Ki Jinn Chin, Javier E Cubillos, Husni Alakkad

Regional anaesthesia comprising axillary block of the brachial plexus is a common anaesthetic technique for distal upper limb surgery. This is an update of a review first published in 2006 and previously updated in 2011 and 2013. To compare the relative effects (benefits and harms) of three injection techniques (single, double and multiple) of axillary block of the brachial plexus for distal upper extremity surgery. We considered these effects primarily in terms of anaesthetic effectiveness; the complication rate (neurological and vascular); and pain and discomfort caused by performance of the block. We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 3), MEDLINE (1946 to April Week 1 2016), Embase (1947 to April 18 2016) and reference lists of trials. We contacted trial authors. The date of the last search was April 2016 (updated from March 2013). We included randomized controlled trials that compared double with single-injection techniques, multiple with single-injection techniques, or multiple with double-injection techniques for axillary block in adults undergoing surgery of the distal upper limb. We excluded trials using ultrasound-guided techniques. Independent study selection, 'Risk of bias' assessment and data extraction were performed by at least two investigators. We undertook meta-analysis. We included one new trial involving 45 participants in this updated review. In total we included 22 trials involving a total of 2193 participants who received regional anaesthesia for hand, wrist, forearm or elbow surgery. 'Risk of bias' assessment indicated that trial design and conduct were generally adequate; the most common areas of weakness were in blinding and allocation concealment.Nine trials comparing double versus single injections showed a statistically significant decrease in primary anaesthesia failure (risk ratio (RR) 0.55, 95% confidence interval (CI) 0.34 to 0.89, high-quality evidence). Subgroup analysis by method of nerve location showed that the effect size was greater when neurostimulation was used rather than the transarterial technique.Nine trials comparing multiple with single injections showed a statistically significant decrease in primary anaesthesia failure (RR 0.25, 95% CI 0.14 to 0.42, high-quality evidence). Pooled data from five trials also showed a significant decrease in incomplete motor block (RR 0.61, 95% CI 0.39 to 0.96, high-quality evidence) in the multiple-injection group.Twelve trials comparing multiple versus double injections showed a statistically significant decrease in primary anaesthesia failure (RR 0.27, 95% CI 0.19 to 0.39, high-quality evidence). Pooled data from six trials also showed a significant decrease in incomplete motor block (RR 0.55, 95% CI 0.36 to 0.85, high-quality evidence) in the multiple injection group.Tourniquet pain was significantly reduced with multiple injections compared with double injections (RR 0.53, 95% CI 0.33 to 0.84, high-quality evidence). Otherwise there were no statistically significant differences between groups in any of the three comparisons on secondary analgesia failure, complications and patient discomfort. Compared with multiple injections, the time for block performance was significantly shorter for single injection (MD 3.33 minutes, 95% CI 2.76 to 3.90) and double injections (MD 1.54 minutes, 95% CI 0.80 to 2.29); however there was no difference in time to readiness for surgery. This review provides evidence that multiple-injection techniques using nerve stimulation for axillary plexus block produce more effective anaesthesia than either double or single-injection techniques. However, there was insufficient evidence to draw any definitive conclusions regarding differences in other outcomes, including safety.