Intravenous dexamethasone fails to prolong psoas compartment block when assessed by objective pinprick sensory...

Recent studies have concluded that i.v. dexamethasone can prolong the duration of peripheral nerve blockade. We hypothesized that a 4 mg dose would equally prolong the duration of psoas compartment blocks (PCBs) when compared with 8 mg, and that both doses would prolong the duration when compared with placebo.

This was a prospective, randomized, placebo-controlled, dose-dependent, equivalency trial with 115 patients undergoing total hip arthroplasty. The patients received a PCB. Subsequently, 15 patients received i.v. normal saline (placebo), 50 patients received i.v. dexamethasone 4 mg, and 50 patients received i.v. dexamethasone 8 mg. The primary outcome was the duration in hours of PCB, determined by serial pinprick assessments. Secondary outcomes included pain scores, time to first analgesic, and opioid consumption. An intention-to-treat-analysis (ITA) and per-protocol analysis (PPA) were performed.

The ITA showed that block duration in the 4 and 8 mg groups was equivalent [mean (standard deviation), 18.5 h (8.0) vs 18.1 h (7.1)]. However, neither group differed from placebo [19.6 h (6.7), (4 mg vs placebo), P=0.97; (8 mg vs placebo), P=0.77)]. Postoperative pain scores and opioid consumption were not different between groups. Time to first analgesic was not different between the 4 and 8 mg groups, or the 4 mg and placebo groups. The 8 mg group, however, had a longer time to first analgesic (median of 533 vs 432 min, P=0.047) when compared with placebo, although the significance was not observed in the PPA (P=0.058).

I.V. dexamethasone did not prolong PCB when duration was objectively assessed, or decrease total opioid consumption. However, dexamethasone 8 mg prolonged the time to first analgesic.

NCT 02464176.