CONTRAST NEPHROPATHY

Contrast-induced nephropathy, a well-recognized complication of procedures and imaging studies requiring the use of iodinated contrast medium, is linked to increased morbidity. Although a variety of definitions exist, it is generally defined as an increase in serum creatinine level greater than or equal to 0.5 mg/dL or an increase in creatinine level greater than or equal to 25%. Deterioration in renal function is usually identified within 48 to 72 hours after exposure to contrast medium and may occasionally be irreversible. Patients of advanced age and those with diabetes, heart failure, liver failure, existing renal disease, or multiple myeloma are at increased risk. Agents with potential to impair renal response, such as angiotensin II receptor blockers, angiotensin-converting enzyme inhibitors, diuretic agents, and nonsteroidal anti-inflammatory drugs, should be withdrawn around the time of the procedure if possible. High contrast medium osmolality and large volumes of contrast medium have been implicated and are generally avoided. Multiple prophylactic measures involving the use of antioxidants and hydration protocols continue to be studied. Periprocedural intravenous hydration has proven to be superior to oral hydration. Although volume expansion with a sodium bicarbonate–based infusion was advantageous in prior trials, recent studies have shown it to have no benefit over sodium chloride and, according to some reports, to potentially add harm in subpopulations.Orally administered acetylcysteine acting as a scavenger of oxygen-derived free radicals has been found to add benefit, although this incremental benefit is modest when 24-hour hydration protocols are in place (and in several trials no benefit has been evident).Despite somewhat ambiguous or conflicting data, it is reasonable to use oral N-acetylcysteine in view of its low cost and minimal adverse effect profile. Aminophylline and ascorbic acid have also been studied without conclusive evidence of benefit.

Clinical Pearl

Periprocedural intravenous volume expansion has been demonstrated to reduce the incidence of contrast-induced nephropathy. The addition of N-acetylcysteine to prophylactic protocols may confer a modest additional benefit.