Iron absorption in patients with chronic uremia undergoing regular hemodialysis

Intradialytic Oral Iron Therapy

In order to test the limits of what can be achieved with oral iron therapy and eliminate the factor of noncompliance, we conducted a series of observational studies in an 140-patient inner city dialysis unit. In these studies the patients received supervised iron therapy as 3-4 ferrous sulfate (325 mg) tablets during each dialysis. Acceptance and tolerance was high, less than 10% refusing to take the tablets. In two separate observational studies oral intradialytic iron yielded a hematocrit 28% in 69% of patients and 30% in 42-52%. There was no correlation between the final hematocrit and serum ferritin or transferrin saturation. The response to iron therapy could frequently not be predicted by the ferritin levels or transferrin saturation. We conclude that in view of the known hazards of intravenous iron dextran, oral intradialityc therapy should be tried first and that a good response can be expected in one half to two thirds of hemodialysis patients.

Iron absorption after renal transplantation

Gastrointestinal iron absorption has been measured by means of whole body counting in 13 patients after renal allotransplantation. Whole body retention 14 days after oral administration of 10 muCi 59Fe together with a carrier dose of 9.9 mg Fe2+ was used as an expression of absorption. The percentage incorporation in the total erythrocyte mass of administered 59Fe (erythrocyte incorporation) and absorbed 59Fe (red cell utilization) was estimated as well. Geometric mean iron absorption was 12.4 +/- 2.5 (S.D.)% and geometric mean erythrocyte incorporation 11.1 +/- 3.0 (S.D.)% while arithmetic mean red cell utilization was 95.6 +/- 8.6 (S.E.M.)%. None of these parameters differed significantly from those obtained in normal subjects (p greater than 0.2, p greater than 0.1, pgreater than 0.3, respectively). Iron absorption and erythrocyte incorporation in renal transplanted patients did not differ significantly from the values measured in non-dialysed and dialysed patients with chronic renal failure (p greather than 0.1). The correlation between iron absorption and erythrocyte incorporation was highly significant (r = 0.96, p less than 0.001).

Iron therapy in patients undergoing maintenance hemodialysis

Twelve patients in maintenance hemodialysis, receiving long-term oral iron therapy, have been treated with i.v. iron dextran, in order to evaluate the effect on the Hb level. Both Hb and hematocrit were unchanged before and after the iron dextran infusion (p greater than 0.5, p greater than 0.7, respectively). Oral iron therapy is usually sufficient to maintain an adequate iron balance in dialysed patients and should be preferred to parenteral iron in view of the better utilization and absence of side-effects. The indication for parenteral iron should be limited to patients with impaired gastrointestinal iron absorption.

Iron absorption and iron status in patients with chronic uremia on regular peritoneal dialysis

Gastrointestinal iron absorption was measured by whole body counting in 18 patients on regular peritoneal dialysis. Ten patients received regular oral iron treatment prior to the study (iron treated group), 8 patients did not receive iron treatment (non-iron treated group). Whole body retention 14 days after oral administration of 10 microCi 59Fe together with a carrier dose of 10 mg Fe2+ was used as an estimate of absorption. The erythrocyte iron incorporation, i.e. the percentage of administered 59Fe incorporated into the total erythrocyte mass, was measured. Geometric mean iron absorption in the non-iron treated groups was 7.4+/-3.3 (S.D.) % and in the iron treated group 2.8+/-2.5% (p less than 0.01). Absorption in the non-iron treated group did not differ significantly from the value in a normal control group (p greater than 0.3). Absorption in the iron treated group was distinctly lower than in the controls (p less than 0.01), due to the high iron supplementation. Several patients in the non-iron treated group had latent or overt iron deficiency, while patients in the iron treated group had satisfactory iron status. The correlation between iron absorption and erythrocyte iron incorporation was highly significant (r=0.95, p less than 0.001). Peritoneal dialysis patients on the whole have a normally functioning iron absorption. However, due to increased iron losses and insufficient dietary iron intake, the maintenance of a satisfactory iron balance implies an adequate oral iron supplementation.

Iron status and iron supplementation in peritoneal dialysis patients

Iron deficiency represents an important problem in peritoneal dialysis patients, especially during erythropoietin therapy. A combination of serum ferritin, transferrin saturation, and/or the percentage of hypochromic red cells should be used to assess iron status in peritoneal dialysis patients. Primarily, oral iron supplementation should be the preferred therapy. However, most of the studies using oral substitution in erythropoietin-treated peritoneal dialysis patients show a progressive decline of serum ferritin. Therefore, parenteral iron supplementation is required in part of the patients, and the intravenous route should be preferred in these cases. Intravenous iron therapy is recommended if serum ferritin falls below 100 microg/liter and should be stopped if the serum ferritin level is more than 650 microg/liter. The optimal form of intravenous iron supplementation is still unclear. Injections once to three times per week restrict the patients' flexibility, but application of higher doses in longer intervals may lead to an impairment of neutrophil functions, probably connected to a higher risk of infection. We treated 17 stable peritoneal dialysis patients with 100 or 200 mg iron saccharate monthly over a period of six months and found an increase of transferrin saturation (from 12.1+/-1.6 to 20.9+/-2.4%, P = 0.026), serum ferritin (from 100.4+/-32.0 to 372.4+/-54.6 microg/liter, NS) and hematocrit (from 32.0+/-0.8% to 35.1+/-0.9%, P = 0.099). The required erythropoietin dosage could be reduced significantly (from 148.4+/-30.3 to 69.4+/-19.5 U/kg/week, P = 0.025). Side effects occurred in 0.9% after application of 100 mg and in 5.9% after injection of 200 mg iron saccharate. The incidence of catheter infections and peritonitis was the same in the period before and after the start of treatment. Further studies are needed to find the most suitable regime of iron supplementation for peritoneal dialysis patients.

Effective utilization of erythropoietin with intravenous iron therapy

INTRODUCTION

Iron replacement therapy reduces the demand for erythropoietin (EPO) in some dialysis patients. It has been postulated that iron supply to the bone marrow is a rate-limiting step in the process of erythropoiesis under erythropoietin stimulation.

METHODS

We evaluated the economic benefit of intravenous iron therapy for this purpose in a prospective, non-blinded study of 22 haemodialysis patients, 16 male, six female, mean age 62 years (range 24-80 years). All patients had a serum ferritin (SF) of < or = 60 microg/L, despite oral iron therapy. Patients with high aluminium and/or parathyroid hormone (PTH) levels, underlying bleeding/haematological disorders or active inflammatory diseases were excluded. Patients were established on subcutaneous EPO and given intravenous iron over seven consecutive dialysis sessions (total dose 1050 mg) and supplemental monthly doses with regular monitoring for 4 months.

RESULTS

The median EPO dose was 4000 units/week (mean 6050 units/week) pre-treatment and 2000 units/week (mean 3700 units) at 6 weeks post intravenous iron therapy (P=0.03). No serious adverse events occurred in the 154 treatment sessions of intravenous iron. Mean haemoglobin (Hb) level remained constant at 6 and 12 weeks (P=0.087). Serum ferritin levels (P< 0.0001) rose significantly, while a reduction in transferrin saturation (TS) became significant at the end of the study (P=0.0047). The use of intravenous iron allowed a substantial monthly cost saving per patient in our unit.

CONCLUSION

Intravenous iron therapy is a safe and cost-effective method for maintaining or improving Hb levels with a more effective utilization of EPO in patients with low SF levels despite oral iron therapy.

Evaluation of RBC ferritin and reticulocyte measurements in monitoring response to intravenous iron therapy

Intravenous (IV) iron therapy can reduce erythropoietin (EPO) requirements in dialysis patients. Monitoring this response accurately is difficult. Estimation of red blood cell ferritin (RBCFer) and reticulocyte indices may give additional valuable information about iron availability to the erythroblasts (erythron). We evaluated the use of RBCFer, mean hemoglobin content of reticulocytes (CHr), and mean hemoglobin concentration of reticulocytes (CHCMr) in a prospective, nonblinded study of 22 hemodialysis patients (16 men and six women with a mean age of 62 years [range, 24 to 80 years]). All patients had an initial serum ferritin of < or = 60 microg/L. Patients with features known to produce EPO resistance and underlying bleeding/hematologic disorders were excluded. Patients were established on subcutaneous EPO and given IV iron therapy. The mean hemoglobin level remained constant throughout the study (P = 0.087). Serum ferritin and RBCFer increased significantly (P < 0.001 and 0.015, respectively) while a reduction in transferrin saturation became significant at the end of the study (P = 0.0047). A sharp increase in reticulocytes occurred in the first 14 days after commencement of IV iron, and there was an initial decrease in the percentage of hypochromic RBCs. An early decline in RBCFer was apparent. CHr increased with IV iron, indicative of increased iron supply to the developing erythron. Measurement of RBCFer and CHr provide evidence of increased iron supply for erythropoiesis during IV iron therapy. These measures help identify patients with functional iron deficiency and allow more accurate monitoring of response to IV iron therapy.