罗比卡因及复合芬太尼硬膜外麻醉对运动阻滞EC_(50)的影响

Comparison of theEC_(50)of epidurial ropivacaine only and combining with fentanyl for motor-block

目的测定罗比卡因单独使用以及复合不同浓度芬太尼用于硬膜外麻醉时,分别产生运动阻滞的半数有效浓度(effective concentration in 50%patients,EC50),从而确定硬膜外使用芬太尼对罗比卡因硬膜外麻醉产生运动阻滞效果的影响.方法选择ASA Ⅰ～Ⅱ级下肢及肛周会阴部择期手术患者165例,随机分为五组,每组33人.选择L2～3或L3～4硬膜外穿刺,头向置管4 cm成功后,以5 ml/min的速度向硬膜外腔缓慢注入15 ml配置好的药液,Ⅰ组:单纯罗比卡因;Ⅱ组:罗比卡因复合1μg/ml芬太尼;Ⅲ组:罗比卡因复合2μg/ml芬太尼;Ⅳ组:罗比卡因复合3μg/ml芬太尼;Ⅴ组:罗比卡因复合4μg/ml芬太尼.各组中第1位患者向硬膜外腔注入的罗比卡因浓度均为0.425%,其后各患者所用浓度按序贯法进行调整,浓度变化梯度定为0.025%.改良Bromage评分等于4分者为无效运动阻滞,低于4分时为有效运动阻滞.根据Dixon和Massey法[1]计算各组运动阻滞的EC50值.结果五组入选患者中,12例结果显示可疑而退出,根据实际进入的153例,Ⅱ～Ⅴ组罗比卡因运动阻滞EC50值与Ⅰ组比较,均无显著性差异.结论罗比卡因复合低浓度芬太尼(0～4μg/ml)用于硬膜外麻醉时,对罗比卡因产生运动阻滞的EC50无明显影响.

Objective To determine the motor block effective concentrations in 50% of patients （EC50） of epidural ropivacaine alone or combining with fentanyl in lower limb surgery and whether fentanyl decreases the concentration of epidural ropivacaine for motor-block. Methods In this randomized, study, 165 patients planning to apply lower limb or perianal surgery, were enrolled and allocated to one of five study groups（n= 33）. After L2-3 or L3-4 epidural catheter placement 4 cm cephalad, each participant received a 15 ml bolus of ropivacaine , ropivacaine with fentanyl 1 μg/ml, ropivacaine with fentanyl 2 μg/ml,ropivacaine with fentanyl 3 μg/ml, or ropivacaine with fentanyl 4 μg/ml. The concentration of ropivacaine was determined by the response of the previous patient to a higher or lower concentration using up-down sequential allocation. The first participants received 0.425%. Effective motor block was defined as a modified Bromage score 〈 4 within 30 minutes. An effective result directed a 0.025% decrement for the next patient. An ineffective result directed a 0.025% increment. The up-down sequences were analyzed using the Dixon and Massey method and probit regression to quantify the motor block minimal local analgesic concentration. Results Among 165 patients enrolled, 12 were excluded. The motor block EC50 of ropivacaine alone was 0.416% （95% CI, 0.410%-0. 421%）. The addition of fentanyl at the doses of 1 μg/ml, 2 μg/ml, 3 μg/ml and 4 μg/ml resulted in no significant reductions （P〉0.05）. Conclusions This study showed no significant （P〉0.05） dosedependent reduction in the motor-block EC50 of ropivacaine by fentanyl.