DEX it or not? Use of dexamethasone as an adjunct to peripheral nerve blocks
Fernando Alquicira-Macedo, MD and Gulshan Doulatram, MD
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The addition of adjuncts to peripheral nerve blocks can achieve prolongation of blockade. Perineural use of dexamethasone as an adjunct to local anesthetics with brachial plexus blocks has been shown to prolong the intensity and duration of the blocks.1 However, there is a concern for neurotoxicity with perineural dexamethasone as well as some of its preservatives.2-6 Despite such concerns, there is some data suggesting that dexamethasone may actually be neuroprotective.7 Intravenous dexamethasone is equivalent to perineural dexamethasone in prolonging the analgesic duration of a single shot of interscalene brachial plexus block in some studies.11,23 However, an exhausting literature review on this has led to the conclusion that a direct comparison amongst the studies has been difficult predominantly due to varying definitions of analgesia duration. Some studies had confounding additives such as epinephrine that could prolong the block as well as pose a neurotoxic risk.8,12,14-16 The use of different local anesthetics and locations of the blocks have also made the correlation difficult to make.
In summary, intravenous dexamethasone prolongs analgesia duration of peripheral nerve blocks.17,18 It does appear that perineural administration of dexamethasone achieves slightly longer prolongation than the intravenous route.9,10, 12-14 The duration of extended relief may not be attractive in light of the fact that there is a possible concern for the risk of neurotoxicity.2-6 An intravenous dose of dexamethasone of at least 0.1 mg/kg should be used as it was found to have a reduction in postoperative pain and opioid consumption.21,22 Doses less than 2.5 mg are not preferred due to lack of effect.17 If perineural dexamethasone is to be used, we suggest using lower doses of 1-2 mg to minimize the risk of neurotoxicity.2,19,20 Furthermore, the dexamethasone needs to be preservative free as certain preservatives have been directly linked to neurotoxicity.3,4 More research is needed to verify the possible role of dexamethasone, route of administration, and its neuroprotective versus neurotoxic effects.