Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

Abstract

REASONS FOR PERFORMING STUDY: Diffusion of local anaesthetic solution after a mid-pastern ring block has not been investigated. OBJECTIVES: To demonstrate potential distribution of local anaesthetic solution following injection of radiodense contrast medium as performed for a mid-pastern ring block. STUDY DESIGN: Experimental. METHODS: Twelve mature horses were used. One and a half ml radiodense contrast medium was injected over the medial or lateral palmar digital nerve at the level of the proximal aspect of the ungular cartilages. A dorsal ring block was performed on the ipsilateral side, 1.5&#x2009;cm proximal to the palpable palmar aspect of the proximal eminence of the middle phalanx, using 2 or 5&#x2009;ml contrast medium. Both forelimbs were injected on 2 days (48 injections). Four standard radiographic views of the pastern were obtained immediately, 10 and 20&#x2009;min after injections. Images were analysed subjectively and objectively. RESULTS: After dorsal injections the contrast medium was distributed in a diffuse patch over the ipsilateral half of the proximal phalanx (PP), extending proximally over the half of the length of PP in all limbs (greatest proximal extension: 89.0% of the length of PP [from distal] after 2&#x2009;ml, 94.2% after 5&#x2009;ml). There was significant proximal diffusion in the first 10&#x2009;min after injection and significant dorsal diffusion between all time points (P<0.01). There was significant positive association between injected volume and the proximal extension of the dorsal contrast patch (P&#x2009;=&#x2009;0.01). The median dorsal diffusion was to the dorsal midline of PP; 5&#x2009;ml contrast medium resulted in significantly greater dorsal diffusion than 2&#x2009;ml (P<0.01). The dorsal and the palmar contrast patches did not merge. CONCLUSIONS: Diffusion to the proximal aspect of P1 occurred even after injection of only 2&#x2009;ml contrast medium. Fetlock region pain may be influenced by a mid-pastern ring block. Ethical animal research:&#x2002;Written consent had been obtained from a representative of the horses' owner prior to starting the study. SOURCE OF FUNDING: None. Competing interests:&#x2002;None declared.