The effects of fenoldopam on renal blood flow and tubular function during aortic cross-clamping in anaesthetized dogs

Postoperative renal impairment is a recognized complication of infrarenal a ortic cross-clamping. Fenoldopam, a selective dopamine agonist, may increas e renal blood flow and decrease tubular oxygen consumption. The objective o f this study was to quantify the effects of fenoldopam (0.1 mu g kg(-1) min (-1)) on renal blood flow and renal tubular function in anaesthetized dogs that have undergone aortic cross clamping. Eight labrador dogs were selecte d to receive either saline or fenoldopam (0.1 mu g kg(-1) min(-1)) intraven ously. Arterial pressure, heart rate, renal blood flow, urinary output, fra ctional excretion of sodium, creatinine clearance and lithium clearance wer e measured (a) prior to infusions of saline or fenoldopam (b) 1 h after com mencing the infusion (c) during a 90-min period of infrarenal aortic cross- clamping with concurrent infusion of fenoldopam or saline and (d) for 1 h a fter simultaneous aortic declamping and discontinuation of the infusions. T here was no haemodynamic instability upon commencing the infusion of fenold opam (0.1 mu g kg(-1) min(-1)). Creatinine clearance (2.03+/-0.5-2.45+/-0.3 mL min(-1) kg(-1) (mean+/-SD)), urine output (0.23+/-0.16-0.35+/-0.23 mL m in(-1) (mean+/-SD)), and fractional excretion of sodium (0.7+/-0.52-1.3+/-0 .73%(mean+/-SD)) increased (P < 0.05), following commencement of the fenold opam infusion. Fractional excretion of sodium (1.2+/-0.7% (mean+/-SD)) and urine output (0.36+/-0.21 mL min(-1) (mean+/-SD)) were maintained during th e aortic cross-clamp period (P < 0.05). Renal blood flow increased when the fenoldopam infusion was commenced (145+/-43.3-161+/-39.2 mL min(-1) (mean/-SD)) and remained greater than baseline during the aortic cross-clamping period (152+/-44 mL min(-1) (mean+/-SD)), although these increases did not reach statistical significance. The mast striking abnormalities observed by electron microscopy were marked disruption of the microvillus brush border in proximal tubules, vacuolation and separation of epithelial cells on bas olateral infolds. The changes were similar in the two groups. In conclusion fenoldopam (0.1 mu g kg(-1) min(-1)) may have renoprotective effects which persist during infrarenal aortic cross clamping.