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.
Comparative evaluation of ultrasound-guided continuous infraclavicular brachial plexus block with stimulating catheter and traditional technique: a prospective-randomized trial.
Secondary catheter failure has been reported in up to 40% of patients with continuous peripheral nerve blocks resulting in failure to provide pain relief after the initial block wears off. Introduction of stimulating catheters as well as ultrasound for regional anaesthesia has facilitated correct placement of catheter tip, closer to the plexus. This randomized study was conducted to compare the efficacy of continuous infraclavicular brachial plexus blocks using non-stimulating catheter, stimulating catheter and ultrasound-guided catheter placement with nerve stimulation assistance.
                Patients undergoing elective hand surgery were randomly allocated to receive continuous infraclavicular brachial plexus block using non-stimulating catheter [group traditional nerve stimulation (TR)], stimulating catheter [group stimulating catheter (ST)] or ultrasound-guided catheter placement with nerve stimulation assistance [group ultrasound guidance with nerve stimulation assistance (US)]. Motor and sensory blocks were assessed every 5 min and primary block success was determined at 30 min. After resolution of the primary block, threshold stimulating current and resulting response, spread of drug on re-injection as seen ultrasonographically and the capacity to re-establish block was documented. Complications and need for supplement was noted.
                The primary block success was significantly higher in the US group [96% US, 58% ST, 59% TR (P=0.0005)]. Secondary catheter failure was significantly lower in the US group [9% US, 17% ST, 86% TR (P<0.0001)]. Axillary nerve was blocked more predictably in the US group (100% US, 79% ST, 50% TR (P=0.0003).
                In this study, ultrasound guidance with nerve stimulation assistance significantly improved primary success and reduced secondary catheter failure in continuous infraclavicular brachial plexus blocks.