Cappelleri Gianluca, Ambrosoli Andrea Luigi, Turconi Stefania, Gemma Marco, Ricci Erika Basso, Cornaggia Gabriele
From the Department of Anesthesia, Azienda Ospedaliera Istituto Ortopedico Gaetano Pini, Milano; Department of Anesthesia, Ospedale di Circolo Varese, Varese; and Department of Anesthesia, Irccs San Raffaele, Milano, Italy.
Anesth Analg. 2014 Aug;119(2):489-493. doi: 10.1213/ANE.0000000000000293.
Among the various factors influencing the success rate, onset time, and duration of peripheral nerve blocks, the role of local anesthetics concentration remains uncertain. In this prospective, randomized, single-blinded study, we evaluated whether varying the dilution of a fixed dose of mepivacaine solution influenced onset time and duration of sciatic nerve block.
Ninety ASA physical status I to II patients scheduled for foot surgery were randomly allocated to receive a double-injection Labat sciatic nerve block with 12 mL mepivacaine 2% (group concentration I = 45 patients) or 24 mL of mepivacaine 1% (group volume II = 45 patients). The nerve stimulator was initially set at 2 Hz, 0.1 millisecond, 1 mA. The total amount of local anesthetic (240 mg) was kept constant and equally divided between the peroneal and tibial nerves. All patients also received an ultrasound-guided popliteal sciatic nerve catheter for postoperative analgesia. Times to readiness for surgery, performance, and offset of local anesthetic were recorded. Our primary end point was to determine a possible difference in offset time between groups. Continuous variables were expressed as median (IQR) and compared with the Wilcoxon-Mann-Whitney U test; WMWodds are reported together with their 95% confidence interval.
The overall success rate of sciatic nerve block was 99%. Time of performance was shorter in group I, 120 seconds (90-150 seconds), than that in group II, 150 seconds (120-180 seconds) (P = 0.0048; WMWodds 2.26 [1.35-4.34]). The onset time of sensory and motor sciatic nerve block was 4 minutes (2-9 minutes) in group I and 6 minutes (4-10 minutes) in group II (P = 0.41; WMWodds 1.21 [0.77-1.95]), while the duration of sensory block was 235 minutes (203-250 minutes) in group I, and 240 minutes (218-247 minutes) in group II respectively (P = 0.51; WMWodds 1.20 [0.69-2.16]).
We found no evidence that varying volume and concentration while maintaining a fixed total dose of mepivacaine alters the onset time and duration of double-injection sciatic nerve block. Considering our WMWodds results, possible differences in onset time and duration comparable to differences in the performance time between groups cannot be excluded.
在影响周围神经阻滞成功率、起效时间和持续时间的各种因素中，局部麻醉药浓度的作用仍不确定。在这项前瞻性、随机、单盲研究中，我们评估了改变固定剂量甲哌卡因溶液的稀释度是否会影响坐骨神经阻滞的起效时间和持续时间。
90例计划行足部手术的ASA身体状况I至II级患者被随机分配接受双注射Labat坐骨神经阻滞，其中一组注射12 mL 2%甲哌卡因（浓度I组 = 45例患者），另一组注射24 mL 1%甲哌卡因（容量II组 = 45例患者）。神经刺激器最初设置为2 Hz、0.1毫秒、1 mA。局部麻醉药的总量（240 mg）保持恒定，并在腓总神经和胫神经之间平均分配。所有患者还接受超声引导下的腘窝坐骨神经导管用于术后镇痛。记录手术准备就绪时间、操作时间和局部麻醉药消退时间。我们的主要终点是确定两组之间消退时间的可能差异。连续变量以中位数（IQR）表示，并采用Wilcoxon-Mann-Whitney U检验进行比较；报告WMW比值及其95%置信区间。
坐骨神经阻滞的总体成功率为99%。I组的操作时间较短，为120秒（90 - 150秒），短于II组的150秒（120 - 180秒）（P = 0.0048；WMW比值2.26 [1.35 - 4.34]）。I组感觉和运动坐骨神经阻滞的起效时间为4分钟（2 - 9分钟），II组为6分钟（4 - 10分钟）（P = 0.41；WMW比值1.21 [0.77 - 1.95]），而感觉阻滞的持续时间I组为235分钟（203 - 250分钟），II组为240分钟（218 - 247分钟）（P = 0.51；WMW比值1.20 [0.69 - 2.16]）。
我们没有发现证据表明在维持甲哌卡因总剂量固定的情况下改变容量和浓度会改变双注射坐骨神经阻滞的起效时间和持续时间。考虑到我们的WMW比值结果，不能排除起效时间和持续时间的可能差异与两组之间操作时间的差异相当。
