Application of dexamethasone as an adjuvant to the local anesthetic in the performance of a US-guided femoral block for postoperative analgesia on patients after total knee joint replacement

Introduction: The article discusses the use of dexamethasone as an adjuvant to local anesthetic solution for ultrasound (US)-guided femoral nerve block in patients after total knee joint replacement. A literature review on the clinical use of other adjuvants is also presented. Design: This was a clinical prospective randomized study. Aim: The aim of this article is to investigate the effect of dexamethasone adjuvant on the local anesthetic solution when performing a US-guided femoral block in patients after total knee joint replacement. Methods: The study included 53 patients, randomized into two groups :  Group 1: single shot femoral nerve block (FNB) + constant infusion through a perineural catheter 15 mL bolus (ropivacaine 0.5%/levobupivacaine 0.375%) with a subsequent infusion of 5-9 mL per hour, including 20 patients; Group 2: single shot FNB  20 mL bolus (ropivacaine 0.5%/levobupivacaine 0.375%) +/- dexamethasone 4 mg, including 33 patients.  In Group 2, 2 subgroups were formed: patients with single shot FNB with chirocain - 10 patients; patients with single shot FNB with ropivacaine - 23 patients. Of these, 15 patients were fasted with single shot FNB  with ropivacaine + dexamethasone 4 mg, and 8 patients with pure ropivacaine. Evaluation of effective control of pain relief symptoms was done on 2nd, 4th, 6th, 12th, 18th, 24th, and 36th hours postoperatively according to the Visual Analogue Scale (VAS). Results: No statistically significant difference in VAS scores was observed between the two groups in the 2nd, 6th, 12th, 18th and 36th hours. Such was found only in the 24th hour. We did not detect statistically significant benefits of this adjuvant. We do not have clinically registered adverse drug reactions (ADRs). We have not established a correlation between these occurrences and the use of dexamethasone. Conclusion: Although our results correspond to those of authors who refute the benefits of dexamethasone as an adjuvant to the peripheral nerve block (PNB), we believe, based on clinical observation data, that it actually attenuated reversible hyperalgesia (patients did not report abruptly, acute, sudden onset of pain), therefore prolongation of the analgesic effect was observed until the 18th, 20th postoperative hour.