Comparative Evaluation of the Datex-Ohmeda S/5 Entropy Module and the Bispectral Index® Monitor during Propofol-Remifentanil Anesthesia

Background: Different analytical concepts were introduced to quantify the changes of the electroencephalogram. The Datex-Ohmeda S/5 Entropy Module (Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland) was the first commercial monitor based on the entropy generating two indices, the state entropy (SE) and the response entropy (RE). The aim of the current study was to compare the accuracy of SE and RE with the Bispectral Index(R) monitor (BIS(R); Aspect Medical Systems, Newton, MA) during propofol-remifentanil anesthesia.

Methods: The authors investigated 20 female patients during minor gynecologic surgery. SE, RE, BIS, mean arterial blood pressure, heart rate, and sedation level were recorded every 20 s during stepwise increase (target-controlled infusion, 0.5 [mu]g/ml) of propofol until the patients lost response. Five minutes after loss of response, remifentanil infusion (0.4 [mu]g [middle dot] kg-1 [middle dot] min-1) was started. Spearman correlation coefficient and prediction probability were calculated for sedation levels with SE, RE, BIS, mean arterial blood pressure, and heart rate. The ability of the investigated parameters to distinguish between the anesthesia steps awake versus loss of response, awake versus anesthesia, anesthesia versus first reaction, and anesthesia versus extubation was analyzed with the prediction probability.

Results: SE correlates best with sedation levels, but no significant differences of the prediction probability values among SE, RE, and BIS were found. The prediction probability for all investigated steps of anesthesia did not show significant differences among SE, RE, and BIS. SE, RE, and BIS were superior to mean arterial blood pressure and heart rate.     

Spectral entropy and bispectral index as measures of the electroencephalographic effects of propofol

Recently, Datex-Ohmeda introduced the Entropy Moduletrade mark for measuring depth of anesthesia. Based on the Shannon entropy of the electroencephalogram, state entropy (SE) and response entropy (RE) are computed. We investigated the dose-response relationship of SE and RE during propofol anesthesia in comparison with the Bispectral Indextrade mark (BIS). Twenty patients were studied without surgical stimulus. Anesthesia was induced by a constant propofol infusion of 2000 mg/h (451 +/- 77 microg x min(-1) x kg(-1)) via a large forearm vein. Propofol was infused until substantial burst suppression occurred (more than 50%) or mean arterial blood pressure decreased to <60 mm Hg. Hereafter, infusions were stopped until recovery of BIS values up to 60 was reached. Subsequently, the constant propofol infusion of 2000 mg/h was restarted to increase depth of anesthesia and again decreased (infusion was stopped) within the BIS value range of 40-60. The coefficient of determination (R2) and the prediction probability (P(K)) were calculated to evaluate the performance of SE, RE, and BIS to predict changing propofol effect-site concentrations. R2 values for SE, RE, and BIS of 0.88 +/- 0.08, 0.89 +/- 0.07, and 0.92 +/- 0.06, respectively, were similar. The calculated P(K) values, however, revealed a significant difference between SE and RE compared with BIS, with P(K) = 0.77 +/- 0.09, 0.76 +/- 0.10, and 0.84 +/- 0.06, respectively. BIS seems to show slight advantages in predicting propofol effect-site concentrations compared with SE and RE, as measured by P(K) but not as measured by R2.     

Spectral Entropy and Bispectral Index as Measures of the Electroencephalographic Effects of Sevoflurane

Background: Recently, entropy algorithms have been proposed as electroencephalographic measures of anesthetic drug effects. Datex-Ohmeda (Helsinki, Finland) introduced the Entropy Module, a new electroencephalographic monitor designed for measuring depth of anesthesia. The monitor calculates a state entropy (SE) computed over the frequency range of 0.8-32 Hz and a response entropy (RE) computed over the frequency range of 0.8-47 Hz. The authors investigated the dose-response relation of SE and RE during sevoflurane anesthesia in comparison with the Bispectral Index (BIS).

Methods: Sixteen patients were studied without surgical stimulus. Anesthesia was induced by sevoflurane inhalation with a tight-fitting facemask. Sevoflurane concentrations were increased and subsequently decreased and increased two to four times until the measurement was stopped and patients were intubated for surgery. The performances of SE, RE, and BIS to predict the estimated sevoflurane effect site concentration, obtained by simultaneous pharmacokinetic and pharmacodynamic modeling, were compared by calculating the correlation coefficients and the prediction probability.

Results: State entropy, RE, and BIS values decreased continuously over the observed concentration range of sevoflurane. Correlation coefficients were slightly but not significantly better for entropy parameters (0.87 +/- 0.09 and 0.86 +/- 0.10 for SE and RE, respectively) than for BIS (0.85 +/- 0.12). Calculating the prediction probability confirmed these results with a prediction probability of 0.84 +/- 0.05 and 0.82 +/- 0.06 for SE and RE, respectively, and 0.80 +/- 0.06 for BIS.     

Spectral entropy and bispectral index as measures of the electroencephalographic effects of sevoflurane

BACKGROUND: Recently, entropy algorithms have been proposed as electroencephalographic measures of anesthetic drug effects. Datex-Ohmeda (Helsinki, Finland) introduced the Entropy Module, a new electroencephalographic monitor designed for measuring depth of anesthesia. The monitor calculates a state entropy (SE) computed over the frequency range of 0.8-32 Hz and a response entropy (RE) computed over the frequency range of 0.8-47 Hz. The authors investigated the dose-response relation of SE and RE during sevoflurane anesthesia in comparison with the Bispectral Index (BIS). METHODS: Sixteen patients were studied without surgical stimulus. Anesthesia was induced by sevoflurane inhalation with a tight-fitting facemask. Sevoflurane concentrations were increased and subsequently decreased and increased two to four times until the measurement was stopped and patients were intubated for surgery. The performances of SE, RE, and BIS to predict the estimated sevoflurane effect site concentration, obtained by simultaneous pharmacokinetic and pharmacodynamic modeling, were compared by calculating the correlation coefficients and the prediction probability. RESULTS: State entropy, RE, and BIS values decreased continuously over the observed concentration range of sevoflurane. Correlation coefficients were slightly but not significantly better for entropy parameters (0.87 +/- 0.09 and 0.86 +/- 0.10 for SE and RE, respectively) than for BIS (0.85 +/- 0.12). Calculating the prediction probability confirmed these results with a prediction probability of 0.84 +/- 0.05 and 0.82 +/- 0.06 for SE and RE, respectively, and 0.80 +/- 0.06 for BIS. CONCLUSION: State entropy and RE seem to be useful electroencephalographic measures of sevoflurane drug effect.     

Evaluation of the sedation level with propofol with electroencephalographic Entropy in comparison with bispectral index monitor

BACKGROUND: Entropy, a newly available electroencephalographic monitor, demonstrates two parameters, response entropy (RE) and state entropy (SE). The aim of this study is to compare RE and SE with bispectral index (BIS) during anesthetic induction with propofol. METHODS: Fifteen patients received target controlled infusion of propofol starting at 3 microg x ml(-1). We measured RE, SE and BIS and recorded effect-site concentrations of propofol at three sedation levels: VR1; conscious state before infusion of propofol, VR2; no response to verbal command, and VR3; no response to verbal command and shaking. Spearman rank correlations and prediction probability for sedation level were analyzed. RESULTS: Effect-site concentrations of propofol at VR1, VR2, and VR3 were 0, 1.8 +/- 0.7, and 2.4 +/- 0.7, respectively. All three parameters showed significant correlations with sedation levels. Prediction probability values of SE, RE, and BIS were 0.905, 0.894, and 0.890, respectively. CONCLUSIONS: Response entropy and SE can provide similar information as BIS about the sedation level with propofol.     

Bispectral index and spectral entropy in neuroanesthesia

Spectral Entropy (SpEn) is an alternative tool to the bispectral index (BIS) for monitoring depth of hypnosis. SpEn measures response entropy (RE) and state entropy (SE). This open-label prospective study was designed to evaluate SpEn and BIS in 20 patients undergoing elective supratentorial neurosurgery with craniotomy and resection of brain tumors. SpEn and BIS were obtained continuously by Datex Ohmeda M-entropy module S/5 (Helsinki, Finland) and Aspect Medical System BIS (Newton), respectively. Total intravenous anesthesia was performed in all patients by Fresenius Vial infusion system (Brezins, France) to maintain a plasma concentration of propofol of 2.5 to 5 microg mL(-1) and sufentanil of 0.2 to 0.4 etag mL(-1). SpEn, BIS, the estimated propofol effect-site concentrations (Ce), the mean arterial pressure (MAP), and the heart rate (HR) were recorded during 12 specific events: induction of anesthesia, patient stop counting, loss of blinking reflex, intubation, mayfield pinning, craniotomy, termination of propofol infusion, recovery of blinking reflex, coughing, limb movement, order execution, and extubation. Stated that prediction probability or P(K) represents an indicator probability to predict correctly the rank order of an arbitrary pair of distinct observed indices of depth of hypnosis (ie, clinical settings and SpEn indices, or BIS, Ce, MAP, HR), PK of BIS, SE, RE, and Ce provided a better depth of hypnosis than MAP and HR; RE being the best for rapidity, SE for sensitivity, and BIS for specificity. There is good correlation between the 3 hypnosis indices and Ce. This study demonstrates that SpEn provides a reproducible hypnosis index for patients undergoing supratentorial neurosurgical procedures.     

熵指数监测全麻患者镇静水平的准确性

目的 评价反应熵和状态熵监测全麻患者镇静水平的准确性.方法 择期行腹部手术患者20例,ASAⅠ或Ⅱ级,入室后监测反应熵(RE)、状态熵(SE)及脑电双频谱指数(BIS),静脉注射异丙酚、维库溴铵和芬太尼麻醉诱导,气管插管后机械通气,吸入七氟烷、间断静脉注射维库溴铵和芬太尼维持麻醉.分别于入室时、意识消失前10min、意识消失即刻、气管插管时、手术1 h、意识恢复前10 min、意识恢复即刻、拔管后10 min时记录RE、SE和BIS.结果 RE、SE和BIS在意识改变前后差异均有统计学意义(P＜0.05),RE、SE和BIS判断意识消失的临界值分别为76、73和68,灵敏度分别为94%、95%和92%,特异度分别为92%、94%和9l%,临界值判断意识消失的准确度分别为93%、95%、94%;判断意识恢复的临界值分别为82、75和70,灵敏度分别为95%、95%和91%,特异度分别为93%、96%和93%,临界值判断意识恢复的准确度分别为98%、96%和97%.结论 熵指数能够准确地监测全麻患者镇静水平.     

Spectral entropy as an electroencephalographic measure of anesthetic drug effect: a comparison with bispectral index and processed midlatency auditory evoked response

BACKGROUND: The authors compared the behavior of two calculations of electroencephalographic spectral entropy, state entropy (SE) and response entropy (RE), with the A-Line ARX Index (AAI) and the Bispectral Index (BIS) and as measures of anesthetic drug effect. They compared the measures for baseline variability, burst suppression, and prediction probability. They also developed pharmacodynamic models relating SE, RE, AAI, and BIS to the calculated propofol effect-site concentration (Ceprop). METHODS: With institutional review board approval, the authors studied 10 patients. All patients received 50 mg/min propofol until either burst suppression greater than 80% or mean arterial pressure less than 50 mmHg was observed. SE, RE, AAI, and BIS were continuously recorded. Ceprop was calculated from the propofol infusion profile. Baseline variability, prediction of burst suppression, prediction probability, and Spearman rank correlation were calculated for SE, RE, AAI, and BIS. The relations between Ceprop and the electroencephalographic measures of drug effect were estimated using nonlinear mixed effect modeling. RESULTS: Baseline variability was lowest when using SE and RE. Burst suppression was most accurately detected by spectral entropy. Prediction probability and individualized Spearman rank correlation were highest for BIS and lowest for SE. Nonlinear mixed effect modeling generated reasonable models relating all four measures to Ceprop. CONCLUSIONS: Compared with BIS and AAI, both SE and RE seem to be useful electroencephalographic measures of anesthetic drug effect, with low baseline variability and accurate burst suppression prediction. The ability of the measures to predict Ceprop was best for BIS.     

Spectral Entropy as an Electroencephalographic Measure of Anesthetic Drug Effect: A Comparison with Bispectral Index and Processed Midlatency Auditory Evoked Response

Background: The authors compared the behavior of two calculations of electroencephalographic spectral entropy, state entropy (SE) and response entropy (RE), with the A-Line(R) ARX Index (AAI) and the Bispectral Index (BIS) and as measures of anesthetic drug effect. They compared the measures for baseline variability, burst suppression, and prediction probability. They also developed pharmacodynamic models relating SE, RE, AAI, and BIS to the calculated propofol effect-site concentration (Ceprop).

Methods: With institutional review board approval, the authors studied 10 patients. All patients received 50 mg/min propofol until either burst suppression greater than 80% or mean arterial pressure less than 50 mmHg was observed. SE, RE, AAI, and BIS were continuously recorded. Ceprop was calculated from the propofol infusion profile. Baseline variability, prediction of burst suppression, prediction probability, and Spearman rank correlation were calculated for SE, RE, AAI, and BIS. The relations between Ceprop and the electroencephalographic measures of drug effect were estimated using nonlinear mixed effect modeling.

Results: Baseline variability was lowest when using SE and RE. Burst suppression was most accurately detected by spectral entropy. Prediction probability and individualized Spearman rank correlation were highest for BIS and lowest for SE. Nonlinear mixed effect modeling generated reasonable models relating all four measures to Ceprop.     

Time-frequency balanced spectral entropy as a measure of anesthetic drug effect in central nervous system during sevoflurane, propofol, and thiopental anesthesia

BACKGROUND: Time-frequency balanced spectral entropy of electroencephalogram (EEG) and frontal electromyogram (FEMG) is a novel measure of hypnosis during anesthesia. Two Entropy parameters are described: Response entropy (RE) is calculated from EEG and FEMG; and State Entropy (SE) is calculated mainly from EEG. This study was performed to validate their performance during transition from consciousness to unconsciousness under different anesthetic agents. METHODS: Response entropy, SE [S/5 Entropy Module, M-ENTROPY (later in text: Entropy), Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland] and BIS (BIS XP, A-2000, Aspect Medical Systems, Newton, MA) data were collected from 70 patients; 30 anesthetized with propofol 2 mg kg-1, 20 with sevoflurane inhalation, and 20 with thiopental 5 mg kg-1. Loss and regaining of consciousness (LOC, ROC) was tested every 10 s, and sensitivity, specificity, and prediction probability (Pk) were calculated. Behavior of the indices was studied. RESULTS: Sensitivity, specificity, and Pk values for consciousness were high and similar for all indices. During regaining of consciousness after propofol bolus, RE, SE, and BIS values recovered by 81 +/- 22%, 75 +/- 26%, and 59 +/- 18% (mean +/- SD), respectively, from the minimum relative to their baseline. After thiopental bolus, RE, SE, and BIS values recovered by 86+/-21%, 88 +/- 13%, and 63 +/- 14%, respectively. The relative rise was higher in RE and SE compared with BIS (P < 0.01). During deep levels of hypnosis, RE and SE decreased monotonously as a function of burst suppression ratio, while BIS showed biphasic behavior. On average, RE indicated emergence from anesthesia 11 s earlier than SE, and 12.4 s earlier than BIS. CONCLUSIONS: All indices, RE, SE, and BIS, distinguished excellently between conscious and unconscious states during propofol, sevoflurane, and thiopental anesthesia. During burst suppression, Entropy parameters RE and SE, but not BIS, behave monotonously. During regaining of consciousness after a thiopental or propofol bolus, RE and SE values recovered significantly closer to their baseline values than did BIS. Response entropy indicates emergence from anesthesia earlier than SE or BIS.     

Spectral Entropy as a Measure of Hypnosis in Children

Background: The Datex-Ohmeda S/5 Entropy Module (Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland), using time-frequency balanced Spectral Entropy, is a novel tool for monitoring the hypnotic state during anesthesia. The Entropy Module produces two values, State Entropy (SE) and Response Entropy (RE), and in adults, it has been shown to measure reliably the hypnotic effects of various drugs. In children, Spectral Entropy has been only preliminary studied. The authors' aim was to study Spectral Entropy as a marker of hypnotic state during general anesthesia in infants and children.

Methods: Twenty infants (aged 1 month-1 yr) and 40 children (aged 1-15 yr) were anesthetized for surgery using standardized sevoflurane-nitrous oxide-based anesthesia. The relationships between SE, RE, or Bispectral Index (BIS) and (1) a modified Observer's Assessment of Alertness/Sedation Scale, (2) non-steady state end-tidal concentration of sevoflurane, (3) steady state end-tidal concentration of sevoflurane, and (4) hemodynamic values were calculated using prediction probability, nonlinear regression, and correlation coefficients, as appropriate. The performances of SE, RE, and BIS were compared.

Results: The prediction probability values (+/- SEM) of SE, RE, and BIS versus the modified Observer's Assessment of Alertness/Sedation Scale in the induction phase were 0.83 +/- 0.06, 0.88 +/- 0.06, and 0.87 +/- 0.08 for children and 0.76 +/- 0.08,0.79 +/- 0.08, and 0.73 +/- 0.10 for infants; values in the emergence phase were 0.68 +/- 0.05, 0.74 +/- 0.04, and 0.64 +/- 0.05 for children and 0.64 +/- 0.07, 0.69 +/- 0.06, and 0.72 +/- 0.06 for infants, respectively. SE, RE, and BIS values were inversely proportionally related to the end-tidal concentration of sevoflurane for children, but for infants, the correlation was much less clear. No significant correlations were found between SE, RE, or BIS values and the hemodynamic values.     

Spectral entropy as a measure of hypnosis in children

BACKGROUND: The Datex-Ohmeda S/5 Entropy Module (Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland), using time-frequency balanced Spectral Entropy, is a novel tool for monitoring the hypnotic state during anesthesia. The Entropy Module produces two values, State Entropy (SE) and Response Entropy (RE), and in adults, it has been shown to measure reliably the hypnotic effects of various drugs. In children, Spectral Entropy has been only preliminary studied. The authors' aim was to study Spectral Entropy as a marker of hypnotic state during general anesthesia in infants and children. METHODS: Twenty infants (aged 1 month-1 yr) and 40 children (aged 1-15 yr) were anesthetized for surgery using standardized sevoflurane-nitrous oxide-based anesthesia. The relationships between SE, RE, or Bispectral Index (BIS) and (1) a modified Observer's Assessment of Alertness/Sedation Scale, (2) non-steady state end-tidal concentration of sevoflurane, (3) steady state end-tidal concentration of sevoflurane, and (4) hemodynamic values were calculated using prediction probability, nonlinear regression, and correlation coefficients, as appropriate. The performances of SE, RE, and BIS were compared. RESULTS: The prediction probability values (+/- SEM) of SE, RE, and BIS versus the modified Observer's Assessment of Alertness/Sedation Scale in the induction phase were 0.83 +/- 0.06, 0.88 +/- 0.06, and 0.87 +/- 0.08 for children and 0.76 +/- 0.08,0.79 +/- 0.08, and 0.73 +/- 0.10 for infants; values in the emergence phase were 0.68 +/- 0.05, 0.74 +/- 0.04, and 0.64 +/- 0.05 for children and 0.64 +/- 0.07, 0.69 +/- 0.06, and 0.72 +/- 0.06 for infants, respectively. SE, RE, and BIS values were inversely proportionally related to the end-tidal concentration of sevoflurane for children, but for infants, the correlation was much less clear. No significant correlations were found between SE, RE, or BIS values and the hemodynamic values. CONCLUSIONS: Spectral Entropy may be a useful tool for measuring the level of hypnosis in anesthetized children and seems to perform as well as BIS. In infants, the clinical usefulness of both these electroencephalogram-derived methods must be evaluated in further controlled studies.     

SNAP index and Bispectral index during different states of propofol/remifentanil anaesthesia

The accuracy of the new SNAP index with the Bispectral index (BIS) to distinguish different states of propofol/remifentanil anaesthesia was compared in 19 female patients who were undergoing minor gynaecological surgery. Comparisons of the SNAP index, BIS, spectral edge frequency, mean arterial blood pressure and heart rate were performed. The ability of all parameters to distinguish between the steps of anaesthesia -awake vs. loss of response, awake vs. anaesthesia, anaesthesia vs. first reaction and anaesthesia vs. extubation - were analysed with the prediction probability. The prediction probability to differentiate between two interesting nuances of anaesthetic states -loss of response vs. first reaction - was calculated. Only the BIS showed no overlap between the investigated steps of anaesthesia. Both the SNAP index and BIS failed to differentiate the nuances of anaesthesia. The SNAP index and BIS were superior to mean arterial blood pressure and heart rate and spectral edge frequency in distinguishing between different steps of anaesthesia with propofol and remifentanil and provided useful additional information.     

听觉诱发相关电位，脑电双频指数和熵用于判断重症监护病房患者的不同镇静状态

背景包括镇静评分和常规镇静暂停在内的镇静方案,有助干减少机械通气时间和重症监护病房（ICU）入住时间。因临床上对于镇静深度的评估工作量大、仅能间断进行且干扰镇静和睡眠,所以通过脑电生理信号评估镇静深度的替代方法已经开始倍受青睐：我们想明确听觉诱发相关电位（ERPs）、脑电双频指数（BIS）和墒（Entropy）是否也能够评估临床镇静深度。方法选择10例择期全麻下行胸部或腹部手术的患者。手术后进入ICU,逐渐减少丙泊酚和瑞芬太尼靶控镇静程度[采用Rickmond Agitation镇静评分（RASS）,-5分极深镇静,-4分深度镇静,-3～-1分中度镇静,0分清醒]期间,记录脑电图、BIS、状态熵（SE）、反应墒（RE）和ERPs。手术前或手术后数天测量指标的相关基础水平。结果基线、PASS-5分、RASS-4分、RASS-3至-1分和PASS-0分,对应的BIS值分别是94[4]（中位数,四分位数间距）、47[15]、68[9]、75[10]和88[6];对应的SE值分别是87[3]、46[10]、60[22]、74[21]和87[5];对应的RE值分别是97[4]、48[9]、71[25]、81[8]和96[3]（P〈0．05,Friedman检验）。BIS和墒都有高变异度。当单独考虑ERP振幅100时,各个镇静水平的ERPs值差异无显著性：但是、复括双参数主要变量分析的ERP辨别分析显示区别深度镇静、中度镇静和清醒状态的推算概率PK大约是0．89。与PK对应的RE,SE和BIS值分别是0．88、0．89和0．85。结论ERPs、BIS和熵均不能替代基于标准评分系统的临床镇静评估。全麻后对于极深镇静、深度到中度镇静和清醒的辨别,ERPs和脑电图仅能提供相似的PK值。BIS和熵存在较高的个体间和个体自身变异度,使其难以确定预测镇静水平的目标值范围,因而在危重患者中的使用受到限制。ERPs的变异度还不清楚。     

Response entropy increases during painful stimulation

Frontal electromyography (FEMG) may increase during painful stimulation and indicate patient arousal. The Datex-Ohmeda Entropy Module calculates state entropy (SE) of the electroencephalogram (EEG; 0.8-32 Hz) and response entropy (RE) of EEG and FEMG (0.8-47 Hz). We determined whether RE increases above SE (RE--SE), an indication of FEMG, increase during painful stimuli and if this is related to paralysis or level of anesthesia. With the unanesthetized baseline measurement, SE was 89 +/- 2 and RE was 98 +/- 2. During paralysis and anesthesia with either 0.8% (n = 10) or 1.4% (n = 10) isoflurane, SE decreased to 63 +/- 7 and 34 +/- 14, respectively, and the RE--SE difference decreased 90%. Before recovery from paralysis, arterial catheter or head pin placement increased RE--SE above unanesthetized levels in eight patients (five treated with 0.8% and three with 1.4% isoflurane), consistent with an increase in FEMG. The elevated RE--SE difference was related to a significant increase in SE, blood pressure, and heart rate. After recovery from paralysis, tetanic stimulation of the ulnar nerve increased the RE--SE difference above unanesthetized levels in 8 of 20 patients (6 treated with 0.8% and 2 with 1.4% isoflurane). In these patients, SE increased significantly. The remaining 12 patients did not show an increase in RE--SE during tetanic stimulation and SE did not increase. We conclude that increased RE during painful stimulation was not dependent on recovery from paralysis but was seen more often in patients anesthetized with 0.8% compared with 1.4% isoflurane. This suggests that RE reflects FEMG and may be useful to identify inadequate anesthesia and patient arousal during painful stimuli.     

Auditory steady-state response and bispectral index for assessing level of consciousness during propofol sedation and hypnosis

We assessed the effect of propofol on the auditory steady-state response (ASSR), bispectral (BIS) index, and level of consciousness in two experiments. In Experiment 1, propofol was infused in 11 subjects to obtain effect-site concentrations of 1, 2, 3, and 4 microg/mL. The ASSR and BIS index were recorded during baseline and at each concentration. The ASSR was evoked by monaural stimuli. Propofol caused a concentration-dependent decrease of the ASSR and BIS index values (r(2) = 0.76 and 0.93, respectively; P<0.0001). The prediction probability for loss of consciousness was 0.89, 0.96, and 0.94 for ASSR, BIS, and arterial blood concentration of propofol, respectively. In Experiment 2, we compared the effects of binaural versus monaural stimulus delivery on the ASSR in six subjects during awake baseline and propofol-induced unconsciousness. During baseline, the ASSR amplitude with binaural stimulation (0.47+/-0.13 microV, mean +/- SD) was significantly (P<0.002) larger than with monaural stimulation (0.35+/-0.11 microV). During unconsciousness, the amplitude was 0.09+/-0.09 microV with monaural and 0.06+/-0.04 microV with binaural stimulation (NS). The prediction probability for loss of consciousness was 0.97 (0.04 SE) for monaural and 1.00 (0.00 SE) for binaural delivery. We conclude that the ASSR and BIS index are attenuated in a concentration-dependent manner by propofol and provide a useful measure of its sedative and hypnotic effect. BIS was easier to use and slightly more sensitive. The ASSR should be recorded with binaural stimulation. The ASSR and BIS index are both useful for assessing the level of consciousness during sedation and hypnosis with propofol. However, the BIS index was simpler to use and provided a more sensitive measure of sedation. Implications: We have compared two methods for predicting whether the amount of propofol given to a human subject is sufficient to cause unconsciousness, defined as failure to respond to a simple verbal command. The two methods studied are the auditory steady-state response, which measures the electrical response of the brain to sound, and the bispectral index, which is a number derived from the electroencephalogram. The results showed that both methods are very good predictors of the level of consciousness; however, bispectral was easier to use.     

Comparative effects of ketamine on Bispectral Index and spectral entropy of the electroencephalogram under sevoflurane anaesthesia

Background. The Bispectral Index (BIS) and spectral entropyof the electroencephalogram can be used to assess the depthof hypnosis. Ketamine is known to increase BIS in anaesthetizedpatients and may confound that index as a guide to steer administrationof hypnotics. We compared the effects of ketamine on BIS, responseentropy (RE) and state entropy (SE) during surgery under sevofluraneanaesthesia. Methods. Twenty-two women undergoing gynaecological surgerywere enrolled in this double-blind, randomized study. Anaesthesiawas induced i.v. and maintained with sevoflurane. Under stablesurgical and anaesthetic conditions, patients were assignedto receive either a bolus of ketamine 0.5 mg kg^–1 or thesame volume of saline. Blood pressure, heart rate, BIS, RE andSE were measured every 2.5 min from 10 min before (baseline)until 15 min after ketamine or saline administration. The maximumrelative increase in BIS, RE and SE compared with baseline wascalculated for each patient. Values are mean (SD). Results. Baseline values were BIS 33 (4), RE 31 (5), SE 30 (5)for the ketamine patients and BIS 35 (3), RE 33 (5) and SE 32(6) for the patients receiving saline. BIS, RE and SE increasedsignificantly from 5 min (BIS) and 2.5 min (RE and SE) afterketamine administration, peaking at 46 (8) (BIS), 52 (12) (RE)and 50 (12) (SE) respectively. The maximum relative increasein RE [42.2 (10.4%)] and SE [41.6 (10.9)%] was higher than thatof BIS [29.4 (10.4%)]. Blood pressure, heart rate and RE–SEgradient did not change in either group. Conclusions. Ketamine administered under sevoflurane anaesthesiacauses a significant increase in BIS, RE and SE without modificationof the RE–SE gradient. This increase is paradoxical inthat it is associated with a deepening level of hypnosis.     

A comparison of state and response entropy versus bispectral index values during the perioperative period

Cerebral monitoring indices are associated with a large degree of inter-patient variability and electrical signal interference during surgery. We designed this clinical study to test the hypothesis that use of the spectral entropy (Entropy) module is associated with less frequent intraoperative interference with the displayed indices than the bispectral index (BIS) monitor when used during general anesthesia with propofol and desflurane. Thirty consenting patients scheduled for major laparoscopic surgery procedures were enrolled in this prospective study. The elapsed time to obtain a baseline index value was recorded, as well as the simultaneous state entropy (SE), response entropy (RE), and BIS values at specific time intervals during the induction, maintenance, and emergence periods in patients administered a standardized general anesthetic technique. During the maintenance period, the changes in these indices were evaluated after a bolus dose of propofol (20 mg IV) and a 2% increase or decrease in the inspired concentration of desflurane. As expected, the baseline SE values were less than the RE and BIS values (88 +/- 2 versus 96 +/- 3 and 96 +/- 4, respectively). However, the SE and RE values correlated with the BIS value during the induction (r = 0.77 and 0.78, respectively) and emergence (r = 0.86 and 0.91, respectively) periods. The area under the receiver operating characteristic curve for detection of consciousness also indicated a similar performance of the SE (0.93 +/- 0.04) relative to the RE (0.98 +/- 0.04) and BIS (0.97 +/- 0.04). During the maintenance period, the responses to changes in propofol and desflurane concentrations were consistent with all three indices. Finally, the entropy indices were less interfered with by the electrocautery unit during the operation (12% versus 62% for the BIS monitor). Because the average selling prices of the Entropy and BIS disposable electrode strips (14.25 dollars versus 14.95 dollars USD, respectively) are comparable, we conclude that the Entropy module is a cost-equivalent alternative to the BIS monitor.     

Comparative evaluation of Narcotrend, Bispectral Index, and classical electroencephalographic variables during induction, maintenance, and emergence of a propofol/remifentanil anesthesia

In the present study, we sought to compare the abilities of Narcotrend (NT) with the Bispectral Index (BIS) electroencephalographic system to monitor depth of consciousness immediately before induction of anesthesia until extubation during a standardized anesthetic. We investigated 26 patients undergoing laminectomy. Investigated states of anesthesia were: awake, loss of response, loss of eyelash reflex, steady-state anesthesia, first reaction, and extubation during emergence. NT, BIS, spectral edge frequency, median frequency, relative power in delta, theta, alpha, beta, and hemodynamics were recorded simultaneously. The ability of all variables to distinguish between awake versus loss of response, awake versus loss of eyelash reflex, awake versus steady-state anesthesia, steady-state anesthesia versus first reaction and extubation were analyzed with the prediction probability. Effects of remifentanil during propofol infusion were investigated with Friedman's and post hoc with Wilcoxon's test. Only NT and BIS were able to distinguish all investigated states accurately with a prediction probability >0.95. After start of remifentanil infusion, only hemodynamics changed statistically significantly (P < 0.05). NT and BIS are more reliable indicators for the assessment of anesthetic states than classical electroencephalographic variables and hemodynamics, whereas the analgesic potency of depth of anesthesia could not be detected by NT and BIS. IMPLICATIONS: The modern electroencephalographic monitoring systems Narcotrend and Bispectral Index are more reliable indicators for the assessment of anesthetic states than classical electroencephalographic and hemodynamic variables to predict anesthetic conditions from before induction of anesthesia until extubation during a standardized anesthetic regime with propofol and remifentanil. The analgesic potency of depth of anesthesia could not be detected by Narcotrend and Bispectral Index.     

脑电双频谱指数和脑电熵指数监测全麻患者镇痛水平的评价

目的 评价脑电双频谱指数(BIS)和脑电熵指数监测全麻患者镇痛水平的可行性.方法 择期全麻腹部手术患者26例,随机分为2组(n=13):试验组和对照组.常规监测行硬膜外置管后,试验组硬膜外注入1%利多卡因5 ml,对照组注入等量生理盐水,8 min后测定阻滞平面,根据结果试验组硬膜外追加1%利多卡因和0.5%罗哌卡因的混合制剂5～10 ml,对照组硬膜外追加生理盐水8 ml.麻醉诱导前确保试验组的感觉阻滞节段超过手术切口范围.连接BIS监测仪和脑电熵指数监测仪监测BIS、状态熵(SE)和反应熵(RE).靶控输注异丙酚(初始血浆靶浓度4 μg/ml)和瑞芬太尼(效应室靶浓度2 ng/ml)进行全麻诱导,调整异丙酚靶浓度,维持BIS 40～50.静脉注射罗库溴铵0.9 mg/kg,气管插管,机械通气,试验组停止输注瑞芬太尼,对照组继续输注瑞芬太尼,效应室靶浓度为2 ng/ml.切皮前3 min每分钟记录BIS、RE、SE、HR、SP、DP、MAP,取其平均值作为基础值,切皮后2 min内要求外科医师停止包括使用电刀在内的手术操作,每分钟记录上述指标.2 min后开始使用电刀,进行正常手术操作,并继续每分钟记录上述指标直到切皮后6 min,取其平均值.结果 与基础值比较,切皮后1 min时对照组BIS、RE-SE、SP、DP和MAP均升高(P＜0.05),试验组各指标差异无统计学意义(P＞0.05),切皮后3～6 min内2组BIS、RE和RE-SE均升高,对照组BP升高(P＜0.05).切皮后1min.对于判断镇痛是否足够的准确性,△SP＞△RE-SE＞△MAP＞△BIS,判断准确性均中等.而在电刀干扰时,只有BP的变化可以作为判断指标区分不同的分组,△SP＞△MAP.结论 BIS、熵指数和BP并不能反映镇痛水平,但BIS、RE-SE和BP都能够在镇痛不足的情况下对伤害性刺激表现出明显升高.对于镇痛不足的判断准确性,△SP＞△RE-SE＞△BIS,准确性均中等.