Rebound pain and related factors in patients undergoing femoral nerve block for postoperative pain control in total knee arthroplasty

Introduction and Aim: Rebound pain is defined as sudden, severe pain occurring within 8-24 hours after a peripheral nerve block, lasting approximately 2 hours, and not alleviated by tramadol treatment. The pain is typically described as a burning sensation. In this study, we aimed to determine the incidence of rebound pain in patients undergoing femoral nerve block (FNB) for postoperative pain control in total knee arthroplasty (TKA) performed under spinal anesthesia. Additionally, we aimed to assess the predictability of rebound pain using inflammation markers such as neutrophil-to-lymphocyte ratio (NLR) and systemic inflammation index (SII) and to identify factors associated with rebound pain. Materials and Methods: A total of 120 patients scheduled for TKA surgery were included in the study. In our prospective, observational study, preoperatively,ba femoral nerve block was administered with 0.25% bupivacaine in adose of 20 ml. Patients for whom the block was successful underwent surgery under spinal anesthesia. Routine ASA monitoring and follow-up were conducted. Postoperatively, all patients received intravenous tramadol through a patient controlled analgesia (PCA) device. NSAIDs were planned as rescue analgesics. Preoprative NLR and SII values were calculated, and postoperative VAS were evaluated during movement and rest, along with tramadol consumption, the need for additional analgesics, side effects, Bromage score, and the incidence and duration of rebound pain. Data analysis was performed using IBM SPSS 27.0 (Armonk, NY: IBM Corp.) statistical package program. Results: Rebound pain was observed in 30,8% of the patients. The average duration of rebound pain was found to be 74.7 ± 29.5 minutes. No statistically significant difference was found between the preoperative values of neutrophil-to-lymphocyte ratio (NLR) and systemic inflammation index (SII)-inflammatory markers thought to be associated with rebound pain-between patients who experienced rebound pain and those who did not. However, although there was no significant difference in additional analgesic use, patients with rebound pain had significantly worse satisfaction and sleep quality compared to those without pain. Conclusion: No relationship was found between preoperative NLR and SII values and rebound pain, which has become a popular topic with the increasing use of peripheral nerve blocks in recent years. Additionally, no differences were observed in VAS scores, postoperative tramadol consumption, or additional analgesic use. We believe that further studies involving different age groups, various surgical procedures and different peripheral nerve blocks are needed to better predict rebound pain. Keywords: Total knee artroplasty, Postoperative analgesia, Femoral nerve block, Rebound pain, İnflammatory markers