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

EFFECT OF DEXMEDETOMIDINE ON MEDIAN EFFECTIVE CONCENTRATION OF ROPIVACAINE FOR BRACHIAL PLEXUS BLOCK

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,EC_(50))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 coneentration,EC_(50))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(oxygensaturation,SpO_2)、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EC_(50)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10～20minMAF和HR降低,Ramsay评分升高(P<0.05)。SpO_2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EC_(50)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 ropivaeaine for brachial plexus block. Methods Sixty ASA Ⅰ or Ⅱ 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 40mL 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 ropivaeaine increased/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.