A cadaveric study to determine the minimum volume of methylene blue to completely color the nerves of brachial plexus in cats. An update in forelimb and shoulder surgeries

Abstract

PURPOSE:To determine the minimum volume of methylene blue (MB) to completely color the brachial plexus (BP) nerves, simulating an effective anesthetic block in cats. METHODS:Fifteen 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. RESULTS:Volumes 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. CONCLUSIONS:The 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.

Origin and distribution of the brachial plexus of the Van cats

“…In this study, in line with the findings reported for cats (McClure et al, ), it was determined that the radial nerve was formed by the ventral branches of the 7th and 8th cervical nerves. In line with the findings asserted in the literature (Aubert et al, ; Mencalha et al, ), this study observed that after giving off a muscle branch for the medial head of the triceps brachii muscle, the radial nerve was divided into the superficial branch and the deep branch.…”

“…It was reported that the radial nerve was formed by the ventral branches of the 7th and 8th cervical (McClure et al, ) or the 7th and 8th cervical and the 1st thoracic nerves (Anson et al, ; König & Liebich, ; Mencalha et al, ). In this study, in line with the findings reported for cats (McClure et al, ), it was determined that the radial nerve was formed by the ventral branches of the 7th and 8th cervical nerves.…”

“…The median nerve originates from the ventral branches of the last two cervical and the first thoracic nerves as two separate roots. These separate branches join at about proximal with 1/3 of the humerus and form the main nerve (Mencalha et al, ). In cats, after passing through the supracondylar foramen, the median nerve is divided into the medial branch and the lateral branch in the distal 1/3 of the antebrachium (Ghoshal, ; Tecirlioğlu, ).…”

“…According to Ghoshal (1972) and Aslan (1994), the axillary nerve originates from the ventral branch of the 6th cervical nerve. It branches off from the cranial brachial cutaneous nerve to the dorsocranial skin of the cubital joint (Anson et al, 2013;Aubert et al, 2004;Mencalha, Fernandes, Sousa, & Abidu-Figueiredo, 2014).…”

Ultrasound and gross anatomy of the brachial plexus and major nerves of the forelimb. An anesthetic approach using the domestic rabbit (Oyctolagus cuniculus) as an experimental model1

“…The study of anatomical landmarks, morphology and morphometric are important to optimize the results of surgical and anesthetic interventions 2,3 . Until the last century, locoregional blocks were exclusively performed through anatomical references, and consequently had high rates of failure and injury.…”