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 (f_R) 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 ($\dot{\text{ΔZ}}$) was calculated by multiplying median ΔZ with f_R. 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, f_R 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 $\dot{\text{ΔZ}}$ 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 f_R and increase in ΔZ but did not affect $\dot{\text{ΔZ}}$. It is likely that (dex)medetomidine resulted in reduction in f_R and increase in tidal volume without impacting minute volume.

中文翻译：

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调查（dex）美托咪定对健康小猎犬的某些呼吸作用。

目的

研究镇静剂量的静脉注射（IV）美托咪定（MED）或右美托咪定（DEX）对犬所选呼吸系统变量的影响。

学习规划

随机，盲法，交叉研究。

动物

共有八只健康的成人研究小猎犬。

方法

狗在呼吸室内的空气中，胸部周围有一条电阻抗断层扫描带，并保持右卧位。静脉注射DEX前120秒（T0）和运动后10分钟（T10），以分钟^–1（mpm）的呼吸速率（f _R）和任意单位（AU）记录的胸阻抗变化（ΔZ）。 （10μgkg ^–1）或MED（20μgkg ^–1），两次治疗之间的最小冲洗时间为10天。分钟ΔZ（$\dot{\text{ΔZ}}$）通过将中位数ΔZ乘以f _R来计算。数据以中位数（四分位间距）表示。对药物的总体效果（DEX对MED）或治疗（T0对T10）的总体意义通过对重复测量进行方差的双向分析进行量化，然后在适当时采用每种因子的Wilcoxon符号秩检验。

结果

总体而言，f _R从T0时的26（22-29）mpm降低到T10时的13（10-21）mpm（p  = 0.003），ΔZ从T0时的1.133（0.856-1.59999）AU增加到1.650（1.273-2.813） T10时为AU（p  = 0.007），但$\dot{\text{ΔZ}}$没有改变[30.375（23.411-32.445）AU分钟^-1在T0和30.581（22.487-35.091）AU分钟^-1在T10]。DEX和MED之间没有区别。大多数狗表现出独特的呼吸模式，其特征是呼吸簇，随后出现短暂的呼吸暂停。

结论与临床意义

两种药物均导致呼吸模式改变，f _R降低和ΔZ升高，但并未影响$\dot{\text{ΔZ}}$。（dex）美托咪定可能会导致f _R降低和潮气量增加而不会影响每分钟的体积。