The interscalene brachial plexus block is recommended for analgesia after shoulder surgery but it may cause hemidiaphragmatic dysfunction. We tested whether ipsilateral hemidiaphragmatic contraction was better after a smaller dose of local anaesthetic without impairing analgesic effect. We randomly allocated 48 adults to 10 ml or 20 ml levobupivacaine 0.25% before arthroscopic shoulder surgery. The primary outcome was hemidiaphragmatic paralysis, defined as inspiratory thickness < 1.2 times expiratory thickness, measured by ultrasound 4 h after block. Hemidiaphragmatic paralysis was recorded for 6/24 vs. 23/24 supine participants after 10 ml vs. 20 ml levobupivacaine 0.25%, respectively, and for 4/24 vs. 23/24 sitting participants, respectively, p < 0.001 for both. Pain scores after 10 ml injectate were not worse than after 20 ml injectate. Median (IQR [range]) morphine doses in the first 24 postoperative hours after 10 ml and 20 ml levobupivacaine 0.25% were 2 (0–6 [0–23]) mg vs. 1 (0–2 [0–11]) mg, respectively, p = 0.12. No participant had a complication after 10 ml interscalene levobupivacaine, whereas seven had complications after 20 ml levobupivacaine, p = 0.009. Hemidiaphragmatic function was better after 10 ml vs. 20 ml interscalene levobupivacaine 0.25% without impairing analgesia for 24 postoperative hours.

中文翻译：

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在接受关节镜肩部手术的患者中进行的一项随机对照试验，比较了肌间沟阻滞与 10 毫升或 20 毫升左布比卡因 0.25%

肩部手术后建议使用肌间沟臂丛神经阻滞进行镇痛，但可能会导致膈肌功能障碍。我们测试了在不影响镇痛效果的情况下，在较小剂量的局麻药后同侧膈肌收缩是否更好。在肩关节镜手术前，我们将 48 名成人随机分配至 10 毫升或 20 毫升 0.25% 的左布比卡因。主要结果是膈肌麻痹，定义为吸气厚度 < 1.2 倍呼气厚度，在阻滞后 4 小时通过超声测量。分别在 10 毫升和 20 毫升 0.25% 的左布比卡因和 4/24 和 23/24 坐着的参与者分别记录了 6/24 和 23/24 仰卧位参与者的膈肌麻痹，两者的 p < 0.001。注射 10 毫升后的疼痛评分并不比注射 20 毫升后差。10 ml 和 20 ml 左布比卡因 0.25% 术后最初 24 小时的吗啡剂量中位数（IQR [范围]）分别为 2 (0-6 [0-23]) mg 对 1 (0-2 [0-11])毫克，分别，p = 0.12。没有参与者在服用 10 ml 左旋布比卡因后出现并发症，而 7 名参与者在服用 20 ml 左布比卡因后出现并发症，p = 0.009。10 毫升与 20 毫升 0.25% 左旋布比卡因肌间肌间隙相比，膈肌功能更好，术后 24 小时不影响镇痛。