Injection Site in Ultrasound-Guided Interscalene Block for Shoulder Arthroscopy

Ultrasound-guided interscalene block is commonly used for postoperative analgesia in patients undergoing shoulder arthroscopy. The location of local anesthetic injection may influence both block efficacy and the incidence of block-related complications. This randomized, double-blind clinical trial compares two different injection sites around the C5-C7 nerve roots using the same local anesthetic dose and volume. The study will assess block success, postoperative analgesia, opioid consumption, diaphragmatic function, and procedure-related complications.

Inclusion Criteria: Adults aged 18 years or older. ASA physical status I-III. Scheduled for shoulder arthroscopy under general anesthesia with a planned ultrasound-guided interscalene block for postoperative analgesia. Able to provide written informed consent. Normal coagulation parameters and no antithrombotic therapy. No infection or anatomical abnormality at the injection site. No known allergy to local anesthetics. No contralateral diaphragmatic paralysis or pneumothorax. No dyspnea and adequate pulmonary function. Exclusion Criteria: Age younger than 18 years or ASA physical status IV. Antithrombotic therapy or abnormal coagulation parameters. Infection or anatomical abnormality at the injection site. Known allergy to local anesthetics. Contralateral diaphragmatic paralysis or history of pneumothorax. Dyspnea. Refusal to undergo interscalene block.