title: Percutaneous electrode guidance using the insulated needle for prelocation of peripheral nerves during axillary plexus blocks.
abstract: OBJECTIVE
  Short reports have noted that percutaneous prelocation is helpful in determining the anatomic course of a peripheral nerve, and, thereby, may serve as a guide for block needle insertion. We prospectively studied percutaneous electrode guidance to assist axillary brachial plexus blocks.
  
  
  METHODS
  In 131 consecutive patients, the tip of an insulated needle emitting 5 mA was placed on the skin above and below the axillary artery to obtain a hand motor response characteristic of the median, ulnar, and radial nerves in succession. The current was reduced until all movement had ceased. The needle was then inserted toward the nerve to be blocked, decreasing the intensity from 2 mA to 0.5 mA, so that the same selected motor response was still obtained. The length of the needle inserted was noted, and 1.5% lidocaine was injected. Pain verbal analogic score (VAS) values were noted during both procedures. Complete sensory blockade was evaluated at 30 min.
  
  
  RESULTS
  Rates of successful percutaneous electrode guidance were 94.6% for the median nerve, 89.4% for the radial nerve, 88.5% for the ulnar nerve, and 85.5% for all 3 nerves together. A significant correlation was found between the lowest percutaneous current applied and the depth of the nerve stimulated at 0.5 mA. Pain VAS values were significantly lower during percutaneous stimulation than during needle insertion (P <.05). Sensory block for all 3 nerves was noted in 92% of patients.
  
  
  CONCLUSIONS
  Percutaneous electrode guidance using the insulated needle enabled clinicians to locate the terminal branches of the plexus in the axilla and appreciate their depth. This method could, therefore, minimize patient discomfort and perhaps the risk of nerve trauma.
authors.affiliation: Department of Anesthesia and Critical Care Medicine, Lapeyronie University Hospital, Avenue du Doyen Giraud, 34295 Montpellier Cedex 5, France. x-capdevila@chu-montpellier.fr
authors.forename: Xavier
authors.initials: X
authors.lastname: Capdevila
authors.forename: Sandrine
authors.initials: S
authors.lastname: Lopez
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bernard
authors.forename: Christophe
authors.initials: C
authors.lastname: Dadure
authors.forename: Frédéric
authors.initials: F
authors.lastname: Motais
authors.forename: Philippe
authors.initials: P
authors.lastname: Biboulet
authors.forename: Olivier
authors.initials: O
authors.lastname: Choquet
mesh_terms: D000328:Adult; D001340:Autonomic Nerve Block / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D001366:Axillary Artery / Q000502:physiology; D001917:Brachial Plexus / Q000502:physiology; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009339:Needles / Q000592:standards*; D010525:Peripheral Nerves / Q000502:physiology; D011446:Prospective Studies; D004561:Transcutaneous Electric Nerve Stimulation / Q000295:instrumentation* / Q000379:methods / Q000592:standards