Gastrointestinal blood loss in patients with chronic renal failure

Ferric pyrophosphate citrate for parenteral administration of maintenance iron: structure, mechanism of action, clinical efficacy and safety

Anemia is a common complication in patients with hemodialysis-dependent chronic kidney disease (HDD-CKD). Anemia is principally the result of erythropoietin deficiency, inflammation, and iron deficiency. High molecular weight iron oxide nanoparticles (IONP) are routinely administered intravenously to replace iron losses and, although effective, there are lingering concerns about possible safety issues. Ferric pyrophosphate citrate (FPC, Triferic, Triferic AVNU [Triferic and Triferic AVNU are the proprietary name for ferric pyrophosphate citrate. Triferic and Triferic AVNU are registered trademarks of Rockwell medical Inc.]) is a complex iron salt that donates iron directly to plasma transferrin. FPC is devoid of any carbohydrate moiety and is administered via the dialysate or intravenously during each hemodialysis session to replace iron and maintain hemoglobin. Controlled clinical trials of up to 48 weeks in duration have demonstrated the efficacy of regular administration of dialysate FPC for maintaining hemoglobin levels and iron balance in HDD-CKD patients. Clinical data also suggest that dialysate FPC may reduce the dose requirements for and use of erythropoiesis-stimulating agents and IONPs in HDD-CKD patients. Safety data from clinical studies and post-marketing surveillance show that FPC is well tolerated and not associated with an increased risk of infection, inflammation, iron overload, or serious hypersensitivity reactions. FPC represents an effective and well-tolerated choice for iron replacement and maintenance of hemoglobin in the long-term management of HDD-CKD patients.

Erythropoiesis-independent effects of iron in chronic kidney disease

Chronic kidney disease (CKD) leads to alterations of iron metabolism, which contribute to the development of anemia and necessitates iron supplementation in patients with CKD. Elevated hepcidin accounts for a significant iron redistribution in CKD. Recent data indicate that these alterations in iron homeostasis coupled with therapeutic iron supplementation have pleiotropic effects on many organ systems in patients with CKD, far beyond the traditional hematologic effects of iron; these include effects of iron on inflammation, oxidative stress, kidney fibrosis, cardiovascular disease, CKD-mineral and bone disorder, and skeletal growth in children. The effects of iron supplementation appear to be largely dependent on the route of administration and on the specific iron preparation. Iron-based phosphate binders exemplify the opportunity for using iron for both traditional (anemia) and novel (hyperphosphatemia) indications. Further optimization of iron therapy in patients with CKD may inform new approaches to the treatment of CKD complications and potentially allow modification of disease progression.

Risk of iron overload with chronic indiscriminate use of intravenous iron products in ESRD and IBD populations

The routine use of recombinant erythropoiesis-stimulating agents (ESA) over the past three decades has enabled the partial correction of anaemia in most patients with end-stage renal disease (ESRD). Since ESA use frequently leads to iron deficiency, almost all ESA-treated haemodialysis patients worldwide receive intravenous iron (IV) to ensure sufficient available iron during ESA therapy. Patients with inflammatory bowel disease (IBD) are also often treated with IV iron preparations, as anaemia is common in IBD. Over the past few years, liver magnetic resonance imaging (MRI) has become the gold standard method for non-invasive diagnosis and follow-up of iron overload diseases. Studies using MRI to quantify liver iron concentration in ESRD have shown a link between high infused iron dose and risk of haemosiderosis in dialysis patients. In September 2017, the Pharmacovigilance Committee (PRAC) of the European Medicines Agency (EMA) considered convergent publications over the last few years on iatrogenic haemosiderosis in dialysis patients and requested that companies holding marketing authorization for iron products should investigate the risk of iron overload, particularly in patients with end-stage renal disease on dialysis and, by analogy, patients with IBD. We present a narrative review of data supporting the views and decision of the EMA, and then give our expert opinion on this controversial field of anaemia therapeutics.

Long-Term Risks of Intravenous Iron in End-Stage Renal Disease Patients

Patients with end-stage renal disease on dialysis commonly receive intravenous iron to treat anemia along with erythropoiesis-stimulating agents. While studies of intravenous iron have demonstrated efficacy in raising hemoglobin, the quantity of administered intravenous iron has raised concerns about iron overload leading to long-term toxicities. The goal of this review is to understand recent trends in intravenous iron use, potential mechanisms of iron toxicity, and to evaluate the available evidence in the literature for potential long-term cardiovascular and infectious complications. We include findings from the recently published landmark clinical trial of intravenous iron for patients receiving hemodialysis to contextualize treatment recommendations.

Diagnostic and therapeutic considerations for obscure gastrointestinal bleeding in patients with chronic kidney disease

Recurrent obscure gastrointestinal bleeding amongst patients with chronic kidney disease is a challenging problem gastroenterologists are facing and is associated with an extensive diagnostic workup, limited therapeutic options, and high healthcare costs. Small-bowel angiodysplasia is the most common etiology of obscure and recurrent gastrointestinal bleeding in the general population. Chronic kidney disease is associated with a higher risk of gastrointestinal bleeding and of developing angiodysplasia compared with the general population. As a result, recurrent bleeding in this subgroup of patients is more prevalent and is associated with an increased number of endoscopic and radiographic procedures with uncertain benefit. Alternative medical therapies can reduce re-bleeding; however, more studies are needed to confirm their efficacy in this subgroup of patients.

Whole-body iron transport and metabolism: Mechanistic, multi-scale model to improve treatment of anemia in chronic kidney disease

Iron plays vital roles in the human body including enzymatic processes, oxygen-transport via hemoglobin and immune response. Iron metabolism is characterized by ~95% recycling and minor replenishment through diet. Anemia of chronic kidney disease (CKD) is characterized by a lack of synthesis of erythropoietin leading to reduced red blood cell (RBC) formation and aberrant iron recycling. Treatment of CKD anemia aims to normalize RBC count and serum hemoglobin. Clinically, the various fluxes of iron transport and accumulation are not measured so that changes during disease (e.g., CKD) and treatment are unknown. Unwanted iron accumulation in patients is known to lead to adverse effects. Current whole-body models lack the mechanistic details of iron transport related to RBC maturation, transferrin (Tf and TfR) dynamics and assume passive iron efflux from macrophages. Hence, they are not predictive of whole-body iron dynamics and cannot be used to design individualized patient treatment. For prediction, we developed a mechanistic, multi-scale computational model of whole-body iron metabolism incorporating four compartments containing major pools of iron and RBC generation process. The model accounts for multiple forms of iron in vivo, mechanisms involved in iron uptake and release and their regulation. Furthermore, the model is interfaced with drug pharmacokinetics to allow simulation of treatment dynamics. We calibrated our model with experimental and clinical data from peer-reviewed literature to reliably simulate CKD anemia and the effects of current treatment involving combination of epoietin-alpha and iron dextran. This in silico whole-body model of iron metabolism predicts that a year of treatment can potentially lead to 90% downregulation of ferroportin (FPN) levels, 15-fold increase in iron stores with only a 20% increase in iron flux from the reticulo-endothelial system (RES). Model simulations quantified unmeasured iron fluxes, previously unknown effects of treatment on FPN-level and iron stores in the RES. This mechanistic whole-body model can be the basis for future studies that incorporate iron metabolism together with related clinical experiments. Such an approach could pave the way for development of effective personalized treatment of CKD anemia.

Positive Iron Balance in Chronic Kidney Disease: How Much is Too Much and How to Tell?

BACKGROUND

Regulation of body iron occurs at cellular, tissue, and systemic levels. In healthy individuals, iron absorption and losses are minimal, creating a virtually closed system. In the setting of chronic kidney disease and hemodialysis (HD), increased iron losses, reduced iron absorption, and limited iron availability lead to iron deficiency. Intravenous (IV) iron therapy is frequently prescribed to replace lost iron, but determining an individual's iron balance and stores can be challenging and imprecise, contributing to uncertainty about the long-term safety of IV iron therapy.

SUMMARY

Patients on HD receiving judicious doses of IV iron are likely to be in a state of positive iron balance, yet this does not appear to confer an overt risk for clinically relevant iron toxicity. The concomitant use of iron with erythropoiesis-stimulating agents, the use of maintenance iron dosing regimens, and the reticuloendothelial distribution of hepatic iron deposition likely minimize the potential for iron toxicity in patients on HD. Key Messages: Because no single diagnostic test can, at present, accurately assess iron status and risk for toxicity, clinicians need to take an integrative approach to avoid iron doses that impose excessive exposure while ensuring sufficient replenishment of iron stores capable of overcoming hepcidin blockade and allowing for effective erythropoiesis.

Iatrogenic iron overload and its potential consequences in patients on hemodialysis

Iron overload was considered rare in hemodialysis patients until recently, but its clinical frequency is now increasingly recognized. The liver is the main site of iron storage and the liver iron concentration (LIC) is closely correlated with total iron stores in patients with secondary hemosiderosis and genetic hemochromatosis. Magnetic resonance imaging (MRI) is now the gold standard method for estimating and monitoring LIC. Studies of LIC in hemodialysis patients by magnetic susceptometry thirteen years ago and recently by quantitative MRI have demonstrated a relation between the risk of iron overload and the use of intravenous (IV) iron products prescribed at doses determined by the iron biomarker cutoffs contained in current anemia management guidelines. These findings have challenged the validity of both iron biomarker cutoffs and current clinical guidelines, especially with respect to recommended IV iron doses. Moreover, three recent long-term observational studies suggested that excessive IV iron doses might be associated with an increased risk of cardiovascular events and death in hemodialysis patients. It has been hypothesized that iatrogenic iron overload in the era of erythropoiesis-stimulating agents might silently increase complications in dialysis patients without creating obvious, clinical signs and symptoms. High hepcidin-25 levels were recently linked to fatal and nonfatal cardiovascular events in dialysis patients. It has been postulated that the main pathophysiological pathway leading to these events might involve the pleiotropic master hormone hepcidin, which regulates iron metabolism, leading to activation of macrophages in atherosclerotic plaques and then to clinical cardiovascular events. Thus, the potential iron overload toxicity linked to chronic administration of IV iron therapy is now becoming one of the most controversial topics in the management of anemia in hemodialysis patients.

Iatrogenic Iron Overload in Dialysis Patients at the Beginning of the 21st Century

Iron overload used to be considered rare in hemodialysis patients but its clinical frequency is now increasingly realized. The liver is the main site of iron storage and the liver iron concentration (LIC) is closely correlated with total iron stores in patients with secondary hemosideroses and genetic hemochromatosis. Magnetic resonance imaging is now the gold standard method for LIC estimation and monitoring in non-renal patients. Studies of LIC in hemodialysis patients by quantitative magnetic resonance imaging and magnetic susceptometry have demonstrated a strong relation between the risk of iron overload and the use of intravenous (IV) iron products prescribed at doses determined by the iron biomarker cutoffs contained in current anemia management guidelines. These findings have challenged the validity of both iron biomarker cutoffs and current clinical guidelines, especially with respect to recommended IV iron doses. Three long-term observational studies have recently suggested that excessive IV iron doses may be associated with an increased risk of cardiovascular events and death in hemodialysis patients. We postulate that iatrogenic iron overload in the era of erythropoiesis-stimulating agents may silently increase complications in dialysis patients without creating frank clinical signs and symptoms. High hepcidin-25 levels were recently linked to fatal and nonfatal cardiovascular events in dialysis patients. It is therefore tempting to postulate that the main pathophysiological pathway leading to these events may involve the pleiotropic master hormone hepcidin (synergized by fibroblast growth factor 23), which regulates iron metabolism. Oxidative stress as a result of IV iron infusions and iron overload, by releasing labile non-transferrin-bound iron, might represent a ‘second hit’ on the vascular bed. Finally, iron deposition in the myocardium of patients with severe iron overload might also play a role in the pathogenesis of sudden death in some patients.

[Use of intravenous iron supplementation in chronic kidney disease: Interests, limits, and recommendations for a better practice]

Iron deficiency is an important clinical concern in chronic kidney disease (CKD), giving rise to iron-deficiency anaemia, and various impaired cellular functions. Oral supplementation, in particular with ferrous salts, is associated with a high rate of gastro-intestinal side effects and is poorly absorbed, a problem that is avoided with intravenous (IV) irons. Recently, with the approval of the European Medicines Agency's Committee for Medicinal Products for Human Use, the French Agence nationale de sécurité du médicament et des produits de santé (ANSM) took adequate measures to minimize the risk of allergic reactions, by correction on the summary of intravenous iron products characteristics. All IV iron products should be prescribed, administered and injected, inside public or private hospitals exclusively, and a clinical follow-up after the infusion for at least 30 minutes is mandatory. The most stable intravenous iron complexes (low molecular weight iron dextran, ferric carboxymaltose, and iron isomaltoside 1000 [under agreement]) can be given in higher single doses and more rapidly than less recent preparations such as iron sucrose (originator or similars). Test doses are advisable for conventional low molecular weight iron dextrans, but are no more mandatory. Iron supplementation is recommended for all CKD patients with iron-deficiency anaemia and those who receive erythropoiesis-stimulating agents, whether or not they require dialysis. Intravenous iron is the preferred route of administration in haemodialysis patients, with randomized trials showing a significantly greater increase in haemoglobin levels for intravenous versus oral iron and a low rate of treatment-related adverse events during these trials. According ANSM, physicians should apply the product's label recommendations especially the posology. In the non-dialysis CKD population, the erythropoietic response is also significantly higher using intravenous versus oral iron, and tolerability is at least as good. Moreover in some non-dialysis patients, intravenous iron supplementation might avoid or at least delay the need for erythropoiesis-stimulating agents. Following the new ANSM's recommendations, we now have the ability to achieve iron stores replenishment correctly and conveniently in dialysis dependent and non-dialysis dependent CKD patients without compromising safety using the various pharmaceutical forms of iron products especially intravenous compounds.

Oral Anticoagulation Therapy for Elderly Patients With Atrial Fibrillation

Elderly individuals are prone to nonvalvular atrial fibrillation (AF) with associated risks of arterial thromboembolic disease. Despite definitive guidelines, oral anticoagulant therapy (OAC) is notoriously underutilized in patients with AF. Physicians cite excessive bleeding risk as one reason they omit OAC for their older patients with AF. Improved understanding of the pathophysiology of age-related bleeding may improve risk–benefit assessments for warfarin and newer antithrombotic agents. We reviewed the literature to identify age-related pathophysiological elements that can exacerbate the likelihood of bleeding. In the context of the Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile international normalized ratio, Elderly, Drugs/alcohol concomitantly (HAS-BLED) bleeding risk framework, we highlight age-related physiological dynamics that predispose to hemorrhage. The combination of increased age (>65 years) with the other elements of the risk factor stratification model identifies patients with AF who are especially susceptible to OAC-related bleeding, irrespective of the agent used. Empirically adjusting OAC dose relative to these common bleeding risks may help to achieve an improved risk–benefit therapeutic ratio.

Anemia of renal disease: what it is, what to do and what's new

PATIENT GROUP

It is estimated that 15-30% of geriatric cats will develop chronic kidney disease (CKD), and that 30-65% of these cats will develop anemia as their renal disease worsens. Anemia of renal disease is multifactorial in its pathogenesis, but the main cause is reduced production of erythropoietin, a renal hormone that controls the bone marrow's production of red blood cells, as kidney disease progresses.

PRACTICAL RELEVANCE

It is important to recognize the presence of anemia of renal disease so that adequate treatment may be instituted to improve quality of life and metabolic function. Erythrocyte-stimulating agents (ESAs), such as epoetin alfa, epoetin beta and darbepoetin alfa, have been developed to counteract the effects of decreased erythropoietin production by the kidneys. These treatments, which are the focus of this review, have 83% similarity in amino acid sequence to the feline hormone. On average, the target packed cell volume (>25%) is reached within 3-4 weeks of ESA therapy.

CLINICAL CHALLENGES

The use of ESAs has been associated with a number of complications, such as iron deficiency, hypertension, arthralgia, fever, seizures, polycythemia and pure red cell aplasia (PRCA). Darbepoetin has a prolonged half-life compared with epoetin and thus can be given only once a week, instead of three times a week. The incidence of PRCA appears to be decreased with darbepoetin use when compared with epoetin use in cats.

EVIDENCE BASE

There is limited published evidence to date to underpin the use of ESAs in cats. This review draws on the relevant publications that currently exist, and the authors' personal experience of using these therapies for over 5 years.

Influence of enteric nutrition on blood urea nitrogen (BUN) in very old patients with chronic kidney disease (CKD)

The purpose was to check the influence of enteric nutrition on BUN in very elderly patients. Clinical data on patients in whom enteral feeding was initiated after a period of poor oral intake are presented. Patients with evidence of volume depletion, signs of gastrointestinal bleeding or medicines that might increase BUN were excluded. We evaluated 5 patients (mean age 90.6 ± 3 years) who were admitted to geriatric department. Mean plasma creatinine concentration was 1.17 ± 0.34 mg/dl, but mean estimated glomerular filtration rate (eGFR) was 41.6 ± 17 ml/min/1.73 m(2). Enteral nutrition was administered at a dose of mean 1,580 ± 53ml/day at mean duration of 9 ± 4 days. Mean BUN was 52 ± 30 mg/dl at baseline, increases to 109 ± 9.4 mg/dl after initiation of feeding and decreased to 82 ± 1.1mg/dl with reduction of dose of enteral nutrition. Our conclusion was that initiation of enteral feeding may induce a large accumulation of nitrogen waste products in elderly patients in whom serum creatinine is an unreliable indicator of kidney function. High protein intake should be considered in differential diagnosis of disproportionate high increment of BUN.

Cost-effectiveness of colorectal cancer screening in renal transplant recipients

BACKGROUND

Colorectal cancer screening is now standard practice in most developed countries. The aim of this study was to determine the cost-effectiveness of colorectal cancer screening, with annual fecal occult blood testing, in renal transplant recipients.

METHOD

A Markov model was developed to compare the effects of annual fecal occult blood testing (FOBT) as screening for colorectal cancer in a cohort of renal transplant recipients ages 50-70 years, versus no screening. Data on cancer risk and survival were obtained from the ANZDATA Registry. Accuracy of FOBT, cancer stage distribution of the screened and unscreened arms, and adverse effects of colonoscopy were extrapolated from general population data because of unavailability of equivalent data in renal transplant recipients.

RESULTS

When the participation rate was 50%, the average cost for annual FOBT was $5076. The estimated incremental cost-effectiveness ratio was $22,309 per life year saved. Using a series of sensitivity analyses, the choice of screening strategy was most sensitive to the prevalence of disease, test specificities, and participation rate. When the base-case analyses were tested over the worst and best-case scenarios, the incremental cost-effectiveness ratio varied from $32,863 to $95,668 per life year saved.

CONCLUSION

Under the most favorable conditions, immunochemical FOBT screening in renal transplant recipients appears good value for money. Uncertainties, however, exist in the model's influential estimates. Primary research into these uncertainties is necessary to confirm whether population colorectal cancer screening is cost-effective in renal transplant population.

Cancer screening in renal transplant recipients: what is the evidence?

Increased cancer risk is well established in the renal transplant population. Little, however, is known about the benefits and harms of cancer screening, treatment effectiveness, and the overall cancer prognosis in renal transplant recipients. In this study, we critically appraised guidelines for cancer screening in the renal transplant and general populations using standard criteria for an evidence-based screening program. Guidelines were included when they were applied to adult participants, had objectives specific to cancer screening, and were written in English. Recommendations for breast and colorectal cancer screening in the general population were supported by evidence of cancer-specific mortality benefits from randomized, controlled trials of cancer screening. Convincing evidence from observational studies had demonstrated population cervical cancer screening was effective, also, test performance of mammography, faecal occult blood testing, and Pap smear were accurate. Population breast, colorectal, and cervical cancer screening also appeared to be good value for money in the general population. On the contrary, recommendations for cancer screening in renal transplant recipients were entirely extrapolated from data in the general population. Studies in the general population have led to the development of cancer screening guidelines in transplant recipients. Because of increased cancer risk, differences in diagnostic test performance, competing risks for deaths from causes such as cardiovascular disease and reduced overall life expectancies, validity of their recommendations are uncertain. Future studies are needed to address these issues to provide the necessary evidence for informed decision-making.

Predictive Value of a Positive Fecal Occult Blood Test Increases as the Severity of CKD Worsens

BACKGROUND

Because chronic kidney disease (CKD) may be associated with gastrointestinal bleeding from trivial mucosal lesions, we hypothesized that the predictive value of a positive fecal occult blood test (FOBT) result for clinically important colonic lesions would decrease as the stage of CKD worsened.

METHODS

We prospectively identified 1,225 consecutive asymptomatic average-risk patients who were referred for colonoscopy to evaluate a positive FOBT result. Using the Modification of Diet in Renal Disease equation, we estimated glomerular filtration rate (GFR) and staged the severity of CKD by using standard criteria as follows: normal/stage 1 (GFR > or = 90 mL/min/1.73 m2 [> or = 1.50 mL/s]), stage 2/3 (GFR 30 to 89 mL/min/1.73 m2 [0.50 to 1.48 mL/s]), and stage 4/5 (GFR < 30 mL/min/1.73 m2 [< 0.50 mL/s] or dialysis).

RESULTS

Clinically important lesions were identified in 23.9% of 531 individuals with none/stage 1 CKD, 32.8% of 497 subjects with stage 2/3 CKD, and 42.6% of 197 patients with stage 4/5 CKD (P < 0.001). Compared with patients with none/stage 1 CKD, adjusted odds of identifying a clinically important lesion were 1.61 (95% confidence interval, 1.21 to 2.15) in subjects with stage 2/3 CKD and 2.33 (95% confidence interval, 1.62 to 3.36) in patients with stage 4/5 CKD. Prevalences of adenomas of 1 cm or greater (15.1% versus 20.1% versus 22.8%; P = 0.007), carcinomas (5.1% versus 10.1% versus 13.2%; P < 0.001), and vascular ectasias (1.7% versus 2.4% versus 6.1%; P = 0.003) increased with the severity of CKD.

CONCLUSION

Contrary to our initial hypothesis, we found that the predictive value of a positive FOBT result for clinically important colonic lesions increased as the severity of CKD worsened.

HEMATOLOGY: ISSUES IN THE DIALYSIS PATIENT: The Safety of Heparins in End-Stage Renal Disease

In patients on chronic dialysis, unfractionated heparin (UFH) is the most commonly used agent for anticoagulation of the hemodialysis extracorporeal circuit, for hemodialysis catheter "locking" between dialysis treatments, and for nondialysis indications such as venous thromboembolic disease, peripheral vascular disease, and acute coronary artery disease. Potentially serious complications of UFH, such as hemorrhage, osteoporosis, and thrombocytopenia, have led to consideration of other options for anticoagulation, including low molecular weight heparin (LMWH) and direct thrombin inhibitors (DTIs). LMWH can be used for anticoagulation of the hemodialysis circuit, but whether this has significant benefit compared to UFH remains to be proven. Because of the somewhat unpredictable risk of severe bleeding complications when LMWH is used for other indications in dialysis patients, UFH rather than LMWH is preferred for treatment of thromboembolic disease in these patients. DTIs have been used for anticoagulation in dialysis patients with heparin-induced thrombocytopenia (HIT), with argatroban being the preferred agent if heparin-free hemodialysis cannot be performed. UFH still remains the preferred anticoagulant in the vast majority of dialysis patients requiring systemic anticoagulation and for anticoagulation of the extracorporeal hemodialysis circuit.

Issues related to iron replacement in chronic kidney disease

Recent epidemiologic studies show that iron deficiency occurs in the vast majority of patients with chronic kidney disease (CKD). In patients with CKD, increased iron losses and, to a lesser extent, poor oral absorption, can lead to iron-deficiency anemia. Correction of iron-deficiency anemia is preferable by the oral route, however, data on oral iron use are limited in this population. In CKD patients, parenteral iron administered with recombinant human erythropoietin (rHuEpo), is the best potential option for the correction of anemia. Nondextran iron preparations are preferable because of a reduced incidence of serious adverse events. Parenteral iron in CKD patients may not be entirely innocuous and, although commonly used, have not received Food and Drug Administration approval for use in this patient population. Exposure to intravenous (IV) iron may lead to oxidative stress, renal injury, infection, cardiovascular disease, and osteomalacia. Studies are needed to confirm the existence and magnitude of these complications. The current data suggest that the overall risk-benefit ratio favors use of IV iron when compared with untreated or partially treated iron-deficiency anemia.

Nomogram for individualizing supplementary iron doses during erythropoietin therapy in haemodialysis patients

AIMS

An adequate iron supplement is crucial not only for prompt erythropoiesis but also for the restoration of tissue iron reserves in haemodialysis patients receiving recombinant human erythropoietin (r-HuEPO). An attempt was made to establish a comprehensive nomogram that allows individualization of intravenous (i.v.) iron doses according to patients' body weights, the initial status of tissue iron reserves and desired increases in haemoglobin levels.

MATERIALS AND METHODS

Clinical and laboratory data retrieved from 95 haemodialysis patients who received r-HuEPO with or without iron supplements for at least 12 weeks were used to construct the nomogram. It was assumed that the administered iron was either incorporated into newly synthesized haemoglobin and tissue iron reserves or eliminated from the body at a constant rate. Tissue iron reserves of the patients were estimated by serum ferritin levels using van Wyck's equation (Kidney Int., 1989, 35, 712). The rate of iron loss in the patients was estimated by the data obtained from 15 of the above patients who exhibited stable haemoglobin levels but decreases in serum ferritin levels with no iron supplements. The validity of the equation was ascertained by comparing the measured serum ferritin levels at the end of r-HuEPO therapy and those predicted by the nomogram. The proposed nomogram was then validated prospectively in 24 haemodialysis patients to determine whether the nomogram-recommended iron doses would increase both haemoglobin and serum ferritin levels within 12 weeks.

RESULTS

The mean (+/-SD) iron loss of haemodialysis patients was calculated to be 10.5 +/- 7.4 mg/week. There was a significant correlation (r=0.77, P < 0.001) between the measured serum ferritin levels, an index of tissue iron reserves, at the end of r-HuEPO therapy and those predicted by the equations used for formulating the nomogram. The prospective study indicated that the nomogram-recommended supplementary iron doses attained haemoglobin and serum ferritin levels of > 95 g/L and >100 microg/L in 79 and 50% of the patients, respectively, within 12 weeks.

CONCLUSION

The present nomogram may be useful for individualizing supplementary i.v. iron doses for haemodialysis patients undergoing r-HuEPO therapy.

Abdominal Surgery in Chronic Hemodialysis Patients

The number of patients with end-stage renal disease who benefit from chronic dialysis is steadily increasing. This study was designed to assess abdominal surgery in chronic hemodialysis (CHD) patients. A 7-year retrospective study was conducted including all the patients on CHD who underwent abdominal surgery in our unit. These patients were separated into an elective and an emergency surgery group. Forty-three patients underwent surgery. In the elective surgery group (18 patients), the most common diseases were colorectal cancer, symptomatic gallbladder stones, and hernia. There was no death related to surgery in this group, and only one patient developed a complication (5%). In the emergency surgery group (25 patients), the most common diseases were mesenteric ischemia and gastrointestinal bleeding from angiodysplasia. Complications occurred in 10 patients (total morbidity rate, 40%), and 6 of them died (mortality rate, 24%). Gastrointestinal elective surgery in patients on CHD can be performed with low morbidity and mortality rates. The emergency group was differentiated by the high prevalence of bleeding from angiodysplasia and mesenteric infarction, as well as its high surgical mortality rate.

Intravenous iron for the treatment of predialysis anemia

This article, based on our own studies and those of others, presents evidence to show that the anemia of chronic renal failure in the predialysis period is, to a significant extent, caused by iron deficiency and can be improved in most cases by the administration of intravenous (i.v.) but not oral iron. We estimate that in approximately 30% of all predialysis patients with anemia, a target hematocrit (Hct) of 35% can be reached and maintained by giving i.v. iron alone without exceeding currently acceptable limits of serum ferritin (500 microg/liter) or the percentage of iron saturation (40%). If, in addition, subcutaneous erythropoietin (EPO-usually in only low doses-is added, the combination has an additive effect on the Hct response, and almost all anemic predialysis patients can reach and maintain the target Hct of 35% over a one-year period. Therefore, the advantage of maintaining adequate iron stores with i.v. iron is that if EPO is needed, lower doses will be required to achieve the target Hct than if EPO were used alone. This not only avoids the high cost of EPO therapy but also its associated side-effects, especially hypertension. Using Venofer, a ferric hydroxide sucrose complex, as our i.v. iron supplement, we have seen no anaphylactic reactions in over 20,000 infusions over a four-year period in 360 hemodialysis, 123 predialysis, and 58 peritoneal dialysis patients.

Intravenous iron supplementation for the treatment of the anemia of moderate to severe chronic renal failure patients not receiving dialysis

Iron deficiency may develop in hemodialysis patients, especially when erythropoietin is given. The role of iron deficiency in the anemia of predialysis chronic renal failure (CRF), however, is much less clear. We have intravenously (IV) administered iron as ferric saccharate in a total dose of 200 mg elemental iron monthly for 5 months to 33 CRF patients who remained anemic despite oral iron supplementation and who had no laboratory signs of iron overload. None was receiving erythropoietin therapy. In 22 of the patients there was an increase in the hematocrit values by the end of the study. These patients were considered responders to intravenous iron (IV Fe) therapy. In 11 patients the iron administration was not associated with improvement of the anemia (nonresponders). Before onset of the IV Fe therapy there were no differences between the responders and nonresponders with regard to degree of anemia, serum ferritin, iron saturation, renal function, or blood pressure. One additional patient was excluded from the study because of a mild reaction during an IV test dose before the study. No worsening of kidney function and no other side effects were noted. In four patients (three responders and one nonresponder) the control of blood pressure necessitated antihypertensive drug therapy adjustment. In conclusion, IV Fe supplementation in two thirds of anemic CRF patients not receiving dialysis resulted in a significant improvement of the anemia, thus avoiding the necessity of erythropoietin or blood administration. This could be achieved by increasing the plasma ferritin levels to 200 to 400 microns/L and/or increasing the iron saturation to 25% to 35%. Intravenous ferric saccharate appears to be a safe and effective method of administering iron for the correction of anemia in CRF patients not receiving dialysis.

Diagnosis of iron deficiency anemia in renal failure patients during the post-erythropoietin era

The purpose of this study was to evaluate the sensitivity and specificity of laboratory methods in the diagnosis of posterythropoietin-era, iron-deficient, chronic renal failure patients. The patient population comprised 25 anemic (hemoglobin < 11 g/dL) patients with creatinine greater than 3 mg/dL; 20 were dialysis patients, two were transplant patients, and three patients had renal failure from other causes. Criteria for study inclusion were as follows: bone marrow iron was the reference standard and was graded 0 to +4, ranging from absent to diffuse homogeneous iron staining; serum ferritin concentration and serum transferrin saturation were tested in terms of sensitivity and specificity. The reference standard indicated that iron deficiency existed in 40% of patients. Neither serum ferritin nor transferrin saturation were completely adequate diagnostic tools. Serum ferritin levels less than 200 ng/dL were 100% specific for the diagnosis but only 41% sensitive. Transferrin saturation of less than 20% was 88% sensitive, but only 63% specific. By excluding patients with hypoproteinemia (transferrin values of < 150 mg/dL), the sensitivity of the test increased to 100% and the specificity to 80%. We conclude that transferrin saturation is an adequate screening tool in anemic chronic renal failure patients, provided that hypoproteinemia is not present. By determining both the serum ferritin concentration and the transferrin saturation, a high sensitivity and specificity can be achieved, even in patients with hypoproteinemia. Furthermore, we believe that on this basis, iron therapy in patients with renal insufficiency can be improved.

Quantitative reticulocyte analysis may be of benefit in monitoring erythropoietin treatment in dialysis patients

Reticulocyte responses to low-dose erythropoietin (EPO) were monitored using automated flow cytometric analysis. Sixteen adult dialysis patients were treated with 1,000 U of recombinant human EPO (rHuEPO), subcutaneously, thrice weekly (mean dose 15.7, SD 3.7 U/kg). The reticulocyte count (baseline 31.1, SD 19.1 x 10(9)/L) increased in 14 patients in the first week, with a peak response occurring at Week 2 (mean 57.3, SD 26.5 x 10(9)/L, p < 0.01). There was a wide spectrum of response, the maximal absolute increment ranging from 6.8-69.7 x 10(9)/L (maximal percentage increase 19-863%). Overall there was no relationship between the early increment in reticulocyte count and hemoglobin (Hb) response over the ensuing 4 months. Nine patients became transfusion independent (mean Hb increasing from 6.9, SD 0.8-9.2, SD 1.2 g/dl). Two patients had poor reticulocyte increments and no significant change in Hb. The remaining 5 patients responded partially with a brisk reticulocyte response and a marked reduction in transfusion dependency, but without a sustained increase in Hb. On investigation, all had gastrointestinal bleeding (melena in 1, commencing after initiation of treatment, positive fecal occult bloods in 4), whereas none of the other patients showed evidence of blood loss. It is notable that the erythron was sensitive to this modest dose of rHuEPO in the majority of patients as evidenced by the reticulocyte response. The results provide useful information in the management of patients on rHuEPO. A small or inapparent reticulocyte response suggests a confounding factor; a poor Hb response in the presence of active reticulocyte synthesis points to occult blood loss or hemolysis.

Effect of nutrition on morbidity and mortality in maintenance dialysis patients

Protein-calorie malnutrition is common in maintenance dialysis patients. Malnutrition is mild to moderate in approximately 33% of maintenance dialysis patients and severe in approximately 6% to 8%. There are many causes of protein-calorie malnutrition in maintenance dialysis patients; the three major causes are probably low nutrient intakes, intercurrent or underlying illnesses, and the dialysis procedure itself. Malnutrition is a major risk factor for mortality in maintenance dialysis patients. This has been shown most clearly for serum albumin, which is the nutritional parameter that has been most heavily studied. Low dietary of protein or other nutrients and protein-calorie malnutrition revealed by the results of different chemistry analyses are also directly correlated with mortality rates. These data do not prove that poor nutritional intake or malnutrition is a cause of the high morbidity and mortality in maintenance dialysis patients, and randomized, prospective controlled clinical trials are necessary to answer this question. However, the data are consistent with the thesis that malnutrition or inadequate nutrient intake do contribute to high morbidity and mortality in these patients. Although it is possible that increasing the dose of dialysis (eg, Kt/V) will lead to increased appetite and nutrient intake, experience suggests that raising the dose of dialysis, by itself, will not optimize nutritional intake in these individuals. To achieve satisfactory nutritional intake and healthy nutritional status, other interventions will need to be developed.

The gastrointestinal tract in uremia

Gastrointestinal mucosal abnormalities ranging from edema to ulceration occur in two thirds of patients dying of uremia. Early studies suggested that uremic patients on maintenance dialysis treatment were at increased risk of peptic ulceration but more recent data indicate that this is not so. Other gastrointestinal problems reported for uremic subjects on maintenance dialysis treatment include bleeding from telangiectatic lesions, constipation, mucosal deposition of amyloid and acute pancreatitis. Nausea and vomiting are common in the uremic patient but gastric emptying studies have yielded conflicting results. Patients undergoing renal transplantation are at increased risk of development of esophagitis, complicated peptic ulcer, intestinal ulceration, and perforation as well as acute pancreatitis.