Interscalene Block Versus Anterior Suprascapular Block for Post-Thoracotomy Shoulder Pain

Inclusion Criteria: * Age \> 18 years and ≤ 65 years old. * American Society of Anesthesiologists (ASA) physical status II-III. * Body mass index 18-35 kg/m2. * Patients who have a confirmed diagnosis of lung cancer and are scheduled for elective open-lung surgery. Exclusion Criteria: * Allergy to local anesthetics. * Known psychiatric or neurologic disorders. * Alcohol or narcotics abuse. * Contraindications to thoracic epidural or suprascapular block, or interscalene block, e.g., coagulopathy or local infection. * Pre-existing shoulder symptoms. * History of previous thoracotomy. * Severe restrictive or obstructive pulmonary disease. * Pre-existing contralateral diaphragmatic paralysis.