脑电双频指数监测临床应用进展

脑电双频指数（BIS）是将脑电信号处理后得到的一个量化参数,主要用于监测麻醉深度。近年来的临床应用研究表明在BIS监测下调控麻醉深度能够为患者术后恢复提供更多的益处．而且BIS还可用于指导闭环靶控麻醉、监测脑缺血、预测心肺复苏的结局等。     

脑电双频指数与听觉诱发电位指数用于麻醉深度监测的临床评价

随着经济的发展，脑电（EEG）监测有望成为临床麻醉、急诊及重症监护病房的常规监测手段，其中研究较多的脑电双频指数（BIS）和听觉诱发电位指数（AEPindex，AAI）已在麻醉诱导、维持、恢复等方面显示出优势。本文旨在就近年来BIS和AAI应用于麻醉实践中的优点及不足作一综述。     

脑电双频谱指数监测在小儿全身麻醉中的应用

脑电双频谱指数（BIS）能准确、及时地反映大脑生理功能的变化。其在成人全身麻醉中有较大的应用价值，现就BIS监测的原理，在小儿麻醉中的应用、应用过程中的局限性以及应用前景等加以综述。     

肌松药对脑电双频指数监测麻醉深度的影响

脑电双频指数(bispectral index,BIS)是基于原始脑电图的一种麻醉深度监测指标,近年来已广泛用于临床.术中监测麻醉深度能提高麻醉质量和手术安全性,通过合理调控麻醉深度,减少麻醉用药量和避免麻醉并发症的发生.但是.关于BIS监测在临床麻醉中应用的实际意义或价值以及BIS值判读准确性及可能的影响因素仍是人们一直关心的热点问题,结合近期国内外有关文献,现就肌松药对BIS监测麻醉深度的影响及相关临床应用情况作一综述.     

BIS在小儿监测中的研究进展

目前，脑电双频谱指数（BIS）已被广泛应用于成人镇静状态与麻醉深度的监测，但小儿大脑发育成熟度与成人比有一定差异，因此BIS在小儿监测的应用特性备受关注。通过对这一领域研究现状进行综述以供参考。     

脑电双频指数监测临床应用的新进展

背景 麻醉深度判断一直是临床医师非常关注的问题.脑电双频指数（bispectral index,BIS）监测是目前应用最为广泛的量化麻醉深度的监测手段,随着BIS监测的普及,其应用价值也不断得到更深入的认识. 目的 就BIS临床应用的新进展作一综述. 内容 术中BIS监测可以使麻醉医师以适合的麻醉深度为目标个体化按需给药,既有助于避免麻醉过浅导致术中知晓,也可避免不必要的麻醉过深而造成的术后恢复延迟,这对于慢性肝病患者的麻醉尤其重要.术中BIS监测有助于通过避免麻醉过深加快患者术后认知功能恢复,并可能改善患者远期预后.对于围术期全脑缺血的高危患者,术中BIS突然下降可能提示脑灌注不足.BIS监测可能还有助于对心跳骤停、心肺复苏后患者的预后判断,但用于预后判断的最佳监测时间和界值仍有待进一步研究阐明. 趋向 术中BIS监测能够预防术中知晓和避免麻醉过深,降低术后谵妄的发生率,并在肝病患者神志判断和麻醉、高危手术围术期脑缺血监测及心肺复苏患者的预后判断等领域有很好的应用价值.     

麻醉深度监测现状

麻醉深度监测的手段随着麻醉技术的不同而变化,脑功能监测成为当前麻醉深度研究的热点。在不断开发的脑功能监测指标中,如脑电双频指数（BIS）、听觉诱发电位（AEP）、熵（Entropy）、脑电功率谱（PSA）、脑功能状态指数（CSI）等,只有BIS经过大样本、多中心和较全面的临床验证。虽然BIS对预防知晓的发生有一定效果,但也存在不少缺陷。由于麻醉不同成分产生的机制和作用部位不同,目前还没有一个指标能够全面、正确地反映麻醉状态的不同成分变化,所以麻醉深度监测的发展趋势应该是针对麻醉不同成分采用特异性强的指标进行综合监测和分析判断。     

单纯靶控输注雷米芬太尼对BIS和AEPI的影响

脑电双频谱指数(BIS)和听觉诱发电位指数(AE PI)是目前监测镇静和麻醉深度的良好指标,可以较好的反应应用吸入麻醉药和多数静脉麻醉药时的麻醉深度。临床麻醉中常需应用阿片类药物,然而阿片类药物对脑电到底有无影响尚无定论,这就给临床麻醉中应用阿片类药物时判断镇静深度带来     

熵指数和脑电双频指数用于丙泊酚-芬太尼麻醉深度监测的比较

熵指数[1]是近年来用于监测麻醉深度的新指标,它包括状念熵(state entropy,SE)和反应熵(response entropy,RE)两个参数.脑电双频指数(bispectral index,BIS)是临床广泛应用的麻醉镇静深度监测的可靠指标.本研究旨在比较熵指数和BIS临测丙泊酚-芬太尼麻醉深度的准确性,为临床应用提供参考.     

脑电双频指数用于小儿镇静及麻醉深度监测的研究进展

大量研究证实，脑电双频指数(BIS)与较大小儿的镇静及麻醉深度有较好的相关性，与麻醉药物浓度呈负相关，能较好地评价意识水平。但对于婴儿，BIS监测的有效性尚有待于进一步研究。     

Different conditions that could result in the bispectral index indicating an incorrect hypnotic state

Since its introduction in 1996, the Bispectral Index (BIS) has gained increasing popularity in daily anesthesia practice. However, numerous reports have been appearing in the literature of paradoxical BIS changes and inaccurate readings. The purpose of this review is to assess the utility of BIS monitoring through examining the various published reports of all BIS values not coinciding with a clinically judged sedative-hypnotic state, whether arising from an underlying pathophysiology of electroencephalographic (EEG) cerebral function or because of shortcomings in the performance and design of the BIS monitor. High electromyographic activity and electric device interference could create subtle artifact signal pollution without their necessarily being displayed as artifacts. This would be misinterpreted by the BIS algorithm as EEG activity and assigned a spuriously increased BIS value. Numerous clinical conditions that have a direct effect on EEG cerebral function could also directly influence the BIS value.     

AEP-monitor/2 derived, composite auditory evoked potential index (AAI-1.6) and bispectral index as predictors of sevoflurane concentration in children

BACKGROUND: Level of anesthesia may be predicted with the auditory evoked potential or with passive processed electroencephalogram (EEG) parameters. Some previous reports suggest the passive EEG does not reliably predict level of anesthesia in infants. The AAI-1.6 is a relatively new index derived from the AEP/2 monitor. It combines auditory evoked potentials and passive EEG parameters into a single index. This study aimed to assess the AAI-1.6 as a predictor of level of anesthesia in infants and children. METHODS: Four infants aged less than 1 year, and five older children aged between 2 and 11 years were enrolled. They all had uniform sevoflurane anesthesia for cardiac catheterization. The AAI-1.6 and bispectral index (BIS) were recorded after achieving equilibrium at 1.5%, 2% and 2.5% sevoflurane, and immediately prior to awakening. The prediction coefficient (Pk) for BIS and AAI-1.6 was calculated and compared within each age group. RESULTS: The Pk for the AAI-1.6 was low in both 0-1 and 2-11 years age groups. In the 2-12 years group, the Pk for BIS was significantly higher than the Pk for the AAI-1.6 (Pk for BIS: 0.89, Pk for AAI-1.6: 0.53, P < 0.01). In contrast in the 0-1 year age group there was no evidence for a difference between the Pk for BIS and the Pk for the AAI-1.6 (Pk for BIS: 0.74, Pk for AAI-1.6: 0.53, P = 0.25). CONCLUSIONS: This preliminary study suggests AAI-1.6 is a poor predictor of sevoflurane concentration in infants and children.     

Bispectral index-guided anesthesia in patients undergoing aortocoronary bypass grafting

In this prospective, randomized study, we compared hemodynamics, oxygenation, possible intraoperative awareness, and costs in 62 patients undergoing first-time elective coronary artery bypass grafting at 2 different levels of anesthesia. Depth of anesthesia was assessed with bispectral index (BIS). All patients were anesthetized with sufentanil/midazolam. The dosage of sufentanil/midazolam was adjusted to achieve a BIS level of 45-55 in 32 patients (Group BIS 50), whereas in 30 patients a BIS level of 35-45 was intended (Group BIS 40). Data were obtained at six different time points before, during, and after surgery. All patients were asked about possible intraoperative awareness on the third postoperative day. There were no significant differences of any hemodynamic or oxygenation variables at any time between the two groups. BIS 40 patients received significantly (P < 0.05) more sufentanil (BIS 40, 888 +/- 211 microg; BIS 50, 514 +/- 99 microg) and midazolam (BIS 40, 22.4 +/- 5.6 mg; BIS 50, 16.6 +/- 3.7 mg) than BIS 50 patients. The reduction in anesthetic drugs used saved euro;13.78/US$12.54 per patient (P < 0.05) in Group BIS 50, but one BIS electrode caused additional costs of 19.95 Euros/18.15 US dollars. Time to extubation was not significantly prolonged in Group BIS 40 (BIS 40, 14.3 +/- 4.6 h; BIS 50, 11.8 +/- 3.8 h). There was no explicit memory during anesthesia in either group. BIS-guided reduction of anesthetic medication saved costs and did not increase the risk of intraoperative awareness. However, total costs were increased by monitoring BIS, because of the BIS electrodes.     

Bispectral index guided timing of intubation without neuromuscular blockade during sevoflurane induction of anaesthesia in adults

The aim of this study was to assess the effectiveness of bispectral index monitoring (BIS) as a guide to the timing of intubation during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents in adults, and specifically, whether a target BIS value of 25 provides better intubating conditions than a target BIS of 40. Forty patients were randomized into one of two groups, a target BIS 25 (n =21) or a target BIS 40 (n =19). Patients received premedication with midazolam 20 microg/kg and fentanyl 0.5 microg/kg. Sevoflurane induction of anaesthesia was initiated and titrated to reach the target BIS value and maintained within the target range for two minutes. The trachea was then intubated, with intubating conditions being assessed using a standardized scale. The BIS 25 group had a superior median intubating score of 4 (range 3-9,[IQR 4-5]) vs the BIS 40 group with a median of 7 (5-10, [6-9], P<0.001). The time to reach target BIS values was not statistically different (BIS 25 group 6.6 min, BIS 40 group 5.1 min, P=0.054). End-tidal sevoflurane concentration upon reaching the target BIS was higher in the BIS 25 group (5.3% +/- 1.2%) vs the BIS 40 group (3.5% +/- 0.95) (P<0.001). There was no statistical difference in haemodynamic parameters between groups. A target BIS value of 25 provides good to excellent intubating conditions and better intubating conditions than a target BIS of 40 during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents.     

Predicted effect-site concentration of propofol and sufentanil for gynecological laparoscopic surgery

Background: This study was to estimate the predicted effect‐site concentration of propofol administered by a target‐controlled infusion (TCI) for maintenance of anesthesia based on the bispectral (BIS) index as a measure of hypnosis in laparoscopic surgery. Method: One‐hundred and sixty unpremedicated patients undergoing gynecologic laparoscopy were assigned randomly to receive one of the target effect‐site concentrations of propofol 2.0, 2.5, 3.0, 3.5 and 4.0 μg/ml during TCI with propofol and sufentanil. The dose–response relationship of propofol for the maintenance of adequate anesthesia based on BIS, movement and hemodynamic response was investigated using a fixed effect‐site concentration of sufentanil (0.2 ng/ml). The BIS values, hemodynamic variables, time course during emergence and intraoperative awareness were also assessed. Results: The predicted effect‐site propofol concentrations for adequate anesthesia at the skin incision in 50% (EC₅₀) and 95% (EC₉₅) of patients undergoing gynecologic laparoscopy were 2.2 and 3.7 μg/ml, respectively. The predicted propofol EC₅₀ and EC₉₅ to maintain adequate anesthesia in these patients were 2.6 μg/ml (95% CI 2.3–2.7 μg/ml) and 3.6 μg/ml (95% CI 3.3–4.0 μg/ml), respectively. The BIS values, effect‐site concentration of propofol, hemodynamic data and time course during emergence and post‐operative adverse events were comparable in each group. There were no reports of intraoperative awareness in the post‐anesthetic care unit. Conclusion: Based on the anesthetic depth assessed by the clinical signs and BIS monitoring, the predicted effect‐site propofol concentrations for the maintenance of anesthesia in patients undergoing gynecologic laparoscopy were similar in those administered adequate anesthesia at the skin incision during TCI.     

Bispectral Index asymmetry and COMFORT score in paediatric intensive care patients

BACKGROUND: The Bispectral Index (BIS) monitor has been suggested as a potential tool to measure depth of sedation in paediatric intensive care unit (PICU) patients. The primary aim of our observational study was to assess the difference in BIS values between the left and right sides of the brain. Secondary aims were to compare BIS and COMFORT score and to assess change in BIS with tracheal suctioning. METHODS: Nineteen ventilated and sedated PICU patients had paediatric BIS sensors applied to either side of their forehead. Each patient underwent physiotherapy involving tracheal suctioning. Their BIS data and corresponding COMFORT score, assessment as by their respective nurses, were recorded before, during, and after physiotherapy. RESULTS: Seven patients underwent more than one physiotherapy session; therefore, 28 sets of data were collected. The mean BIS difference values (and 95% CI) between left BIS and right BIS for pre-, during, and post-physiotherapy periods were 9.2 (5.9-12.5), 15.8 (11.9-19.7), and 7.5 (5.2-9.7), respectively. Correlation between mean BIS, left brain BIS, and right brain BIS to COMFORT score was highly significant (P<0.001 for all three) during the pre- and post-physiotherapy period, but less so during the stimulated physiotherapy period (P=0.044, P=0.014, and P=0.253, respectively). CONCLUSIONS: A discrepancy between left and right brain BIS exists, especially when the patient is stimulated. COMFORT score and BIS correlate well between light and moderate sedation.     

The relationship between bispectral index and electroencephalographic parameters during isoflurane anesthesia

Bispectral index (BIS) integrates various electroencephalographic (EEG) parameters into a single variable. However, the exact algorithm used to synthesize the parameters to BIS values is not known. The relationship between BIS and EEG parameters was evaluated during nitrous oxide/isoflurane anesthesia. Twenty patients scheduled for elective ophthalmic surgery were enrolled in the study. After EEG recording with a BIS monitor (A-1050) was begun, general anesthesia was induced and maintained with 0.5%-2% isoflurane and 66% nitrous oxide. Using software we developed, we continuously recorded BIS, spectral edge frequency 95% (SEF95), and EEG parameters such as relative beta ratio (BetaRatio), relative synchrony of fast and slow wave (SynchFastSlow), and burst suppression ratio. BetaRatio was linearly correlated with BIS (r = 0.90; P < 0.01; n = 253) at BIS more than 60. At a BIS range of 30 to 80, SynchFastSlow (r = 0.60; P < 0.01; n = 3314) and SEF95 (r = 0.75; P < 0.01; n = 3339) were linearly correlated with BIS. The correlation between BIS and SEF95 was significantly better than the correlation between BIS and SynchFastSlow (P < 0.01). At BIS less than 30, the burst suppression ratio was inversely linearly correlated with BIS (r = 0.76; P < 0.01; n = 65). At BIS less than 80, burst-compensated SEF95 was linearly correlated with BIS (r = 0.78; P < 0.01; n = 3404). In the range of BIS from 60 to 100, BIS can be calculated from BetaRatio. At surgical levels of anesthesia, BIS and SynchFastSlow (a parameter derived from bispectral analysis) or burst-compensated SEF95 (derived from power spectral analysis) are well correlated. However, our results show that SynchFastSlow has no advantage over SEF95 in calculation of BIS. IMPLICATIONS: The relationship between bispectral index (BIS) and electroencephalographic parameters was evaluated during nitrous oxide/isoflurane anesthesia. At surgical levels of anesthesia, BIS and the relative synchrony of fast and slow wave (a parameter derived from bispectral analysis) or burst-compensated spectral edge frequency 95% (a parameter derived from power spectral analysis) are well correlated.     

The bispectral index does not correlate with clinical signs of inhalational anesthesia during sevoflurane induction and arousal in children

PURPOSE: Validation of the bispectral index (BIS) in children requires correlating BIS with several levels of sedation, hypnosis and anesthesia. Our purpose was to compare BIS values with objective assessments of the level of hypnosis in children. We postulated that BIS predicted the level of anesthesia during induction and emergence in children. METHODS: In a prospective observational study, we evaluated the BIS monitor in 87 children (ages: 0.3 to 14 yr) ASA physical status I-II undergoing general surgery under sevoflurane and nitrous oxide. Clinical signs of inhalational anesthesia (CSA), the motor response to surgical incision and signs of arousal were used as indicators of the depth of anesthesia. CSA and BIS measurements were paired every minute during induction and emergence until arousal. RESULTS: CSA scores decreased during induction and increased during emergence (P < 0.001) and correlated with changes in sevoflurane concentrations (r = -0.46; P < 0.001). BIS was associated with changes in CSA scores during induction (r = 0.49; P < 0.01) and emergence (r = 0.62; P < 0.01), but the ranges of individual BIS values overlapped several levels of hypnosis. A BIS value greater than 50 had a positive predictive value of 25% for distinguishing between responders and non-responders to surgical incision. A BIS score equal or greater than 72 had a predictive value of 63% for discriminating between pre-arousal and arousal. CONCLUSIONS: BIS correlates with several levels of hypnosis during inhalational induction and emergence in children, but individual BIS values show large inter-individual variability. The BIS monitor identified the physiological changes associated with arousal and distinguished the effects of preoperative sedation during emergence. The use of movement as an endpoint of hypnosis during surgical stimulation does not correlate with BIS values in children. The large inter-individual variability of BIS at different levels of anesthetic depth may limit the applicability of BIS to pediatric anesthesia.     

The bispectral index: a measure of depth of sleep?

How does physiological sleep affect the Bispectral Index (BIS)? We collected electroencephalographic (EEG) data from five subjects during the early part of the night, comparing the changes in the BIS with the conventional EEG stages of sleep. We found that the BIS was a consistent marker of depth of sleep. Light sleep occurred at BIS values of 75-90, slow-wave sleep occurred at BIS values of 20-70, and rapid eye movement sleep occurred at BIS values of 75-92. The effects of natural sleep on the BIS seem to be similar to the effects of general anesthesia on the BIS. The BIS may have a role in monitoring depth of sleep. IMPLICATIONS: Electroencephalographic data were collected from five subjects during sleep. We found that the Bispectral Index decreased during increasing depth of sleep in a fashion very similar to the decrease in Bispectral Index that occurs during general anesthesia. This study further highlights the electroencephalographic similarities of states of sleep and general anesthesia.