• Natanael Pietroski Dos Santos, Vanessa de Paula Silva, Guilherme Stéfano da Silva Oliveira, Victor Cardoso Musacchio, and Vanessa Henriques Carvalho.
• FMABC University Center, Santo André, SP, Brazil pietroski@gmail.com.
• Reg Anesth Pain Med. 2025 Jan 8.

Background/ImportanceLocal anesthetic (LA) mixtures are used in peripheral nerve blocks (PNB) to improve onset, though study results remain conflicting.ObjectiveThis systematic review and meta-analysis compared the efficacy outcomes of long-acting LA to their mixture with shorter-acting LA in ultrasound-guided PNB. The primary outcome was sensory block onset.Evidence ReviewWe searched WoS, Scopus, MEDLINE, EMBASE, BVS/LILACS, and Cochrane databases from 1998 to 2024 for randomized controlled trials (RCTs). We conducted a random-effects meta-analysis, evaluated the risk of bias (RoB) with RoB 2.0, performed sensitivity analyses, assessed non-reporting bias with DOI plots and Luis Furuya-Kanamori index, and evaluated strength of evidence with Grading of Recommendations Assessment, Development and Evaluations.FindingsWe included 10 RCTs (516 participants). Mixture of LA may have no effect on sensory block onset (mean difference (MD) -1.62 min, 95% CI: -4.04 to 0.81; I2=81.50%, 95% CI: 62.82% to 90.80%; prediction interval (PI)=-7.78 to 4.55; very low certainty) and motor block onset (MD -5.60 min; 95% CI: -14.54 to 3.33, I2=98.89%, 95% CI: 98.50% to 99.18%; PI=-31.90 to 20.69; very low certainty), while it may reduce the duration of sensory block (MD -2.16 hours, 95% CI: -4.16 to -0.17; I2=90.77%, 95% CI: 84.22% to 94.60%; PI=-7.24 to 2.92; very low certainty).ConclusionsLA mixtures may not affect sensory and motor block onset in ultrasound-guided PNB but could shorten the duration of sensory blockade.© American Society of Regional Anesthesia & Pain Medicine 2025. No commercial re-use. See rights and permissions. Published by BMJ Group.

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