Ultrasound Guidance for Interscalene Brachial Plexus Block

This study has been designed to assess the possible advantages of using ultrasound imaging to block the brachial plexus (i.e., nerves of the upper limb) in patients undergoing shoulder surgery. The ultrasound technique will be compared with the current gold standard, electrical nerve stimulation. The aim of this study is to define which technique is better in terms of time to onset of anesthesia.