Strategies to prevent contrast nephropathy

Contrast nephropathy (CN) is a common cause of iatrogenic acute renal failure. Its incidence rises with the growing use of intra-arterial contrast in older patients for diagnostic and interventional procedures. Aim of the present review is to discuss the mechanisms and risk factors of CN, to summarize the controlled studies evaluating measures for prevention, and to conclude with evidence-based strategies for prevention. Pathophysiological mechanisms of CN are intrarenal vasoconstriction, leading to medullary ischemia, direct cytotoxicity, oxidative tissue damage and apoptosis. Nephrotoxicity is related to osmolality, dose and route of the contrast agent and only occurs in synergy with patient factors, such as previous renal impairment, cardiovascular disease, oxidant stress and the use of certain drugs. CN has impact on morbidity and mortality. In patients at risk, the following measures are recommended: discontinuation of potentially nephrotoxic drugs, treatment of intravascular volume depletion, hydration with sodium-bicarbonate (which seems superior to sodium-chloride), limitation of contrast volume and the use of low-osmolal contrast. Furthermore, if starting the day before is feasible, administer oral N-acetylcysteine, or, with urgent interventions, theophylline 200 mg i.v. (once before the intervention) or high dose ascorbic acid. In patients with combined severe cardiac and renal insufficiency, periprocedural hemofiltration may be considered; this is the only intervention with proven clinical improvement. Large randomised controlled trials are necessary to show whether pharmacological interventions can improve clinical outcomes.