Effect of supplementation with antioxidants (α‐tocopherol and ascorbic acid) on markers of renal tubular injury in cardiac surgery patients

Summary: Cardiac surgery is accompanied by the risk of ischaemia‐reperfusion injury to both myocardial and peripheral tissues like the kidney due to the generation of oxygen‐derived free radicals. Supplementation with chain‐breaking antioxidants may trap free radicals and help protect tissues from injury. We therefore examined the effect of pre‐treating cardiac surgery patients with α‐tocopherol (vitamin E) and ascorbic acid (vitamin C) or placebo on a hypoxia‐sensitive tissue, the renal proximal tubule. Sixty‐nine subjects undergoing elective coronary artery bypass grafting participated in a prospective, double‐blind, placebo controlled randomized trail, receiving either placebo or both 750 IU/dL‐α‐tocopherol per day for 7‐10 days, and 1 g ascorbic acid 12 h prior to surgery. Plasma α‐tocopherol concentrations fell from elevated to normal levels in the supplemented group and from normal to negligible levels in the placebo group. Renal tubular markers (N‐acetyl‐β‐D‐glucosaminidase, adenosine deaminase binding protein, and γ‐glutamyl transpeptidase) increased significantly relative to creatinine in both groups following surgery ( P > 0.001). However, there were no differences between the two patient groups. Thus, although antioxidant supplementation prior to cardiac surgery prevented the depletion of the primary lipid‐soluble antioxidant in plasma (α‐tocopherol), renal tubular injury was not measurably reduced.