The effects of addition of dexamethasone to bupivacaine during ultrasound-guided femoral nerve block for postoperative analgesia in patients undergoing total knee replacement surgery

Introduction
The goal of knee replacement is to relieve pain, improve quality of life, and maintain or improve knee function. The procedure is performed on people of all ages. However, a significant number of patients experience persistent pain and functional limitations following knee replacement, with ~20% of patients reporting unfavorable pain outcomes.
Materials and methods
Our study was done after obtaining Assiut University Hospital Ethical Committee approval and informed written consent from the patients who were admitted to the Department of Orthopedics in Assiut University Hospital and were planned for total knee replacement surgery in the period from December 2015 until July 2017. Our study included 60 patients aged between 18 and 80 years. Patients were randomized into two groups: group B (30 ml of 0.25% bupivacaine) and group BD (28 ml of 0.25% bupivacaine + 2 ml dexamethasone 8 mg).
Results
The current study showed that preemptive addition of 8 mg dexamethasone to 30 ml bupivacaine 0.25% for femoral nerve block guided with ultrasound for total knee replacement surgery on side of operation resulted in a reduction of visual analog scale pain score over the postoperative 24 h prolonged the duration of the block, required longer time till first analgesic, and led to more patient satisfaction and less incidence of nausea and vomiting. As seen in our results that the visual analog scale was significantly low starting from 4 h (1 ± 0 vs. 1.13 ± 0.35; < 0.001), 8 h (1.07 ± 0.25 vs. 1.67 ± 0.71; < 0.001), 12 h (1.23 ± 0.43 vs. 1.97 ± 0.67; = 0.789), 16 h (1.67 ± 0.71 vs. 2.37 ± 0.67; = 0.563), 20 h (1.9 ± 0.76 vs. 2.87 ± 0.82; = 0.774), and 24 h (2.03 ± 0.76 vs. 2.97 ± 0.61; = 0.052).
Conclusion
Our study results demonstrate that the addition of dexamethasone to bupivacaine suggestively prolongs its analgesic effect postoperatively. These results are consistent with the trend of previous studies using dexamethasone as an additive to local anesthetic in peripheral nerve blocking.