Effect of epidural analgesia on the neutrophil-to-lymphocyte ratio after thoracic surgery: a large-scale retrospective cohort study

Background: Postoperative analgesia is crucial for recovery after thoracic surgery. The neutrophil-to-lymphocyte ratio (NLR) serves as an indicator of systemic inflammatory status. This study aimed to evaluate the impact of different postoperative analgesia modalities on NLR and recovery outcomes in patients undergoing thoracic surgery. Methods: We retrospectively analyzed data from 1,099 patients who underwent thoracic surgery between January 2020 and July 2024 and received patient-controlled analgesia (PCA). Based on the pain relief method employed, the patients were categorized into two groups: the patient-controlled epidural analgesia (PCEA) group (n=533) and the patient-controlled intravenous analgesia (PCIA) group (n=566). The primary outcome was the NLR at 48 hours postoperatively. Secondary outcomes included postoperative pain scores and recovery parameters. Results: The postoperative NLR at 48 hours was significantly lower in the PCEA group (4.75) than in the PCIA group (5.90) (P