Group-based trajectory analysis of postoperative pain in epidural analgesia for video-assisted thoracoscopic surgery and risk factors of rebound pain.

BACKGROUND The current study aimed to investigate the patterns of postoperative pain trajectories over time and their associated risk factors in patients receiving video-assisted thoracoscopic surgery (VATS) and epidural analgesia (EA) for non-small cell lung cancer (NSCLC). METHODS This retrospective study was conducted at a tertiary medical center and included patients undergoing VATS for stage I NSCLC between 2011 and 2015. Maximal pain intensity was recorded daily during the first postoperative week. Group-based trajectory analysis was performed to categorize variations in pain scores over time. Associations between pain trajectory classification and amount of EA administered and length of hospital stay (LOS) after surgery were also evaluated. RESULTS A total of 635 patients with 4,647 pain scores were included in the analysis, and two postoperative pain trajectory groups were identified: group 1, mild pain trajectory (78%); and group 2, rebound pain trajectory (22%). Risk factors for rebound pain trajectory were a surgical time longer than 3 hours (odds ratio, OR: 1.97; 95% confidence interval, CI: 1.27 - 3.07), female sex (OR: 1.62; 95% CI: 1.04 - 2.53) and higher pain score on postoperative day 0 (OR: 1.21; 95% CI: 1.08 - 1.36, linear effect). Although group 2 had a longer LOS (p < 0.001), they did not receive more EA than group 1 (p = 0.805). CONCLUSION Surgical time, sex and pain intensity after surgery were major determinants of rebound pain trajectory, and more aggressive pain control strategies should be considered in high-risk patients.