Novel analgesic adjuncts for brachial plexus block: a systematic review.

This article reviews current evidence for the efficacy of adding novel analgesic adjuncts to brachial plexus block, the goal of which is to prolong analgesic effect without the disadvantage of systemic side effects or prolonged motor block. It may also allow for a reduction in the total dose of local anesthetic used. Novel adjuncts studied to date include opioids, clonidine, neostigmine, and tramadol. Twenty-four studies were reviewed and assessed by using specific inclusion criteria, and only those studies satisfying these criteria were included in the final assessment. Satisfactory studies were then assessed for inclusion of a systemic control group to determine peripheral effect, as opposed to possible systemic effect, of an adjunct administered peripherally. Evidence regarding the analgesic benefit of opioid adjuncts remains equivocal and more evidence is required before their routine use can be recommended. Clonidine appears to have significant analgesic benefit and to cause minimal adverse effects when used in doses up to 150 microg. Data regarding other drugs, such as tramadol and neostigmine, are not sufficient to allow for any recommendations, and further studies are required.