Distant Extrafascial Injection vs Subfascial Injection for Interscalene Block: Acute Pain Outcomes and Rates of Complications

The objective of this randomized controlled trial is to compare the analgesic efficacy and the safety profile between two techniques of injection for the interscalene block. The interscalene block consists of injecting local anesthetic around the cervical roots of the brachial plexus and allows analgesia after shoulder surgery. Stated differently, the dual objective of that study is: 1. to confirm that an injection at a distance of 4 mm away from the lateral sheath of the plexus (distal injection) provides similar analgesia as a classical injection within the plexus (subfascial injection); 2. to demonstrate that a distant extrafascial injection produces less respiratory complications than a subfascial injection, defined as hemidiaphragmatic paresis.