右美托咪定对罗哌卡因收肌管内隐神经阻滞半数有效浓度的影响

Effect of dexmedetomidine on the median effective concentration of ropivacaine for adductor canal block

目的探讨复合右美托咪定对收肌管内隐神经阻滞罗哌卡因半数有效浓度(EC 50)的影响。方法择期行全膝关节置换术患者54例,男29例,女25例,年龄53~76岁,ASAⅠ或Ⅱ级,随机分为两组:对照组(C组)和右美托咪定组(D组)。C组仅应用罗哌卡因溶液行收肌管内隐神经阻滞;D组收肌管内隐神经阻滞用药为含右美托咪定1μg/kg的罗哌卡因混合溶液。采用序贯法确定罗哌卡因的浓度,初始浓度为0.5%,相邻浓度之比为1∶1.2,注药后30 min隐神经支配区域感觉阻滞完全为阳性反应,下一例患者则采用低一级的浓度,反之则采用高一级的浓度。应用概率单位法计算罗哌卡因用于收肌管内隐神经阻滞的EC 50及其95%可信区间(CI)。结果C组和D组罗哌卡因EC 50分别为0.38%(95%CI 0.36%~0.41%)和0.29%(95%CI 0.28%~0.31%),且D组明显低于C组(P<0.05)。结论复合右美托咪定1μg/kg可降低收肌管内隐神经阻滞罗哌卡因的EC 50。

Objective To investigate the effect of combination of dexmedetomidine on the median effective concentration(EC 50)of ropivacaine for saphenous nerve block in adductor canal.Methods Fifty-four patients undergoing total knee arthroplasty,29 males and 25 females,aged 53-76 years,ASA physical statusⅠorⅡ,were divided into two groups:control group(group C)and dexmedetomidine group(group D).Saphenous nerve block in adductor canal was performed using only ropivacaine in group C.The mixture of ropivacaine and dexmedetomidine 1μg/kg was used for saphenous nerve block in adductor canal in group D.The EC 50 of ropivacaine was determined by up and down sequential trial.The initial concentration of ropivacaine was set at 0.5%,and the ratio between the two successive concentration was 1∶1.2.Each time the concentration increased or decreased in the next patient according to whether or not the sensory block was complete at 0.5 h after injected ropivacaine.The probability unit method was used to determine the EC 50 and 95%confidence interval(CI)of ropivacaine for saphenous nerve block in adductor canal.Results The EC 50 and 95%CI of ropivacaine for ultrasound-guided saphenous nerve block in adductor canal was 0.38%(95%CI 0.36%-0.41%)in group C and 0.29%(95%CI 0.28%-0.31%)in group D.The EC 50 of ropivacaine for ultrasound-guided saphenous nerve block in adductor canal was lower in group D than in group C(P<0.05).Conclusion The EC 50 of ropivacaine could be decreased by the combination of dexmedetomidine for saphenous nerve block in adductor canal.