Dexamethasone, but Not Esketamine, Reduces Rebound Pain After Interscalene Nerve Block: A Randomized Factorial Trial

Rebound pain following peripheral nerve block resolution is a distressing phenomenon that impairs recovery and commonly arises at night when treatment options are limited.

To evaluate whether intravenous esketamine and/or dexamethasone, as adjuvants to interscalene ropivacaine block, reduce rebound pain after arthroscopic shoulder surgery.

A patient- and outcome assessor-blinded, randomized, controlled, 2×2 factorial clinical trial.

A single tertiary-care academic hospital.

A total of 160 adult patients undergoing arthroscopic shoulder surgery under general anaesthesia with single-shot interscalene brachial plexus block.

Patients were randomized to receive intravenous combinations of esketamine-placebo, placebo-dexamethasone, esketamine-dexamethasone, or placebo-placebo, in addition to ropivacaine block after induction of general anaesthesia and before surgical incision.

Co-primary outcomes were: (1) the increase in pain score from before to after the ISB resolved; and (2) the incidence of severe rebound pain, defined as numerical rating scale (NRS) pain score ≥7.

All 160 patients completed the trial. Rebound pain occurred in 32% of patients, with no interaction between esketamine and dexamethasone. The pain score increased by 6.2 ± 2.5 in the placebo-placebo group versus 4.4 ± 2.5 in the esketamine-dexamethasone group (difference -1.8; 95% CI -2.9 to -0.7; P = 0.002). Dexamethasone significantly reduced the pain score increase compared to placebo (-1.7; 95% CI -2.8 to -0.6; P = 0.003), while esketamine alone did not. Severe rebound pain occurred in 22/80 (27%) of patients receiving esketamine versus 26/80 (32%) without (RR 0.84; 95% CI 0.50 to 1.41; P = 0.459), and in 18/80 (22%) of patients receiving dexamethasone versus 29/80 (36%) without (RR 0.62; 95% CI 0.38 to 0.89; P = 0.016).

Intravenous dexamethasone, but not esketamine (low dose), significantly reduced the incidence and severity of rebound pain following interscalene nerve block.

Chinese Clinical Trial Registry (ChiCTR2300072416).