Add on Perineural dexamethasone to bupivacaine may prolong ulnar nerve block

Healthy participants who received perineural dexamethasone in addition to bupivacaine experienced a longer ulnar nerve block than those who received a placebo, says an article published in Anesthesiology.

When used as an adjuvant to peripheral nerve blocks in patients having surgery, dexamethasone delivered perineurally or systemically prolongs block duration. It is uncertain whether the block-prolonging effects of perineural injection result from a direct perineural mechanism of action or from the systemic analgesic effects of dexamethasone. The purpose of this study by Mathias Maagaard and colleagues was to test the hypotheses that systemic dexamethasone is noninferior to perineural dexamethasone and that both perineural and systemic dexamethasone as adjuncts to bupivacaine enhance the duration of an ulnar nerve block compared to bupivacaine alone.

On two trial days, the authors administered bilateral ulnar nerve blocks with 3 ml bupivacaine 5 mg/ml in 16 healthy volunteers. On one trial day, subjects received adjunct treatment with 1 ml dexamethasone 4 mg/ml + 1 ml saline (perineural condition) in one arm and 2 ml saline in the other arm (systemic condition, through absorption and redistribution of the contralaterally administered perineural dexamethasone) in the other arm (lidocaine condition) on the other trial day. The duration of the sensory nerve block was measured using temperature discrimination as the primary result.

The key findings of this study were:

The average sensory block duration for the perineural condition was 706 94 minutes, 677 112 minutes for the systemic condition, and 640 121 minutes for the placebo condition.

Perineural dexamethasone prolonged sensory nerve block duration compared to placebo (mean difference 66 min (95% CI, 23 to 108).

The length of the block was comparable between systemic dexamethasone & placebo (mean difference 36 min; 95% confidence interval, -30 to 103).

Reference:

Maagaard, M., Stormholt, E. R., Nielsen, L. F., Bærentzen, F., Danker, J., Zachodnik, J., Jæger, P., Mathiesen, O., & Andersen, J. H. (2023). Perineural and Systemic Dexamethasone and Ulnar Nerve Block Duration: A Randomized, Blinded, Placebo-controlled Trial in Healthy Volunteers. In Anesthesiology (Vol. 138, Issue 6, pp. 625–633). Ovid Technologies (Wolters Kluwer Health). https://doi.org/10.1097/aln.0000000000004557