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 - A Prospective, Randomized Clinical Trial

This prospective, randomized, double-blind clinical trial is designed to compare the efficacy and safety of intravenous buprenorphine delivered via a patient-controlled analgesia (PCA) system versus intravenous oxycodone PCA for the management of postoperative pain after video-assisted thoracoscopic surgery (VATS). The study will be conducted at the Department of Anesthesiology and Intensive Care, Faculty of Medical Sciences in Zabrze, Medical University of Silesia in Katowice, and will enroll 200 adult patients aged 18-75 years who are scheduled for elective VATS, have an ASA physical status of I-III, are expected to use a PCA device postoperatively, and provide written informed consent. Prior to randomization, baseline assessment will include age, sex, height, body mass index (BMI), noninvasive arterial blood pressure (systolic, diastolic, and mean), relevant comorbidities (including arterial hypertension, diabetes mellitus, ischemic heart disease, and chronic pain), current analgesic medications, use of psychoactive substances, preoperative pain intensity measured with the Numerical Rating Scale (NRS; 0-10), ASA classification, and confirmation of the patient's ability to appropriately use the PCA pump after surgery. Pain will be evaluated using NRS (0 = no pain; 10 = worst imaginable pain). After eligibility confirmation, patients will be randomized (computerized REDCap system) to one of two treatment arms-OXY or BUPRE-under a double-blind design in which both the patient and the assessor recording pain outcomes remain unaware of the allocated opioid.

All participants will receive standardized perioperative analgesia and anesthetic care. As preemptive analgesia administered 30 minutes before incision, patients will receive paracetamol 1.0 g intravenously (Paracetamol Biofarm, Poland) and metamizole 1.0 g intravenously (Pyralgia, Polpharma, Poland). General anesthesia will be performed with double-lumen endotracheal intubation and controlled one-lung ventilation (OLV) tailored to the requirements of VATS. If premedication is required, midazolam 1-2 mg IV will be administered approximately 10 minutes before induction. Standard monitoring will include 3-5 lead ECG, noninvasive blood pressure measurement every 5 minutes, pulse oximetry (SpO₂), capnography (EtCO₂), depth of anesthesia monitoring (BIS), and neuromuscular transmission monitoring (Train-of-Four, TOF). Invasive arterial blood pressure monitoring (arterial line) will be used in prolonged procedures or in patients with increased hemodynamic risk, and arterial blood gas analysis (ABG) will be performed after initiation of OLV and whenever clinically indicated by intraoperative changes.

Induction of anesthesia will be achieved with propofol 1.5-2.5 mg/kg IV, fentanyl 1-2 µg/kg IV, and rocuronium 0.6 mg/kg IV to facilitate tracheal intubation. Following loss of consciousness and adequate neuromuscular blockade, a double-lumen tube will be placed, and correct positioning will be confirmed after lateral decubitus positioning and after initiation of OLV. Maintenance anesthesia will use sevoflurane 0.8-1.2 MAC in an air/oxygen mixture with FiO₂ 0.8-1.0, with continued neuromuscular blockade using rocuronium 0.15 mg/kg administered every 20-45 minutes as required. Intraoperative fluid therapy will consist of balanced crystalloid solutions (e.g., Plasmalyte or Optilyte) at 1-4 ml/kg/h according to a goal-directed fluid therapy protocol. Hemodynamic management will include treatment of hypotension with ephedrine 5-10 mg IV or a norepinephrine infusion titrated to maintain mean arterial pressure (MAP) above 70 mmHg.

Mechanical ventilation will be delivered in PCV-VG mode. During two-lung ventilation, tidal volume will be set at 6-8 ml/kg predicted body weight (PBW) with PEEP of 5 cmH₂O. During OLV, tidal volume will be reduced to 4-6 ml/kg PBW with PEEP 5-8 cmH₂O and FiO₂ 1.0, and the respiratory rate will be adjusted to maintain EtCO₂ between 35 and 45 mmHg. If hypoxemia occurs, predefined interventions will include alveolar recruitment maneuvers, application of CPAP to the nonoperative lung, or intermittent periods of two-lung ventilation.

To provide regional chest wall analgesia, an ultrasound-guided serratus anterior plane block will be performed on the operative side at the end of surgery, prior to transfer to the post-anesthesia care unit (PACU). Using a high-frequency linear probe (6-13 MHz) and a 50-100 mm block needle, the anesthesiologist will identify the latissimus dorsi muscle, serratus anterior muscle, and ribs at the level of the 4th-6th intercostal space in the mid-axillary or posterior axillary line. After skin disinfection and negative aspiration, a small test injection (1-2 ml) will be used to confirm correct fascial plane separation, followed by injection of 20-30 ml of local anesthetic-either 0.25% bupivacaine or 0.375% ropivacaine-selected according to body weight. Depending on patient anatomy and clinician preference, the injection may be performed in the superficial plane (between latissimus dorsi and serratus anterior) or the deep plane (between serratus anterior and the ribs), aiming to cover dermatomes Th2-Th9 of the lateral and anterior chest wall.