Abstract
Objective
To determine the relation between epidural injectate volume (ml/kg of body weight) and its craniad migration in calves and pigs.
Animals
23 neonatal calves and 26 feeder pigs.
Procedure
Animals were randomly assigned to receive different volumes of new methylene blue (NMB, 1.2 mg/ml in 0.9% saline solution). Injections were made into the sacrococcygeal intervertebral space in calves and the lumbosacral intervertebral space in pigs, immediately after euthanasia. Sagittal sections of the spine were made at necropsy, and craniad migration of NMB was determined and rounded to the nearest intervertebral space.
Results
In calves treated with 0.05, 0.1, or 0.15 ml of NMB/kg, mean ± SEM number of stained spinal segments was 5 ± 0.3, 8 ± 0.6, and 8 ± 0.6, respectively. Craniad migration of NMB was significantly greater for 0.15 and 0.1 ml/kg volumes versus 0.05 ml/kg. In pigs treated with 0.05, 0.1, 0.2, or 0.3 ml of NMB/kg, mean number of stained spinal segments was 8 ± 1.1, 8 ± 0.9, 10 ± 1.2, and 18 ± 2.0. Craniad dye migration was significantly greater in the 0.3 ml/kg group versus the 3 lower volume groups. Linear regression performed on both sets of data after logarithmic transformation of spaces migrated to correct for non-normality was significant (P < 0.05), and R 2 values of 0.49 and 0.55 were obtained for calves and pigs, respectively.
Conclusions
There is a significant correlation between volume (ml/kg) of NMB injected in the epidural space and its craniad migration in calves and pigs.
Clinical Relevance
Results provide a basis for determination of volume of injectate to be given to reach a minimal desired level and should be a useful baseline for future investigations of epidural drug administration. (Am J Vet Res 1997;58:786–790)
