Effect of enalapril on haemoglobin and serum erythropoietin in patients with chronic nephropathy

Prevalence of Anemia in Type 2 Diabetic Patients and ‎correlation with Body Mass Index and Kidney ‎function in Palestine

Background

The objective of this study was to determine the prevalence of anemia in patients with type 2 diabetes mellitus and ‎to identify the set of anthropometric and biochemical factors that jointly influence ‎the diabetic and anemic patients including ‎body mass index and kidney function.‎‎.

Methods

A retrospective cross-sectional design study that was carried out in a private medical center ‎in Palestine. The study included a total of 453 patients with type 2 diabetes. Inclusion criteria ‎included all patients (18 years or older) suffering from type 2 Diabetes mellitus attended the ‎diabetic clinic from the 1st of January 2018, till 30th of December 2018.‎.

Results

A total number of 453 diabetic patients were recruited in the study. Male constituted 48.5% ‎‎(n=220) of the study sample and 51.4% (n=233) were female. Of total 453 diabetic patients, ‎‎38.4% (95% CI, 34%-43%) had anemia. The results of statistical modeling showed that female ‎gender (AOR 18.5; 95% CI 9.35-21.97), presence of hypertension (AOR 2.11; 95% CI 1.98- ‎‎4.25), high BMI (AOR 1.101; 95% CI 1.045-1.159), high Serum Creatinine (AOR 1.72; 95% ‎CI 1.22-2.13), high BUN level (AOR 1.22; 95% CI 1.145-1.301) and low e-GFR (AOR ‎‎0.571; 95% CI 0.271-0.872) are strong determents of anemia in type 2 diabetic patients.‎.

Conclusion

The results of the current study revealed a high prevalence of Anemia among type 2 diabetes ‎Mellitus patients. A significant association was reported between Anemia, kidney functions and ‎body mass index.‎.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers for adults with early (stage 1 to 3) non-diabetic chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a long-term condition that occurs as a result of damage to the kidneys. Early recognition of CKD is becoming increasingly common due to widespread laboratory estimated glomerular filtration rate (eGFR) reporting, raised clinical awareness, and international adoption of the Kidney Disease Improving Global Outcomes (KDIGO) classifications. Early recognition and management of CKD affords the opportunity to prepare for progressive kidney impairment and impending kidney replacement therapy and for intervention to reduce the risk of progression and cardiovascular disease. Angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) are two classes of antihypertensive drugs that act on the renin-angiotensin-aldosterone system. Beneficial effects of ACEi and ARB on kidney outcomes and survival in people with a wide range of severity of kidney impairment have been reported; however, their effectiveness in the subgroup of people with early CKD (stage 1 to 3) is less certain. This is an update of a review that was last published in 2011.

OBJECTIVES

To evaluate the benefits and harms of ACEi and ARB or both in the management of people with early (stage 1 to 3) CKD who do not have diabetes mellitus (DM).

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 6 July 2023 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and Embase, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials (RCTs) reporting the effect of ACEi or ARB in people with early (stage 1 to 3) CKD who did not have DM were selected for inclusion. Only studies of at least four weeks duration were selected. Authors independently assessed the retrieved titles and abstracts and, where necessary, the full text to determine which satisfied the inclusion criteria.

DATA COLLECTION AND ANALYSIS

Data extraction was carried out by two authors independently, using a standard data extraction form. The methodological quality of included studies was assessed using the Cochrane risk of bias tool. Data entry was carried out by one author and cross-checked by another. When more than one study reported similar outcomes, data were pooled using the random-effects model. Heterogeneity was analysed using a Chi² test and the I² test. Results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach MAIN RESULTS: Six studies randomising 9379 participants with CKD stages 1 to 3 (without DM) met our inclusion criteria. Participants were adults with hypertension; 79% were male from China, Europe, Japan, and the USA. Treatment periods ranged from 12 weeks to three years. Overall, studies were judged to be at unclear or high risk of bias across all domains, and the quality of the evidence was poor, with GRADE rated as low or very low certainty. In low certainty evidence, ACEi (benazepril 10 mg or trandolapril 2 mg) compared to placebo may make little or no difference to death (any cause) (2 studies, 8873 participants): RR 2.00, 95% CI 0.26 to 15.37; I² = 76%), total cardiovascular events (2 studies, 8873 participants): RR 0.97, 95% CI 0.90 to 1.05; I² = 0%), cardiovascular-related death (2 studies, 8873 participants): RR 1.73, 95% CI 0.26 to 11.66; I² = 54%), stroke (2 studies, 8873 participants): RR 0.76, 95% CI 0.56 to 1.03; I² = 0%), myocardial infarction (2 studies, 8873 participants): RR 1.00, 95% CI 0.84 to 1.20; I² = 0%), and adverse events (2 studies, 8873 participants): RR 1.33, 95% CI 1.26 to 1.41; I² = 0%). It is uncertain whether ACEi (benazepril 10 mg or trandolapril 2 mg) compared to placebo reduces congestive heart failure (1 study, 8290 participants): RR 0.75, 95% CI 0.59 to 0.95) or transient ischaemic attack (1 study, 583 participants): RR 0.94, 95% CI 0.06 to 15.01; I² = 0%) because the certainty of the evidence is very low. It is uncertain whether ARB (losartan 50 mg) compared to placebo (1 study, 226 participants) reduces: death (any-cause) (no events), adverse events (RR 19.34, 95% CI 1.14 to 328.30), eGFR rate of decline (MD 5.00 mL/min/1.73 m2, 95% CI 3.03 to 6.97), presence of proteinuria (MD -0.65 g/24 hours, 95% CI -0.78 to -0.52), systolic blood pressure (MD -0.80 mm Hg, 95% CI -3.89 to 2.29), or diastolic blood pressure (MD -1.10 mm Hg, 95% CI -3.29 to 1.09) because the certainty of the evidence is very low. It is uncertain whether ACEi (enalapril 20 mg, perindopril 2 mg or trandolapril 1 mg) compared to ARB (olmesartan 20 mg, losartan 25 mg or candesartan 4 mg) (1 study, 26 participants) reduces: proteinuria (MD -0.40, 95% CI -0.60 to -0.20), systolic blood pressure (MD -3.00 mm Hg, 95% CI -6.08 to 0.08) or diastolic blood pressure (MD -1.00 mm Hg, 95% CI -3.31 to 1.31) because the certainty of the evidence is very low.

AUTHORS' CONCLUSIONS

There is currently insufficient evidence to determine the effectiveness of ACEi or ARB in patients with stage 1 to 3 CKD who do not have DM. The available evidence is overall of very low certainty and high risk of bias. We have identified an area of large uncertainty for a group of patients who account for most of those diagnosed as having CKD.

Phase angle and extracellular water-to-total body water ratio estimated by bioelectrical impedance analysis are associated with levels of hemoglobin and hematocrit in patients with diabetes

Background

Anemia is one of the common complications of diabetes and is associated with mortality. Phase angle (PhA), ratio of extracellular water to total body water (ECW/TBW) and skeletal muscle mass index (SMI) estimated by bioelectrical impedance analysis (BIA) have been used as prognostic indicators for various chronic diseases and frailty. We aimed to clarify the clinical significance of PhA, ECW/TBW and SMI for anemia in patients with diabetes.

Materials and methods

The values of PhA, ECW/TBW and SMI were estimated by a portable BIA device and blood samples were collected in 371 Japanese patients with diabetes. The relationships of PhA, ECW/TBW and SMI with hemoglobin (Hgb) and hematocrit (Hct) were statistically evaluated.

Results

In simple linear regression analysis, PhA and SMI were positively correlated with Hgb and Hct levels in total subjects, male subjects and female subjects. In contrast, ECW/TBW was negatively correlated with Hgb and Hct levels regardless of sex. Multivariate regression analysis showed that both PhA and ECW/TBW but not SMI independently contributed to Hgb and Hct levels after adjustment of clinical confounding factors in both males and females.

Conclusions

PhA and ECW/TBW but not SMI were associated with levels of Hgb and Hct in patients with diabetes. Therefore, aberrant values of PhA and ECW/TBW suggest a risk of anemia in diabetic patients.

Beauty and the beast: host microRNA-155 versus SARS-CoV-2

Severe acute respiratory coronavirus 2 (SARS-CoV-2) infection in the young and healthy usually results in an asymptomatic or mild viral syndrome, possibly through an erythropoietin (EPO)-dependent, protective evolutionary landscape. In the old and in the presence of co-morbidities, however, a potentially lethal coronavirus disease 2019 (COVID-19) cytokine storm, through unrestrained renin-angiotensin aldosterone system (RAAS) hyperactivity, has been described. Multifunctional microRNA-155 (miR-155) elevation in malaria, dengue virus (DENV), the thalassemias, and SARS-CoV-1/2, plays critical antiviral and cardiovascular roles through its targeted translational repression of over 140 genes. In the present review, we propose a plausible miR-155-dependent mechanism whereby the translational repression of AGRT1, Arginase-2 and Ets-1, reshapes RAAS towards Angiotensin II (Ang II) type 2 (AT2R)-mediated balanced, tolerable, and SARS-CoV-2-protective cardiovascular phenotypes. In addition, it enhances EPO secretion and endothelial nitric oxide synthase activation and substrate availability, and negates proinflammatory Ang II effects. Disrupted miR-155 repression of AT1R + 1166C-allele, significantly associated with adverse cardiovascular and COVID-19 outcomes, manifests its decisive role in RAAS modulation. BACH1 and SOCS1 repression creates an anti-inflammatory and cytoprotective milieu, robustly inducing antiviral interferons. MiR-155 dysregulation in the elderly, and in comorbidities, allows unimpeded RAAS hyperactivity to progress towards a particularly aggressive COVID-19 course. Elevated miR-155 in thalassemia plausibly engenders a favorable cardiovascular profile and protection against malaria, DENV, and SARS-CoV-2. MiR-155 modulating pharmaceutical approaches could offer novel therapeutic options in COVID-19.

Effects of Angiotensin II on Erythropoietin Production in the Kidney and Liver

The kidney is a main site of erythropoietin production in the body. We developed a new method for the detection of Epo protein by deglycosylation-coupled Western blotting. Detection of deglycosylated Epo enables the examination of small changes in Epo production. Using this method, we investigated the effects of angiotensin II (ATII) on Epo production in the kidney. ATII stimulated the plasma Epo concentration; Epo, HIF2α, and PHD2 mRNA expression in nephron segments in the renal cortex and outer medulla; and Epo protein expression in the renal cortex. In situ hybridization and immunohistochemistry revealed that ATII stimulates Epo mRNA and protein expression not only in proximal tubules but also in collecting ducts, especially in intercalated cells. These data support the regulation of Epo production in the kidney by the renin–angiotensin–aldosterone system (RAS).

Discontinuation of the renin-angiotensin system inhibitors improves erythropoiesis in patients with lower-risk myelodysplastic syndromes

Renin–angiotensin system (RAS) blockade by angiotensin-converting enzyme inhibitors (ACEis) or angiotensin-receptor blockers (ARBs) has been related to anemia in various situations. We aimed to investigate whether discontinuation of RAS inhibitors improves erythropoiesis in patients with lower-risk myelodysplastic syndromes (LR-MDSs). Seventy-four patients with LR-MDS were divided into three groups matched for gender and age. Group A consisted of 20 hypertensive patients who discontinued RAS inhibitors and received alternative medications. Group B consisted of 26 patients who continued to receive ACEi/ARB and Group C included 28 patients (50% hypertensive) never exposed to ACEi/ARB. Half of the patients in each group were under treatment with recombinant human erythropoietin (rHuEPO). Data were collected at baseline and after 3, 6 and 12 months. Group A showed a significant increase in hemoglobin from 10.4 ± 1g/dL at baseline to 12.6 ± 1.2 g/dL after 12 months (p = 0.035) and in hematocrit (31.4 ± 3% versus 37.9 ± 4%, p = 0.002). Incident anemia decreased from 100% at baseline to 60% at 12 months (p = 0.043) despite a concomitant dose reduction in rHuEPO by 18% (p = 0.035). No changes in hemoglobin and hematocrit were observed in both Group B and Group C. In the subset of patients not treated with rHuEPO, improvement of erythropoiesis was found only in Group A, as measured by changes in hemoglobin (11.5 ± 1 g/dL versus 12.4 ± 1.3 g/dL, p = 0.041) and hematocrit (34.5 ± 3% versus 37.1 ± 4%, p = 0.038) after 12 months. In contrast, Group B and Group C decreased hemoglobin and hematocrit after 12 months (p < 0.05). In conclusion, discontinuation of ACEi/ARB in LR-MDS patients is followed by a significant recovery of erythropoiesis after 12 months.

Inhibition of the renin-angiotensin system in the cardiorenal syndrome with anaemia: a double-edged sword

: The term 'cardiorenal syndrome' (CRS) was introduced to describe problems related to the simultaneous existence of heart and renal insufficiency. The prevalence of anaemia in CRS is high and increases the risk of hospitalizations and death. Renin-angiotensin system (RAS) inhibition is the cornerstone therapy in cardiovascular and renal medicine. As angiotensin II regulates both glomerular filtration rate (GFR) and erythropoiesis, RAS inhibition can further deteriorate renal function and lower hematocrit or cause anaemia in patients with heart failure. The aim of this review is to explore the relationship among CRS, anemia and administration of angiotensin-converting enzyme inhibitor (ACEi) or angiotensin receptor blocker (ARB) and summarize the evidence suggesting that RAS inhibition may be considered an iatrogenic cause of deterioration of CRS with anemia. It should be emphasized however, that RAS inhibition reduces mortality in both groups with and without worsening of renal function, and therefore, no patient with CRS should be denied an ACEi or ARB trial without careful evaluation.

Ethnic prevalence of anemia and predictors of anemia among chronic kidney disease patients at a tertiary hospital in Johannesburg, South Africa

INTRODUCTION

Anemia is a complication of chronic kidney disease (CKD) that can greatly impact on its prognosis. However, the risk factors for anemia, including the influence of ethnicity, are not well established among the CKD population in Johannesburg.

METHODS

This was a cross-sectional study of 353 adult CKD patients attending the renal outpatient clinic of the Charlotte Maxeke Johannesburg Academic Hospital (Johannesburg, South Africa) from June 1, 2016 to December 30, 2016. Sociodemographic and clinical characteristics were obtained using a proforma. Blood samples were collected for serum electrolytes and hematological parameters. Predictors of low hemoglobin and iron deficiency anemia (IDA) were evaluated using multivariable binary logistic regression.

RESULTS

The mean age and prevalence of anemia among the CKD participants were 55.3±15.0 years and 43.18% (95% CI: 38.1%-48.4%), respectively. Blacks had the highest prevalence of anemia (46.9%), while Indians/Asians had the lowest (18.2%). Although the odds of anemia was 3.8-fold higher (odds ratio =3.8, P-value =0.059) among CKD stage V participants as compared to CKD stage I, the relationship between anemia and stages of CKD was non-linear. Diabetes mellitus (odds ratio =2.31, P-value =0.005) had a strong association with anemia among the CKD participants.

CONCLUSION

Almost half of the CKD participants were anemic, and the odds of anemia did not increase linearly with increasing severity of CKD. There was a marked ethnic disparity in anemia prevalence. Our study highlights the need for risk-based management of anemia among CKD patients.

Iron deficiency in chronic kidney disease patients with diabetes mellitus

BACKGROUNDS

Iron deficiency has been studied extensively in patients with chronic kidney disease on hemodialysis therapy. However, few studies looked at iron treatment in the non-dialysis chronic kidney disease population.

METHODS

Five hundred and eighty patients were studied (247 were diabetic persons). Patients were divided into 4 groups: non-diabetic subjects without CKD, non-diabetic ones with GFR < 60 mL/min, diabetic persons without CKD and diabetic ones with GFR < 60 mL/min). Iron deficiency was diagnosed when serum ferritin level was <100 mg/dl. It was defined as diminished iron availability when ferritin was above 100 mg/dl and serum transferrin saturation (TSAT) was <20%.

RESULTS

Anemia was more frequent in the diabetic CKD patients group (52.4%, p < 0.001). Anemia prevalence was also higher in all CKD patients as well as in diabetic patients compared with non-diabetic ones. Iron deficiency was more frequent in diabetic patients. Among CKD diabetic patients the prevalence of iron deficiency was higher than in non-diabetic CKD ones. Diminished iron availability prevalence was higher in non-diabetic patients. Logistic regression analysis showed that only sex and diabetes mellitus were independently associated with iron deficiency.

CONCLUSIONS

Anemia was more common in diabetic CKD patients. Diabetes mellitus was independently associated with iron deficiency. Surprisingly, diminished iron availability was not more frequent in diabetic patients. The physio-pathological mechanisms that could explain these findings remain to be elucidated.

Fludrocortisone stimulates erythropoietin production in the intercalated cells of the collecting ducts

Erythropoietin has been thought to be secreted to plasma soon after the production because of the difficulty of Western blot analysis and immunohistochemistry. We established the new methods of Western blot analysis and immunohistochemistry. Using the new methods, we investigated the effects of aldosterone and fludrocortisone, an analogue of aldosterone on erythropoietin mRNA and protein production by the kidneys. Aldosterone stimulated Epo and HIF2α mRNA expressions in tubule suspensions and microdissected medullary thick ascending limbs and outer medullary collecting ducts. Western blot analysis showed a recombinant erythropoietin at 34-45 kDa and kidney erythropoietin at 36-40 and 42 kDa, both of which shifted to 22 kDa by deglycosylation. Erythropoietin protein expression was observed in the nephrons but not in the interstitial cells in control condition. Fludrocortisone stimulated erythropoietin mRNA and protein expressions in the distal nephrons, particularly in the intercalated cells of the collecting ducts. These data show that erythropoietin is produced by the nephrons by the regulation of renin-angiotensin-aldosterone system and not by the renal interstitial cells in control condition.

A Comparison of the Effect of Enalapril and Metoprolol on Renal Function, Potassium Balance, Lipid Profile, Cardiac Function, Exercise Tolerance and Quality of Life in Hypertensive Dialysis Patients

26 patients with hypertension while on hemodialysis or continuous ambulatory peritoneal dialysis for end-stage renal diseases were treated first with enalapril and then changed to metoprolol. Both drugs were shown to be similarly effective in controlling blood pressure. There was no difference between the two drugs in their effects on renal function, potassium balance, lipid profile, cardiac function, exercise tolerance, and quality of life. Mild worsening of anemia was observed during treatment with enalapril. No serious side effects were reported. Use of enalapril is safe in the treatment of hypertension in dialysis patients.

Effect of calcium channels blockers and inhibitors of the renin-angiotensin system on renal outcomes and mortality in patients suffering from chronic kidney disease: systematic review and meta-analysis

BACKGROUND

The renoprotective effect of inhibitors of renin-angiotensin system (RAS) has been identified through placebo-controlled trials. However, the effect of calcium-channel blockers (CCBs) on renal system is still controversial. Our current meta-analysis includes available evidences to compare the effect of dihydropyridine CCBs and ACEIs or ARBs on renal outcomes and mortality. We also further investigate whether CCBs can be used in combination with inhibitors of RAS to improve the prognosis of patients with chronic kidney disease (CKD).

METHODS AND RESULTS

Electronic databases were searched up to July 2012, for clinical randomized controlled trials, assessing the effect of dihydropyridine CCBs on the incidence of end-stage renal disease (ESRD) and all-cause mortality in contrast to ACEIs or ARBs. Eight clinical trials were included containing 25,647 participants. ESRD showed significantly higher frequency with CCBs therapy compared with ACEIs or ARBs therapy, though blood pressure was decreased similarly in both groups in every trial (OR, 1.25; 95% CI, 1.05-1.48; p = 0.01). In contrast, there was no significant difference in the incidence of all-cause mortality between these two groups, though ACEIs or ARBs exhibited better renoprotective effect compared to CCBs (OR, 0.96; 95% CI, 0.89-1.03; p = 0.24).

CONCLUSIONS

CCBs did not increase all-cause mortality incidence in patients with CKD though they displayed weaker renoprotective, compared to ACEIs or ARBs therapy. Our results suggest the combination of a CCB and an ACEI or ARB should be a preferable antihypertensive therapy in patients with CKD, considering their higher effect in decreasing blood pressure and fewer adverse metabolic problems caused.

Renin-angiotensin system inhibitors linked to anemia: a systematic review and meta-analysis

BACKGROUND

The objective of this meta-analysis was to evaluate the risk of anemia in patients who received renin-angiotensin system (RAS) inhibitors.

METHODS

A literature search was performed using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from inception through November, 2014. Studies that reported relative risks, odd ratios or hazard ratios comparing the anemia risk in patients who received angiotensin-converting-enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) vs. those who did not were included. We performed the prespecified sensitivity analysis including only only studies with confounder adjusted analysis. Pooled risk ratios (RRs) and 95% confidence interval (CI) were calculated using a random-effect, generic inverse variance method.

RESULTS

Seven studies (2 cohort and 5 cross-sectional studies) with 29,061 patients were included in the analysis to assess the risk of anemia and the RAS inhibitors use. The pooled RR of anemia in patients receiving ACEIs was 1.56 (95% CI, 1.40-1.73, I(2) = 17%). When meta-analysis was limited only to studies with confounder adjusted analysis, the pooled RR of anemia in patients using ACEIs was 1.57 (95% CI, 1.43-1.73, I(2) = 0%) The pooled RR of anemia in patients receiving ARBs was 1.60 (95% CI, 1.27-2.00, I(2) = 39%). The meta-analysis of studies with confounder adjusted analysis demonstrated the pooled RR of anemia in patients using ARBs of 1.59 (95% CI, 1.38-1.83, I(2) = 0%).

CONCLUSIONS

Our meta-analysis demonstrates an association between anemia and the use of RAS inhibitors. Hematological parameters should be monitored in patients treated with RAS inhibitors.

Iron deficiency: Prevalence and relation to cardiovascular biomarkers in heart failure outpatients

BACKGROUND

Both iron deficiency (ID) and cardiovascular biomarkers are associated with a poor outcome in heart failure (HF). The relationship between different cardiovascular biomarkers and ID is unknown, and the true prevalence of ID in an outpatient HF clinic is probably overlooked.

OBJECTIVES

To identify the prevalence of ID in a HF clinic and evaluate whether ID is associated with increased plasma concentrations of different cardiovascular biomarkers that carry a poor prognosis.

METHODS

We prospectively included 149 patients with systolic HF referred to an outpatients HF clinic. ID was defined as ferritin<100 μg/L or ferritin 100-300 μg/L and Tranferin-saturation<0.20. Five different cardiovascular biomarkers were analyzed on frozen plasma.

RESULTS

The patients had a median age of 70 (Interquartile range: 64-75) years, 25% were females, 29% were in functional class III-IV and LVEF was 32 (27-39) %. The prevalence of ID was 45% (95%-confidence interval (CI): 37-53%). In multivariate analyses, ID was not associated with plasma concentrations of troponin I, NT-proBNP, MR-proANP, chromogranin A or copeptin (P>0.05 for all) but with plasma concentrations of hs-CRP (odds ratio: 2.03, 95%-CI: 1.02-4.02, P=0.043).

CONCLUSION

ID is frequent in an outpatient HF clinic. ID is not associated with cardiovascular biomarkers after adjustment for traditional confounders. Inflammation, but not neurohormonal activation is associated with ID in systolic HF. Further studies are needed to understand iron metabolism in elderly HF patients.

The sex difference in haemoglobin levels in adults - mechanisms, causes, and consequences

Men and women have different mean haemoglobin levels in health in venous blood - women have mean levels approximately 12% lower than men. A similar sex-related difference in haemoglobin levels in adult animals is found in many species of mammals, birds and reptiles, indicating that it is an important physiological phenomenon. It is probably a direct effect of sex hormones, both oestrogen and androgens, on erythropoiesis. However, since there is no difference in erythropoietin levels between the sexes, this effect most likely takes place in the kidney, rather than in the bone marrow. Oestrogens dilate and androgens constrict the renal microvasculature: dilation and vasoconstriction in vessels below 300 μm in diameter respectively increase and decrease the haematocrit in blood in arterioles, capillaries and venules, altering the oxygen delivery per unit red cell mass, and providing a mechanism for varying the red cell mass without compensatory changes in erythropoiesis.

Effect of angiotensin converting enzyme inhibitors and angiotensin receptor blockers on hemoglobin levels

Background

Angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are widely used in the management of congestive heart failure (CHF), diabetes mellitus (DM) and hypertension (HTN). Use of these agents is reported to cause anemia.

Methods

We examined the association between standard care use of ACEI or ARB and subsequent change in hemoglobin (Hgb) in a population of 701 adult primary care patients with DM, CHF and/or HTN. Data analysis was conducted to adjust for baseline differences between the treatment groups.

Results

After adjusting for differences in covariates at baseline between the subjects who were prescribed ACEI (N = 519) and ARB (N = 182), as well as the associated odds of being prescribed ARB, the ACEIs were associated with lower mean Hgb [0.18 (0.02, 0.34) g/dL, p = 0.02] at follow up relative to ARBs. However, patients with CHF experienced an increase in Hgb while on treatment (0.42 g/dL), especially those treated with ACEIs (0.56 g/dL). Chronic kidney disease at baseline was not associated with a significant decrease in Hgb in either treatment group.

Conclusions

Since ACEIs and ARBs are most frequently used in patients who are vulnerable to complications from anemia, such as patients with CHF, HTN and DM, these findings may be useful to clinicians in selecting medications and monitoring patients for the adverse effects of treatment.

Introduction of angiotensin-converting enzyme inhibitors induces a fall in hemoglobin levels in elderly patients hospitalized with heart failure: a cohort study

BACKGROUND AND AIMS

Although the use of angiotensin-converting enzyme-inhibitors (ACE-I) is a cornerstone of treatment for heart failure (HF), these agents have been associated with decreasing hemoglobin levels in several settings. The aim of this study was to assess whether ACE-I are associated with decreasing hemoglobin in older subjects, and whether this effect is enhanced among patients with HF.

METHODS

The association between starting use of ACE-I and variations in hemoglobin levels was investigated in 10,354 hospitalized elderly, 1217 of whom had a verified diagnosis of HF, enrolled in a multicenter pharmacoepidemiology survey.

RESULTS

According to Cox regression analysis, the relative risk of a decrease in hemoglobin levels >0.5 g/dL associated with starting treatment with ACE-I was 1.12 (95% CI 0.98-1.26, p=0.081) among participants without HF, and 1.98 (95% CI 1.54-2.53, p<0.0001) among patients with HF, after adjusting for potential confounders. Analysis of the interaction term in Cox regression confirmed that the association between use of ACE-I and hemoglobin decrease varied according to diagnosis of HF (p=0.003) and older age (p=0.029).

CONCLUSIONS

Starting treatment with ACE-I is independently associated with increased risk of hemoglobin decrease among older hospitalized patients with HF. Hemoglobin levels should be monitored in older subjects who start ACE-I.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers for adults with early (stage 1 to 3) non-diabetic chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a long term condition that occurs as a result of damage to the kidneys. Early recognition of CKD is becoming increasingly common due to widespread laboratory estimated glomerular filtration rate (eGFR) reporting, raised clinical awareness, and international adoption of Kidney Disease Outcomes Quality Initiative (K/DOQI) classification. Early recognition and management of CKD affords the opportunity not only to prepare for progressive kidney impairment and impending renal replacement therapy, but also for intervening to reduce the risk of progression and cardiovascular disease. Angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) are two classes of antihypertensive drugs that act on the renin-angiotensin-aldosterone system. Beneficial effects of ACEi and ARB on renal outcomes and survival in people with a wide range of severity of renal impairment have been reported; however, their effectiveness in the subgroup of people with early CKD (stage 1 to 3) is less certain.

OBJECTIVES

This review aimed to evaluate the benefits and harms of ACEi and ARB or both in the management of people with early (stage 1 to 3) CKD who do not have diabetes mellitus.

SEARCH STRATEGY

In March 2010 we searched The Cochrane Library, including The Cochrane Renal Group's specialised register and The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. Reference lists of review articles and relevant studies were also checked. The search was conducted using the optimally sensitive strategy developed by the Cochrane Collaboration for the identification of randomised controlled trials (RCTs) with input from an expert in trial search strategy.

SELECTION CRITERIA

All RCTs reporting the effect of ACEi or ARB in people with early (stage 1 to 3) CKD who did not have diabetes mellitus were selected for inclusion. Only studies of at least four weeks duration were selected. Authors, working in teams of two, independently assessed the retrieved titles and abstracts, and whenever necessary the full text of these studies were screened to determine which studies satisfied the inclusion criteria.

DATA COLLECTION AND ANALYSIS

Data extraction was carried out by two authors, independently, using a standard data extraction form and cross checked by two other authors. Methodological quality of included studies was assessed using the Cochrane risk of bias tool. Data entry was carried out by one author and cross checked by another author. When more than one study reported similar outcomes, data were pooled using the random-effects model, but a fixed-effect model was also analysed to ensure the robustness of the model chosen and to check susceptibility to outliers. Heterogeneity was analysed using a Chi² test on N-1 degrees of freedom, with an alpha of 0.05 used for statistical significance and with the I² test. Where data permitted, subgroup analysis was used to explore possible sources of heterogeneity. The quality of the evidence was analysed.

MAIN RESULTS

Four RCTs enrolling 2177 participants met our inclusion criteria. Of these, three compared ACEi with placebo and one compared ACEi with ARB. Two studies had an overall low risk of bias, and the other two were considered to be at moderate to high risk of bias. Low to moderate quality of evidence (from two studies representing 1906 patients) suggested that ACEi had no impact on all-cause mortality (RR 1.80, 95% CI 0.17 to 19.27, P = 0.63) or cardiovascular events (RR 0.87, 95% CI 0.66 to 1.14, P = 0.31) in people with stage 3 CKD. For all-cause mortality, there was substantial heterogeneity in the results. One study (quality assessment: low risk of bias) reported no difference in the risk of end-stage kidney disease in those with an eGFR > 45 mL/min/1.74 m² treated with ACEi versus placebo (RR 1.00, 95% CI 0.09 to 1.11, P = 0.99). The (high risk of bias) study that compared ACEi with ARB reported little difference in effect between the treatments when urinary protein, blood pressure or creatinine clearance were compared. No published studies comparing ARB with placebo or ACEi and ARB with placebo were identified.

AUTHORS' CONCLUSIONS

Our review demonstrated that there is currently insufficient evidence to determine the effectiveness of ACEi or ARB in patients with stage 1 to 3 CKD who do not have diabetes mellitus. We have identified an area of significant uncertainty for a group of patients who account for most of those labelled as having CKD.

Role of residual renal function in phosphate control and anemia management in chronic hemodialysis patients

BACKGROUND AND OBJECTIVES

There is increasing awareness that residual renal function (RRF) has beneficial effects in hemodialysis (HD) patients. The aim of this study was to investigate the role of RRF, expressed as GFR, in phosphate and anemia management in chronic HD patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Baseline data of 552 consecutive patients from the Convective Transport Study (CONTRAST) were analyzed. Patients with a urinary output≥100 ml/24 h (n=295) were categorized in tertiles on the basis of degree of GFR and compared with anuric patients (i.e., urinary output<100 ml/24 h, n=274). Relations between GFR and serum phosphate and erythropoiesis-stimulating agent (ESA) index (weekly ESA dose per kg body weight divided by hematocrit) were analyzed with multivariable regression models.

RESULTS

Phosphate levels were between 3.5 and 5.5 mg/dl in 68% of patients in the upper tertile (GFR>4.13 ml/min per 1.73 m2), as compared with 46% in anuric patients despite lower prescription of phosphate-binding agents. Mean hemoglobin levels were 11.9±1.2 g/dl with no differences between the GFR categories. The ESA index was 31% lower in patients in the upper tertile as compared with anuric patients. After adjustments for patient characteristics, patients in the upper tertile had significantly lower serum phosphate levels and ESA index as compared with anuric patients.

CONCLUSIONS

This study suggests a strong relation between RRF and improved phosphate and anemia control in HD patients. Efforts to preserve RRF in HD patients could improve outcomes and should be encouraged.

The role of the renin-angiotensin system in the regulation of erythropoiesis

The renin-angiotensin system is the major regulator of blood pressure by virtue of controlling vascular resistance and plasma volume. Much less recognition exists for the role of the renin-angiotensin system in regulating erythropoiesis, a biological function critical for oxygen delivery to tissues. In this review, we present evidence that angiotensin II (Ang II) is a physiologically important regulator of erythropoiesis with 2 key actions. First, Ang II is a growth factor of erythroid progenitors and, in cooperation with erythropoietin, increases red blood cell mass. Second, Ang II acts as an erythropoietin secretagogue to maintain increased erythropoietin levels despite increments in hematocrit. Among a multitude of physiologic and pathophysiologic implications, these lines of evidence provide an explanation for the effect of angiotensin-converting enzyme inhibitors and Ang II type 1 receptor blockers to decrease hematocrit or cause anemia in various clinical conditions.

Erythropoietin is reduced by combination of diuretic therapy and RAAS blockade in proteinuric renal patients with preserved renal function

BACKGROUND

Renin-angiotensin-aldosterone system (RAAS) blockade improves prognosis in renal patients, but usually requires diuretic co-treatment. RAAS blockade can decrease erythropoietin (EPO) and/or haemoglobin (Hb) levels. Diuretics decrease EPO in rodents, but their effect on EPO and Hb in humans is unknown.

METHODS

Proteinuric renal patients with preserved renal function were treated during 6-week periods with placebo, losartan 100 mg/day (LOS) and LOS plus hydrochlorothiazide 25 mg/day (LOS/HCT), in random order.

RESULTS

Hb was inversely related to proteinuria, and EPO levels were inappropriately low in relation to Hb. Hb was lowered by LOS with and without HCT. EPO was decreased by LOS/HCT, but not by LOS.

CONCLUSIONS

EPO and Hb are reduced by HCT added to LOS in proteinuric renal patients with preserved renal function. We hypothesize that EPO reduction by HCT is caused by a decrease in renal oxygen requirement, which is the main stimulus for EPO production, due to the inhibition of active tubular sodium reabsorption. Further studies should explore the exact mechanism of this phenomenon and its clinical impact.

Timing of onset of CKD-related metabolic complications

Chronic kidney disease (CKD) guidelines recommend evaluating patients with GFR <60 ml/min per 1.73 m(2) for complications, but little evidence supports the use of a single GFR threshold for all metabolic disorders. We used data from the NephroTest cohort, including 1038 adult patients who had stages 2 through 5 CKD and were not on dialysis, to study the occurrence of metabolic complications. GFR was measured using renal clearance of (51)Cr-EDTA (mGFR) and estimated using two equations derived from the Modification of Diet in Renal Disease study. As mGFR decreased from 60 to 90 to <20 ml/min per 1.73 m(2), the prevalence of hyperparathyroidism increased from 17 to 85%, anemia from 8 to 41%, hyperphosphatemia from 1 to 30%, metabolic acidosis from 2 to 39%, and hyperkalemia from 2 to 42%. Factors most strongly associated with metabolic complications, independent of mGFR, were younger age for acidosis and hyperphosphatemia, presence of diabetes for acidosis, diabetic kidney disease for anemia, and both male gender and the use of inhibitors of the renin-angiotensin system for hyperkalemia. mGFR thresholds for detecting complications with 90% sensitivity were 50, 44, 40, 39, and 37 ml/min per 1.73 m(2) for hyperparathyroidism, anemia, acidosis, hyperkalemia, and hyperphosphatemia, respectively. Analysis using estimated GFR produced similar results. In summary, this study describes the onset of CKD-related complications at different levels of GFR; anemia and hyperparathyroidism occur earlier than acidosis, hyperkalemia, and hyperphosphatemia.

Association between erythropoietin requirements and antihypertensive agents

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACI) and angiotensin II receptor blockers (ARB) have been reported to increase recombinant human erythropoietin (rHuEPO) requirements. We performed a cross-sectional study to investigate an association of antihypertensive agents including these two with the rHuEPO dose in chronic hemodialysis patients.

METHODS

We studied 625 patients undergoing hemodialysis therapy in 11 dialysis units. The association between the rHuEPO dose and antihypertensive agents was statistically analyzed.

RESULTS

The mean hemoglobin (Hb) level and rHuEPO dose corrected by body weight were 10.5 g/dl and 95.2 U/kg/week, respectively. When the patients were subdivided into four groups according to the number of prescribed antihypertensive agents (G-0, G-1, G-2, and G-3; patients prescribed with no medication, 1, 2, and >3 drugs, respectively), a significantly low dose of rHuEPO was observed in G-0 compared to the other groups. Unpaired t test showed a higher dose of rHuEPO in the presence of ARB, alpha-blockers, or calcium channel blockers (CCB). The rHuEPO dose was higher in the elderly, in females, and in patients with diabetes or hypertension. In multiple regression analysis, age, sex, rHuEPO dose, serum albumin level, and duration of dialysis therapy but not antihypertensive drugs were independent factors for the Hb level. In contrast, the rHuEPO dose was significantly associated with a low level of Hb, age, females, and CCB use. However, since CCB use was strongly associated not only with rHuEPO dose but also with systolic blood pressure and the use of alpha-blockers and ARB, these findings might be caused by erythropoietin (EPO)-induced hypertension.

CONCLUSION

There was an association between the number of antihypertensive agents and rHuEPO dose in chronic hemodialysis patients. However, no significant relation was indicated between ARB/ACI use and EPO requirements.

Effects of the Renin-Angiotensin system blockade on hemoglobin levels in type 2 diabetic patients with chronic kidney disease

BACKGROUND

Treatment with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin-receptor blockers (ARBs) may be associated with reduced erythrocyte production in several clinical settings; however, these effects have not been determined in diabetic patients with chronic kidney disease (CKD), a high-risk population for anemia. We conducted a retrospective study to assess the effects of ACEIs and ARBs on hemoglobin levels in Japanese adults with type 2 diabetes and CKD.

METHODS

Diabetic patients with an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2), who filled a prescription for an ACEI or ARB, were included. Changes in hemoglobin levels after initiating treatment with an ACEI or ARB were compared using multivariate analysis of covariance (ANCOVA) and propensity-score matching to minimize the bias.

RESULTS

A total of 201 diabetic patients, 77 treated with an ACEI and 124 treated with an ARB, fulfilled study criteria and constituted the retrospective cohort. Mean (+/-s.e.) change in hemoglobin (adjusted for covariates) was greater for patients treated with ARBs (-0.43 +/- 0.08 g/dl) than patients treated with ACEIs (-0.11 +/- 0.11 g/dl, P = 0.025) by ANCOVA. In the propensity-score cohort analysis of 57 pairs of ACEI/ARB-treated patients, a significant decrease in hemoglobin was observed in patients treated with an ARBs (-0.54 +/- 1.02 g/dl (mean +/- s.d.), P < 0.001), but not in patients treated with an ACEIs (-0.14 +/- 0.98 g/dl, P = 0.294).

CONCLUSIONS

Treatment with an ARB, but not ACEI, may be associated with a modest decrease in hemoglobin levels in diabetic patients with CKD.

Impact of diabetes on haemoglobin levels in renal disease

AIMS/HYPOTHESIS

Anaemia is a common complication of renal impairment. It has been suggested that renal failure secondary to diabetes is associated with more severe anaemia, but this has not been clearly substantiated in the published literature. To clarify this, we undertook a single centre, retrospective study to identify the impact of diabetes on anaemia associated with renal impairment.

MATERIALS AND METHODS

Information on clinical, biochemical and haematological parameters of 2,052 stable ambulatory patients attending a single tertiary referral renal unit was collected. The impact of diabetic kidney disease on haemoglobin levels at all degrees of renal impairment was studied by comparison with patients with non-diabetic kidney disease after correcting for other commonly associated variables that influence anaemia in patients with renal impairment.

RESULTS

Linear regression analysis showed lower haemoglobin in patients with diabetic kidney disease (p < 0.01). At chronic kidney disease (CKD) stages 3, 4 and 5, mean haemoglobin levels in patients with diabetic kidney disease compared with those in patients with non-diabetic kidney disease were 129.5 vs 136.9 g/l (p < 0.001), 120.5 vs 126.9 g/l (p < 0.001) and 107.1 vs 115.9 g/l (p < 0.01), respectively. At CKD stage 4 and 5 the two groups were comparable for ferritin, plasma intact parathyroid hormone levels, ACE inhibitor use and length of follow-up by a nephrologist.

CONCLUSIONS/INTERPRETATION

Diabetic kidney disease is associated with lower haemoglobin in comparison with non-diabetic kidney disease, especially at GFR <60 ml/min.

Potential side effects of renin inhibitors – mechanisms based on comparison with other renin–angiotensin blockers

Angiotensin (Ang) II plays important roles in the development of hypertension and cardiovascular and renal injury. Pharmaceutical approaches to block its activity led to the development of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Numerous trials have documented their efficacy in controlling blood pressure, minimising left ventricular remodelling, preventing progression to heart failure, ameliorating proteinuria and retarding renal disease progression. Although they are considered safe in general, there remain concerns about the potential for adverse events in certain target populations. Recently, several novel, low molecular weight renin inhibitors without the extended peptide-like backbone of previous renin inhibitors were developed with favourable pharmacokinetic properties. They have been shown to successfully reduce Ang II levels in normal volunteers and to lower blood pressure in patients with mild-to-moderate hypertension. In this review, the authors summarise current knowledge about these renin inhibitors.

Angiotensin-converting enzyme inhibitors slow recovery from anemia following cardiac surgery

OBJECTIVES

Angiotensin-converting enzyme (ACE) inhibitors, which are frequently administered in patients with heart disease, have a known inhibitory effect on erythropoiesis. The aim of this study was to detect whether early ACE inhibitor administration slows recovery from anemia following recent cardiac surgery.

METHODS AND RESULTS

Forty male patients with anemia (hemoglobin < 12 g/dL) an average of 9 days after cardiac surgery were randomized to receive enalapril (ACE inhibitor group) or not. All of the patients received ferrous sulfate, 525 mg, in addition to standard therapy. Patients with anemia due to other causes were excluded. Blood samples were obtained at baseline, and after 8 days, 16 days, and 60 days. A 6-min walking test and echocardioscan were performed at baseline, and after 16 days and 60 days of treatment, and a chest radiograph was obtained at baseline and after 60 days. The ACE inhibitor group showed a statistically significant lower increase in hemoglobin and RBC values. The peak between-group differences of 1 g/dL of hemoglobin (p = 0.012) and 444 RBCs per milliliter (p = 0.017) were observed on day 16.

CONCLUSIONS

Early enalapril maleate administration in anemic patients after heart surgery significantly inhibits erythropoiesis. This unfavorable effect on anemia should be considered when prescribing ACE inhibitors for such patients.

HEMATOLOGY: ISSUES IN THE DIALYSIS PATIENT: Erythropoietin Resistance in the Treatment of the Anemia of Chronic Renal Failure

Resistance to erythropoietin therapy is a common complication of the modern management of anemia in chronic kidney disease. Iron deficiency, deficiency of other nutrients, toxins, infections, and inadequate dialysis account for the vast majority of episodes of such resistance.

Higher prevalence of anemia with diabetes mellitus in moderate kidney insufficiency: The Kidney Early Evaluation Program

BACKGROUND

The Kidney Early Evaluation Program (KEEP 2.0) cross-sectional, community-based study, targeted individuals at increased risk for kidney disease and measured blood glucose, creatinine, and hemoglobin.

METHODS

KEEP 2.0 screening data were used to determine the prevalence of anemia by level of kidney function and diabetes status. Estimated glomerular filtration rate (EGFR) was calculated using serum creatinine values, and categorized as > or =90, 60-89, 30-59 and <30 mL/min/1.73 m(2). Anemia was defined as hemoglobin <12 g/dL in men and in women aged >50 years, and <11 g/dL in women < or =50 years. Diabetes was defined as participant-reported diagnosis, fasting glucose >125 mg/dL, or nonfasting glucose >200 mg/dL.

RESULTS

Data were available on 5380 participants screened from August 2000 through December 2001. Diabetes was present in 26.9% of participants, and anemia in 7.7%; 15.9% of participants had at least moderately reduced kidney function (EGFR <60 mL/min/1.73 m(2)). In participants with diabetes, anemia prevalence at the 4 levels of descending EGFR were 8.7%, 7.5%, 22.2%, and 52.4%, compared with 6.9%, 5.0%, 7.9%, and 50.0% in persons without diabetes. In a multivariable model, participants of non-white race/ethnicity, those with diabetes and those with EGFR <30 or 30-59 mL/min/1.73 m(2) had significantly increased odds of anemia. In addition, a significant sex-diabetes interaction was identified; odds of anemia were 4-fold greater in men than women with diabetes relative to sex-matched participants without diabetes.

CONCLUSION

Diabetes was independently correlated with anemia, more so in men than women, and may be linked to premature expression of anemia in persons with moderate reductions in kidney function.

Drug dosing in chronic kidney disease

Patients with chronic kidney disease (CKD) are at high risk for adverse drug reactions and drug-drug interactions. Drug dosing in these patients often proves to be a difficult task. Renal dysfunction-induced changes in human pathophysiology regularly results may alter medication pharmacodynamics and handling. Several pharmacokinetic parameters are adversely affected by CKD, secondary to a reduced oral absorption and glomerular filtration; altered tubular secretion; and reabsorption and changes in intestinal, hepatic, and renal metabolism. In general, drug dosing can be accomplished by multiple methods; however, the most common recommendations are often to reduce the dose or expand the dosing interval, or use both methods simultaneously. Some medications need to be avoided all together in CKD either because of lack of efficacy or increased risk of toxicity. Nevertheless, specific recommendations are available for dosing of certain medications and are an important resource, because most are based on clinical or pharmacokinetic trials.

Enalapril dosage in progressive chronic nephropathy: a randomised, controlled trial

OBJECTIVE

In chronic renal failure, clearance of enalapril is reduced. Hence, a renoprotective effect may be achieved with lower doses than conventionally used. Since marked inter-patient variation in concentrations of enalaprilat has been shown in patients with renal failure despite equivalent dosage of enalapril, a direct comparison of the effect of high versus low plasma concentrations of enalaprilat on the progression of renal failure was undertaken.

METHODS

Forty patients with a median glomerular filtration rate (GFR) of 17 (6-35) ml/min/1.73 m2 were studied in an open-label, randomised trial comparing patients with a high (>50 ng/ml) with patients with a low (<10 ng/ml) target trough plasma concentration of enalaprilat. The dose of enalapril was titrated accordingly. The patients were followed for 12 months or until they needed renal replacement therapy. GFR was measured at 3-month intervals by the plasma clearance of 51Cr-EDTA, and the individual rates of progression of renal failure were calculated as the slope of GFR versus time plot.

RESULTS

In the high-concentration group, the median enalaprilat trough concentration was 92.9 ng/ml (21.8-371.0 ng/ml) and in the low-concentration group it was 9.1 ng/ml (2.5-74.8 ng/ml) at 3 months follow-up (P<0.001). The median daily doses of enalapril were 10 mg (2.5-30 mg) and 1.88 mg (1.25-5 mg) in the high and low groups, respectively (P<0.001). In the high-concentration group, the mean+/-SE decline in renal function was 6.1+/-1.5 ml/min/1.73 m2 per year and in the low-concentration group it was 4.3+/-14.4 ml/min/1.73 m2 per year (P=0.48). Five patients in the high-concentration group reached end-stage renal failure whereas none in the low-concentration group did (P=0.04). There were no statistically significant differences in blood pressure level, concomitant antihypertensive therapy or urinary albumin excretion. However, the high-enalaprilat concentration group had an overall higher plasma potassium concentration of 0.42 mmol/l than the low group (P<0.001).

CONCLUSION

In patients with moderate to severe renal insufficiency, a low concentration of enalaprilat afforded the same degree of renoprotection, blood pressure control and minimisation of proteinuria as a high concentration, during 12 months of follow-up. The high-dosage treatment was associated with a more pronounced tendency to hyperkalaemia. Thus, there seems to be no indication for increasing the daily dose of enalapril beyond what achieves adequate blood pressure control in this group of patients.

Angiotensin-converting enzyme inhibitors in the therapy of renal diseases

Renal diseases, especially chronic renal failure (CRF), are common in canine and feline medicine. The renin-angiotensin-aldosterone system (RAAS) plays a pivotal role in these conditions in the development of renal lesions and the progression of kidney dysfunction. Angiotensin-converting enzyme inhibitors (ACEI) are currently considered as the most efficient agents in therapeutic strategies. The benefit of an ACEI treatment can be explained by at least three mechanisms: ACEI limit systemic and glomerular capillary hypertension, have an antiproteinuric effect, and retard the development of glomerulosclerosis and tubulointerstitial lesions. These effects have been studied in dogs and cats, and there is now some evidence to support the recommendation of ACEI therapy in dogs and cats with CRF. Nevertheless the prescription of ACEI in such patients should take into account the potential influence of renal impairment on ACEI disposition, and adverse effects on the renal function itself (especially hypotension and acute reductions in glomerular filtration rate). The risk of drug interaction with diuretics, nonsteroidal anti-inflammatory drugs and anesthetics, should not be overestimated. Furthermore, hypotension may occur in patients on a low sodium diet.

Anemia as a risk factor and therapeutic target in heart failure

Anemia has recently been recognized as an important comorbid condition and potentially novel therapeutic target in patients with heart failure (HF). Anemia is common in HF patients, with a prevalence ranging from 4% to 55% depending on the population studied. Multiple potential mechanisms of interaction exist between anemia and the clinical syndrome of HF, including hemodilution, inflammatory activation, renal insufficiency, and malnutrition. A growing body of literature from observational databases and clinical trials suggests that anemia is an independent risk factor for adverse outcomes in patients with HF. Although preliminary data suggest that treatment of anemia may result in significant symptomatic improvement in HF, aggressive treatment of anemia may also be associated with increased risk of hypertension or thrombosis. Multiple ongoing studies will provide definitive data on the balance of risks and benefits of anemia treatment in chronic HF.

Are hematinic deficiencies the cause of anemia in chronic heart failure?

BACKGROUND

Anemia in chronic heart failure (CHF) is common, varying in prevalence between 14.4% and 55%, and is more frequent in patients with more severe heart failure. Patients with CHF who have anemia have a poorer quality of life, higher hospital admission rates, and reduced exercise tolerance. We explored the relation between hematinic levels and hemoglobin (Hb) levels and exercise tolerance in a group of patients with CHF.

METHODS

We analyzed data from 173 patients with left ventricular systolic dysfunction (LVSD), 123 patients with symptoms of heart failure, but preserved left ventricular (LV) systolic function ("diastolic dysfunction"), and 58 control subjects of similar age. Each underwent echocardiography, a 6-minute walk test, and blood tests for renal function and Hb and hematinic levels (vitamin B12, iron, and folate). We classified patients as having no anemia (Hb level >12.5 g/dL), mild anemia (Hb level from 11.5-12.5 g/dL), or moderate anemia (Hb level <11.5 g/dL).

RESULTS

Of patients with LVSD, 16% had moderate anemia and 19% had mild anemia. Of patients with preserved LV function, 16% had moderate anemia and 17% had mild anemia. Four control subjects had a Hb level <12.5 g/dL. Of all patients, 6% were vitamin B12 deficient, 13% were iron deficient, and 8% were folate deficient. There was no difference between patients with LVSD and the diastolic dysfunction group. In patients with LVSDS, the average Hb level was lower in New York Heart Association class III than classes II and I. The distance walked in 6 minutes correlated with Hb level in both groups of patients with CHF (r = 0.29; P <.0001). Patients with anemia achieved a lower pVO2 (15.0 [2.3] vs 19.5 [4.4], P <.05). Peak oxygen consumption correlated with Hb level (r = 0.21, P <.05) in the patients, but not in the control subjects. In patients with anemia, the mean creatinine level was higher than in patients with a Hb level >12.5 g/dL, but there was no clear relationship with simple regression. Hematocrit level and mean corpuscular volume were not different in the patients with diastolic dysfunction, patients with LV dysfunction, or the control subjects. Hematocrit levels were not influenced by diuretic dose. Patients with anemia were not more likely to be hematinic deficient than patients without anemia.

CONCLUSIONS

Patients with symptoms and signs of CHF have a high prevalence of anemia (34%) whether they have LV dysfunction or diastolic dysfunction, but few patients have hematinic deficiency. Hemoglobin levels correlate with subjective and objective measures of severity and renal function.

Posttransplant erythrocytosis

Posttransplant erythrocytosis (PTE) is defined as a persistently elevated hematocrit to a level greater than 51% after renal transplantation. It occurs in 10% to 15% of graft recipients and usually develops 8 to 24 months after engraftment. Spontaneous remission of established PTE is observed in one fourth of the patients within 2 years from onset, whereas in the remaining three fourths it persists for several years, only to remit after loss of renal function from rejection. Predisposing factors include male gender, retention of native kidneys, smoking, transplant renal artery stenosis, adequate erythropoiesis prior to transplantation, and rejection-free course with well-functioning renal graft. Just as in other forms of erythrocytosis, a substantial number (approximately 60%) of patients with PTE experience malaise, headache, plethora, lethargy, and dizziness. Thromboembolic events occur in 10% to 30% of the cases; 1% to 2% eventually die of associated complications. Posttransplant erythrocytosis results from the combined trophic effect of multiple and interrelated erythropoietic factors. Among them, endogenous erythropoietin appears to play the central role. Persistent erythropoietin secretion from the diseased and chronically ischemic native kidneys does not conform to the normal feedback regulation, thereby establishing a form of "tertiary hypererythropoietinemia." However, erythropoietin levels in most PTE patients still remain within the "normal range," indicating that erythrocytosis finally ensues by the contributory action of additional growth factors on erythroid progenitors, such as angiotensin II, androgens, and insulin-like growth factor 1 (IGF-1). Inactivation of the renin-angiotensin system (RAS) by an angiotensin-converting enzyme (ACE) inhibitor, or an angiotensin II type 1 AT1 receptor blocker represents the most effective, safe, and well-tolerated therapeutic modality.

Why is erythropoietin made in the kidney? The kidney functions as a 'critmeter' to regulate the hematocrit

The normal hematocrit is not a random number, but one that maximizes oxygen delivery. While the feedback loop wherein tissue oxygen pressure determines the production of erythropoietin, which further drives the production of red blood cells in the bone marrow, explains how the hematocrit is generated, it does not speak to how the hematocrit is regulated. The regulation of the hematocrit requires the coordination of the plasma volume and the red cell mass. By controlling red cell mass via erythropoietin and plasma volume through excretion of salt and water, the kidney is able to generate the hematocrit. It is hypothesized that the kidney functions as a critmeter by sensing the relative volumes of each component of the blood through the common signal of tissue oxygen tension. The kidney's unique ability to sense ECF volume through tissue oxygen signal allows it to coordinate these two volumes to produce the normal hematocrit. Hence, it may be the kidneys ability to report a measure of ECF volume as a tissue oxygen signal and thus to regulate the hematocrit that establishes it as the logical site of erythropoietin production. The critmeter is proposed to be a functional unit located at the tip of the cortical labyrinth at the juxta-medullary region of the kidney where erythropoietin is made physiologically. Renal vasculature and nephron segment heterogeneity in sodium reabsorption likely provides the anatomical construct to generate the marginal tissue oxygen pressure required to trigger the production of erythropoietin. The balance of oxygen consumption for sodium reabsorption and oxygen delivery is reflected by the tissue oxygen pressure. This balance hence determines RBC mass adjusted to plasma volume. Factors that affect blood supply and sodium reabsorption in a discordant manner may modulate the critmeter, e.g. angiotensin II. The objective of this work is to describe the hypothesis of the kidney's function as a critmeter, including the anatomical and physiological components, and the role of the renin-angiotensin system in modulating erythropoietin. Clinical examples of the dysregulation of the critmeter may be found in the anemia of renal failure and in sports anemia.

Effects of losartan or enalapril on hemoglobin, circulating erythropoietin, and insulin-like growth factor-1 in patients with and without posttransplant erythrocytosis

Both angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists reduce hemoglobin (Hb) levels in patients with posttransplantation erythrocytosis (PTE). However, their effects in transplant recipients without PTE are not certain, and the mechanism by which they reduce Hb levels in patients with PTE remains unclear. This study evaluated the effects of losartan and enalapril on Hb levels in relation to serum erythropoietin (EPO) and insulin-like growth factor-1 (IGF-1) levels in 8 patients with PTE and 10 patients without PTE. All 18 patients were treated sequentially with 24 weeks of losartan therapy, followed by 24 weeks of enalapril therapy; the two treatment phases were separated by a washout period. Patients with PTE showed significantly greater baseline Hb and IGF-1 concentrations compared with patients without PTE before both losartan and enalapril treatments. Baseline serum EPO levels were similar for patients with and without PTE. Baseline Hb level correlated significantly with IGF-1 level (r = 0.517; P = 0.002), but not with EPO level. Treatment with enalapril, 5 mg, reduced Hb levels more markedly than treatment with losartan, 50 mg, in patients with PTE. In patients without PTE, enalapril, 5 mg, mildly reduced Hb levels, whereas losartan, 50 mg, had no significant Hb-lowering effect. The reduction in Hb levels with enalapril therapy in patients with PTE was associated with a significant reduction in circulating IGF-1 levels, but not EPO levels, whereas losartan reduced Hb levels with no significant change in circulating IGF-1 and EPO levels. In patients without PTE, no significant change was noted in serum EPO and IGF-1 levels with either treatment. The differential Hb-lowering effect with losartan and enalapril treatment in patients with and without PTE suggests that the pathogenesis for PTE is complex and heterogeneous. Different erythropoietic mechanisms may be involved in patients with and without PTE. Further large-scale study is needed to determine the exact interaction between the renin-angiotensin system and regulation of IGF-1 and EPO synthesis and define the exact mechanism by which losartan and enalapril reduce Hb levels.

Losartan may modulate erythropoietin production

Erythropoietin (Epo) is distinct amongst haematopoietic hormones, in that it is produced remote from the bone marrow. The tissue oxygen pressure required to trigger the Epo gene under physiological conditions is uniquely sited at a restricted area in the kidney termed the critmeter. Angiotensin II (Ang II) increases sodium reabsorption and hence oxygen consumption at any given bloodflow rate; therefore, it may affect the balance of renal oxygen supply vs. demand and hence Epo production. The purpose of this study was to determine whether Epo production is modulated by the renin-angiotensin system (RAS). Twenty normal subjects on a controlled sodium and protein diet had glomerular filtration rate (GFR) and renal plasma flow (RPF)assessed by standard methods of inulin and para-aminohippurate clearance, respectively, at baseline, hourly after the administration of losartan (25 mg) and after each 30 minute period of the infusion of Ang II at doses of 0.5, 1.5 and 2.5 ng/kg/minute. The baseline GFR was 115+/-4.0 ml/minute/1.73 m2, RPF 650+/-29 ml/minute/1.73 m2 and Epo 12.4+/-0.8 U/L. In spite of a marked increase in filtration fraction (FF) with Ang II, no changes in serum Epo levels were observed at two hours(11.7+/-1.3 U/L, p=n.s. compared with baseline). After the administration of losartan, there was a variable effect on FF, but a strong correlation of the change in serum Epo concentration and the change in FF(r=0.648, p=0.002), suggesting that the RAS may modulate Epo production.

Angiotensin II infusion increases plasma erythropoietin levels via an angiotensin II type 1 receptor-dependent pathway

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEIs) have been shown to lower hematocrit and erythropoietin (EPO), but a direct link between angiotensin II (Ang II) and EPO in humans has not been shown.

METHODS

Placebo or Ang II was infused for six hours in nine healthy male volunteers with and without blockade of the Ang II subtype 1 receptor (AT1R). EPO concentrations were measured 3, 6, 12, and 24 hours after the start of the infusion.

RESULTS

Ang II raised the mean arterial pressure by about 20 mm Hg. Consistent with the known diurnal variation, EPO levels rose significantly (P < or = 0.02) during the day in all groups. During Ang II infusion, EPO levels rose to significantly higher levels after 6 and 12 hours compared with placebo [9.9 +/- 3.5 vs. 7.2 +/- 3.1 mU/mL (3 h, P = NS); 16.9 +/- 4.5 vs. 8.8 +/- 3.7 mU/mL (6 h, P = 0.01); 17.0 +/- 8.6 vs. 11.1 +/- 4.7 mU/mL (12 h, P = 0.01)] and returned to baseline after 24 hours (7.9 +/- 3.8 vs. 10.6 +/- 8.6 mU/mL, P = NS). With AT1R blockade, blood pressure remained normal during Ang II infusion, and EPO levels were never significantly different from placebo [6.8 +/- 4.8, 10.5 +/- 5.6, 13.1 +/- 9.0, and 12.4 +/- 10.1 mU/mL at 3, 6, 12, and 24 h after infusion, respectively, P = NS].

CONCLUSIONS

Ang II increases EPO levels in humans. This increase requires the participation of AT1R.

Erythropoietin deficiency causes anemia in nephrotic children with normal kidney function

Anemia in persistent nephrotic syndrome (NS) has been described in a few case reports but has not been studied systematically. We present a group of 19 children with NS who developed anemia before the deterioration of kidney function. The aim of our study is to determine whether erythropoietin (EPO) and/or iron deficiency are causative factors and to evaluate the effect of EPO replacement therapy. Serum EPO levels, iron status, and vitamin B(12) concentrations were measured in nephrotic patients with anemia (NS-A) and compared with those of nephrotic children with normal hemoglobin (Hb) levels (NS-NHb; n = 13). Two control groups consisted of age-matched patients without kidney disease or hypoxemia with either iron deficiency anemia (IDA; n = 19) or normal Hb concentrations (NHb; n = 16). Most NS-A patients experienced persistent steroid-resistant NS, whereas most NS-NHb children had steroid-responsive NS. Although serum iron, ferritin, and B(12) levels were significantly lower in NS-A children, appropriate replacement therapy that resulted in normalization of ferritin and/or cobalamin levels did not lead to correction of the anemia. NS-A patients had greater EPO levels than those without anemia (21.6 +/- 3.3 versus 5.5 +/- 0.8 IU/L; P: < 0.001), but their response to anemia was inappropriately low compared with IDA children (EPO, 94.6 +/- 15.1 IU/L) despite similar Hb concentrations. EPO therapy for 4 to 9 months in 6 NS-A children with Hb levels less than 9 g/dL led to resolution of the anemia. In conclusion, anemia is a common feature of persistent NS that develops before the deterioration of kidney function. Depletion of iron stores may contribute to the development of anemia, but iron replacement therapy is ineffective. Nephrotic patients have EPO deficiency with a blunted response to anemia. The EPO deficiency is amenable to EPO therapy, which is recommended for this group of patients.

Serum erythropoietin in heart failure patients treated with ACE-inhibitors or AT(1) antagonists

BACKGROUND

Erythropoietin (Epo), a growth factor produced by the kidney, is important in heart failure patients to promote oxygen delivery to tissues. Seventy-two chronic heart failure (CHF) patients at our outpatient clinic were subjected to morning serum Epo-level measurements and classified according to NYHA criteria.

RESULTS

Forty-eight patients of classes III and IV had a significantly elevated serum Epo-level of 42.9+/-40.3 mIU/ml (mean+/-1 S.D.) when compared to the mean level of 24 patients of classes I and II who had a normal range mean value of 13.4+/-6.2 mIU/ml (P<0.05). Patients on angiotensin-converting enzyme (ACE) inhibitors showed a trend towards lower serum Epo-levels compared to patients treated with angiotensin-II type-1 receptor antagonists (AT(1) antagonists) (levels: 33.3+/-35.6 mIU/ml and 43.6+/-38.1 mIU/ml). This trend did not, however, reach statistical significance (P=0.36).

CONCLUSION

We suggest that a desirable Epo increase in class III and IV CHF patients could be achieved by either recombinant human Epo administration or, possibly, by appropriate selection of the concomitant medical therapy. A large prospective study shall investigate the possible advantage of AT(1) antagonists over ACE-inhibitors with regard to Epo effect.

Lack of angiotensin II-facilitated erythropoiesis causes anemia in angiotensin-converting enzyme-deficient mice

While nephrologists often observe reduced hematocrit associated with inhibitors of angiotensin-converting enzyme (ACE), the basis for this effect is not well understood. We now report that two strains of ACE knockout mice have a normocytic anemia associated with elevated plasma erythropoietin levels. (51)Cr labeling of red cells showed that the knockout mice have a normal total blood volume but a reduced red cell mass. ACE knockout mice, which lack tissue ACE, are anemic despite having normal renal function. These mice have increased plasma levels of the peptide acetyl-SDKP, a possible stem cell suppressor. However, they also show low plasma levels of angiotensin II. Infusion of angiotensin II for 2 weeks increased hematocrit to near normal levels. These data suggest that angiotensin II facilitates erythropoiesis, a conclusion with implications for the management of chronically ill patients on inhibitors of the renin-angiotensin system.

ACE inhibitors do not induce recombinant human erythropoietin resistance in hemodialysis patients

Angiotensin-converting enzyme (ACE) inhibitors may exacerbate anemia in patients with chronic renal failure, as well as in dialysis patients. To better answer this question, a prospective, crossover study was conducted to evaluate the effect of ACE inhibitors on recombinant human erythropoietin (rHuEPO) requirements in hemodialysis patients. Patients administered an ACE inhibitor when entering the study remained on this drug for the initial 4 months and were then switched to another antihypertensive agent for 4 more months. Patients not initially administered an ACE inhibitor were switched to lisinopril at 4 months. rHuEPO doses were adjusted using a sliding scale based on weekly laboratory hematocrit values. The inclusion criteria were met by 51 patients undergoing dialysis. Demographics were as follows: 61% were women, 64% were black, 46% had diabetes, average age was 53.2 +/- 13.3 years, and time on hemodialysis was 38.0 +/- 44.5 months. Thirty-three patients completed the study. Hematocrit averaged 32.7% +/- 1.9% while on ACE inhibitor therapy and 33.1% +/- 2.1% off ACE inhibitor therapy (P = 0.217). There was no difference in rHuEPO dose per treatment during each period (3,500 +/- 1,549 U on ACE inhibitor therapy versus 3,312 +/- 1,492 U off ACE inhibitor therapy; P = 0.300). No significant differences were found in degree of blood pressure control or various clinical and laboratory parameters that might be associated with rHuEPO resistance between the two periods. Similarly, no differences were found in hospitalization days, duration of infections, or transfusion requirements. These findings suggest that ACE inhibitors do not contribute to rHuEPO resistance in hemodialysis patients.