title: The use of electrical stimulation to guide epidural and intrathecal needle advancement at the L5 -L6 intervertebral space in dogs.
abstract: OBJECTIVE
  To determine the minimal electrical threshold (MET) necessary to elicit appropriate muscle contraction when the tip of an insulated needle is positioned epidurally or intrathecally at the L5-6 intervertebral space (phase-I) and to determine whether the application of a fixed electrical current during its advancement could indicate needle entry into the intrathecal space (phase-II) in dogs.
  
  
  METHODS
  Prospective, blinded study.
  
  
  METHODS
  Thirteen (phase-I) and seventeen (phase-II) dogs, scheduled for a surgical procedure where L5-6 intrathecal administration was indicated.
  
  
  METHODS
  Under general anesthesia, an insulated needle was first inserted into the L5-6 epidural space and secondly into the intrathecal space and the MET necessary to obtain a muscular contraction of the pelvic limb or tail at each site was determined (phase-I). Under similar conditions, in dogs of phase-II an insulated needle was inserted through the L5-6 intervertebral space guided by the use of a fixed electrical current (0.8 mA) until muscular contraction of the pelvic limb or tail was obtained. Intrathecal needle placement was confirmed by either free flow of cerebrospinal fluid (CSF) or myelography.
  
  
  RESULTS
  The current required to elicit a motor response was significantly lower (p < 0.0001) when the tip of the needle was in the intrathecal space (0.48 ± 0.10 mA) than when it was located epidurally (2.56 ± 0.57). The use of a fixed electrical stimulation current of 0.8 mA resulted in correct prediction of intrathecal injection, corroborated by either free flow of CSF (n = 12) or iohexol distribution pattern (n = 5), in 100% of the cases.
  
  
  CONCLUSIONS
  Nerve stimulation may be employed as a tool to distinguish epidural from intrathecal insulated needle position at the L5-6 intervertebral space in dogs. This study demonstrates the feasibility of using an electrical stimulation test to confirm intrathecal needle position in dogs.
authors.affiliation: Anaesthesiology Department, College of Veterinary Medicine, University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Otero
authors.forename: Natali
authors.initials: N
authors.lastname: Verdier
authors.forename: Martin R
authors.initials: MR
authors.lastname: Ceballos
authors.forename: Lisa
authors.initials: L
authors.lastname: Tarragona
authors.forename: Myriam
authors.initials: M
authors.lastname: Flores
authors.forename: Diego A
authors.initials: DA
authors.lastname: Portela
mesh_terms: D000767:Anesthesia, Epidural / Q000662:veterinary*; D000818:Animals; D004285:Dogs / Q000502:physiology / Q000601:surgery*; D004558:Electric Stimulation; D005260:Female; D007268:Injections, Epidural / Q000662:veterinary*; D008159:Lumbar Vertebrae; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009339:Needles; D011446:Prospective Studies
keywords: dog; electrical threshold; epidural; intrathecal; nerve stimulation test