Technical note on cervical epidural catheterization in two adult horses: Injectate distribution and epidural space effects

OBJECTIVE: To determine the caudalmost extent of diffusion of contrast media administered through a cervical epidural catheter (CEC) and to describe pathologic changes associated with maintaining an indwelling CEC for up to 17 days. STUDY DESIGN: Pilot study. ANIMALS: Two mature horses. METHODS: CECs were placed under ultrasound guidance in two horses. Both horses were injected with 5 mL 50% Iohexol contrast solution, followed by radiographs of catheter insertion site to confirm placement. A total volume of 15 mL contrast solution was injected in 5 mL aliquots up to 25 min post-initial injection. Laterolateral radiographs were taken every 5 min post-initial 5 mL injection in the caudal cervical region. Horses were euthanized 16 or 17 days after placement of an indwelling CEC and the area surrounding the catheter was examined using gross necropsy. RESULTS: In one horse, cranial C6 was reached at 25 min following 15 mL of contrast solution. In the other horse, cranial C6 was reached at 1 min following 5 mL of contrast solution. The caudalmost extent of contrast solution was reached after 15 mL and 20-25 min. Grossly, areas of mild inflammation and fibrosis were identified in the epidural space surrounding the catheters at 16-17 days post-catheter placement. CONCLUSION: These results indicate that a 10-15 mL volume of contrast solution can reach the cranial extent of the brachial plexus. Indwelling CECs at days 16 and 17 displayed similar findings on gross necropsy to those previously described for sacrococcygeal and lumbosacral epidural catheters. CLINICAL SIGNIFICANCE: Further studies are warranted to assess the effect of the medical treatment of lesions in the caudal cervical vertebrae of horses through administration via cervical epidural catheters.