右美托咪定对老年患者罗哌卡因胸椎旁阻滞半数有效浓度的影响

目的 评价右美托咪定(dexmedetomidine,Dex)对老年患者超声引导下胸椎旁阻滞罗哌卡因半数有效浓度(median effective concentration,EC50)的影响. 方法 选择胸腔镜下行肺叶切除术老年患者60例,年龄65 ～79岁,ASA分级Ⅱ、Ⅲ级,拟在超声引导下行胸椎旁阻滞.采用随机数字法分为两组(每组30例):对照组(C组)和Dex组(D组).C组神经阻滞用药仅为罗哌卡因;D组神经阻滞用药为罗哌卡因和0.75 μg/kg Dex的混合液.罗哌卡因初始浓度为0.5％,相邻浓度比值为1.2,若阻滞效果评定为优良,则下一例采用低一级浓度;若阻滞效果评定为差,则下一例采用高一级浓度.采用Probit概率单位回归法计算两组罗哌卡因胸椎旁阻滞的EC50及其95％置信区间(confidence interval,CI). 结果 C组超声引导下罗哌卡因的EC50为0.42％,95％C1为0.40％～0.45％;Dex组罗哌卡因的EC50为0.35％,95％CI为0.32％～0.37％. 结论 Dex可降低罗哌卡因椎旁阻滞的EC50.

Effect of dexmedetomidine on the medium effective concentration of ropivacaine for thoracic paravertebral block in aged patients

Objective To investigate effect of dexmedetomidine (Dex) on the medium effective concentration (EC50) of ropivacaine for ultrasound-guided thoracic paravertebral block.Methods Sixty ASA Ⅱ or Ⅲ patients,aged 65-79 y,scheduled for lobectomy under video-assisted thoracoscopic surgery,requiring ultrasound-guided thoracic paravertebral block,were randomly assigned into 2 groups (n=30):control group (group C) and Dex group (group D).Paravertebral block was performed by using only ropivacaine in group C.In group D the mixture of ropivacaiue and 0.75 μg/kg Dex was injected for the block.The initial concentration of ropivacaine was 0.5％ and the ratio between the two successive concentrations was 1.2.If the block was effective,the next patient received a lower dose of ropivacaine,or if ineffective,a higher dose was given to the next patient.The EC50 and 95％ confidence interval (C/) of ropivacaine were determined by using probit regression method.Results The EC50 of ropivacaine was 0.42％ and 95％CI was 0.40％-0.45％ in group C,The EC50 of ropivacaine was 0.35％ and 95％CI was 0.32％-0.37％ in group D.Conclusions The combined use of Dex can decrease the EC50 of ropivacaine for ultrasound-guided thoracic paravertebral block.