[Pathophysiology and prevention of contrast-induced acute renal failure]

Although the infusion of iodinated contrast media in diagnostic and interventional procedures may cause acute renal failure (ARF) especially in older or diabetic patients with preexisting nephropathy, these procedures are often unavoidable. Contrast medium-induced ARF is defined as an increase in serum creatinine of 0.5 mg/dL or a 25% or greater relative increase from baseline within 72 hours of iodinated contrast medium infusion. Because it is often very difficult to employ alternative diagnostic procedures, it is mandatory to adopt prophylactic protocols to prevent radiocontrast nephropathy. Renal hemodynamic lesions leading to medullary hypoxia, oxygen free radicals inducing tubular cell alterations, and parenchymal vasoconstriction are the main factors in the pathogenesis of contrast-induced ARF. Among the many proposed protocols to prevent contrast-induced renal toxicity, the most effective procedure is hydration with 1 mL/kg/h of isotonic saline solution in the 12 hours before and after contrast medium infusion. Promising results in terms of cardiac and renal protection have been reported in a recent trial with the use of high-dose N-acetylcysteine acting as an oxygen free radical scavenger: an intravenous bolus of 1200 mg N-acetylcysteine was given before coronary angiography followed by 1200 mg orally twice a day for 48 hours after the procedure. The protective effect seemed to involve not only the kidney: the drug was found to induce a significant reduction of the necrotic area in myocardial infarction.