右美托咪啶对罗哌卡因臂丛神经阻滞半数有效浓度的影响

摘要

目的 探讨右美托咪啶对罗哌卡因臂丛神经阻滞半数有效浓度( median effective concentration,EC50)的影响.方法 择期臂丛神经阻滞的上肢手术患者60例,年龄20~55岁,体质量50~75kg,ASA 分级Ⅰ或Ⅱ级.采用随机数字表法将其分为罗哌卡因(ropivacaine,R)组(n=30)和罗哌卡因混合右美托咪啶(ropivacaine+dexmedetomidine,RD)组(n=30).采用肌间沟臂丛阻滞法,定位成功后,R组和RD组分别注入罗哌卡因和罗哌卡因混合1μg/kg右美托咪均40mL.R组和RD组第1例患者罗哌卡因浓度分别为0.38%、0.28%,按序贯法确定下1例患者罗哌卡因的浓度,若上1例患者麻醉有效,则下1例患者罗哌卡因的浓度降低1个浓度梯度,若麻醉无效,则下1例患者增加1个浓度梯度,罗哌卡因的浓度梯度为0.02%.采用概率单位(Probit)法计算罗哌卡因半数有效浓度(median effective concentration,EC50)及其95%可信区间(95% confidence interval,95 %CI).记录患者麻醉前,麻醉后5、10和20min平均动脉压(mean artery pressure,MAP)、心率(heart rate,HR)、血氧饱和度(oxygen saturation,SpO2)、Ramsay评分.记录有关不良反应的发生情况.结果 R组和RD组罗哌卡因的EC50及95%CI分为0.32(0.27~0.37)%和0.20(0.16~0.24)%(P＜0.05).与R组及麻醉前比较,RD组在麻醉后10~20min MAP和HR降低,Ramsay评分升高(P＜0.05).SpO2和不良反应发生率比较差异无统计学意义(P＞0.05).结论 右美托咪啶可降低罗哌卡因臂丛神经阻滞EC50,增加镇静评分,且血流动力学稳定.%Objective To investigate the effect of dexmedetomidine on median effective concentration( EC50 ) of ropivacaine for brachial plexus block. Methods Sixty ASA I or H patients aged 20 ~55year,weighing 50 ~75kg,scheduled for upper extremity surgery under brachial plexus block were randomly divided into 2 groups( n =30 each ): ropivacaine group( group R ) and ropivacaine combind with dexmedetomidine group( group RD ). After successful location, ropivacaine 40 mL and ropivacaine combind with dexmedetomidine 40mL were injected in group R and group RD. The initial ropivacaine concentration was set at 0. 38% ,0. 28% in group R and group RD respectively. The concentration of ropivacaine was determined by up - and - down sequential allocation, each time the concentration of ropivacainernincreased/decreased by 0. 02%. The EC50 of ropicacaine and 95% confidence interval ( 95% CI ) were calculated using Probit analysis. Mean artery pressure ( MAP ), heart rate ( HR ), oxygen saturation ( SpO2 ),Ramsay score and adverse events were recorded. Results The EC50 and 95% CI of ropivacain was 0. 32( 0. 27 ~0. 37 )% and 0. 20( 0.16 ~0. 24 )% in group R and group RD( P <0. 05 ). Compared with group R and baseline, MAP and HR were decreased, Ramsay scores was increased at post anaesthetic 10 ~20min in group RD. There was no significant difference between the two groups in SpO2 and adverse events( P >0. 05 ). Conclusion Dexmedetomidine can significantly decreases the EC50 of ropivacaine, increase sedation score and stable hemodynamics.