臺灣博碩士論文加值系統

Dexmedetomidine is one of α2-adrenergic receptor agonists widely used in human and animals as a sedative-analgesic drug, and it is a highly specific and selective α2-adrenoceptor agonist. α2A-subtype, a kind of α2-adrenergic receptors, produces the most classical effects of α2-adrenergic receptor agonists. In dogs, the hemodynamic effects of α2-agonists includes the biphasic change of blood pressure accompanying increased systemic vascular resistance and central venous pressure, and decreased heart rate and cardiac index. In present study, six healthy dogs of clinical cases were dosed intravenously with dexmedetomidne 250 μg/m2; vertebral heart score (VHS) and echocardiographic parameters were evaluated. These data collected before and after administration of the medicine were compared. After dosing dexmedetomidine, systolic (SBP), diastolic (DBP), and mean (MBP) blood pressure, VHS, E point to septal separation (EPSS), end-diastolic/systolic volume (EDV/ESV), and left ventricle internal diameter in diastole/systole (LVIDd/LVIDs) appeared significant increases; heart rate (HR), E velocity, fractional shortening (FS), ejection fraction (EF), stroke volume/index (SV/SI), cardiac output/index (CO/CI), interventricular septal thickness in diastole/systole (IVSTd/IVSTs), and left ventricle posterior wall thickness in diastole (LVPWTd) showed significant decreases. Mitral, tricuspid, and pulmonary regurgitation occurred in dogs after medication. According to the results, both systolic and diastolic function of left heart decreased. The increased preload and decreased systolic function might contribute to the enlargement of heart, especially left ventricle, and further aggravate mitral regurgitation. Therefore, this drug may be not very proper to sedate dogs that undergo the examination of thoracic radiography and ultrasonography.

Contents
中文摘要 i
Abstract ii
Contents iii
Table contents v
Figure contents vi
List of abbreviations vii
Chapter 1 Introduction 1
Chapter 2 Literature Reviews 3
2.1. α2-Adrenoceptor agonists 3
2.1.1. Classification of α2 receptor subtypes 3
2.1.1.1. α2A-adrenergic receptor 3
2.1.1.2. α2B-adrenergic receptor 5
2.1.1.3. α2C-adrenergic receptor 6
2.1.2. Dexmedetomidine 7
2.1.2.1. Pharmacology and pharmacokinetics 7
2.1.2.2. Hemodynamic and other effects 8
2.2. Atipamezole 11
2.3. Echocardiographic evaluation in α2 agonists-sedated animals 12
Chapter 3 Materials and Methods 14
3.1. Animals 14
3.2. Instruments 14
3.2.1. Dexmedetomidine 14
3.2.2. Atipamezole 14
3.2.3. Radiographic equipment 14
3.2.4. Echocardiography machine 14
3.2.5. Medical monitor 14
3.3. Experimental protocol 15
3.4. Radiographic assessment 15
3.5. Echocardiographic assessment 15
3.6. Statistical analysis 17
Chapter 4 Results 18
4.1. Heart rate (HR) 18
4.2. Blood pressure 18
4.3. Vertebral heart score (VHS) 18
4.4. Echocardiographic parameters 19
Chapter 5 Discussion 29
5.1. Heart rate (HR) and blood pressure 29
5.2. Echocardiographic parameters 30
5.2.1. With B-mode and M-mode echocardiography 30
5.2.2. With Doppler echocardiography 35
5.3. Conclusion 37
References 38
Appendix 52

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