As the frequency of contrast media–enhanced radiological procedures grows as the population ages, the incidence of contrast-induced acute kidney injury (CI-AKI) is on the rise. Typically, these older patients also come with comorbidities that predispose them to renal impairment. As Umar Sadat, MD, PhD, and colleagues stated in their recent JACC paper, it is imperative that cardiologists develop a better understanding of the etiology of CI-AKI, with the hopes of reaching diagnosis earlier and formulating more effective preventive and therapeutic regimens.

In the current study, Sadat et al. conducted a meta-analysis to assess whether ascorbic acid (or vitamin C) exerts a nephroprotective effect in patients undergoing coronary angiography. The researchers identified nine randomized controlled trials, totaling 1,536 patients, that compared ascorbic acid to placebo or other pharmacological agents in reducing CI-AKI. Placebos and alternate treatments included N-acetylcysteine and normal saline hydration. Ascorbic acid was given to 740 patients (either through oral administration or intravenous hydration), while 796 patients representing the control group received alternate treatment; all patients had some degree of renal impairment at baseline.

Incidence of CI-AKI in patients receiving ascorbic acid was 9.59%, compared to 16.83% in the control arm. The investigators also conducted a pooled analysis using random effects model, finding that patients receiving ascorbic acid had 33% less risk of CI-AKI compared to the control group (RR = 0.672; p = 0.034).

How does ascorbic acid offer nephroprotection? The exact mechanism is “as unclear as the etiology of CI-AKI,” the authors wrote, but ascorbic acid’s potent antioxidant property likely helps control oxidative stress, which has been implicated as a contributing risk factor in the etiology of CI-AKI.

“This pooled statistical analysis of systematically selected RCTs provides robust evidence that ascorbic acid reduces the risk of CI-AKI, albeit by somewhat small magnitude, in patients undergoing coronary angiography compared to alternate treatment strategies,” Dr. Sadat and colleagues concluded. “To assess its full potential as a nephroprotective agent, further investigation is warranted regarding its optimal dosage and route of administration which affects its bioavailability.”

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Sadat U, Usman A, Gillard JH, Boyle JR. J Am Coll Cardiol. 2013 August 28. [Epub ahead of print]

At TCT 2013, CSWN: Interventions spoke with Paul Zei, MD, about the results from the recent study on SCD prevention with wearable cardioverter-defibrillators. Visit youtube.cswnews.org to watch the interview.

Keywords: Acute Kidney Injury, Comorbidity, Oxidative Stress, Biological Availability, Risk Factors, Contrast Media, Incidence, Kidney Diseases, Coronary Angiography

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