Postoperative pain is highly prevalent following laparoscopic radical gastrectomy. Although the erector spinae plane block (ESPB) can effectively alleviate this pain, it still has many limitations. The external oblique intercostal plane block (EOIB) is a novel nerve block technique that may provide well postoperative analgesia for upper abdominal surgery. Therefore, this study employs a non-inferiority randomized controlled trial design to verify that the analgesic effect of EOIB is not inferior to that of ESPB, thereby offering more options for regional analgesia strategies in laparoscopic radical gastrectomy.

Laparoscopic radical gastrectomy (including subtotal and total gastrectomy) is the most commonly used surgical approach for gastric cancer. Although this technique is less invasive than traditional open surgery, more than 50% of patients still experience moderate to severe acute pain in the early postoperative period, making effective postoperative pain management essential. Regional nerve blockade techniques have become a key component of postoperative analgesia due to their reliable analgesic effect and significant reduction in opioid consumption.

The erector spinae plane block (ESPB) is considered a relatively safe nerve block for upper abdominal surgery analgesia. However, the spread of the local anesthetic and the resulting block effect are unpredictable. Moreover, ESPB cannot be performed with the patient in the supine position and may present technical challenges in obese patients.

The external oblique intercostal plane block (EOIB) is a recently proposed regional block technique for the upper abdomen. This block involves injecting local anesthetic into the superficial fascial plane between the external oblique muscle and the intercostal muscles, thereby blocking the anterior rami and cutaneous branches of the intercostal nerves from T6-T10, which can provide effective analgesia for upper abdominal incision areas.

Nevertheless, current research on the analgesic effect of EOIB after laparoscopic radical gastrectomy remains limited, particularly lacking high-quality, prospective, randomized controlled studies to verify whether EOIB can achieve analgesic effects comparable to those of ESPB. Therefore, this study adopts a non-inferiority randomized controlled trial design to verify that the postoperative analgesic effect of EOIB is not inferior to that of ESPB, providing more options for regional analgesia strategies in laparoscopic radical gastrectomy.

Inclusion Criteria:

• Patients aged over 18 years
• Classified as ASA I-III
• Scheduled for elective laparoscopic radical gastrectomy under general anesthesia
• Voluntarily participated and provided written informed consent.

Exclusion Criteria:

• Chronic opioid dependence or prior use of analgesic medications for >3 months;
• Inability to communicate due to severe dementia, language barriers, or terminal illness;
• History of central and/or peripheral nervous system disorders;
• Severe renal insufficiency (serum creatinine >442 μmol/L or requiring renal replacement therapy) or severe hepatic insufficiency (Child-Pugh class C);
• Allergy to local anesthetics.
• Expected to be transferred to ICU after surgery.

On the day of surgery, after the induction of general anesthesia, the study coordinator opened the corresponding envelope in the order of recruitment. Patients were randomly assigned to receive either EOIB or ESPB, which was performed preoperatively by an experienced anesthesiologist. The anesthesiologist was aware of the intervention, but all patients, data investigator and postoperative follow-up remained blinded to group assignment.