Magnesium Sulphate as an Adjuvant in Combined Costoclavicular Block and Suprascapular Block Versus Interscalene Block for Ambulatory Shoulder Arthroscopy

Shoulder arthroscopy is a common outpatient procedure that can cause moderate to severe pain during the first 24 to 48 hours after surgery. An interscalene brachial plexus block (ISB) is widely used to provide pain relief, but it frequently causes temporary weakness or paralysis of the diaphragm (the main breathing muscle) by blocking the phrenic nerve, which can lead to shortness of breath. A combined costoclavicular and suprascapular nerve block (CCB-SSNB) has emerged as an alternative approach that numbs the shoulder while potentially preserving normal breathing and diaphragmatic function. Additionally, adding magnesium sulfate as an adjuvant medication to local anesthetics can help prolong and enhance pain relief. The primary purpose of this study is to compare the pain-relieving efficacy and respiratory safety of ultrasound-guided combined CCB-SSNB versus standard ISB, both administered with magnesium sulfate as an adjuvant, in adult patients undergoing elective outpatient shoulder arthroscopy under general anesthesia. Participants will be randomly assigned to one of two groups prior to surgery: * Group A (Combined CCB-SSNB): Participants will receive an ultrasound-guided suprascapular nerve block (10 mL of 0.5% bupivacaine with 100 mg magnesium sulfate) and an ultrasound-guided costoclavicular block (10 mL of 0.5% bupivacaine with 100 mg magnesium sulfate). * Group B (ISB): Participants will receive an ultrasound-guided interscalene block (20 mL of 0.5% bupivacaine with 200 mg magnesium sulfate). The primary outcome is the duration of pain relief, measured as the time from the end of surgery until the patient first requests rescue pain medication. Secondary outcomes include total opioid consumption during the first 24 hours postoperatively, pain scores at rest and during movement up to 48 hours, ultrasound evaluation of diaphragmatic movement to detect hemidiaphragmatic paresis, recovery time in the post-anesthesia care unit (PACU), patient satisfaction, and any block-related side effects or complications.

Inclusion Criteria: * Age 18-65 years. * American Society of Anesthesiologists (ASA) physical status class I or II. * Scheduled for elective outpatient shoulder arthroscopy under general anesthesia. * Ability to understand the study procedures and provide written informed consent. * Ability to understand and utilize the Numeric Rating Scale (NRS) for postoperative pain assessment. Exclusion Criteria: * Refusal to participate or withdrawal of informed consent. * Known allergy or hypersensitivity to bupivacaine, magnesium sulfate, or any components of the study medications. * Coagulopathy or ongoing anticoagulant therapy contraindicating regional anesthesia. * Local infection or anatomic contraindication at the planned block puncture sites. * Pre-existing peripheral neuropathy, neuromuscular disease, or neurological deficit involving the operative upper limb. * Severe pulmonary disease or respiratory insufficiency. * Body mass index (BMI) \> 40 kg/m². * Chronic opioid use or pre-existing chronic pain syndromes that may interfere with postoperative pain evaluation. * Pregnancy or lactation. * Inability to communicate adequately or complete postoperative pain and follow-up assessments.