BACKGROUND: Pain caused by chest tube placed after uniportal video-assisted thoracoscopic surgery (UVATS) is often neglected. Ropivacaine can be used to alleviate pain related to the chest tube, but the current lowest effective concentration of ropivacaine remains unclear. METHODS: To investigate the analgesic effect of administering two different concentrations of ropivacaine into the pleural cavity via pleural drainage tube bypass after UVATS. Ninety patients were randomly divided into three groups: Control group (PCIA only), Low-dose group (PCIA combined with intrathoracic infusion of 200 ml 0.25% ropivacaine), Medium-dose group (PCIA combined with intrathoracic infusion of 200 ml 0.5% ropivacaine). The analysis included Visual Analogue Scale (VAS) scores for chest tube-related pain and surgical incision pain at 6 h, 12 h, 24 h, and 48 h post-operation for each group. Compare incidence of adverse reactions (respiratory depression, hypotension, nausea/vomiting, arrhythmia, dizziness) within 48 h. RESULTS: Compared to the control group, both 0.25% and 0.50% ropivacaine effectively reduced chest tube-related pain (P <
0.001) and surgical incision pain (P <
0.001) at 6 h, 12 h, 24 h, and 48 h postoperatively. However, no significant differences were observed between the two concentrations of ropivacaine in alleviating rest and cough pain related to the chest tube (P >
0.05) or surgical incision (P >
0.05) within 48 h postoperatively. Adverse reaction rates were similar among groups within 48 h postoperatively (P = 0.383). CONCLUSION: The analgesic effect of ropivacaine infusion with concentrations of 0.25% and 0.50% administered via intrathoracic pumps for chest tube-related pain after UVATS showed no significant difference, but both were superior to the sole use of PCIA. REGISTRATION: Chinese Clinical Trial Registry ChiCTR2200065184.