The effect of dopamine on renal microcirculation in hemorrhagic shock in dogs.

Dopamine, a naturally occuring catecholamine, was infused at the rate of 6 micrograms per kilogram per minute on an hemorrhagic shock model in dogs. Urinary output was continuously recorded, with arterial pressure being maintained at 50 millimeters of mercury. At the termination of the experiment, the dogs were sacrificed, and renal microcirculation was studied by an angiomicrohistologic technique. There was a dramatic increase in urinary output following the infusion of dopamine. Results of the microcirculatory study of the renal vasculature showed markedly increased cortical perfusion and dilation of vessels, particularly at a level of afferent arterioles; however, findings on efferent arterioles were inconsistent. Also, changes in the microvasculature of the medulla were less striking than those of the cortex following the administration of dopamine.