Ultrasound guidance compared with electrical neurostimulation for peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Despite the growing interest in the use of ultrasound (US) imaging to guide performance of regional anaesthetic procedures such as peripheral nerve blocks, controversy still exists as to whether US is superior to previously developed nerve localization techniques such as the use of a peripheral nerve stimulator (PNS). We sought to clarify this issue by performing a systematic review and meta-analysis of all randomized controlled trials that have compared these two methods of nerve localization.
METHODS: We searched Ovid MEDLINE, the Cochrane Central Register of Controlled Trials, and Google Scholar databases and also the reference lists of relevant publications for eligible studies. A total of 13 studies met our criteria and were included for analysis. Studies were rated for methodological quality by two reviewers. Data from these studies were abstracted and synthesized using a meta-analysis.
RESULTS: Blocks performed using US guidance were more likely to be successful [risk ratio (RR) for block failure 0.41, 95% confidence interval (CI) 0.26-0.66, P<0.001], took less time to perform (mean 1 min less to perform with US, 95% CI 0.4-1.7 min, P=0.003), had faster onset (29% shorter onset time, 95% CI 45-12%, P=0.001), and had longer duration (mean difference 25% longer, 95% CI 12-38%, P<0.001) than those performed with PNS guidance. US guidance also decreased the risk of vascular puncture during block performance (RR 0.16, 95% CI 0.05-0.47, P=0.001).
CONCLUSIONS: US improves efficacy of peripheral nerve block compared with techniques that utilize PNS for nerve localization. Larger studies are needed to determine whether or not the use of US can decrease the number of complications such as nerve injury or systemic local anaesthetic toxicity.