In experienced hands, ultrasound provides at least as good success rates as other methods of peripheral nerve location. Individual studies have demonstrated that ultrasound may reduce complication rates and improve quality, performance time, and time to onset of blocks. Due to wide variations in study outcomes we chose not to combine the studies in our analysis.
Electrical nerve stimulation or ultrasound guidance for lateral sagittal infraclavicular blocks: a randomized, controlled, observer-blinded, comparative study.
Ultrasound guidance is frequently used to perform infraclavicular brachial plexus blocks. In this study, we compared electrical nerve stimulation and ultrasound guidance for the lateral sagittal infraclavicular block.
                Eighty patients, ASA 1-2, were randomized for either nerve stimulation (group NS) or ultrasound-guided blocks (group US). The brachial plexus was anesthetized with 0.6 mL/kg mepivacaine (15 mg/mL) with epinephrine (2.5 microg/mL) in both groups. For ultrasound-guided blocks, local anesthetic was injected cranioposterior to the axillary artery. An observer who was blinded for the method assessed the blocks and questioned the patients. Successful block was defined as analgesia or anesthesia of all five nerves distal to the elbow. The main outcome variables were the time until readiness for surgery, quantified discomfort during the block, and pain related to tourniquet ischemia on a numeric rating scale (0-10).
                Block performance time was 4.3 min (sd 1.3) and 4.1 min (sd 1.3) (P = 0.64) in group NS and group US, respectively. Onset time for sensory block was 13.7 min (sd 6.6) and 13.9 min (sd 5.8), (P = 0.99). The time until readiness for surgery was 18.1 min in both groups (sd 6.6 and 6.0) (P = 0.99). Median discomfort related to the block procedure was 1 in both groups (P = 0.92), and median tourniquet pain was 0.5 in group NS and 1 in group US (P = 32). Differences in success rates, between 85% in group NS and 95% in group US, were not significant (P = 0.26).
                We conclude that favorable results can be obtained when either nerve stimulation or ultrasound guidance is used for lateral sagittal infraclavicular block. Using ultrasound, local anesthetic injection cranioposterior to the artery appears feasible.