Department of Anaesthesia, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada.
Br J Anaesth. 2011 Jan;106(1):124-30. doi: 10.1093/bja/aeq306. Epub 2010 Nov 8.
Previous studies have demonstrated that lower local anaesthetic (LA) volumes can be used for ultrasound (US)-guided interscalene brachial plexus block (ISB). However, no study has examined whether US can reduce the volume required when compared with nerve stimulation (NS) for ISB. Our aim was to do this by comparing the minimum effective analgesic volumes (MEAVs).
After ethics approval and informed consent, patients undergoing shoulder surgery were recruited to this randomized, double-blind, up-down sequential allocation study. The volume used for both US and NS was dependent upon the success or failure of the previous block. Success was defined as a verbal rating score of 0/10, 30 min after surgery. Ten needle passes were allowed before defaulting to the opposite group. Patients received general anaesthesia. Pain scores and analgesic consumption were assessed by a blinded observer. Statistical comparisons of continuous variables were performed using Student's t-test and Mann-Whitney U-test as appropriate. Categorical variables were analysed using χ² test. MEAV values were estimated using log-transformed up-down independent pairs analysis and probit regression. Significance was assumed at P<0.05 (two-sided).
The MEAV required to provide effective analgesia was significantly (P=0.034) reduced to 0.9 ml [95% confidence interval (CI) 0.3-2.8] in the US group from 5.4 ml (95% CI 3.4-8.6) in the NS group. Fewer needle passes were needed to identify the brachial plexus with US (1 vs 3; P<0.0001) and patients had less pain at 30 min after surgery (P=0.03).
US reduces the number of attempts, LA volume, and postoperative pain when compared with NS for ISB.
先前的研究表明，在超声（US）引导下进行锁骨下臂丛神经阻滞（ISB）时，可以使用较低的局部麻醉剂（LA）剂量。然而，尚无研究比较 US 与神经刺激（NS）用于 ISB 时所需的 LA 体积是否更小。我们旨在通过比较最小有效镇痛体积（MEAV）来实现这一目标。
本研究经伦理委员会批准并获得患者知情同意后，纳入了拟行肩部手术的患者，采用随机、双盲、上下序贯分配研究。US 和 NS 所用的 LA 体积取决于前一次阻滞的成功或失败。成功定义为术后 30 分钟时的口述评分 0/10。如果 10 次穿刺均未成功，则转为对侧组。患者接受全身麻醉。由盲法观察者评估疼痛评分和镇痛药物消耗情况。使用学生 t 检验和 Mann-Whitney U 检验比较连续变量，使用 χ²检验比较分类变量。使用对数转换上下独立对分析和概率回归估计 MEAV 值。假设 P<0.05（双侧）具有统计学意义。
与 NS 组（5.4ml，95%置信区间 3.4-8.6）相比，US 组的有效镇痛所需 MEAV 显著降低（P=0.034）至 0.9ml（95%置信区间 0.3-2.8）。US 组识别臂丛神经所需的穿刺针数更少（1 次比 3 次；P<0.0001），术后 30 分钟时疼痛更少（P=0.03）。
与 NS 相比，US 减少了 ISB 的穿刺次数、LA 用量和术后疼痛。
