右美托咪定对患者膝关节腔注射罗哌卡因镇痛ED_(50)的影响

Minimum effective local anesthetic dose of intra-articular ropivacaine with dexmedetomidine for analgesia in patients undergoing knee arthroscopy

目的：观察右美托咪定对罗哌卡因膝关节腔注射用于老年患者膝关节镜术后镇痛ED50的影响。方法选择择期行膝关节镜诊治术老年患者72例,男35例,女37例,年龄60~75岁, ASA Ⅰ或Ⅱ级。随机分为罗哌卡因组（R 组）和右美托咪定复合罗哌卡因组（DR 组）,每组36例。R组患者膝关节腔内注射不同浓度罗哌卡因；DR 组患者关节腔内注射不同浓度罗哌卡因和右美托咪定1μg/kg 的混合液。术后2 h VAS 评分低于3分为镇痛有效。采用序贯法确定罗哌卡因浓度,初始浓度为0.15%,相邻浓度比值为1.1,镇痛有效则下一例采用低一级浓度,镇痛无效则下一例采用高一级浓度。采用 Dixon-Massey 法确定 ED50及其95%CI。记录术前5 min（T0）、术后1 h（T1）、2 h （T2）、3 h（T3）、6 h（T4）、12 h（T5）、24 h（T6）和48 h（T7）患者 BP 和 HR,并对患者进行改良的 OAA/S 评分和 VAS 评分。结果术前和术后各时点两组患者 BP、HR、VAS 评分和 OAA/S 评分差异均无统计学意义。C 组 ED50为0.31%（95%CI 0.30%~0.32%）；DR 组 ED50为0.14%（95%CI 0.14%~0.15%）。结论右美托咪定可增强罗哌卡因膝关节腔注射用于患者膝关节镜术后镇痛的效果,并可减少罗哌卡因的用药剂量。

Objective To observe the minimum effective local anesthetic dose of intra-articular ropivacaine with dexmedetomidine for analgesia after knee arthroscopy in patients.Methods Seventy-two patients （35 males,37 females,aged 60-75 years,ASA grade Ⅰ or Ⅱ）undergoing knee arthro-scopy under total intravenous anesthesia were randomly divided into two groups （n =36 each）：ropiv-acaine group （group R）and ropivacaine with dexmedetomidine group （group DR）;Ropivacaine was injected intra-articularly in group C,and dexmedetomidine 1 μg/kg with ropivacaine was injected intra-articularly in group DR.ED50 of ropivacaine was determined by the sequence method.VAS score3 two hours after operation was rated as effective.The initial dose was 3 mg and according to the effective or ineffective results in previous patient,a dose of ropivacaine was decreased or increased 1.1 times to the previous patient.BP,HR,VAS Score,and OAA/S score were recorded five minutes preoperatively（T0 ）,1 h （T1 ）,2 h （T2 ）,3 h （T3 ）,6 h （T4 ）,12 h （T5 ）,24 h （T6 ）,and 48 h （T7 ） after operation in two groups.Results There was no significant difference between the two groups with regard to the BP,HR,VAS Score,and OAA/S score.ED50 of ropivacaine for analgesia after knee arthroscopy was 0.31% （95%CI 0.30%-0.32%）,and ED50 of ropivacaine with dexmedetomi-dine for analgesia after knee arthroscopy was 0.14% （95% CI 0.14%-0.1 5%）. Conclusion Intra-articular administration of ropivacaine with dexmedetomidine could provide superior postoperative analgesia.The dose of ropivacaine for analgesia after knee arthroscopy should be reduced when combined with dexmedetomidine in patients.