相同MAC浓度的安氟醚和异氟醚对脑电图功率谱的影响

２４例 ２０～５０岁、ＡＳＡⅠ级、行择期外科手术的患者，随机分成两组：安氟醚组和异氟醚组。不用术前药，麻醉诱导以静脉硫喷妥钠５ｍｇ／ｋｇ、阿曲库胺０．６～０．７ｍｇ／ｋｇ。单纯吸入安氟醚或异氟醚维持全麻。气管插管后控制呼吸，维持呼气末二氧化碳分压（ＰＥＴＣＯ２）４．２７。４．９３ｈｐａ。以ＴＯＦ监测肌松，间断给予阿曲库胺 １０～１５ｍｇ，维持Ｔ４／Ｔ１＜２５％。采用 ＦＰ１－Ａ１、ＦＰ２－Ａ２双导联监护脑电，验证呼气末麻醉药浓度在 ０． ５、０．８、１． ０、１． ３和 １．５ ＭＡＣ时的脑电功率谱、９５％边缘频率（ＳＥＦ）和中心频率（ＭＰＦ）改变。结果发现，随ＭＡＣ增加脑电功率谱表现出波增加，α和β波减少，而ＳＥＦ、ＭＰＦ值随ＭＡＣ增加而减少的改变呈负性线性关系，ｒ＝－０．９５。提示脑电功率谱、ＳＥＦ和ＭＰＦ在评价全麻深度上有一定意义。     

低蛋白饮食合并必需氨基酸及a酮酸治疗慢性肾衰的疗效评价

６例慢性肾功能衰竭患者均采用治疗前低蛋白饮食（ＬＰＤ）后及低蛋白饮食合并必需氨基酸及ａ－酮酸（ＬＰＤ－ＥＡＡ－ＫＡ）后自身对照的研究。结果显示：ＬＰＤ－ＥＡＡ－ＫＡ治疗后，ＳＣｒ明显下降（Ｐ＜０．０１），ＣＣｒ明显提高（Ｐ＜０．０５），ＢＵＮ未有变化，血浆总必需氨基酸与总非必需氨基酸比率、支链氨基酸浓度均升高，且机体由负氮转为正氮平衡（Ｐ＜０．００５），蛋白质合成与分解率明显提高（均Ｐ＜０．００１     

全麻诱导气管插管时大脑皮层电活动与血流动力学的变化——比较异丙酚和硫喷妥钠的药理作用

目的：探讨数量化脑电图在反映麻醉诱导气管插管期间脑电的活动程度，以及ＥＥＧ和心血管反应相关性研究。方法：７０例ＡＳＡⅠ级病人，随机双盲分两组，组Ⅰ（ｎ＝３５）硫喷妥钠，组Ⅱ（ｎ＝３５）异丙酚。硫喷妥钠或异丙酚和琥珀胆碱行气管插管。分别于诱导前、诱导后、气管插管后１～２分和３～５分监测数量化脑电图、ＭＡＰ、ＨＲ、ＳｐＯ２的变化。结果：诱导前，两组病人的ＥＥＧ及血流动力学参数无差异。诱导后，ＥＥＧ抑制，ＳＥＦ、ＭＦ、ＢＩＳ下降，δＲ升高，但两组之间无区别；异丙酚组ＭＡＰ降低程度大于硫喷妥钠组（Ｐ＜０．０１），ＨＲ无差异。气管插管后，ＥＥＧ活化，ＳＥＦ、ＭＦ、ＢＩＳ升高（Ｐ＜０．０１），δＲ降低（Ｐ＜０．０１），异丙酚组ＥＥＧ各参数的变化程度轻于硫喷妥钠组（Ｐ＜０．０１）；异丙酚组ＭＡＰ和ＨＲ升高程度小于硫喷妥钠组（Ｐ＜０．０１）。结论：气管插管前，等效剂量的异丙酚和硫喷妥钠对中枢神经的抑制程度类似，气管插管后，异丙酚组的ＥＥＧ活化程度及血流动力学的变化明显轻于硫喷妥钠。     

静吸复合麻醉中不同小剂量芬太尼对脑电边缘频率和双波谱指数的影响

目的 研究静吸复合麻醉中不同小剂量芬太尼对脑电边缘频率（ＳＥＦ）和双小的指数（ＢＩＳ的影响。方法 随机将ＡＳＡⅠ～Ⅱ级病人３０例分为Ⅰ、Ⅱ、Ⅲ组地全麻诱导吸入安氟醚达０．８ＭＡＣ后三组分别静注芬太尼３μｇ．ｋｇ＾０－１、５μｇ．ｋｇ＾－１,于给药后６ｍｉｎ记录每组病人的ＭＡＰ、ＨＲ、ＳＥＦ及ＢＩＳ。结果 三组 内、组间ＭＡＰ、ＨＲ相比均无显著差异（Ｐ〈０．０５）,ＢＩＳ无显著性差异（Ｐ〉０．０５）     

风湿性心脏病患者心瓣膜置换术前后血浆肾上腺髓质素及肺血流动力学变化

目的 观察风湿性心脏病患者心瓣膜换术前、后血浆肾上腺髓质素（ＡＭ）及肺血流动嗅觉的变化，探讨ＡＭ在风湿性心脏病肺动脉高压中的作用。方法 采用放射免疫法测定３７例风湿性患者瓣膜置换术前。后血浆ＡＭ的浓度，Ｓｗａｎ－Ｇａｎｚ漂浮导管测定肺血流动力学指标。结果 风湿性心脏病患者术前血浆ＡＭ水平明显高于对照组（Ｐ〈０．０５），ＡＭ水平与平均肺动脉压、肺动脉楔压、肺血管阻力呈正相关（ｒ＝０．７３６，０．５９     

用脑电双频指数观察异丙酚的量效关系

以脑电双频指数（ＢＩＳ）和边缘频率（ＳＥＦ）为主要指标,观察不同剂量异丙酚推注后的量效关系。选择１２例择期行腹腔镜下手术患者,持续记录ＰＥＥＧ各指标。静脉注射阿曲库铵０６ｍｇ／ｋｇ,并以１０ｍｇ／ｓ速率注入异丙酚２ｍｇ／ｋｇ诱导,气管插管后机械控制...     

肾移植患者术后早期血浆内皮素的变化

对３２例尸体肾移植患者术前及术后早期３个月的血浆内皮素－１（ＥＴ－１）浓度进行了动态观察，同时行前列腺素Ｅ－２（ＰＧＥ－２）、血栓素Ｂ－２（ＴＸＢ－２）与环孢素Ａ（ＣｓＡ）血浓度的测定及移植肾功能与血压的监测。ＥＴ－１、ＰＧＥ－２及ＴＸＢ－２均采用放射免疫法测定，ＣｓＡ血浓度采用多克隆抗体偏振免疫荧光法（ＴＤＸ）进行。结果显示：移植前患者的血浆ＥＴ－１平均浓度为１０．２７±０．５７ｐｇ／ｍｌ，移植后３个月各阶段的ＥＴ－１值均显著降低，平均浓度为４．６２±０．１４ｐｇ／ｍｌ。与此同时，血浆Ｃｒ和ＢＵＮ值以及收缩压、舒张压也呈现相似的变化，与移植前相比有非常显著性差异（Ｐ＜０．０１），且血浆ＥＴ－１浓度的变化与移植肾功能及血压密切相关。血浆ＥＴ－１浓度可作为肾移植术后的一项监测参考指标。     

安氟醚,七氟醚和异丙酚对胸肺静态顺应性的影响

２４例ＡＳＡⅠ￣Ⅱ级在全麻下行乳癌根治术的患，分为三组：安氟醚组（Ｅ）、七氟醚组（Ｓ）和异丙酚组（Ｐｒｏ）。Ｅ、Ｓ组分别以１．０ＭＡＣ的安氟醚和七氟醚维持麻醉。Ｐｒｏ组静点异丙酚４￣６ｍｇ·ｋｇ＾－１·ｈ＾－１维持麻醉。采用吸气末气道阻断法测定胸肺静顺应性（Ｃｒｓ）。用药３０分钟后Ｃｒｓ明显降低（Ｐ〈０．０１）；Ｐｒｏ组的Ｃｒｓ下降上于Ｅ和Ｓ组（Ｐ〈０．０５）。表明：麻醉药是影响Ｃｒｓ的重要因素     

脑电双频谱分析用于地氟醚复合氧化亚氮吸入时麻醉深度的判断

目的：通过观察地氟醚复合Ｎ２Ｏ吸入麻醉过程中脑电双频谱指数（ＢＩＳ）的进一步评价ＢＩＳ在麻醉深度监测中的应用价值。方法：患者２０例,气管插管后后用５０％Ｏ２＋５０％Ｎ２Ｏ＋地氟醚维持麻醉。地氟醚初始吸入浓度６％,分别于呼气末浓度达到０．５、０．７５、１．０、１．２５６ １．５ＭＡＣ时记录ＢＩＳ、Ｂ客ＨＲ等指标,然后维持呼气末２３．９％（１．３ＭＡＣ０,１５分钟后开始手术,观察切皮时患者有无反应。术     

脑电功率谱分析用于监测手术切皮时的麻醉深度

目的：评价脑电功率谱分析技术反映麻醉深度的准确性。方法：６５例ＡＳＡⅠ级腹部手术病人，快速静脉诱导气管插管后，机械通气，维持ＰＥＴＣＯ２在正常范围内。麻醉：Ｏ２－Ｎ２Ｏ（１∶２）－七氟醚吸入，切皮前不追加长效肌松药。随机分为三组：Ⅰ组ｎ＝２５、Ⅱ组ｎ＝２０、Ⅲ组ｎ＝２０。七氟醚呼气末浓度分别为１．０％、１．５％、２．０％，至少维持１５分钟。应用数量化脑电图监测仪监测手术切皮前、后３分钟脑电图的改变，同时监测ＭＡＰ、ＨＲ的改变，切皮后四肢肌肉活动、面部表情变化、呛咳或切皮前不能耐受气管插管刺激者定为切皮反应阳性。结果：切皮前三组病人的ＥＥＧ随七氟醚呼气末浓度增加，波谱边缘频率（ＳＥＦ）、中频率（ＭＦ）、双谱指数（ＢＩＳ）明显降低（Ｐ＜０．０１），δ波比率（δＲ）明显升高（Ｐ＜０．０１），ＭＡＰ仅Ⅰ组和Ⅲ组之间有差异（Ｐ＜０．０５），ＨＲ三组之间无统计学差异。切皮反应者的ＳＥＦ、ＭＦ、ＢＩＳ明显高于无反应者，δＲ明显低于无反应者（Ｐ＜０．０１）。反应者切皮前、后的ＭＡＰ和ＨＲ变化差明显大于无反应者（Ｐ＜０．０１）。结论：ＥＥＧ数量化指标ＳＥＦ和ＢＩＳ能较准确地反映切皮前七氟醚麻醉深度。     

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.     

Variation of bispectral index under TIVA with propofol in a paediatric population

BACKGROUND: In this prospective observational study, we aim to explore the relationship between age and bispectral index (BIS) values at different plasma concentrations of propofol. METHODS: Fifty children aged from 3 to 15 yr were included. Anaesthesia was induced using a target-controlled infusion of propofol with the Kataria pharmacokinetic model together with a bolus of remifentanil followed by a continuous infusion rate at 0.2 microg kg(-1) min(-1). Target plasma propofol concentration was initially stabilized to 6 microg ml(-1) and continued for 6 min. The target was then decreased and stabilized to 4 microg ml(-1) and then to 2 microg ml(-1). BIS values, plasma propofol concentration, and EEG were continuously recorded. In order to explore the relationship between variations in propofol concentration and the EEG bispectrum, we used a multiple correspondence analysis (MCA). Results are shown in median (range). RESULTS: We found no statistical difference between BIS values with propofol 6 microg ml(-1) [23 (12-40)] and 4 microg ml(-1) [28 (9-67)]. At 2 microg ml(-1), BIS was significantly different [52 (24-71)], but a significant correlation between the age of children and BIS values was found (r2=0.66; P<0.01). There was little change in children's position between 6 and 4 microg ml(-1) in the structure model of the MCA. From 4 to 2 microg ml(-1), the position of children moved only on axis 2. CONCLUSIONS: These results showed the difficulty to interpret BIS values because of the absence of significant change for higher plasma propofol concentration variation or because of the link with age for the lower plasma concentration.     

The effect of ketamine on clinical endpoints of hypnosis and EEG variables during propofol infusion

BACKGROUND: We studied the effect of variable doses of ketamine on the endpoints of hypnosis, e.g., unresponsiveness to verbal commands (UVC), loss of eyelash reflex (LER), and inhibition of body movement response with or without sneezing to nasal membrane stimulation (INBMR), and processed EEG variables, e.g., bispectral index (BIS), 95% spectral edge frequency (SEF) and median frequency (MF) during propofol infusion. METHODS: Forty-eight patients received either propofol infusion, 30 mg.kg-1.h-1 (Group P; n = 12) or ketamine bolus, 0.25, 0.5 or 0.75 mg i.v., followed by propofol infusion, 30 mg.kg-1.h-1 + variable dose ketamine infusion, 0.25, 0.5 or 0.75 mg.kg-1.h-1 (Groups PK0.25, PK0.5 and PK0.75; n = 12 each) until UVC, LER and INBMR. BIS, 95% SEF and MF values were monitored and recorded at the endpoints of hypnosis. Propofol and ketamine concentrations were measured at INBMR. RESULTS: Propofol infusion, 30 mg.kg-1.h-1, induced UVC, LER and INBMR at BIS: 65 +/- 2, 63 +/- 9 and 33 +/- 7; 95% SEF: 17 +/- 3, 17 +/- 4 and 14 +/- 3; and MF values of 5 +/- 2, 5 +/- 3 and 3 +/- 2, respectively. With adjunctive ketamine (Groups PK0.5 and PK0.75), the hypnotic endpoints were achieved at higher BIS and 95% SEF values and lower propofol doses and concentrations as compared to Groups P and PK0.25 (9.9 +/- 5.8 and 9.4 +/- 3.4 vs. 13.4 +/- 4.5 and 14 +/- 5.8 micrograms.ml-1). CONCLUSIONS: Our results suggest additive interaction between propofol and ketamine (Groups PK0.5 and PK0.75) for achieving the hypnotic endpoints; however, ketamine did not depress the EEG variables in proportion to its hypnotic effect. The paradoxically higher BIS and 95% SEF values at the hypnotic endpoints may be due to lower propofol concentrations and/or no effect of ketamine on the EEG variables.     

Narcotrend index versus bispectral index as electroencephalogram measures of anesthetic drug effect during propofol anesthesia

The Narcotrend monitor (MonitorTechnik, Bad Bramstedt, Germany) performs an automatic analysis of the electroencephalogram (EEG) during anesthesia based on a visual assessment of the raw EEG. Its newest software version 4.0 includes a dimensionless index that, similar to the bispectral index (BIS), ranges from 100 (awake) to 0. We compared the performance of Narcotrend index and BIS as EEG measures of anesthetic drug effect during propofol anesthesia. Eighteen adult patients scheduled for radical prostatectomy were investigated. An epidural catheter was placed in the lumbar space and electrodes for BIS (version XP; Aspect Medical Systems, Natick, MA) and Narcotrend were positioned as recommended by the manufacturers. Narcotrend index, BIS values, and propofol plasma and effect site concentrations as parallelly simulated by Rugloop software (Department of Anesthesia, Ghent University, Belgium) were automatically recorded in intervals of 5 s. Induction of anesthesia consisted of a fentanyl bolus and a propofol infusion. After endotracheal intubation, patients received 15 mL bupivacaine 0.5% epidurally, and 45 min later propofol dosages were subsequently increased and decreased twice. Simulated propofol effect site concentrations ranged from 2.0 +/- 0.4 microg/mL (smallest) to 6.3 +/- 1.3 microg/mL (largest) during these subsequent increases and decreases of propofol. In terms of prediction probability (P(K)) the performance of the Narcotrend index (P(K) = 0.88 +/- 0.03) to predict propofol effect site concentrations was comparable to the BIS (P(K) = 0.85 +/- 0.04). Using the respective EEG index as a measure of drug effect the mean k(e0) was calculated as 0.20 +/- 0.05 min(-1) for Narcotrend index and 0.16 +/- 0.07 min(-1) for BIS. In the observed propofol concentration range Narcotrend index detected differences in EEG dynamics as well as BIS. IMPLICATIONS: This study in 18 adult patients undergoing radical prostatectomy describes the relationship between Narcotrend index and bispectral index versus predicted propofol effect compartment concentrations. In terms of prediction probability, the performance of the Narcotrend index and the bispectral index to predict propofol effect site concentrations was comparable.     

Changes of bispectral index during recovery from general anesthesia with 2% propofol and remifentanil in children

BACKGROUND: The bispectral (BIS) index is a pharmacodynamic measure of the effect of anesthesia on the central nervous system. The aim of this study was to investigate the relationship between BIS index and predicted plasma concentration of propofol delivered by target controlled infusion (TCI) during emergence in children. METHODS: With approval of IRB, 30 patients (2-7 years) were included in this study. Anesthesia was with TCI propofol 3-5 microg.ml(-1) and remifentanil 7.5 ng.ml(-1) to maintain BIS 40-60 and the propofol concentration was fixed at 3 microg.ml(-1) Remifentanil infusion was stopped 10 min before the end of surgery. BIS values were recorded after reducing propofol in decrement of 0.2 microg.ml(-1). BIS values were checked when spontaneous respiration occurred and children were able to obey a command (eye opening or hand grasping). RESULTS: Spearman's correlation analysis showed negative correlation between BIS and propofol plasma concentration (r = -0.559, P < 0.001). When respiration returned, mean BIS was 77.2 +/- 5.3 and propofol plasma concentration 1.6 +/- 0.3 microg.ml(-1) and when a verbal command was obeyed, BIS was 82.4 +/- 5.6 and propofol plasma concentration 1.5 +/- 0.3 microg.ml(-1). CONCLUSIONS: In preschool children, BIS moderately correlated with the predicted plasma concentration of propofol.     

Comparison of spontaneous frontal EMG, EEG power spectrum and bispectral index to monitor propofol drug effect and emergence

Background: The aim of this study was to investigate the accuracy of frontal spontaneous electromyography (SEMG) and EEG spectral edge frequency (SEF 95%), median frequency (MF), relative delta power (RDELTA) and bispectral index (BIS) in monitoring loss of and return of consciousness and hypnotic drug effect during propofol administration at different calculated plasma target concentrations.
Methods: Propofol was administered by using a target-controlled infusion at different propofol steady-state concentrations. All variables were measured simultaneously at specific calculated concentrations and endpoints.
Results: Loss of consciousness was accurately monitored by BIS, SEMG and SEF 95%, and propofol drug effect by BIS only. Return of consciousness was predicted by BIS, MF and SEF 95%. Due to the biphasic EEG pattern of propofol and the lack of reproducible data at specific propofol concentrations, the clinical usefulness of SEF 95%, MF and RDELTA was very limited. SEMG was useful to detect loss and return of consciousness, but without predictive value.
Conclusions: The BIS might be an accurate measure to monitor depth of anaesthesia and hypnotic drug effect. Other neurophysiologic measures have limited value to monitor depth of anaesthesia and hypnotic drug effect.     

Propofol anaesthesia via target controlled infusion or manually controlled infusion: effects on the bispectral index as a measure of anaesthetic depth.

Target controlled infusions (TCI) of propofol allow anaesthetists to target constant blood concentrations and respond promptly to signs of inappropriate anaesthetic depth. Studies comparing propofol TCI with manually controlled infusion (MCI) reported similar control of anaesthesia, but did not use an objective measure of anaesthetic depth. We therefore tested whether the Bispectral Index (BIS), an electroencephalographic (EEG) variable, is more stable during propofol TCI or MCI. Forty patients received midazolam and fentanyl before induction and were randomized to TCI or MCI. Target propofol concentrations in the TCI group were 3 to 8 microg/ml. The MCI group received propofol bolus (approximately 2 mg/kg) and infusion (3 to 10 mg/kg/h). Neuromuscular blockade was achieved with rocuronium. Following endotracheal intubation, nitrous oxide (66%) in oxygen was delivered and propofol infusion and fentanyl boluses were titrated against clinical signs. Blood pressure, heart rate and EEG were recorded, although the anaesthetist was blind to BIS values. The ideal BIS for general anaesthesia was defined as 50. Performance error, absolute performance error, wobble and divergence of BIS, and maximum changes in blood pressure and heart rate were compared using two-sample t-tests or rank-sum tests where appropriate. There was no difference in absolute performance errors during maintenance of anaesthesia with propofol TCI or MCI (23 +/- 11% vs 23 +/- 9%; P=0.97). The two groups did not differ significantly in performance error, wobble, divergence on haemodynamic changes. We conclude that TCI and MCI result in similar depth of anaesthesia and haemodynamic stability when titrated against traditional clinical signs.     

Bispectral Analysis of the Electroencephalogram Predicts Conscious Processing of Information during Propofol Sedation and Hypnosis

Background: The bispectral index (BIS) measures changes in the interfrequency coupling of the electroencephalogram (EEG). The purposes of this study were (1) to determine whether BIS correlates with responses to command during sedation and hypnosis induced by propofol or propofol and nitrous oxide, and (2) to compare BIS to targeted and measured concentrations of propofol in predicting participants' responses to commands.

Methods: Twenty volunteers (15 men and 5 women, aged 22-50 yr) were given propofol by computer-controlled infusion, and EEG was recorded for off-line analysis of BIS. Responses to randomly ordered verbal commands or voice plus touch were measured with two categorical scales (CS1 and CS2, respectively). All subjects received a propofol infusion targeted to achieve effect site concentrations of 1, 2, 4, 2, 1, and 0 micro gram/ml. Ten participants had repeated infusion, whereas 10 others breathed 30% nitrous oxide and oxygen and received a propofol infusion targeted for 0.5, 1, 2, 4, 2, 1, 0.5, and 0 micro gram/ml. Five minutes after each targeted concentration had been reached, CS1, CS2, and arterial propofol concentration were determined. The area under the receiver operating characteristic curve was used to compare the accuracy of (1) BIS, (2) targeted propofol concentration, (3) measured concentration, and (4) treatment history as predictors of response.

Results: Bispectral index was a strong predictor of CS1 and CS2 (P < 0.0001) and significantly more accurate than targeted or measured propofol concentrations (P < 0.0003 and P < 0.003, respectively). It also provided additional predictive power when combined with treatment history (P < 0.02). Nitrous oxide slightly decreased the probability of response at a given value of BIS (P < 0.05), but accuracy was unaffected.     

Narcotrend,bispectral index,and classical electroencephalogram variables during emergence from propofol/remifentanil anesthesia

The aim of this study was to investigate modern and classical electroencephalographic (EEG) variables in response to remifentanil and propofol infusions. We hypothesized that modern EEG variables may indicate the effects of propofol but not of remifentanil. Twenty-five patients were included in the study after the end of elective spine surgery without any surgical stimulation. Baseline values were defined with remifentanil 0.3 microg. kg(-1). min(-1) and target-controlled infusion of propofol 3.0 microg/mL. EEG changes were evaluated 1, 3, 5, 7, and 9 min after the stop of remifentanil infusion, followed by a step-by-step reduction (0.2 microg/mL) every 3 min of target-controlled infusion propofol. Narcotrend (NT; classifying EEG stages from awake to deep anesthesia), bispectral index (BIS), EEG spectral frequency bands (%), 50% (Median) and 95% percentiles (spectral edge frequency), mean arterial blood pressure, heart rate, and oxygen saturation were detected at every time point. The end of remifentanil application resulted in significant increases in %alpha, spectral edge frequency, mean arterial blood pressure, and %theta and decreases in %delta (P < 0.05). NT, BIS, Median, heart rate, and oxygen saturation were unchanged. Decreases in propofol concentration were associated with statistically significant increases in NT and BIS (P < 0.05). Thus, the sedative-hypnotic component of propofol could be estimated by modern EEG variables (NT and BIS), whereas the analgesic component provided by remifentanil was not indicated. However, during conditions without surgical stimulation, neither NT nor BIS provided an adequate assessment of the depth of anesthesia when a remifentanil infusion was used. IMPLICATIONS: We investigated modern and classical electroencephalographic (EEG) variables during emergence from propofol/remifentanil anesthesia. Modern EEG variables indicate changes of infusion in propofol, but not in remifentanil. Thus, modern EEG variables did not provide an adequate assessment of depth of anesthesia when remifentanil was used.     

Performance of bispectral index and auditory evoked potential monitors in detecting loss of consciousness during anaesthetic induction with propofol with and without fentanyl

BACKGROUND AND OBJECTIVE: To investigate and compare the performance of bispectral index (BIS) and auditory evoked response index (AAI) in detecting the transition from consciousness to unconsciousness during anaesthesia induction by propofol, alone and in combination with fentanyl. METHODS: Anaesthesia was induced with either an intravenous infusion of 30 mg kg(-1)h(-1) of propofol plus 2 microg kg(-1) of fentanyl (Group PF, n = 20) or an intravenous infusion of 30 mg kg(-1) h(-1) of propofol plus normal saline (Group P, n = 20). BIS, AAI and the doses of propofol administered were recorded at the end-point of unresponsiveness to verbal commands. The propofol plasma concentration was also measured. RESULTS: The propofol dose and plasma propofol concentration required to achieve loss of consciousness were significantly lower in patients pretreated with fentanyl (P < 0.001). The mean BIS value at loss of consciousness was significantly different between the two groups (74.10 in Group PF vs. 60.80 in Group P) (P < 0.001). However, no difference in the AAI was seen between the two groups at loss of consciousness (32.90 in Group PF vs. 31.80 in Group P) (P > 0.05). In both groups, the regression analysis values (r-values) between BIS and plasma propofol concentrations at the onset of unconsciousness were higher than those between AAI and propofol concentrations (0.553 vs. 0.180 in Group P; 0.432 vs. 0.308 in Group PF). CONCLUSIONS: These results show that a fentanyl bolus is effective in augmenting the hypnotic effect of propofol during anaesthesia induction. AAI appears to be able to measure the transition from consciousness to unconsciousness at similar values, regardless of whether or not fentanyl pretreatment is used whereas the BIS values were not independent of fentanyl pretreatment. This suggests that AAI may be a better indicator of conscious status during propofol/fentanyl anaesthesia, where it appears to be independent of the anaesthesia regimen.