In recent years, video-assisted thoracic surgery (VATS) has largely matured and gained widespread acceptance. Patients undergoing VATS have been reported to have less postoperative pain and a better quality of life. VATS has fewer overall post-operative complications, shorter hospital stays and lower rates of blood transfusion than conventional open surgery. However, about 38% of patients who underwent VATS were still reported to have severe postoperative pain. The placement of a thoracic drain increases the level of post-operative pain, especially when the patient breathes deeply, moves around or coughs, making the patient afraid to cooperate with deep breathing or coughing after surgery, thus increasing the chance of post-operative atelectasis and lung infection.

Epidural analgesia (EA) is the 'gold standard' for postoperative analgesia in the thoracic surgery and is an important component of multimodal analgesia in thoracic surgery. Continuous epidural infusion (CEI) of local anesthetic combined with patient-controlled analgesia (PCA) is an effective method of post-operative analgesia in thoracic surgery. However, CEI has some disadvantages, such as increased consumption of local anesthetic and limited distribution area of anesthetic, which does not suppress pain during deep breathing or coughing in the postoperative period very well, resulting in poor appetite and reduced quality of recovery. Programmed intermittent epidural bolus (PIEB) is an epidural analgesia modality that has emerged in recent years and has been more comprehensively studied in the field of postoperative analgesia in obstetrics. PIEB mode has been shown to provide better analgesia and lower consumption of local anesthetic compared to the traditional CEI mode.

The current study of PIEB in thoracic surgery under VATS is still unclear and we wanted to investigate the effect of procedural intermittent epidural bolus (PIEB) versus continuous epidural infusion (CEI) on the quality of recovery in patients undergoing lobectomy by VATS. The trial was divided into two groups, with the control group (CEI group) using a continuous epidural infusion and the trial group (PIEB group) using a programmed intermittent epidural infusion. All subjects received a standardised epidural solution containing 0.2% ropivacaine and 0.4（male）/0.3（famale）μg/ml sufentanil. The CEI group was infused continuously at a rate of 0.05\*kg ml/h, while the PIEB group was programmed for intermittent infusion with 0.1\*kg pumped every two hours. The PCEA is 4ml in both groups. The lockout time for both groups was 60 min. The maximum infusion dosage of the both groups is 10ml/h. Heart rate, ECG, pulse oximetry, invasive blood pressure, and end-expiratory carbon dioxide partial pressure (ETCO2) are routinely monitored on admission. Prior to induction of anaesthesia, ultrasound-assisted epidural puncture placement in the mid-thoracic segment (T5/6 or T6/7 or T7/8) is performed and the success of placement is judged using the disappearance of resistance method. The epidural catheter was placed 5 cm cephalad and 3 mL of 1.5% lidocaine was injected epidurally as a test dose to rule out inadvertent vessel entry and dural breach. This was followed by an epidural push of 10-20 mL of 0.2% ropivacaine with a test plane in the T1-T10 range. General anesthesia was induced with intravenous dexmedetomidine (0.5 ug/kg), propofol (2 mg/kg), sufentanil (0.2 ug/kg) and cis-atracurium (0.15 mg/kg). Anesthesia is maintained with 4ug/ml propofol in TCI model, with additional cis-atracurium as required, followed by additional epidural 0.2 % ropivacaine at the discretion of the anesthetist and recorded as appropriate. Vasoactive drugs may be used as appropriate to maintain blood pressure fluctuations within ±20% of basal blood pressure. The QoR15 rating scale (Quality of Recovery-15, QoR15) is one of the main methods currently used to evaluate postoperative recovery and is a valid, reliable and responsive patient-centred prognostic indicator that is highly acceptable to both patients and clinicians. Therefore, we used the 24h postoperative QoR15 score as the primary outcome.