Background: Open liver resection is associated with severe postoperative pain. While thoracic epidural analgesia (TEA) is considered the gold standard for pain control, its clinical application is often limited by postoperative coagulation profile derangement, which increases the risk of epidural hematoma. Continuous erector spinae plane block (ESPB) has emerged as a promising, safer alternative with a lower risk of bleeding complications. Objective: This study aims to compare the postoperative analgesic efficacy, safety profiles, and impacts on respiratory function between ultrasound-guided continuous ESPB and TEA in patients undergoing elective open liver resection. Hypothesis: The investigators hypothesize that continuous ESPB using a programmed intermittent bolus (PIB) regimen is non-inferior to TEA regarding 72-hour postoperative pain scores at rest, while offering superior hemodynamic stability and fewer technique-related risks.

This is a randomized, controlled, parallel-group, non-inferiority clinical trial conducted at Bach Mai Hospital. Eligible patients scheduled for elective open liver resection will be randomly allocated into one of two groups at a 1:1 ratio: 1. ESPB Group (n = 30): Patients will receive bilateral erector spinae plane catheters placed at the T7 level under ultrasound guidance prior to anesthesia induction. A bolus of 20 mL Ropivacaine 0.2% will be administered on each side. Postoperative analgesia will be maintained for 72 hours using a Programmed Intermittent Bolus (PIB) regimen of Ropivacaine 0.1%: 24 mL every 3 hours on the right side and 12 mL every 3 hours on the left side. 2. TEA Group (n = 30): Patients will receive a thoracic epidural catheter inserted at the T7-T8 interspace. An initial bolus of 10 mL Ropivacaine 0.1% will be given, followed by a continuous basal infusion of Ropivacaine 0.1% at 5-8 mL/h for 72 hours. Multimodal Analgesia: All patients in both groups will receive a standardized general anesthesia protocol and systemic multimodal analgesia, including intravenous paracetamol (1 g every 6 hours) and nefopam (20 mg every 6 hours). Outcomes Evaluation: The primary outcome is the postoperative pain intensity measured by the Numerical Rating Scale (NRS) at rest 24 hours after surgery. Secondary outcomes include NRS pain scores at rest and during coughing at multiple time points up to 72 hours, cumulative 24-hour morphine consumption, hemodynamic parameters, and incidence of adverse events (e.g., hypotension, postoperative nausea and vomiting, hematoma, or catheter failure)

Inclusion Criteria:

• * Patients aged between 18 and 80 years old.

  • American Society of Anesthesiologists (ASA) physical status classification I to III.
  • Scheduled to undergo elective open liver resection (open hepatectomy).
  • Patient provides written informed consent to participate in the study.

Exclusion Criteria:

• Severe coagulation profile derangement prior to surgery (defined as International Normalized Ratio [INR] > 1.5 or 2.0, or Platelet count [PLT] < 50 G/L or 100 G/L).

  • Severe hepatic impairment (Child-Pugh Class C).
  • Severe chronic obstructive pulmonary disease (COPD GOLD stage III-IV).
  • Severe cardiac dysfunction with an ejection fraction (EF) < 35%.
  • Severe obesity with a Body Mass Index (BMI) > 40 kg/m².
  • Localized infection at the planned puncture/needle insertion site.
  • Known allergy or hypersensitivity to local anesthetics (e.g., Ropivacaine) or opioids (e.g., Morphine).
  • Pregnancy or current lactation.

The individual patient data will not be shared publicly to maintain patient confidentiality and privacy in accordance with local institutional regulations. The aggregated results will be published in the final thesis and scientific journals