Numerous studies have confirmed that regional analgesia using peripheral nerve block has great potential for perioperative analgesia in abdominal surgery. Ultrasound guided costal margin block (CMB) is a new regional anesthesia technique that has been proven to compensate for the analgesic effects of regional analgesia techniques such as transverse abdominal muscle plane (TAP) and rectus abdominis sheath (RSB) on mid abdominal incisions, but it is difficult to meet the analgesic needs of anterior and outer abdominal wall incisions. According to relevant anatomy and research, the application of local anesthetics along the rib margin under the rectus abdominis muscle or under the external oblique muscle on the rib surface can block the lateral and anterior cutaneous branches of the thoracoabdominal nerve, known as CMB. Ultrasound guided CMB requires the injection of local anesthetics onto the surface of the rib along the plane below the rectus abdominis and oblique muscles, covering most of the upper abdominal incision pain. However, there are few reports on other types of upper abdominal surgeries such as liver, gallbladder, and pancreas surgeries.

Bupivacaine liposomes are an important innovation, which encapsulate bupivacaine in polycystic liposomes using DepoFoam technology to achieve slow drug release and effectively prolong pain relief time by up to 72 hours. This ultra long acting local anesthetic has significant advantages in reducing opioid use, improving analgesic satisfaction, reducing complications, and shortening hospital stays, and has been applied in the ERAS concept.

The investigators designed a prospective, single blind, randomized, active controlled clinical trial to investigate the effect of bupivacaine liposomes in combination with bupivacaine mixture or bupivacaine alone for ultrasound-guided bilateral CMB on postoperative analgesia in patients undergoing laparoscopic hepatobiliary pancreatic surgery. Our main hypothesis is that the use of bupivacaine liposomes and a mixture of bupivacaine for ultrasound-guided CMB in a multimodal analgesia regimen can more effectively reduce the dosage of intravenous patient-controlled analgesia (PCA) opiates within 72 hours after laparoscopic hepatobiliary pancreatic surgery compared to using bupivacaine alone. Secondary outcomes include the dosage of PCA opiates within 24-48 hours, pain score values, patient satisfaction, adverse reactions, and complications.

All participators were randomized into two groups using a complete randomization allocation method: the trial group and the control group. An investigator introduced the study to the study before surgery and informed consent was obtained. The investigators educate patients on how to use the VAS scale to express pain intensity and instruct patients on how to use the postoperative analgesia pump. General anesthesia with endotracheal intubation or laryngeal mask before the nerve block. Standard analgesic protocol: sufentanil (0.5 μg/ kg) + remifentanil (0.1-0.2 μg / kg/min) + flurbiprofen ester (50mg); intravenous analgesia pump (PCIA) or analgesic with opioids and non-steroidal anti-inflammatory drugs as needed. All patients underwent ultrasound-guided bilateral costal margin block (CMB). Test group: 20ml bupivacaine liposomes +10ml 0.75% bupivacaine hydrochloride + 20ml normal saline, for ultrasound-guided CMB. Control group: 10 ml of 0.75% bupivacaine hydrochloride + 40ml of normal saline, with ultrasound-guided CMB.

Inclusion Criteria:

• 18-80 years old ASA Level I-III Laparoscopic Hepatobiliary Pancreatic Surgery

Exclusion Criteria:

• Body Mass Index (BMI) ≥ 30 kg/m ² or ≤ 15 kg/m ² Known alcohol or drug abuse History of upper abdominal surgery Congenital coagulation dysfunction Localized or systemic infection Peripheral neuropathy Unable to understand the research plan

individual participant data sets to be shared will include all collected individual participant data that underlie the results reported in any publications resulting from the trial. This would typically include data related to pain relief, opioid analgesic consumption, incidence of complications, and any other relevant outcomes assessed at multiple time points within 72 hours after surgery.

From February 1,2025 to February 1,2027

The IPD and any additional supporting information will be shared with qualified researchers upon request. Access will be granted for the purpose of conducting further analyses related to the outcomes of the clinical trial, such as but not limited to, pain relief, opioid analgesic consumption, and complications. Requests for access will be reviewed by the principal investigators and designated research personnel to ensure that the proposed analyses align with the objectives of the study and maintain participant confidentiality. Access to the data will be provided through a secure mechanism that safeguards the privacy and integrity of the individual participant data.