Intravenous iron: the iatrogenic kick to lose control over oxygen?

Endothelial Injury Markers With High-dose IntravenousIron Therapy in Renal Failure

Endothelial injury is prevalent in patients with chronic renal failure (CRF) and may be exacerbated by commonly used intravenous (IV) iron therapy. The effects of high-dose IV iron sucrose treatment (200 mg daily in 250 mL of 0.9% saline, administered over 1 hour, median treatment duration 5 days) on circulating endothelium and/or tissue injury markers such as hepatocyte growth factor, thrombomodulin, von Willebrand factor, and C-reactive protein levels were studied. The markers were determined in 24 anemic (mean hemoglobin 9.48 g/dL) pre-dialysis (median creatinine clearance 21.5 mL/min) patients with CRF and defined absolute and/or functional iron deficiency. The measurements were performed before iron administration and 24 hours after the last infusion. All the markers remained unchanged following the IV iron therapy (all p < 0.172); no thrombotic or other adverse effects were observed. In conclusion, the above high-dose IV iron sucrose supplementation does not cause evident endothelial or other tissue injury in patients with CRF, and is clinically safe.

Evaluation of Oxidative Stress after Repeated Intravenous Iron Supplementation

Parenteral iron has been recommended for the treatment of iron deficiency in the majority of maintenance hemodialyzed (HD) patients. However, iron supplementation and consequent over saturation of transferrin and high iron levels, may aggravate oxidative stress already present in these patients. This study aimed to further clarify the role of repeated intravenous iron therapy as a supplementary cause of oxidative stress in HD patients. Markers of free radical activities (carbonyl reactive derivatives, CRD, thiol groups, SH, malondialdehyde, MDA) and antioxidant enzyme activities (superoxide dismutase, SOD and glutathione peroxidase, GPX) were determined in plasma and red blood cells (RBC) of 19 hemodialysis patients given a total iron dose of 625 mg (ferrogluconat, Ferrlecit, 62.5 mg). Blood samples were taken before the first and after the last dose of iron. Twenty apparently normal subjects served as healthy controls. Before iron treatment, HD patients exhibited increased concentrations of MDA and CRD in plasma and red blood cells, accompanied with impaired antioxidant capacity. All patients responded to iron therapy with a significant increase in their serum ferritin, serum iron, hemoglobin, and red blood cells levels. However, iron treatment resulted in enhanced oxidative stress in plasma of HD patients, since significant increase in plasma MDA and CRD concentrations, together with a decrease in nonprotein SH groups levels were detected. Supplementation with iron did not significantly influence plasma SOD and GPX activities, nor did any of the red blood cell parameters tested. Our data show that, despite improvement in hematological parameters, an increase in iron stores due to supplementation could also contribute to increased free radical production in HD patients.

Anaemia as a risk factor for the progression of chronic kidney disease

PURPOSE OF REVIEW

About a dozen controlled clinical trials examined the effect of anaemia correction on the progression of chronic kidney disease. None of these studies fulfilled the stringent criteria of a randomized controlled trial as suggested by the CONSORT statement, yet evidence emerged that anaemia sustains mitogenic and fibrogenic stimuli by lowering local partial oxygen tension. This review addresses the question of why and how anaemia could possibly enhance the progression of chronic kidney disease, and summarizes relevant clinical trials.

RECENT FINDINGS

The discovery of hypoxia-inducible factor, a transcription factor stabilized under hypoxic conditions, with DNA-binding properties towards about 50 target genes including erythropoietin, has largely encouraged the hypothesis that tissue hypoxia may serve as another common mechanism for the progression of chronic kidney disease besides hypertension or proteinuria. In addition, anaemia-mediated alterations of renal sympathetic nerve activity and anaemia-related increments of oxidative stress may contribute to a progressive nephron loss. Conclusive evidence from clinical trials is scarce.

SUMMARY

Pathophysiological concepts suggest some impact of anaemia on the progression of chronic kidney disease. The urge for more sound clinical intervention trials is met by the ongoing ECAP study (Effect of early Correction of Anaemia on the Progression of chronic kidney disease).