Opioid-Free Versus Opioid-Based Anesthesia in Thyroid Surgery

This study will compare opioid-free anesthesia and opioid-based anesthesia in adult euthyroid patients undergoing elective thyroidectomy. Opioid-based anesthesia is commonly used during surgery, but opioids may be associated with adverse effects such as nausea, vomiting, respiratory depression, hyperalgesia, and increased postoperative opioid use. Opioid-free anesthesia uses non-opioid medications as part of a multimodal strategy to provide intraoperative analgesia. The main aim of this prospective randomized study is to evaluate whether opioid-free anesthesia changes the perioperative oxidative stress response compared with opioid-based anesthesia. Oxidative stress will be assessed using serum biomarkers, including native thiol, total thiol, disulfide, total antioxidant status, total oxidant status, and oxidative stress index. Eligible patients will be randomly assigned to receive either opioid-free anesthesia or fentanyl-based opioid anesthesia. Blood samples will be collected before anesthesia induction, 30 minutes after extubation, and 24 hours after surgery. The study will also compare postoperative pain scores, rescue analgesic requirement, postoperative nausea and vomiting, recovery characteristics, and intraoperative hemodynamic variables between the two anesthesia strategies.

Inclusion Criteria: * Adult patients aged 18 to 65 years * Scheduled for elective thyroidectomy * American Society of Anesthesiologists physical status I-II * Euthyroid status, defined as thyroid-stimulating hormone, free thyroxine, and free triiodothyronine levels within the reference range * Able to understand the study procedures and provide written informed consent Exclusion Criteria: * Uncontrolled advanced systemic disease, including advanced cardiac, pulmonary, renal, or hepatic failure * Active infection * Use of high-dose antioxidant supplementation within the last month * Widespread inflammation related to malignancy * Known severe allergy or contraindication to any study medication * Refusal to participate in the study