听觉诱发电位指数和脑电指数用于全麻恢复期麻醉深度监测的比较

目的 比较听觉诱发电位指数(AAI)、双频谱指数(BIS)、95％边缘频率(SEF)及血液动力学参数监测异丙酚-异氟醚静吸复合全麻恢复期麻醉深度的准确性。方法 选择36例ASAI-II级,听力正常的择期手术病人,实施异丙酚-异氟醚复合麻醉,于麻醉恢复期各时点记录AAI、BIS、SEF及血液动力学参数,并研究AAI与其他指标的相关性。结果 对呼名有反应前后AAI分别为36.1±11.5和52.4±12.3,BIS为71.9±11.5和78.6±11.9,SEF分别为16.7±3.0和18.6±3.2。结论(1)AAI、BIS、SEF均能监测恢复期麻醉深度,以AAI较为敏感。血液动力学指标对恢复期麻醉深度监测意义不大。(2)AAI在呼名有反应时突然升高,能区分有意识和无意识状态,是预测意识恢复的最好指标。     

听觉诱发电位指数和脑电指数用于监测全麻深度的比较性研究

目的　比较听觉诱发电位指数 (AAI) ,双频谱指数 (BIS)在监测全麻诱导及恢复期的准确性。方法　ASAⅠ -Ⅱ级听力正常的择期腹部手术病人 ,随机分为Ⅰ组 (对照组n =15 )和Ⅱ组 (咪唑安定组 n =15 ) ,实施异丙酚 -异氟醚或异丙酚 -咪唑安定 -异氟醚复合麻醉 ,记录麻醉诱导及恢复期各时间点AAI、BIS、HRV及血液动力学参数 ,并研究AAI与其它指标的相关性。结果　 (1)AAI反应时间较BIS明显缩短。 (2 )OAA/S镇静评分与BIS、AAI显著相关 (r =0 .93 3、0 .5 3 3、P <0 .0 1)。 (3 )苏醒时 (对呼名有反应 )AAI、BIS的变化两组间差异无统计学意义。结论　AAI、BIS均能监测麻醉诱导及恢复期麻醉深度 ,AAI反应更快 ,趋于实时监测。     

老年病人瑞芬太尼复合异丙酚靶控输注全凭静脉麻醉的效果

目的比较成年和老年病人瑞芬太尼复合异丙酚靶控输注(TCI)全凭静脉麻醉的效果。方法全麻下择期行骨科手术病人40例,ASAⅠ～Ⅲ级,分为Ⅰ组(＜65岁)和Ⅱ组(≥65岁),每组20例。入室后(基础值,T_1)静脉输注乳酸钠林格氏液5 ml／kg,效应室靶浓度TCI(T_2)瑞芬太尼从1．0ng／ml渐升至4．0ng／ml后启动异丙酚TCI,从1．0μg／ml血浆靶浓度渐升至4．0μg／ml(T_3),气管插管后即刻(T_4)、切皮前3 min瑞芬太尼和异丙酚靶浓度分别调整为3．0ng／ml、3．0μg／ml。记录平均动脉压(MAP)、心率(HR)、听觉诱发电位指数(AAI)、双频谱指数(BIS),不良反应发生率、辅助药物使用次数、苏醒指标、拔除气管导管后即刻(T_6)及回病房后即刻视觉模拟疼痛评分(VAS)等。结果与Ⅰ组比较,Ⅱ组T_(2,3)时BIS降低,T_(4,5)时MAP、HR降低,心动过缓发生率、麻黄碱、阿托品使用率升高(P＜0．05),不良反应发生率差异无统计学意义。LOC时Ⅰ组和Ⅱ组异丙酚血浆靶浓度分别为2．5±0．7、(1．2±0．5)μg／ml,瑞芬太尼效应室靶浓度Ⅰ组和Ⅱ组分别为3．5±0．4、(3．3±0．4)ng／ml(P＞0．05),异丙酚4μg／ml开始至LOC的时间两组分别为130±60、(82±29)s(P＜0．01),BIS分别为52±11、46±12,AAI为40±25、30±7。Ⅰ组停药至自主呼吸、指令反应恢复时间及拔管、离室时间均早于Ⅱ组(P＜0．05)。回病房后即刻VAS评分Ⅱ组低于Ⅰ组(P＜0．05)。结论瑞芬太尼复合异丙酚TCI全凭静脉麻醉可提供老年病人骨科手术满意的麻醉效应,但需密切观察血液动力学变化。     

听觉诱发电位指数、脑电双频指数及心血管反应评估"过浅麻醉"的价值

目的通过研究丙泊酚诱导过程中,听觉诱发电位指数(AAI)、脑电双频指数(BIS)及心血管反应与插管体动的关系,探讨上述监测手段是否能够反映“过浅麻醉”。方法35例ASAⅠ~Ⅱ级妇科择期手术患者,以丙泊酚进行诱导,患者入睡后,用压力袖带隔离一侧前臂,静注维库溴铵0·1mg/kg。当丙泊酚靶控输注(TCI)达到设定血浆靶浓度(3·5μg/ml)后行气管内插管。记录隔离侧手臂运动(体动)情况,并以是否发生体动反应为准将患者分为体动组与非体动组。记录患者诱导前、插管前的SBP、DBP、HR、BIS、AAI及插管后2min内上述指标的最大值。结果体动组AAI插管后明显高于插管前(P<0·01),而非体动组插管前、后的差异无显著意义;两组患者BIS插管前、后组内及组间的差异均无显著意义;插管引起的DBP、SBP增高体动组明显大于非体动组(P<0·01),但HR变化两组相似。结论BIS仅是衡量睡眠深度的指标,AAI及BP反映“过浅麻醉”,反映机体对伤害性刺激的反应较BIS敏感。     

腰-硬联合麻醉患者异丙酚不同镇静深度下半数有效的浓度、脑电双频指数和听觉诱发电位指数

目的测定腰-硬联合麻醉期间异丙酚靶控输注清醒镇静时患者不同镇静深度的半数有效浓度(EC50)、半数有效BIS(BIS50)和半数有效AAI(AAI50)。方法择期腰-硬联合麻醉下行下腹部或下肢手术患者45例,ASAⅠ级。腰麻阻滞完善后,异丙酚靶控输注清醒镇静,以患者OAA/S评分为镇静指标,采用二项Logistic回归方法计算不同镇静深度(OAA／S评分)的EC50、BIS50和AAI50。结果患者OAA/S4分时EC50为0.6μg／ml、BIS50为85和AAI50为72,OAA/S3分时EC50为1.0μg/ml、BIS50为75和AAI50为59,OAA／S2分时EC50为1.3μg/ml、BIS50为67和AAI50为39,OAA/S1分时EC50为1.6μg／ml、BIS50为61和从AAI50为30,OAA／S0分时EC50为2.5μg／ml、BIS50为41和.AAI50为12。结论EC50、BIS50和AAI50对患者腰-硬联合麻醉期间清醒镇静有重要的临床指导价值。     

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。     

脑电双频指数用于开颅术后患者意识障碍预测

目的探讨开颅术后早期脑电双频指数(BIS)监测对患者远期意识状态预测的准确性,指导护士早期判断患者意识状态。方法对63例开颅术后延迟苏醒拔管患者,记录术后6 h内每小时BIS监测值(BISmax)、道格拉斯昏迷量表中的语言或疼痛刺激体动反应评分(GCS-M)及术后24 h意识状态。根据患者术后24 h是否清醒分组,计算两组BISmax、GCS-M及BISmax对术后24h意识障碍的预测概率(PK)。结果术后24 h清醒患者57例,未清醒6例;清醒者GCS-M评分均为6分,术后6 h内BISmax预测术后24 h意识障碍的PK值为0.69~0.86。结论监测BIS可作为开颅术后患者意识状态的辅助预测方法。     

脑电双频谱指数反馈调控异丙酚靶控输注静脉麻醉

目的 评价BIS作为异丙酚靶控输注的反馈控制变量在腹腔镜胆囊切除术麻醉中的可行性。方法 40例行择期腹腔镜手术的病人随机分为两组，反馈靶控输注组和靶控输注组，每组20人。BIS作为反馈控制变量设定在50。诱导前3min一次性静注芬太尼3μg/kg，异丙酚的血浆靶浓度设定为3μg/ml，诱导及维持期间保持不变。记录并比较两组间的实时BIS值、术中收缩压和舒张压的最高值和最低值、附加药物剂量、呼唤睁眼反应恢复和定向力恢复时间、术中知晓情况和异丙酚的单位标准化使用剂量。结果 反馈组的异丙酚总剂量低于靶控组（P＜0．01），单位标准化剂量亦较低（P＜0．01），血液动力学相对稳定，所用升压药少（P＜0．01），停药药呼唤反应恢复时间较短（P＜0．05），但定向力恢复时间两组间无统计学差异（P＞0．05）。术中BIS的最高值、最低值及清醒值、定向力恢复时的数值，两组间无统计学差异（P＞0．05）。芬太尼均可以使反馈输注组BIS值和靶控输注组BIS值显著下降（P＜0．01）。结论 BIS作为异丙酚靶控输注麻醉的反馈控制变量是可行的，具有这种特性的输注系统能够满足腹腔镜胆囊切除手术的麻醉要求，具有异丙酚用药量少、苏醒快、术中血压比较稳定的优点，使得麻醉深度的调控更加精确。由于不同药物对BIS的影响不同，BIS作为麻醉深度监测指标仅对某些药物是特异的。     

高龄病人异丙酚分步TCI时效应室浓度及BIS的变化

目的 研究高龄病人异丙酚分步靶控输注(TCI)时效应室浓度变化的规律及其相应镇静程度和双频指数(BIS)的变化。方法10例年龄67～77岁病人,进行异丙酚分步TCI,靶浓度(Ct)由1μg/ml,分6步渐增加至4μg/ml。观察效应室浓度(Ce)、BIS和镇静警觉评分(OAA/S),并于Ct分别为1、2、3和4μg/ml时取桡动脉血测异丙酚浓度(Cb)。结果①Ce随Ct增加而增加,但较Ct明显滞后,Ce达到4μg/ml较Ct滞后时间为(14.4±0.5)min。②Cb均高于Ct。PE、MDPE和MDAPE分别为16.3％,9.7％和11.2％。③BIS与Ct和Ce均呈显著负相关(r=-0.878和-0.888,P<0.01)。OAA/S与BIS呈显著正相关(r=0.913,P<0.01),与Ct、Ce均呈显著负相关(r=-0.876和-0.893,P<0.01)。④意识和痛刺激反应消失时BIS值分别为64.6±10.6和43.6±8.1,Ce分别为(1.67±0.49)μg/ml和(2.78±0.46)μg/ml。结论 高龄病人 Ce变化较Ct明显滞后,高龄病人BIS监测可很好反映异丙酚麻醉的深度。     

兔异丙酚靶控输注的药代动力学

目的测定兔靶控输注(TCI)异丙酚药代动力学参数及引起不同麻醉深度所需的异丙酚血浆靶浓度。方法日本大耳兔20只,耳缘静脉注射10 mg·kg~(-1)异丙酚,抽取静脉注射后1、2、5、8、10、15、20、30、45、60 min动脉血各2 ml,通过高效液相色谱法测定异丙酚血药浓度,应用3P87药代动力学程序分析兔异丙酚药代动力学房室模型结构；随后将药代动力学参数代入TCI控制程序Stelpump中,以咀嚼反射消失作为浅麻醉标志,以夹尾后无体动反应为深麻醉标志,确定达到不同麻醉深度所需的异丙酚血浆靶浓度。结果兔异丙酚药代动力学模型为两室模型,中央室表观分布容积为(0．331±0．007)L·kg~(-1),中央室消除速率常数为(0．263±0．019)min~(-1),室间分布速率常数K_(12)、K_(21)分别为0．083±0．004、(0．060±0．009)min~(-1)。浅麻醉状态及深麻醉状态所需异丙酚血浆靶浓度分别为9．25±0．12、(11．63±0．29)μg·ml~(-1)。结论本研究确定了兔TCI异丙酚的药代动力学参数及维持不同麻醉水平血浆靶浓度。     

Detection of awareness in surgical patients with EEG-based indices--bispectral index and patient state index

Background. Patient state index (PSI) and bispectral index (BIS)are values derived from the EEG, which can measure the hypnoticcomponent of anaesthesia. We measured the ability of PSI andBIS to distinguish consciousness from unconsciousness duringinduction and emergence from anaesthesia and a period of awarenessin surgical patients. Methods. Forty unpremedicated patients were randomized to receive:(1) sevoflurane/remifentanil (     

Comparison of Alaris AEP index and bispectral index during propofol-remifentanil anaesthesia

Background. The Alaris AEP monitor^TM (Alaris, UK, version 1.4)is the first commercially available auditory evoked potential(AEP) monitor designed to estimate the depth of anaesthesia.It generates an ‘Alaris AEP index’ (AAI), whichis a dimensionless number scaled from 100 (awake) to 0. Thisstudy was designed to compare AAI and BIS^TM (Aspect, USA, versionXP) values at different levels of anaesthesia. Methods. Adult female patients were premedicated with diazepam0.15 mg kg^–1 orally on the morning of surgery. Electrodesfor BIS and Alaris AEP monitoring and a headphone to give auditorystimuli were applied as recommended by the manufacturers. Anaesthesiawas induced with remifentanil (0.4 µg kg^–1 min^–1)and a propofol target-controlled infusion (Diprifusor^TM TCI,AstraZeneca, Germany) to obtain a predicted concentration ofinitially 3.5 µg ml^–1. After loss of consciousnessthe patients were given 0.5 mg kg^–1 of atracurium. Aftertracheal intubation, remifentanil was given at 0.2 µgkg^–1 min^–1 and the propofol infusion was adjustedto obtain BIS target values of 30, 40, 50, and 60. AAI and BISvalues were recorded and matched with the predicted propofoleffect-site concentrations. Prediction probability was calculatedfor consciousness vs unconsciousness. Values are mean (SD). Results. Fifty female patients, 53 (15), range 18–78 yr,ASA I or II were studied. Mean values before induction of anaesthesiawere 95 (4), range 99–82 for BIS and 85 (12), range 99–55for AAI. With loss of eyelash reflex both values were significantlyreduced to 64 (13), range 83–39 for BIS (P<0.05) and61 (22), range 99–15 for AAI (P<0.05). The predictionprobability P_K for consciousness vs unconsciousness (i.e. lossof eyelash reflex) was better for BIS (P_K=0.99) than for AAI(P_K=0.79). At a BIS of 30, 40, 50, and 60 the correspondingAAI values were 15 (6), 20 (8), 28 (11), and 40 (16), and thesewere significantly different. Conclusions. During propofol-remifentanil anaesthesia a decreaseof the depth of anaesthesia as indicated by BIS monitoring isaccompanied by corresponding effects shown by the AAI. However,wide variation in the awake values and considerable overlapof AAI values between consciousness and unconsciousness, suggestsfurther improvement of the AAI system is required. Br J Anaesth 2003; 91: 336–40     

Relationship between bispectral index,auditory evoked potential index and effect-site EC50 for propofol at two clinical end-points

Background. Many anaesthetists are deterred from using totali.v. anaesthesia because of uncertainty over the concentrationof propofol required to prevent awareness. We predicted bloodand effect-site concentrations of propofol at two clinical end-points:loss of consciousness and no response to a painful stimulus. Methods. Forty unpremedicated Caucasian patients were anaesthetizedwith i.v. propofol delivered by a Diprifusor target-controlledinfusion (TCI). Bispectral index (BIS) and auditory evoked potentialindex (AEPex) were measured and blood and effect-site propofolconcentrations were predicted. Logistic regression was usedto estimate population values for predicted blood and effect-sitepropofol concentrations at the clinical end-points and to correlatethese with BIS and AEPex. Results. The effect-site EC₅₀ at loss of consciousness was 2.8 µm ml^–1with an EC₀₅ and an EC₉₅ of 1.5 and 4.1 µm ml^–1,respectively. The predicted EC₅₀ when there was no responseto a tetanic stimulus was 5.2 µm ml^–1 withan EC₀₅ and an EC₉₅ of 3.1 and 7.2 µm ml^–1,respectively. Conclusions. Unconsciousness and lack of response to a painfulstimulus occur within a defined range of effect-site concentrations,predicted by Diprifusor TCI software. Br J Anaesth 2003; 90: 127–31     

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.     

Comparability of Narcotrend index and bispectral index during propofol anaesthesia

Background. The dimensionless Narcotrend^TM (NCT) index (MonitorTechnik,Germany, version 4.0), from 100 (awake) to 0, is a new indexbased on electroencephalogram pattern recognition. Transferringguidelines for titrating the Bispectral Index^TM (BIS, AspectMedical Systems, USA, version XP) to the NCT index depends ontheir comparability. We compared the relationship between BISand NCT values during propofol anaesthesia. Methods. Eighteen adult patients about to have radical prostatectomywere investigated. An epidural catheter was placed in the lumbarspace and electrodes for BIS and NCT were applied as recommendedby the manufacturers. After i.v. fentanyl 0.1 mg, anaesthesiawas induced with a propofol infusion. After intubation, patientsreceived bupivacaine 0.5% 15 ml via the epidural catheter. Forty-fiveminutes after induction, the propofol concentration was increasedto substantial burst suppression pattern and then decreased.This was done twice in each patient, and BIS and Narcotrendvalues were recorded at intervals of 5 s. The efficacy of NCTand BIS in predicting consciousness vs unconsciousness was evaluatedusing the prediction probability (P_K). Results. We collected 38 629 artefact-free data pairs of BISand NCT values from the respective 5-s epochs. Because of artefacts,another 5008 epochs had been excluded from data analysis (3855epochs for the NCT index alone, 245 epochs for the BIS aloneand 908 epochs for both indices). Mean (SD) values in awakepatients were 94 (6) for Narcotrend and 91 (8) for BIS. Withloss of the eyelash reflex, both values were significantly reduced,to 72 (9) for NCT (P<0.001) and to 77 (11) for the BIS index(P<0.001). The P_K value for loss of eyelash reflex was similarfor BIS (0.95) and NCT (0.93). Decreasing BIS values coincidedwith decreasing NCT values. A sigmoid model [NCT index=52.8+26.8/(1+exp(–(BIS–78.3)/4.8))^0.4;r=0.52] described the correlation between BIS and NCT indexin a BIS range between 100 and 50. For BIS values lower than50, a second sigmoid model with a correlation of r=0.83 wasapplied [NCT index=6.6+45.3/(1+exp(–(BIS–29.8)/2.4))^0.6 r=0.83]. The relationship between burst suppression ratio(BSR) and NCT index was best described by the following sigmoidmodel: NCT index=265/(1+exp((–BSR+108)/–49); r=0.73. Conclusions. We found a sufficient correlation between BIS andNCT index, but deviations from the line of identity in someranges require attention. Therefore, a simple 1:1 transfer fromBIS to NCT values is not adequate. Our results might serve asa blueprint for the rational translation of BIS into NCT values.     

Comparison of ocular microtremor and bispectral index during sevoflurane anaesthesia

Background. A practical and reliable monitor of depth of anaesthesiawould be a major advance on current clinical practice. Noneof the present monitors is both simple to use and accurate.Ocular microtremor (OMT) is a physiological tremor that is suppressedby propofol in a dose-dependent manner. We studied OMT duringpropofol induction and nitrous oxide– oxygen–sevofluranemaintenance of anaesthesia in 30 patients, and compared OMTwith the bispectral index (BIS) as a predictor of response toverbal command. Methods. OMT was measured using the closed-eye piezoelectricstrain-gauge technique. OMT and BIS were measured at specifictimes during the anaesthetic, including at loss of consciousness,at end-tidal sevoflurane 1 and 2%, and at emergence. Results. OMT decreased significantly after induction, did notdecrease as end-tidal sevoflurane was increased from 1 to 2%,and increased at emergence in all patients. By logistic regression,OMT was more sensitive and specific than BIS in distinguishingthe awake from the anaesthetized state (OMT, 84.9 and 93.1%respectively; BIS, 75.7 and 69.0%). Conclusions. OMT is suppressed by sevoflurane and accuratelypredicts response to verbal command. OMT may be a useful monitorof depth of hypnosis. Br J Anaesth 2002; 89; 551–5     

Detection of cerebral hypoperfusion with bispectral index during paediatric cardiac surgery

Background. The bispectral index (BIS) may indicate changesin cerebral activity when the cerebral circulation is affectedby acute hypotension. Methods. We measured BIS and cerebral haemoglobin saturation(Sr_O2) by near-infrared spectroscopy in 10 children undergoingcardiac surgery. Results. We noted 14 episodes of simultaneous decreases in Sr_O2and BIS during acute hypotension in five children. An acutedecrease in BIS, which coincided with a decrease in Sr_O2 suggestinga reduction in cerebral blood flow, was associated with acuteslowing of the raw EEG waveforms. Conclusions. Our findings suggest that an acute decrease inBIS during acute hypotension indicates cerebral hypoperfusion,and that cerebral hypoperfusion caused by hypotension may occurfrequently during paediatric cardiac surgery. Br J Anaesth 2003; 90: 694–8     

Bispectral index monitoring: comparison of two types of electrode

Bis-monitoring is a new method of monitoring anaesthetic depth. Bis-monitoring is easy to perform, but the Bis-monitor and the original, disposable electrodes are expensive. The aim of this study was to determine whether the original Zipprep electrodes could be replaced by the much cheaper electrocardiogram electrodes. We compared bispectral index measurements, conducted using both types of electrode in the same patients before anaesthesia, and during light and deep anaesthesia, in patients randomly allocated to receive either sevoflurane or propofol anaesthesia. We found very good agreement between the measurements from the two different sets of electrodes. The impedance in the electrocardiogram electrodes was higher than in the Zipprep electrodes, but this did not affect the bispectral index. No other problems with either type of electrode were detected. It is concluded that Zipprep electrodes can be replaced by electrocardiogram electrodes in normal clinical practice.     

Correlation of the A-Line ARX index with acoustically evoked potential amplitude

Background. Automated indices derived from mid-latency auditoryevoked potentials (MLAEP) have been proposed for monitoringthe state of anaesthesia. The A-Line^TM ARX index (AAI) has beenimplemented in the A-Line^TM monitor (Danmeter, V1.4). Severalstudies have reported variable and, in awake patients, sometimessurprisingly low AAI values. The purpose of this study was toreproduce these findings under steady-state conditions and toinvestigate their causes. Methods. Ten awake unmedicated volunteers were studied understeady-state conditions. For each subject, the raw EEG and theAAI were recorded with an A-Line^TM monitor (V1.4) during threeseparate sessions of 45.0 (1.6) min duration each. MATLAB^TM(Mathworks) routines were used to derive MLAEP responses fromEEG data and to calculate maximal MLAEP amplitudes. Results. The AAI values ranged from 15 to 99, while 11.4% fellbelow levels which, according to the manufacturer, indicatean anaesthetic depth suitable for surgery. Inter-individualand intra-individual variation was observed despite stable recordingconditions. The amplitudes of the MLAEP varied from 0.8 to 42.0µV. The MLAEP amplitude exceeded 2 µV in 75.3% ofreadings. The Spearman's rank correlation coefficient betweenthe MLAEP amplitude and the AAI value was r=0.89 (P<0.0001). Conclusions. The version of the A-Line^TM monitor used in thisstudy does not exclude contaminated MLAEP signals. Previouspublications involving this version of the A-Line^TM monitor(as opposed to the newer A-Line/2^TM monitor series) should bereassessed in the light of these findings. Before exclusivelyMLAEP-based monitors can be evaluated as suitable monitors ofdepth of anaesthesia, it is essential to ensure that inbuiltvalidity tests eliminate contaminated MLAEP signals. Presented in part at the annual meeting of the European Societyof Anaesthesiologists, Lisbon, Portugal, June 5–7, 2004.     

Surgical stress index reflects surgical stress in gynaecological laparoscopic day-case surgery

Background: Monitoring of analgesia remains a challenge during general anaesthesia.The surgical stress index (SSI) is derived from the photoplethysmographicwaveform amplitude and the heart beat-to-beat interval. We evaluatedthe ability of SSI to measure surgical stress in patients undergoinggynaecological laparoscopy. Our hypothesis was that while keepingState Entropy^TM (SE) at a predetermined level, SSI would behigher in patients receiving a ß-blocking agent (esmolol)than in those receiving an opioid (remifentanil) during laparoscopy. Methods: Thirty women undergoing gynaecological laparoscopy were assignedrandomly to receive esmolol (n = 15) or remifentanil (n = 15).Anaesthesia was induced with propofol and fentanyl and maintainedwith desflurane and nitrous oxide 50% in oxygen to keep SE at50(5). The infusion of esmolol or remifentanil was started beforelaparoscopy and adjusted to keep the systolic blood pressureat –20 to +10% from the preoperative value. Results: During the fentanyl phase, before surgery, both groups behavedsimilarly, with an increase in SSI after intubation. In thepatients receiving esmolol, the SSI reacted to the initial incision(P < 0.05), and remained high after trocar insertion (P <0.05). In patients receiving remifentanil, it did not reactto the initial incision, but increased after trocar insertion(P < 0.05), and it remained lower both after incision (P< 0.05) and after trocar insertion (P < 0.05). Conclusion: SSI was higher in patients receiving esmolol. The index seemsto reflect the level of surgical stress and may help guide theuse of opioids during general anaesthesia.