静脉输注右美托咪定对罗哌卡因骶管阻滞半数有效浓度的影响

Effect of intravenous dexmedetomidine on median effective concentration of ropivacaine for caudal block

摘要:

目的 骶管阻滞具有操作简单、损伤小、起效快和麻醉效果明确等特点，是儿童和成人接受下肢、泌尿系统或肛肠手术的常用麻醉方法。静脉输注右美托咪定（intravenous dexmedetomidine，IV-DEX）是区域麻醉过程中常用的镇静方法，显示了其对局麻药的协同作用。本研究的目的是验证IV-DEX是否会降低局麻药骶管阻滞的半数有效浓度（median effective concentration，EC₅₀）。方法 纳入60例计划行择期痔切除术的患者，分为2组，静脉输注生理盐水组（intravenous-normal saline，IV-NS组）和IV-DEX组。IV-NS组和IV-DEX组分别在骶管阻滞前15 min静脉输注20 mL生理盐水和1 μg/kg右美托咪定（生理盐水稀释至20 mL）。采用Dixon-Massey“上下”顺序分配法确定罗哌卡因骶管阻滞的EC₅₀。记录患者术中生命体征，需要药物处理的低血压、心动过缓和术中其他不良反应发生情况。结果 IV-NS组罗哌卡因骶管阻滞的EC₅₀为0.280%，IV-DEX组为0.233%（P<0.05）。与IV-NS组相比，IV-DEX组中罗哌卡因的EC₅₀降低16.8%（P=0.000），具有统计学差异。2组间需要药物治疗的低血压、心动过缓和术中其他不良反应发生率无统计学差异。结论 IV-DEX可以降低罗哌卡因骶管阻滞的EC₅₀，但IV-DEX可能导致低血压、心动过缓的发生率增加。因此，IV-DEX与局麻药协同作用的最佳剂量仍需要进一步探索。

Abstract:

Objective Caudal block，characterized by simple operation，small injury，rapid onset and definite anesthetic effect，is a common anesthesia method for children and adults undergoing lower extremity，urinary system or anorectal surgery. Intravenous dexmedetomidine（IV-DEX） is a commonly used sedative method during regional anesthesia，but it also shows synergistic effect on local anesthetics. This study aims to examine whether IV-DEX reduces the median effective concentration（EC₅₀） of local anesthetics for caudal block.Methods Sixty patients scheduled for elective hemorrhoidectomy were enrolled in the study and divided into intravenous-normal saline（IV-NS） group and IV-DEX group. In IV-NS group and IV-DEX group，20 mL saline and 1 μg/kg dexmedetomidine （diluted to 20 mL） were intravenously infused 15 min before caudal block， respectively. The EC₅₀ of ropivacaine for caudal block was determined by Dixon-Massey “up and down” sequential assignment method. Vital signs，hypotension， bradycardia，and other intraoperative adverse events requiring medical treatment were recorded.Results The EC₅₀ of ropivacaine for caudal block in IV-NS group was 0.280%，and that in IV-DEX group was 0.233%（P<0.05）. Compared with the IV-NS group，the EC₅₀ of ropivacaine in the IV-DEX group was decreased by 16.8%（P=0.000），and the difference was statistically significant. The incidence of hypotension，bradycardia，and other adverse events requiring medical treatment had no difference between the two groups.Conclusion IV-DEX can reduce the EC₅₀ of ropivacaine for caudal block，but it may lead to an increase in the incidence of hypotension and bradycardia. Therefore，the optimal synergistic dose of IV-DEX with local anesthetics still needs to be further explored.