Comparison of effects of dopamine hydrochloride and dopexamine hydrochloride on abdominal and femoral hemodynamics in anesthetized dogs.

The effects of dopamine and dopexamine administered in graded intravenous bolus injections (0.1-51.2 micrograms.kg-1) were compared in the renal and femoral, and in a number of splanchnic vessels at the organ level simultaneously in anesthetized dogs. Hemodynamic data are presented for each artery as conductance, which was obtained by dividing mean flow by mean arterial pressure. The data were analyzed in two different ways: 1) by responses at intervals of 3 sec to 12.8 micrograms dopamine or dopexamine during 1 min, and 2) by dose-response curves. Additionally, urine volume was measured during dopamine and dopexamine administration. During a period of 1 min after an injection of dopamine, early and late effects could be distinguished, while heart rate was unaltered. In the superior mesenteric, inferior mesenteric, splenic, common hepatic, renal, and femoral arteries, an early (at 18-21 sec) reduction in conductance was seen. The early reduction was often followed by an increase above the preinjection level. After dopexamine, the early reduction in conductance was not seen, except in the left gastric artery. In contrast to the effect of dopamine, dopexamine induced a more pronounced increase during the late phase. Contrary to dopamine, dopexamine increased the conductance in the common hepatic artery bed. It remains questionable whether dopaminergic receptors are present in this vascular bed. Dopamine raised blood pressure and urine production dose-dependently. Dopexamine decreased aortic pressure. Low dosages of dopexamine increased urine production, without raising renal blood flow. An advantage of dopexamine over dopamine could be that dopexamine does not stimulate alpha-adrenergic receptors.