Perineural or intravenous dexamethasone for adductor canal and iPACK blocks in total knee arthroplasty: A randomised trial

SUMMARY Introduction Total knee arthroplasty causes substantial postoperative pain. Combined adductor canal and interspace block between the popliteal artery and posterior knee capsule (iPACK) provides motor-sparing analgesia, but its duration is limited. We compared perineural and intravenous dexamethasone as adjuncts to these blocks in older patients undergoing primary total knee arthroplasty. Methods In this prospective, randomised, quadruple-blind, parallel-group trial, 90 patients aged 65–100 years were allocated equally to receive adductor canal and iPACK blocks with ropivacaine plus perineural dexamethasone 4 mg in total (2 mg per block), intravenous dexamethasone 4 mg, or placebo. The primary outcome was time to first rescue opioid analgesia within 48 h. Secondary outcomes included opioid consumption, pain scores, inflammatory markers, blood glucose, quadriceps strength, and neurological safety. Results Time to first rescue opioid analgesia differed between groups (log-rank p < 0.001). Median time (95% CI) was 4.5 (4.5–5.5) h with placebo, 13.9 (12.5–14.7) h with intravenous dexamethasone, and 18.5 (16.5 to not reached) h with perineural dexamethasone. The proportions remaining opioid-free at 48 h were 0%, 23.3%, and 36.7%, respectively. Opioid consumption and pain scores were lower with both dexamethasone routes than with placebo; perineural administration resulted in the lowest opioid consumption and lower pain scores than intravenous administration at later timepoints. Perineural dexamethasone was associated with lower postoperative neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios, whereas intravenous dexamethasone was associated with higher blood glucose. No motor weakness or nerve injury occurred. Discussion Perineural dexamethasone prolonged analgesia and reduced opioid requirements more than intravenous dexamethasone, without neurological or motor impairment. The inflammatory-marker findings were exploratory and do not establish independent clinical benefit.