title: Weight-based volume of injection influences cranial to caudal spread of local anesthetic solution in ultrasound-guided transversus abdominis plane blocks in canine cadavers.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Prospective experimental study.
  
  
  METHODS
  Adult Beagle cadavers (n = 20)
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA. sbruggink@uwhealth.org
authors.forename: Sean M
authors.initials: SM
authors.lastname: Bruggink
authors.forename: Kristopher M
authors.initials: KM
authors.lastname: Schroeder
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Baker-Herman
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Schroeder
mesh_terms: D034861:Abdominal Wall / Q000294:innervation*; D000772:Anesthesia, Local / Q000379:methods / Q000662:veterinary; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000818:Animals; D002045:Bupivacaine / Q000008:administration & dosage* / Q000493:pharmacokinetics; D002102:Cadaver; D004396:Coloring Agents; D004285:Dogs / Q000378:metabolism*; D008751:Methylene Blue; D009407:Nerve Block / Q000379:methods / Q000662:veterinary*; D011446:Prospective Studies
chemical_list: D000779:Anesthetics, Local; D004396:Coloring Agents; D008751:Methylene Blue; D002045:Bupivacaine