地氟醚和七氟醚对术中运动诱发电位监测的影响

目的比较地氟醚和七氟醚对术中运动诱发电位(motor evoked potentials,MEPs)监测的影响。方法选择ASAⅠ或Ⅱ级,择期神经外科手术术中行MEPs监测的患者36例,随机均分为两组:地氟醚组(F组)和七氟醚组(S组)。术中监测血流动力学、BIS、MEPs的波幅和潜伏期、肌松(TOF值)、体温。术中保证肌松药作用消失,维持血流动力学平稳,BIS 40~60,体温36~37℃,调节吸入麻醉药浓度,使其呼气末浓度达到0.7、0.8、0.9和1.0 MAC,每一浓度维持10min,测每一浓度下四肢的运动诱发电位,记录其潜伏期和波幅,比较两组各肢体在不同浓度下MEPs的潜伏期和波幅的变化。结果与前一MAC比较,随MAC值增加,左上、下肢体和右上、下肢体的两组MEPs潜伏期明显延长,MEPs波幅明显降低(P0.05)。在0.7、0.8 MAC时,左下肢和右下肢F组的MEPs潜伏期明显长于,MEPs波幅明显低于S组(P0.05);在0.9、1.0 MAC时,左上、下肢体和右上、下肢体的F组的MEPs潜伏期明显长于,MEPs波幅明显低于S组(P0.05)。与前一MAC比较,随MAC值增加,左上、下肢体和右上、下肢体的两组MEPs潜伏期与0.7 MAC时MEPs潜伏期的百分率明显升高,MEPs波幅与0.7 MAC时MEPs波幅的百分率明显减低(P0.05)。结论地氟醚和七氟醚对MEPs均有抑制作用,随着药物浓度的增加,抑制作用逐渐增强,且在同一MAC条件下,似乎地氟醚的抑制作用强于七氟醚。     

七氟醚、异氟醚不同呼气末浓度对熵和脑电双频指数的影响

目的 观察不同呼气末浓度的七氟醚和异氟醚对熵、脑电双频指数(BIS)及血流动力学的影响.方法 40例ASA Ⅰ或Ⅱ级全麻手术患者随机均分为七氟醚组(Ⅰ组)和异氟醚组(Ⅱ组).麻醉诱导用丙泊酚1 mg/kg,1 min后吸入七氟醚或异氟醚;维持反应熵(RE)、状态熵(SE)、BIS45～55,6 min后置入喉罩.调节吸入浓度使两组患者呼气末浓度分别为0.4、0.6、0.8、1.0和1.3MAC时各维持10 min,记录RE、SE、BIS、HR和MAP.结果 两组患者不同呼气末浓度七氟醚和异氟醚RE、SE、BIS随浓度增加而逐渐下降(P<0.05),HR逐渐减慢、MAP逐渐降低(P<0.05).两组间各指标差异均无统计学意义.RE、SE、BIS间直线相关性随呼气末浓度增大相关系数有增加趋势.结论 熵和BIS均能有效监测七氟醚、异氟醚麻醉深度.     

体感诱发电位、数量化脑电图与异氟醚吸入浓度的关系

目的 探讨短潜伏期体感诱发电位和数量化脑电图监测异氟醚吸入麻醉深度的可行性.方法 选择全麻患者30例,麻醉诱导后吸入异氟醚,依次增加呼气末异氟醚浓度为0.4、0.7、1.0、1.3和1.6 MAC,记录麻醉过程中MAP、HR、数量化脑电图(BIS、95%SEF和MF)和体感诱发电位(LP15、LN20、LN11和CCT),计算各监测指标与异氟醚吸入浓度的相关性.结果 患者HR、LN11与呼气末异氟醚浓度变化无直线相关关系;MAP、BIS、95%SEF和MF与呼气末异氟醚浓度变化呈负相关关系(P＜0.05),而LP15、LN20和CCT与呼气末异氟醚浓度变化呈正相关关系(P＜0.05).结论 BIS、95%SEF、MF、LN20和CCT是监测异氟醚吸入麻醉深度的较好指标.     

BIS用于指导小儿七氟醚麻醉用药的临床观察

目的 探讨BIS指导小儿七氟醚麻醉的临床意义.方法 48例1～12岁、行泌尿外科手术的小儿随机均分为两组.BIS组依据BIS值调整七氟醚吸入浓度(目标BIS术中保持在40～60,术末15 min保持60～75);对照组根据临床经验调节七氟醚吸人浓度.记录术中和术末平均BIS值、呼气末七氟醚浓度及MAC值.同时记录HR、MAP、苏醒时间、气管拔管时间、离开PACU时间.计算七氟醚用量.结果 BIS组术中及术末的平均呼气末七氟醚浓度显著小于对照组(P<0.01),BIS值显著大于对照组(P<0.01).BIS组苏醒时间、拔管时间、离开PACU时间均显著短于对照组(P<0.01).结论 小儿七氟醚麻醉中监测BIS能减少七氟醚用量和加快苏醒.     

听觉诱发电位指数监测患者吸入异氟醚麻醉深度的准确性

目的 评价听觉诱发电位指数(AAI)监测患者异氟醚吸入麻醉深度的准确性.方法 30例择期全麻手术患者,ASA Ⅰ或Ⅱ级.麻醉诱导气管插管后15 min开始以3 L/min氧流量(高流量)洗人,12 min后调整为0.5 L/min氧流量(低流量)维持,调节异氟醚挥发罐刻度,使异氟醚呼气末浓度依次为0.8 MAC、1.0 MAC和1.3 MAC,每个浓度维持20 min,分别于诱导前(基础状态)、诱导后即刻、吸人异氟醚前即刻、高流量洗入3 min、6 min、9 min、12 min及低流量维持期异氟醚呼气末浓度分别为0.8 MAC、1.0 MAC、1.3 MAC时监测平均动脉压、心率和AAI.结果 与吸入异氟醚前即刻比较,高流量洗人期AAI降低,且高流量洗人期AAI逐渐降低(P＜0.05).低流量维持期异氟醚呼气末浓度为0.8 MAC、1.0 MAC和1.3 MAC时,随浓度的增加AAI逐渐降低(P＜0.05),在此范围内AAI与异氟醚呼气末浓度的相关系数为-0.896(P＜0.01).结论 AAI可用于监测患者异氟醚吸入麻醉的深度.     

静吸复合麻醉下七氟醚与异氟醚对颅内压的影响

目的:在颅内顺应性正常神经外科病人,观察1.0 MAC七氟醚与异氟醚对颅内压的影响。方法:垂体瘤或颅咽管瘤手术病人16例,随机分为两组:A组为咪唑安定 芬太尼 1.0 MAC异氟醚;B组为咪唑安定 芬太尼 1.0 MAC七氟醚。选择L_(3～4)行蛛网膜下腔穿刺。麻醉诱导采用芬太尼-咪唑安定-阿曲库铵。插管后维持稳定30分开始吸入七氟醚(或异氟醚)。分别于麻醉前、吸入麻醉药前、达预定呼气末浓度30分内观察监测指标。结果:1.0 MAC七氟醚和异氟醚均可显著降低脑灌注压,异氟醚作用较强。吸入1.0 MAC七氟醚后颅内压首先呈显著性下降,15分后回复至基础水平。吸入1.0 MAC异氟醚后颅内压无显著性变化。结论:在颅内顺应性正常患者,1.0 MAC七氟醚和异氟醚均可安全用于神经外科麻醉。     

幼儿脑电双频指数与七氟醚呼气末浓度的关系

目的 探讨幼儿患者脑电双频指数(BIS)与七氟醚呼气末浓度(CETSev)的关系.方法 择期全麻下行腹部手术的患儿120例,ASA Ⅰ或Ⅱ级,年龄1～3岁,随机均分为四组:Ⅰ组,CETSev为0.4 MAC;Ⅱ组,CETSev为0.7 MAC;Ⅲ组,CETSev为1.0 MAC;Ⅳ组,CETSev为1.3MAC.8%七氟醚面罩吸入诱导,氧流量5 L/min,待患儿意识消失后调整氧流量至2 L/min,并逐步凋节七氟醚吸入浓度,按照分组使CETSev达到并维持于相应的浓度,每一浓度均维持15 min,视为稳态CETSev.分别记录所有患儿入室(T0)、达稳态CETSev(T1)时的BIS、MAP及HR.结果 当CETSev由0.4～1.3 MAC递增时,四组患儿MAP和HR差异无统计学意义,但BIS逐渐下降(P＜0.05),BIS、MAP及HR与CETSev相关系数分别为-0.857、-0.379和0(P＜0.05).结论 无伤害性刺激时,BIS与CETScv呈一定剂量的负相关,相关性较好,BIS可用于监测七氟醚麻醉下的镇静程度.     

低浓度七氟醚与异氟醚吸入麻醉对小儿血流动力学的影响

目的 研究低流量七氟醚与异氟醚吸入麻醉对小儿血流动力学的影响.方法 40例1～5岁小儿随机分为七氟醚组(S组)和异氟醚组(I组),每组20例.分别测量呼气末麻醉药浓度为0MAC(T0)、0.5MAC(T1)、1.0MAC(T2)和1.5MAC(T3)稳定5 min后的每搏指数(SI)、心脏指数(CI)、外周血管阻力(SVR)、HR及MAP.结果 与T0时比较,T1时两组MAP和SVR均有降低(P<0.05),其他指标均无明显变化.T2时,SVR和MAP进一步降低,HR略增快和SI略升高,但两组间差异无统计学意义,S组Cl值显著高于Ⅰ组(P<0.05).T3时,S组的HR显著快于Ⅰ组,而SI下降与T0近似;SVR和MAP两组无进一步降低.结论 低浓度七氟醚和异氟醚麻醉对小儿心肌无明显抑制,仅降低MAP和SVR,七氟醚增快HR作用大于异氟醚.     

不同靶浓度异丙酚对七氟醚MAC的影响

目的 评价不同靶浓度异丙酚对七氟醚MAC的影响.方法 择期全麻下行腹部手术的病人,年龄20～50岁,ASA Ⅰ或Ⅱ级,随机分为5组,P0组、P2组、P3组、P4组和P4组均吸入8%七氟醚麻醉诱导,意识消失后静脉注射琥珀胆碱1 mg/kg和瑞芬太尼1 μg/kg.气管插管后行机械通气,P1组、P2组、P3组和P4组靶控输注异丙酚,血浆靶浓度分别为1、2、3、4 tμg/ml,P0组、P1组、P2组、P3组和P4组第1例病人七氟醚呼气末浓度分别为3.0%、2.2%、2.0%、1.8%和1.5%,当七氟醚呼气末浓度平衡15 min以上且神经肌肉功能恢复后开始切皮,根据是否发生切皮反应,采用up-down方法确定下一例病人的七氟醚呼气末浓度,每组出现6个交叉点后终止研究,以6个交叉点病人七氟醚呼气末浓度的均数为MAC.七氟醚MAC与异丙酚血浆靶浓度间分别进行直线回归和等级相关分析.结果 Pn组～P4组七氟醚MAC分别为2.17 4-0.11%、1.90%±0.10%、1.47%±0.19%、1.37%±0.13%和1.00%±0.10%;与P0组相比,P1组～P4组七氟醚MAC均降低,且呈浓度依赖性(P＜0.05).七氟醚MAC(Y)与异丙酚血浆靶浓度(X)间的直线回归方程为Y=2.17-0.212 X,相关系数为-0.946 9(P＜0.05).结论 异丙酚血浆靶浓度1～4 μg/ml可使七氟醚MAC分别降低12%、32%、37%和54%,两者以相加作用的方式抑制切皮反应.     

硬膜外利多卡因对异氟醚和地氟醚MAC的影响

目的 本研究以BIS>50作为指标来确定异氟醚和地氟醚的ED50值(MACBIS50),观察硬膜外利多卡因对异氟醚和地氟醚达到满意麻醉深度时用药量的影响。方法 48例患者随机分为两组:异氟醚组和地氟醚组,每组又随机分全麻复合硬膜外组和单纯全麻组(每组12例)。患者术前阿托品肌肉注射,全麻复合硬膜外组给予1.6％利多卡因10ml。全麻诱导采用咪达唑仑、芬太尼、异丙酚和维库溴铵,诱导插管后吸入异氟醚和地氟醚,待呼气末浓度(ET％)达到预定值并且稳定10 min后,记录相应的BIS值。采用上下波动法分别计算异氟醚和地氟醚MACBIS50,BIS值和呼气末浓度进行直线回归分析。结果MACBIS50全麻复合硬膜外组(异氟醚组0.77％、地氟醚组3.87％)和单纯全麻组(异氟醚组1.16％、地氟醚组5.18％)比较显著降低(P<0.01)。四组BIS和ET％均呈直线相关。结论硬膜外利多卡因可显著降低异氟醚(34％)和地氟醚(53％)维持足够麻醉深度的呼气末浓度,并保持BIS值和呼气末浓度的直线相关性。     

The bispectral index system in pediatrics--is it related to the end-tidal concentration of inhalation anesthetics?

BACKGROUND AND GOAL OF STUDY: Bispectral Index (BIS) has been used in adults to measure depth of anesthesia using various protocols. Though less investigated in children, there is growing evidence that bispectral index seems adequately calibrated for monitoring the depth of isoflurane and sevoflurane anesthesia in pediatric patients. A range of BIS scores (40-60) has been seen to be an indicator for an acceptable level of hypnosis and anesthesia. Davidson and Czarnecki have reported that, at an end-tidal concentration of 1 MAC, the BIS for halothane was significantly greater than isoflurane (56.5 +/- 8.1 vs. 35.9 +/- 8.5). The explanation given is the fact that the volume concentration of the MAC value is inversely related to the BIS value. Accordingly, it is expected that the BIS value at 1 MAC of desflurane must be less than halothane and isoflurane. MATERIALS AND METHODS: This is a clinical cross-over, prospective, randomized double blinded study. 90 pediatric patients scheduled for below umbilical surgery, under general and caudal analgesia, were allocated into 4 study groups. The BIS values at a relatively equipotent doses of the previously mentioned agents were compared with each other in the same group and between other groups. RESULTS: At a relatively equipotent doses, the mean BIS value for halothane {60.4 +/- 5.6} was significantly higher than isoflurane {45.5 +/- 9.2} and desflurane {38.5 +/- 9.2} P<0.001). Equivalent end-tidal doses of different inhalational anesthetics do not necessarily have the same effects on cortical and sub-cortical functions and consequently on EEG. Conclusion: The use of a relatively equipotent end-tidal concentration of different inhalational agents may result in different BIS values.     

Relationship between minimum alveolar concentration and electroencephalographic bispectral index as well as spectral edge frequency 95 during isoflurane/epidural or sevoflurane/epidural anesthesia]

To investigate the relationship between minimum alveolar concentration (MAC) and electroencephalographic variables, we measured the bispectral index (BIS) and the spectral edge frequency 95 (SEF 95) in 17 patients undergoing elective surgery during isoflurane/epidural (n = 8) or sevoflurane/epidural (n = 9) anesthesia. Patients received 2.0 MAC end-tidal concentrations of isoflurane or sevoflurane, and the BIS and the SEF 95 were recorded after 15 min of an unchanged end-tidal concentration. The concentration of the inhalational agent was decreased to 1.2 MAC, and measurements were repeated again. During isoflurane anesthesia, the BIS increased significantly (3.6 +/- 3.9 at 2.0 MAC, 43.5 +/- 9.2 at 1.2 MAC [mean +/- SD]). In contrast, the BIS did not change significantly during sevoflurane anesthesia (35.3 +/- 8.4 at 2.0 MAC, 42.8 +/- 6.1 at 1.2 MAC). There were significant differences in the BIS and the SEF 95 at 2.0 MAC between isoflurane and sevoflurane groups. In contrast, the BIS and the SEF 95 showed no difference at 1.2 MAC between the groups. These findings suggest that different inhalational anesthetics may have different effects on the BIS and the SEF 95.     

The effect of desflurane and sevoflurane on cerebral oximetry under steady-state conditions

We studied the effect of sevoflurane and desflurane on regional cerebral oxygenation (rSO2). Twenty-two patients undergoing abdominal hysterectomy received sevoflurane and desflurane for 15 min each and 30 min apart under steady-state conditions in a randomized, crossover manner to maintain a bispectral index (BIS) of 40-50. In another 22 patients undergoing the same anesthesia and surgery BIS was maintained at 20-30. During the 15-min administration of each anesthetic at steady-state conditions rSO2, BIS, inspired and end-tidal anesthetic concentrations, end-tidal CO2, Spo2, systolic and diastolic blood pressures, and heart rate were recorded every 3 min. The rSO2 did not differ between sevoflurane and desflurane when BIS values were maintained between 40-50 or 20-30. The MAC(BIS) values required to maintain BIS at 40-50 and at 20-30 were 1.0 versus 1.2 (P = 0.004) and 1.6 versus 1.8 (P < 0.001) for desflurane and sevoflurane respectively. Higher rSO2 values were obtained by 1.6 MAC (71 +/- 13) than by 1 MAC of desflurane (66 +/- 10; P < 0.001) and by 1.8 MAC (72 +/- 11) than by 1.2 MAC of sevoflurane (66 +/- 13; P < 0.001). In conclusion, equipotent concentrations of desflurane or sevoflurane in terms of BIS are associated with similar rSO2 values, but larger anesthetic concentrations of both anesthetics increased the rSO2 values.     

异氟醚和七氟醚对非体外循环冠状动脉旁路移植术患者心肌保护作用的比较

目的 比较异氟醚和七氟醚对非体外循环冠状动脉旁路移植术患者的心肌保护作用.方法 择期行非体外循环冠状动脉旁路移植术患者40例,性别不限,年龄40～55岁,体重55～94 kg,ASA分级Ⅱ或Ⅲ级,NYHA分级Ⅱ或Ⅲ级.采用随机数字表法,将患者随机分为2组(n=20):异氟醚组(Ⅰ组)和七氟醚组(S组).麻醉诱导:静脉注射咪达唑仑0.08 mg/kg、舒芬太尼2μg/kg和维库溴铵0.1 mg/kg,气管插管后行机械通气.麻醉维持:Ⅰ组吸入异氟醚,初始呼气末浓度1.2%;S组吸入七氟醚,初始呼气末浓度1.7%;两组静脉输注舒芬太尼0.04μg·kg-1·min-1和维库溴铵0.8μg·kg-1·min-1.通过调节异氟醚或七氟醚的呼气末浓度,维持BIS值40～50.分别于切皮前即刻、术毕、术后2和4 h时,采集中心静脉血样,测定血浆MB型肌酸激酶同工酶(CK-MB)的活性和心肌肌钙蛋白Ⅰ(cTnI)的浓度.记录术中心血管不良事件的发生情况.结果 与Ⅰ组比较,S组术中室性早搏、心动过速、心动过缓、室颤和S-T段抬高＞0.1 mV的发生率升高,术后血浆CK-MB活性和cTnI浓度升高(P＜0.05).结论 非体外循环冠状动脉旁路移植术患者异氟醚的心肌保护作用优于七氟醚.

Abstract：

Objective To compare the myocardial protective effects of isoflurane versus sevoflurane in patients undergoing off-pump coronary artery bypass grafting (OPCABG). Methods Forty ASA Ⅱ or Ⅲ patients (NYHA Ⅱ or Ⅲ ) of both sexes, aged 40-55 yr, weighing 55-94 kg, scheduled for elective OPCABG, were randomly divided into 2 groups ( n = 20 each): isoflurane group ( group Ⅰ) and sevoflurane group ( group S). Anesthesia was induced with midazolam, sufentanil and vecuronium. Patients were tracheal intubated and mechanically ventilated. Anesthesia was maintained with inhalation of isoflurane or sevoflurane and infusion of sufentanil and vecuronium. In group Ⅰ, the initial end-tidal concentration of isoflurane was 1.2%. In group S, the initial end-tidal concentration of sevoflurane was 1.7 %. BIS value was maintained at 40-50 by adjusting the end-tidal concentration of isoflurane or sevoflurane. The central venous blood samples were collected immediately before skin incision, at the end of surgery, 2 and 24 h after surgery for determination of plasma creatine kinase-MB (CK-MB) activity and cardiac troponin Ⅰ (cTnI) concentration. The adverse cardiovascular events were recorded. Results The incidences of ventricular premature beat, tachycardia, bradycardia, ventricular fibrillation and S-T segment elevation ( ＞0.1 mV) during surgery and the plasma CK-MB activity and cTnI concentration after surgery were significantly higher in group S than in group Ⅰ ( P ＜ 0.05). Conclusion Isoflurane has better myocardial protective effect than sevoflurane in patients undergoing OPCABG.     

末梢灌注指数监测地氟醚诱发患者交感神经兴奋的评价

目的 评价末梢灌注指数(TPI)监测地氟醚诱发的患者交感神经兴奋作用.方法 择期全麻患者48例,年龄25～60岁,ASA Ⅰ或Ⅱ级,随机分为3组(n=16):七氟醚组(Ⅰ组)、地氟醚组(Ⅱ组)和地氟醚+异丙酚组(Ⅲ组).气管插管后Ⅰ组和Ⅱ组地氟醚或七氟醚呼气末浓度依次快速达到0.5 MAC、1.0 MAC和1.5 MAC,并在每个水平维持5 min.Ⅲ组在气管插管后靶控输注异丙酚.血浆靶浓度至1μg/ml,地氟醚呼气末浓度依次快速达到0.5 MAC、1.0 MAC,并在每个水平维持5 min.分别在给予咪达唑仑后5 min(T0)、麻醉诱导后3 min(T1)、插管后即刻(T2)、呼气末浓度达到0.5 MAC(T3)、0.5 MAC后5 min(T4)、1.0 MAC(T5)、1.0MAC后5min(T6)、1.5MAC(T7)、1.5MAC后5min(T8)时记录心率(HR)、平均动脉压(MAP)、TPI、脑电双频谱指数,并在T0、T1、T2、T5、T7时测定血浆肾素活性和血管紧张素Ⅱ水平.结果 与T4时比较,Ⅱ组T5时,IPI降低(P<0.05);与T7时比较,Ⅱ组T4～6、T8时HR、MAP降低,T3～6、T8时TPI降低(P<0.05);与Ⅰ组比较,Ⅱ组T7时HR、MAP升高,TPI降低(P<0.05);Ⅱ组T5和T7时TPI出现变化最大值的时间短于HR、MAP;ATPI与△HR、AMAP呈负相关(r=-0.593,P<0.05;r=-0.591,P<0.05);与Ⅰ组比较,Ⅱ组血浆肾素活性和AT-Ⅱ浓度升高(P<0.05).结论 TPI可灵敏地反映地氟醚诱发的患者交感神经兴奋.     

The relationship between end-tidal isoflurane concentration and electroencephalographic bispectral index during isoflurane/epidural anesthesia

We studied the effects of increases in isoflurane concentration on the bispectral index (BIS) in 16 patients undergoing lower abdominal surgery during isoflurane/epidural anesthesia. In 8 patients, the lungs were ventilated with an air/oxygen mixture (inspired oxygen fraction 0.33) [N(-) group], and in another 8 patients, the lungs were ventilated with 66% nitrous oxide in oxygen [N(+) group]. During surgery, patients received 1.0 MAC (1.15%) end-tidal isoflurane and the BIS was recorded after 10 min of unchanged end-tidal concentration. After this, we increased the end-tidal concentration of isoflurane by 0.2 MAC to 1.8 MAC. At each concentration step, the BIS was recorded again after 10 min of unchanged end-tidal concentration. At isoflurane concentration < 1.4 MAC, the BIS did not change with increasing isoflurane concentration in both groups (BIS values = about 40). In N (-) group, the BIS decreased in all patients at isoflurane concentration > 1.6 MAC. The mean BIS values were 22 (SD 18) at 1.6 MAC and 2(4) at 1.8 MAC, respectively. In N (+) group, the BIS decreased in four patients at isoflurane concentration > 1.6 MAC, and the BIS did not decrease at 1.8 MAC in another four patients. The mean BIS values were 27 (17) at 1.6 MAC and 21(21) at 1.8 MAC. The present data suggest that BIS may not correlate with anesthetic effect of isoflurane at isoflurane concentration > 1.0 MAC.     

吸入麻醉下内隐记忆与脑电双频谱指数的关系

目的 研究相同ＭＡＣ水平的吸入麻醉药对内隐记忆的影响,分析内隐记忆消失的界值。方法 ５４例行择期腹部手术患者,随机分为异氟醚、七氟醚、地氟醚３组（每组１８例）,麻醉采用吸入麻醉复合硬膜外麻醉,每组又依吸入麻醉浓度不同分成３个亚组（每组６例）,吸入麻醉药呼末ＭＡＣ值分别为０．４、０．５、０．６,监测患者入室后、麻醉后、切皮后、术中的双频谱指数（ＢＩＳ）,９５％的谱边缘频率（ＳＥＦ）,调查患者术后８ｈ     

Comparative Pharmacodynamic Modeling of the Electroencephalography-slowing Effect of Isoflurane, Sevoflurane, and Desflurane

Background: The most common measure to compare potencies of volatile anesthetics is minimum alveolar concentration (MAC), although this value describes only a single point on a quantal concentration-response curve and most likely reflects more the effects on the spinal cord rather than on the brain. To obtain more complete concentration-response curves for the cerebral effects of isoflurane, sevoflurane, and desflurane, the authors used the spectral edge frequency at the 95th percentile of the power spectrum (SEF95) as a measure of cerebral effect.

Methods: Thirty-nine patients were randomized to isoflurane, sevoflurane, or desflurane groups. After induction with propofol, intubation, and a waiting period, end-tidal anesthetic concentrations were randomly varied between 0.6 and 1.3 MAC, and the EEG was recorded continuously. Population pharmacodynamic modeling was performed using the software package NONMEM.

Results: The population mean EC50 values of the final model for SEF (95) suppression were 0.66 +/- 0.08 (+/- SE of estimate) vol% for isoflurane, 1.18 +/- 0.10 vol% for sevoflurane, and 3.48 +/- 0.66 vol% for desflurane. The slopes of the concentration-response curves were not significantly different; the common value was [Greek small letter lambda] = 0.86 +/- 0.06. The Ke0 value was significantly higher for desflurane (0.61 +/- 0.11 min-1), whereas separate values for isoflurane and sevoflurane yielded no better fit than the common value of 0.29 +/- 0.04 min (-1). When concentration data were converted into fractions of the respective MAC values, no significant difference of the C50 values for the three anesthetic agents was found.     

Bispectral index values at sevoflurane concentrations of 1% and 1.5% in lower segment cesarean delivery

Inadequate hypnosis in the absence of opioid analgesia may account for the increased incidence of awareness in cesarean delivery. An end-tidal concentration of 0.5 MAC isoflurane in 50% nitrous oxide (N(2)O) during cesarean delivery resulted in bispectral index (BIS) values >60, the threshold below which consciousness is unlikely. Our aim was to determine the BIS values achieved with the equivalent end-tidal concentration of sevoflurane and to determine if a larger concentration would consistently maintain BIS values <60. Twenty ASA physical status I-II parturients were randomized to receive an end-tidal concentration of either 1% sevoflurane or 1.5% sevoflurane delivered in 50% N(2)O throughout surgery. Thiopental 4 mg/kg was used for anesthetic induction. Morphine 0.1-0.15 mg/kg was administered only after delivery. Mean BIS values in the period between skin incision and neonatal delivery were 61 (95% confidence interval, 57-64) in the 1% sevoflurane group, versus 42 (95% confidence interval, 37-47) in the 1.5% sevoflurane group. BIS values were significantly different between groups at skin incision, uterine incision, delivery, and 10 min after delivery, but not thereafter. Indices of maternal and neonatal outcome were similar between groups. IMPLICATIONS: Bispectral index (BIS) values <60 are consistent with a high probability of unconsciousness. An end-tidal concentration of 1.5% sevoflurane maintained BIS values <60 during cesarean delivery, whereas 1% did not. Adverse effects were not seen with the use of larger concentrations of sevoflurane.     

地氟烷和七氟烷在稳态条件下对脑氧饱和度的影响

我们研究了七氟烷和地氟烷对局部脑组织氧饱和度（rSO2）的影响。22例经腹行子宫切除术的患者在稳态条件下以随机交叉的方式间隔30分钟吸入七氟烷和地氟烷各15分钟，维持脑电双频指数（bispectral index，BIS）值为40～50。另一组接受同样手术和麻醉的22例患者维持BIS值为20—30。在每种麻醉药15分钟的维持期间，每3分钟记录一次稳态条件下的rSO2、BIS、麻醉药吸入浓度和呼气末浓度、呼气末二氧化碳、SpO2、舒张压和收缩压以及心率。当BIS值维持于40～50或20—30时，两种麻醉药的rSO2均无差异。维持BIS值为40～50和20—30所需地氟烷和七氟烷的MACBIS值分别为1．0和1．2（P=0．004）及1．6和1．8（P〈0．001）。吸入1．6MAC地氟烷的rSO，值（71±13）高于1MAC时的rSO2值（66±10，P〈0．001），吸入1．8MAC七氟烷的rSO2值（72±11）高于1．2MAC时的rSO2值（66±13，P〈0．001）。因此，BIS值等效浓度的地氟烷或七氟烷的rSO，值相似，而提高两种麻醉药的吸入浓度均可增加rSO2值。