at the target C_e of propofol in children.

Trial registration

http://www.clinicaltrials.gov (No.: NCT03195686, Date of registration: 22/06/2017).

Do epoch lengths of hypnotic depth indicators affect estimated of blood-brain equilibration rate constants of propofol?

This study aimed to investigate the effect of epoch length of hypnotic depth indicators on the blood-brain equilibration rate constant (k_e0) estimates of propofol. Propofol was administered by zero-order infusion (1.5, 3.0, 6, and 12 mg·kg^-1·h^-1) for one hour in 63 healthy volunteers. The k_e0 of propofol was estimated using an effect-compartment model linking pharmacokinetics and pharmacodynamics, in which response variables were electroencephalographic approximate entropy (ApEn) or bispectral index (BIS) (n = 32 each for propofol infusion rates of 6 and 12 mg·kg^-1·h^-1). Epoch lengths of ApEn were 2, 10, 30, and 60 seconds (s). The correlations between plasma propofol concentrations (Cp) and BIS and ApEn 2, 10, 30, and 60 s were determined, as was the Ce associated with 50% probability of unconsciousness (Ce_50,LOC). The pharmacokinetics of propofol were well described by a three-compartment model. The correlation coefficient between Cp and ApEn 2, 10, 30, and 60 s were -0.64, -0.54, -0.39, and -0.26, respectively, whereas correlation coefficient between Cp and BIS was -0.74. The blood-brain equilibration half-life based on the k_e0 estimates for ApEn at 2, 10, 30, 60 s and BIS were 4.31, 3.96, 5.78. 6.54, 5.09 min, respectively, whereas the Ce_50,LOC for ApEn at 2, 10, 30, 60 s and BIS were 1.55, 1.47, 1.28, 1.04, and 1.55 μg·ml^-1, respectively. Since k_e0, which determines the onset of drug action, varies according to the epoch length, it is necessary to consider the epoch length together when estimating k_e0.

Effect of depth of anesthesia on the phase lag entropy in patients undergoing general anesthesia by propofol: A STROBE-compliant study

The PLEM100 (Inbody Co., Ltd., Seoul, Korea) is a device for measuring phase lag entropy (PLE), a recently developed index for the quantification of consciousness during sedation and general anesthesia. In the present study, we assessed changes in PLE along with the level of consciousness during the induction of general anesthesia using propofol. PLE was compared with the bispectral index (BIS), which is currently the most commonly used index of consciousness.After obtaining Institutional Review Board approval and written informed consent, we enrolled 15 patients (8 men, 7 women; mean age: 37 ± 9 years; mean height: 168 ± 8 cm; mean weight; 68 ± 11 kg) undergoing nasal bone reduction. PLE and BIS sensors were attached simultaneously, and general anesthesia was induced via target-controlled infusion (TCI) of propofol. PLE and BIS scores were recorded when the calculated effect site concentration shown on the TCI pump was equal to the target concentrations of 1.5, 2.0, 2.5, 2.8, 3.0, 3.2, 3.4, and 3.5 μg/mL (and at each 0.1 μg/mL increase, thereafter). Observer's Assessment of Alertness/Sedation (OAA/S) scores were also recorded until unconsciousness was achieved. Throughout the anesthesia period, all pairs of PLE and BIS data were collected using data acquisition software.The partial correlation coefficients between OAA/S scores and PLE, and between OAA/S scores and BIS were 0.778 (P < .001) and 0.846 (P < .001), respectively. Throughout the period of anesthesia, PLE and BIS exhibited a significant positive correlation. The partial correlation coefficient prior to the loss of consciousness was 0.838 (P < .001), and 0.669 (P < .001) following the loss of consciousness. Intra-class correlation between the 2 indices was 0.889 (P < .001) and 0.791 (P < .001) prior and following the loss of consciousness, respectively.PLE exhibited a strong and predictable correlation with both BIS and OAA/S scores. These results suggest that PLE is reliable for assessing the level of consciousness during sedation and general anesthesia.

Monitoring of anesthetic depth and EEG band power using phase lag entropy during propofol anesthesia

Background

Phase lag entropy (PLE) is a novel anesthetic depth indicator that uses four-channel electroencephalography (EEG) to measure the temporal pattern diversity in the phase relationship of frequency signals in the brain. The purpose of the study was to evaluate the anesthetic depth monitoring using PLE and to evaluate the correlation between PLE and bispectral index (BIS) values during propofol anesthesia.

Methods

In thirty-five adult patients undergoing elective surgery, anesthesia was induced with propofol using target-controlled infusion (the Schneider model). We recorded the PLE value, raw EEG, BIS value, and hemodynamic data when the target effect-site concentration (Ce) of propofol reached 2, 3, 4, 5, and 6 μg/ml before intubation and 6, 5, 4, 3, 2 μg/ml after intubation and injection of muscle relaxant. We analyzed whether PLE and raw EEG data from the PLE monitor reflected the anesthetic depth as the Ce of propofol changed, and whether PLE values were comparable to BIS values.

Results

PLE values were inversely correlated to changes in propofol Ce (propofol Ce from 0 to 6.0 μg/ml, r² = − 0.83; propofol Ce from 6.0 to 2.0 μg/ml, r² = − 0.46). In the spectral analysis of EEG acquired from the PLE monitor, the persistence spectrogram revealed a wide distribution of power at loss of consciousness (LOC) and recovery of consciousness (ROC), with a narrow distribution during unconsciousness. The power spectrogram showed the typical pattern seen in propofol anesthesia with slow alpha frequency band oscillation. The PLE value demonstrated a strong correlation with the BIS value during the change in propofol Ce from 0 to 6.0 μg/ml (r² = 0.84). PLE and BIS values were similar at LOC (62.3 vs. 61.8) (P > 0.05), but PLE values were smaller than BIS values at ROC (64.4 vs 75.7) (P < 0.05).

Conclusions

The PLE value is a useful anesthetic depth indicator, similar to the BIS value, during propofol anesthesia. Spectral analysis of EEG acquired from the PLE monitor demonstrated the typical patterns seen in propofol anesthesia.

Trial registration

This clinical trial was retrospectively registered at ClinicalTrials.gov at October 2017 (NCT03299621).