分娩镇痛时硬膜外左旋布比卡因运动阻滞的半数有效浓度

目的 确定分娩镇痛时硬膜外左旋布比卡因运动阻滞的半数有效浓度(EC50).方法 30例ASAI级初产妇,在第一产程宫颈开至2～3 cm时,L2,3硬膜外间隙穿刺,注射负荷量左旋布比卡因10ml,第1例产妇的左旋布比卡因浓度为0.5%,应用序贯法确定下一例产妇的药物浓度,相邻浓度比值为0.95.注药后30 min采用改良Bromage评分法评价下肢运动阻滞程度.结果 左旋布比卡因运动阻滞的EC50为0.562%,95%可信区间为0.542%～0.584%.结论 分娩镇痛时第一产程硬膜外左旋布比卡因(10 ml)运动阻滞的EC50为0.562%,95%可信区间为0.542%～0.584%.     

序贯试验测定自然分娩时硬膜外罗哌卡因镇痛的EC50

目的 测定自然分娩第一产程时硬膜外罗哌卡因的局部镇痛的半数有效浓度（effective concentrations in50% patient,EC50)。方法 选择33例产前无服用镇痛催眠药史的足月初产妇（ASAⅠ-Ⅱ级），宫口开张2-3cm时行硬膜外穿刺置管，注入20ml罗哌卡因溶液，以上一产妇的结果，根据双盲，序贯方法确定所用的罗哌卡因药液浓度，视觉模拟评分（VAS）小于3分时为有效。初始的罗哌卡因浓度定为0.15%。结果 共3例产妇因结果可疑而被排除，余30例产妇结果呈有效或无效而进入分析。结果显示，第一产程时硬膜外罗哌卡因镇痛的EC50是0.063%(95%可信区间为：0.05972%-0.06699%)。结论 利用序贯试验方法测定自然分娩时硬膜外罗哌卡因镇痛的EC50是0.063%。     

硬膜外混合不同浓度舒芬太尼分娩镇痛时罗哌卡因的半数有效浓度

目的测定产妇硬膜外分娩镇痛时不同浓度舒芬太尼混合罗哌卡因的半数有效浓度(EC50),寻找舒芬太尼混合罗哌卡因的适宜浓度。方法100例ASAⅠ或Ⅱ级的足月初产妇,妊娠37～42周,随机分为2组:0.4μg/ml舒芬太尼混合罗哌卡因组(A组)(n=45)和0.6μg/ml舒芬太尼混合罗哌卡因组(B组)(n=55)。2组均在宫口扩张至2～3 cm时行硬膜外穿刺,置管。2组第1例产妇罗哌卡因浓度均为0.12%,随后的罗哌卡因浓度按序贯法确定:即前1例若镇痛有效(注药后30 min时VAS评分≤3分)。则下1例接受的药物降低一个浓度梯度,若镇痛无效,则上升一个浓度梯度,浓度梯度0.01%。若镇痛效果可疑,则下1例接受的药物维持原浓度,计算罗哌卡因的EC50及其95%可信区间。观察镇痛期间发生的不良反应。结果A组、B组皮肤瘙痒发生率分别为11.9%、29.4%(P< 0.05),A组、B组各有1例发生恶心呕吐(P>0.05)。A组罗哌卡因的EC50为0.059%(95%可信区间为0.056%～0.062%),B组罗哌卡因的EC50为0.054%(95%可信区间为0.053%～0.055%)。结论硬膜外混合0.4、0.6μg/ml舒芬太尼分娩镇痛时,罗哌卡因的EC50分别为0.059%、0.054%;舒芬太尼的推荐浓度为0.4μg/ml。     

不同浓度芬太尼对硬膜外罗哌卡因分娩镇痛效应的影响

目的 观察不同浓度芬太尼对硬膜外罗哌卡因分娩镇痛效应的影响。方法 本研究为多中心、随机、双盲对照研究，选择要求分娩镇痛的初产妇128例，ASAⅠ或Ⅱ级，随机分为4组，FD组（n=33）：单纯罗哌卡因组；F1组（n=30）：罗哌卡因混合1μg/ml芬太尼组；F2组（n=33）：罗哌卡因混合2μg/ml芬太尼组；F3组（n=32）：罗哌卡因混合3μg/ml芬太尼组。所有产妇于L2．3硬膜外穿刺头向置管，注入15ml药液。各组初始罗哌卡因浓度为0．12％，其后每例产妇所用浓度按双盲、序贯法进行调整。以VAS评价产妇注药30min内镇痛效果，计算硬膜外罗哌卡因分娩镇痛的半数有效浓度（EC50），记录注药后30min产妇收缩压、心率及胎儿心率、运动阻滞程度及不良反应发生情况。结果 共有124例完成试验观察。各组硬膜外罗哌卡因分娩镇痛的EC50及其95％可信区间（95％CI）为：F0组：0．110％及0．1090％-0．1116％；F1组：0．089％及0．0877％-0．0911％；F2组：0．073％及0．0717％～0．0744％；F3组：0．060％及0．0560％～0．0634％，F1、F2、F3组EC50低于F0组（P〈0．01）。硬膜外注药后30min内，产妇心率、血压、胎儿心率均在正常范围，各组运动阻滞程度比较差异无统计学意义（P〉0．05）；与F0组比较，乃组皮肤瘙痒发生率升高（P〈0．05）。结论 硬膜外混合低浓度芬太尼（1-3μg/ml）能增强0．12％罗哌卡因分娩镇痛效果，推荐芬太尼的安全浓度范围为1～2μg/ml。     

蛛网膜下腔罗哌卡因产妇分娩的最低镇痛剂量

腰麻-硬膜外联合阻滞起效迅速而且能持续镇痛,是分娩镇痛常用的方法。罗哌卡因和布比卡因是分娩镇痛中常用的腰麻药物。Stocks等报道蛛网膜下腔布比卡因产妇分娩的第一产程的最低镇痛剂量(MLAD)为1.99 mg(95%可信区间1.71-2.27 mg)。本研究拟采用序贯法确定蛛网膜下腔罗哌卡因国人分娩的MLAD。     

不同浓度罗哌卡因复合舒芬太尼分娩镇痛对产妇产间发热的影响

目的研究不同浓度罗哌卡因复合舒芬太尼硬膜外注射用于分娩镇痛对产妇产间发热及致热因子的影响。方法适合阴道分娩、自愿要求分娩镇痛的初产妇120例,孕37～41周,年龄20～35岁,ASA I或Ⅱ级,随机分为三组:0.075%罗哌卡因组(A组)、0.1%罗哌卡因组(B组)和0.125%罗哌卡因组(C组),每组40例。宫口扩张至3 cm时实施硬膜外分娩镇痛,A组0.075%罗哌卡因+舒芬太尼0.5μg/ml;B组0.1%罗哌卡因+舒芬太尼0.5μg/ml;C组0.125%罗哌卡因+舒芬太尼0.5μg/ml。记录镇痛后1、2、3、4和5 h、胎儿娩出即刻、分娩后2 h产妇鼓膜温度;分别在镇痛前、胎儿娩出即刻及分娩后2 h采集产妇静脉血,测定血清IL-1β、IL-6、TNF-α浓度;记录产程时间;采用改良Bromage法评定三组产妇在镇痛后1 h及胎儿娩出即刻的运动神经阻滞程度。结果与镇痛前比较,镇痛后5 h及胎儿娩出即刻三组鼓膜温度明显升高,C组发热率明显高于A组和B组(P0.05)。与镇痛前比较,胎儿娩出即刻三组血清IL-1β、IL-6、TNF-α浓度明显升高(P0.05)。C组第二产程和镇痛时间明显长于A组和B组,B组第二产程和镇痛时间明显长于A组(P0.05)。三组运动神经阻滞程度差异无统计学意义。结论不同浓度罗哌卡因复合舒芬太尼硬膜外注射用于分娩镇痛均能产生良好的镇痛效果,低浓度罗哌卡因分娩镇痛产妇发热率低,产妇分娩期间发热与致热因子水平升高相关。     

不同浓度舒芬太尼或芬太尼对硬膜外罗哌卡因分娩镇痛效应的影响

目的研究不同浓度舒芬太尼或芬太尼对硬膜外罗哌卡因分娩镇痛效应的影响。方法采用多中心、随机、双盲对照法进行该试验。初产妇224例，ASAⅠ级或Ⅱ级，妊娠≥36周，产前未服用镇痛、催眠药，随机分为7组：单纯罗哌卡因组（Ⅰ组，n=33）、罗哌卡因混合0．2μg／ml舒芬太尼组（Ⅱ组，n=33）、罗哌卡因混合0．4vg／ml舒芬太尼组（Ⅲ组，n=32）、罗哌卡因混合0．6μg／ml舒芬太尼组（Ⅳ组，n=31）、罗哌卡因混合1μg／ml芬太尼组（Ⅴ组，n=32）、罗哌卡因混合2μg／ml芬太尼组（Ⅵ组，n=31）及罗哌卡因混合3μg／ml芬太尼组（Ⅶ组，n=32）。所有产妇宫Vt开至2—3cm时，于L2，3间隙硬膜外穿刺头向置管，分别注人15ml罗哌卡因与不同浓度的舒芬太尼或芬太尼混合药液。各组初始的罗哌卡因浓度为0．12％，采用双盲、序贯法，以上一例产妇的镇痛效果确定下一例产妇所用的罗哌卡因药液浓度。采用视觉模拟评分法（VAS）评价注药30min内的疼痛程度，计算硬膜外罗哌卡因分娩镇痛的半数有效浓度（EC50），记录注药后30min产妇心率、收缩压及胎儿心率、运动阻滞程度及不良反应的发生情况。结果共有214例完成试验。硬膜外注药后30min内，产妇心率、收缩压及胎胎儿心率均在正常范围内，各组运动程度阻滞程度差异无统计学意义（P〉0．05）；与Ⅰ组比较，Ⅳ组和Ⅶ组不良反应发生率升高（P〈0．05）。各组硬膜外罗哌卡因分娩镇痛的EC50及其95％可信区间（95％CI）为：Ⅰ组0．1100％及0．1057％-0．1159％，Ⅱ组0．0741％及0．0708％．0.0789％，Ⅲ组0．0474％及0.0405％-0．0556％，Ⅳ组0．0355％及0．0289％-0．0438％，Ⅴ组0.0890％及0．0877％．0．0911％，Ⅵ组0．0730％及0．0717％-0．0744％，Ⅶ组0．0610％及0．0560％-0．0635％；Ⅱ-Ⅶ组EC50低于Ⅰ组（P〈0.05）；与Ⅱ组、Ⅵ组及Ⅶ组比较，Ⅲ组及Ⅳ组EC50降低（P〈0．05）。结论硬膜外混合舒芬太尼（0.2～0．6μg/ml）或芬太尼（1—3μg／ml）可增强罗哌卡因分娩镇痛效果；舒芬太尼的镇痛效应明显强于芬太尼；硬膜外混合罗哌卡因分娩镇痛中，舒芬太尼、芬太尼的推荐浓度分别为0．4μg／ml、2μg/ml.     

硬膜外注射右美托咪啶用于患者镇痛的适宜剂量

目的 比较不同剂量右美托咪啶对罗哌卡因硬膜外阻滞半数有效浓度(EQ50)的影响,以探讨其硬膜外给药用于患者镇痛的适宜剂量.方法 拟行膝关节镜诊治术患者120例,年龄20～55岁,体重50～75 kg,ASA分级Ⅰ级,采用随机数字表法,将其随机分为4组(n=30).D0组:硬膜外注射罗哌卡因20 ml;D0.25组、D0.50组和D1.00组分别硬膜外注射罗哌卡因混合液含0.25、0.50和1.00μg/kg右美托咪啶.硬膜外注射罗哌卡因混合右美托咪啶的容量为20ml.D0组、D0.25组、D0.50组或D1.00组首例罗哌卡因浓度分别为0.40％、0.40％、0.28％和0.20％,按照序贯法调整罗派卡因浓度,升降幅度为0.02％.采用VAS评价对手术切皮的阻滞效果,VAS评分=0分为阻滞有效.采用概率单位法计算罗哌卡因EC50及其95％可信区间(95％CI).记录有关不良反应的发生情况.结果 D0组、D0.25组、D0.50组和D1.00组罗哌卡因EC50及95％ CI分别为0.38％(0.35～0.41)％、0.34％ (0.31 ～0.36)％、0.22％ (0.20～ 0.24)％和0.14％(0.12～0.15)％.D0组、D0.25组、D0.50组、D1.00组罗哌卡因EC50依次降低(P＜0.05);与D0组比较,D1.00组低血压和心动过缓的发生率升高(P＜0.05),D0.25组和D0.50组不良反应发生率差异无统计学意义(P＞0.05).结论 硬膜外注射右美托咪啶用于患者镇痛的适宜剂量为0.50μg/kg.     

罗哌卡因-芬太尼用于硬膜外和腰-硬联合阻滞分娩镇痛效果及安全性

目的比较罗哌卡因-芬太尼用于硬膜外阻滞(CEA)和腰-硬联合阻滞(CSEA)行分娩镇痛的临床效果及安全性。方法自愿接受分娩镇痛足月、单胎、头位初产妇40例,宫口扩张3～5cm时随机分为CEA组和CSEA组;无分娩镇痛的产妇为对照组(C组)。CEA组以0.1%罗哌卡因+芬太尼(2μg/ml)5ml为试验剂量,随后注入上述药物10ml。CSEA组蛛网膜下腔给予罗哌卡因2mg+芬太尼10μg。两组采用0.1%罗哌卡因+芬太尼2μg/ml硬膜外PCA。记录镇痛评分、下肢肌力、产程、分娩方式、药物用量、产妇满意度和新生儿1、5minApgar评分、脐带血罗哌卡因浓度。结果镇痛后5～30min,CSEA组VAS显著低于CEA组(P0.05);CSEA组罗哌卡因及芬太尼用量较CEA组明显减少(P0.05);两组脐带血罗哌卡因浓度差异无统计学意义。CSEA组和CEA组第一产程短于C组(P0.05)。与C组比较,CSEA组和CEA组自然分娩率较高,催产素使用率较高(P0.05)。与CEA组比较,CSEA组镇痛起效时间较短、催产素使用率较低,自然分娩率和产妇满意度更高(P0.05)。结论罗哌卡因-芬太尼用于CSEA和CEA均能提供满意且安全的分娩镇痛。CSEA因起效快、药物用量少、产妇满意度高而更适合分娩镇痛。     

右美托咪定局部用药对罗哌卡因臂丛神经阻滞半数有效浓度的影响

目的 通过评价右美托咪定局部用药对罗哌卡因臂丛神经阻滞半数有效浓度(EC50)的影响,探讨其局部用药的镇痛机制.方法 前臂及手部择期手术患者52例,年龄18 ～ 50岁,体重50～80 kg,ASA分级Ⅰ或Ⅱ级,拟在超声引导下行腋路臂丛神经阻滞.采用随机数字表法,将其分为2组(n=26),对照组(C组)神经阻滞时仅用罗哌卡因;右美托咪定组(D组)神经阻滞时局部注射罗哌卡因和0.8 μg/kg右美托咪定的混合液.以臂丛支配区痛觉消失为阻滞有效,局麻药容量30 ml,采用序贯法确定罗哌卡因浓度:初始浓度为0.50％,相邻浓度比值为1.2,阻滞有效则下一例采用低一级浓度,阻滞无效则下一例采用高一级浓度.用Dixon-Massey法确定EC50及其95％可信区间.结果 D组罗哌卡因EC50(95％可信区间)为0.32％ (0.30％ ～ 0.33％),C组为0.44％ (0.42％ ～ 0.46％).D组罗哌卡因EC50低于C组(P＜0.05).结论 右美托咪定局部用药可降低罗哌卡因臂丛神经阻滞的EC50,提示其具有局麻药样效应.     

潜伏期和活跃期硬膜外分娩镇痛对母婴影响的比较

目的 比较硬膜外分娩镇痛始于潜伏期与活跃期对母婴的影响.方法 自愿接受分娩镇痛的足月、单胎、头位初产妇80例,根据开始分娩镇痛的时机分为潜伏期(宫口扩张0.5～3.0 cm)组(L组,n=40)和活跃期(宫口扩张＞3.0 cm)组(A组,n=40).同时随机选取不接受分娩镇痛的足月、单胎、头位初产妇40例为对照组(C组).A组和L组均以L2,3间隙进行硬膜外穿刺,以0.1%罗哌卡因+芬太尼(2 μg/ml)5 ml为试验剂量,随后注入上述药物10 ml,硬膜外导管连接镇痛泵,药物同上,采用PCA模式,PCA量6 ml,间隔时间30 min.于镇痛前即刻(C组于宫口扩张3 cm时)、镇痛开始后5、10、15、30 min、宫口扩张7～8 cm及10 cm时行VAS评分,采用改良Bromage评分法测定下肢肌力.镇痛前取静脉血样,胎儿娩出即刻取母体静脉血样及脐带血样,采用放免法测定血浆皮质醇浓度,采用高效液相色谱法测定脐带血浆罗哌卡因浓度.记录镇痛时间、产程时间、分娩方式、催产素使用情况、药物用量、胎儿娩出后1、5 min时Apgar评分、产妇满意度评分及不良反应发生情况.结果 与C组比较,L组和A组镇痛开始后各时点VAS评分降低,胎儿娩出即刻母体血浆皮质醇浓度降低,第一产程时间缩短,催产素使用率升高,剖宫产率降低(P＜0.05),其余指标差异无统计学意义(P＞0.05).与L组比较,A组镇痛时间缩短(P＜0.05),其余指标差异无统计学意义(P＞0.05).3组间脐带血浆皮质醇浓度比较差异无统计学意义(P＞0.05).结论 硬膜外分娩镇痛始于潜伏期与活跃期均能降低剖宫产机率,在其程度上无差异,且不延长产程,对新生儿同样安全.

Abstract：

Objective To compare the effects of labor epidural analgesia initiated in latent phase and active phase on parturients and neonates. Methods One hundred twenty nulliparous women at full term (single, head presentation, ASA Ⅰ or Ⅱ ) were randomly divided into 3 groups (n=40 each):control group(group C) ; PCEA initiated in latent phase group (cervical dilatation 0.5-3.0 cm) (group L) and PCEA initiated in active phase group (cervical dilatation＞3.0 cm) (group A). Epidural catheter was placed through L2,3 interspace. 0.1% ropivacaine with fentanyl 2 μg/ml was used for PCEA. A test dose of 5 ml was followed by a loading dose of 10 ml. PCEA device was programmed to allow a bolus of 6 ml with a 30 min lockout interval. The intensity of pain was measured with VAS (0=no pain, 10=worst pain) before analgesia, at 5, 10, 15 and 30 min after beginning of PCEA and cervical dilatation of 7-8 cm and 10 cm. Degree of motor block was assessed by lower extremity muscle strength (modified Bromage scale,0=no motor block, 3=inability to flex ankle joints).Plasma cortisol in maternal venous blood obtained before analgesia and at delivery of fetus and in umbilical cord blood and plasma ropivacaine concentrations in umbilical core blood were determined.The length of every stage, duration of analgesia,delivery mode, the amount of oxytocin used, maternal satisfaction, Apgar scores of the neonates and adverse effects were recorded. Results PCEA initiated in latent phase or active phase significantly reduced VAS score, the plasma cortisol level at delivery, the duration of 1st stage of labor, and the rate of cesarean section and increased the use of oxytocin in L and A groups as compared with group C, but there was no significant difference in the above variables between L and A groups. The duration of analgesia was shorter in group A than in group L. Conclusions Labor epidural analgesia initiated in latent phase or active phase can decrease the rate of cesarean section but does not prolong the duration of labor and is safe for the newborn.     

罗哌卡因复合芬太尼用于可行走硬膜外分娩镇痛的可行性

目的 探讨0．075％罗哌卡因或布比卡因与芬太尼2μg/ml的混合液用于可行走硬膜外分娩镇痛的可行性。方法 60例初产妇随机分为三组：A组（n＝20）0．075％罗哌卡因＋芬太尼2μg/ml;B组（n＝20）0．075％布比卡因＋芬太尼2μg/ml;C级（n＝20）为对照组。采用双盲法进行视觉模拟疼痛评分（VAS）和行走功能的评定。记录各组产妇的生命体征、胎心率（FHR）、产程时间、分娩方式、催产素用量以及新生儿Apgar评分和脐静脉血气分析,并测定用药前和宫口开全时母体血清皮质醇浓度。结果 A、B两组产妇均获得良好镇痛效果,镇痛后A组所有产妇均能下床行走和自主排尿,而B组仅70％产妇能下床行走和自主排尿,两组比较有显著性差异（P＜0．05）;A、B两组第一产程末血清皮质醇浓度明显低于C组（P＜0．05）。产程时间、分娩方式和新生儿Apgar评分各组间均无差异（P＞0．05）。结论 0．075％罗哌卡因和芬太尼2μg/ml的混合液有效安全地用于可行走硬膜外分娩镇痛。     

Relative analgesic potencies of ropivacaine and bupivacaine for epidural analgesia in labor: implications for therapeutic indexes

BACKGROUND: The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to assess the relative analgesic potencies of epidural bupivacaine and ropivacaine by determining their respective minimum local analgesic concentrations. METHODS: Seventy-three parturients at < or = 7 cm cervical dilation who requested epidural analgesia were allocated to one of two groups in this double-blinded, randomized, prospective study. After a lumbar epidural catheter was placed, 20 ml of the test solution was given, either ropivacaine (n = 34) or bupivacaine (n = 39). The concentration of local anesthetic was determined by the response of the previous patient in that group to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scores with < or = 10 mm within 30 min defined as effective. An effective result directed a 0.01% wt/vol decrement for the next patient. An ineffective result directed a 0.01% wt/vol increment. RESULTS: The minimum local analgesic concentration of ropivacaine was 0.111% wt/vol (95% confidence interval, 0.100-0.122), and the minimum local analgesic concentration of bupivacaine was 0.067% wt/vol (95% confidence interval, 0.052-0.082). Ropivacaine was significantly less potent than bupivacaine, with a potency ratio of 0.6 (95% confidence interval, 0.49-0.74). No difference in motor effects was observed. CONCLUSION: Ropivacaine was significantly less potent than bupivacaine for epidural analgesia in the first stage of labor.     

Dose-response study of epidural ropivacaine for labor analgesia

BACKGROUND: Ropivacaine has been introduced for use in epidural analgesia in labor. However, there have been few formal dose-response studies of ropivacaine in this setting. METHODS: The authors performed a prospective, randomized, double-blind study examining the effectiveness of five different doses of ropivacaine (10, 20, 30, 40, and 50 mg) administered epidurally in a volume of 10 ml to establish analgesia in 66 parturients who were in active labor with cervical dilatation less than 4 cm. A dose was considered effective when the visual analog scale pain score decreased by 50% or more from baseline. RESULTS: A sigmoid dose-response curve and a probit log dose-response plot (linear regression coefficient, r = 0.84; coefficient of determination, r2 = 0.71) were obtained. The ED50 (median effective dose) obtained based on the maximum likelihood estimation was 18.4 mg (95% confidence interval, 13.4-25.4 mg). Time to onset of analgesia, duration of analgesia, time to two-segment regression of sensory block level, and incidence of motor block were not affected by the dosage of ropivacaine administered (P = 0.93, 0.12, 0.55, and 0.39, respectively). However, the upper level of sensory block was dose-related (P < 0.01). CONCLUSION: In a traditional dose-response study, the ED50 of ropivacaine required to initiate epidural analgesia in early labor was found to be 18.4 mg (95% confidence interval, 13.4-25.4 mg).     

The effect of clonidine on the minimum local analgesic concentration of epidural ropivacaine during labor

On the basis of the determination of minimum local analgesic concentration (MLAC), ropivacaine has been demonstrated to be less potent than bupivacaine during the first stage of labor. In this study we assessed the effect of clonidine on the MLAC of ropivacaine. Seventy-seven parturients of mixed parity requesting epidural analgesia for labor (cervical dilation, 3-7 cm) were included in the study. They received an epidural bolus of either ropivacaine (n = 30), ropivacaine plus clonidine 30 microg (n = 28), or ropivacaine plus clonidine 60 microg (n = 19) in the second part of the study. The concentration of the ropivacaine solution was determined by the response of the previous parturient in that group by using an up-down sequential allocation. A visual analog pain score of < or =10 mm within 30 min after the epidural bolus (20 mL) was considered an effective response. An effective result directed a 0.01% wt/vol decrement for the next patient. An ineffective result directed a 0.01% wt/vol increment. The MLAC of ropivacaine was 0.097% wt/vol (95% confidence interval, 0.085%-0.108%). It was unaffected by a 30-microg dose of epidural clonidine (0.081% [0.045%-0.117%]) but was significantly decreased by a 60-microg clonidine dose (0.035% [0.024%-0.046%]) (P < 0.001). This study documents a decrease in the MLAC of ropivacaine by clonidine, significant for a 60- microg dose. IMPLICATIONS: Epidural ropivacaine potency in labor can be increased by the addition of epidural clonidine. This study demonstrates that 60 microg of epidural clonidine significantly decreases the minimum local analgesic concentration of ropivacaine during the first stage of labor but is associated with sedation.     

The effects of age on the median effective concentration of ropivacaine for motor blockade after epidural anesthesia with ropivacaine

Minimal local analgesic concentrations have been defined as the median effective concentration (EC50). In this study, we sought to examine the effect of age on motor blockade and determine the motor block EC50 of elderly patients after epidural administration of ropivacaine in patients undergoing urological or minor lower limb surgery. ASA physical status I-II patients were enrolled in 1 of 2 age groups (Group 1: > or =70 yr; Group 2: <70 yr). Each received a 15-mL bolus of epidural ropivacaine without epinephrine. The first patient in each group received 0.425%. Up-down sequential allocation was used to determine subsequent concentrations at a testing interval of 0.025%. Effective motor blockade was defined as a modified Bromage score >0 within 30 min. The motor blockade EC50 of ropivacaine was 0.383% (95% confidence interval, 0.358%-0. 409%) in group 1 and 0.536% (95% confidence interval, 0.512%-0.556%) in group 2 (P < 0.01). We conclude that age is a determinant of motor blockade EC50 of ropivacaine with epidural administration.     

硬膜外分娩镇痛对分娩方式的影响

目的 评价硬膜外分娩镇痛对分娩方式的影响.方法 初产妇400例,ASA Ⅰ或Ⅱ级,足月、单胎、头位,无妊娠并发症及硬膜外麻醉禁忌证.分为硬膜外镇痛组和非镇痛组(n=200).硬膜外镇痛组宫口开至3 cm时,采用0.1%罗哌卡因混合0.5 μg/ml舒芬太尼行硬膜外镇痛,宫口开全后停止镇痛.记录镇痛前和镇痛15 min时VAS评分;评价运动阻滞程度;记录分娩方式、第一产程、第二产程、新生儿出生后1、5 min时Apgar评分和新生儿体重;记录镇痛过程中不良反应的发生情况.结果 硬膜外镇痛组镇痛15 min时VAS评分由(8.3±0.8)分降至(1.6±1.1)分(P＜0.05).与非镇痛组比较,硬膜外镇痛组顺产率和阴道器械助产率升高,剖宫产率降低,第一产程和第二产程延长(P＜0.05).2组新生儿出生后1、5 min时Apgar评分和新生儿体重比较差异无统计学意义(P＜0.05).硬膜外镇痛组下肢运动阻滞发生率为0.5%,下肢麻木发生率为9.0%,恶心呕吐发生率为1.5%.结论 硬膜外分娩镇痛可降低剖宫产率,提高自然分娩率.     

The relative motor blocking potencies of epidural bupivacaine and ropivacaine in labor

Minimal local analgesic concentrations (MLAC) have been used to determine the epidural analgesic potencies of bupivacaine and ropivacaine. There are no reports of the motor blocking potencies of these drugs. We sought to determine the motor block MLAC of both drugs and their relative potency ratio. Sixty ASA physical status I and II parturients were randomized to one of two groups, during the first stage of labor. Each received a 20-mL bolus of epidural bupivacaine or ropivacaine. The first woman in each group received 0.35%. Up-down sequential allocation was used to determine subsequent concentrations at a testing interval of 0.025%. Effective motor block was defined as a Bromage score <4 within 30 min. The up-down sequences were analyzed by using the Dixon and Massey method and probit regression to quantify the motor block minimal local analgesic concentration. Two-sided P < 0.05 defined significance. The motor block minimal local analgesic concentration for bupivacaine was 0.326% (95% confidence interval [CI], 0.285-0.367) and for ropivacaine was 0.497% (95% CI, 0.431-0.563) (P = 0.0008). The ropivacaine/bupivacaine potency ratio was 0.66 (95% CI, 0.52-0.82). This is the first MLAC study to estimate the motor blocking potencies of bupivacaine and ropivacaine. Ropivacaine was significantly less potent for motor block, at 66% that of bupivacaine. IMPLICATIONS:The results of this study demonstrate that epidural ropivacaine is less potent than epidural bupivacaine in producing motor blockade during labor. The motor block potency relation is similar to the sensory potency ratio for these two drugs.     

Dose-Response Study of Epidural Ropivacaine for Labor Analgesia

Background: Ropivacaine has been introduced for use in epidural analgesia in labor. However, there have been few formal dose-response studies of ropivacaine in this setting.

Methods: The authors performed a prospective, randomized, double-blind study examining the effectiveness of five different doses of ropivacaine (10, 20, 30, 40, and 50 mg) administered epidurally in a volume of 10 ml to establish analgesia in 66 parturients who were in active labor with cervical dilatation less than 4 cm. A dose was considered effective when the visual analog scale pain score decreased by 50% or more from baseline.

Results: A sigmoid dose-response curve and a probit log dose-response plot (linear regression coefficient, r = 0.84; coefficient of determination, r2 = 0.71) were obtained. The ED50 (median effective dose) obtained based on the maximum likelihood estimation was 18.4 mg (95% confidence interval, 13.4-25.4 mg). Time to onset of analgesia, duration of analgesia, time to two-segment regression of sensory block level, and incidence of motor block were not affected by the dosage of ropivacaine administered (P = 0.93, 0.12, 0.55, and 0.39, respectively). However, the upper level of sensory block was dose-related (P < 0.01).