Leeds Institute of Molecular Medicine, University of Leeds, UK.
Br J Anaesth. 2010 Apr;104(4):490-5. doi: 10.1093/bja/aeq017. Epub 2010 Feb 18.
The aim of this study was to determine whether the ED(50) dose of bupivacaine 0.5% for supraclavicular brachial plexus block increases with increasing body mass index (BMI).
This double-blind, non-randomized trial followed an up-and-down sequential allocation design. Adult patients undergoing elective upper limb surgery under ultrasound-guided supraclavicular brachial block were recruited. A preliminary study was used to guide the dosing schedule for the main study in which patients were divided into three groups according to their BMI (Group A, BMI >27 kg m(-2); Group B, BMI 24-27 kg m(-2); Group C, BMI <24 kg m(-2)). The study design and analysis followed Dixon's small sample model using a 'nominal' sample size of six per group.
Twenty-one patients were recruited to the preliminary study. Using isotonic regression, the ED(50) for bupivacaine 0.5% was estimated to be 8.9 ml [95% confidence interval (CI) 7.8-15.9]. In comparison, the ED(50) volume was found to be 10.8 ml (95% CI 5.9-19.7) using the Dixon-Massey formula. In the main study, six patients were recruited in each group with mean (range) BMI of 31.5 (27.2-38.8) kg m(-2) in Group A, 25.6 (24.4-26.3) kg m(-2) in Group B, and 21.6 (19.7-23.8) kg m(-2) in Group C. The ED(50) (95% CI) for Groups A, B, and C were 8.9 (6.2-12.7), 10.7 (7.5-15.4), and 13.4 (9.3-19.1) ml, respectively (P=0.05 for Group A vs Group C).
Our study demonstrates that the ED(50) of bupivacaine 0.5% does not increase with an increase in BMI. We found evidence of a possible inverse relationship between ED(50) and BMI.
本研究旨在确定 0.5%布比卡因用于锁骨上臂丛阻滞的 ED（50）剂量是否随体重指数（BMI）的增加而增加。
这是一项双盲、非随机试验，采用上下序贯分配设计。招募接受超声引导锁骨上臂丛阻滞下择期上肢手术的成年患者。初步研究用于指导主要研究的剂量方案，根据 BMI 将患者分为三组（A 组，BMI>27kg/m（2）；B 组，BMI 24-27kg/m（2）；C 组，BMI<24kg/m（2））。研究设计和分析遵循 Dixon 的小样本模型，每组名义样本量为 6 例。
初步研究共纳入 21 例患者。使用等渗回归，估计 0.5%布比卡因的 ED（50）为 8.9ml[95%置信区间（CI）7.8-15.9]。相比之下，Dixon-Massey 公式显示 ED（50）体积为 10.8ml（95%CI5.9-19.7）。在主要研究中，每组招募 6 例患者，A 组平均（范围）BMI 为 31.5（27.2-38.8）kg/m（2），B 组为 25.6（24.4-26.3）kg/m（2），C 组为 21.6（19.7-23.8）kg/m（2）。A、B 和 C 组的 ED（50）（95%CI）分别为 8.9（6.2-12.7）、10.7（7.5-15.4）和 13.4（9.3-19.1）ml，A 组与 C 组比较差异有统计学意义（P=0.05）。
本研究表明，0.5%布比卡因的 ED（50）剂量不会随 BMI 的增加而增加。我们发现 ED（50）与 BMI 之间可能存在反比关系。
