Background: Decreased renal blood flow (RBF) and vasoconstriction are considered major mechanisms of contrast-induced acute kidney injury (CIAKI). To understand the severity and duration of such putative effects, we measured systemic and renal hemodynamics after intra-arterial radiocontrast administration. The subjects were six Merino ewes. The setting was a university-affiliated research institute. This is a randomized cross-over experimental study.
Methods: Transit-time flow probes were implanted on the pulmonary and left renal arteries 2 weeks before experimentation. We simulated percutaneous coronary intervention by administering five intra-arterial boluses of 0.5 mL/kg saline (control) or radiocontrast (iodixanol) to a total of 2.5 mL/kg over 1 h. Cardiac output (CO), heart rate, mean arterial pressure (MAP), RBF, renal vascular conductance (RVC), urine output (UO), creatinine clearance (CrCl), and fractional excretion of sodium (FENa) were measured.
Results: In the first 8 h after intra-arterial administration of radiocontrast, CO, total peripheral conductance (TPC), and heart rate (HR) increased compared with those after normal saline administration. Thereafter, CO and TPC were similar between the two groups, but HR remained higher with radiocontrast (p < 0.001). After a short (30 min) period of renal vasoconstriction with preserved RBF secondary to an associated increase in MAP, RBF and RVC showed an earlier and greater increase (vasodilatation) with radiocontrast (p < 0.001) and remained higher during the first 2 days. Radiocontrast initially increased urine output (p < 0.001) and FENa (p = 0.003). However, the overall daily urine output decreased in the radiocontrast-treated animals at 2 days (p < 0.001) and 3 days (p = 0.006). Creatinine clearance was not affected.
Conclusions: In healthy animals, intra-arterial radiocontrast increased RBF, induced renal vasodilatation, and caused a delayed period of oliguria. Our findings suggest that sustained reduction in RBF and renal vasoconstriction may not occur in normal large mammals after intra-arterial radiocontrast administration.