Local Anesthetic Injection Speed and Common Peroneal Nerve Block Duration: A Randomized Controlled Trial in Healthy Volunteers

Background and Objectives The speed of local anesthetic (LA) injections in peripheral regional anesthesia ranges from slow continuous infusions (3–12 mL/h) to rapid manual injections (>7500 mL/h). Optimizing injection speed could augment the spread of LA toward the targeted nerves and influence nerve block characteristics. The objective of this study was to investigate whether injection speed of a single dose of LA affects peripheral nerve block duration. Methods After approval from the Danish Regional Scientific Ethics Committee, we enrolled 60 healthy adult volunteers. We used an ultrasound-guided catheter-based technique to perform a common peroneal nerve block. Participants were randomized to receive 4.0 mL of ropivacaine 0.2% with 1 of 5 injection speeds: 12, 60, 300, 600, or 1800 mL/h. Investigators and participants were blinded to group assignment and intervention. Primary outcome was duration of sensory nerve block defined by insensitivity toward cold. Secondary outcomes were duration of motor nerve block, time to onset of sensory nerve block, and grades of sensory and motor nerve block. Intergroup differences were tested by one-way analysis of variance. Results We found no differences in sensory block duration between the 5 groups. Durations were median [range]: 11 [6–14], 12 [9–14], 10.5 [2–15], 11 [8–17], and 12 [9–18] hours, respectively (P = 0.294). In addition, we found no differences in secondary outcomes. Conclusions Injection speed of LA in the range of 12 to 1800 mL/h did not affect common peroneal nerve block duration. Clinical Trial Registration This study was registered at ClinicalTrials.gov, identifier NCT02801799. Accepted for publication November 13, 2017. Address correspondence to: Mikkel Herold Madsen, MD, Department of Anesthesiology, Nordsjællands Hospital Hillerød, Dyrehavevej 29, Building 52B, 4th Floor, DK-3400 Hillerød, Denmark (e-mail: mhmadsen@gmail.com). This work was funded by Innovation Fund Denmark and by Nordsjællands Hospital Hillerød. This work was presented in part at the American Society of Regional Anesthesia and Pain Medicine 42nd Annual Regional Anesthesiology and Pain Medicine Meeting; San Francisco, CA; April 6 to 8, 2017. The authors declare no conflict of interest. Copyright © 2018 by American Society of Regional Anesthesia and Pain Medicine.

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