Combined Dexamethasone and Dexmedetomidine as Adjuncts to Popliteal and Saphenous Nerve Blocks in Patients Undergoing Surgery of the Foot or Ankle: A Randomized, Blinded, Placebo-controlled, Clinical Trial

Background Both dexamethasone and dexmedetomidine increase the duration of analgesia of peripheral nerve blocks. The authors hypothesized that combined intravenous dexamethasone and intravenous dexmedetomidine would result in a greater duration of analgesia when compared with intravenous dexamethasone alone and placebo. Methods The authors randomly allocated participants undergoing surgery of the foot or ankle under general anesthesia and with a combined popliteal (sciatic) and saphenous nerve block to a combination of 12 mg dexamethasone and 1 mcg/kg dexmedetomidine, 12 mg dexamethasone, or placebo (saline). The primary outcome was the duration of analgesia measured as the time from block performance until the first sensation of pain in the surgical area as reported by the participant. The authors pre-defined a 33% difference in the duration of analgesia as clinically relevant. Results A total of 120 participants from 2 centers were randomized and 119 analyzed for the primary outcome. The median [IQR] duration of analgesia was 1572 minutes [1259 to 1715] with combined dexamethasone and dexmedetomidine, 1400 minutes [1133 to 1750] with dexamethasone alone, and 870 minutes [748 to 1138] with placebo. Compared with placebo, the duration was greater with combined dexamethasone and dexmedetomidine (difference 564 minutes, 98.33% CI 301 to 794, p < 0.001) and with dexamethasone (difference 489 minutes, 98.33% CI 265 to 706, p < 0.001). The prolongations exceeded our pre-defined clinically relevant difference. The duration was similar when combined dexamethasone and dexmedetomidine was compared with dexamethasone alone (difference 61 minutes, 98.33% CI -222 to 331, p = 0.614). Conclusion Dexamethasone with or without dexmedetomidine increased the duration of analgesia in patients undergoing surgery of the foot or ankle with a popliteal (sciatic) and saphenous nerve block. Combined dexamethasone and dexmedetomidine did not increase the duration of analgesia when compared with dexamethasone.