Ultrasound guidance for peripheral nerve blockade

BACKGROUND: Peripheral nerve blocks can be performed using ultrasound guidance. It is not yet clear whether this method of nerve location has benefits over other existing methods. OBJECTIVES: To assess whether the use of ultrasound to guide peripheral nerve blockade has any advantages over other methods of peripheral nerve location. SEARCH STRATEGY: We searched the following databases for relevant published trials: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 3); MEDLINE (1966 to July 2008); EMBASE (1974 to July 2008); ISI Web of Science (1945 to 2008 ); CINAHL (1982 to July 2008); and LILACS (1980 to July 2008). We also handsearched meeting supplements. SELECTION CRITERIA: We included all identified randomized controlled trials (RCTs) comparing ultrasound-guided peripheral nerve block with at least one other method of nerve location. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial quality and extracted data. We attempted to contact study authors for additional information, where necessary. MAIN RESULTS: We included 18 trials containing data from 1344 patients. Ten trials assessed upper limb blocks and eight assessed lower limb blocks. Most compared ultrasound with peripheral nerve stimulation. All trials were assessed as having a moderate risk of bias due to inability to blind the practitioner. Meta-analysis was not performed because of the variety of blocks, techniques, and outcomes, and the review was based on the authors' assessment of the trials. Ultrasound guidance produced similar success rates in providing surgical anaesthesia (72% to 98.8%) when compared with peripheral nerve stimulation (58% to 93.1%). Major complication rates were low in all studies; however, the use of ultrasound appeared to reduce the incidence of vascular puncture or haematoma formation. Differences in study methodology made it difficult to compare block characteristics, however ultrasound improved quality of sensory block in six studies and motor block in four studies. Block onset time was found to be improved in six out of the 10 studies where this was assessed. Two studies assessed volume of local anaesthetic required and both found a significant reduction was possible when ultrasound was used. Ten studies assessed block performance time and five found a significant reduction with ultrasound, the mean difference in time taken was 1.5 to 4.8 minutes. AUTHORS' CONCLUSIONS: 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.