Sodium bicarbonate alkalinization of local anesthetics for peripheral nerve blocks: A systematic review

Alkalinization of local anesthetic solutions is intended to increase the non-ionized fraction of the local anesthetic, but its clinical benefit in onset time, duration, or block quality in peripheral nerve blocks remains uncertain.

PubMed and Embase were searched to October 2025 with no date restrictions. Eligible studies were comparative clinical studies evaluating sodium bicarbonate alkalinization versus non-alkalinised solutions for single-shot peripheral nerve blocks, reporting onset time, duration, or block quality. Risk of bias was assessed using design-appropriate tools and a structured narrative synthesis was performed.

A total of 422 records were identified; after deduplication, screening, and eligibility assessment, 18 studies were included. Thirteen of 16 studies providing group-comparable onset data found faster onset in at least one outcome after alkalinization, with more consistent findings for motor than sensory onset. Effects on block duration were heterogeneous and block quality findings were inconsistent. Risk of bias was predominantly some concerns; incomplete final pH reporting in several studies limited intervention fidelity.

This review shows that alkalinization may accelerate onset time in peripheral nerve blocks, particularly with lidocaine (lignocaine) and most consistently for motor onset, but the effect is variable, agent-specific, and supported by evidence of low-to-moderate certainty. The available evidence supports a selective rather than universal approach to alkalinization.

PROSPERO (CRD420251248335).