Abstract
Objective
To investigate the effects of sedative doses of intravenous (IV) medetomidine (MED)
or dexmedetomidine (DEX) on selected respiratory variables in dogs.
Study design
Randomized, blinded, crossover study.
Animals
A total of eight healthy adult research Beagles.
Methods
Dogs breathing room air had an electrical impedance tomography belt placed around
the chest and were maintained in right lateral recumbency. Respiratory rate (fR) in movements minute–1 (mpm) and changes in thoracic impedance (ΔZ) in arbitrary units (AU) were recorded
for 120 seconds before (T0) and exactly 10 minutes (T10) after the administration
of IV DEX (10 μg kg–1) or MED (20 μg kg–1), with a minimum washout period of 10 days between treatments. Minute ΔZ () was calculated by multiplying median ΔZ with fR. Data are presented as median (interquartile range). Significance for an overall
effect of drugs (DEX versus MED) or treatment (T0 versus T10) was quantified with a two-way analysis of variance for repeated measures, followed
by, when appropriate, Wilcoxon’s signed rank test for each factor.
Results
Overall, fR decreased from 26 (22–29) mpm at T0 to 13 (10–21) mpm at T10 (p = 0.003) and ΔZ increased from 1.133 (0.856–1.599) AU at T0 to 1.650 (1.273–2.813)
AU at T10 (p = 0.007), but did not change [30.375 (23.411–32.445) AU minute–1 at T0 and 30.581 (22.487–35.091) AU minute–1 at T10]. There was no difference between DEX and MED. Most dogs developed a peculiar
breathing pattern characterized by clusters of breaths followed by short periods of
apnoea.
Conclusions and clinical relevance
Both drugs caused a change in breathing pattern, reduction in fR and increase in ΔZ but did not affect . It is likely that (dex)medetomidine resulted in reduction in fR and increase in tidal volume without impacting minute volume.
Keywords
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References
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Article info
Publication history
Published online: May 14, 2020
Accepted:
May 6,
2020
Received:
November 17,
2019
Identification
Copyright
© 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.
