Columb M O, Lyons G
St. James's University Hospital, Leeds, United Kingdom.
Anesth Analg. 1995 Oct;81(4):833-7. doi: 10.1097/00000539-199510000-00030.
The aim of this study was to devise a clinical model to determine the effective concentrations in 50% of patients (EC50) for bupivacaine and lidocaine in the first stage of labor and define EC50 as the minimum local analgesic concentration (MLAC). This should allow the determination of relative analgesic potency and, subsequently, the local anesthetic sparing efficacy of other epidural analgesics. Parturients not exceeding 5 cm cervical dilation who requested epidural analgesia were enrolled. The two studies involved 81 women (bupivacaine n = 41, lidocaine n = 40). After a lumbar epidural catheter was placed, 20 mL of the concentration of local anesthetic being tested was given. The concentration was determined by the response of the previous patient to a higher or lower concentration using double-blinded, up-down sequential allocation. Efficacy was assessed using 100-mm visual analog pain scores with less than 10 mm within 1 h defined as effective. MLAC was determined using the formula of Dixon and Massey. Results show MLAC bupivacaine 0.065% (95% confidence interval [CI] 0.045-0.085), MLAC lidocaine 0.37% (95% CI 0.32-0.42), equivalent to 2 and 14 mmol solutions, respectively. Thus bupivacaine was 5.7 times more potent than lidocaine in weighted and 7 times more potent in molar ratios at analgesic EC50, in the volume of local anesthetic studied.
本研究的目的是设计一种临床模型，以确定布比卡因和利多卡因在第一产程中使50%患者有效的浓度（EC50），并将EC50定义为最低局部镇痛浓度（MLAC）。这应有助于确定相对镇痛效能，进而确定其他硬膜外镇痛药的局部麻醉药节省效果。纳入了宫颈扩张不超过5cm且要求硬膜外镇痛的产妇。两项研究共涉及81名女性（布比卡因组n = 41，利多卡因组n = 40）。放置腰段硬膜外导管后，给予20mL正在测试的局部麻醉药浓度。浓度通过前一名患者对更高或更低浓度的反应，采用双盲、上下顺序分配法来确定。使用100mm视觉模拟疼痛评分评估疗效，1小时内评分低于10mm定义为有效。MLAC采用Dixon和Massey公式确定。结果显示，布比卡因的MLAC为0.065%（95%置信区间[CI] 0.045 - 0.085），利多卡因的MLAC为0.37%（95%CI 0.32 - 0.42），分别相当于2mmol和14mmol溶液。因此，在所研究的局部麻醉药体积中，在镇痛EC50时，布比卡因的效能按加权计算比利多卡因高5.7倍，按摩尔比计算高7倍。
