Beneficial effects of iron therapy in renal failure patients on hemodialysis

Evolution of iv iron compounds over the last century

Administration of intravenous (IV) iron has become pivotal in the management of anaemia in patients with chronic kidney disease (CKD). Since parenteral iron was first introduced for human use in the 1930s, things have come a long way. Seventy years ago, iron was toxic, administered as an iron oxyhydroxide complex. This problem was circumvented with the introduction of compounds containing iron in a core surrounded by a carbohydrate shell. The carbohydrate shell consists of molecules such as dextran, sucrose, dextrin or gluconate. The first dextran-containing IV iron preparations carried a small risk of anaphylaxis, but the more recently introduced low molecular weight iron dextran preparation has significantly less risk of this. Iron reactions occur with all IV iron preparations, but are generally not thought to be immune based. Recently, newer IV iron preparations have appeared in the market, including Ferumoxytol (Feraheme) and ferric carboxymaltose (Ferinject). These latest IV iron preparations do not contain a requirement for a test dose, and a much higher dose of iron can be delivered as a single administration. Thus, giving supplemental iron to man has come a long way since 1930s; we are now in an era when we are able to administer higher doses of iron with acceptable safety and without significant adverse effects. However, the long-term safety of the newer IV iron preparations is not yet established.

The use of intravenous iron in patients with cancer-related anaemia

Intravenous iron has become the standard of care in patients with renal failure receiving treatment with erythropoiesis stimulating agents (ESAs) to treat true and functional iron deficiency and to prevent its development in haemodialysis patients. In cancer-related anaemia, several recently published, randomised studies suggested that intravenous iron improved haemoglobin response rates in ESA-treated patients compared to those treated with oral iron or placebo. The data supporting the efficacy of intravenous iron instead of oral iron in this setting are increasingly persuasive but larger randomised trials are needed before definitive recommendations are made.

Iron management in nondialysis-dependent CKD

Iron deficiency has been studied extensively in patients with chronic kidney disease on hemodialysis therapy. However, few studies looked at iron treatment in the nondialysis chronic kidney disease population. Limited data suggest that iron deficiency is common in patients with chronic kidney disease with anemia; this lack of iron can hinder the effectiveness of erythropoiesis. The diagnosis of iron deficiency should involve clinical judgment, with an emphasis on clinical characteristics of the patient because of the limited amount of literature examining the interpretation of iron testing results. When iron deficiency is diagnosed in nondialysis patients with chronic kidney disease, a search must be initiated for any sources of blood loss. After addressing any blood loss, the preferred route of iron treatment must be determined. To date, no clear advantage was shown with intravenous versus oral administration in nondialysis patients, as shown in the hemodialysis setting. Thus, oral iron therapy may be a more reasonable option unless oral therapy previously failed. Additional research is needed to support evidence-based guidelines for the treatment of iron deficiency in the nondialysis chronic kidney disease population because this population differs from hemodialysis patients in the decreased extent of blood loss.

Renal anaemia: recent developments, innovative approaches and future directions for improved management

The morbidity, mortality and economic burden of chronic kidney disease (CKD) and associated anaemia are substantial. With the increasing numbers of patients who are likely to be affected in the future, approaches are required to improve anaemia management without increasing the burden on health-care professionals. A multidisciplinary approach to treatment, where early initiation of erythropoiesis-stimulating agents (ESA) is encouraged, may improve patient outcomes. Recent studies also suggest that the early use of iron therapy in patients with CKD not on dialysis may be associated with beneficial effects on haemoglobin levels. Another strategy to reduce the burden on health-care providers is to simplify anaemia management by extending the administration interval of ESA. Indeed, recent studies have explored the efficacy of extending the administration interval of ESA in clinical practice in CKD patients on dialysis and not on dialysis. The ability to maintain haemoglobin levels within guideline ranges at extended administration intervals may improve patient care and reduce the workload of health-care providers.

Intermittent versus maintenance iron therapy in children on hemodialysis: a randomized study

In patients with renal anemia, iron therapy can be administered intermittently or regularly at a low dose. We performed a randomized clinical trial in pediatric patients with end-stage renal failure on hemodialysis and absolute or functional iron deficiency. The study group received maintenance iron therapy according to the ferritin serum levels and the control group received intermittent 10-weekly doses. Success was defined as stabilization of ferritin levels between 100 and 800 microg/l and transferrin saturation (TSAT) between 20% and 50%, in addition to an increase in the hemoglobin level. The major reason for exclusion was iron overload. The study group received 6 mg/kg per month of parenteral iron [95% confidence interval (CI) 3.3-8.8] and the control group 14.4 mg/kg per month (95% CI 12-16.8) ( P<0.001). After 4 months of treatment, ferritin levels increased to 66 microg/l (95% CI 69-200) in the study group and to 334 microg/l (95% CI 145-522) in the control group ( P=0.009). Maintenance therapy and intermittent weekly doses were successful in 73% and 38%, respectively. After 3 months of treatment, hemoglobin levels increased to 10 g/dl, with no difference between the groups. However, in the control group the increase in hemoglobin levels was unsustained, and 3 patients needed transfusion. Patients in the control group had a higher risk of iron overload than patients in the study group (70% vs. 19%). Thus, the regimen based on assessment of serum ferritin levels was more efficient than the intermittent regimen because it increased and maintained the hemoglobin levels with lower iron doses and a lower risk of iron overload.

Evaluation of intestinal iron absorption by indirect methods in patients on hemodialysis receiving oral iron and recombinant human erythropoietin

Intestinal iron absorption was evaluated in 40 patients on hemodialysis therapy treated over 4 months with 105 mg/d of oral iron and recombinant human erythropoietin (rHuEPO). The effect of iron stores, erythropoietic activity (EA), and route of rHuEPO administration on absorption was evaluated. Iron was administered after basal determinations had been made and was stopped 15 days before obtaining the final determinations. Intestinal iron absorption was calculated by summing the increase in hemoglobin (Hb) iron (iron used for the synthesis of new Hb) and variations in estimated tissue iron reserves (reserves at the end of the study minus basal reserves). Markers of EA included soluble transferrin receptors (sTfRs) and erythron transferrin uptake (ETU). Iron losses caused by dialysis or normal obligatory iron losses were not measured. Hb levels increased from 8.38 +/- 1.4 to 10.75 +/- 1.5 g/dL (P < 0.05). sTfR levels reached their maximum value at 45 days (3.22 +/- 0.84 mg/mL; P < 0.05), and ETU increased from 40 +/- 26 to 61 +/- 39 micromol/L whole blood/d (P = 0.007). Intestinal iron absorption was 238 mg (interquartile range [Q75 to Q25], 255) at 2 months and 348 mg (Q75 to Q25, 475) at 4 months (P =0.02) and correlated positively with hematocrit at the end of the study (r = 0.826; P = 0.0001). No relationship between iron absorption and basal serum ferritin level or EA markers was observed. Intestinal iron absorption was similar regardless of the route of rHuEPO administration. In conclusion, intestinal iron absorption from medicinal iron covers erythropoietic requirements and allows Hb levels to increase significantly. It is proportional to the degree of efficient erythropoiesis reached and independent of tissue iron stores present before treatment, markers of EA, and rHuEPO administration route.

Effects of erythropoietin therapy on iron absorption in chronic renal failure

The effect of erythropoietin administration on the absorption of dietary and therapeutic iron was examined in patients with anemia of chronic renal failure on maintenance hemodialysis. Absorption from test meals tagged extrinsically with iron 55, iron 59, or both was determined 2 weeks later by using incorporated red blood cell radioactivity and whole body counting. In an initial study of food iron absorption, the effect of initiating erythropoietin therapy was determined by measuring the absorption of heme and nonheme iron before and 2 weeks after the administration of 64 U/kg body weight erythropoietin (range, 46-85 U/kg body weight) three times weekly. Absorption of heme iron increased 1.6-fold from 18.6% to 30.1% (P < .05), and nonheme iron increased 3.7-fold from 1.3% to 4.9% (P < .01) after erythropoietin therapy. In a second study therapeutic iron absorption was evaluated at baseline and after erythropoietin administration (63 U/kg body weight (range, 48-74 U/kg body weight) three times weekly). The absorption of 50 mg of iron as ferrous sulfate increased 2.4-fold from 3.8% to 9.4% (P < .05) when given without food and 4.2-fold from 1.4% to 5.9% (P < .05) when given with food after erythropoietin administration. After adjusting for changes in iron stores with serum ferritin after erythropoietin therapy, the enhanced erythropoiesis associated with erythropoietin therapy increased absorption about 2-fold, which was similar to the response observed previously in normal subjects. In a final study we examined the absorption of therapeutic iron during the steadystate phase of erythropoietin therapy after an erythroid response to erythropoietin had occurred. The absorption of 50 mg of iron was lower than that occurring with the initiation of erythropoietin therapy at 2.2% when given alone and 1.3% when taken with food. We conclude that iron absorption with or without erythropoietin stimulation is unimpaired in patients with chronic renal failure.

Anemia management of adult hemodialysis patients in the US results: from the 1997 ESRD Core Indicators Project

BACKGROUND

The Health Care Financing Administration's End-Stage Renal Disease (ESRD) Core Indicators Project collects clinical information on prevalent adult patients receiving in-center hemodialysis (HD) care in the United States to assess the quality of care delivered. Although hematocrit values, transferrin saturations, and iron prescription practices have improved over the last five years, we sought to determine whether continued opportunities for improvement of this domain of care exist.

METHODS

A random sample of 7292 adult in-center HD patients was selected. Dialysis facility staff provided clinical information for the period of October through December 1996 for 6858 (94%) patients; complete laboratory information was available from 4991 (73%) returned forms. Hematocrit values, transferrin saturations, serum ferritin concentrations, epoetin alfa dosing, and iron prescriptions were abstracted from patient medical records to assess anemia management practices.

RESULTS

The mean hematocrit for this cohort was 32.6 +/- 3.5%. Seventy-two percent of patients had hematocrit values> 30%. Forty-two percent had hematocrit values of 33 to 36%, and 10% were severely anemic (hematocrit <28%). Ninety-four percent of the patients received epoetin alfa intravenously (i.v.) and 6% subcutaneously. The mean weekly dose was 202.4 +/- 137.2 units/kg. The mean transferrin saturation was 27.4 +/- 12.6%; 73% of patients had a mean transferrin saturation > or = 20%. The mean serum ferritin concentration was 386 +/- 422 ng/mL; 79 and 12% of patients had a serum ferritin concentration of> 100 and> 800 ng/mL, respectively. Nine percent of the sample (N = 434) had a transferrin saturation <20% and serum ferritin concentration <100 ng/mL. Regardless of the patient's transferrin saturation, approximately three fourths of the patients received either oral or i.v. iron, and only approximately one half of the patients received i.v. iron. Of the subset of patients with transferrin saturation <20% and serum ferritin concentration <800 ng/mL, only 53% were prescribed intravenous iron. Multivariate linear regression analysis revealed that serum albumin, urea reduction ratio, age, and transferrin saturation were significantly positively associated with hematocrit. Epoetin alfa dose and serum ferritin concentration were significantly and negatively associated with the hematocrit (P < 0.001).

CONCLUSION

Although substantial improvements have been made in anemia management for adult in-center HD patients over the past five years, significant opportunities persist to improve iron prescription practices.