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Spread of Injectate Associated With Radial or Median Nerve-Type Motor Response During Infraclavicular Brachial-Plexus Block: An Ultrasound Evaluation
  1. Sébastien Bloc, M.D.,
  2. Thierry Garnier, M.D.,
  3. Bernard Komly, M.D.,
  4. Hugues Asfazadourian, M.D.,
  5. Pascal Leclerc, M.D.,
  6. Luc Mercadal, M.D.,
  7. Bertrand Morel, M.D. and
  8. Gilles Dhonneur, M.D., Ph.D.
  1. Department of Anesthesiology, Private Hospital, Claude Galien, Quincy-sous-Snart, Paris, France
  2. Anesthesia and Intensive Care Department, Public University Hospital of Paris, Paris School of Medicine, Bobigny, France.
  1. Reprint requests: Gilles Dhonneur, M.D., Ph.D., Service d'Anesthésie et Reanimation, CHU (APHP) Jean Verdier, 93153, Av du 14 Juillet, 93143 Bondy CEDEX, Paris, France. E-mail: gilles.dhonneur{at}


Background and Objectives: 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.

Conclusion: 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.

  • Infraclavicular plexus block
  • Nerve stimulation
  • Ultrasound guidance
  • Spread of injectate

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  • This work was funded by departmental sources.

    This work has been presented as an abstract at the SFAR Congress, Paris, September 2006.