Effect of intravenous dexamethasone on the duration of postoperative analgesia for popliteal sciatic nerve block: a randomized, double-blind, placebo-controlled study

Intravenous (IV) dexamethasone prolongs the duration of peripheral nerve block; however, there is little available information about the optimal effective dose. This study aimed to evaluate the effects of three different doses of IV dexamethasone on the duration of postoperative analgesia to determine the optimal effective dose for sciatic nerve block. Patients scheduled for foot and ankle surgery were randomly assigned to receive normal saline or IV dexamethasone 2.5 mg, 5 mg, or 10 mg. Ultrasound-guided popliteal sciatic nerve block was performed using 0.75% ropivacaine (20 mL) before general anesthesia. The duration of postoperative analgesia was the primary outcome, and pain scores, use of rescue analgesics, block onset time, incidence of postoperative nausea and vomiting, adverse effects, and patient satisfaction were assessed as secondary outcomes. Compared with the control group, the postoperative analgesic duration of sciatic nerve block was prolonged in groups receiving IV dexamethasone 10 mg (P < 0.001), but not the groups receiving IV dexamethasone 2.5 mg or 5 mg. The use of rescue analgesics was significantly different among the 4 groups 24 h postoperatively (P = 0.004) and similar thereafter. However, pain scores were not significantly different among the 4 groups 24 h postoperatively. There were no statistically significant differences in other secondary outcomes among the 4 groups. This study demonstrated that compared with control, only IV dexamethasone 10 mg increased the duration of postoperative analgesia following sciatic nerve block for foot and ankle surgery without occurrence of adverse events.