Intravenous ascorbic acid as an adjuvant therapy for recombinant erythropoietin in hemodialysis patients with hyperferritinemia

Assessment and management of vitamin status in children with CKD stages 2-5, on dialysis and post-transplantation: clinical practice points from the Pediatric Renal Nutrition Taskforce

Children with chronic kidney disease (CKD) are at risk for vitamin deficiency or excess. Vitamin status can be affected by diet, supplements, kidney function, medications, and dialysis. Little is known about vitamin requirements in CKD, leading to practice variation.The Pediatric Renal Nutrition Taskforce (PRNT), an international team of pediatric kidney dietitians and pediatric nephrologists, was established to develop evidence-based clinical practice points (CPPs) to address challenges and to serve as a resource for nutritional care. Questions were formulated using PICO (Patient, Intervention, Comparator, Outcomes), and literature searches undertaken to explore clinical practice from assessment to management of vitamin status in children with CKD stages 2-5, on dialysis and post-transplantation (CKD2-5D&T). The CPPs were developed and finalized using a Delphi consensus approach. We present six CPPs for vitamin management for children with CKD2-5D&T. We address assessment, intervention, and monitoring. We recommend avoiding supplementation of vitamin A and suggest water-soluble vitamin supplementation for those on dialysis. In the absence of evidence, a consistent structured approach to vitamin management that considers assessment and monitoring from dietary, physical, and biochemical viewpoints is needed. Careful consideration of the impact of accumulation, losses, comorbidities, and medications needs to be explored for the individual child and vitamin before supplementation can be considered. When supplementing, care needs to be taken not to over-prescribe. Research recommendations are suggested.

Two Faces of Vitamin C in Hemodialysis Patients: Relation to Oxidative Stress and Inflammation

Hemodialysis (HD) is the most common method of renal replacement therapy. Besides toxins, it eliminates nutrients from the circulation, such as ascorbic acid (AA). HD-patients present AA deficiency more often than representatives of the general population, also due to dietary restrictions. This condition aggravates oxidative stress and inflammation related to uremia and extracorporeal circulation and increases cardiovascular risk followed by mortality. Supplementation of AA seems to be a promising approach in the treatment of hemodialysis patients. Many successful interventions restored plasma AA concentration in HD patients by enteral or intravenous supplementation, concomitantly inhibiting oxidative stress and inflammation. A significant number of studies reported opposite, serious pro-oxidant effects of AA. In this narrative review, we present studies, commenting on their limitations; on AA plasma or serum concentration and the influence of its supplementation on protein and lipid peroxidation, DNA damage, reactive oxygen species generation, paraoxonase activity, advanced glycation endproducts, and C-reactive protein (CRP) concentration. Moreover, in terms of safety, the possible development of oxalosis in HD patients regarding the intravenous or enteral route of AA administration is discussed. Unequivocal clinical results of recent studies on hemodialysis patients are displayed.

Vitamin C deficiency and impact of vitamin C administration among pediatric patients with advanced chronic kidney disease

BACKGROUND

Vitamin C deficiency is common in chronic kidney disease (CKD) due to losses through dialysis and dietary intake below requirement. We investigated prevalence of vitamin C deficiency and impact of vitamin C treatment in deficient/insufficient patients.

METHODS

A prospective cohort study in patients aged 1-18 years with CKD stages 4 and 5D collected demographic data including underlying disease, treatment, and anthropometric assessment. Vitamin C intake was assessed using 24-h dietary recall. Hemoglobin, iron status, serum vitamin C, and serum oxalate were measured at baseline and after treatment. Vitamin C (250 mg/day) was given orally for 3 months to deficient/insufficient patients.

RESULTS

Nineteen patients (mean age 12.00 ± 4.1 years) showed prevalence of 10.6% vitamin C insufficiency and 78.9% deficiency. There were no associations between vitamin C level and daily vitamin C intake (p = 0.64) or nutritional status (p = 0.87). Median serum vitamin C was 1.51 (0.30-1.90) mg/L. In 16 patients receiving treatment, median serum vitamin C increased from 1.30 (0.23-1.78) to 3.22 (1.77-5.96) mg/L (p = 0.008) without increasing serum oxalate (79.92 (56.6-106.84) vs. 80.47 (56.88-102.95) μmol/L, p = 0.82). However, 62.5% failed to achieve normal vitamin C levels. Ordinal regression analysis revealed patients with non-oligoanuric CKD were less likely to achieve normal vitamin C levels (β = - 3.41, p = 0.03).

CONCLUSION

We describe high prevalence of vitamin C insufficiency/deficiency among pediatric CKD patients. Vitamin C levels could not be solely predicted by nutritional status or daily intake. The treatment regimen raised serum vitamin C without increasing serum oxalate; however, it was largely insufficient to normalize levels, particularly in non-oligoanuric CKD. Graphical abstract .

Plasma vitamin C levels in ESRD patients and occurrence of hypochromic erythrocytes

INTRODUCTION

The achievement of erythropoiesis in hemodialysis (HD) patients is typically managed with erythropoiesis-stimulating-agents (ESA's) and intravenous iron (IV-iron). Using this treatment strategy, HD patients frequently show an elevated fraction of red blood cells (RBC) with hemoglobin (Hb) content per cell that is below the normal range, called hypochromic RBC. The low Hb content per RBC is the result of the clinical challenge of providing sufficient iron content to the bone marrow during erythropoiesis. Vitamin C supplements have been used to increase Hb levels in HD patients with refractory anemia, which supports the hypothesis that vitamin C mobilizes iron needed for Hb synthesis.

METHODS

We conducted a cross-sectional survey in 149 prevalent HD patients of the percent hypochromic RBC, defined as RBC with Hb < 300 ng/uL of packed RBC, in relation to plasma vitamin C levels. We also measured high-sensitivity CRP, (hs-CRP), iron, and ferritin levels. and calculated ESA dose.

FINDINGS

High plasma levels of vitamin C were negatively associated with hypochromic RBC (P < 0.003), and high ESA doses were positively associated (P < 0.001). There was no significant association of hs-CRP with percent hypochromic RBC.

DISCUSSION

This finding supports the hypothesis that vitamin C mobilizes iron stores, improves iron delivery to the bone marrow, and increase the fraction of RBC with normal Hb content. Further research is warranted on development of protocols for safe and effective use of supplemental vitamin C for management of renal anemia.

Oral vitamin C supplementation reduces erythropoietin requirement in hemodialysis patients with functional iron deficiency

PURPOSE

Functional iron deficiency (FID) is a major cause of persistent anemia in dialysis patients and also contributes to a suboptimal response to erythropoietin (Epo) administration. Vitamin C acts as an enzyme cofactor and enhances mobilization of the ferrous form of iron to transferrin thus increasing its bioavailability. High-dose intravenous vitamin C has been shown to decrease the Epo requirement and improve hemoglobin levels in previous studies. This study assessed the effect of low-dose oral vitamin C on possible reduction in Epo dose requirements in stable hemodialysis patients with FID.

METHODS

This prospective study included 22 stable hemodialysis patients with FID defined as transferrin saturation (T sat) <30 % and ferritin levels of >100 mcg/L with Epo requirement of ≥4000 U/HD session. Patients received oral vitamin C 250 mg daily for 3 months. Hemoglobin, iron and T sat levels were recorded monthly. No one received iron supplementation during the study period.

RESULTS

There was a significant reduction in median Epo dose requirement in the 15 patients who completed the study, from 203.1 U/kg/week (95 % CI 188.4-270.6) to 172.8 U/kg/week (95 % CI 160.2-214.8), (P = 0.01). In the seven responders, there was 33 % reduction in Epo dose from their baseline. Despite adjustment of Epo dose, the mean hemoglobin level was significantly increased from 10.1 ± 0.6 to 10.7 ± 0.6 mg/dL (P = 0.03). No adverse effects of oral vitamin C were observed.

CONCLUSION

Daily low-dose oral vitamin C supplementation reduced Epo dose requirements in hemodialysis patients with FID. Limitations of this study include a small sample size and the lack of measurements of vitamin C and oxalate levels. Despite concerns regarding oral vitamin C absorption in dialysis patients, this study indicates vitamin C was well tolerated by all participants without reported adverse effect.

Effect of protoconized therapy for renal anemia on adverse events of patients with maintenance hemodialysis

PURPOSE

We evaluate the effect of the protoconized anemia therapy on adverse events using the Hb and ferritin levels of individual patients undergoing maintenance hemodialysis (MHD).

METHODS

Design: A randomized, parallel group, multi-center study.

PATIENTS

Two hundred sixty-six MHD patients. Intervention group: The doses of erythropoietin, iron, and vitamin C were adjusted every month based on the ferritin and hemoglobin (Hb) levels according to the protocol. Non-intervention group: The attending physician determined the doses of erythropoietin and iron.

RESULTS

The maintenance rate of target Hb and ferritin levels were significantly higher in the Intervention group than in the Non-intervention group. The frequency of hospitalization was significantly lower for patients with a higher maintenance rate of target Hb levels than for those with a lower maintenance rate.

CONCLUSIONS

Using an anemia treatment protocol according to the individual Hb and ferritin levels of hemodialysis patients might stabilize the Hb and ferritin levels, which in turn could contribute to the lower frequency of adverse events in MHD patients.

Plasma ascorbic acid concentrations in prevalent patients with end-stage renal disease on hemodialysis

OBJECTIVE

To determine the prevalence of vitamin C (ascorbic acid [AA]) deficiency in patients with end-stage renal disease, the effect of supplemental AA on plasma AA concentrations, and the extrinsic and intrinsic factors that affect plasma AA concentrations in this patient population.

DESIGN

In study 1, we compared the effect of hemodialysis (HD) on plasma AA concentrations between patients with low and high pre-HD AA concentrations. In study 2, we analyzed kinetic and nonkinetic factors for their association with increased plasma AA concentrations in patients on maintenance HD. Study 1 was performed in a single outpatient HD clinic in Cherry Hill, New Jersey. Study 2 was performed in 4 outpatient HD clinics in Southern New Jersey.

SUBJECTS AND INTERVENTION

In study 1, we collected plasma samples from 8 adult patients on maintenance HD at various time points around their HD treatment and assayed them for AA concentration. In study 2, we enrolled 203 adult patients and measured pre-HD plasma AA concentrations. We ascertained supplemental AA use and assessed dietary AA intake.

MAIN OUTCOME MEASURE

In study 1, plasma AA concentrations were compared during the intradialytic and interdialytic period. In study 2, pre-HD plasma AA concentrations were correlated with supplement use and demographic factors.

RESULTS

Study 1 showed that over the course of a single HD treatment, the plasma AA concentration decreased by a mean (±standard deviation) of 60% (±6.6). In study 2, the median pre-HD plasma AA concentration was 15.7 μM (interquartile range, 8.7-66.8) in patients who did not take a supplement and 50.6 μM (interquartile range, 25.1-88.8) in patients who did take a supplement (P < .001). Supplement use, increasing age, and diabetes mellitus were associated with a pre-HD plasma AA concentration ≥30 μM.

CONCLUSION

HD depletes plasma AA concentrations, and AA supplementation allows patients to achieve higher plasma AA concentrations.

Erythropoiesis-stimulating agents in chronic kidney disease: what have we learned in 25 years?

Since the pioneering studies by Eschbach et al in 1987, erythropoiesis-stimulating agents (ESAs) have become the mainstay of anemia therapy in chronic kidney disease (CKD) patients. The introduction of ESAs 25 years ago markedly improved the lives of many patients with CKD, who until then had severe, often transfusion-dependent anemia. However, randomized controlled trials demonstrate an increased risk for cardiovascular events such as stroke, thrombosis, and death at nearly normal hemoglobin concentrations and higher ESA doses in CKD. By contrast, kidney transplant recipients may represent a unique population of CKD patients who may benefit from ESA therapy. This review discusses potential mechanisms involving the erythropoietic and nonerythropoietic effects of ESA treatment and ESA resistance. Further research aimed at elucidating the causal pathways is strongly recommended. Given current knowledge, however, clinical practice should avoid disproportionately high dosages of ESAs to achieve recommended hemoglobin targets, particularly in those with significant cardiovascular morbidity or ESA resistance. The key to CKD anemia management will be individualization of the potential benefits of reducing blood transfusions and anemia-related symptoms against the risks of harm.

Interventions for erythropoietin-resistant anaemia in dialysis patients

BACKGROUND

People living with end-stage kidney disease (ESKD) often develop anaemia. Erythropoiesis-simulating agents (ESAs) are often given to people living with ESKD to maintain haemoglobin at a level to minimise need for transfusion. However, about 5% to 10% of patients with ESKD exhibit resistance to ESAs, and observational studies have shown that patients requiring high doses of ESA are at increased risk of mortality.

OBJECTIVES

This review aimed to study the effects of interventions for the treatment of ESA-resistant anaemia in people with ESKD.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE for randomised controlled trials (RCT) that involved participants with ESKD on dialysis or who were pre-dialysis patients with chronic kidney disease (stage 5). Date of last search: April 2013.

SELECTION CRITERIA

ESA resistance was defined as failure to achieve or maintain haemoglobin/haematocrit levels within the desired target range despite appropriate ESA doses (erythropoietin ≥ 450 U/kg/wk intravenously or ≥ 300 U/kg/wk subcutaneously; darbepoetin ≥ 1.5 µg/kg/wk) in people who were not nutritionally deficient, or who had haematological or bleeding disorders. Extended inclusion criteria for ESA hyporesponsive state were: erythropoietin dose ≥ 300 U/kg/wk and ≥ 150 U/kg/wk for intravenous administration; or ≥ 200 U/kg/wk and ≥ 100 U/kg/wk for subcutaneous administration; or darbepoetin dose ≥ 1.0 µg/kg/wk).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Statistical analyses were performed using a random effects model and results expressed as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

Titles and abstracts of 521 records were screened, of which we reviewed 99 from the full text. Only two studies matched our inclusion criteria. One study compared intravenous vitamin C versus no study medication for six months in 42 ESKD patients on haemodialysis who required intravenous erythropoietin (dose ≥ 450 U/kg/wk). The other included study compared high-flux dialyser versus low-flux dialyser for six months in 48 haemodialysis patients who required subcutaneous erythropoietin (dose ≥ 200 U/kg/wk). Because interventions differed, data could not be combined for quantitative meta-analysis.

AUTHORS' CONCLUSIONS

There was inadequate evidence identified to inform recommendation of any intervention to ameliorate ESA hyporesponsiveness. Adequately powered RCTs are required to establish the safety and efficacy of interventions to improve responsiveness to ESA therapy.

Is vitamin C intake too low in dialysis patients?

Vitamin C has several well-established roles in physiology including synthesis of collagen, carnitine and epinephrine, absorption of dietary iron, and mobilization of storage iron for erythropoeisis. Loss of several of these functions explains the pathology of scurvy, where defective collagen synthesis and anemia are major symptoms. Vitamin C deficiency is very common in dialysis patients and may arise from dialytic vitamin C clearance, restricted intake of vitamin C-rich foods, and increased vitamin C catabolism in vivo from inflammation. In the dialysis population, greater vitamin C intake may be needed for optimal health. Relationships between intake, body distribution, inflammation, and dialytic losses are complex and need further study. Concern about vitamin C metabolism leading to accumulation of tissue oxalate has led to the recommendation that vitamin C intake equals, but not exceeds, the intake recommended for the general population. Vitamin C deficiency in dialysis patients may have clinical consequences; a study in Renal Research Institute clinics found an association with periodontal disease. Data also support a role for vitamin C in prevention of dialysis-related anemia. New research questions are proposed in this editorial, with a discussion of strategies to determine the optimal provision of vitamin C for CKD patients.

Effect of short-term intravenous ascorbic acid on reducing ferritin in hemodialysis patients

Resistance to recombinant erythropoietin (rEPO) in hemodialysis patients may be due to inadequate iron recruitment and defect in iron use. In this cross over randomized clinical trial, 30 hemodialysis patients with serum ferritin levels of ≥500 ng/ml, hemoglobin ≤11.0 g/dl, and transferrin saturation (TSAT) of 20% or less were administrated intravenous iron (50-100 mg/wk) and rEPO (120-360 U/kg/wk) for 6 months. Patients were excluded if there was a clear explanation for rEPO hyporesponsiveness. Patients were divided into two groups. Group1 received standard care and 500 mg of intravenous ascorbic acid (IVAA) with each dialysis session in the first week of each month for a total of 3 months. Group 2 received standard care only. After 2 month washout period, groups were crossed over. Each month hemoglobin (Hb) was assessed. Iron, TIBC (transferrin iron binding capacity), TSAT, iPTH (intact parathyroid hormone), liver enzymes, albumin and cholesterol levels were measured every 3 months. After 3 months of intervention, Hb significantly increased from 10.11 to 12.19 g/dl (P <0 0.001; 95% confidence interval [CI] 2.7-1.4) and TSAT increased from 18.9 to 28.1% (P = 0.008; 95% CI 0.09-3), while ferritin and serum iron declined significantly from 1391 to 938 ng/ml (P = 0.001; 95% CI 216-689), 97.2 to 64.6 (P = 0.001; 95% CI 14.8-50.4) in the study group. Change of Hb over time in IVAA group was significant (P < 0.0005). There were significant differences between two groups in change of Hb level over time (P < 0.0005) and treatment effect (P = 0.002). Baseline laboratory tests were similar in the two groups and there was no carry over effect at phase 2. We showed that low amount of IVAA could reduce ferritin level and enhance Hb and TSAT, suggesting improved iron utilization.

The effect of intravenous ascorbic acid in hemodialysis patients with normoferritinemic anemia

Background

Hemodialysis (HD) patients with functional iron deficiency often develop resistance to recombinant human erythropoietin (rhEPO). Recent studies have shown that intravenous ascorbic acid (IVAA) administration could override rhEPO resistance in HD patients. This study was undertaken to test the effects of IVAA in HD patients with normoferritinemic functional iron deficiency accompanied by EPO-hyporesponsive anemia.

Methods

Fifty-eight HD patients with normoferritinemic anemia (between 100 and 500 μg/L) were included and divided into the control (N=25) and IVAA (N=33) groups. IVAA patients received 500 mg of IVAA with each dialysis session for 3 months and an additional 4-month follow-up after the end of the therapy.

Results

Twenty patients had a response to IVAA with a significant increase in hemoglobin level (Hgb>1.0 g/dL) and reduction of weekly rhEPO dosage compared with the control group after 3 months of treatment (P<0.05). Compared with non-responders, transferrin saturation (TSAT) was significantly decreased in the responders group (26±11 vs. 35±14%, P<0.05) on baseline data. There was a significant increase in serum iron and TSAT (baseline vs. 3 months, serum iron 57±22 vs. 108±22 μg/dL, TSAT 26±11 vs. 52±7%, P<0.05) and a decrease in serum ferritin (377±146 vs. 233±145 ng/mL, P<0.05) in the responders group (N=20), but no significant changes in the control and non-responders groups (N=13) at 3-month treatment.

Conclusion

IVAA can be a potent and effective adjuvant therapy for HD patients with rhEPO-resistant normoferritinemic anemia. In addition, IVAA can reduce the dosage of rhEPO for anemia correction.

Oxidative stress and inflammation: Implications in uremia and hemodialysis

Oxidative response and inflammation constitute a major defense against infections, but if not properly regulated they could also lead to a number of deleterious effects. Patients affected by different stages of acute and chronic kidney disease, particularly patients on hemodialysis, present a marked activation of oxidative and inflammatory processes. This condition exposes these patients to an elevated risk of morbidity and mortality. This Review is up to date and it analyses the newest notions about pathophysiological mechanisms of oxidative stress and inflammation in patients with renal diseases, also considering the different strategies studied to counterbalance this high risk state.

Hemoglobin and plasma vitamin C levels in patients on peritoneal dialysis

OBJECTIVE

To determine the contribution of vitamin C (Vit C) status in relation to hemoglobin (Hb) levels in patients on long-term peritoneal dialysis (PD).

METHODS

56 stable PD patients were evaluated in a cross-sectional survey. Plasma samples were collected for Vit C (analyzed by HPLC with electrochemical detection) and high-sensitivity C-reactive protein (hs-CRP) determinations. Clinical records were reviewed for Hb, transferrin saturation (TSAT), ferritin, erythropoietin (EPO) dose, and other clinical parameters. Dietary Vit C intake was evaluated by patient survey and from patient records. Total Vit C removed during PD treatment was measured in 24-hour dialysate collections.

RESULTS

Patients showed a highly skewed distribution of plasma Vit C levels, with 40% of patients below normal plasma Vit C levels (<30 μmol/L) and 9% at higher than normal levels (>80 μmol/L). Higher plasma Vit C levels were associated with higher Hb levels (Pearson r = 0.33, p < 0.004). No direct connection between Vit C levels and reported dietary intake could be established. In stepwise multiple regression, plasma Vit C remained significantly associated with Hb (p = 0.017) but there was no significant association with other variables (dialysis vintage, age, ferritin, TSAT, hs-CRP, residual renal function, and EPO dose). In 9 patients that were evaluated for Vit C in dialysate, plasma Vit C was positively associated (Spearman r = 0.85, p = 0.01) with the amount of Vit C removed during dialysis treatment.

CONCLUSIONS

These data indicate that plasma Vit C is positively associated with higher Hb level. Vit C status could play a major role in helping PD patients to utilize iron for erythropoiesis and achieve a better Hb response during anemia management.

Beneficial hematologic effects of daily oral ascorbic acid therapy in ESRD patients with anemia and abnormal iron homeostasis: a preliminary study

AIM

To determine the efficacy and effects of the oral administration of ascorbic acid on anemia management in ESRD patients with hyperferritinemia.

METHODS

Twenty-one anemic hemodialysis patients with ferritin levels greater than 350 ng/mL had received oral daily ascorbic acid at a dose of 500 mg/day and were retrospectively studied. Hemoglobin, hematocrit, EPO dose, ferritin, and transferrin saturation were recorded at baseline and after three months of treatment. EPO dose/hematocrit was calculated. Serum oxalate levels were also measured.

RESULTS

Hb increased 9% from 11.4 to 12.2 gm/dL (p = 0.05), HCT increased 10% from 33.3 to 36.7% (p = 0.05), but EPO dose requirement decreased 33% from 26,229 to 17,559 U/week (p = 0.03). Ferritin levels decreased 21% from 873 to 691 ng/mL (p = 0.004). Mean oxalate level during therapy was 87 micromol/L (normal <27). Patients with oxalate levels >27 micromol/L were instructed to stop ascorbic acid treatment, and mean levels decreased from 107 to 19 micromol/L (p = 0.01) over a mean time of 71 days.

CONCLUSION

In this study, daily oral ascorbic therapy decreased ferritin levels and EPO dose requirements while raising hemoglobin and hematocrit level. This beneficial profile of effects of ascorbic acid therapy is consistent with improvement of EPO resistance and cost savings in this population.

Parenteral ascorbic acid in haemodialysis patients

PURPOSE OF REVIEW

Parenteral ascorbic acid has been frequently used to overcome problems of vitamin C deficiency in haemodialysis patients. The benefits of vitamin C supplementation in clinical studies have been controversial and did not consider toxicological aspects. The review summarizes recent findings of the effects of parenteral ascorbic acid and discusses toxicological effects.

RECENT FINDINGS

Vitamin C deficiency in haemodialysis patients, which has been frequently described, cannot be improved with oral supplementation due to limited absorption of high dosages. To avoid consequences of vitamin C deficiency, parenteral vitamin C solutions should be administered because this intervention is the only way to guarantee a sufficient supply to the cells. A beneficial consequence of parenteral vitamin C on the recombinant human erythropoietin resistance is an additional therapeutic effect, which contributes to the prevention of iron deficiency anaemia in haemodialysis patients. Thus, large amount of supplemental vitamin C are required for extended periods of time (up to 500 mg 3 times a week). To avoid hyperoxaluria, plasma oxalate levels should be monitored on a regular basis, for example, once a week.

SUMMARY

Parenteral administration of ascorbic acid may be an approach that can overcome problems of vitamin C deficiency in haemodialysis patients - in particular problems of iron overload, erythropoetin resistance, and chronic inflammation.

Anemia of Chronic Kidney Disease

Chronic kidney disease may result in complete kidney failure and contribute to many other health issues. Anemia is a logical consequence of the disease because the kidneys are the primary source of erythropoietin, the hormone that acts to stimulate red blood cell production in the bone marrow. All patients with chronic kidney disease are at risk for anemia, and treating anemia is extremely important to their health and well-being. Preventing or reversing the effects of anemia on the heart may decrease morbidity and mortality and improve quality of life. Many patients fail to receive treatment for anemia before requiring renal replacement therapy for end-stage renal disease. Pharmacists can play a vital role in screening, evaluating, designing proper treatment regimens, and monitoring patients with anemia of chronic kidney disease. Current recommendations regarding anemia are reviewed, including evaluation, pharmacotherapeutic agents, monitoring parameters, and goals of therapy.

Iron and anemia in human biology: a review of mechanisms

The biology of iron in relation to anemia is best understood by a review of the iron cycle, since the majority of iron for erythropoiesis is provided by iron recovered from senescent erythrocytes. In iron-deficiency anemia, storage iron declines until iron delivery to the bone marrow is insufficient for erythropoiesis. This can be monitored with clinical indicators, beginning with low plasma ferritin, followed by decreased plasma iron and transferrin saturation, and culminating in red blood cells with low-Hb content. When adequate dietary iron is provided, these markers show return to normal, indicating a response to the dietary supplement. Anemia of inflammation (also known as anemia of chronic disease, or ACD) follows a different course, because in this form of anemia storage iron is often abundant but not available for erythropoiesis. The diagnosis of ACD is more difficult than the diagnosis of iron-deficiency anemia, and often the first identified symptom is the failure to show a response to a dietary iron supplement. Confirmation of ACD is best obtained from elevated markers of inflammation. The treatment of ACD, which typically employs erythropoietin (EPO) supplements and intravenous iron (i.v.-iron), is empirical and often falls shorts of therapeutic goals. Dialysis patients show a complex pattern of anemia, which results from inadequate EPO production by the kidney, inflammation, changes in nutrition, and blood losses during treatment. EPO and i.v.-iron are the mainstays of treatment. Patients with heart failure can be anemic, with incidence as high as 50%. The causes are multifactorial; inflammation now appears to be the primary cause of this form of anemia, with contributions from increased plasma volume, effects of drug therapy, and other complications of heart disease. Discerning the mechanisms of anemia for the heart failure patient may aid rational therapy in each case.

Newer strategies for anemia prevention in hemodialysis

Anemia prevention for hemodialysis relies primarily on supplemental erythropoietin (EPO) and intravenous iron (IV-iron). The doses of EPO utilized are somewhat higher than normal endogenous rates of EPO production in healthy subjects, and the amount of IV-iron used to boost red blood cell (RBC) production may be greater than the amounts used for erythropoiesis. EPO and IV-iron might be used more efficiently if two fundamental problems were solved in the management of dialysis patients: better vitamin C status, and avoidance of chronic inflammation. The low levels of plasma vitamin C commonly observed in dialysis patients restrict mobilization of stored iron from the reticuloendothelial system (RES), and inflammation has a very similar effect. The impact of low vitamin C levels and concurrent inflammation causes a large amount of iron to be stored, with relatively inefficient utilization for erythropoiesis. Vitamin C intake for dialysis patients is often restricted because of avoidance of vitamin C-rich foods, and because of concerns about oxalosis. Inflammation is a chronic feature of renal disease, which is compounded by infections from use of catheters. Research strategies to improve vitamin C status and to decrease inflammation would lead to better utilization of iron and EPO, and could have parallel benefits for the long-term health of patients on hemodialysis.

Novel aspects of vitamin C in epoetin response

Provision of sufficient available iron is a prerequisite to ensure the bodys optimal response to recombinant human erythropoietin (epoetin). Functional iron deficiency (a state when iron supply is reduced to meet the demands for increased erythropoiesis) is a common cause of poor response to epoetin in dialysis patients who have normal iron status, even when they are iron-overloaded. Iron supplementation is not justified for this hyporesponsiveness in patients with iron overload due to the potential hazards of iron overload aggravated by intravenous iron therapy. Furthermore, in vivo studies have indicated that the promising effect of intravenous iron medication to overcome iron-deficient erythropoiesis is not observed in iron-overloaded hemodialysis (HD) patients. Vitamin C, a water-soluble antioxidant as well as a reducing agent, has a number of associations with iron metabolism. Recent research highlights that vitamin C can potentiate the mobilization of iron from inert tissue stores and facilitates the incorporation of iron into protoporphyrin in HD patients being treated with epoetin. Interest has turned towards the use of vitamin C as an adjuvant therapy in this field. This review focuses on the improvement of epoetin response by administration of vitamin C and discusses its clinical implications and potential issues for internal medicine doctors.

Iron therapy for renal anemia: how much needed, how much harmful?

Iron deficiency is the most common cause of hyporesponsiveness to erythropoiesis-stimulating agents (ESAs) in end-stage renal disease (ESRD) patients. Iron deficiency can easily be corrected by intravenous iron administration, which is more effective than oral iron supplementation, at least in adult patients with chronic kidney disease (CKD). Iron status can be monitored by different parameters such as ferritin, transferrin saturation, percentage of hypochromic red blood cells, and/or the reticulocyte hemoglobin content, but an increased erythropoietic response to iron supplementation is the most widely accepted reference standard of iron-deficient erythropoiesis. Parenteral iron therapy is not without acute and chronic adverse events. While provocative animal and in vitro studies suggest induction of inflammation, oxidative stress, and kidney damage by available parenteral iron preparations, several recent clinical studies showed the opposite effects as long as intravenous iron was adequately dosed. Thus, within the recommended international guidelines, parenteral iron administration is safe. Intravenous iron therapy should be withheld during acute infection but not during inflammation. The integration of ESA and intravenous iron therapy into anemia management allowed attainment of target hemoglobin values in the majority of pediatric and adult CKD and ESRD patients.

Vitamin C neglect in hemodialysis: sailing between Scylla and Charybdis

In our efforts to meet the vitamin C requirements of dialysis patients we confront a medical dilemma--do we allow the patient to become depleted of vitamin C, with the accompanying hematological and other consequences (Scylla), or do we provide for adequate tissue levels of vitamin C, which has been thought to carry the risk of oxalosis (Charybdis). Many practitioners are certain that either one outcome (deficiency) or the other (oxalic acid toxicity) is inevitable, and much like Odysseus, no safe course is to be found. The recent accumulating evidence that vitamin C improves the management of anemia in dialysis patients compels us to find a safe passage through this dilemma. The serious vitamin C deficiency seen in many patients may also contribute to poor oral health and chronic fatigue. The evidence for oxalosis from vitamin C supplements stems from hemodialysis as practiced 20 years ago. Investigators using this therapy are not observing systemic oxalosis, and the most current data support the conclusion that vitamin C therapy is safe for dialysis patients. The question will be resolved by controlled trials that address both vitamin C effectiveness and safety.

The oxalate level in ultrafiltrate fluid collected from a dialyzer is useful for estimating the plasma oxalate level in hemodialysis patients

BACKGROUND

Patients on chronic hemodialysis are likely to develop secondary hyperoxalemia. It is, however, difficult to measure plasma oxalate levels. To measure plasma oxalate levels, rapid plasma separation, deproteinization, and acidification are essential in preventing the formation of oxalate and the deposition of calcium oxalate within the test tube. The present study was undertaken to examine whether the oxalate level in dialyzer ultrafiltrate is potentially useful for estimating plasma oxalate levels.

METHODS

In nine patients on chronic hemodialysis, the plasma, after deproteinization with a filter, and the ultrafiltrate from the dialyzer before hemodialysis were acidified to a pH level of less than 3, followed by the measurement of oxalate levels by ion chromatography. Also, oxalate levels were compared between acidified and non-acidified ultrafiltrates from the dialyzer. In the second part of the study, seven patients on chronic hemodialysis receiving erythropoietin therapy, in whom the ferritin level was more than 300 ng/ml and transferrin saturation was less than 25%, were intravenously administered ascorbic acid, 100 mg, three times a week, after each dialysis session to facilitate the utilization of stored iron. This treatment was continued until the serum ferritin level decreased to a level below 300 ng/ml (for 3 months, at a maximum). The oxalate level in the dialyzer ultrafiltrate after this treatment was compared with that before treatment.

RESULTS

The mean +/- SE oxalate level in the dialyzer ultrafiltrate was 45 +/- 6 micromol/l, essentially equal to the plasma oxalate level (46 +/- 7 micromol/l). The plasma oxalate level had a significant positive correlation with the dialyzer ultrafiltrate oxalate level (plasma oxalate level = 0.99 x dialyzer ultrafiltrate oxalate level + 1.5; r = 0.95; P < 0.0001). The oxalate level in the acidified ultrafiltrate (45 +/- 6 micromol/l) did not differ significantly from that in the non-acidified ultrafiltrate (45 +/- 6 micromol/l). The mean +/- SE duration of ascorbic acid administration was 64 +/- 13 days. The hemoglobin level remained unchanged at 9.6 +/- 0.4 g/dl, whereas the serum iron level increased significantly, from 34 +/- 2 microg/dl to 43 +/- 4 microg/dl (P < 0.05), and serum ferritin levels decreased significantly, from 645 +/- 219 ng/ml to 231 +/- 30 ng/ml after the treatment (P < 0.05). The oxalate level in the acidified ultrafiltrate showed no significant change after ascorbic acid administration (31 +/- 8 micromol/l vs 47 +/- 7 micromol/l).

CONCLUSIONS

In patients on chronic hemodialysis, the oxalate level in acidified ultrafiltrate from the dialyzer was found to be useful for estimating the plasma level of non-protein-bound oxalate. When administering ascorbic acid to hemodialysis patients, the plasma oxalate level can be monitored using this method.

Normoxic stabilization of hypoxia-inducible factor-1alpha by modulation of the labile iron pool in differentiating U937 macrophages: effect of natural resistance-associated macrophage protein 1

Hypoxia-inducible factor (HIF) is a transcription factor with major roles in many cellular and systemic responses to hypoxia. Activation of HIF pathways under hypoxia is mediated by suppression of the Fe(2+)- and O(2)-dependent HIF hydroxylase enzymes that normally inactivate HIFalpha subunits. Mechanisms underlying induction of HIF in normoxic conditions are less clearly understood. In human cancers, infiltrating macrophages show up-regulation of HIF and it has recently been shown that normoxic expression of HIF-1alpha is essential for macrophage function. Here, we report studies of HIF-1alpha induction following phorbol-12-myristate 13-acetate (PMA)-induced differentiation of monocytic U937 and THP1 cells. HIF-1alpha was markedly up-regulated under normoxia in this setting and this involved failure of HIF-1alpha prolyl hydroxylation despite the presence of O(2). Fluorescence measurements showed that differentiation was associated with marked reduction of the labile iron pool. Both the reduction in labile iron pool and the up-regulation of HIF-1alpha were suppressed by RNA interference-mediated down-regulation of the iron transporter natural resistance-associated macrophage protein 1. Up-regulation of HIF-1alpha following PMA-induced differentiation was also abolished by addition of Fe(2+) or ascorbate. These results indicate that physiologic changes in macrophage iron metabolism have an important effect on HIF hydroxylase pathways and suggest means by which the system could be manipulated for therapeutic benefit.

Effect of Intravenous Ascorbic Acid in Hemodialysis Patients With EPO-Hyporesponsive Anemia and Hyperferritinemia

BACKGROUND

Although erythropoietin (EPO)-hyporesponsive anemia in hemodialysis patients most commonly results from iron deficiency, the contributory role of chronic inflammation and oxidative stress in its pathogenesis is poorly understood. We conducted an open-label prospective study to assess the effect of vitamin C, an antioxidant, on EPO-hyporesponsive anemia in hemodialysis patients with unexplained hyperferritinemia.

METHODS

Forty-six of 262 patients in an inner-city hemodialysis center met the inclusion criteria (administration of intravenous iron and EPO for > or = 6 months at a dose > or = 450 U/kg/wk, average 3-month hemoglobin [Hb] level < or = 11.0 g/dL [< or = 110 g/L], ferritin level > or = 500 ng/mL (microg/L), and transferrin saturation [TSAT] < or = 50%). Patients were excluded if they had a clear explanation for the EPO hyporesponsiveness. Four patients refused to participate. The remaining patients were randomly assigned; 20 patients to receive standard care and 300 mg of intravenous vitamin C with each dialysis session (group 1) and 22 patients to receive standard care only (group 2). Study duration was 6 months. During the study, 1 patient from group 1 was removed (upper gastrointestinal bleeding) from final analysis. Monthly assessment included Hb level, mean corpuscular volume, iron level, iron-binding capacity, ferritin level, TSAT, and Hb content in reticulocytes. In addition, biointact parathyroid hormone, aluminum, C-reactive protein (CRP), and liver enzymes were measured every 3 months.

RESULTS

Age, sex, race, and time on dialysis therapy were similar in both groups. At 6 months, Hb levels significantly increased from 9.3 to 10.5 g/dL (93.0 to 105.0 g/L) in group 1, but not group 2 (9.3 to 9.6 g/dL [93.0 to 96.0 g/L]; P = 0.0001). Similarly, TSAT increased from 28.9% to 37.3% in group 1, but not group 2 (28.7% to 29.3%; P = 0.0001). EPO dose (477 to 429 versus 474 to 447 U/kg/wk), iron-binding capacity (216 to 194 versus 218 to 257 microg/dL [38.7 to 34.7 versus 39 to 46 micromol/L]), and CRP level (2.8 to 0.9 versus 2.8 to 2.2 mg/dL) decreased significantly in group 1, but not in controls. Changes in Hb content in reticulocytes and ferritin level also were statistically significant in group 1. There was no change in biointact parathyroid hormone levels. Although serum iron levels and intravenous iron doses changed within each group, changes were equal between the 2 groups.

CONCLUSION

In hemodialysis patients with refractory anemia and hyperferritinemia, vitamin C improved responsiveness to EPO, either by augmenting iron mobilization from its tissue stores or through antioxidant effects.

Melatonin corrects reticuloendothelial blockade and iron status in haemodialysed patients

AIM

Treatment of anaemia in haemodialysed patients in the setting of inflammation usually displays high levels of serum ferritin (>800 ng/mL) and low transferrin saturation (TSAT) (<20%) despite i.v. iron supplementation, thus proving iron trapping in the reticuloendothelial system. Melatonin has been reported to reduce cytokine production and, in dialysis patients, to prevent oxidative stress resulting from iron and erythropoietin treatment.

METHOD

In this study, we evaluated a group of 10 patients undergoing haemodialysis who displayed elevated serum ferritin (981 +/- 44.6 ng/mL) and TSAT <20% (15.6 +/- 3.8%) after having received 1.2 g of i.v. iron dextran over a period of 8 weeks. These patients received oral melatonin, 6 mg/day at night for 30 days.

RESULTS

After this treatment, all of them markedly increased TSAT values, reaching 35.5 +/- 6.7% (P < 0.0001 vs basal values). In addition, ferritin values decreased to 754.4 +/- 263.7 ng/mL (P < 0.05), and serum iron dramatically increased in all of the patients under study (42.4 +/- 9.4 vs 109.7 +/- 24.3 microg/dL; P < 0.0001). Values for haematocrit (28.6 +/- 2.7 vs 31.9 +/- 3.57%; P < 0.05) and haemoglobin (9.19 +/- 0.97 vs 10.04 +/- 1.29 g/dL; P < 0.05) were also improved. Measurements were then repeated 2 weeks after melatonin withdrawal, showing an impressive decrease in TSAT (16.4 +/- 5.3%; P < 0.00001) and serum iron (48 +/- 14.7 microg/dL; P < 0.0001) values and an almost significant increase in ferritin values (954.4 +/- 86 ng/mL; P < 0.054).

CONCLUSION

The present study demonstrates that melatonin may strongly correct the reticuloendothelial blockade seen in dialysis patients under an inflammatory status, thus allowing a better management of iron derangements and renal anaemia.

Effects of oral vitamin C supplementation in hemodialysis patients: A proteomic assessment

Evidence indicates that oxidative stress is present in dialysis patients, and is associated with vitamin C deficiency. Limited data are available regarding the effects of vitamin C supplementation on oxidative stress and inflammation markers in these patients. Moreover, there are no data available on plasma polypeptide fingerprints by proteome analysis before and after vitamin C supplementation. Therefore, we analyzed plasma samples from a prospective, randomized, open-labeled trial to assess the effects of oral vitamin C supplementation (250 mg three times per week), to define the plasma polypeptide pattern in hemodialysis patients. Our results reveal that more than 30 polypeptides show significant changes in the dialysis patients in comparison to controls with normal renal function, and that several polypeptides are affected/normalized by oral vitamin C supplementation. These results underline the remarkable potential for proteomics to recognize specific peptide profiles in different pathological situations, which might not be detected by classical methods.

Correction of copper deficiency improves erythropoietin unresponsiveness in hemodialysis patients with anemia

We have encountered five hemodialysis patients who had received enteral nutrition and recovered from erythropoietin-resistant anemia with neutropenia after the correction of copper deficiency. We reduced the required doses of recombinant human erythropoietin (rHuEPO) to maintain the target hematocrit levels and three patients were finally weaned from the rHuEPO therapy. Thus, copper deficiency is involved in erythropoietin-resistant anemia in hemodialysis patients.

Long-term, low-dose, intravenous vitamin C leads to plasma calcium oxalate supersaturation in hemodialysis patients

BACKGROUND

Ascorbate supplementation for patients on regular dialysis treatment (RDT) is advised to obviate deficiency and improve epoetin response in those with functional iron deficiency. However, clear-cut safety concerns regarding hyperoxalemia are still poorly understood. This study tries to establish safety/efficacy profiles of ascorbate and oxalate during long-term intravenous ascorbate supplementation.

METHODS

A prospective study was performed in 30 patients on RDT showing ascorbate deficiency (plasma ascorbate < 2.6 mg/L [<15 micromol/L]): 18 patients were administered intravenous ascorbate during 18 months (250 mg/wk, subsequently increased to 500 mg), and 12 patients were taken as reference untreated cases. Plasma ascorbate and oxalate assays and dialytic balance determinations were performed (ion chromatography and reverse-phase high-performance liquid chromatography, respectively) at baseline, during treatment, and 12 months after withdrawal.

RESULTS

Plasma ascorbate levels increased dose dependently with supplementation (1.6 +/- 0.8 mg/L [9.1 +/- 4.6 mumol/L] at baseline, 2.8 +/- 1.8 mg/L [15.9 +/- 10.1 micromol/L]) with 250 mg of ascorbate, and 6.6 +/- 2.8 mg/L [37.5 +/- 16.0 micromol/L] with 500 mg/wk of ascorbate), but only normalized with greater dosages for several months in 94% of patients. Baseline plasma oxalate levels increased from 3.2 +/- 0.8 mg/L (35.8 +/- 8.8 micromol/L) to 3.6 +/- 0.8 mg/L (39.5 +/- 9.1 micromol/L) and 4.5 +/- 0.9 mg/L (50.3 +/- 10.4 micromol/L) with 250 and 500 mg, respectively ( P < 0.001). The calcium oxalate saturation threshold was exceeded by 7 of 18 patients (40%) during 6 months therapy with 500 mg/wk. Ascorbate dialysis removal increased from 37.8 +/- 23.2 mg (215 +/- 132 micromol) to 99.6 +/- 51.7 mg (566 +/- 294 micromol) during supplementation (P < 0.001), with corresponding increases in oxalate removal from 82.5 +/- 33.2 mg (917 +/- 369 micromol) to 111.2 +/- 32.6 mg/L (1,236 +/- 362 micromol; P < 0.01). Withdrawal reverted plasma levels and dialysis removal to initial values. Values for untreated patients did not change during 1 year of follow-up.

CONCLUSION

Patients on RDT may resolve ascorbate deficiency with intravenous supplementation of 500 mg/wk, but this implies a significant risk for oxalate supersaturation. Oxalate measurements are strongly recommended during long-term ascorbate therapy.

Serum non-transferrin bound iron in hemodialysis patients not receiving intravenous iron

BACKGROUND

Non-transferrin bound iron (NTBI) has been found to be raised in end stage renal disease (ESRD) patients on hemodialysis (HD) receiving intravenous (IV) iron. Such NTBI is proposed to cause oxidative damage to biomolecules.

METHOD

NTBI, both ferrous (Fe(+2)) and ferric (Fe(+3)) forms, serum ferritin, protein thiols and lipid hydroperoxides were estimated by spectrophotometric and electrochemiluminescence immunoassay methods in patients with chronic renal failure (CRF), patients with ESRD on HD not receiving IV iron, and in normal controls.

RESULTS

NTBI (Fe(+2)) in HD patients not receiving IV iron was higher than in normal controls. NTBI (Fe(+3)) was significantly higher in HD patients not on IV iron therapy than in CRF and normal controls. There was no significant increase in NTBI in CRF patients when compared to normal controls. Serum ferritin was higher in HD patients compared to CRF and normal controls. There was a significant increase in lipid hydroperoxides and protein thiols in HD patients and CRF patients when compared to normal controls. The NTBI did not correlate with serum ferritin and oxidative markers.

CONCLUSION

The source of NTBI in hemodialysis is not only IV iron therapy but also the hemodialysis procedure per se. It may be due to microhemolysis during hemodialysis. The NTBI is however found to be catalytically inactive.

Efficacy and safety of oral versus intravenous ascorbic acid for anaemia in haemodialysis patients

BACKGROUND

Intravenous (i.v.) ascorbic acid (AA) improves anaemia in iron-overloaded, erythropoietin (rEPO) hyporesponsive haemodialysis patients. While oral AA is readily attainable, the efficacy and safety of oral versus i.v. AA has not been examined.

METHODS

We conducted an open-label randomised parallel study on the effects of 8 weeks of 250 mg oral AA (n=10) compared with 250 mg i.v. AA (n=11) 3x/week on haemoglobin (Hb), ferritin and rEPO dose in 21 iron-overloaded haemodialysis patients. We also examined the effect of 3 months of 500 mg oral AA 3x/week (n=70) compared with no treatment (n=83) on Hb, ferritin and rEPO dose in 153 haemodialysis patients.

RESULTS

Patients had severe AA deficiency (mean 2.2+/-SE 0.4 mg/L; normal range, 4.0-14.0). Following treatment, the plasma AA level increased (P<0.001), but was not significantly different between the groups. There was no change in Hb, iron availability and rEPO dose with oral or i.v. AA. There was a significant increase in serum oxalate but no significant changes in left ventricular function or renal calculi formation. In the second study, oral AA had no effect on Hb, rEPO dose and ferritin in the whole group and a subgroup of 30 with anaemia.

CONCLUSION

Haemoglobin and iron availability did not improve following oral or i.v. AA in this select small group of iron-overloaded haemodialysis patients or in a larger population of haemodialysis patients given oral AA at a higher dose and for a longer duration. AA supplementation may still be warranted in view of severe AA deficiency in haemodialysis patients.

Effects of oral vitamin C supplementation on oxidative stress and inflammation status in haemodialysis patients

BACKGROUND

There is increasing evidence for the presence of oxidative stress and vitamin C deficiency in dialysis patients. Limited data, however, are available regarding the effects of vitamin C supplementation on oxidative stress and inflammation markers in such patients.

METHODS

We ran a prospective, randomized, open-label trial to assess the effects of oral vitamin C supplementation (250 mg three times per week) for 2 months on well-defined oxidative and inflammatory markers in 33 chronic haemodialysis (HD) patients.

RESULTS

Normalization of plasma total vitamin C and ascorbate levels by oral vitamin C supplementation did not modify plasma levels of carbonyls, C-reactive protein and albumin, or erythrocyte concentrations of reduced and oxidized glutathione.

CONCLUSION

Short-term oral vitamin C supplementation did not modify well-defined oxidative/antioxidative stress and inflammation markers in HD patients. Whether a higher oral dose or the intravenous route can modify these markers remains to be determined.

Emerging drugs for renal failure

Renal failure involves a significant impairment of the essential functions of the kidney, which can be either acute with sudden and rapid onset (acute renal failure [ARF]) or chronic with gradual onset (chronic renal failure [CRF]). ARF, if detected early, may be halted or reversed, whereas CRF is generally irreversible. Without treatment or intervention, both forms of renal failure lead to end stage renal failure (ESRF) or end stage renal disease (ESRD), requiring renal replacement therapy (RRT) in the form of dialysis or renal transplantation for survival. However, provision of RRT requires expert teams working in specialised units, making therapy of patients with renal failure expensive; furthermore, RRT is complex, with its own complications. Although pharmacological interventions have shown promise in experimental models, these have not been as successful in the clinical setting (e.g., administration of atrial natriuretic peptide, low-dose dopamine). At present, drugs are administered during CRF to either reduce one of the many risk factors of CRF (e.g., angiotensin-converting enzyme inhibitors, statins) or to deal with the consequences of CRF (e.g., erythropoietin, calcitriol). Recent evidence suggests that some of these interventions may provide further direct beneficial effects via reduction of renal inflammation. Although these interventions have greatly improved the prospects for patients suffering ESRF, the development of novel drugs and therapies with which to reduce the consequences of renal failure and ESRD remain topics of great interest. This article reviews the therapies available for the prevention and management of renal failure in adults and describes, in detail, emerging drugs and novel interventions that may soon become available for the treatment or prevention of ESRF.

Editorials: L-Carnitine Supplementation in Dialysis Patients: Does the Evidence Justify Its Use?

Beginning January 1, 2003, the Centers for Medicare and Medicaid Services (CMS) initiated a national coverage determination for the use of levo-carnitine (L-carnitine) in end-stage renal disease (ESRD) patients as a supplement for individuals defined as having a carnitine deficiency, accompanied by either erythropoietin (EPO)-resistant anemia and/or symptomatic intradialytic hypotension. The CMS criteria established for use of this supplement is minimal because EPO-resistant anemia and symptomatic intradialytic hypotension are never defined with any degree of scientific rigor. Even with the minimal criteria, CMS rejected 97% of the claims submitted over the first 6 months of the national coverage. Most importantly, scientific studies to justify use of the supplement do not exist. Based on limited scientific investigations, there appears to be no justification for the government paying for this supplement. A randomized, prospective, controlled study is needed to determine if there is any benefit from L-carnitine supplementation. Pending appropriate scientific proof, I do not believe that we should continue to waste our limited ESRD resources on a treatment of unproven benefit.

Pharmacologic adjuvants to epoetin in the treatment of anemia in patients on hemodialysis

Anemia is a common complication of chronic kidney disease, particularly in patients who are on dialysis. The use of recombinant human erythropoietin has led to the eradication of severe anemia in the dialysis population. Correction of anemia in these patients has been associated with better quality of life and clinical outcomes. Some hemodialysis patients have anemia that either is relatively refractory to epoetin therapy or requires very high doses of epoetin (i.e., hyporesponsiveness), despite having adequate iron stores, and are thus unable to achieve or maintain target hemoglobin levels. Several pharmacologic agents have been studied for effects on improving response to epoetin, either to counter hyporesponsiveness or simply to reduce epoetin use for purely economic reasons. This review examines the available literature regarding the efficacy of these potential pharmacologic adjuvants to epoetin in the treatment of anemia in patients on maintenance hemodialysis, with special emphasis on androgens, vitamin C (ascorbic acid), and L-carnitine. A review of published guidelines and recommendations for use of these agents in hemodialysis patients is provided.

Vitamin C plasma level and response to erythropoietin in patients on maintenance haemodialysis

BACKGROUND

Intravenous vitamin C supplementation to haemodialysis patients might ameliorate responsiveness to recombinant human erythropoietin (rHuEpo). This study was performed to analyse the relation between vitamin C plasma concentration and response to rHuEpo.

METHODS

In a cross-sectional, single-centre observational study including all haemodialysis patients, pre-dialysis plasma vitamin C concentrations were measured by high-performance liquid chromatography and response to rHuEpo (haemoglobin concentration/international units rHuEpo/kg/week) was recorded together with baseline laboratory data.

RESULTS

Univariate analysis yielded a significant correlation between vitamin C plasma levels and response to rHuEpo (n = 130, r = 0.25, P = 0.004), which still persisted after adjustment for transferrin saturation, C-reactive protein, malondialdehyde, parathyroid hormone, route of rHuEpo administration, residual renal function and diabetes mellitus (adjusted r = 0.23, P = 0.014). Analysis per quartiles of vitamin C plasma level revealed a significantly lower response to rHuEpo with decreasing vitamin C values (P = 0.026).

CONCLUSIONS

In unselected haemodialysis patients, vitamin C plasma levels account, at least partially, for the response to rHuEpo. Larger-sized interventional studies are needed to find out whether vitamin C plasma levels may or may not appropriately reflect the potential beneficial effect of vitamin C supplements on rHuEpo responsiveness.