BackgroundCompared with open surgery, laparoscopic liver resection is a minimally invasive surgical technique. However, a number of patients experience moderate-to-severe postoperative pain after laparoscopic liver resection. This study aims to compare the postoperative analgesic effects of erector spinae plane block (ESPB) and quadratus lumborum block (QLB) in patients undergoing laparoscopic liver resection.MethodsOne hundred and fourteen patients undergoing laparoscopic liver resection will be randomly allocated to three groups (control, ESPB, or QLB) in a 1:1:1 ratio. In the control group, participants will receive systemic analgesia consisting of regular NSAIDs and fentanyl-based patient-controlled analgesia (PCA) according to the institutional postoperative analgesia protocol. In the two experimental groups (ESPB or QLB group), the participants will receive preoperative bilateral ESPB or bilateral QLB in addition to systemic analgesia according to the institutional protocol. ESPB will be performed at the 8th thoracic vertebra level with ultrasound guidance before surgery. QLB will be performed in the supine position on the posterior plane of the quadratus lumborum with ultrasound guidance before surgery. The primary outcome is cumulative opioid consumption 24 h after surgery. Secondary outcomes are cumulative opioid consumption, pain severity, opioid-related adverse events, and block-related adverse events at predetermined time points (24, 48, and 72 h after surgery). Differences in plasma ropivacaine concentrations in the ESPB and QLB groups would be investigated, and the quality of postoperative recovery among the groups will be compared.DiscussionThis study will reveal the usefulness of ESPB and QLB in terms of postoperative analgesic efficacy and safety in patients undergoing laparoscopic liver resection. Additionally, the study results will provide information on the analgesic superiority of ESPB versus QLB in the same population.Trial registrationProspectively registered with the Clinical Research Information Service on August 3, 2022; KCT0007599.