分娩镇痛时硬膜外罗哌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罗哌卡因运动阻滞的半数有效浓度(EC50).方法 30例ASA Ⅰ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,头端置管3 cm,注射负荷量罗哌卡因10 ml,第1例产妇罗哌卡因浓度为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1.04.注药后30 min时采用改良Bromage评分评价下肢运动阻滞程度.结果 罗哌卡因运动阻滞的EC50为0.674%,95%可信区间为0.651%～0.697%.结论 分娩镇痛时第一产程硬膜外罗哌卡因(10 ml)运动阻滞的EC50为0.674%,95%可信区间为0.651%～0.697%.     

老年患者左旋布比卡因硬膜外运动阻滞的半数有效浓度

目的 研究老年和青壮年患者左旋布比卡因硬膜外运动阻滞的半数有效浓度(EC50).方法 60例下肢或下腹部择期手术患者分成老年组(A组,≥70岁)和青壮年组(Y组,<70岁),每组30例.硬膜外穿刺置管后注入15 ml不同浓度的左旋布比卡因:每组第一位患者左旋布比卡因浓度均定为0.375%,其后各患者所用浓度按序贯法进行选择,浓度变化梯度定为0.025%.以改良Bromage评分法判断运动阻滞程度,计算硬膜外左旋布比卡因运动阻滞的EC50.结果 A组左旋布比卡因硬膜外运动阻滞的EC50为0.349%(95%可信区间:0.327%～0.373%),显著低于Y组的0.453%(95%可信区间:0.424%～0.484%)(P<0.01).结论 与青壮年患者相比,老年患者左旋布比卡因硬膜外运动阻滞的EC50明显降低.     

妇科硬膜外左旋布比卡因最低感觉及运动阻滞浓度

目的 测定妇科手术左旋布比卡因最低感觉及运动阻滞浓度即半数有效浓度(EC50).方法 70例妇科手术患者随机分为感觉组和运动组,每组35例.择L2～3行硬膜外穿刺置管后分次给予预定浓度芹旋布比卡因总量为15 ml:第一例感觉组浓度为0.150%,运动组为0.375%,其后各患者的药物浓度以序贯法进行选择,相邻级别浓度比感觉组为0.980.运动组为0.944.以VAS和改良Bromage评分法分别判断感觉和运动阻滞程度.结果 硬膜外左旋布比卡因感觉阻滞EC50为0.140%(95% CI:0.136%～0.144%),显著低于运动阻滞的EC50 0.385%(95% CI:0.359%～0.414%)(P＜0.01),左旋布比卡因感觉与运动阻滞分离区间是0.140%～0.385%.结论 妇科硬膜外左旋布比卡因感觉和运动阻滞EC50.分别为0.140%和0.385%.     

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%。     

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。     

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。     

剖宫产术患者左旋布比卡因蛛网膜下腔阻滞的量效关系

目的 确定剖宫产术患者左旋布比卡因蛛网膜下腔阻滞的量效关系.方法 择期剖宫产术患者印例,年龄25～35岁,体重60～90 kg,ASA Ⅰ或Ⅱ级,随机分为4组(n=15),于L3,4蛛网膜下腔穿刺成功后,分别注射左旋布比卡因7.5 mg(L1组)、10 mg(L2组)、12.5 mg(L3组)和15 mg(L4组),均用5%葡萄糖稀释至3 ml,注药时间30 s.采用视觉模拟评分法(VAS)评价切皮即刻患者疼痛程度,0分为无痛,10分为剧痛.VAS评分=0分为镇痛有效;VAS评分≥1分为镇痛无效,硬膜外追加1%利多卡因5～10 ml.采用Probit法计算50%和95%患者镇痛有效的左旋布比卡因剂量(ED50和ED95)及其95%可信区间.结果 左旋布比卡因的ED50及其95%可信区间为9.0(7.8～9.9)mg,ED95及其95%可信区间为13.2(11.6～17.6)mg.结论 剖宫产术患者左旋布比卡因蛛网膜下腔阻滞的ED50和ED95分别为9.0、13.2 mg.     

等效浓度左旋布比卡因与罗哌卡因硬膜外分娩镇痛质量的比较

目的 比较等效浓度的左旋布比卡因与罗哌卡因硬膜外分娩镇痛质量.方法 选择自愿接受硬膜外分娩镇痛的初产妇120例,ASA Ⅰ或Ⅱ级、头位、单胎、孕期≥36周,按双盲原则随机分为左旋布比卡因组(L组)和罗哌卡因组(R组),每组60例.镇痛液分别为0.125%左旋布比卡因或0.15%罗哌卡因复合2 μg/ml芬太尼.记录产妇的VAS评分、镇痛药用量、镇痛时间、补救措施次数、产程、分娩方式及恶心、呕吐等不良反应发生率.对镇痛不全/镇痛失败产妇进行Logistic回归分析,寻找影响镇痛质量的因素.结果 两组患者镇痛不全和镇痛失败共24例,合并后行Logistic回归分析发现影响镇痛质量的因素有首剂量后VAS评分≥30 mm、镇痛时间超过6 h、持续性枕后位.结论 0.125%左旋布比卡因与0.15罗哌卡因复合2 μg/ml芬太尼均可提供满意的硬膜外分娩镇痛效果.     

不同浓度左旋布比卡因伍用芬太尼用于硬膜外分娩镇痛的临床观察

分娩疼痛不仅造成产妇痛苦，而且影响母婴平安。硬膜外分娩镇痛以其镇痛效果确切、简便易行，对产妇影响小广泛应用临床。硬膜外分娩镇痛既要有良好的镇痛效果又要尽可能地保留产妇的运动能力，因此镇痛液中局麻药浓度要适中。本研究拟对比观察不同浓度的左旋比布卡因伍用芬太尼用于硬膜外分娩镇痛，比较其镇痛效果和对产时产力的影响，找出适宜的左旋布比卡因浓度。     

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。     

Relative analgesic potencies of levobupivacaine and ropivacaine for epidural analgesia in labor

BACKGROUND: The minimum local analgesic concentration has been defined as the median effective local analgesic concentration (EC50) 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 levobupivacaine and ropivacaine by determination of their respective minimum local analgesic concentrations. METHODS: Parturients at 7 cm of cervical dilation or less who requested epidural analgesia were allocated to one of two groups in this double-blind, randomized, prospective study. After lumbar epidural catheter placement, 20 ml of the test solution was given: levobupivacaine (n = 35) or ropivacaine (n = 35). 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 scale scores, with 10 mm or less 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: Of 105 women enrolled, 35 were excluded, leaving 70 for analysis. The minimum local analgesic concentration of levobupivacaine was 0.087% wt/vol (95% CI, 0.081-0.094%), and the minimum local analgesic concentration of ropivacaine was 0.089% wt/vol (95% CI, 0.075-0.103%). Levobupivacaine and ropivacaine were of similar potency with a ropivacaine:levobupivacaine potency ratio of 0.98 (95% CI, 0.80-1.20). No difference in motor effects was observed. CONCLUSIONS: This study demonstrated that levobupivacaine and ropivacaine are of similar potency for epidural analgesia in the first stage of labor.     

Relative Analgesic Potencies of Levobupivacaine and Ropivacaine for Epidural Analgesia in Labor

Background: The minimum local analgesic concentration has been defined as the median effective local analgesic concentration (EC50) 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 levobupivacaine and ropivacaine by determination of their respective minimum local analgesic concentrations.

Methods: Parturients at 7 cm of cervical dilation or less who requested epidural analgesia were allocated to one of two groups in this double-blind, randomized, prospective study. After lumbar epidural catheter placement, 20 ml of the test solution was given: levobupivacaine (n = 35) or ropivacaine (n = 35). 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 scale scores, with 10 mm or less 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: Of 105 women enrolled, 35 were excluded, leaving 70 for analysis. The minimum local analgesic concentration of levobupivacaine was 0.087% wt/vol (95% CI, 0.081-0.094%), and the minimum local analgesic concentration of ropivacaine was 0.089% wt/vol (95% CI, 0.075-0.103%). Levobupivacaine and ropivacaine were of similar potency with a ropivacaine:levobupivacaine potency ratio of 0.98 (95% CI, 0.80-1.20). No difference in motor effects was observed.     

A Randomized Sequential Allocation Study to Determine the Minimum Effective Analgesic Concentration of Levobupivacaine and Ropivacaine in Patients Receiving Epidural Analgesia for Labor

Background: This study was designed to determine and compare the minimum local analgesic concentrations of levobupivacaine and ropivacaine when used in epidural obstetric analgesia.

Methods: In a double-blind study, healthy women requiring epidural analgesia for labor pain were randomized to receive either ropivacaine or levobupivacaine. Drugs were administered as a 20-ml epidural bolus. The concentration of each started at 0.11% and increased or decreased at intervals of 0.01%, depending on the response of the previous patient, using the technique of up-down sequential allocation. Minimum local analgesic concentrations were calculated using the formula of Dixon and Massey. Efficacy was assessed using visual analog pain scores and motor and sensory block assessments, and safety was assessed by recording maternal and fetal/neonate vital signs and adverse events.

Results: Forty-seven patients received levobupivacaine, and 47 received ropivacaine. Minimum local analgesic concentrations for levobupivacaine (0.077%; 95% CI, 0.058-0.096%) were lower than those for ropivacaine (0.092%; 95% CI, 0.082-0.102%). The 0.015% difference was not statistically significant. There was no notable difference between treatment groups in the proportion of patients reporting drug-related adverse events.     

A randomized sequential allocation study to determine the minimum effective analgesic concentration of levobupivacaine and ropivacaine in patients receiving epidural analgesia for labor

BACKGROUND: This study was designed to determine and compare the minimum local analgesic concentrations of levobupivacaine and ropivacaine when used in epidural obstetric analgesia. METHODS: In a double-blind study, healthy women requiring epidural analgesia for labor pain were randomized to receive either ropivacaine or levobupivacaine. Drugs were administered as a 20-ml epidural bolus. The concentration of each started at 0.11% and increased or decreased at intervals of 0.01%, depending on the response of the previous patient, using the technique of up-down sequential allocation. Minimum local analgesic concentrations were calculated using the formula of Dixon and Massey. Efficacy was assessed using visual analog pain scores and motor and sensory block assessments, and safety was assessed by recording maternal and fetal/neonate vital signs and adverse events. RESULTS: Forty-seven patients received levobupivacaine, and 47 received ropivacaine. Minimum local analgesic concentrations for levobupivacaine (0.077%; 95% CI, 0.058-0.096%) were lower than those for ropivacaine (0.092%; 95% CI, 0.082-0.102%). The 0.015% difference was not statistically significant. There was no notable difference between treatment groups in the proportion of patients reporting drug-related adverse events. CONCLUSIONS: Levobupivacaine was 19% more potent than ropivacaine and provided similar safety results.     

Postoperative epidural analgesia after total knee arthroplasty with sufentanil 1 microg/ml combined with ropivacaine 0.2%, ropivacaine 0.125%, or levobupivacaine 0.125%: a randomized, double-blind comparison

BACKGROUND AND OBJECTIVES: Total knee replacement is associated with severe postoperative pain that, if treated insufficiently, interferes with early rehabilitation. The purpose of the present study is to compare the efficacy of ropivacaine (0.2% and 0.125%) and levobupivacaine (0.125%), all in combination with sufentanil 1 microg/mL with regard to postoperative pain relief and absence of motor block in a patient-controlled epidural analgesia setting. METHODS: The study design was randomized and double-blind. Sixty-three patients scheduled for total knee replacement under combined spinal-epidural anesthesia were randomly allocated to receive ropivacaine 0.2%/sufentanil 1 microg/mL (group 1), ropivacaine 0.125%/sufentanil 1 microg/mL (group 2), or levobupivacaine 0.125%/sufentanil 1 microg/mL (group 3) for postoperative epidural pain relief. Primary endpoints were numerical rating scores for pain and patient satisfaction, motor block scores, time to first demand of the patient-controlled epidural analgesia device and average hourly consumption of local anesthetic and sufentanil. RESULTS: There were no significant differences between the 3 groups regarding numerical rating scores for pain, patient satisfaction, and motor block scores at any of the time intervals; time to first demand and average hourly sufentanil consumption were similar. Patients in group 1 used significantly more local anesthetic than patients in groups 2 and 3. CONCLUSIONS: All 3 solutions provided adequate analgesia and minimal motor block. The higher concentration of ropivacaine 0.2% was associated with a higher consumption of local anesthetic and did not result in a decrease in the consumption of sufentanil. Under the conditions of this study, patient-controlled epidural analgesia consumption of the epidural mixture was predominantly determined by sufentanil.     

Levobupivacaine-sufentanil with or without epinephrine during epidural labor analgesia

In a prospective, randomized, double-blind study, we investigated whether epinephrine increased the efficacy of levobupivacaine and sufentanil during epidural labor analgesia. Seventy term parturients received an epidural injection of levobupivacaine 0.125% and sufentanil 0.75 microg/mL with or without 1:800,000 epinephrine. After an initial dose of 10 mL, a patient-controlled analgesia pump was started. Total and hourly drug consumption, pain scores using the visual analog scale, sensory and motor block, duration of labor, vital variables, maternal and neonatal outcome, and side effects were compared. If the parturients experienced insufficient pain relief during the study, even after a rescue dose of 10 mL, they were excluded from further study and received 10 mL of bupivacaine 0.125% and sufentanil 0.75 microg/mL with 1:800,000 epinephrine. Hourly drug consumption, rescue dosing, and pain scores at 15 min and 20 min were lower in the epinephrine group. The incidence of motor block and duration of the second stage of labor tended to be higher in the epinephrine group and were associated with lower Apgar scores at 1 and 5 min. These findings suggest that the addition of epinephrine intensifies the effects of epidural levobupivacaine and sufentanil but may cause more motor block.     

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.     

硬膜外罗比卡因用于腰椎间盘摘除术的最低运动阻滞浓度

目的 确定腰椎间盘摘除术中硬膜外罗比卡因的最低运动阻滞浓度。方 法随机选择30例择期腰椎间盘摘除术的患者，用上下序贯法确定硬膜外罗比卡因的最低运动阻滞浓度，即阻滞踝关节屈曲的罗比卡因的半数有效浓度。结果 在本研究的条件下硬膜外罗比卡因的最低运动阻滞浓度为0.730％[95％可信区间：0.696％～0.733％]。结论 存在一个镇痛满意而不发生运动阻滞的罗比卡因浓度范围，本文结果有助于在相关手术中选择合适的罗比卡因浓度。     

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.