Objective:To examine thepredominant mechanism of action of comparing the effects of epidural and venous sufentanil 7.5 μg on the median effective dose (ED50) of intrathecally administered ropivacaine for gynecology operating. Methods: In this study ED50 was determined by up-downsequential allocation. A total of 90. American Society of Anesthesiologists(ASA) classification Ⅰ or Ⅱ patients aged 20-60yr undergoing panhysterectomy with a combined spinal - epidural technique received varying doses of 0. 5％ ropivacaine alone (Group Ⅰ ) or co-administered with venous sufentanil 7.5 μg group (Group Ⅱ ) or epidural sufentanil 7.5 μg group (Group Ⅲ ). The initial dose was 20 mg. Each time the dose increased/decreased by 1 mg. Efficacy was determined by the level of sensory block was T6 and the motor block (Bromage scale = 3) in both lower limbs within 15 min after the spinal injection. The ED50 with 95％ CI of ropivacaine was estimated by the up-down reversals and by probit regression. Results: The ED50 of ropivacaine was 20.2mg(95％CI: 18.1 - 23.0) in Group Ⅰ , 17. 1 mg(95％CI: 15.0 - 19.2) in Group Ⅱ ,13.5 mg(95％ CI: 11.5 - 15.1) in Group Ⅲ. Group Ⅲ and Group Ⅱ ratio of ED50 was 0. 7885(95％CI:0. 4007 - 0. 9659). The ratio was defined as relative median potency, not included 1 ,which meaned the ED50 in Group Ⅲ lower as compared with the Group Ⅱ. Group Ⅲ and Group Ⅰ ratio of ED50 was 0. 6678(95％CI:0. 2248 - 0. 9006), which meaned the ED50 in Group Ⅲ lower as compared with the Group Ⅰ. Group Ⅱ and Group Ⅰ ratio of ED50 was 0. 8649 (95％ CI:0. 5265 - 0. 9934), which meaned the ED50 in Group Ⅱ lower as compared with the Group Ⅰ . Conclusions: Compared with an equal dose of sufentanil venous, epidurally administered sufentanil 7.5 μg co-administered with intrathecal ropivacaine has a significant local anaestheticsparing effect via a predominantly spinal mechanism for panhysterectomy.%目的:通过观察在腰麻联合硬膜外麻醉中硬膜外注射舒芬太尼是否影响罗哌卡因腰麻的半数有效剂量来分析硬膜外舒芬太尼的作用机制.方法:90例美国麻醉医师协会(ASA)分级为Ⅰ～Ⅱ级,择期行全子宫切除术的患者,随机分为3组.患者行腰麻联合硬膜外麻醉,将等比重0.5%罗哌卡因注入蛛网膜下腔.患者改为平卧位后,3组患者分别于静脉和硬膜外随机注入3 mL液体,Ⅰ组:静脉0.9%氯化钠液+硬膜外0.9%氯化钠液;Ⅱ组:静脉舒芬太尼7.5 μg+硬膜外0.9%氯化钠液;Ⅲ组:静脉0.9%氯化钠液+硬膜外舒芬太尼7.5 μg.采用序贯法进行试验,每组第1例患者罗哌卡因剂量均为20 mg,剂量变化梯度为1 mg.感觉阻滞有效定义为15 min内感觉无痛平面达到T6、Bromage评分达3分.若上1例有效,下1例剂量减低1 mg;如无效,则下1例剂量增加1 mg.半数有效剂量(ED50)及其95%可信区间(95%CI)采用Probit(概率单位回归)计算.组间比较采用中位数法比较.结果:罗哌卡因的ED50在Ⅰ组中是20.2 mg(95%CI:18.1～23.0 mg),Ⅱ组中是17.1 mg(95%CI:15.0～19.2 mg),Ⅲ组中是13.5 mg(95%CI:11.5～15.1 mg).罗哌卡因ED50 Ⅲ组/Ⅱ组是0.7885(95%CI:0.4007～0.9659),相对中位数潜力值<1,2组结果有显著差异,表示Ⅲ组的ED50<Ⅱ组的ED50.罗哌卡因ED50Ⅲ组/Ⅰ组是0.6678(95%CI:0.2248～0.9006),Ⅲ组ED50<Ⅰ组ED50.ED50Ⅱ组/Ⅰ组是0.8649(95%CI:0.5265～0.9934),Ⅱ组ED50<Ⅰ组ED50.结论:与静脉注射舒芬太尼相比,硬膜外舒芬太尼7.5 μg能显著降低罗哌卡因腰麻的ED50,因此硬膜外舒芬太尼的作用部位主要在脊髓水平.
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