Background Variation in clinical practice is often considered unwarranted when it does not reflect patient preference or evidence-based medicine. Complications from regional anesthesia such as nerve injury and systemic toxicity are dose dependent. It is currently unclear if there is significant variation with the dosing of local anesthetics (LA) in the context of the modern practice of peripheral regional anesthesia.

Methods We analyzed data from the International Registry of Regional Anesthesia that include prospective data on peripheral regional anesthesia procedures from 21 centers located around the world. Using data from years 2011 to 2017, our primary aim was to characterize the degree of variation in dosing of LA for the top 10 most commonly performed single injection peripheral nerve blocks. Our secondary aim was to identify potential drivers of this variation.

Results Among the 26 457 peripheral blocks performed, mean (±SD) LA dose per block in ropivacaine equivalents was 125.1±51.2 mg and 1.6±0.7 for mg/kg. There was large variation across all block types, with the highest variation (measured by interdecile range) in axillary blocks (143.8 mg) and lowest in interscalene blocks (83.3 mg). In a regression analysis, dose was primarily associated with the hospital (Cohen’s f=0.37) where the block was administered and block type (f=0.38), less so with age (f=0.02), weight (f=0.12), gender (f=0.05) or LA (f=0.17) used. Hospital site had strong impact on variation in LA dose (f=0.88). Variation was not significantly associated with number of blocks performed by hospital site.

Conclusions Large variation in dosing for regional blocks exists within and among hospitals, which is unlikely to be warranted. For many blocks, the variation of dosing is larger than the mean dose. Hospital site had strong impact on variation in LA dose and moderate impact on mean LA dose.