Comparison of the Postoperative Analgesic Effects of the Temperature-responsive Gel Mixed With Local Anesthetics Application and Ultrasound-guided Transversus Abdominis Plane Block in Patients Undergoing Laparoscopic Gastrectomy

This study is a single-center, prospective, randomized controlled trial designed to compare two established postoperative analgesic strategies in adult patients undergoing laparoscopic gastrectomy under general anesthesia.

Effective pain control after laparoscopic gastrectomy is essential to promote early recovery, facilitate ambulation, reduce opioid consumption, and improve overall postoperative outcomes. Although minimally invasive techniques reduce surgical trauma, patients frequently experience moderate postoperative pain arising from abdominal wall incisions and trocar insertion sites.

This trial compares two analgesic approaches:

Ultrasound-guided bilateral transversus abdominis plane (TAP) block using 0.2% ropivacaine

Local application of a thermosensitive ropivacaine-poloxamer 407 hydrogel formulation (Welpass®) applied to the surgical site at the end of surgery

A total of 80 patients (age ≥19 years, American Society of Anesthesiologists physical status I-III) scheduled for elective laparoscopic gastrectomy will be enrolled at a single institution. Participants will be randomly assigned in a 1:1 ratio to either the TAP block group (n=40) or the hydrogel group (n=40).

In the TAP block group, 0.2% ropivacaine will be injected bilaterally between the internal oblique and transversus abdominis muscles under ultrasound guidance at the completion of surgery.

In the hydrogel group, a mixture of ropivacaine and poloxamer 407-based gel (Welpass®) will be prepared and applied locally to the surgical site, including the fascial plane and subcutaneous tissue, prior to wound closure.

All patients will receive standardized general anesthesia and postoperative patient-controlled analgesia (PCA) according to institutional protocols.

The primary objective of the study is to compare postoperative pain intensity between the two groups. Pain will be assessed using the Visual Analog Scale (VAS) immediately upon arrival in the post-anesthesia care unit (PACU), just before PACU discharge, and at 12 and 24 hours after surgery.

Secondary outcomes include:

• Total PCA consumption within 48 hours
• Additional analgesic use (total dose and frequency)
• Time to first flatus
• Time to ambulation
• Length of hospital stay
• Incidence of postoperative nausea and vomiting (PONV)

Safety will be evaluated by monitoring adverse events, including signs of local anesthetic systemic toxicity or other serious complications. Both analgesic techniques involve medications and procedures that are widely used in routine clinical practice. The study uses approved drugs within standard dosing ranges and is conducted by experienced clinicians. If a serious adverse event suspected to be related to the intervention occurs, appropriate medical management will be provided immediately, and the Institutional Review Board (IRB) will be notified in accordance with regulatory requirements.

Participants may be withdrawn from the study if they experience a serious adverse reaction related to the intervention, if conversion to open surgery occurs, or if they choose to withdraw consent.

The aim of this study is to determine whether local application of sustained-release ropivacaine hydrogel provides analgesic efficacy comparable or superior to ultrasound-guided TAP block. The findings may help identify an effective and safe postoperative pain management strategy for patients undergoing laparoscopic gastrectomy and contribute to optimizing multimodal analgesia protocols in minimally invasive gastric surgery.