Department of Anesthesiology, Lapeyronie University Hospital, Route de Ganges, France.
Anesth Analg. 2010 Oct;111(4):1059-64. doi: 10.1213/ANE.0b013e3181eb6372. Epub 2010 Aug 12.
Nerve stimulation and ultrasound guidance are the most popular techniques for peripheral nerve blocks. However, the minimum effective anesthetic volume (MEAV) in selected nerves for both techniques and the consequences of decreasing the local anesthetic volume on the pharmacodynamic characteristics of nerve block remain unstudied. We designed a randomized, double-blind controlled comparison between neurostimulation and ultrasound guidance to estimate the MEAV of 1.5% mepivacaine and pharmacodynamics in median and ulnar nerve blocks.
Patients scheduled for carpal tunnel release were randomized to ultrasound guidance (UG) or neurostimulation (NS) groups. A step-up/step-down study model (Dixon method) was used to determine the MEAV with nonprobability sequential dosing based on the outcome of the previous patient. The starting dose of 1.5% mepivacaine was 13 and 11 mL for median and ulnar nerves at the humeral canal. Block success/failure resulted in a decrease/increase of 2 mL. A blinded physician assessed sensory blockade at 2-minute intervals for 20 minutes. Block onset time and duration were noted.
The MEAV50 (SD) of the median nerve was lower in the UG group 2 (0.1) mL (95% confidence interval [CI] = [1, 96] to [2, 04]) than in the NS group 4 (3.8) mL (95% CI = [2, 4] to [5, 6]) (P = 0.017). There was no difference for the ulnar nerve between UG group 2 (0.1) mL (95% CI = [1, 96] to [2, 04]) and NS group 2.4 (0.6) mL (95% CI = [2, 1] to [2, 7]). The duration of sensory blockade was significantly correlated to local anesthetic volume, but onset time was not modified.
Ultrasound guidance selectively provided a 50% reduction in the MEAV of mepivacaine 1.5% for median nerve sensory blockade in comparison with neurostimulation. Decreasing the local anesthetic volume can decrease sensory block duration but not onset time.
神经刺激和超声引导是外周神经阻滞最常用的技术。然而，这两种技术在选定神经中的最小有效麻醉量（MEAV）以及减少局部麻醉量对神经阻滞药效学特征的影响仍有待研究。我们设计了一项随机、双盲对照研究，比较神经刺激和超声引导，以估计 1.5%甲哌卡因在正中神经和尺神经阻滞中的 MEAV 和药效学。
拟行腕管松解术的患者被随机分为超声引导（UG）或神经刺激（NS）组。采用逐步递增/递减研究模型（Dixon 法），根据前一位患者的结果，基于概率序贯给药来确定 MEAV。正中神经在肱骨管内的起始剂量为 1.5%甲哌卡因 13 和 11 mL，尺神经为 11 和 9 mL。阻滞成功/失败导致 2 mL 的减少/增加。一位盲法医师每 2 分钟评估一次感觉阻滞，共 20 分钟。记录阻滞起效时间和持续时间。
UG 组的 MEAV50（SD）为 2（0.1）mL（95%置信区间 [CI]：[1, 96]至 [2, 04]），明显低于 NS 组的 4（3.8）mL（95% CI：[2, 4]至 [5, 6]）（P = 0.017）。在 UG 组和 NS 组 2 中，尺神经的 MEAV50 没有差异，分别为 2（0.1）mL（95% CI：[1, 96]至 [2, 04]）和 2.4（0.6）mL（95% CI：[2, 1]至 [2, 7]）。感觉阻滞的持续时间与局部麻醉量显著相关，但起效时间没有改变。
与神经刺激相比，超声引导选择性地将 1.5%甲哌卡因用于正中神经感觉阻滞的 MEAV 降低了 50%。减少局部麻醉量可以缩短感觉阻滞持续时间，但不能改变起效时间。
