Comparison of the analgesic effects of different bupivacaine concentrations in continuous femoral block after total knee arthroplasty surgery

Abstract

Aim: In regional anesthesia practice, anesthesists’ goal must be to use the lowest effective concentration of local anesthetics to provide sufficient pain relief while minimizing side effects and complications. This study was designed to compare the analgesic efficacy of two different concentrations of bupivacaine (0.125% and 0.1%) in continuous femoral block for postoperative analgesia.

Method: In this study, fifty patients were enrolled, all of whom underwent femoral nerve block catheterization. The block procedure involved the administration of 30ml of bupivacaine solution at a concentration of 0.25%. Following a thirty-minute interval post-block application, patients underwent knee surgery under general anesthesia. During the closure of subcutaneous tissues, an additional 10ml of bupivacaine solution was injected through the catheter. Two groups were formed based on the concentration of the solution administered: Group(0.125%) received bupivacaine at a concentration of 0.125%, while Group(0.1%) received it at a concentration of 0.1%. Subsequently, upon arrival at the postoperative care unit, infusion through the catheter commenced at a rate of 10ml/h-1, maintaining the same concentrations for both groups. In addition to the nerve block, all patients were provided with intravenous Patient Controlled Analgesia (PCA) devices containing morphine for pain management. Throughout the postoperative period, sensory and motor block levels, Numerical Rating Scale (NRS) values for static and dynamic pain assessment, total morphine consumption, morphine demand, as well as any observed side effects and complications, were meticulously recorded for analysis.

Results: Postoperatively the NRSstatic values at 24th and 48th hours and NRSdynamic values at the 24th hour were higher in Group(0.1%) and it was statistically significant(p<0,007). And at 48th hour, morphine consumption was significantly higher in Group(0.1%) (p<0,05).

Conclusions: In our study, all patients across both experimental groups initially experienced satisfactory analgesia. However, within the 24-hour postoperative period, Group(0.1%) exhibited a decline in the quality of analgesia, necessitating increased utilization of rescue analgesics. This escalation in rescue analgesic use was associated with a higher incidence of adverse effects and reduced patient comfort levels within this group. Consequently, our findings indicate that the 0.125% concentration of bupivacaine yielded superior efficacy compared to the 0.1% concentration in the context of continuous femoral block administration.