Endocrinology and Pd: Optimal Treatment of Anemia in Peritoneal Dialysis Patients

The optimal treatment of anemia in peritoneal dialysis is given by subcutaneous administration of epoetin. The optimal dosing frequency is in most patients 2 -3 injections per week, but in responsive patients once a week may be enough during the maintenance phase. Both before starting and during epoetin treatment it is necessary to monitor for factors causing hyporesponsiveness. The epoetin dose is adjusted monthly aiming at an increase in Hb concentration of 10 g/L per month. Further studies are required to define the optimal target Hb concentration. Iron supplements should be administered routinely. Parenteral iron may be used liberally when oral supplements are ineffective or inconvenient.

In the initial three-month period of peritoneal dialysis a marked increase in Hb concentration is common, and if epoetin treatment is necessary low starting doses will be sufficient. In patients with moderate anemia, adequate iron stores and iron availability, and no significant comorbidity, low starting doses are recommended (50 75 U kg-1 week-1). Patients with severe anemia or with comorbidity usually require higher doses and may be started with 75 150 kg-1 week-1. Hypertension is the principal adverse effect of epoetin treatment in patients with chronic renal failure, but it is usually easily controlled by fluid control and/or increased antihypertensive medication.

Peritoneal effects of intravenous iron sucrose administration in rats

Intravenous iron supplementation is commonly used in uremic patients treated with peritoneal dialysis. Infusion of iron compounds results in various systemic noxious effects, mainly because of its prooxidant and proinflammatory actions. The authors studied how the intravenous infusion of iron sucrose (IS) affects intraperitoneal homeostasis in rats undergoing acute peritoneal dialysis. Experiments were performed on Wistar rats, which were infused intravenously with IS in a dose 10 mg/kg body weight or with normal saline in the controls. Simultaneously, 4-hour acute peritoneal dialysis was started. At the end of the dialysis, systemic and peritoneal inflammatory reaction and peritoneal permeability were evaluated. Compared with controls, rats exposed to IS showed increased dialysate iron concentration by +70%, P<0.001, and in the differential cell count, more eosinophils (+113%, P<0.05) and fewer macrophages (-16%, P<0.05) existed. In in vitro conditions, macrophages obtained from IS-treated rats released more tumor necrosis factor-alpha (TNF-alpha; +173%, P<0.05) upon stimulation with endotoxin. Additionally increased (+73%, P<0.01) dialysate elastase activity was found in IS-treated animals. Rats infused with IS demonstrated increased peritoneal permeability to total protein (+60%, P<0.001) as compared with control animals. When rats with simultaneous peritonitis received intravenous IS, ex vivo isolated peritoneal leukocytes generated more free radicals (+73%, P<0.05) than did cells harvested from control animals. It has been concluded that intravenous infusion of IS affects the intraperitoneal homeostasis in rats, moving it toward the inflammatory state. These changes may contribute to peritoneal damage.

Intravenous versus Oral Iron Supplementation in Peritoneal Dialysis Patients

Iron supplementation is required in a preponderance of peritoneal dialysis (PD) patients treated with erythropoietic stimulatory agents (ESAs). Although many authors and clinical practice guidelines recommend primary oral iron supplementation in ESA-treated PD patients, numerous studies have clearly demonstrated that, because of a combination of poor bioavailability of oral iron, gastrointestinal intolerance, and noncompliance, oral iron supplementation is insufficient for maintaining a positive iron balance in these patients over time. Controlled trials have demonstrated that, in iron-deficient and iron-replete PD patients alike, intravenous (IV) iron supplementation results in superior iron stores and hemoglobin levels with fewer side effects than oral iron produces. Careful monitoring of iron stores in patients receiving IV iron supplementation is important in view of conflicting epidemiologic links between IV iron loading and infection and cardiovascular disease. Emerging new iron therapies such as heme iron polypeptide and ferumoxytol may further enhance the tolerability, efficacy, and ease of administration of iron in PD patients.

The efficacy and safety of once-weekly and once-fortnightly subcutaneous epoetin β in peritoneal dialysis patients with chronic renal anaemia

BACKGROUND

Reducing the dosage frequency of subcutaneous epoetin in peritoneal dialysis (PD) patients is convenient and should improve patient satisfaction and, possibly, compliance. We investigated if a weekly dosage of epoetin beta in PD patients safely maintained haemoglobin (Hb) concentrations equivalent to those obtained with previous twice- or thrice-weekly administration. In addition, we investigated if a fortnightly dosage of epoetin beta was safe and as effective as previous weekly administration.

METHODS

After a 4 week run-in period, PD patients were switched to either weekly or fortnightly epoetin beta administration, depending on their previous treatment schedules, for 25 weeks.

RESULTS

The per-protocol cohort included 128 patients, of whom 54 received epoetin beta once weekly and 74 once fortnightly. The mean change in Hb concentration from baseline over weeks 13-25 and the 90% confidence intervals (CIs) remained within the target range (10-12 g/dl) and specified equivalence (+/-0.75 g/dl) limits in the weekly (-0.34 g/dl; 90% CI: -0.14 to -0.54 g/dl) and fortnightly (-0.39 g/dl; 90% CI: -0.24 to -0.55 g/dl) cohorts. The mean change from baseline in the epoetin beta dose was 1.4 IU/kg/week (90% CI: -3.8 to 6.6 IU/kg/week; 2%) in the weekly cohort and 4.4 IU/kg/week (90% CI: 1.7-7.2 IU/kg/week; 13%) in the fortnightly cohort. Both treatment regimens were well tolerated.

CONCLUSIONS

In stable PD patients switched from twice- or thrice-weekly to weekly epoetin beta treatment, Hb concentrations could be maintained within the specified range over 25 weeks without significant change in their mean epoetin beta doses. In patients switched from weekly to fortnightly treatment, Hb concentrations could also be maintained over 25 weeks. There was a small increase in the mean dose during this period, but >/=50% of patients could be maintained without dose increase. Reducing dosage frequency may improve compliance in PD patients who self-administer their epoetin.

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.