Vitamin C protects kidneys against angiography contrast

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Ascorbic acid findings represent advancement

The findings of this meta-analysis represent an advancement in the field, and frame ascorbic acid as a potential therapy to be evaluated in large-scale clinical trials, according to Dr. Peter A. McCullough and Dr. Krittapoom Akrawinthawong.

This is important given the lack of "bona fide preventive approaches" to protect against CK-AKI until less-toxic iodinated contrast becomes available, they wrote in an editorial (J. Am. Coll. Cardiol. 2013 Aug. 28).

However, several questions about the potential benefits of ascorbic acid in this setting remain unanswered, they noted.

The key question remains: "If we prevent or lessen CI-AKI as determined by serum creatinine, will we reduce the rates of clinical outcomes including end-stage renal disease, mortality, and more secondary events including the development of heart failure, recurrent acute coronary syndromes, or stroke?"

This question can be answered only by large-scale trials with effective therapies and adequate follow-up, they said.

Dr. McCullough is with Providence Hospitals and Medical Centers, Southfield and Novi, Mich. Dr. Akrawinthawong is with St. John Hospital and Medical Center, Detroit. They said they had no relevant financial disclosures.



Ascorbic acid may protect against contrast-induced-acute kidney injury in patients undergoing coronary angiography, a meta-analysis of nine randomized controlled trials has shown.

The overall incidence of contrast-induced acute kidney injury (CI-AKI) among 740 patients who received ascorbic acid and who were included in the final analysis was 9.6%, compared with 16.8% in 796 patients who received placebo or an alternative pharmacologic treatment, Dr. Umar Sadat of Cambridge (England) University Hospitals NHS Foundation Trust, and colleagues reported.

"In the pooled analysis using random effects model, patients receiving ascorbic acid had 33% less risk of CI-AKI compared to the control group (risk ratio, 0.672)," a statistically significant difference, the investigators wrote.

The findings were published online Aug. 28 in the Journal of the American College of Cardiology.

The investigators systematically reviewed Medline, Embase, and Cochrane central databases for studies published from inception to May 2013 on the incidence of CI-AKI in patients undergoing coronary angiography. Studies that were included in the meta-analysis had at least one arm that involved treatment with ascorbic acid alone or in combination with saline hydration. Ultimately, nine studies involving a total of 1,536 patients with baseline renal impairment were included (J. Am. Coll. Cardiol. 2013 Aug. 28).

The findings, which provide "robust evidence that ascorbic acid reduces the risk of CI-AKI, albeit by a small magnitude," suggest that ascorbic acid has nephroprotective qualities and could form a part of effective prophylactic pharmacologic regimens to protect patients undergoing coronary angiography against CI-AKI.

It makes sense that ascorbic acid – a form of vitamin C – could provide nephroprotection, because strong evidence suggests it acts as a potent antioxidant by scavenging physiologically relevant reactive oxygen species (ROS), they explained, noting that ROS-induced oxidative stress and renal vasoconstriction have been implicated in the etiology of CI-AKI.

The findings are important, because the incidence of CI-AKI is rising in tandem with the increasing number of contrast media–enhanced radiologic procedures and with a rise in the octogenarian population with comorbidities such as hypertension, diabetes, and renovascular disease that predispose patients to renal impairment, the investigators said.

However, further investigation regarding the optimal dosage and route of administration of ascorbic acid in order to assess its full potential as a nephroprotective agent is warranted, they concluded.

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