Department of Anaesthesia and Pain Management, Ulster Hospital, Dundonald, Upper Newtownards Road, Belfast BT16 1RH, UK.
Br J Anaesth. 2010 May;104(5):633-6. doi: 10.1093/bja/aeq050. Epub 2010 Mar 16.
The minimum effective volume of local anaesthetic needed to provide effective analgesia of the four main branches of the axillary brachial plexus is unknown. This study was performed to determine the minimum volume of local anaesthetic required to surround the nerves of the axillary brachial plexus and document onset and duration of sensory and motor effects.
We enrolled 19 ASA I-II patients undergoing hand or forearm surgery. The four nerves of the axillary plexus were identified with ultrasound guidance. Lidocaine 1.5% with epinephrine 1:200 000 was loaded into a syringe driver. A 22 G needle was inserted in the long axis to each nerve and injection commenced using the bolus function (600 ml h(-1)). The needle was repositioned until the nerve was completely surrounded. The bolus dose in millilitres displayed on the syringe driver was recorded. This was repeated for each nerve. The degree of sensory and motor block was recorded as secondary outcomes.
The mean (95% CI) volume to surround each nerve was: radial 3.42 (2.84-3.99) ml, median 2.75 (2.31-3.19) ml, ulnar 2.58 (2.14-3.03) ml, and musculocutaneous 2.30 (1.96-2.64) ml. The mean (95% CI) onset time for complete sensory block was: radial 22.5 (13.5-31.5) min, median 26.8 (18.5-35.0) min, ulnar 26.6 (17.8-35.4) min, and musculocutaneous 15.8 (7.45-24.2) min. The mean (95% CI) last recorded time with complete block was: radial 137.1 (105.6-168.7) min, median 144.7 (123.4-166.0) min, ulnar 183.2 (158.1-208.2) min, and musculocutaneous 158.3 (131.8-184.9) min. Seven patients required additional local anaesthetic infiltration and two required i.v. analgesia. No patient required conversion to general anaesthesia for surgery.
We found that it is possible to surround each nerve of the axillary brachial plexus with 2-4 ml of local anaesthetic. We speculate that increasing this volume would produce blocks of quicker onset and longer duration while still using smaller volumes than previously thought.
腋臂丛的四个主要分支需要的最小有效局部麻醉体积以提供有效的镇痛尚不清楚。本研究旨在确定环绕腋臂丛神经所需的最小局部麻醉量，并记录感觉和运动效果的起始和持续时间。
我们招募了 19 名接受手部或前臂手术的 ASA I-II 级患者。使用超声引导识别腋丛的四根神经。将利多卡因 1.5%加肾上腺素 1:200000 装入注射器泵。将 22G 针插入每根神经的长轴，使用推注功能（600ml/h）开始注射。将针重新定位，直到完全环绕神经。记录注射器泵上显示的推注剂量。对每个神经重复此操作。感觉和运动阻滞的程度作为次要结果进行记录。
环绕每根神经的平均（95%CI）体积分别为：桡神经 3.42（2.84-3.99）ml，正中神经 2.75（2.31-3.19）ml，尺神经 2.58（2.14-3.03）ml，肌皮神经 2.30（1.96-2.64）ml。完全感觉阻滞的平均（95%CI）起始时间分别为：桡神经 22.5（13.5-31.5）min，正中神经 26.8（18.5-35.0）min，尺神经 26.6（17.8-35.4）min，肌皮神经 15.8（7.45-24.2）min。完全阻滞的最后记录时间的平均（95%CI）分别为：桡神经 137.1（105.6-168.7）min，正中神经 144.7（123.4-166.0）min，尺神经 183.2（158.1-208.2）min，肌皮神经 158.3（131.8-184.9）min。七名患者需要额外的局部麻醉浸润，两名患者需要静脉内镇痛。没有患者需要转为全身麻醉进行手术。
我们发现，用 2-4ml 的局部麻醉剂环绕腋臂丛的每根神经是可能的。我们推测，增加这种体积会产生更快起效和更长持续时间的阻滞，同时仍然使用比以前认为的更小的体积。
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