| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 106 === 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.
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