Shoulder Pericapsular Block Versus Interscalene Block in Arthroscopic Shoulder Surgery

Interscalene block is widely used for shoulder surgery but is frequently associated with ipsilateral hemidiaphragmatic paralysis due to phrenic nerve involvement. The shoulder PENG block is a more distal pericapsular technique targeting articular branches and may reduce diaphragmatic impairment. This prospective, parallel-group, randomized controlled trial will enroll 68 adult patients scheduled for elective shoulder surgery. Participants will be randomly assigned (1:1) to receive either ultrasound-guided intrafascial interscalene block or ultrasound-guided shoulder PENG block. Both groups will receive 15 mL of 0.25% bupivacaine (total dose 37.5 mg). Diaphragmatic excursion will be measured at baseline and 30 minutes after block performance using M-mode ultrasonography by a blinded assessor. The primary endpoint is hemidiaphragmatic paralysis defined as ≥25% reduction in diaphragmatic excursion from baseline. Partial and complete paralysis will be analyzed as a composite binary outcome.