Weight-Based Volume of Injection Influences Cranial to Caudal Spread of Local Anesthetic Solution in Ultrasound-Guided Transversus Abdominis Plane Blocks in Canine Cadavers

Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
Veterinary Surgery (Impact Factor: 1.04). 03/2012; 41(4):455-7. DOI: 10.1111/j.1532-950X.2012.00972.x
Source: PubMed


To determine if the volume of injected local anesthetic solution affects cranial to caudal spread when performing ultrasound-guided transversus abdominis plane (TAP) blocks in dogs.
Prospective experimental study.
Adult Beagle cadavers (n = 20)
Bilateral TAP blocks using ultrasound guidance was performed in 20 Beagle cadavers (mean ± SD weight, 9.3 ± 1.4 kg) using a 1:1 solution of methylene blue/bupivacaine injected at volumes of 0.25, 0.5, 0.75, and 1.0 mL/kg. Cadavers were dissected to determine injectate spread within the transversus abdominis fascial plane.
The transversus abdominis fascial plane was adequately identified by ultrasonography, injected, and dissected in 38 beagle hemi-abdominal walls; injectate was not identified in 2 hemi-abdominal walls. Dermatomal spread (number of ventral nerve roots saturated by injected solution) was volume dependent (P = .026, Kruskal Wallis): 2.9 ± 0.74 nerve roots for 0.25 mL/kg; 3.4 ± 1.1 for 0.5 mL/kg; 4.0 ± 0.67 for 0.75 mL/kg; and 4.2 ± 1.2 for 1 mL/kg.
In Beagle cadavers, the volume of injected local anesthetic solution significantly affects cranial to caudal spread within the TAP during ultrasound-guided TAP blocks. The volume of local anesthetic injected could potentially be used to augment the spread of analgesic coverage for a given surgical procedure in dogs.

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