A double-blind randomized controlled trial comparing dexamethasone and clonidine as adjuvants to a ropivacaine sciatic popliteal block for foot surgery

Background and aims: A popliteal block is effective in managing postoperative pain for foot surgery, but since the duration of analgesia is limited following a single-shot popliteal fossa block technique, methods to prolong effective postoperative analgesia are mandatory. The aim of this study was to assess the effect of adjuvants to ropivacaine on the duration of sensory and motor block. Methods: In this double-blind randomized placebo-controlled study, we evaluated the - analgesic effect of clonidine or dexamethasone (DXM) when added to ropivacaine for hallux valgus - surgery. After obtaining institutional ethics research board approval and written informed consent, a total of 72 patients were randomly allocated. Fifty-seven of these patients were statistically analyzed. All patients received an ultrasound-guided single-shot popliteal fossa block with 30 mL of ropivacaine 0.75%, supplemented with saline, clonidine 100 mu g, or DXM 5 mg. The primary end point was time to first pain sensation. Secondary end points were time to complete sensory and motor block regression. Results: Compared to saline, duration to first pain sensation was prolonged by 9 hours (mean +/- standard deviation: 31 +/- 9 hours) (42%) in the DXM group (P= 0.024) and by 6 hours (28 +/- 10 hours) (27%) in the clonidine group (P= 0.024). Compared to saline, DXM prolonged both complete sensory and motor blockade by 12 hours (25 +/- 7 hours) (46%) and 13 hours (36 +/- 6 hours) (55%), respectively, while clonidine prolonged complete sensory and motor blockade by 7 hours (30 +/- 7 hours) (27%) and 2 hours (22 +/- 5 hours) (10%), respectively. DXM prolonged sensory block regression time by 6 hours (21 +/- 7 hours) (41%) and clonidine by 2 hours (17 +/- 6 hours) (13%) compared to the control group (P= 0.006). Similarly, DXM prolonged motor block regression by 7 hours (25 +/- 7 hours) (46%) and clonidine by 4 hours (21 +/- 4 hours) (19%) (P< 0.0001). Conclusion: Addition of DXM and clonidine to ropivacaine significantly prolonged the duration of postoperative sensory and motor block.