A comparison of patient state index and bispectral index values during the perioperative period

The patient state index (PSI), a quantitative electroencephalographic index, has been recently introduced into clinical practice as a monitor for assessing consciousness during sedation and general anesthesia. We designed this observational study to compare the sensitivity and specificity of the PSI with that of the bispectral index (BIS) with respect to their ability to predict the loss of consciousness and emergence from anesthesia, as well as to assess changes in IV (propofol) and inhaled (desflurane) anesthetics during the maintenance period. Twenty consenting patients scheduled for elective laparoscopic surgical procedures were enrolled in this prospective clinical study. Anesthesia was induced with propofol 2 mg/kg IV and fentanyl 1 micro g/kg IV, and tracheal intubation was facilitated with cisatracurium 0.3 mg/kg IV. Desflurane 4% in combination with nitrous oxide 60% in oxygen was administered for the maintenance of anesthesia. Comparative PSI and BIS values were obtained at specific time intervals during the induction, maintenance, and emergence periods. The changes in these indices were recorded after the administration of propofol (20 mg IV) or with 2% increases or decreases in the inspired concentration of desflurane during the maintenance period. With logistic regression models, both the BIS and PSI were found to be effective as predictors of unconsciousness (i.e., failed to respond to verbal stimuli) (P < 0.01). The PSI also correlated with the BIS during both the induction of (r = 0.78) and emergence from (r = 0.73) general anesthesia. However, the area under the receiver operating characteristic curve for detection of consciousness indicated a better performance with the PSI (0.95 +/- 0.04) than the BIS (0.79 +/- 0.04). During the maintenance period, the PSI values were comparable to the BIS in response to changes in propofol and desflurane but displayed greater interpatient variability. Finally, the PSI (versus BIS) values were less interfered with by the electrocautery unit during surgery (16% versus 65%, respectively). In conclusion, the PSI may prove to be a viable alternative to the BIS for evaluating consciousness during the induction of and emergence from general anesthesia, as well as for titrating the administration of propofol and desflurane during the maintenance period. However, further studies with the PSA device are needed to determine its role in anesthesia. IMPLICATIONS: The patient state index could be a useful alternative to the bispectral index for assessing level of consciousness during the induction of and emergence from anesthesia, as well as for titrating IV and volatile anesthetics during surgery.     

A comparison of frontal and occipital bispectral index values obtained during neurosurgical procedures

We placed bispectral index (BIS) sensors on the frontal and occipital areas of neurosurgical patients and compared BIS values obtained from both areas during propofol/fentanyl anesthesia. BIS showed a strong correlation between frontal and occipital montages (r(2) = 0.96; P = 0.03). It may be valid to measure BIS with the sensor on the occipital area if required during frontal neurosurgical procedures. IMPLICATIONS: Bispectral values were positively correlated when recorded from frontal and occipital sensors in patients undergoing clipping of unruptured cerebral aneurysms while anesthetized with propofol and fentanyl.     

Correlation and agreement between bispectral index and state entropy of the electroencephalogram during propofol anaesthesia

Background. Bispectral index (BIS) and state entropy (SE) monitorhypnosis. We evaluated the correlation and the agreement betweenthose parameters during propofol anaesthesia and laryngoscopywith and without muscle relaxation. Methods. A total of 25 patients were anaesthetized with propofol.At steady state (SS: BIS 40–50), they randomly receivedrocuronium (R) or saline (S); 3 min thereafter, a 20 s laryngoscopywas performed. Correlation (regression analysis) and agreement(Bland–Altman analysis) were evaluated before induction(baseline), at loss of eyelash reflex (LER), at SS and duringthe first 3 min after laryngoscopy (L). Results. The correlation coefficient r (95% CI), the mean difference(MD) (95% CI), and the limits of agreement [lower-upper limitsof 95% CI of MD (SD 1.96)] between BIS and SE were as follows.Overall recordings: 0.87 (0.83 to 0.90), 2.5 (1.2 to 3.0), and[–19.5 to 24.6]; Baseline: 0.45 (0.06 to 0.72), 7.6 (6.0to 9.2), and [–2.7 to 17.9]; LER: 0.74 (0.47 to 0.88),8.3 (3.5 to 13.2), and [–22.6 to 39.3]; SS, all patients:0.41 (0.14 to 0.63), 2.0 (–0.5 to 4.6), and [–19.0to 23.3]; SS, Group S: 0.36 (–0.07 to 0.68), 1.9 (–2.5to 6.3), and [–25.0 to 28.8]; SS, Group R: 0.63 (0.32to 0.82), 0.2 (–2.0 to 2.3), and [–14.0 to 14.4];L, all patients: 0.49 (0.32 to 0.63), 0.7 (–1.6 to 3.0),and [–25.6 to 27.1]; L, Group S: 0.41 (0.13 to 0.63),2.3 (–2.4 to 7.1), and [–36.7 to 41.3]; L, GroupR: 0.72 (0.56 to 0.83), –0.6 (–2.2 to 1.0), and[–14.3 to 13.1]. The correlation was good except for SSin Group S. The MD was significantly different from 0 for overallrecordings, during baseline and LER, but not for the other conditions.The agreement was poor except for baseline, and SS and L inGroup R. Conclusions. BIS and SE are globally well correlated. In contrast,agreement is poor as differences of more than 20 units are frequentlyobserved, except for awake and paralysed patients.     

Spectral entropy measurement of patient responsiveness during propofol and remifentanil. A comparison with the bispectral index

Background. We compared two spectral entropies, state entropy(SE) and response entropy (RE), based on the irregularity ofthe EEG, to measure loss of response to verbal command (LOR_verbal)and noxious stimulus (LOR_noxious) with the bispectral index(BIS) during propofol infusion with and without remifentanil. Methods. Three groups of 20 patients received an effect-sitecontrolled propofol infusion (Ce_PROP) starting at 1 µgml^–1 and increased in steps of 0.5 µg ml^–1at 4 min intervals. In addition, a remifentanil infusion wasmaintained at a group-dependent, fixed effect-site target concentration(Ce_REMI) (0, 2 or 4 ng ml^–1). The ability of BIS, SE orRE to predict LOR_verbal and LOR_noxious were compared with thechanges in BIS, SE and RE using logistic regression, predictionprobability (P_K), and sensitivity/specificity. Results. In all groups, BIS, SE and RE decreased with increasingCe_PROP. However, BIS decreased more smoothly than SE and REat deeper levels of sedation. At LOR_verbal, BIS₅₀, SE₅₀ andRE₅₀ increased with increasing Ce_REMI. BIS, SE and RE all detectedLOR_verbal accurately but BIS performed better at 100% sensitivity.Sensitivity/specificity for detection of LOR_verbal decreasedfor all methods with increasing Ce_REMI. LOR_noxious was poorlydescribed by all measures. Conclusion. LOR_verbal was detected accurately by BIS, SE andRE except for 100% sensitivity, where BIS performed better.Though BIS, SE and RE were influenced by remifentanil duringpropofol administration, their ability to detect LOR_verbal remainedaccurate. None of the measures predicted LOR_noxious.      

A comparison of bispectral index and entropy, or how to misinterpret both

Consciousness monitoring has become increasingly popular in general anesthesia cases, and a new technology has recently been introduced with potential advantages over the other available products. In this case report, we discuss a patient who was monitored simultaneously with Bispectral Index and Entropy and evaluate the differences between the two. More importantly, we emphasize the importance of vigilance when using new technologies and discuss the potential impact of lack of vigilance on patient outcome.     

Cerebral state index versus bispectral index during propofol–fentanyl–nitrous oxide anesthesia

Purpose  

The aim of this study was to compare the cerebral state index (CSI) and bispectral index (BIS) during propofol–fentanyl–nitrous oxide anesthesia.     

Cerebral state index during propofol anesthesia: a comparison with the bispectral index and the A-line ARX index

BACKGROUND: The objective of this study was to prospectively test the Cerebral State Index designed for measuring the depth of anesthesia. The Cerebral State Index is calculated using a fuzzy logic combination of four subparameters of the electroencephalographic signal. The performance of the Cerebral State Index was compared with that of the Bispectral Index and the A-Line ARX Index. METHODS: This study applied raw data from two previously published clinical protocols. The patients in protocol 1 were given a continuous propofol infusion, 300 ml/h, until 80% of burst suppression occurred. In protocol 2, a stepwise increased target-controlled infusion of propofol was administered to patients until loss of response to noxious stimuli while the Observer's Assessment of Alertness and Sedation was registered every 4 min. The Cerebral State Index was calculated off-line from the recorded electroencephalographic data. The Spearman rank correlation coefficient between electronic indices and the effect site concentration of propofol was calculated along with the prediction probability of each index to predict the Observer's Assessment of Alertness and Sedation level. RESULTS: The Spearman rank correlation coefficients between the Cerebral State Index, Bispectral Index, and A-Line ARX Index and the propofol effect site concentration were -0.94, -0.89, and -0.82, respectively, in protocol 1, whereas the prediction probability values between the Cerebral State Index, Bispectral Index, and A-Line ARX Index and the Observer's Assessment of Alertness and Sedation score in protocol 2 were 0.92, 0.93, and 0.91, respectively. CONCLUSION: The Cerebral State Index detects well the graduated levels of propofol anesthesia when compared with the propofol effect site concentration and the Observer's Assessment of Alertness and Sedation score.     

丙泊酚靶控输注全麻诱导时BIS值与机体应激反应的关系

目的观察丙泊酚靶控输注(TCI)用于全麻诱导时,脑电双频指数(BIS)值与应激反应的关系。方法30例气管插管全麻下手术患者随机分为三组,每组10例。Ⅰ组BIS值维持在36~45,Ⅱ组46~55,Ⅲ组56~65,分别于麻醉诱导前(T0)、插管即刻(T1)以及插管后1min(T2)、3min(T3)、5min(T4)和10min(T5)记录HR和MAP,同期抽取桡动脉血测定血糖和皮质醇。结果Ⅰ组MAP、HR于T3、T4时持续下降(P<0.05),且T3、T4时MAP低于Ⅲ组(P<0.05);Ⅱ组T4时MAP低于T0时(P<0.05);Ⅲ组血糖和皮质醇水平T2、T3时高于T0时(P<0.05或P<0.01),血糖T2~T4时较Ⅰ组升高(P<0.05或P<0.01),T3、T4时较Ⅱ组升高(P<0.05),T2、T3时皮质醇水平明显高于Ⅰ组和Ⅱ组(P<0.05或P<0.01)。结论丙泊酚TCI用于全麻诱导时,将BIS值控制在46~55,在有效减轻应激反应的同时,能维持血流动力学的相对稳定。     

频谱熵和双频指数用于测定依托咪酯血浆效应室平衡速率常数的比较

目的 比较用熵指数和脑电双频指数(BIS)测定依托咪酯单次注射后的最大效应时间(TpEAK),并藉以估计依托咪酯的血浆-效应室平衡速率常数(Ke0).方法 22例患者静脉注射最大效应负荷剂量依托咪酯后,用熵指数模块和听觉诱发电化监测仪测定从注射开始至反应熵(RE)、状态熵(SE)、BIS最低的时间(TPEAK),用TpEAx和Arden等报道的依托咪酯药代学模型,按照Minto等提出的方法计算KeO.结果 RE、SE、BIS的TpEAx中位数分别为70、70和80 s,Ke0中位数分别是1.10/min、1.10/min和1.02/min.结论 单次注射依托咪酯后,熵指数和BIS监测的TpESK和计算的Ke0相同,且有别于国外研究报道的结果.     

Differences between bispectral index and spectral entropy during xenon anaesthesia: a comparison with propofol anaesthesia

We enrolled 114 patients, aged 65–83 years, undergoing elective surgery (duration > 2h) into a randomised, controlled study to evaluate the performance of bispectral index and spectral entropy for monitoring depth of xenon versus propofol anaesthesia. In the propofol group, bispectral index and state entropy values were comparable. In the xenon group, bispectral index values resembled those in the propofol group, but spectral entropy levels were significantly lower. Mean arterial blood pressure was higher and heart rate was lower in the xenon group than in the propofol group. Bispectral index and spectral entropy considerably diverged during xenon but not during propofol anaesthesia. We therefore conclude that these measures are not interchangeable for the assessment of depth of hypnosis and that bispectral index is likely to reflect actual depth of anaesthesia more precisely compared with spectral entropy.     

Unusually low bispectral index values during emergence from anesthesia

We observed unusually low BIS values during emergence from anesthesia apparently caused by misanalysis (as "suppression") of low voltage electroencephalogram. IMPLICATIONS: When BIS values do not adequately correspond with clinical status, it is necessary to check raw electroencephalogram waveforms to more clearly characterize patient status.     

Correlation and agreement between the bispectral index vs. state entropy during hypothermic cardio‐pulmonary bypass

Background: The bispectral index (BIS) and spectral entropy enable monitoring the depth of anaesthesia. Mild hypothermia has been shown to affect the ability of electroencephalography monitors to reflect the anaesthetic drug effect. The purpose of this study was to investigate the effect of hypothermia during a cardio‐pulmonary bypass on the correlation and agreement between the BIS and entropy variables compared with normothermic conditions. Methods: This prospective clinical study included coronary artery bypass grafting patients (n=25) evaluating correlation and agreement (Bland–Altman analysis) between the BIS and both spectral and response entropy during a hypothermic cardio‐pulmonary bypass (31–34 °C) compared with nomothermic conditions (34–37.5 °C). Anaesthesia was maintained with propofol and sufentanil and adjusted clinically, while the anaesthetist was blinded to the monitors. Results: The BIS and entropy values decreased during cooling (P<0.05), but the decrease was more pronounced for entropy variables compared with BIS (P<0.05). The correlation coefficients (bias±SD; percentage error) between the BIS vs. spectral state entropy and response entropy were r²=0.56 (1±11; 42%) and r²=0.58 (?2±11; 43%) under normothermic conditions, and r²=0.17 (10±12; 77%) and r²=0.18 (9±11; 68%) under hypothermic conditions, respectively. Bias was significantly increased under hypothermic conditions (P<0.001 vs. normothermia). Conclusion: Acceptable agreement was observed between the BIS and entropy variables under normothermic but not under hypothermic conditions. The BIS and entropy variables may therefore not be interchangeable during a hypothermic cardio‐pulmonary bypass.     

艾司洛尔、拉贝洛尔和尼卡地平对气管插管期间心血管反应、脑电双频指数和熵指数的影响

目的探讨艾司洛尔、拉贝洛尔和尼卡地平对气管插管期间心血管反应、腑电双频指数(BIS)和熵指数的影响。方法 60例择期腹部手术的患者,随机均分为四组:艾司洛尔组、拉贝洛尔组和尼卡地平组、生理盐水组。四组均采用丙泊酚分步靶控输注诱导,BIS≤80时各组分别静注艾司洛尔0.3 mg/kg、拉贝洛尔0.04 mg/kg、尼卡地平0.03 mg/kg 和生理盐水。当 BIS≤50后1 min行气管插管。观察反应熵(RE)、状态熵(SE)、BIS、HR 和 MAP 的变化。结果艾司洛尔组、拉贝洛尔组和尼卡地平组 MAP、HR 在插管后1 min 显著高于插管前1 min(P<0.05或 P<0.01)。各组RE、SE、BIS 插管前后差异无统计学意义。结论艾司洛尔、拉贝洛尔或尼卡地平均可减轻患者气管插管时的心血管反应,但对 BIS、RE、SE 无显著影响。     

神经外科手术中枕部与额部脑电双频指数相关性分析的研究

目的 分析神经外科手术中枕部与额部脑电双频指数(BIS)的相关性.方法 神经外科颅内肿瘤切除术患者10例,在同侧枕部和额部分别放置电极,取诱导前10min(T1)、切皮前10 min(T2),切皮后10min(T3),切开硬膜后10min(T4),切开硬膜后30～90min(T5)各时段BIS值进行分析.结果 枕部BIS值T1时明显低于额部(P<0.01),T2～T5时明显高于额部(P<0.01).麻醉前后枕部与额部BIS值具有正相关性(r2=0.954;P=0.000).结论 在神经外科手术中,麻醉前后枕部与额部BIS值有明显差异,但同时有良好的相关性.     

肌松药对异丙酚诱导期脑电熵和脑电双频指数的影响

目的：探讨维库溴铵、琥珀胆碱对异丙酚诱导期脑电熵和脑电双频指数（bispectral index,BIS）的影响。方法：靶控输注异丙酚进行诱导,当患者OAA/S评分≤1分时置入喉罩,机械通气。调节异丙酚靶控浓度,使效应室浓度（effect-site concentration,Ce）维持在2.0μg/mL或3.0μg/mL,稳定5min。维库溴铵2.0组（V2.0组）和维库溴铵3.0组（V3.0组）分别在异丙酚Ce稳定在2.0μg/mL或3.0μg/mL时静脉推注维库溴铵0.1mg/kg,琥珀胆碱2.0组（S2.0组）和琥珀胆碱3.0组（S3.0组）则静脉推注琥珀胆碱1mg/kg,两组对照组（C2.0组,C3.0组）给予等容量的生理盐水。记录麻醉诱导前、肌松药静脉推注前（基础值）及静脉给药后第1～5分钟的BIS、反应熵（respect entropy,RE）、状态熵（state entropy,SE）。结果：与基础值比较,V2.0组、S2.0组和C2.0组静脉给药后BIS、RE、SE下降（P〈0.05）,V3.0组和S3.0组各指标变化差异无统计学意义（P〉0.05）。S2.0组和S3.0组在给予琥珀胆碱后第2分钟时点RE、SE升高（P〈0.05）,但BIS变化差异无统计学意义（P〉0.05）。V2.0组、V3.0组、S2.0组和S3.0组分别与相同异丙酚Ce对照组比较,静脉推注肌松药前后SE、BIS差异均无统计学意义（P〉0.05）,仅RE在给予琥珀胆碱后第2分钟时点升高（P〈0.05）。结论：肌松药对脑电熵和BIS的影响与镇静深度有关,在较浅的镇静状态下,肌松药可引起BIS、RE、SE数值下降;肌松药对脑电熵和BIS的影响与肌松药的种类无关。     

Comparative evaluation of the cerebral state index and the bispectral index during target-controlled infusion of propofol

Background. Cerebral state index (CSI) has recently been introducedas an intra-operative monitor of anaesthetic depth. We comparedthe performance of the CSI to the bispectral index (BIS) inmeasuring depth of anaesthesia during target-controlled infusion(TCI) of propofol. Methods. Twenty Chinese patients undergoing general anaesthesiawere recruited. CSI and BIS, and predicted effect-site concentrationof propofol were recorded. The level of sedation was testedby Modified Observer's Assessment of Alertness/Sedation Scale(MOAAS) every 20 s during stepwise increase (TCI, 0.5 µgml^–1) of propofol. The loss of verbal contact (LVC) andloss of response (LOR) were defined by MOAAS values of 2–3and less than 2, respectively. Baseline variability and theprediction probability (P_K) were calculated for the BIS andCSI. The values of BIS₀₅ and CSI₀₅, BIS₅₀ and CSI₅₀, BIS₉₅ andCSI₉₅ were calculated at each end-point (LVC and LOR). Results. Baseline variability of CSI was more than that of BIS.Both CSI and BIS showed a high prediction probability for thesteps awake vs LVC, awake vs LOR, and LVC vs LOR, and good correlationswith MOAAS values. Conclusion. Despite larger baseline variation, CSI performedas well as BIS in terms of P_K values and correlations with stepchanges in sedation.