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Investigation of selected respiratory effects of (dex)medetomidine in healthy Beagles

  • Tekla Pleyers
    Affiliations
    Anaesthesiology section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Berne, Berne, Switzerland
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  • Olivier Levionnois
    Affiliations
    Anaesthesiology section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Berne, Berne, Switzerland
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  • Joëlle Siegenthaler
    Affiliations
    Anaesthesiology section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Berne, Berne, Switzerland
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  • Claudia Spadavecchia
    Affiliations
    Anaesthesiology section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Berne, Berne, Switzerland
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  • Mathieu Raillard
    Correspondence
    Correspondence: Mathieu Raillard, University Veterinary Teaching Hospital, Evelyn Williams building B10, The University of Sydney, 2006, NSW, Australia.
    Affiliations
    Anaesthesiology section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Berne, Berne, Switzerland

    The University of Sydney, Faculty of Science, School of Veterinary Science, The University of Sydney, NSW, Australia
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      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 ( 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 ΔZ ˙ 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 ΔZ ˙ . 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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