Patients in the esketamine group was induced with esketamine 0.5 mg/kg, propofol 2 mg/kg, and rocuronium 0.9 mg/kg. Anesthesia is maintained with propofol 5 mg/kg/h and esketamine 0.5 mg/kg/h. Patients in the opioid group was induced with sufentanil 0.5 ug/kg, propofol 2 mg/kg, rocuronium 0.9 mg/kg. Anesthesia is maintained with propofol 5 mg/ kg/h and remifentanil 0.1 ug/kg/min.

Before anesthesia induction, radial artery puncture and catheterization under local anesthesia for manometry, and intravenous dexmedetomidine (1 µg/kg) infused over 15 minutes, followed by penehyclidine hydrochloride (0.01mg/kg), palonosetron (0.075 mg), dexamethasone (5 mg). Anesthesia-induced in the opioid group (group A) was intravenous sufentanil 0.5 ug/kg, and esketamine group (group E) received intravenous esketamine 0.5 mg/kg. Subsequently, both groups were sequentially injected with propofol 2 mg/kg and rocuronium 0.9 mg/kg. After the onset of rocuronium, the left-sided double-lumen endotracheal tube was guided by a video laryngoscope, the correct position of the tube was confirmed by bronchoscope, and the anesthesia machine was connected to the tube for mechanical ventilation after fixation, with a tidal volume of 6-8 mL/kg (ideal body weight), a respiratory rate of 10~18 breaths/min, and end-expiratory carbon dioxide partial pressure at 35~45 mmHg (4.7-6.0 kPa).

Intraoperative anesthesia maintenance in the opioid group was pumped with propofol (5 mg/ kg/h) and remifentanil (0.1 ug/kg/h), and esketamine group was pumped with propofol (5 mg/kg/h) and esketamine (0.5 mg/kg/h). Rocuronium was administered as needed in intermittent boluses of 0.3 mg/kg intraoperatively. After the lateral decubitus position is set up and the paravertebral block (T4 and T6 levels, 0.5% ropivacaine, 10 ml each) was performed under ultrasound guidance, supplemented by 0.75% ropivacaine infiltration at the surgical site upon skin closure. At the completion of the surgery, patients were given 200 mg sugammadex sodium as an antagonistic residual muscle relaxant. They were transferred to the post-anesthesia care unit (PACU) after tracheal extubation and full recovery of consciousness, and returned to the thoracic surgery ward for further treatment after reaching the discharge criteria of PACU. Postoperative analgesia was provided without patient-controlled intravenous analgesia (PCIA). We employed a modified Brice questionnaire to assess the occurrence of intraoperative awareness. The confusion assessment method (CAM) was used to assess postoperative delirium (POD). Rescue analgesia with intravenous flurbiprofen axetil (50 mg) was administered when NRS scores reached ≥4. Rescue antiemetic therapy (intravenous palonosetron 0.075 mg) was provided for postoperative nausea and vomiting (PONV) scores reached ≥4.

Update note (2026-01-04): The record was updated to correct terminology/wording errors (e.g., static vs dynamic compliance; increased intracranial pressure vs intracranial pressure) and to clarify that PCIA was not used. Meanwhlie, a more detailed account that specifies the anesthetic management protocol with greater precision was provided. One prespecified secondary outcome (inflammatory biomarkers) was not collected; therefore, no data are available for that outcome.

Inclusion Criteria

1. ASA physical status I-II
2. age 18-70 years
3. thoracoscopic segmentectomy or lobectomy is proposed under general anesthesia due to pulmonary nodule
4. informed consent was obtained Exclusion Criteria

(1) body mass index ˃30 kg/m2 or ˂ 19 kg/m2 (2) preoperative use of opioids, acute and chronic pain or hyperalgesia (3) significant ischemic heart disease, including preoperative coronary artery disease, severe angina, heart failure, or structural heart disease (e.g., significant valvular disease) (4) severe hepatic and renal failure before operation (5) history of mental illness or alcoholism (6) history of alcohol or drug abuse (7) increased intracranial pressure, elevated intraocular pressure, or a diagnosis of glaucoma (8) poorly controlled or untreated hypertension (9) preeclampsia or eclampsia (10) untreated and undertreated hyperthyroidism (11) inability to complete the required rating scales

Neither the patients who participated in the trial nor the analysis of the results of the study were aware of the experimental group