Effects of atrial natriuretic peptide on renal function during cardiopulmonary bypass: a randomized pig model

OBJECTIVES: Acute kidney injury is a well-known complication after cardiac surgery and cardiopulmonary bypass (CPB). In this experimental animal study, we evaluated the effects of atrial natriuretic peptide (ANP) on renal function, perfusion, oxygenation and tubular injury during CPB. METHODS: Twenty pigs were blindly randomized to continuous infusion of either ANP (50 ng/kg/min) or placebo before, during and after CPB. Renal blood flow as well as cortical and medullary perfusion was measured. Blood was repeatedly sampled from the renal vein. Glomerular filtration rate was measured by infusion clearance of 51Cr-EDTA. RESULTS: Glomerular filtration rate was higher (P < 0.001), whereas renal blood flow or renal oxygen delivery was not affected by ANP during CPB. Renal oxygen consumption did not differ between groups during CPB, whereas renal oxygen extraction was higher in the ANP group (P = 0.03). Urine flow and sodium excretion were higher in the ANP group during CPB. Blood flow in the renal medulla, but not in the cortex, dropped during CPB, an effect that was not seen in the animals that received ANP. CONCLUSIONS: ANP improved renal function during CPB. Despite impaired renal oxygenation, ANP did not cause tubular injury, suggesting a renoprotective effect of ANP during CPB. Also, CPB induced a selectively reduced blood flow in the renal medulla, an effect that was counteracted by ANP.