Dexamethasone as an adjuvant for peripheral nerve blockade: a randomised, triple-blinded crossover study in volunteers

Abstract

Background: The efficacy of dexamethasone in extending the duration of local anaesthetic block is uncertain. In a randomised controlled triple blind crossover study in volunteers, we tested the hypothesis that neither i.v. nor perineurally administered dexamethasone prolongs the sensory block achieved with ropivacaine.

Methods: Ultrasound-guided ulnar nerve blocks (ropivacaine 0.75% wt/vol, 3 ml, with saline 1 ml with or without dexamethasone 4 mg) were performed on three occasions in 24 male volunteers along with an i.v. injection of saline 1 ml with or without dexamethasone 4 mg. The combinations of saline and dexamethasone were as follows: control group, perineural and i.v. saline; perineural group, perineural dexamethasone and i.v. saline; i.v. group, perineural saline and i.v. dexamethasone. Sensory block was measured using a VAS in response to pinprick testing. The duration of sensory block was the primary outcome and time to onset of sensory block the secondary outcome.

Results: All 24 subjects completed the trial. The median [inter-quartile range (IQR)] duration of sensory block was 6.87 (5.85-7.62) h in the control group, 7.37 (5.78-7.93) h in the perineural group and 7.37 (6.10-7.97) h in the i.v. group (P=0.61). There was also no significant difference in block onset time between the three groups.

Conclusion: Dexamethasone 4 mg has no clinically relevant effect on the duration of sensory block provided by ropivacaine applied to the ulnar nerve.

Clinical trial registration: DRKS, 00014604; EudraCT, 2018-001221-98.

Keywords: dexamethasone; local anaesthetics; regional anaesthesia; ropivacaine; ulnar nerve block; ultrasound-guided.

Fig 1

High-resolution ultrasound image of the anatomical position of the ulnar nerve at the forearm between the superior flexor digitorum muscle (SFDM), profoundus flexor digitorum muscle (PFDM), and the flexor carpi ulnaris muscle (FCUM). The ulnar nerve (indicated by the arrow) appears at this anatomical position as a triangular structure and was the standardised site of nerve blockade.

Fig 2

High-resolution ultrasound image of the ulnar nerve blockade via an in-plane needle guidance technique. The vertical arrow indicates the shaft of the needle and the horizontal arrow indicates the tip of the needle. The administered local anaesthetic (with or without dexamethasone or saline) appears as a hypoechoic area around the hyperechoic nerve.

Fig 3

Sensory block durations for each volunteer showing the effects of perineural or i.v. dexamethasone. Although the repeated measures are linked for the purposes of presentation, the order was randomised.

Fig 4

Sensory block onset times for each volunteer showing the effects of perineural or i.v. dexamethasone. Although the repeated measures are linked for the purposes of presentation, the order was randomised.