Rectus Abdominis Muscle Parameters and Postoperative Opioid Consumption in Geriatric Patients

Inclusion Criteria: * Age ≥65 years * Scheduled for elective midline abdominal surgery * ASA physical status I-III * Planned to receive bilateral ultrasound-guided rectus sheath block as part of routine clinical practice * Provided written informed consent Exclusion Criteria: * Known allergy or hypersensitivity to local anesthetics * Infection or skin lesion at the injection site * Systemic infection or sepsis * Coagulopathy (INR \>1.5 or platelet count \<100,000/mm³) * Use of therapeutic anticoagulation not safely managed perioperatively * History of previous midline laparotomy * History of abdominal mesh implantation or abdominal wall reconstruction * Significant abdominal wall pathology (e.g., large hernia) affecting anatomy * Neuromuscular disease (e.g., myasthenia gravis, ALS, muscular dystrophy) * Inability to perform required maneuver for dynamic ultrasound measurement * Moderate to severe cognitive impairment or poor cooperation * Body mass index (BMI) \>40 kg/m² * Cachexia or severe malnutrition * Chronic opioid use (≥3 months) * Chronic pain syndromes requiring regular analgesic use * Alcohol or substance abuse * Emergency surgery * Use of additional regional anesthesia techniques (e.g., epidural, TAP block) * Inadequate ultrasound visualization of the target anatomical plane