Increase in oxygen supply during experimental septic shock: the effects of dobutamine versus dopexamine

Dobutamine and dopexamine are synthetic adrenergic agents that can efficiently increase cardiac out-put and oxygen supply with little effect on arterial pressure. We compared the effects of these two drugs during experimental septic shock induced by endotoxin infusion in 12 mechanically ventilated dogs. In each animal, dobutamine and dopexamine were administered blindly in a successive and ran domized order at a dose of up to 4 μg/kg/min, while filling pressures were maintained at the baseline level by concurrent fluid administration. Dobutamine and dopexamine administration resulted in a significant and similar increase in cardiac output due to increases in stroke volume and heart rate. Because the arterial pressure increased with dobutamine and not with dopexamine, the left ventricular stroke work increased more with dobutamine and the systemic vascular resistance decreased more with dopexamine. Accordingly, dobutamine has a more pronounced inotropic action and dopexamine has a stronger vasodilating action.Dopexamine also improved arterial oxygenation, possibly by a bronchodilating effect.