Perineural Methylprednisolone Versus Dexamethasone as Ropivacaine Adjuvants in Popliteal Sciatic Nerve Block: A Randomized Double-Blind Superiority Trial

Abstract

Background. Single-shot popliteal sciatic nerve block (PSNB) gives analgesia for distal lower limb surgery but is time-limited. Dexamethasone, a non-particulate steroid, is the usual adjuvant. Particulate methylprednisolone acetate might act as a depot and prolong analgesia, but this is untested in PSNB.

Objective. To determine whether perineural methylprednisolone prolongs analgesia more than dexamethasone added to 0.5% ropivacaine in PSNB.

Methods. In this double-blind superiority trial, 36 adults (ASA I–III) having distal lower limb surgery were randomized 1:1 to 20 mL of 0.5% ropivacaine with dexamethasone 8 mg (Group D, n = 18) or methylprednisolone acetate 40 mg (Group M, n = 18). The primary outcome was duration of analgesia (time to NRS > 3 or rescue analgesia; superiority margin 4 hours), analyzed by Kaplan–Meier and log-rank tests. Secondary outcomes were onset, pain, rescue tramadol and adverse events.

Results. Mean duration of analgesia was 18.4 ± 3.2 hours in Group D and 19.1 ± 3.5 hours in Group M (difference 0.7 hours, 95% CI −1.6 to 3.0; log-rank p = 0.610), excluding the 4-hour margin. Sensory onset (median 14.5 vs. 15.0 minutes), motor onset (18.0 vs. 19.5 minutes) and NRS (median ≤ 2 at 12, 24 and 48 hours) did not differ. Rescue tramadol was needed by 2 of 18 and 1 of 18 patients (p = 1.000). No rebound pain, neurotoxicity or infection occurred.

Conclusion. Methylprednisolone did not prolong analgesia beyond dexamethasone in PSNB. Dexamethasone remains the preferred adjuvant; methylprednisolone may be considered where it is unavailable, pending larger trials.