1994 Volume 25 Issue 2 Pages 49-55
Six horses were anesthetized with isoflurane and positioned in right lateral recumbency. End expiratory isoflurane concentration was maintained at 1.7±0.1% and arterial carbon dioxide was maintained at 40±5 mmHg by controlled mechanical ventilation. Three doses of dobutamine (0.5, 1.0 and 2.0 μg/kg/min) were infused and hemodynamic responses were measured. Mean arterial pressure significantly increased dose-dependently by dobutamine infusions. Systemic vascular resistance also increased significantly but the response was not dose-dependent. Stroke volume slightly increased by dobutamine infusions at a dose of 0.5 μg/kg/min and clearly increased at doses of 1.0 and 2.0 μg/kg/min. Heart rate slightly decreased at doses of 0.5 and 1.0 μg/kg/min of dobutamine and slightly increased at a dose of 2.0 μg/kg/min. Accordingly, cardiac output was not significantly changed at a dose of 0.5μg/kg/min of dobutamine, but a slight increase in cardiac output at a dose of 1.0 μg/kg/min and a significant increase at a dose of 2.0 μg/kg/min were observed. It was considerd that increased mean arterial pressure by dobutamine infusion solely depended on the increase in systemic vascular resistance at a dose of 0.5 μg/kg/min and on the increases in both systemic vascular resistance and cardiac output at 1.0 or 2.0 μg/kg/min.
