Dexamethasone and peripheral nerve blockade

“Dexamethasone as an adjuvant for peripheral nerve blockade: a randomised, triple-blinded crossover study in volunteers” Marhofer, P et al. British Journal of Anaesthesia, 122 (4): 525e531 (2019)

Background

  • No ideal agent exists for use in peripheral nerve blockade (one which would allow motor and sensory blockade intraoperatively and then prolonged sensory blockade postoperatively).
  • Therefore adjuncts have been added to prolong postoperative sensory blockade.
  • Dexamethasone is one such adjunct.

Rationale

  • Efficacy of dexamethasone administered perineurally or systemically has been evaluated in 7 recent systematic reviews and meta-analyses.
  • Authors suggest low quality of trials and heterogeneity mean no reliable conclusions can be drawn regarding efficacy of perineural dexamethasone in combination with local anaesthetics.
  • Therefore decided to conduct their own study.

Method

  • Volunteer study
  • Randomised, triple-blinded crossover study
  • Assessing effects of dexamethasone as an additive to ropivicaine in a standardised peripheral nerve block.
  • Ethics approval obtained.
  • Male volunteers aged 18 – 55 with BMIs 18-35 recruited.
  • Underwent Ulnar Nerve blockade on non-dominant hand by single investigator. 
  • Three study groups: control, perineural group, i.v. group.

Assessment of sensory block

VAS (0-100mm) in response to pinprick testing over the hypothenar area. 

Results

  • 24 volunteers, 72 blocks. 19 volunteers had blocks on left arm, 5 on right arm. 
  • Median age 30, mean BMI 23. 
  • No difference in duration.
  • No difference in outcome.
  • Full recovery of sensation in all patients for each block and no other sequelae.

Discussion

  • No new local anaesthetics in last 20 years, therefore adjuvants been investigated.
  • Dexamethasone has been heavily investigated but with heterogenous study designs and no uniformity in practice.
  • Clinical studies leave gaps in assessment of duration.
  • This study is highly standardised and employed crossover design. The dose of dexamethasone  and concentration of local anaesthetic allows full blockade of a peripheral nerve.
  • Well powered: 99% for a difference in duration of block of 4  hours and 98% for a difference of 2 hours.
  • Dexamethasone may have an effect on neural blood flow and therefore may be efficacious in chronic pain due to the inflammatory component, therefore future studies should focus on this.

Group discussion/overall thoughts

  • Not applicable to our practice as no surgical stimulus and fit and well people assessed.
  • Only used ropivacaine not other local anaesthetics, conceivably differing effects of dexamethasone with other local anaesthetics.
  • The paper didn’t investigate higher doses of dexamethasone than 4mg and the potential effects.
  • There was no assessment of motor blockade and effect of dexamethasone on this.
  • They chose 4 hours as clinically significant, however it would be interesting to see if there was a block duration difference of 1 hour and how well the paper was powered for this.


Summary by Dr Anish Amlani

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s