Purpose of review: The duration of single-injection regional anaesthesia is limited due to the inherent pharmacological properties of local anaesthetics. The ideal duration of a regional anaesthesia block lasting for the first 24 h postoperatively can be stated, while a residual analgesic effect thereafter is desirable.The aim of this review is to present current options to prolong the duration of action of single-injection peripheral regional anaesthesia in the ambulatory setting. Secondly, this review outlines and discusses the latest evidence regarding the clinical use of adjuvants and sustained-release local anaesthetics.
Recent findings: Extended-release formulations of local anaesthetics such as liposomal bupivacaine have been developed to prolong regional anaesthesia up to 96 h. Recent studies, however, show that the actual effects remain far behind expectations and that the efficacy is only marginally better than bupivacaine hydrochloride.Adjuvants to local anaesthetics have been studied extensively with heterogenous results. Dexamethasone and alpha-2 agonists range among the most effective measures to prolong single-injection nerve blocks.Continuous nerve blocks and catheter techniques may prolong regional anaesthesia very effectively, but are less cost-effective regarding block procedure, postoperative care and handling logistical issues especially in ambulatory surgery.
Summary: In conclusion, adjuvants are the recommended measure to prolong regional anaesthesia where needed. With good evidence supporting it, dexamethasone is the most effective adjuvant, followed by dexmedetomidine. Both have few side effects and a favourable safety profile. However, a preferable duration of analgesia lasting for the first 24 h postoperatively is still not reliably achievable.
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