Background and objectives Pain following total hip arthroplasty is significant, and effective analgesia is associated with an improvement in functional outcomes. Dexamethasone may facilitate the action of local anesthesia, but its role as an additive to a local infiltration analgesia (LIA) mixture in hip arthroplasty settings has not been investigated. We hypothesized that the addition of dexamethasone to local anesthetic infiltration improves analgesic outcomes following total hip arthroplasty.

Methods We performed a double-blind, randomized control trial of 170 patients undergoing total hip arthroplasty. Patients were randomized to receive LIA mixed with either 2 mL of saline 0.9% or 2 mL of dexamethasone 4 mg/mL. The primary outcome was 24 hours oral morphine consumption. Secondary outcomes included short-term and long-term analgesic and functional outcomes and adverse events.

Results 85 patients were included in each arm. 24 hours morphine consumption was similar between saline and dexamethasone groups, with a median (IQR (range)) of 75 (45–105 (0–240)) and 62.5 (37.5–102.5 (0–210)) mg, respectively (p=0.145). However, patients receiving dexamethasone had significantly reduced opioid consumption for their total in-hospital stay, but not at any other time points examined. Functional outcomes were similar between groups. The incidence of postoperative nausea and vomiting was reduced in patients receiving dexamethasone.

Conclusions The addition of 8 mg dexamethasone to LIA did not reduce 24 hours morphine consumption but was associated with limited improvement in short-term analgesic outcomes and a reduction in postoperative nausea and vomiting. Dexamethasone had no effect on functional outcomes or long-term analgesia.

Trial registration number NCT02760043