Hemodynamics of uremic anemia

Cardiovascular Function in a Chronic Peritoneal Dialysis Pediatric Population on Recombinant Human Erythropoietin Treatment

Anemia, through a hyperkinetic state, is an Important contributor to myocardial function impairment. To determine the cardiovascular effects of recombinant human erythropoietin (rHuEPO) therapy, 10 chronic peritoneal dialysis (CPD)-treated anemic children were studied be fore and during 18 months of treatment. The following parameters were recorded: hemoglobin (Hb) [percent of target level (TL) = x 2 standard deviations of normal Hb values for age and sex], heart rate (HR, beats/minute), mean arterial pressure (MAP, mmHg), end-diastolic left ventricular diameter (EDLVD, mm/sm BSA), shortening fraction (SF, percent), and Interventricular septal thickness (IVS, mm/sm BSA).

Student's t-test for paired data showed (vs time before treatment, TO) a progressive Increase In Hb, a progressive decrease In HR, and a progressive Increase In MAP. EDLVD progressively decreased, while SF and IVS remalned unchanged throughout the study. Regression analysis showed a close correlation between anemIa cor rection and decrease of HR (p<0.01), while no correlation was found between Hb and EDLVD or SF, IVS, or MAP.

Our data indicate that anemia correction In these patients Is mainly associated with a decrease in hyperkinetic state (HR reduction with SF unvaried), while left ventricular function and dimensions remain normal, despite an Increase in MAP.

Management of Hypertension in Dialysis

Arterial hypertension is a highly frequent symptom in end-stage renal failure. This study was designed to evaluate the importance of total exchangeable sodium (NaE), plasma renin activity (PRA) and the adrenergic nervous system in the pathogenesis of high blood pressure. 86 patients were studied (26 with end-stage kidney disease and under conservative treatment and 60 on maintenance haemodialysis).

Under conservative treatment a simple linear regression analysis gave a correlation coefficient of 0.794 for NaE × log. PRA against mean arterial pressure (MAP). This data suggests that before the start of the haemodialytic treatment NaE and PRA are important determinants of hypertension.

In patients undergoing chronic heamodialysis the correlation between MAP and the product of NaE × log. PRA was lost. In hypertensive patients we have found indication of an increased adrenergic activity. In fact resting heart rate and two hours walking plasma catecholamines were significantly higher in hypertensive compared with normotensive patients on dialysis. A significant positive correlation was found between basal plasma noradrenaline levels and MAP in 34 patients treated with periodic haemodialysis when hypothyroid patients were excluded.

Arterial hypertension is a highly frequent symptom in end-stage renal failure and occurs in over 80% of all case histories (1, 2, 3, 4, 5).

This paper is a review of our experience concerned with the pathogenesis and management of hypertension in patients with chronic renal failure.

Clinical Effect of Recombinant Human Erythropoietin on Anemia Associated with Chronic Renal Failure. A Multiinstitutional Study in Japan

Clinical effect and safety of recombinant human erythropoietin (r-HuEPO) were evaluated in 66 hemodialysis patients with intractable anemia. Initially, 50U/kg dry weight (DW) of r-HuEPO was administered intravenously at the end of every hemodialysis procedure for 4 weeks, then the dosage was increased to 100 and 200U/kg DW for poor responders. The patients’ hematocrits rose from 19.8 ± 2.3% (pretreatment) to 30.2 ± 4.9% after 12 weeks. From 206 U of blood transfusion requirement in the 3-month period before the study, only 34 U were needed after treatment. Serum iron and ferritin levels fell significantly during the study, and iron storage was considered to be one of the decisive factors in the response to r-HuEPO. Blood pressure rose in the course of r-HuEPO administration, but uncontrollable hypertension was rarely observed. There was no significant adverse effect of r-HuEPO except for this mild hypertension. These results indicate that r-HuEPO is an excellent therapeutic aid for the anemia associated with chronic renal failure.

Hemodynamic and Cardiac Effects of Erythropoietin in Patients on Regular Dialysis

The long-term impact of erythropoietin (EPO) treatment on cardiac structures and function was prospectively studied in eight hypertensive (Group I) and seven normotensive (Group II) patients on hemodialysis (HD). Doppler-echocardiograms were done before EPO and at two and twelve months of treatment. Mean hemoglobin (± SD) before EPO was 6.4 ± 0.9; it rose significantly up to two months and then remained constant. At two months, cardiac index (CI) had significantly decreased, while peripheral vascular resistances increased. Five patients required increased antihypertensive drug treatment. No changes were seen in myocardial parameters at this short follow-up. After one year, left ventricular mass index (LVMi) decreased (p < 0.05) in both groups concomitantly with a decrease in diastolic diameter and septum and posterior wall thicknesses. Basal LVMi was higher in Group I than in Group II, and after one year the regression was more marked in Group II. Left cardiac work showed prompt and steady improvement in both groups. Maintained partial correction of anemia with EPO during one year was associated with a return to normal of high CI, decreased left cardiac work and impressive regression of left ventricular hypertrophy.

Blood Pressure after three Different forms of Correction of Anemia in Hemodialysis

It is not known whether recombinant human erythropoietin has a direct, clinically apparent pressor effect in hemodialysis patients or whether hypertension developing or aggravated in these patients merely reflects increased hematocrit. We compared blood pressure after three different methods of partial correction of anemia in hemodialysis patients with similar baseline hematocrits (erythropoietin n=12, intravenous iron alone n=10, androgens n=9). Shortly after the start of treatment and with a minimally increased hematocrit, the need for antihypertensive medication increased in the erythropoietin group. No such pressor effect was observed with iron or androgens. These data suggest a direct hypertensive effect of erythropoietin in some patients on hemodialysis.

Seizures in Dialysis Patients Treated with Recombinant Erythropoietin. Review of the Literature and Guidelines for Prevention

Anemia is one of the major limitations to rehabilitation in patients with end-stage renal disease (ESRD). The efficacy of recombinant human erythropoietin (rHuEPO) in the treatment of renal anemia is well established. Nevertheless, rHuEPO therapy has been associated with serious untoward effects. There appears to be an increased risk of hypertension, not infrequently accompanied by hypertensive encephalopathy and seizures. The mechanism of hypertension remains uncertain. It is associated with an increase in blood viscosity, a reversal of hypoxic vasodilatation, and, possibly, a direct pressor effect of the hormone. Seizures, otherwise, may be the result of cerebral hypoperfusion and, finally, of a focal cerebral edema. The guidelines for rHuEPO treatment and prevention of associated convulsions are outlined. The possible convulsive risk induced by this treatment, even at low doses, particularly in patients with a previous history of seizures, is stressed.

Anemia management in oncology and hematology

Anemia is frequent in cancer patients and its incidence increases with chemotherapy. The probability of requiring transfusions also increases with chemotherapy. Anemia negatively impacts survival and accentuates fatigue in cancer patients. Cancer promotes inflammatory cytokine production, which suppresses erythropoiesis and erythropoietin (EPO) production. Erythropoiesis-stimulating agents (ESAs) improve erythropoiesis and reduce transfusion needs in anemic cancer patients receiving chemotherapy. However, meta-analyses have shown an increased risk of thromboembolic (TE) events with ESA use during chemotherapy, but not increased on-study mortality or reduced overall survival. Three reasons have been proposed to explain why ESAs might have adverse effects in anemic cancer patients: tumor progression due to stimulation of tumor cell EPO receptors; increased risk of TE; and reduced survival. However, erythropoietin is not an oncogene, nor is the EPO receptor. It has also been demonstrated that erythropoietin does not stimulate tumor proliferation. Increased TE risk associated with ESAs is probably a consequence of increased blood viscosity due to excessive RBC mass elevation with concomitant plasma volume contraction, nitric oxide scavenging, and endothelial cell activation. Increased ESA dosing may also impact survival negatively because EPO contracts the plasma volume and stimulates inflammatory cytokine production independently of increasing erythropoiesis. Furthermore, transfusions themselves are associated with an increase in TE and plasma volume contraction, and these events are potentiated when ESAs are given with transfusions. An update on the management of anemia in oncology, the potential adverse events of ESAs, the benefits and risks of transfusions, and QoL are discussed in this paper.

Hemodynamic Effects of Arteriovenous Fistula in End‐Stage Renal Failure

Hemodynamic parameters using Swan Ganz catheter were studied in 17 patients with end stage renal disease. The acute effects of radiocephalic AV fistula on the hemodynamic parameters were studied at 24 hours of surgery. The chronic effects were studied in 8 of these patients at 6 weeks of arteriovenous (AV) fistula. The AV fistula matured in 3 to 4 weeks time and blood flow was sufficient for hemodialysis (400 mL/min). Patients with chronic renal failure had normal or high normal hemodynamic parameters. Six weeks after the AV fistula, the cardiac index and the stroke volume index slightly increased along with a significant increase in systolic and mean systemic arterial pressure. None of the patients had significant increase in cardiac filling pressures. Although there was some fall in systemic vascular resistance index and rise in cardiac index and stroke volume index, these changes were physically small and unlikely to put any extra hemodynamic load. Thus, AV fistula in dialysis patients is not an appreciable cause of circulatory or pulmonary congestion.

Arterial hypertension induced by erythropoietin and erythropoiesis-stimulating agents (ESA)

This review summarizes the evidence for a hypertensinogenic effect of Erythropoietin (Epo) in normal human subjects and predialysis, hemodialysis, and continuous ambulatory peritoneal dialysis (CAPD) patients. The possible mechanisms of Epo-induced hypertension are examined with in vivo animal and in vitro data, as well as pathophysiological human studies in both normal subjects and CKD patients. The evidence for a hypertensinogenic effect of erythropoiesis-stimulating agents (ESAs) in normal subjects, predialysis CKD, hemodialysis, and CAPD patients is compelling. Epo increases BP directly and notably independently of its erythropoietic effect and its effect on blood rheology. The potential for the development of future agents that might act as specific stimulators of erythropoiesis, devoid of direct hemodynamic side effects is underscored.

Hypertension induced by erythropoietin has a correlation with truncated erythropoietin receptor mRNA in endothelial progenitor cells of hemodialysis patients

Endothelial nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) contribute to erythropoietin (EPO)-induced hypertension, a major adverse reaction associated with EPO therapy. To investigate the mechanism of EPO-induced hypertension, we examined circulating endothelial progenitor cells (EPCs) taken from 56 hemodialysis (HD) patients. Among these EPCs (which reflect the condition of the endothelium), we looked for EPO receptor (EPOR) mRNAs. A truncated form of EPOR acts as a dominant negative regulator of EPO signaling, leading to hypertension. We found that the ratio of truncated EPOR mRNA in EPCs has a correlation with EPO-induced increase in blood pressure (r = 0.36, P = 0.02). The ratio of truncated to total EPOR mRNA in EPCs had an inverse correlation with EPO-induced cGMP production in vitro (r = -0.31, P = 0.02). A similar correlation was observed in cultured human endothelial cells after transfection of the full-length or truncated forms of EPOR (r = -0.92, P < 0.001). It follows, therefore, that evaluation of EPOR isoform mRNA in EPCs can predict EPO-induced hypertension. The termination of the EPO signal by truncated EPORs may decrease NO/cGMP production after EPO exposure, thereby raising blood pressure.

Transplant reno-vascular stenoses associated with early erythropoietin use

BACKGROUND AND OBJECTIVES

This report describes an unusual presentation of severe hypertension (HTN) in a subset of pediatric kidney recipients treated with a steroid avoidance pediatric renal transplantation protocol. The HTN was secondary to atypical, reno-vascular abnormalities (RVA) of the transplanted vasculature, temporally associated with erythropoietin (EPO) use.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

To investigate the clinical significance underlying this event, a retrospective clinical study of 100 pediatric renal transplants was undertaken (50 steroid-free and 50 matched steroid-based controls), with peripheral blood transcriptional analysis of four RVA patients and controls.

RESULTS

Regardless of a higher observed incidence of anemia (p < 0.001) and greater overall EPO usage in the first post-transplant year in steroid-free patients, the incidence of new-onset HTN at one yr was significantly less in the steroid-free cohort (p = 0.03). Nevertheless, early EPO (first week post-transplant) was significantly associated with the combinatory findings of new-onset HTN (p = 0.03) and RVA (p = 0.007). Molecular mechanisms of RVA injury were investigated further by peripheral blood cDNA microarray gene expression profiling. A panel of 42 transcripts differentiated patients with RVA and HTN from three sets of matched controls, with and without HTN and EPO use, with 100% concordance (p < 0.001). The biological processes governed by these significant genes suggest a role for EPO regulation of growth factor receptor ubiquitination as a putative mechanism for renal vascular injury.

CONCLUSION

This study cautions against the use early post-transplant use of EPO in immunosuppression regimens with steroid minimization/avoidance, which may have an increased incidence of post-transplant anemia.

Mechanism of increased mortality risk with erythropoietin treatment to higher hemoglobin targets

Recent randomized, controlled trials indicate that there is a strong trend for increased risk for death or adverse composite outcomes with erythropoiesis-stimulating agent treatment in kidney disease to hemoglobin targets higher than those currently recommended. The failure of these trials to find a benefit of higher hemoglobin is in stark contrast to findings from large, observational, population-based studies that continue to demonstrate the association of low hemoglobin with adverse outcomes. The mechanisms for the adverse effect of higher hemoglobin targets that are seen in the randomized, controlled trials are poorly understood. This review explores hypotheses involving (1) the effect of achieved hemoglobin itself, (2) the role of erythropoiesis-stimulating agent treatment, (3) the use of iron supplementation, (4) increased blood pressure, and (5) erythropoiesis-stimulating agent hyporesponsiveness. Because the causal pathway has yet to be determined, further research is strongly encouraged. Clinical practice, however, should avoid erythropoiesis-stimulating agent treatment to higher hemoglobin targets, particularly in those with significant cardiovascular morbidity and those who require disproportionately high dosages of erythropoietin-stimulating agents to achieve recommended hemoglobin levels.

The use of recombinant human erythropoietin in humans

Recombinant human erythropoietin (rhEPO) has now been in clinical trials for over three years. It has been shown to be nearly uniformly effective in correcting the anaemia of patients on haemodialysis or patients with progressive chronic renal failure not yet on dialysis. Preliminary results indicate that rhEPO is effective in increasing the ability of individuals to donate blood for self-use and early trials have shown the drug to increase the haematocrit in patients with rheumatoid arthritis. Trials in patients with anaemia associated with cancer or myelodysplastic syndromes are warranted. rhEPO will have a major impact as a therapeutic, particularly in patients with renal disease.

UNRESOLVED ISSUES IN DIALYSIS: Management of Intradialytic Hypertension: The Ongoing Challenge

There is no widely accepted definition of intradialytic hypertension. Arbitrary clinical definitions have included an increase in blood pressure during or immediately after hemodialysis, a rise in blood pressure during the second or third hour of dialysis, and an increase in blood pressure that is resistant to ultrafiltration. To date, no studies have evaluated the prevalence and prognostic importance of intradialytic hypertension. The pathogenesis of intradialytic hypertension is complex and is due in part to extracellular fluid volume expansion, increased cardiac output, activation of the renin-angiotensin system and the sympathetic nervous system, increased circulating vasoactive substances resulting in peripheral vasoconstriction, erythropoietin use, and fluctuations in electrolytes and removal of antihypertensive medications during the dialysis procedure. Management strategies of intradialytic hypertension are based on expert opinion using the pathophysiologic principles described above. We conclude that additional epidemiologic, basic science, and interventional studies are needed to further elucidate the prevalence, prognostic importance, pathophysiology, and potential treatment of intradialytic hypertension.

Pathologic Basis and Treatment Considerations in Chronic Kidney Disease-Related Hypertension

Chronic kidney disease (CKD) is both a cause and an effect of hypertension and is multifactorial in its origin. Beyond volume expansion, CKD-related hypertension is without defining characteristics of any consistency. Consequently, the order in which antihypertensive medications are given to the CKD patient with hypertension is arbitrary, although prescription practice is for the most part mindful of the need for multiple drug classes with at least one of them being a diuretic. It is not without reason that blood pressure goals in the hypertensive CKD patient are set at lower levels than those for patients with essential hypertension, but it remains to be determined how much the blood pressure should be decreased in the CKD patient.

A single monoclonal antibody as probe to detect the entire set of native and partially unfolded rhEPO glycoforms

Human erythropoietin (hEPO) is a highly heterogeneous glycosylated protein that requires well-characterised immunochemical reagents to evaluate the glycoform profile along its biotechnological production as a recombinant hormone. These reagents should be suitable for several assay conditions (like those used for immunoblotting analysis, liquid or solid-phase quantitative assays, immunoaffinity purification) with no glycoform selectivity. Five anti-recombinant hEPO monoclonal antibodies (mAbs) were characterised with the aim of selecting the appropriate reagent. These antibodies mapped two spatially distinct epitopes and neutralised the in vitro biological activity of the cytokine. All of them were able to bind to both, the partially denatured and the native form of the protein. Isoelectric focusing analysis followed by immunoblotting confirmed that all the mAbs, herein described, were able to bind to each glycoform, recognising amino acid sequences of the hEPO. Nevertheless, only mAb 2B2 preserved the ability to bind to soluble recombinant human erythropoietin (rhEPO) when it was coated to polystyrene plates or immobilised on CNBr-activated Sepharose matrix. Besides, mAb 2B2 was able to bind to the complete set of soluble rhEPO glycoforms, showing the same affinity for the glycosylated and deglycosylated cytokine. Thus, mAb 2B2 was useful as a capture antibody to develop a sandwich enzyme-linked immunosorbent assay (ELISA), performing a simple, specific and fast assay to quantify rhEPO with a detection limit of 7 ng ml(-1). mAb 2B2 was also satisfactorily employed as affinity ligand to purify rhEPO. Our work led us to find a suitable and single reagent to perform a variety of immunochemical approaches, where the binding of each glycoform in the native or partially unfolded form of rhEPO is required.

Cardiac performance and morphology in end-stage renal disease

Patients with end-stage renal disease (ESRD) experience a variety of hemodynamic and metabolic abnormalities that predispose to alterations in cardiac performance and morphology. High cardiac output related to renal anemia, hypertension, volume overload, and the arteriovenous fistula (in patients on hemodialysis) predispose to eccentric left ventricular (LV) hypertrophy. Hypertension, aortic stiffness, and aortic stenosis predispose to concentric LV hypertrophy. Most ESRD patients have a hybrid form of LV hypertrophy. LV hypertrophy is commonly accompanied by LV diastolic dysfunction. LV systolic dysfunction is less common. Newer dialytic techniques, excellent control of hypertension, and correction of renal anemia produce regression of LV hypertrophy. The effect of these interventions on LV systolic and diastolic function is less well established. Alterations in serum calcium, choice of dialysate base, hypoxia, and comorbid conditions may influence the effects of dialysis (particularly hemodialysis) on LV function. A variety of negative inotropic drugs may depress LV function in patients with ESRD.

Vasoactive effects of erythropoietin on human placental blood vessels in vitro

OBJECTIVE

The aim of this study was to investigate the direct effect of erythropoietin on human placental vessels.

STUDY DESIGN

Placental vessel rings (n = 8 for each group) from uncomplicated pregnancies were exposed to recombinant human erythropoietin (10-300 IU/mL) in an isometric myograph. One-way analysis of variance with the Bonferroni posttest was used to evaluate significant levels of differences.

RESULTS

Recombinant human erythropoietin evoked reproducible contractions on the vessel rings in a dose-dependent way, which were marked significantly more on veins than on arteries. These contractile responses were not changed by captopril (10(-5) mol/L) but were blunted significantly by losartan (10(-5) mol/L).

CONCLUSION

We concluded that recombinant human erythropoietin exerts a direct contractile effect on human placental vessels, angiotensin II type 1 receptors are needed to mediate these responses, and erythropoietin might participate in one of the humoral mechanisms that are involved in the control of the human placental vascular bed and also in the pathogenesis of intrauterine growth restriction and preeclampsia.

Successful treatment of severe orthostatic hypotension with erythropoietin

A 71-year-old man, who was diagnosed with familial amyloidosis type I, was admitted for treatment of severe orthostatic hypotension associated with recurrent syncopal attacks. Head-up tilt testing demonstrated severe orthostatic hypotension (114/72 mmHg in the supine position and 62/34 mmHg in the upright position) with syncope or presyncope. Oral midodorine and fludrocortisone therapies failed to prevent his symptoms. After administration of subcutaneous erythropoietin, his blood pressure drop in the upright position was decreased and symptoms disappeared unassociated with improvement of anemia. Although previous reports have shown that the mechanism by which erythropoietin improves orthostatic hypotension is related to improvement in anemia, other mechanisms may also play a role.

Recurrence of left ventricular hypertrophy following cessation of erythropoietin therapy

The high cardiac output state is considered a major factor for occurrence of left ventricular hypertrophy (LVH). Increased left ventricular mass is a powerful predictor of morbidity and mortality. We analyzed morphologic changes of the heart in dialysis patients during treatment with erythropoietin (EPO) and after cessation of therapy. Fourteen hemodialysis patients were treated with EPO for 1 year. They were above age 18, dialyzed 3 times per week, and with a hematocrit below 28 vol%. EPO was given subcutaneously, at a dose of 20 U/kg body weight 3 times per week, before each hemodialysis session. Anemia was corrected and hematocrit maintained between 30 and 35 vol%. When this part of the study was completed, EPO was stopped in all 14 patients. Echocardiography was performed three times: at baseline, at 12 months of therapy, and 1 year after EPO cessation. Mean hematocrit of the group at these 3 time intervals was 23.78 +/- 2.11 vol%; 33.14 +/- 1.95 vol%; and 25.93 +/- 5.23 vol%, respectively (mean +/- SD). The following echocardiographic changes occurred. End-diastolic volume decreased from 134.8 +/- 25.4 to 113.2 +/- 26.4 ml and increased back to 136.2 +/- 46.2 ml. Left ventricular mass decreased from 296.6 +/- 62.4 to 225.2 +/- 52.7 g and increased again to 311.7 +/- 106 g. Cardiac output decreased from 7,295.8 +/- 2,166.9 to 5,816.4 +/- 1,216.2 ml/min and increased to 6,803.2 +/- 1,646.5 ml/min. Total peripheral resistance increased from 1,360.8 +/- 428 to 1,691.3 +/- 326 and decreased again to 1,242.8 +/- 303.3 dyne x s/cm5. All these changes were significant. Mean arterial pressure increased from 114.7 +/- 13.9 to 119.3 +/- 13.8 mm Hg and decreased to 100.5 +/- 9.3 mm Hg. LVH could be affected severely by the degree of anemia in uremics and was reversible.

Effect of 1-week treatment with erythropoietin on the vascular endothelial function in anaesthetized rabbits

Chronic administration of erythropoietin (EPO) is often associated with hypertension in animals and humans. The aim of this study was to estimate whether 1-week treatment with EPO can affect the vascular endothelial function. Rabbits were given with EPO (400 iu kg(-1) s.c.) or saline each other day for 1 week. Hypotensive responses to intravenously given acetylcholine (ACh), endothelium-independent nitric oxide donors (NOC7, nitroprusside and nitroglycerin) and prostaglandin I2 were tested before and after administration of N(G)-nitro-L-arginine methyl ester (L-NAME), a specific nitric oxide synthase inhibitor, under pentobarbitone anaesthesia. Blood haemoglobin concentration in EPO group was significantly higher than that in control group, whereas baseline values of aortic pressure, heart rate and femoral vascular resistance were similar. The dose of ACh (172 ng kg(-1)) requiring for a 15 mmHg hypotension from the baseline in EPO group was apparently higher than that (55 ng kg(-1)) in control group. On the contrary, hypotensive responses to NOC7, nitroprusside, nitroglycerin and prostaglandin I2 were comparable between two groups. The extent of ACh-induced hypotension did not correlate with haemoglobin concentration. L-NAME significantly inhibited the ACh-induced vasodilating response in control group but did not in EPO group. In another set of rabbits, the same treatment with EPO also decreased vasodilating responses to carbachol, bradykinin and substance P besides ACh as compared with control group. These results indicate that 1-week treatment with EPO selectively attenuates depressor responses to endothelium-dependent vasodilators in anaesthetized rabbits, most likely due to inhibition of endothelial nitric oxide synthase.

Risk factors for cardiovascular disease in children on maintenance dialysis

Cardiovascular disease mortality is high in children on maintenance dialysis, accounting for about 25% of patient deaths. Cardiovascular-related mortality rates for children on dialysis are higher than for children with successful kidney transplants. Data on the long-term consequences of risk factors for cardiovascular disease are lacking for pediatric end-stage renal disease patients. This article reviews pediatric data pertaining to the following risk factors: anemia, hypertension, hyperlipidemia, left ventricular hypertrophy, abnormal calcium-phosphorus metabolism, and hyperhomocysteinemia. The potential relationship of end-stage renal disease to the etiology of several functional disorders of the cardiovascular system is discussed. Clinical studies are needed to assess the prevalence of cardiovascular disease and of cardiovascular disease risk factors in the pediatric end-stage renal disease population. Possible preventive and therapeutic guidelines need to be developed for at-risk children on maintenance dialysis.

High Output Cardiac Failure

Congestive heart failure describes a syndrome with complex and variable symptoms and signs, including dyspnea, increased fatigability, tachypnea, tachycardia, pulmonary rales, and peripheral edema. Although this syndrome usually is associated with low cardiac output, it may occur in a number of so-called high output states, when the cardiac output is normal or greater than normal. A high output state may occur in chronic severe anemia, large arteriovenous fistula or multiple small arteriovenous shunts as in Paget's bone disease, some forms of severe hepatic or renal disorders, and acutely in septic shock. The syndrome of systemic congestion in a high output state is traditionally referred to as high output heart failure. However, the term is a misnomer because the heart in these conditions is normal, capable of generating very high cardiac output. The underlying problem in high output failure is a decrease in the systemic vascular resistance that threatens the arterial blood pressure and causes activation of neurohormones, resulting in an increase in salt and water retention by the kidney. Many of the high output states are curable conditions, and because they are associated with decreased peripheral vascular resistance, the use of vasodilator therapy for treatment of congestion may aggravate the problem. There are other clinically important issues in high output failure that have received little attention in the current medical literature. This article reviews the available data on high output cardiac failure with particular emphasis on the underlying mechanisms and treatment.

The heterogeneous and delayed course of blood pressure normalization in hypertensive patients after bilateral nephrectomy with and without subsequent renal transplantation

BACKGROUND

Controversy exists about the time course of blood pressure normalization following bilateral nephrectomy. We sought to evaluate the time course of blood pressure normalization following bilateral nephrectomy and after subsequent kidney transplantation.

METHODS AND RESULTS

Clinical data from 14 hypertensive patients were retrospectively assessed. Baseline blood pressure was 175 +/- 33/109 +/- 9 mmHg. Ten patients firstly underwent unilateral nephrectomy, which resulted in a slight increase of blood pressure (185 +/- 22/110 +/- 5 mmHg). One month following bilateral nephrectomy, blood pressure was 167 +/- 23/104 +/- 17 mmHg, at 3 months 159 +/- 42/104 +/- 25 mmHg, and at 6 months 149 +/- 41/96 +/- 30 mmHg. Antihypertensive medication was necessary in 9/14 patients at a 2 year follow-up. Eight patients remained anephric (group I), 6 patients had subsequent kidney transplantation (group II). In group I, blood pressure was 159 +/- 42/93 +/- 17 mmHg and 129 +/- 34/75 +/- 14 mmHg at 3 and 6 months, respectively (p< 0.05 vs. baseline). In group II, blood pressure decreased from 188 +/- 42/ 128 +/- 46 mmHg to 167 +/- 48/113 +/- 32 mmHg at 3 months, but increased after transplantation to 186 +/- 39/118 +/- 33 mmHg. Antihypertensive medication was still necessary in 5 transplanted patients (83%) and in 3 anephric patients (38%).

CONCLUSION

Adaptation of the blood pressure response following bilateral nephrectomy is a time requiring process, and long-term antihypertensive medication may still be necessary.

Myocardial morphology and cardiac function in rats with renal failure

The effects of chronic renal failure on cardiac performance and myocardial morphology were studied in rats: 17 with 5/6 nephrectomy (CRF rats) and 12 with sham operation (controls). Cardiac function was assessed 8 weeks postoperatively, using the Langendorff technique for an isolated working heart model. After the hemodynamic study the hearts were fixed for electron and light microscopy. In the CRF rats left ventricular systolic pressure was significantly higher at all preloads (10-20 cmH2O) and afterloads (70-90 cmH2O), and left ventricular stroke work was significantly increased at preload 20 cmH2O with afterloads 70 or 90 cmH2O. Light microscopy revealed fibronecrotic lesions consisting of fibroblastic proliferation with newly formed collagen interposed between or entrapping degenerative myocytes. The changes were focally distributed, with perivascular accentuation and were most frequent in the basal half of the ventricular wall. Electron microscopy of non-necrotic myocytes showed intact myocytes, with mitochondria morphometrically similar in the 2 groups, but a significantly lower incidence of mitochondrial granules in the CRF rats. Thus 8 weeks of CRF showed no cardiac dysfunction associated with the focally distributed fibronecrotic myocardial lesions and decrease in mitochondrial granules. The precise mechanism of the discrepancy between the morphological change and the cardiac function is unclear. One possible explanation may be that because the pathological changes in the myocardium were focal or mild to moderate, some compensation mechanism may be involved or it may be the turning point of functional change from acute renal failure to the chronic state.

Mechanism of erythropoietin-induced hypertension

Chronic administration of erythropoietin (EPO) is associated with an increase in arterial blood pressure in patients and animals with chronic renal failure (CRF). Several mechanisms have been considered in the pathogenesis of EPO-induced hypertension. These include the possible role of the rise of hematocrit and erythrocyte mass, changes in production or sensitivity to endogenous vasopressors, alterations in vascular smooth-muscle ionic milieu, dysregulation of production or responsiveness to endogenous vasodilatory factors, a direct vasopressor action of EPO, and finally arterial remodeling through stimulation of vascular cell growth.

Recombinant human erythropoietin inhibits iNOS activity and reverts vascular dysfunction in splanchnic artery occlusion shock

1. We investigated the effects of recombinant human erythropoietin (rh-EPO) in splanchnic artery occlusion (SAO) shock. Sham operated animals were used as controls. Survival rate, mean arterial blood pressure (MAP), serum Tumor Necrosis Factor (TNF-alpha), plasma nitrite/nitrate concentrations, red blood cell (RBC) count, blood haemoglobin (Hb), the responsiveness of aortic rings to phenylephrine (PE, 1 nM-10 microM) and the activity of inducible nitric oxide synthase (iNOS) were studied. 2. SAO shocked rats had a decreased survival rate (0% at 4 h of reperfusion, while sham shocked rats survived more than 4 h), enhanced serum TNF-alpha concentrations, increased plasma nitrite/nitrate levels (60+/-9.5 microM; sham shocked rats= 2+/-0.4 microM), decreased MAP, unchanged RBC count and blood Hb and enhanced iNOS activity in the aorta. Moreover aortic rings from shocked rats showed a marked hyporeactivity to PE. 3. Rh-EPO (25, 50 and 100 U 100 g(-1), 5 min following the onset of reperfusion) increased survival rate (70% at 4 h of reperfusion with the highest dose), reduced plasma nitrite/nitrate concentrations (10.3+/-3.3 microM), increased MAP, did not change RBC count and blood Hb, and inhibited iNOS activity in thoracic aortae. Furthermore rh-EPO, either in vivo or in vitro (10 U for 1 h in the organ bath), restored to control values the hyporeactivity to PE. Finally rh-EPO inhibited the activity of iNOS in peritoneal macrophages activated with endotoxin. 4. Our data suggest that rh-EPO protects against SAO shock by inhibiting iNOS activity.

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.

Renal anaemia treatment with recombinant human erythropoietin increases cardiac output in patients with ischaemic heart disease

An increase in blood pressure is common during treatment of renal anaemia with recombinant human erythropoietin (rhEPO). Concomitant findings of a decrease in cardiac output indicate that an increase in the peripheral flow resistance underlies the increase in blood pressure. The aim of this study was to elucidate the haemodynamic changes during rhEPO treatment in patients with ischaemic heart disease (IHD). Haemodynamic variables were assessed by impedance cardiography in 18 consecutive patients with renal anaemia before and after rhEPO treatment. IHD was found in eleven of these patients. The remaining seven served as controls. Before rhEPO treatment, the cardiac index was decreased in the group of patients with IHD, compared with controls and healthy subjects. Due to an increase in stroke index, the cardiac index increased during rhEPO treatment and reached values equal to those in the control group. The blood pressure increased and the increase in mean arterial pressure was correlated to the increase in cardiac index. Apparently the patients with IHD were unable to compensate for anaemia by increasing their cardiac index. Anaemia treatment increased cardiac index, which in turn caused an increase in blood pressure in these patients.

Effects of recombinant human erythropoietin on blood pressure and renal function in SHR with chronic renal failure

1. The effects of chronic administration of erythropoietin (EPO) on blood pressure and renal function in rats with ablation of renal mass were assessed. 2. Spontaneously hypertensive rat were subjected to 5/6 nephrectomy (5/6Nx). Four weeks after the operation, the rats were randomly allocated to vehicle, EPO 20IU/kg i.p., or EPO 100 IU/kg i.p. (both given twice a week) for 4 weeks. 3. Marked anaemia was noted in SHR-5/6Nx. EPO caused a significant increase in haematocrit at a high dose but not at a low dose. A dose dependent relationship was noted in the EPO-induced rise in the systolic blood pressure. 4. EPO dose-dependently increased urinary protein excretion. It also increased blood urea nitrogen and serum creatinine levels. 5. These results suggest that EPO ameliorates anaemia and severely accelerates renal failure in SHR-5/6Nx. They also suggest that anaemia can be a haemodynamically favorable adaptation to chronic renal disease and that its correction may have adverse renal haemodynamic and structural consequences.

Erythropoietin enhances vascular responsiveness to norepinephrine in renal failure

The mechanism of hypertension induced by recombinant human erythropoietin (rHuEPO) is unclear but may include an increase in peripheral vascular resistance. We studied changes of arterial pressure and plasma endothelin in nine consecutive hemodialysis patients before, and 6 and 12 weeks after, starting rHuEPO. In six patients, changes in cardiac index (CI), stroke index (SI) and total peripheral resistance index (TPRI) were measured by bioimpedance, and forearm vascular responsiveness to intra-arterial norepinephrine (30 to 240 pmol/min) and endothelin-1 (5 pmol/min) were assessed. Six healthy age and sex matched subjects also underwent assessment of forearm vascular responsiveness to norepinephrine and endothelin-1. Treatment with rHuEPO significantly increased hemoglobin and mean arterial pressure (MAP). TPRI also increased by 35 +/- 11%. Plasma endothelin, although elevated basally, remained unchanged. Intra-arterial infusion of norepinephrine caused a maximal increase in forearm vascular resistance (FVR) of 17 +/- 9% before rHuEPO, significantly less than the 32 +/- 5% increase in healthy control subjects (P = 0.04). The response increased to 65 +/- 15% (P = 0.03) after 12 weeks rHuEPO treatment (P = 0.51 vs. controls). Endothelin-1 caused a maximal increase of FVR at 60 minutes of 45 +/- 24% before rHuEPO, which was not significantly different from controls, and tended to decrease with rHuEPO therapy. The response to endothelin-1, but not norepinephrine, correlated inversely with MAP (r = -0.52; P = 0.03) and TPRI (r = -0.51; P = 0.04). In conclusion, these studies show that anemia in chronic renal failure is associated with depressed vascular responsiveness to norepinephrine which is restored by rHuEPO therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence-based recommendations for the clinical use of recombinant human erythropoietin

In an era of increasing scrutiny regarding use of health care resources, it is critical that physicians have rational, evidence-based guidelines for treatment decisions. This review of more than 200 published papers constitutes a comprehensive approach to evaluating the current evidence regarding the clinical use of recombinant human erythropoietin therapy in renal failure patients. After this review, specific recommendations are provided regarding who should receive r-HuEPO; what the target hemoglobin should be; the best route of administration of r-HuEPO; how iron status should be evaluated and managed; and monitoring and follow-up of patients taking r-HuEPO. Throughout the article, areas for important future research are also identified.

Pressor effect of recombinant human erythropoietin: results of ambulatory blood pressure monitoring and home blood pressure measurements

We investigated whether treatment of anemic hemodialysis patients with a low dose of recombinant human erythropoietin (erythropoietin) for a short period would increase their blood pressure. Ambulatory blood pressure monitoring and home blood pressure measurements were used to detect minute increase in blood pressure. Thirty-two patients with a hematocrit of 25% or less received erythropoietin at the dose of 4500 IU/week, by the intravenous route for 8 weeks. Erythropoietin increased the hematocrit from 20.9 +/- 2.1 to 26.2 +/- 2.1%. Erythropoietin elevated mean ambulatory blood pressure by 5 mmHg or more in two-thirds of patients (n = 20; pressor group), while it elevated home mean blood pressure by 5 mmHg or more in one-third of patients (n = 11). An increase in clinic mean blood pressure by more than 5 mmHg was observed only in one-fourth of patients (n = 7). Circadian variation of blood pressure (nocturnal fall and diurnal rise) had been attenuated in the patients of the pressor group before erythropoietin treatment and erythropoietin decreased the nocturnal fall of blood pressure further more. Erythropoietin elevated nocturnal blood pressure more than diurnal blood pressure. Therefore, the increase in blood pressure induced by erythropoietin was detected more reliably by ambulatory blood pressure monitoring. There was no relation between the change in hemoglobin concentration and the increase in ambulatory blood pressure induced by erythropoietin. Erythropoietin tended to decrease cardiac output and plasma volume while it increased total peripheral resistance. It also decreased plasma norepinephrine and vasopressin levels but did not affect other humoral factors. Although the pressor effect of erythropoietin treatment for 8 weeks at the dose of 4500 IU/week was not evident on clinic blood pressure measurements, any increase in blood pressure determined by ambulatory blood pressure should be treated carefully to reduce the risk of a cardiovascular complication in patients receiving hemodialysis.