Autonomic and Immune Effects of Regional Anesthesia in Total Hip Arthroplasty

Surgical trauma activates the sympathetic nervous system and induces a systemic inflammatory response, both of which may adversely affect postoperative recovery. Regional anesthesia has traditionally been used for perioperative analgesia; however, emerging evidence suggests that peripheral nerve blocks may also modulate autonomic and immune pathways. This prospective randomized double-blind trial aims to compare three regional anesthesia strategies in patients undergoing elective total hip arthroplasty under spinal anesthesia and to determine their effects on autonomic regulation, systemic inflammatory response, postoperative pain, opioid consumption, quality of recovery, and early functional outcomes.

Inclusion Criteria: * Adults aged ≥18 years. * Scheduled for elective primary total hip arthroplasty due to primary hip osteoarthritis. * American Society of Anesthesiologists (ASA) physical status I-III. * Planned spinal anesthesia with one of the study regional analgesia techniques. * Ability to understand the study procedures and provide written informed consent. Exclusion Criteria: * Refusal or inability to provide written informed consent. * Revision hip arthroplasty, simultaneous bilateral hip arthroplasty, or hip arthroplasty performed for an acute fracture. * Known hypersensitivity to ropivacaine or other medications required for the study procedures. * Contraindication to spinal anesthesia, PENG block, or local infiltration analgesia, including infection at the injection site or a coagulation disorder or antithrombotic treatment that precludes safe performance of the planned procedures. * Pre-existing neurological or neuromuscular disease that substantially affects sensation or motor function in the operated limb or prevents reliable assessment of study outcomes. * Cognitive impairment or a communication disorder that prevents understanding of the study procedures or reliable completion of pain assessments. * A medical condition that, in the investigator's judgment, makes participation or the planned anesthetic procedures unsafe. * Planned use of an additional regional analgesic technique outside the study protocol. * Participation in another interventional study that could interfere with the assessment of the study outcomes.