title: Effects of approach and injection volume on diffusion of mepivacaine hydrochloride during local analgesia of the deep branch of the lateral plantar nerve in horses.
abstract: OBJECTIVE
  To compare the effects of 2 approaches and 2 injection volumes on diffusion of mepivacaine hydrochloride for local analgesia of the deep branch of the lateral plantar nerve (DBLPN) in horses.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  16 adult horses.
  
  
  METHODS
  Either 2 mL (low volume) or 8 mL (high volume) of mepivacaine hydrochloride-iohexol (50:50 mixture) was injected by means of 1 of 2 techniques to produce analgesia of the DBLPN. For technique 1, the needle was inserted 15 mm distal to the head of the fourth metatarsal bone and directed perpendicular to the limb. For technique 2, the needle was inserted 20 mm distal to the head of the fourth metatarsal bone and was directed in a proximodorsal direction. Lateromedial radiographs were obtained before and 5, 15, 30, and 60 minutes after injection. Radiographs were evaluated to determine the proximal and distal extent of diffusion of the contrast solution and presumably anesthetic agent and whether contrast agent appeared to be present in the tarsal sheath or tarsometatarsal joint.
  
  
  RESULTS
  A high degree of variability in contrast solution diffusion was noted among injections. High-volume injections diffused significantly further proximally and distally than did low-volume injections. Contrast agent was documented within the tarsal sheath in 5 of 32 (16%) injections and within the tarsometatarsal joint in 2 of 32 (6%) injections. No significant difference was found for risk of inadvertent tarsal sheath or tarsometatarsal joint injection between the 2 techniques or the 2 volumes of anesthetic used. Mepivacaine diffused significantly further distally with technique 1 than with technique 2 but diffused significantly further proximally with technique 2 than with technique 1. For both techniques, diffusion in the distal but not the proximal direction significantly increased over time.
  
  
  CONCLUSIONS
  Results indicated that the proximal and distal diffusion of the mepivacaine-iohexol solution was quite variable following either DBLPN nerve block technique.
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Claunch
authors.forename: Randy B
authors.initials: RB
authors.lastname: Eggleston
authors.forename: Gary M
authors.initials: GM
authors.lastname: Baxter
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage / Q000494:pharmacology; D006614:Hindlimb; D006736:Horses; D007267:Injections / Q000379:methods / Q000662:veterinary; D007472:Iohexol / Q000008:administration & dosage / Q000494:pharmacology; D008619:Mepivacaine / Q000008:administration & dosage* / Q000493:pharmacokinetics; D009407:Nerve Block / Q000379:methods / Q000662:veterinary*
chemical_list: D000779:Anesthetics, Local; D003287:Contrast Media; D007472:Iohexol; D008619:Mepivacaine