Assessment of Renal Flow and Flow Reserve in Humans

ObjectivesThe purpose of this work was to establish the normal range of maximal renal hyperemic response in humans and to identify the ideal renal vasodilatory stimuli.BackgroundStenotic renovascular atherosclerosis is increasingly treated by percutaneous transluminal renal intervention but with an unpredictable outcome. This may be due to hemodynamically non-significant stenosis or the presence of irreversible damage to the glomerular circulation. We propose that the renovascular hyperemic response may help identify appropriate patients.MethodsIn 28 normotensive patients, quantitative angiographic measurements of the renal artery were obtained, and renal artery pressure and flow velocity were continuously recorded after various hyperemic agents.ResultsIn a first group of 11 patients, a significant increase in renal artery average peak velocity (APV) was observed after intrarenal (IR) bolus injection of 600 μg isosorbide dinitrate (41 ± 19%), 30 mg papaverine (50 ± 34%), 50 μg dopamine (94 ± 54%), 0.8 μg·kg−1fenoldopam (80 ± 25%), and during IR infusion of 1 μg·kg−1·min−1fenoldopam (86 ± 28%). A second group of 17 patients received intravenous infusion of dopamine (3, 5, 10, 20, 30, and 40 μg·kg−1·min−1). The 3 and 5 μg·kg−1·min−1of dopamine modestly reduced renal resistance index (RI) (−13 ± 15% and −25 ± 20%, respectively). At higher dosages, no further decline in RI was observed. No significant change in vessel diameter was observed before and after the administration of the pharmacological stimuli suggesting that changes in APV corresponded with changes in absolute renal blood flow.ConclusionsThe normal renal flow reserve averages approximately 2 in humans with normal renal function. An IR bolus injection of 50 μg·kg−1of dopamine is the most convenient means to elicit maximal renal hyperemia.