Craniad migration of differing doses of new methylene blue injected into the epidural space after death of calves and juvenile pigs

Mandi J. Lopez From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr W, Madison, WI 53706.

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Rebecca Johnson From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr W, Madison, WI 53706.

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Dean A. Hendrickson From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr W, Madison, WI 53706.

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Kris T. Kruse-Elliott From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr W, Madison, WI 53706.

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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)

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)

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