Effects of dopamine on canine intrarenal blood flow distribution during hemorrhage

Renal blood flow distribution was measured in control dogs, dogs given dopamine, hemorrhaged dogs, and dogs hemorrhaged plus infused with dopamine with a modification of 85Kr washout. Kidneys injected with 85Kr through a renal arterial cannula were removed at several specific intervals after injection, rapidly frozen, and sectioned transversely so that pieces of tissue could be isolated and counted for radioactivity. In the normotensive animals, dopamine appeared to produce a mild vasodilatory effect in the subcortical outer medulla (flow increased 50%). Hemorrhage reduced renal regional flow throughout the kidneys. Subcortical outer medullary flow, however, appeared to be proportionately better maintained than were the more peripheral renal regions, so that all regions had similar flows. Hemorrhaged animals receiving dopamine infusion had statistically significantly higher cortical blood flows than did the animals simply hemorrhaged. From this study, it is impossible to determine if the cortical vasodilation during hemorrhage was a direct or indirect effect on the renal vasculature; however, improved perfusion of the renal cortex during hypotension may partially explain the improved renal function reportedly produced by dopamine infusion in patients in shock.