• Rodrigo Mencalha, Neide Fernandes, Carlos Augusto dos Santos Sousa, and Marcelo Abidu-Figueiredo.
• Department of Veterinary Surgery and Anestesiology, School of Veterinary Medicine, Valença Higher Education Center, Valença, RJ, Brazil.
• Acta Cir Bras. 2014 Jun 1;29(6):382-8.

PurposeTo determine the minimum volume of methylene blue (MB) to completely color the brachial plexus (BP) nerves, simulating an effective anesthetic block in cats.MethodsFifteen adult male cat cadavers were injected through subscapular approach with volumes of 2, 3, 4, 5 and 6 ml in both forelimbs, for a total of 30 brachial plexus blocks (BPB). After infusions, the specimens were carefully dissected preserving each nervous branch. The measurement of the effective area was indicated by the impregnation of MB. Nerves were divided into four segments from the origin at the spinal level until the insertion into the thoracic limb muscles. The blocks were considered effective only when all the nerves were strongly or totally colored.ResultsVolumes of 2, 3 and 4 ml were considered insufficient suggesting a failed block, however, volumes of 5 and 6 ml were associated with a successful block.ConclusionsThe injection of methylene blue, in a volume of 6 ml, completely colored the brachial plexus. At volumes of 5 and 6 ml the brachial plexus blocks were considered a successful regional block, however, volumes of 2, 3 and 4 ml were considered a failed regional block.

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