Cranial epidural spread of contrast medium and new methylene blue dye in sternally recumbent anaesthetized dogs.

OBJECTIVE: To examine the spread of solution in the epidural space of sternally recumbent dogs. STUDY
DESIGN: Prospective experimental trial. Animals  Ten healthy adult Beagle dogs weighing 7.6 ± 1.1 kg.
METHODS: Dogs were anaesthetized with total intravenous propofol infusion, and placed in sternal recumbency. A volume of 0.2 mL kg(-1) contrast medium (CM) containing 1% new methylene blue (MB) dye was administered into the lumbosacral epidural space. Left to right lateral radiographs using a horizontal beam were taken every 5 minutes for 45 minutes. The perpendicular height (PH) between floor of the epidural canal of the highest vertebra and that of lumbosacral spinal canal was measured on radiographs. The angle of slope from the injection point toward the highest vertebral floor was measured. Immediately after taking the last radiographic image, dogs were euthanized and a laminectomy was performed from the cervical to lumbar vertebrae for visual evaluation of MB spread. The spread of CM and of MB as counted in number of stained vertebra were compared, and each of these data sets were further compared to PH and angle, using linear regression analyses.
RESULTS: The PH and angle were (mean ± SD) 3.8 ± 0.8 cm and 14.8 ± 2.8° respectively. The most cranial spread of CM was at 12.7 ± 5.7 (range: C6-L3) vertebrae, and at 14.0 ± 5.4 (range: C6-L2) vertebrae for MB staining. There were no significant correlations between PH and spread of CM (R(2)  = 0.08) or MB (R(2)  = 0.13), between angle and spread of CM (R(2)  = 0.05) or MB (R(2)  = 0.02), respectively. CM and MB demonstrated proportional relationship (R(2)  = 0.82, p < 0.001).
CONCLUSIONS: No significant inhibitory effect of upward slope on cranial epidural spread of the solution was observed. Other factors may have greater effect on epidural spread in sternally recumbent dogs.