SNAP指数监测瑞芬太尼-异丙酚麻醉患者镇静深度的可行性

目的 探讨SNAP指数（SI）监测异丙酚一瑞芬太尼麻醉患者镇静深度的可行性。方法 40例择期全麻手术男性患者，ASA Ⅰ或Ⅱ级，年龄18～60岁，体重指数20～30kg／m^22，随机分为R0、R2、R4、R6组，每组10例。R0组麻醉诱导时靶控输注（TCI）0．9％生理盐水，R2、R4、R6组分别以效应室靶浓度2、4、6n/MLTCI瑞芬太尼，输注10min时开始TCI异丙酚，异丙酚初始效应室靶浓度均为1．5μg／ml，每4min增加0．5μg／ml，改良警觉／镇静（OAA／S）评分为1分时给予强直刺激，记录在临床目标（改良OAA／S评分为1分、睫毛反射消失、对强直刺激反应消失）出现时SI、脑电双频谱指数（BIS）、异丙酚效应室靶浓度（Ct）、异丙酚效应室浓度（Ce），并对SI与改良OAMS评分、BIS、Ct、Ce进行直线相关分析。结果 SI与改良OAA／S评分、BIS呈正相关，SI与Ct（除外R4组）及Ce（除外R2组）呈负相关；四组睫毛反射消失时SI差异无统计学意义（P〉0．05）；与R0组比较，对强直刺激反应消失时其它三组SI升高，Ct及Ce降低（P〈0．05）。结论 SI可用于瑞芬太尼-异丙酚麻醉患者镇静深度的监测。     

The contribution of remifentanil to middle latency auditory evoked potentials during induction of propofol anesthesia

There is a debate regarding whether opioids, as a component of general anesthesia, are adequately reflected in the assessment of anesthesia based on derivatives of the electroencephalogram. To test the hypothesis of a possible quantitative contribution of remifentanil on middle latency auditory evoked potentials, we studied its interaction with propofol anesthesia in 45 unpremedicated male patients undergoing elective lower limb orthopedic surgery. They were allocated randomly to three groups. The first two groups received remifentanil either with a high (8 ng mL(-1)) or a low (3 ng mL(-1) target concentration using target-controlled infusion (TCI). The third group received spinal anesthesia instead of remifentanil. Anesthesia was induced by a stepwise increase in propofol concentration using TCI. The auditory evoked potential index (AEPex) and calculated propofol effect site concentrations were determined at loss of consciousness and the reaction to laryngeal mask airway insertion was noted. The propofol infusion was then converted to a closed-loop TCI using an AEPex value of 40 as the target. We found no significant contribution of remifentanil alone on the auditory evoked response, whereas increasing concentrations of remifentanil led to a significant decrease of the calculated propofol effect site concentrations (P = 0.023) necessary for unconsciousness. Prediction probability for AEPex was inversely related to the remifentanil concentration and was best for the control group, which received propofol alone. These results support previous findings of a quantitative interaction between remifentanil and propofol for loss of consciousness but question the specific contribution of remifentanil to auditory evoked potentials.     

Electroencephalographic approximate entropy changes in healthy volunteers during remifentanil infusion

BACKGROUND: The aim of this study was to investigate the independent effect of remifentanil on the approximate entropy (ApEn) in frontoparietal montages. The authors investigated which montages were relevant to assess the remifentanil effect on the electroencephalogram. Spectral edge frequency and the canonical univariate parameter were used as comparators. METHODS: Twenty-eight healthy volunteers were enrolled. With recording of the electroencephalogram at the F3, F4, Cz, P3, and P4 montages, remifentanil was infused at the rate of 1-8 mug . kg . min for 15-20 min. The relation between remifentanil concentration and the electroencephalographic parameters were tested by Spearman correlation. Signal-to-noise ratio, artifact robustness, coefficient of variation of the median baseline and maximal electroencephalographic effects, and ratio of average maximal electroencephalographic effect to interindividual baseline variability were measured. The performance of ApEn as an index of remifentanil effect site concentrations was tested by prediction probability. RESULTS: Approximate entropy showed significant correlation (R = -0.6465, P < 0.0001) with remifentanil concentration. It provided comparable signal-to-noise ratio, artifact robustness, and ratio of average maximal electroencephalographic effect to interindividual baseline variability to 95% spectral edge frequency. The coefficients of variation of the median baseline and maximal electroencephalo graphic effects were smallest in ApEn. Parietal montages showed higher ratios of average maximal electroencephalographic effect to interindividual baseline variability for all electroencephalographic parameters and lower coefficients of variation of the baseline values for ApEn and 95% spectral edge frequency than frontal montages. The prediction probability of ApEn was 0.7730. CONCLUSIONS: Approximate entropy derived from a parietal montage is appropriate for the assessment of the remifentanil effect on the electroencephalogram.     

Comparison of bispectral EEG analysis and auditory evoked potentials for monitoring depth of anaesthesia during propofol anaesthesia

We have compared the auditory evoked potential index (AEPIndex) andbispectral index (BIS) for monitoring depth of anaesthesia in spontaneouslybreathing surgical patients. Twenty patients (aged 17-49 yr) undergoing daysurgery were anaesthetized with computer-controlled infusions of propofol.The mean (SD and range) of each measurement was determined duringconsciousness and unconsciousness and at specific times during theperioperative period. Mean values for AEPIndex during consciousness andunconsciousness were 74.5 (SD 14.7) 36.7 (7.1), respectively. BIS had meanvalues of 89.5 (SD 4.6) during consciousness and 48.8 (16.4) duringunconsciousness. AEPIndex and BIS were greater during consciousnesscompared with during unconsciousness. The average awake values of AEPIndexwere significantly higher than all average values during unconsciousnessbut this was not the case for BIS. BIS increased gradually during emergencefrom anaesthesia and may therefore be able to predict recovery ofconsciousness at the end of anaesthesia. AEPIndex was more able to detectthe transition from unconsciousness to consciousness.     

异丙酚病人自控镇静与靶控镇静的对比研究

目的 比较异丙酚病人自控镇静术（PCS）与靶控镇静术（TCI）在硬膜外麻醉中的应用价值。方法 32例行下肢或下腹部手术的成年患者,硬膜外麻醉满意后,随机分成两组,PCS组行病人自控镇静,单次剂量0.3mg/kg,锁定时间2min;TCI组行靶控输注,术中维持镇静深度于OAA/S镇静评分3分。监测不同时点的镇静评分、双频谱指数（BIS）、边缘频率（95％SEF）、异丙酚靶浓度（CP）及血药浓度（Cm）、术中遗忘及镇静满意程度,并比较BIS、95％SEF及Cm与镇静评分的相关性。结果 所有患者均对镇静效果满意,PCS组镇静深度较浅,异丙酚用药量较TCI组少（分别为 2.5mg·kg-1·h-1与 3.8mg·kg-1·h-1,P<0.01）,且个体差异明显。TCI组血药浓度平稳,并与靶浓度基本相符,术中及术后遗忘率较自控镇静组高（分别为31％与69％,P<0.01）。BIS与镇静评分的相关性（γ=0.73）较95％SEF及Cm高。结论 两种方法镇静效果均满意,但又各具特点。自控镇静体现了个体化给药原则,用药量较少,其合理的设置至关重要。靶控镇静的深度平稳且易于调控,遗忘良好,但由于其治疗窗较窄,需要有良好的监测。BIS是监测硬膜外麻醉中镇静深度的较敏感指标。     

Effect-site modelling of propofol using auditory evoked potentials

Auditory evoked potentials (AEP) were used to monitor central nervous system effects during induction and recovery from anaesthesia produced by infusion of propofol 30 mg kg-1 h-1 in 22 healthy male patients. Non- parametric and parametric modelling techniques were used successfully to calculate the parameter keo which linked pharmacokinetic with pharmacodynamic aspects of drug action in only 15 of the study patients. In the non-parametric analysis, keo was found to have a mean value of 0.2 (range 0.1-0.36) min-1. Estimation of keo allowed calculation of the effect-site concentration (Ce50) associated with 50% of AEP effect for the population (2.08 micrograms ml-1; 95% confidence limits 1.7-2.45). There were no significant differences between keo values calculated by non-parametric and individual parametric modelling techniques. During recovery, 50% of patients demonstrated evidence of waking at an effect-site concentration of 2.28 micrograms ml-1.      

听觉诱发电位指数及脑电双频谱指数与芬太尼复合异丙酚镇静深度的相关性

目的 分析听觉诱发电位指数（AAI）及脑电双频谱指数（BIS）与芬太尼复合异丙酚镇静深度的相关性。方法拟在全麻下行腹部手术病人45例，年龄40-55岁，随机分为3组（n=15）：异丙酚组（P组）、芬太尼2μg／kg复合异丙酚组（FP2组）以及芬太尼5μg／kg复合异丙酚组（FP5组）。P组、FP2组、FP5组分别静脉注射生理盐水5ml、芬太尼2、5μg／kg麻醉诱导。4min后以血浆靶浓度（Cp）1．0μg／ml TCI异丙酚，以后每3分钟递增0．2μg／ml，直至警觉，清醒评分（OAA／S评分）达到1分。分别于病人人室平卧10min（基础值）、注射芬太尼后4min、每次调整异丙酚Cp前即刻记录AAI、BIS、平均动脉压（MAP）、心率（HR）、脉搏血氧饱和度（SpO2）、Cp、效应室浓度（Ce），并进行OAA／S评分，对AAI及BIS与OAA／S评分间进行等级相关分析。结果P组、FP2组、FP5组AAI及BIS与OAA／S评分间均呈正相关。三组间BIS与OAA／S评分间相关程度逐渐降低（P〈0．05），而组间AAI与OAA／S评分间相关程度比较差异无统计学意义。在病人对呼唤反应消失时，随着芬太尼剂量的增加，BIS逐渐升高，而AAI差异无统计学意义。结论AAI可以监测芬太尼复合异丙酚的镇静深度，而BIS则不能。     

Auditory evoked potentials index versus bispectral index during propofol sedation in spinal anesthesia

Purpose  It is still controversial whether an electroencephalogram could be a useful monitor of sedation levels. The present study was performed to compare the bispectral index (BIS) and the auditory evoked potentials index (AAI) during light sedation with propofol infusion in spinal anesthesia. Methods  Eighty patients, aged 20 to 70 years, scheduled for surgery of the lower extremities under spinal anesthesia were assigned to one of four groups (20 patients each). Patients in the AAI propofol and BIS propofol groups were sedated with propofol infusion at an initial rate of 2 mg·kg⁻¹·h⁻¹. Propofol infusion was controlled to try to keep the observer’s assessment of alertness/sedation (OAAS) scale at 3 or 4. Patients in the AAI control and BIS control groups did not receive propofol. Results  The OAAS scales and the AAI or BIS decreased significantly in all groups during surgery, while the decrease was larger in the AAI propofol and BIS propofol groups. The AAI was significantly lower along with lower OAAS scales. There was no overlap in the AAI between OAAS scale 3 and scale 5 in the AAI propofol group, while in the BIS propofol group, no difference was observed in the BIS among OAAS scales 2, 3, 4, and 5. Conclusion  The AAI, but not the BIS, could discriminate slight changes of consciousness during light sedation with propofol infusion in patients with spinal anesthesia. This work was done at the Department of Anesthesiology, Ofuna Chuo Hospital, Kanagawa, Japan.     

ARX-derived auditory evoked potential index and bispectral index during the induction of anesthesia with propofol and remifentanil

A new commercial auditory evoked potential (AEP) monitor (A-line AEP monitor) was developed to calculate an index (ARX AEP index; AAI) by automatically using the amplitudes and latencies of the AEP. We investigated 30 patients before spine surgery. AAI; bispectral index (BIS); relative (%) delta, theta, alpha, and beta; spectral edge frequency; median frequency; mean arterial blood pressure; heart rate; and oxygen saturation were obtained simultaneously during stepwise (1.0 micro g/mL) induction of target-controlled propofol concentration until 5.0 micro g/mL, followed by an infusion of 0.3 micro g. kg(-1). min(-1) of remifentanil. Every minute, the patients were asked to squeeze the observer's hand. Prediction probability (Pk), receiver operating characteristic, and logistic regression were used to calculate the probability to predict the conditions AWAKE, UNCONSCIOUSNESS (first loss of hand squeeze), and steady-state ANESTHESIA (5.0 micro g/mL of propofol and 0.3 micro g. kg(-1). min(-1) of remifentanil). Although a statistically significant difference among the conditions was observed for AAI, BIS, mean arterial blood pressure, median frequency, and %alpha, only AAI and BIS were able to distinguish UNCONSCIOUSNESS versus AWAKE and ANESTHESIA versus AWAKE with better than Pk = 0.90. The modern electroencephalographic variables AAI and BIS were superior to the classic electroencephalographic and hemodynamic variables to distinguish the observed anesthetic conditions. IMPLICATIONS: The modern electroencephalographic ARX-derived auditory evoked potential index and the bispectral index were superior to the classic electroencephalographic and hemodynamic variables for predicting anesthetic conditions. Variables derived from the auditory evoked potential did not provide an advantage over variables derived from spontaneous electroencephalogram.     

BIS和AEPI监测镇静深度的评价

目的比较脑电双频指数（BIS）和听觉诱发电位指数（AEPI）在丙酚靶控镇静深度的临床价值.方法45例腰-硬联合麻醉术中需丙泊酚镇静病人,ASA I级,腰麻平面确定后开始丙泊酚靶控输注镇静.结果（1）丙泊酚镇静期BIS、AEPI逐渐降低,苏醒期逐渐升高（P＜0.01）,而AEPI则在意识转换过程中变化更敏感（P＜0.01）.（2）在丙泊酚镇静期和苏醒期BIS、AEPI与丙泊酚EC密切相关.（3）在丙泊酚镇静期,联合监测当BIS≤63和AEPI≤30时敏感度即可达100%.结论BIS和AEPI是监测麻醉镇静深度的良好指标,BIS和AEPI联合监测提高了诊断的敏感度.     

Target-controlled infusion anesthesia with propofol and remifentanil compared with manually controlled infusion anesthesia in mastoidectomy surgeries

Target-controlled infusion (TCI) system is increasingly used in anesthesia to control the concentration of selected drugs in the plasma or at the site of drug effect (effect-site). The performance of propofol TCI delivery when combined with remifentanil in patients undergoing elective surgeries has been investigated. Our aim in this study was to assess the anesthesia profile of the propofol and remifentanil target controlled infusion (TCI) anesthesia as compared to the manually controlled infusion (MCI), in mastoidectomy surgery, where a bloodless field is of utmost importance to the surgeon. Sixty patients, aged 18-60 years ASA I-II enrolled in the study, were divided into two equal groups. Group MCI received propofol and remifentanil by conventional-dose-weight infusion method, and Group TCI received propofol 4 microg/ml and remifentanil 4 ng/ml as effect-site target concentration. The hemodynamic variability, recovery profile, postoperative nausea and vomiting (PONV), surgeons satisfaction were assessed. Results were analyzed by SPSS version 11.5. The two groups were comparable with respect to age, ASA class, sex, weight, basal vital signs, operation time. The blood pressure and pulse were above desired levels in some data points in the MCI Group (P < or = 0.05). The PACU stay time to reach Aldret score of 10 was longer in the MCI Group (42.54 +/- 8 vs 59.01 +/- 6 min) (P < or = 0.05). The PONV was more common in the MCI Group (P < or = 0.05). Surgeon's satisfaction of the surgical field showed no significant differences except when described as "good", more common in the TCI Group. TCI is capable to induce and maintain anesthesia as well as MCI. In some stages of anesthesia, the TCI control of vital signs are better than the MCI. In some stages of anesthesia, the TCI control of vital signs are beter than the MCI. Recovery profile and complication rate and surgeon's satisfactions are more acceptable in the TCI than in the MCI Group.     

Ability of the bispectral index, autoregressive modelling with exogenous input-derived auditory evoked potentials, and predicted propofol concentrations to measure patient responsiveness during anesthesia with propofol and remifentanil

BACKGROUND: This study was conducted to compare the performance accuracy of the independent variables Bispectral Index (BIS), A-Line ARX index (AAI), and predicted propofol effect-site concentration (CePROP) to measure the dependent variables of loss of responses to different stimulation defined as loss of response to verbal command (LORverbal), eyelash reflex (LORlash), and noxious stimulus (LORnoxious) during stepwise increased levels of propofol infusion with and without remifentanil. METHODS: Forty-five patients were randomly allocated to one of three groups (0, 2, and 4 ng/ml remifentanil) to receive graded CePROP and predicted effect compartment controlled remifentanil (CeREMI). At every step, the ability to respond to verbal command using the Observer's Assessment of Alertness/Sedation Scale (OAA/S), eyelash reflex, and electrical tetanic noxious stimulus were compared against BIS, AAI, and CePROP. Prediction probability and sensitivity/specificity were calculated. RESULTS: Increasing CeREMI increased BIS and AAI values at LORverbal and LORlash and decreased CePROP. Similar findings were found for LORnoxious. The overall prediction probability to measure the hypnotic component of anesthesia remained accurate in the three groups for BIS, AAI, and CePROP. Combined information from CePROP, CeREMI, and BIS or AAI increased the overall prediction probability for predicting the OAA/S scale and LORlash. Less accuracy to LORnoxious was found in all independent variables. CONCLUSIONS: Although BIS, AAI, and CePROP were influenced by remifentanil during propofol administration, their ability to detect OAA/S and LORlash remained accurate. Improved performance is obtained when BIS and AAI are measured in conjunction with drug targeted effect-site concentrations. Remifentanil decreases the ability of these independent variables to detect LORnoxious.     

Precision and bias of target controlled propofol infusion for sedation

Background. The purpose of this study is to test precision andsystematic bias of a target controlled infusion (TCI) of propofolin human volunteers at two sedative concentrations. Methods. We studied the ‘Diprifusor’ model (MarshPharmacokinetics and a Graseby® 3400 infusion pump) in 18human volunteers at two sedative target plasma concentrations(0.5 and 1.0 µg ml^–1). Twenty minutes after infusionstart or change and 20 min after discontinuation of the infusionplasma propofol concentrations were measured using liquid chromatography–massspectroscopy (LC-MS). Plasma propofol concentrations were comparedwith concentrations predicted by the TCI system. Agreement ofthose two measures (precision and bias) was determined usingregression analysis. Results. We found little systematic bias but poor precision.When setting the TCI system to deliver a plasma concentrationof 1.0 µg ml^–1 one can predict the actual plasmaconcentration with 95% confidence only within a range of 0.44–1.38µg ml^–1. Conclusions. This finding helps to explain differences in responsesto propofol sedation; pharmacokinetic variability appears tobe an important factor.      

靶控异丙酚镇静时脑电双频指数和听觉诱发电位指数监测意识状态的比较

目的 在靶控输注异丙酚镇静时比较脑电双频指数（BIS）和听觉诱发电位指数（AEPindex)监测意识状态的准确性。方法 16例病人在全麻诱导前用异丙酚靶控输注镇静，同时监测BIS和AEPindex，用逻辑回归、ROC曲线（Receiver Operating Characteristic)过程、以及灵敏度和特异性比较两种方法监测意识状态的准确性。结果 BIS和AEPindex均能很好的反映病人镇静时的意识状态（P＝0．01），AEPindex的ROC曲线下面积与BIS的ROC曲线下面积相比，差异无统计学意义（P＞0．05），镇静警醒评分（OAA／S）从2恢复到3时AEPindex从42急剧上升至67（P＞0．01），而BIS则从64逐渐上升至72（P＞0．05），提示AEPindex对患者意识状态的差别力更好。OAA／S与BIS、AEPindex和靶控浓度有显著相关性（r分别是0．781、0．684和－0．580，P均＜0．01）。结论 AEPindex和BIS均能正确反映靶控输注异丙酚镇静时的镇静深度，AEPindex对意识（有／无）的鉴别更佳，而BIS能很好的反映意识恢复的渐进性过程。     

右美托咪定对瑞芬太尼复合丙泊酚靶控输注全麻的影响

目的观察预先给予右美托咪定对瑞芬太尼复合丙泊酚靶控输注(TCI)全麻的影响。方法择期全麻行妇科腹腔镜手术患者40例,随机均分为右美托咪定组(D组)和对照组(C组),D组诱导前15min静脉泵注右美托咪定0.8μg/kg,C组则给予等量生理盐水。观察注药前(T1)、麻醉诱导前(T2)、插管前即刻(T3)、插管后即刻(T4)、插管后3min(T5)、拔管后即刻(T6)、拔管后3min(T7)的BIS、MAP、HR、肾上腺素(E)、去甲肾上腺素(NE)浓度变化;记录丙泊酚和瑞芬太尼的用量、麻醉恢复情况,随访术后延迟性呼吸抑制、术中知晓情况。结果 T2时D组BIS明显低于T1时和C组(P<0.01);与D组比较,T2、T4、T6时C组MAP明显升高,HR明显增快(P<0.05或P<0.01);T4、T6时C组的E、NE浓度明显高于T3时和D组(P<0.01),而D组则无明显变化;D组丙泊酚和瑞芬太尼的用量明显少于C组(P<0.05);D组拔管期间体动、呛咳的发生率明显低于C组(P<0.01),两组呼吸恢复时间、睁眼时间、拔管时间组间差异无统计学意义。结论瑞芬太尼复合丙泊酚靶控输注全麻预先静注右美托咪定0.8μg/kg可产生明显的镇静效应,有效抑制患者的应激反应,减少麻醉药的用量,且不延长麻醉恢复时间。     

丙泊酚复合瑞芬太尼靶控输注在无痛支气管镜检查中的应用

目的观察三种丙泊酚复合瑞芬太尼靶控输注(TCI)诱导给药方法在无痛支气管镜检查中对患者生命体征的影响。方法择期行支气管镜检查的患者60例,随机均分为快速组、平滑组和阶梯组。麻醉诱导分别按效应室浓度输注丙泊酚至6.0μg/ml、瑞芬太尼至4.0 ng/ml。达靶浓度后入镜并随即调整丙泊酚浓度至2.0μg/ml、瑞芬太尼至2.0 ng/ml。分别记录患者吸氧前(T0)、诱导开始1 min(T1)、入镜即刻(T2)、入镜后1 min(T3)、2 min(T4)、5 min(T5)及术毕(T6)的MAP、HR及SpO2。结果阶梯组的达靶时间和入睡时间均显著长于快速组和平滑组(P<0.05或P<0.01)。阶梯组在T2时MAP显著高于其它两组(P<0.05),低血压发生率明显降低(P<0.05)。结论 TCI丙泊酚与瑞芬太尼用于无痛支气管镜检查时,阶梯法诱导较快速法、平滑法使患者血压更平稳,但可控性稍差。     

Predictive performance of computer-controlled infusion of remifentanil during propofol/remifentanil anaesthesia

Background. The predictive performance of the available pharmacokineticparameter sets for remifentanil, when used for target-controlledinfusion (TCI) during total i.v. anaesthesia, has not been determinedin a clinical setting. We studied the predictive performanceof five parameter sets of remifentanil when used for TCI ofremifentanil during propofol anaesthesia in surgical patients. Methods. Remifentanil concentration–time data that hadbeen collected during a previous pharmacodynamic interactionstudy in 30 female patients (ASA physical status I, aged 20–65 yr)who received a TCI of remifentanil and propofol during lowerabdominal surgery were used in this evaluation. The remifentanilconcentrations predicted by the five parameter sets were calculatedon the basis of the TCI device record of the infusion rate–timeprofile that had actually been administered to each individual.The individual and pooled bias [median performance error (MDPE)],inaccuracy [median absolute performance error (MDAPE)], divergenceand wobble of the remifentanil TCI device were determined fromthe pooled and intrasubject performance errors. Results. A total of 444 remifentanil blood samples were analysed.Blood propofol and remifentanil concentrations ranged from 0.5to 11 µg ml^–1 and 0.1 to 19.6 ng ml^–1respectively. Pooled MDPE and MDAPE of the remifentanil TCIdevice were –15 and 20% for the parameter set of Mintoand colleagues (Anesthesiology 1997; 86: 10–23), 1 and21%, –6 and 21%, and –6 and 19% for the three parametersets described by Egan and colleagues (Anesthesiology 1996;84: 821–33, Anesthesiology 1993; 79: 881–92, Anesthesiology1998; 89: 562–73), and –24 and 30% for the parameterset described by Drover and Lemmens (Anesthesiology 1998; 89:869–77). Conclusions. Remifentanil can be administered by TCI with acceptablebias and inaccuracy. The three pharmacokinetic parameter setsdescribed by Egan and colleagues resulted in the least biasand best accuracy. Br J Anaesth 2003; 90: 132–41     

Changes in the rapidly extracted auditory evoked potentials index and the bispectral index during sedation induced by propofol or midazolam under epidural block

Background. The bispectral index (BIS) and the rapidly extractedauditory evoked potentials index (A-line ARX Index or AAI) havebeen proposed as methods to measure the depth of sedation. Aprospective study was designed to assess the performance ofboth these methods for measuring the depth of sedation inducedby propofol or midazolam under epidural block. Methods. Thirty-two ASA I and II adult patients undergoing electivegynaecological surgery under low-thoracolumbar epidural blockwere studied. Eighteen patients received propofol (Group P:20 mg bolus every 3 min) and 14 received midazolam (Group M:0.5 mg bolus every 5 min) until an observer’s assessmentof alertness/sedation (OAA/S) scale score of 1 was achieved.AAI and BIS were monitored for different OAA/S scores. Results. AAI and BIS decreased and increased following the changeson the patients’ OAA/S scores and correlated with sedationsignificantly. During the onset phase, the coefficients of Spearman’srank correlation for AAI and BIS were respectively 0.958 and0.898 (P<0.001) for Group P, and 0.973 and 0.945 (P<0.001)for Group M. During the recovery phase in Group P, the coefficientswere respectively 0.946 and 0.702 (P<0.001). Linear regressionanalysis showed that both AAI and BIS were linearly relatedto the OAA/S scores. The coefficients of Spearman’s rankcorrelation and linear regression for AAI were all greater thanthose for BIS (P<0.05). Conclusions. Both AAI and BIS correlated well with the depthof sedation induced by propofol or midazolam under epiduralblock. AAI may be more valuable when monitoring depth of sedation. Br J Anaesth 2002; 89: 260–4     

Comparison of remifentanil and propofol infusions for sedation during regional anesthesia

Background and Objectives. Patients treated with regional anesthesia often require concomitant medication for comfort and sedation. Propofol is widely used for this purpose. Remifentanil, a new ultra-short-acting opioid, exhibits at low doses distinct sedative properties that may be useful for supplementation of regional anesthesia. This study compared the effectiveness of remifentanil and propofol infusions for providing sedation during regional block placement and surgery. Methods. In an open, prospective trial, 28 patients were randomly allocated to receive continuous infusions of remifentanil (6 μg/kg/h) or propofol (3 mg/kg/h) for sedation during spinal or axillary regional anesthesia. Infusion rates were titrated to maintain a sedation level ≥ 2 as assessed with the Observer's Assessment of Alertness Scale. Vital signs were measured continuously, during and for 2 hours after ending study drug infusion. Results. Similar scores for comfort and sedation were obtained in both groups during placement of the regional block and during surgery. Degree of sedation correlated with drug infusion rate of remifentanil (P < .002) but not for propofol. Respiratory rate decreased in the remifentanil group in absence of surgery (P < .05). Mean arterial pressure and heart rate were 20% lower in the propofol group (P < .05). Return to alertness occurred after 10 ± 6 minutes in the remifentanil group and after 16 ± 15 minutes in the propofol group. Similar incidences of hypotension, bradycardia, and nausea and vomiting were found in both groups, but intraoperative respiratory depression and nausea were more prominent in the remifentanil group. Conclusions. When titrated to the same sedation level, remifentanil provided a smoother hemodynamic profile than propofol during regional anesthesia. The frequent occurrence of remifentanil-induced respiratory depression requires cautious administration of this agent. The incidence of adverse reactions seen with both agents during and after their administration makes the management of such sedative infusion techniques difficult.