臺灣博碩士論文加值系統

Dexmedetomidine具有良好的鎮靜、抗焦慮、止痛和減少吸入性麻醉劑用量的效果，因此常被用於麻醉前給藥和術中止痛。然而，Dexmedetomidine會造成顯著的血液動力學變化，包括心律不整、持續性的心搏徐緩和全身血管阻力增加。目前很少研究提及關於低劑量的Dexmedetomidine恆定速率輸注對於犬隻心臟功能的改變。本研究總共納入八隻健康犬隻，麻醉的流程先以propofol導入麻醉、isoflurane維持麻醉，之後由頭靜脈給予1 μg kg-1 Dexmedetomidine做為初始劑量，接著給予1 μg kg-1 hr-1 Dexmedetomidine。分別在給予恆定速率輸注Dexmedetomidine前(紀錄為基礎值)和給予後的第20和60分鐘 (紀錄為T20和T60)，紀錄心跳、呼吸速率、血壓和進行心臟超音波的檢查。與基礎值相比，T20和T60時心跳顯著下降而血壓顯著上升，左心室收縮期的內徑和左心房直徑顯著增加。在T60時，E波和S波的速率顯著下降，最大肺動脈流速在T20和T60皆顯著下降。儘管如此，整體心臟收縮及舒張功能指標，包括心輸出量、縮短分率、射血分率、E / A和E / E'在給予Dexmedetomidine後與給予前相比皆沒有顯著差異，我們也藉由彩色都卜勒成像發現給予Dexmedetomidine後，出現瓣膜逆流。整題而言，儘管在健康犬隻給予Dexmedetomidine恆定速率輸注會造成一些數值的改變，然而這些改變並不影響心輸出量和整體心臟收縮及舒張功能。1 μg kg-1 hr-1 Dexmedetomidine是可以安全用於isoflurane麻醉下的健康犬隻，甚至也可能適用於擁有無臨床症狀心臟病的犬隻。

Dexmedetomidine is used as a premedication and intraoperative analgesia, because it can provide good sedative, anxiolytic, analgesic effects and a reduced inhaled anesthetics requirement. Dexmedetomidine causes significant changes of haemodynamics, including arrhythmias, sustained bradycardia, increased systemic vascular resistance. There are little liiteratures mention about the cardiac function change of low dosage continuous rate infusion (CRI) of dexmedetomidine in dogs. In present study, anaesthetic protocol of eight healthy dogs were induction with propofol and maintenance with isoflurane. A loading dose of 1 μg kg-1 dexmedetomidine was given, immediately followed by a CRI of 1 μg kg-1 hr-1. Heart rate, respiratory rate, blood pressure and the parameters of echocardiography were recorded before administration of dexmedetomidine at baseline, at 20 and 60 minutes (recorded as T20 and T60) after dexmedetomidine CRI. Heart rate decreased and blood pressure increased at T20 and T60 compared with baseline. The left ventricular internal diameter in systole and the left atrium diameter increased after dexmedetomidine CRI. E velocity(m/s), S’ velocity(m/s) decreased at T60, and maximal pulmonary velocity(m/s) decreased at T20 and T60. There was no significant difference in general systolic and diastolic function indicator, including cardiac output, fractional shortening, ejection fraction, E/A and E/E', at T20 and T60 compared with baseline. The appearance of valvular regurgitation was identified by color Doppler imaging. In conclusion, a little changes of parameters were found after administered dexmedetomidine CRI in healthy dogs. However, these changes does not impair cardiac output, general systolic and diastolic cardiac function. It is appropriate to use 1 μg kg-1 hr-1 dexmedetomidine in healthy dogs anesthetized by isoflurane, and also may be used in dogs with asymptomatic heart disease.

致謝 i
摘要 ii
Abstract iii
Contents v
Figure contents vii
Table contents viii
Abbreviations ix
Chapter 1 Introduction 1
Chapter 2 Literature Reviews 3
2.1 α2-Adrenergic receptor 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 Pharmacokinetics 7
2.1.2.2 Pharmacodynamics 8
2.1.2.3 Cardiopulmonary 9
2.1.2.4 Other effects 10
2.2 Atipamezole 11
2.3 Echocardiographic evaluation of the effects of α2 agonists 12
Chapter 3 Material and Methods 13
3.1 Animals 13
3.2 Anesthesia Protocol 13
3.3 Echocardiography 15
3.4 M-mode echocardiographic measurements 15
3.5 Two-dimensional echocardiographic measurements 16
3.6 Doppler echocardiographic measurements 16
3.7 Statistical analysis 17
Chapter 4 Results 24
4.1 Clinical exam variables and blood pressure 24
4.2 M-mode echocardiographic measurements 24
4.3 2D echocardiographic measurements 24
4.4 Doppler echocardiographic measurements 25
4.5 Cardiac output values 25
4.6 Presence of valvular regurgitation and smoke 26
Chapter 5 Discussion 33
5.1 Cardiovascular and respiratory effect 33
5.2 Diastolic function of left ventricle 35
5.3 Systolic function of left ventricle 37
5.4 Maximal aortic and pulmonary velocities 38
5.5 Valvular regurgitation and smoke 40
5.6 Limitations 41
5.7 Conclusion 42
References 43

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