Comparison of the Efficacy and Safety of Intravenous Buprenorphine Administered Via PCA System Versus Oxycodone in the Management of Postoperative Pain After Video-Assisted Thoracoscopic Surgery

The goal of this clinical trial is to learn whether intravenous buprenorphine administered via a patient-controlled analgesia (PCA) system provides effective and safer postoperative pain control than intravenous oxycodone PCA in adults undergoing video-assisted thoracoscopic surgery (VATS). It will also evaluate the overall tolerability of buprenorphine in the early postoperative period and explore longer-term pain outcomes. The main questions it aims to answer are: Does buprenorphine PCA provide pain control that meets predefined targets during the first 48 hours after VATS (both at rest and during respiratory rehabilitation/mobilization), compared with oxycodone PCA? Does buprenorphine PCA reduce clinically relevant respiratory safety events (e.g., apnea or oxygen desaturation requiring intervention) and excessive sedation, compared with oxycodone PCA? What opioid-related adverse effects (e.g., nausea/vomiting, pruritus, constipation, hypotension) occur with buprenorphine PCA versus oxycodone PCA? Does buprenorphine PCA affect time to first patient-initiated analgesic demand and total opioid consumption within 48 hours? Does the choice of PCA opioid influence quality of recovery and the incidence of persistent postoperative pain at follow-up? Researchers will compare buprenorphine PCA to oxycodone PCA (both as part of standardized multimodal analgesia and perioperative care, including serratus anterior plane block) to determine whether buprenorphine provides non-inferior analgesia with a superior safety profile. Participants will: Be randomly assigned (double-blind) to receive buprenorphine PCA or oxycodone PCA for 48 hours after surgery, alongside standard multimodal analgesia Receive standardized general anesthesia for VATS with one-lung ventilation and an ultrasound-guided serratus anterior plane block at the end of surgery Have pain scores (NRS) recorded at multiple time points over 48 hours, at rest and during rehabilitation, and complete recovery questio