title: Assessment of the tissue diffusion of anesthetic agent following administration of a low palmar nerve block in horses.
abstract: OBJECTIVE
  To investigate tissue diffusion of anesthetic agent following administration of low palmar nerve blocks (LPBs) in horses.
  
  
  METHODS
  Randomized clinical trial.
  
  
  METHODS
  12 adult horses.
  
  
  METHODS
  In 9 horses, mepivacaine hydrochloride-iohexol (50:50 dilution) injections were administered bilaterally (2 or 4 mL/site) to affect the medial and lateral palmar and palmar metacarpal nerves (4 sites). Lateral radiographic views of both metacarpal regions were obtained before and at 5, 15, 30, 60, 90, and 120 minutes after block administration; proximal and distal extents of contrast medium (and presumably anesthetic agent) diffusion from palmar and palmar metacarpal injection sites were measured and summed to determine total diffusion. Methylene blue solution was injected in forelimbs of 3 other horses that were subsequently euthanized to determine the potential route of anesthetic agent diffusion to the proximal suspensory ligament region.
  
  
  RESULTS
  Mean extents of proximal and total contrast medium diffusion were 4.0 and 6.6 cm, respectively, for the palmar metacarpal nerves and 4.3 and 7.1 cm, respectively, for the palmar nerves. Subtle proximal diffusion secondary to lymphatic drainage was evident in 17 of the 18 limbs. Contrast medium was detected in the metacarpophalangeal joint or within the digital flexor tendon sheath in 8 and 7 limbs, respectively. In the cadaver limbs, methylene blue solution did not extend to the proximal suspensory ligament region.
  
  
  CONCLUSIONS
  In horses, LPBs resulted in minimal proximal diffusion of anesthetic agent from the injection sites. Limbs should be aseptically prepared prior to LPB administration because inadvertent intrasynovial injection may occur.
authors: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA. Katie.Seabaugh@colostate.edu
authors: Kathryn A
authors: KA
authors: Seabaugh
authors: Kurt T
authors: KT
authors: Selberg
authors: Alejandro
authors: A
authors: Valdés-Martínez
authors: Sangeeta
authors: S
authors: Rao
authors: Gary M
authors: GM
authors: Baxter
mesh_terms: D000772:Anesthesia, Local / Q000662:veterinary*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage / Q000494:pharmacology; D005528:Foot; D005552:Forelimb; D006736:Horses; D007472:Iohexol / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008619:Mepivacaine / Q000008:administration & dosage / Q000493:pharmacokinetics*; D009407:Nerve Block / Q000379:methods / Q000662:veterinary*; D014018:Tissue Distribution
chemical_list: D000779:Anesthetics, Local; D003287:Contrast Media; D007472:Iohexol; D008619:Mepivacaine