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

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 cm proximal to the palpable palmar aspect of the proximal eminence of the middle phalanx, using 2 or 5 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 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 ml, 94.2% after 5 ml). There was significant proximal diffusion in the first 10 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 = 0.01). The median dorsal diffusion was to the dorsal midline of PP; 5 ml contrast medium resulted in significantly greater dorsal diffusion than 2 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 ml contrast medium. Fetlock region pain may be influenced by a mid-pastern ring block. Ethical animal research: Written consent had been obtained from a representative of the horses' owner prior to starting the study.

SOURCE OF FUNDING

None. Competing interests: None declared.