Abnormal hemodynamics and elevated angiotensin II plasma levels in polydipsic patients on regular hemodialysis treatment

Relationship between chronic kidney disease and sarcopenia

Few studies have investigated the relationship between sarcopenia and mild to moderate renal decline. This study aimed to investigate the relationship between chronic kidney disease (CKD) and sarcopenia. In total, 123 patients hospitalized with CKD and 57 healthy volunteers who underwent physical examination during the same period (control group) were analyzed. Body compositions were measured by dual-energy X-ray absorptiometry, and the relative appendicular skeletal muscle index (RASMI) was calculated. Muscular strength was evaluated using hydraulic hand dynamometer. Walking speed within 6 m was measured for muscular function assessment. Single-photon emission computed tomography was performed to measure the glomerular filtration rate of CKD patients, who were then divided into CKD1 (55 patients in CKD stages 1 and 2) and CKD2 (68 patients in CKD stages 3-5). RASMI showed a downward trend with CKD progression (P = 0.001). Multivariate logistic regression analysis showed that age and CKD progression were independent risk factors for sarcopenia. The morbidity of sarcopenia was significantly greater in CKD patients than in healthy volunteers, and the degree of muscle loss was closely related to CKD progression.

Clinical relevance of sarcopenia in chronic kidney disease

PURPOSE OF REVIEW

In this article, we review sarcopenia in chronic kidney disease (CKD). We aim to present how definitions of sarcopenia from the general population may pertain to those with CKD, its assessment by clinicians and emerging therapies for sarcopenia in CKD. For this review, we limit our description and recommendations to patients with CKD who are not on dialysis.

RECENT FINDINGS

Poorer parameters of lean mass, strength and physical function are associated with worsening patient-centered outcomes such as limiting mobility, falls and mortality in CKD; however, the magnitude of these associations are different in those with and without CKD. Sarcopenia in CKD is a balance between skeletal muscle regeneration and catabolism, which are both altered in the uremic environment. Multiple pathways are involved in these derangements, which are briefly reviewed. Differences between commonly used terms cachexia, frailty, protein-energy wasting, dynapenia and sarcopenia are described. Therapeutic options in predialysis CKD are not well studied; therefore, we review exercise options and emerging pharmacological therapies.

SUMMARY

Sarcopenia, now with its own International Classification of Diseases, 10th Revision (ICD-10) code, is of importance clinically and should be accounted for in research studies in patients with CKD. Multiple therapies for sarcopenia are in development and will hopefully be available for our patients in the future.

Hyponatraemia, mortality and haemodialysis: An unexplained association

BACKGROUND

As in the general population, in patients on haemodialysis (HD) hyponatraemia is associated with higher mortality risk. The objective of this article was to study the relationship between predialysis serum sodium (sNa) and mortality in an HD population. We also intended to define hyponatraemia and determine the characteristics of hyponatraemic patients in terms of anthropometric data, analytical features, dialysis measurements and hydration (bioimpedance).

METHODS

Observational, descriptive study of a cohort of HD incident patients. The independent variable was the mean of each patient's sNa analysed during their first 6 months on HD.

RESULTS

A total of 4,153 patients were included in the study. Mean age was 64.7 years; 65.2% of the patients were male and 35% were diabetics. Mean follow-up time was 21.48 (SD) (1.31) months. sNa had a normal distribution, with a mean (SD)=138.46 (2.7) mEq/l. Body weight, diabetes mellitus, systolic blood pressure, interdialytic weight gain, total ultrafiltration, serum glucose, albumin and creatinine, vascular access and haemodialysis type, acquire significant differences between sodium quartiles. Lean tissue index (LTI) in patients with low serum sodium, Q1 (135 mEq/l), was significantly lower than the LTI of patients from the other serum sodium quartiles. Patients with sNa<136 mEq/l had a higher independent mortality risk (OR=1.62) (Cox regression analysis).

CONCLUSIONS

HD patients with hyponatraemia patients have a poor prognosis and present malnutrition or fluid overload.

Bone is Not Alone: the Effects of Skeletal Muscle Dysfunction in Chronic Kidney Disease

Chronic kidney disease (CKD) is associated with a decline in muscle mass, strength, and function, collectively called "sarcopenia." Sarcopenia is associated with hospitalizations and mortality in CKD and is therefore important to understand and characterize. While the focus of skeletal health in CKD has traditionally focused on bone and mineral aberrations, it is now recognized that sarcopenia must also play a role in poor musculoskeletal health in this population. In this paper, we present an overview of skeletal muscle changes in CKD, including defects in skeletal muscle catabolism and anabolism in uremic tissue. There are many gaps in knowledge in this field that should be the focus for future research to unravel pathogenesis and therapies for musculoskeletal health in CKD.

Protein phosphatase 2C-alpha knockdown reduces angiotensin II-mediated skeletal muscle wasting via restoration of mitochondrial recycling and function

Background

Circulating angiotensin II (AngII) is elevated in congestive heart failure (CHF), and leads to skeletal muscle wasting, which is strongly associated with poor patient outcomes. We previously found that AngII upregulates protein phosphatase 2C-alpha (PP2Cα) and dephosphorylates AMP-activated protein kinase (AMPK), a critical regulator of cellular metabolism, in skeletal muscle.

Methods

To determine the role of PP2Cα in AngII-induced wasting, gastrocnemius (Gas) muscles of FVB mice were injected with scrambled or PP2Cα siRNA and mice were infused with saline or AngII for 4 days.

Results

Knockdown of PP2Cα reduced AngII wasting, blocked AngII upregulation of PP2Cα, increased p-T172-AMPK, and inhibited AngII-mediated reductions in peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear respiratory factor 1 (NRF1), mitochondrial transcription factor A (TFAM), in complex IV activity, and in ATP levels. AngII impaired the rate of autophagy as determined by a 2.4-fold increase in p62/SQSTM1 (p62) accumulation. This induction was reduced by PP2Cα knockdown, which also increased beclin-1 expression and microtubule-associated protein 1 light chain 3 (LC3)-II conversion in AngII-infused Gas. AngII reduced activating S555 phosphorylation of UNC-51-like kinase 1 (ULK1), a critical regulator of autophagosome formation, and increased inhibitory S757 ULK1 phosphorylation and these effects were prevented by PP2Cα siRNA.

Conclusions

AngII inhibited AMPK activity and reduced PGC-1α and TFAM expression (thereby inhibiting mitochondrial biogenesis) and impaired ULK1 activation and autophagy (thereby also inhibiting clearance of damaged mitochondria), resulting in mitochondrial dysfunction, decreased ATP, and wasting. Knockdown of PP2Cα normalized AMPK activity, PGC-1α, NRF1, and TFAM levels and blocked AngII inhibition of ULK1, leading to improved mitochondrial biogenesis/recycling/function, energy production, and inhibition of AngII-induced wasting. These results demonstrate novel effects of AngII on cellular metabolism that are likely critical in mediating the muscle wasting that is a hallmark of CHF.

Dialysis hypotension: a role for inadequate increase in arginine vasopressin levels? A systematic literature review and meta-analysis

BACKGROUND

Intradialytic hypotension is a common complication of hemodialysis (HD). Some studies have suggested that inadequate arginine vasopressin (AVP) increase could play a role in the pathogenesis of intradialytic hypotension. However, AVP levels during HD and its relation to hypotension has never been systematically studied.

SUMMARY

PubMed and Embase were searched (1970-2013, search terms 'vasopressin' and 'hemodialysis') for studies reporting on AVP levels during standard HD or other dialysis techniques. Observational studies reporting on AVP levels pre- and postdialysis were additionally included in a meta-analysis. Thirty-seven studies were included in the systematic literature review, of which 26 studies were eligible for meta-analysis. The main findings were that pretreatment AVP levels were higher in dialysis patients compared with healthy controls (6.4 ± 3.5 vs. 2.5 ± 1.3 pg/ml, p = 0.003) and that plasma AVP levels showed little or no increase during HD (from 7.0 ± 4.9 to 8.8 ± 9.3, p = 0.433). Significant heterogeneity was found between studies. Meta-regression analysis revealed no significant associations between AVP and patient or study characteristics. Studies on other dialysis techniques showed mixed results regarding the AVP course. The eight studies that addressed the relation between intradialytic hypotension and AVP also showed inconsistent results.

KEY MESSAGES

Plasma AVP levels are higher in dialysis patients compared with healthy controls, but show little or no increase during HD. The lack of a rise in AVP levels during HD may be pathophysiologically involved in the onset of intradialytic hypotension, but firm conclusions are not possible from our review of the literature.

Low serum sodium is associated with protein energy wasting and increased interdialytic weight gain in haemodialysis patients

Background

Low serum sodium (Na) has been associated with decreased body mass index and increased cardiovascular mortality in haemodialysis (HD) patients. We examined the relationship between serum Na and selected nutritional parameters of protein energy wasting that are not affected from the hydration status in a cohort of HD patients.

Methods

Triceps skinfold thickness (TSF), mid-arm circumference (MAC), mid-arm muscle circumference (MAMC), handgrip strength (HGS) and subjective global assessment (SGA) were assessed in maintenance HD patients using standard techniques. MAMC was calculated with the formula MAMC (cm) = MAC (cm) −3.142 × TSF cm. Pre-dialysis serum Na values from routine monthly laboratory measurements were averaged for the last 6 months prior to the nutritional assessment.

Results

Altogether 172 patients with anthropometric data were included in the final analysis. Mean age was 66 ± 14, females 62 (36%) and diabetics 48 (28.9%). Patients with pre-dialysis serum Na below the mean value (136.2 mEq/L) had lower MAMC, HGS, SGA scores and albumin levels (23.50 ± 3.16 cm versus 24.58 ± 3.71 cm, P = 0.048; 21.7 ± 13.6 kg versus 28.0 ± 12.4 kg, P = 0.030; 5.1 ± 1.2 versus 5.7 ± 1.0, P = 0.012 and 31.65 ± 4.73 mg/L versus 32.25 ± 3.91 mg/L, P = 0.022, respectively) and higher interdialytic weight gains. Pre-dialysis serum Na correlated positively with MAMC, handgrip and SGA (Pearson's correlation r = 0.165, P = 0.031, r = 0.237, P = 0.022 and r = 0.195, P = 0.011, respectively).

Conclusion

This study demonstrates that low serum sodium is associated with protein energy wasting and increased interdialytic weight gain in HD patients.

Angiotensin II stimulates cardiac fibroblast migration via the differential regulation of matrixins and RECK

Sustained induction and activation of matrixins (matrix metalloproteinases or MMPs), and the destruction and deposition of extracellular matrix (ECM), are the hallmarks of cardiac fibrosis. The reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) is a unique membrane-anchored endogenous MMP regulator. We hypothesized that elevated angiotensin II (Ang II), which is associated with fibrosis in the heart, differentially regulates MMPs and RECK both in vivo and in vitro. Continuous infusion of Ang II into male C57Bl/6 mice for 2weeks resulted in cardiac fibrosis, with increased expressions of MMPs 2, 7, 9 and 14, and of collagens Ia1 and IIIa1. The expression of RECK, however, was markedly suppressed. These effects were inhibited by co-treatment with the Ang II type 1 receptor (AT1) antagonist losartan. In vitro, Ang II suppressed RECK expression in adult mouse cardiac fibroblasts (CF) via AT1/Nox4-dependent ERK/Sp1 activation, but induced MMPs 2, 14 and 9 via NF-κB, AP-1 and/or Sp1 activation. Further, while forced expression of RECK inhibits, its knockdown potentiates Ang II-induced CF migration. Notably, RECK overexpression reduced Ang II-induced MMPs 2, 9 and 14 activation, but enhanced collagens Ia1 and IIIa1 expression and soluble collagen release. These results demonstrate for the first time that Ang II suppresses RECK, but induces MMPs both in vivo and in vitro, and RECK overexpression blunts Ang II-induced MMP activation and CF migration in vitro. Strategies that upregulate RECK expression in vivo have the potential to attenuate sustained MMP expression, and blunt fibrosis and adverse remodeling in hypertensive heart diseases.

Angiotensin II inhibits satellite cell proliferation and prevents skeletal muscle regeneration

Cachexia is a serious complication of many chronic diseases, such as congestive heart failure (CHF) and chronic kidney disease (CKD). Although patients with advanced CHF or CKD often have increased angiotensin II (Ang II) levels and cachexia and Ang II causes skeletal muscle wasting in rodents, the potential effects of Ang II on muscle regeneration are unknown. Muscle regeneration is highly dependent on the ability of a pool of muscle stem cells (satellite cells) to proliferate and to repair damaged myofibers or form new myofibers. Here we show that Ang II reduced skeletal muscle regeneration via inhibition of satellite cell (SC) proliferation. Ang II reduced the number of regenerating myofibers and decreased expression of SC proliferation/differentiation markers (MyoD, myogenin, and active-Notch) after cardiotoxin-induced muscle injury in vivo and in SCs cultured in vitro. Ang II depleted the basal pool of SCs, as detected in Myf5(nLacZ/+) mice and by FACS sorting, and this effect was inhibited by Ang II AT1 receptor (AT1R) blockade and in AT1aR-null mice. AT1R was highly expressed in SCs, and Notch activation abrogated the AT1R-mediated antiproliferative effect of Ang II in cultured SCs. In mice that developed CHF postmyocardial infarction, there was skeletal muscle wasting and reduced SC numbers that were inhibited by AT1R blockade. Ang II inhibition of skeletal muscle regeneration via AT1 receptor-dependent suppression of SC Notch and MyoD signaling and proliferation is likely to play an important role in mechanisms leading to cachexia in chronic disease states such as CHF and CKD.

Molecular mechanisms and signaling pathways of angiotensin II-induced muscle wasting: potential therapeutic targets for cardiac cachexia

Cachexia is a serious complication of many chronic diseases, such as congestive heart failure (CHF) and chronic kidney disease (CKD). Many factors are involved in the development of cachexia, and there is increasing evidence that angiotensin II (Ang II), the main effector molecule of the renin-angiotensin system (RAS), plays an important role in this process. Patients with advanced CHF or CKD often have increased Ang II levels and cachexia, and angiotensin-converting enzyme (ACE) inhibitor treatment improves weight loss. In rodent models, an increase in systemic Ang II leads to weight loss through increased protein breakdown, reduced protein synthesis in skeletal muscle and decreased appetite. Ang II activates the ubiquitin-proteasome system via generation of reactive oxygen species and via inhibition of the insulin-like growth factor-1 signaling pathway. Furthermore, Ang II inhibits 5' AMP-activated protein kinase (AMPK) activity and disrupts normal energy balance. Ang II also increases cytokines and circulating hormones such as tumor necrosis factor-α, interleukin-6, serum amyloid-A, glucocorticoids and myostatin, which regulate muscle protein synthesis and degradation. Ang II acts on hypothalamic neurons to regulate orexigenic/anorexigenic neuropeptides, such as neuropeptide-Y, orexin and corticotropin-releasing hormone, leading to reduced appetite. Also, Ang II may regulate skeletal muscle regenerative processes. Several clinical studies have indicated that blockade of Ang II signaling via ACE inhibitors or Ang II type 1 receptor blockers prevents weight loss and improves muscle strength. Thus the RAS is a promising target for the treatment of muscle atrophy in patients with CHF and CKD. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

Angiotensin II reduces food intake by altering orexigenic neuropeptide expression in the mouse hypothalamus

Angiotensin II (Ang II), which is elevated in many chronic disease states such as end-stage renal disease and congestive heart failure, induces cachexia and skeletal muscle wasting by increasing muscle protein breakdown and reducing food intake. Neurohormonal mechanisms that mediate Ang II-induced appetite suppression are unknown. Consequently, we examined the effect of Ang II on expression of genes regulating appetite. Systemic Ang II (1 μg/kg · min) infusion in FVB mice rapidly reduced hypothalamic expression of neuropeptide Y (Npy) and orexin and decreased food intake at 6 h compared with sham-infused controls but did not change peripheral leptin, ghrelin, adiponectin, glucagon-like peptide, peptide YY, or cholecystokinin levels. These effects were completely blocked by the Ang II type I receptor antagonist candesartan or deletion of Ang II type 1a receptor. Ang II markedly reduced phosphorylation of AMP-activated protein kinase (AMPK), an enzyme that is known to regulate Npy expression. Intracerebroventricular Ang II infusion (50 ng/kg · min) caused a reduction of food intake, and Ang II dose dependently reduced Npy and orexin expression in the hypothalamus cultured ex vivo. The reduction of Npy and orexin in hypothalamic cultures was completely prevented by candesartan or the AMPK activator 5-aminoimidazole-4-carboxamide ribonucleoside. Thus, Ang II type 1a receptor-dependent Ang II signaling reduces food intake by suppressing the hypothalamic expression of Npy and orexin, likely via AMPK dephosphorylation. These findings have major implications for understanding mechanisms of cachexia in chronic disease states such as congestive heart failure and end-stage renal disease, in which the renin-angiotensin system is activated.

Angiotensin II infusion induces marked diaphragmatic skeletal muscle atrophy

Advanced congestive heart failure (CHF) and chronic kidney disease (CKD) are characterized by increased angiotensin II (Ang II) levels and are often accompanied by significant skeletal muscle wasting that negatively impacts mortality and morbidity. Both CHF and CKD patients have respiratory muscle dysfunction, however the potential effects of Ang II on respiratory muscles are unknown. We investigated the effects of Ang II on diaphragm muscle in FVB mice. Ang II induced significant diaphragm muscle wasting (18.7±1.6% decrease in weight at one week) and reduction in fiber cross-sectional area. Expression of the E3 ubiquitin ligases atrogin-1 and muscle ring finger-1 (MuRF-1) and of the pro-apoptotic factor BAX was increased after 24 h of Ang II infusion (4.4±0.3 fold, 3.1±0.5 fold and 1.6±0.2 fold, respectively, compared to sham infused control) suggesting increased muscle protein degradation and apoptosis. In Ang II infused animals, there was significant regeneration of injured diaphragm muscles at 7 days as indicated by an increase in the number of myofibers with centralized nuclei and high expression of embryonic myosin heavy chain (E-MyHC, 11.2±3.3 fold increase) and of the satellite cell marker M-cadherin (59.2±22.2% increase). Furthermore, there was an increase in expression of insulin-like growth factor-1 (IGF-1, 1.8±0.3 fold increase) in Ang II infused diaphragm, suggesting the involvement of IGF-1 in diaphragm muscle regeneration. Bone-marrow transplantation experiments indicated that although there was recruitment of bone-marrow derived cells to the injured diaphragm in Ang II infused mice (267.0±74.6% increase), those cells did not express markers of muscle stem cells or regenerating myofibers. In conclusion, Ang II causes marked diaphragm muscle wasting, which may be important for the pathophysiology of respiratory muscle dysfunction and cachexia in conditions such as CHF and CKD.

Angiotensin II upregulates protein phosphatase 2Cα and inhibits AMP-activated protein kinase signaling and energy balance leading to skeletal muscle wasting

Congestive heart failure and chronic kidney disease are characterized by chronically elevated angiotensin II (Ang II) and muscle wasting. Ang II causes skeletal muscle wasting by reducing appetite and by enhancing catabolism. The serine/threonine kinase AMP-activated protein kinase (AMPK) functions mainly as a sensor of cellular energy status. It is energy sparing and favors ATP generation. We hypothesized that Ang II induces muscle wasting in part by inhibiting AMPK signaling and altering cellular energy balance. Our results show that Ang II infusion in mice reduced gastrocnemius muscle weight by 26% and depleted ATP by 74%. In addition, Ang II upregulated protein phosphatase 2Cα by 2.6-fold and reduced AMPK phosphorylation and signaling in muscle. Importantly, the pharmacological AMPK activator 5-aminoimidazole-4-carboxamide ribonucleoside restored AMPK activity to levels of pair-fed controls and reversed Ang II-mediated ATP depletion and muscle wasting. Moreover, 5-aminoimidazole-4-carboxamide ribonucleoside activated Akt and inhibited Ang II-induced increases in E3 ubiquitin ligase expression. These novel results demonstrate critical roles for energy depletion and AMPK inhibition in Ang II-induced skeletal muscle wasting and suggest a therapeutic potential for AMPK activators in diseases characterized by muscle wasting.

The risks of high ultrafiltration rate in chronic hemodialysis: implications for patient care

As dialytic practice has evolved, hemodialysis (HD) adequacy has come to be defined in terms of small molecule clearance. A growing body of evidence suggests that fluid dynamics, specifically ultrafiltration rate (UFR), bear clinical and physiological significance and should perhaps play a more central role in titrating HD therapy. Three recent studies have shown an independent association between higher UFR and mortality. Further work is needed to determine whether this relationship represents a direct toxic effect of rapid fluid perturbations or whether this association is a consequence of confounding on the basis of large interdialytic weight gain, as each would prompt a different therapeutic response. This mounting evidence builds the case that fluid management should play a more central role in the dialytic prescription and that more individualized approaches to fluid management should be encouraged.

Mortality associated with low serum sodium concentration in maintenance hemodialysis

BACKGROUND

low serum sodium concentrations are associated with an increased risk of death in the general population, but causality is uncertain due to confounding from clinical conditions such as congestive heart failure and cirrhosis, in which hyponatremia results from elevated levels of arginine vasopressin.

METHODS

to examine the association between predialysis serum sodium concentration and mortality in patients undergoing hemodialysis for end-stage renal disease, a condition in which arginine vasopressin does not affect water excretion and osmoregulation, we studied 1549 oligoanuric participants in the HEMO study, a randomized controlled trial of hemodialysis patients examining the effect of hemodialysis dose and flux. We used proportional hazards models to compare the risk of death according to predialysis serum sodium concentration.

RESULTS

considered as a continuous variable, each 4-mEq/L increment in baseline predialysis serum sodium concentration was associated with a hazard ratio for all-cause mortality of 0.84 (95% confidence interval (CI), 0.78-0.90). Multivariable adjustment for demographic, clinical, laboratory, and dialysis-specific covariates, including ultrafiltration volume, did not appreciably change the results (hazard ratio for all-cause mortality of 0.89; 95% CI, 0.82-0.96). the results also were consistent in time-updated analyses using repeated measures of serum sodium and other relevant covariates.

CONCLUSION

Lower predialysis serum sodium concentration is associated with an increased risk of death. Considering the unique physiology in the dialysis population, these findings raise the possibility that hyponatremia itself may be a causal determinant of mortality in the broader population.

Candesartan cilexetil on regular hemodialysis: inability to reduce excessive thirst, but good tolerance and efficacy in hypertensive patients

It has been postulated that hypertension and interdialytic weight gain in hemodialysis patients are related to the activation of the renin-angiotensin system. Angiotensin II type 1 (ATI) receptor antagonists are new anti-hypertensive agents and are currently the most specific means of blocking the renin-angiotensin enzymatic cascade. Recent studies show that candesartan cilexetil regulates thirst and hypertension in rodents, via cerebral AT1 receptor blockade. We therefore conducted a prospective open study of candesartan cilexetil in 21 hypertensive patients on long-term hemodialysis during 6 weeks, focusing on thirst regulation. We also performed a prospective follow-up study of tolerance of candesartan and its anti-hypertensive efficacy after this 6-week study, while the patients remained on this therapy. Weight gain between hemodialysis sessions did not differ between the periods before and during candesartan cilexetil therapy. Median absolute interdialytic weight gain was 2.35 kg (range: 0.55-5) before therapy, compared to 2.25 kg (range: 0.35-4.65) during therapy (p > 0.05, Wilcoxon test). The median interdialytic weight gain/dry weight index was 3.7% (range: 1.15-7) before therapy and 3.6% (range: 0.7-6.6) during candesartan therapy (p > 0.05, Wilcoxon test). The median dose of candesartan cilexetil was 12 mg/day (range: 4-24). The median total duration of therapy with candesartan (including the 6 weeks of the thirst study) was 12 months (range: 2-25). During candesartan cilexetil therapy, the number of concomitant anti-hypertensive drugs per patient fell significantly (median number of anti-hypertensive drugs before candesartan =2 (range: 1-6); during candesartan =1 (range: 1-5) (p < 0.02, Wilcoxon test). No anaphylactoid reactions occurred. A total of 161 episodes of hypotension (5%) occurred during 3074 hemodialysis sessions (including the 6 weeks of the thirst study) We conclude that, like angiotensin converting enzyme inhibitors and the other angiotensin receptor antagonists, candesartan cilexetil is unable to reduce interdialytic weight gain in hemodialysis patients. This study also shows that the irreversible angiotensin II receptor antagonist candesartan cilexetil is a safe and effective therapeutic option for hypertensive hemodialysis patients.

The pharmacokinetics and pharmacodynamics of angiotensin-receptor blockers in end-stage renal disease

Angiotensin-converting enzyme (ACE) inhibitors and more recently angiotensin-receptor blockers (ARBs) have become popular therapies in the end-stage renal disease (ESRD) patient. The ability of either of these drug classes to reduce blood pressure in the ESRD patient is well accepted; however, there is considerably less information available to guide the clinician in the safe and effective use of these drugs in the ESRD patient with congestive heart failure and/or coronary artery disease. Head-to-head studies in the ESRD patient are lacking for both drug classes. Several pharmacokinetic factors can influence the selection of these drugs, including dialysability and the propensity for systemic accumulation. ACE inhibitors (ACE-Is) and ARBs are recognised as having a range of nonpressor effects that are pertinent to patients with ESRD. Such effects include their ability to decrease both thirst drive and erythropoiesis. These drug classes, though, are distinguishable by the unique adverse effect profile for ACE-Is. As is the case in patients without renal failure, ESRD patients can experience cough and, less frequently, angioneurotic oedema with ACE-Is. In the ESRD population, so-called anaphylactoid dialyser reactions can occur in conjunction with ACE-I use. The use of a drug from within the ARB class carries both less risk and permits a compound with a preferred pharmacokinetic profile limited dialysability and minimal systemic accumulation to be administered. These attributes would favour the increased use of ARBs in this population.

Pharmacotherapy in congestive heart failure: angiotensin II and thirst: therapeutic considerations

Angiotensin II is the effector peptide of the renin-angiotensin system and is involved in a wide range of physiologic functions that relate to volume control. In this regard, angiotensin II maintains and regulates salt and water balance, is critically involved in cardiovascular function, and governs thirst. When present in excess, angiotensin II can pathologically influence each of these functions. The role of angiotensin II in controlling sodium balance, in both renal insufficiency states and congestive heart failure, is clearly recognized. Alternatively, it is poorly appreciated that angiotensin II plays an important role in both normal and pathologic thirst states. The latter is a potential problem in both end-stage renal disease and congestive heart failure. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor antagonists (AT1-RAs) have both been shown to reduce abnormal thirst drive. Whether an ACE inhibitor or an AT1-RA lessens thirst drive to any significant degree relates to its capacity to penetrate the blood-brain barrier. Head-to-head comparisons of ACE inhibitors and AT1-RAs, as to their effect on thirst drive, have not been undertaken in a systematic fashion; thus, until otherwise established, the effect of these compounds on thirst should be viewed as a class effect, albeit one that is likely to be dose-dependent. (c)2001 CHF, Inc.

Risk-benefit ratio of angiotensin antagonists versus ACE inhibitors in end-stage renal disease

The effective treatment of hypertension is an extremely important consideration in patients with end-stage renal disease (ESRD). Virtually any drug class--with the possible exception of diuretics--can be used to treat hypertension in the patient with ESRD. Despite there being such a wide range of treatment options, drugs which interrupt the renin-angiotensin axis are generally suggested as agents of choice in this population, even though the evidence in support of their preferential use is quite scanty. ACE inhibitors, and more recently angiotensin antagonists, are the 2 drug classes most commonly employed to alter renin-angiotensin axis activity and therefore produce blood pressure control. ACE inhibitor use in patients with ESRD can sometimes prove an exacting proposition. ACE inhibitors are variably dialysed, with compounds such as catopril, enalapril, lisinopril and perindopril undergoing substantial cross-dialyser clearance during a standard dialysis session. This phenomenon makes the selection of a dose and the timing of administration for an ACE inhibitor a complex issue in patients with ESRD. Furthermore, ACE inhibitors are recognised as having a range of nonpressor effects that are pertinent to patients with ESRD. Such effects include their ability to decrease thirst drive and to decrease erythropoiesis. In addition, ACE inhibitors have a unique adverse effect profile. As is the case with their use in patients without renal failure, use of ACE inhibitors in patients with ESRD can be accompanied by cough and less frequently by angioneurotic oedema. In the ESRD population, ACE inhibitor use is also accompanied by so-called anaphylactoid dialyser reactions. Angiotensin antagonists are similar to ACE inhibitors in their mechanism of blood pressure lowering. Angiotensin antagonists are not dialysable and therefore can be distinguished from a number of the ACE inhibitors. In addition, the adverse effect profile for angiotensin antagonists is remarkably bland, with cough and angioneurotic oedema rarely, if ever, occurring. In patients with ESRD, angiotensin antagonists are also not associated with the anaphylactoid dialyser reactions which occur with ACE inhibitors. The nonpressor effects of angiotensin antagonists--such as an influence on thirst drive and erythropoiesis--have not been explored in nearly the depth, as they have been with ACE inhibitors. Although ACE inhibitors have not been compared directly to angiotensin antagonists in patients with ESRD, angiotensin antagonists possess a number of pharmacokinetic and adverse effect characteristics, which would favour their use in this population.

Use of the medical differential diagnosis to achieve optimal end-stage renal disease outcomes

Compared with the general population, end-stage renal disease (ESRD) patients continue to have a higher than expected morbidity and mortality. Hypoalbuminemia, anemia, hypertension, and inadequate dialysis are all thought to contribute to the high morbidity and mortality among ESRD patients. Anemia algorithms should help to standardize the approach to anemia and the use of recombinant human erythropoietin (rHuEPO), but clinicians still must review each patient individually, searching for and treating the multitude of interrelated factors that affect rHuEPO responsiveness. Hypoalbuminemia is a very strong predictor of increased morbidity and mortality in dialysis and nondialysis patients. The causes of hypoalbuminemia are multifactorial, and diagnosis of the cause of hypoalbuminemia is usually elusive. The basis of the poorer survival in US dialysis patients remains controversial, but inadequate dialysis has been implicated. To assure adequate dialysis, the dialysis prescription must be individualized for each patient, and delivered dialysis must be routinely monitored. Hypertension is associated with left ventricular hypertrophy, which is also an important determinant of survival in ESRD patients. Hypertension should be treated in ESRD patients in conjunction with other interventions that are known to reverse left ventricular hypertrophy. Special efforts must be made in the medical management of hypoalbuminemia, anemia, hypertension, and dialysis treatment adequacy to improve survival in patients with ESRD.

Lack of efficacy of angiotensin-converting enzyme inhibitors in reducing interdialytic weight gain

Angiotensin-converting enzyme inhibitors (ACEIs) have been suggested to reduce interdialytic fluid weight gain, presumably via suppression of the dipsogenic angiotensin II. We retrospectively studied 25 (76% black) chronic hemodialysis patients who received ACEIs for blood pressure control. The mean arterial blood pressure decreased from 115.4 +/- 10.4 mm Hg to 112.7 +/- 9.0 mm Hg (mean +/- SD; P = NS) and there was no change in the interdialytic weight gain (3.74 +/- 1.5 kg v 3.72 +/- 1.5 kg; P = NS). Only 10 (40%) patients had some reduction in their interdialytic weight gain; in four of them the reduction was more than 20% of the pre-ACEI weight gain. When nine patients who had no decline in blood pressure were excluded due to possible noncompliance, the mean arterial blood pressure in the remaining 16 patients (75% black) declined from 119.3 +/- 9.9 mm Hg to 111.6 +/- 9.9 mm Hg (P < 0.0001), but there was no change in the interdialytic fluid weight gain (3.7 +/- 1.4 kg v 3.8 +/- 1.4 kg; P = NS). There was no correlation between age, race, etiology of renal failure, or blood pressure response and change in the interdialytic weight gain after ACEI treatment. Our results do not support the previous report that ACEIs significantly decrease the interdialytic weight gain in chronic hemodialysis patients. The multifactorial nature of excessive fluid intake in the hemodialysis patients and the differences in patient population and study design may account for this discrepancy.