Combination of shorter and longer-acting LA vs. longer-acting LA for brachial plexus block: Systematic review and meta-analysis of randomized clinical trials

Abstract

Background: Combining shorter-acting local anesthetics (LA) with longer-acting ones should theoretically ensure a quick-onset block without compromising on the duration of blockade. We wanted to perform a review of literature evaluating combination of shorter-acting and longer-acting LA in comparison to long-acting LA alone when used for brachial plexus blocks in terms of block characteristics and efficacy.

Methods: Primary literature searches were performed in PubMed, Embase, and the Cochrane databases from their inception through October 26, 2023. Randomized clinical trials (RCTs) utilizing any combination of mixtures of a shorter and longer-acting LA (combination LA) compared to any single long-acting LA for brachial plexus block in adults were selected. The primary outcomes of interest were sensory and motor block onset times while secondary outcomes included duration of blockade, duration of analgesia and, the need for conversion to general anesthesia (GA).

Results: A total of 4209 primary references were reviewed and after exclusions, 11 RCTs were included for data extraction. Pooled data showed that compared to long-acting LA, combination of LAs did not reduce the sensory onset time [MD (95 % CI) -0.44 min (-0.89; 0.02)] nor the motor onset [MD (95 % CI): 0.01 (-1.30 to 1.32)]. The combination group showed a shorter duration of sensory and motor blockade without differences in other secondary outcomes.

Conclusion: Our meta-analysis of RCTs indicate that combination of shorter and long acting LAs did not provide benefit in terms of onset time while leading to notably shorter durations of sensory and motor blockade compared to longer acting LA alone when used in brachial plexus blocks. PROSPERO registration no.: CRD42023476579.

Keywords: Anesthesia, conduction; Anesthetics, local; Brachial plexus block; Regional anesthesia.