Serratus Posterior Superior Intercostal Plane Block for Postoperative Analgesia in Mastectomy

Inclusion Criteria: * Female patients aged 18-65 years * ASA physical status I-III * Scheduled for elective unilateral mastectomy with axillary lymph node dissection under general anesthesia * Able to understand and use the Numeric Rating Scale (NRS) for pain assessment * Provided written informed consent Exclusion Criteria: * Known allergy or hypersensitivity to local anesthetics (e.g., bupivacaine) * Coagulopathy, thrombocytopenia (\<100,000/mm³), or ongoing anticoagulant/antiplatelet therapy that cannot be discontinued * Infection or skin lesion at the injection site * Planned bilateral surgery or additional major surgical procedures * Chronic pain conditions or regular use of opioids, gabapentinoids, or centrally acting analgesics * Neurological or psychiatric conditions interfering with pain assessment * History of previous major thoracic or chest wall surgery on the same side * Pregnancy or breastfeeding * Refusal to participate or inability to provide informed consent