Comparison of ultrasound and nerve stimulation for interscalene catheter placement

INTERVENTION: Interscalene catheter placed using either ultrasound or nerve stimulation Ultrasound (US) Group The needle will be advanced superficially in a caudal and peripheral direction until tissue displacement is observed just lateral to the brachial plexus trunks in the body of the middle scalene muscle. Dextrose 5% 5‐10 mL will be injected down the needle to observe for appropriate fluid spread adjacent to the brachial plexus trunks, and a non‐stimulating catheter advanced 2 cm past the needle tip. If US imaging proves difficult, a brief appropriate muscle twitch will be sought with a nerve stimulator set to 0.8 mA to confirm brachial plexus position. Sustained muscle twitches at 0.2‐0.5mA will not be sought. If satisfactory US images cannot be attained within 5 min, the probe will be discarded and interscalene catheter (ISC) placement conducted blind as per the NS group. Duration of procedure: 15 min CONDITION: Analgesia following shoulder surgery PRIMARY OUTCOME: Analgesic consumption and pain scores during first 48 hours, researcher questioning patient on days 1 and 2. ; Assessment tool: numerical rating pain score (0‐10). SECONDARY OUTCOME: Needle time under the skin at interscalene catheter (ISC) insertion. INCLUSION CRITERIA: Patients requiring continuous interscalene analgesia following elective shoulder surgery under the care of the principal investigator.