Abstract: 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.

Plain-language summary: We searched the literature up until April 2016 and identified 22 randomized controlled trials for inclusion in the review. These trials involved a total of 2193 participants who were given regional anaesthesia for hand, wrist, forearm or elbow surgery. The trials used methods that were generally adequate and did not affect the validity of the findings. Nine trials compared double versus single injections. These found that people in the double-injection group had a 45% reduction in their chance of needing additional anaesthesia. The effect was more certain in the four trials where the nerves were located using the more precise method of neurostimulation. In the nine trials comparing multiple with single injections, and the 12 trials comparing multiple with double injections, there were significant reductions in the chance of needing additional anaesthesia in the multiple-injection groups (75% and 73% reductions when compared to single and double injections respectively). In addition, people in the multiple-injection group were 47% less likely to experience pain from the surgical tourniquet compared to the double-injection group. There were no other statistically significant differences in complications or patient discomfort between the two groups for any of the three comparisons. Single and double injections took less time to perform than multiple injections, but this did not reduce the total time required for adequate surgical anaesthesia to be established. Overall, there is high-quality evidence showing that multiple injections of anaesthetic close to three or four nerves in the armpit provide more complete anaesthesia for hand and forearm surgery than one or two injections. There was, however, not enough evidence to determine if there was a significant difference in the other outcomes, including safety.