title: Spread of injectate associated with radial or median nerve-type motor response during infraclavicular brachial-plexus block: an ultrasound evaluation.
abstract: OBJECTIVE
  We have compared ultrasound characteristics of spread during infraclavicular brachial-plexus blocks by use of electrically evoked radial-nerve- or median-nerve-type distal motor responses to guide the injection of 30 mL of 1.5% mepivacaine.
  
  
  METHODS
  Consecutive patients who required surgery distal to the upper arm were prospectively included in this study. With radial- or median-evoked distal motor response at a stimulating current intensity of less than 0.5 mA, patients were distributed into 2 equal groups. An independent investigator blinded to the evoked response described ultrasound characteristics of the spread of local anesthetic and assessed block quality 30 minutes after placement. A quality diffusion score proportional to the extent and intensity of spread around the axillary artery was used, and dynamic movements during injection were noted.
  
  
  RESULTS
  Thirty-two patients were included. With radial-nerve-type motor response, the success rate of infraclavicular plexus block was 100%, but 3 supplemental axillary blocks were requested with median-nerve-type motor response. Quality diffusion scores were significantly higher with radial-nerve-type as compared with median-nerve-type motor response (P = .03). Injection after radial-nerve-type motor response resulted in a typical and reproducible ultrasound feature of posterior local-anesthetic spread associated with medial and upper movement of the axillary artery. With median-nerve-type motor response, failed blocks were associated with a specific posterior displacement of the axillary artery that resulted from superficial spread.
  
  
  CONCLUSIONS
  We have demonstrated that as compared with median-nerve-type motor response, injection performed after a radial-nerve-type motor response promoted reproducible and remarkable ultrasound spread characteristics associated with complete sensory block of the 3 cords at 30 minutes.
authors.affiliation: Department of Anesthesiology, Private Hospital, Claude Galien, Quincy-sous-Snart, Paris, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Bloc
authors.forename: Thierry
authors.initials: T
authors.lastname: Garnier
authors.forename: Bernard
authors.initials: B
authors.lastname: Komly
authors.forename: Hugues
authors.initials: H
authors.lastname: Asfazadourian
authors.forename: Pascal
authors.initials: P
authors.lastname: Leclerc
authors.forename: Luc
authors.initials: L
authors.lastname: Mercadal
authors.forename: Bertrand
authors.initials: B
authors.lastname: Morel
authors.forename: Gilles
authors.initials: G
authors.lastname: Dhonneur
mesh_terms: D000328:Adult; D000368:Aged; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000493:pharmacokinetics; D001365:Axilla; D001917:Brachial Plexus / Q000187:drug effects; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D007267:Injections; D008297:Male; D008475:Median Nerve / Q000187:drug effects / Q000502:physiology; D008619:Mepivacaine / Q000008:administration & dosage / Q000493:pharmacokinetics; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects* / Q000295:instrumentation; D011446:Prospective Studies; D011826:Radial Nerve / Q000187:drug effects / Q000502:physiology; D018084:Ultrasonography, Interventional
chemical_list: D000779:Anesthetics, Local; D008619:Mepivacaine