Hyperphosphataemia--a silent killer of patients with renal failure?

Left Ventricular Mass and Functions in Egyptian Children with Chronic Kidney Disease in Comparison to Normal Subjects

Left ventricular hypertrophy (LVH) and cardiac fibrosis are common accompaniments of chronic kidney disease (CKD). They can be rather easily assessed by conventional cardiac imaging modalities, most practically by M-mode or two-dimensional (2D) echocardiography, with adequate recognition of pitfalls. This study uncovers the impact of impaired renal function on left ventricular mass (LVM) and LVM index (LVMI) in children with CKD on regular hemodialysis (HD) attending the Zagazig University Hospital for Children. A total of 80 Egyptian children, out of which 40 subjects having a mean age of 11.2 ± 3.12 years were cases with CKD in stage 5 on regular HD and the other 40 healthy subjects as controls, with a mean age of 12.2 ± 2.54 years, were included in the study and assessed for LVH and LVMI by 2D echocardiography. HD children had a significantly higher mean LVMI (102.3 ± 19.1 vs. 49.6 ± 4.11 g/m², P <0.001) than controls. Relative wall thickness was significantly higher in the patients with CKD patients on HD compared with controls (P <0.001) with a mean value of 0.46 indicating concentric LVH in renal patients. Comparing mitral inflow velocities between both the groups revealed that the patient group had a significant decrease in mitral E-wave velocity (0.88 ± 0.2 vs. 1.1 ± 0.1 m/sec, P <0.001) and E/A velocity ratio (1.3 ± 0.3 vs. 1.7 ± 0.3, P <0.001) in comparison with the control group, but there was no statistically significant difference in A-wave velocity. This indicates early diastolic dysfunction in CKD patients. LV mass changes in CKD children were strongly related to hypocalcemia and Vitamin D deficiency. Children with CKD are prone to the development of cardiac diastolic dysfunction and LVH, so early and regular echocardiographic studies of all children with CKD are recommended to detect early cardiac changes and institute interventions.

Role of dipstick proteinuria for predicting cardiovascular events: a Japanese cardiovascular hospital database analysis

Initial screening for proteinuria by urine dipstick test (UDT) may be useful for predicting clinical outcomes. The Shinken Database includes all the new patients visiting the Cardiovascular Institute Hospital in Tokyo, Japan. Patients for whom UDT was performed at their initial visit between 2004 and 2010 (n = 7131) were divided into three groups according to the test results: negative, trace, and positive (1+ to 4+) proteinuria. During the mean follow-up period of 3.4 years, 233 (3.1%) deaths, 255 (3.6%) heart failure (HF) events, and 106 (1.5%) ischemic stroke (IS) events occurred. Prevalence of atherothrombotic risks increased with an increase in the amounts of proteinuria. The incidence of all-cause death, HF and IS events increased significantly from negative to trace to positive proteinuria groups (log rank test, P for trend < 0.001). Multivariate analysis revealed independent association between proteinuria and all-cause death [hazard ratio (HR): 1.50, 95% confidence interval (CI) 1.07-2.10], HF (HR: 1.55, 95% CI 1.14-2.12), and IS (HR: 2.08, 95% CI 1.26-3.45). Even trace proteinuria was independently associated with HF (HR: 1.64, 95% CI 1.07-2.53) and IS (HR: 2.17, 95% CI 1.14-4.11) and with all-cause death (HR: 1.56, 95% CI 0.99-2.47). In conclusions, dipstick proteinuria was independently associated with cardiovascular events and death, suggesting that the UDT is a useful tool for evaluating patients' risk for such adverse events.

Blood Pressure and Left Ventricular Hypertrophy in Patients on Different Peritoneal Dialysis Regimens

Objective

To examine the relation between the results of ambulatory 24-hour blood pressure monitoring (ABPM) and left ventricular mass index (LVMI), then to find the independent determinant for left ventricular hypertrophy (LVH) in peritoneal dialysis (PD) patients. Finally, to evaluate the differences in the clinical and cardiovascular characteristics between patients on continuous ambulatory PD (CAPD) and continuous cyclic PD (CCPD).

Design

An open, nonrandomized, cross-sectional study.

Setting

Divisions of nephrology and cardiology in a medical center.

Patients

Thirty-two uremic patients on maintenance PD therapy (22 patients on CAPD, and 10 on CCPD) without anatomical heart disease or history of receiving long-term hemodialysis.

Interventions

Home blood pressure (BP) and office BP were measured using the Korotkoff sound technique by sphygmomanometer. ABPM was employed for continuous measurement of BP. Echocardiography was performed for measurement of cardiac parameters and calculation of LVMI.

Main Outcome Measures

Multivariate logistic regression analysis was performed for independent determinant of LVH in PD patients. The differences in clinical and cardiovascular characteristics between CAPD and CCPD patients were compared.

Results

Simple regression analysis showed positive correlations between LVMI and the duration of hypertension, ambulatory nighttime BP/BP load/BP load > 30%, serum phosphate, calcium–phosphate product, ultrafiltration (UF) volume, and percentage of UF volume during the nighttime. A negative correlation was noted between LVMI and dipping. In multiple regression analysis, the duration of hypertension was the only variable linked to LVMI. In multivariate logistic regression analysis, only ambulatory nighttime systolic BP load > 30% had an independent association with LVH. There were correlations between office/home BP and ambulatory 24-hour BP. In addition, CCPD patients had higher LVMI, UF volume during the nighttime, and percentage of UF volume during the nighttime than those of CAPD patients.

Conclusions

In this study, ambulatory nighttime systolic BP load > 30% had an independent association with LVH. Office and home BP measurements were correlated with ABPM in PD patients. The result that CCPD patients had a higher LVMI than CAPD patients may be due to a relative volume overload during the daytime in CCPD patients.

Effect of Intradialytic Exercise on Hyperphosphatemia and Malnutrition

Intradialytic exercise (IDE) is not routinely prescribed in hemodialysis (HD) units despite its potential benefits on patients' outcomes. This study was the first in the United Arab Emirates to examine the effect of aerobic IDE on hyperphosphatemia, malnutrition, and other health outcomes among HD patients. Participants were chosen from the largest HD unit in Sharjah Emirate for a quasi-experimental intervention with pre and post evaluation. The study lasted for 12 months. Study parameters were collected at baseline, post intervention, and follow-up. The intervention included a moderate-intensity aerobic IDE of 45 min per HD session; intensity was assessed using the Borg Scale. Patients were educated on the importance of exercise. Study outcomes were serum phosphorus (P), malnutrition inflammation score (MIS), quality of life (QOL), and pertinent blood tests. Forty-one eligible consenting HD patients were included in the study. Results at follow-up showed a non-significant reduction in P (p = 0.06) in patients who were hyperphosphatemic at baseline, but not in the sample as whole. MIS did not deteriorate throughout the study (p = 0.97). IDE resulted in a non-significant increase in the QOL visual analogue scale (p = 0.34). To conclude, aerobic IDE for 45 min is safe and could be beneficial, especially for hyperphosphatemic patients.

Vascular Calcification in Chronic Kidney Disease: The Role of Inflammation

Cardiovascular complications are extremely frequent in patients with chronic kidney disease (CKD) and death from cardiac causes is the most common cause of death in this particular population. Cardiovascular disease is approximately 3 times more frequent in patients with CKD than in other known cardiovascular risk groups and cardiovascular mortality is approximately 10-fold more frequent in patients on dialysis compared to the age- and sex-matched segments of the nonrenal population. Among other structural and functional factors advanced calcification of atherosclerotic plaques as well as of the arterial and venous media has been described as potentially relevant for this high cardiovascular morbidity and mortality. One potential explanation for this exceedingly high vascular calcification in animal models as well as in patients with CKD increased systemic and most importantly local (micro)inflammation that has been shown to favor the development of calcifying particles by multiple ways. Of note, local vascular upregulation of proinflammatory and proosteogenic molecules is already present at early stages of CKD and may thus be operative for vascular calcification. In addition, increased expression of costimulatory molecules and mast cells has also been documented in patients with CKD pointing to a more inflammatory and potentially less stable phenotype of coronary atherosclerotic plaques in CKD.

Uremic Toxicity: Present State of the Art

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Electrolytes and Fluid Management in Hemodialysis and Peritoneal Dialysis

The kidney is a complex and vital organ, regulating the electrolyte and fluid status of the human body. As hemodialysis (HD) and peritoneal dialysis (PD) are forms of renal replacement therapy and not an actual kidney, they do not possess the same physiologic regulation of both fluid and electrolytes. Precise regulation of fluid and electrolytes in the HD and PD population remains a constant challenge. In this review, fluid status of both HD and PD will be examined, as well as sodium, potassium, phosphorous, and calcium. Each electrolyte will be analyzed by its physiological significance, the complications that arise when a proper balance cannot be maintained, and methods to correct these imbalances. An overview of the fluid compartments and volume of distribution within the body will be discussed. Ultrafiltration, a modality used in both forms of renal replacement therapy, will be defined, along with its impact on fluid status. Fluid assessment will be addressed, along with proper maintenance of fluid homeostasis. By having an understanding of the pathophysiology behind the fluid and electrolyte abnormalities that occur in end-stage renal disease, one can direct proper management with medications, diet, and alterations in dialysis to provide patients with the most optimal form of renal replacement therapy available.

Assessment of some cardiovascular risk factors in predialysis chronic kidney disease patients in Southern Nigeria

BACKGROUND

Cardiovascular risk factors are responsible for cardiovascular disease and rapid progression of chronic kidney disease (CKD) to end-stage renal disease. Prompt evaluation, modification, and treatment of these factors in predialysis patients will reduce morbidity and mortality. This study assessed some cardiovascular risk factors in predialysis CKD patients in a tertiary hospital in Southern Nigeria.

PATIENTS AND METHODS

This was a case-control study that involved 76 consecutive predialysis CKD patients and 38 age-and sex-matched controls without CKD over 1 year period. Both groups were assessed for cardiovascular risk factors, and comparisons were made. A P value of <0.05 was taken as significant.

RESULTS

The mean ages of the CKD versus control group were 48.00 ± 15.28 versus 45.34 ± 15.35 years. The male:female ratio was 1.7:1 for both groups. The common etiologies of CKD in this study were hypertension 30 (39.5%), diabetes mellitus 23 (30.3%), and chronic glomerulonephritis 19 (25%). There were 38 (50%) in CKD stage 3, 31 (40.8%) in CKD stage 4, and 7 (9.2%) in CKD stage 5. The common cardiovascular risk factors found in the CKD versus control were hypertension (96.1% vs. 42.1%), anemia (96.1% vs. 23.7%), left ventricular hypertrophy (77.6% vs. 23.7%), dyslipidemia (67.1% vs. 39.5%), hypocalcemia (60.1% vs. 18.5%), hyperphosphatemia (63.2% vs. 0%), and hyperuricemia (57.9% vs. 15.8%). These risk factors were significantly higher in CKD group. Hyperphosphatemia and hypoalbuminemia significantly increased across CKD stages 3-5. Anemia was significantly more common in males whereas dyslipidemia was more common in female CKD patients.

CONCLUSION

Cardiovascular risk factors were highly prevalent in predialysis CKD subjects even in early stages. Hypoalbuminemia and hyperphosphatemia significantly increased across the CKD stages 3-5 whereas anemia and dyslipidemia showed significant gender differences. Cardiovascular risk factors should be treated early in predialysis CKD patients.

Evaluation of morbidity and mortality data related to cardiovascular calcification from calcium-containing phosphate binder use in patients undergoing hemodialysis

Cardiovascular disease is the leading cause of death among patients with stage 5 chronic kidney disease. Several mechanisms are thought to contribute to vascular calcification and subsequent cardiovascular disease in patients who require hemodialysis. One of these mechanisms is the use of calcium-containing phosphate binders to treat hyperphosphatemia. Although most phosphate binding occurs in the gastrointestinal tract, some calcium is inevitably absorbed and has the potential to perpetuate the calcium-phosphorus product and the development of vascular and soft tissue calcification. Some phosphate binders such as sevelamer hydrochloride do not contain calcium and therefore may not carry the same risks. We examined the cardiovascular calcification effect and morbidity and mortality data with calcium-containing phosphate binders compared with sevelamer hydrochloride when given to patients with stage 5 chronic kidney disease for the treatment of hyperphosphatemia. A literature search using the MEDLINE and PubMed databases identified relevant articles from 1989-2009; nine studies compared vascular calcification between a calcium-containing phosphate binder and sevelamer hydrochloride. Three mortality studies were also identified. Seven of the nine studies reported a statistically significant increase in vascular calcification in patients taking calcium-containing phosphate binders as measured by coronary artery calcification scores and aortic calcification scores. In two trials, lower mortality rates were observed in the patients receiving sevelamer hydrochloride compared with calcium-containing phosphate binders. No significant difference in the mortality rate was observed in the third trial. Based on the current literature, it appears that calcium-containing phosphate binders promote the progression of vascular calcification to a greater extent than does sevelamer hydrochloride. In addition, some evidence suggests that sevelamer hydrochloride may reduce all-cause mortality rates in patients undergoing hemodialysis, particularly those aged 65 years or older. Thus, although sevelamer hydrochloride appears to be the more appropriate choice of phosphate binder for patients undergoing hemodialysis in whom cardiovascular calcification is a concern, more clinical trials are needed to further guide practitioners on the selection of phosphate binders.

Elevated serum phosphate predicts mortality in renal transplant recipients

BACKGROUND

High serum phosphate has been identified as an important contributor to the vascular calcification seen in patients with chronic kidney disease (Block et al., Am J Kidney Dis 1998; 31: 607). In patients on hemodialysis, elevated serum phosphate levels are an independent predictor of mortality (Block et al., Am J Kidney Dis 1998; 31: 607; Block, Curr Opin Nephrol Hypertens 2001; 10: 741). The aim of this study was to investigate whether an elevated serum phosphate level was an independent predictor of mortality in patients with a renal transplant.

METHODS

Three hundred seventy-nine asymptomatic renal transplant recipients were recruited between June 2000 and December 2002. Serum phosphate was measured at baseline and prospective follow-up data were collected at a median of 2441 days after enrolment.

RESULTS

Serum phosphate was significantly higher in those renal transplant recipients who died at follow-up when compared with those who were still alive at follow-up (P<0.001). In Kaplan-Meier analysis, serum phosphate concentration was a significant predictor of mortality (P=0.0001). In multivariate Cox regression analysis, serum phosphate concentration remained a statistically significant predictor of all-cause mortality after adjustment for traditional cardiovascular risk factors, estimated glomerular filtration rate, and high sensitivity C reactive protein (P=0.036) and after adjustment for renal graft failure (P=0.001).

CONCLUSIONS

The results of this prospective study are the first to show that a higher serum phosphate is a predictor of mortality in patients with a renal transplant and suggest that serum phosphate provides additional, independent, prognostic information to that provided by traditional risk factors in the risk assessment of patients with a renal transplant.

Pharmacological control of secondary hyperparathyroidism in chronic hemodialysis patients: cinacalcet is coming to Japan

Secondary hyperparathyroidism has a significant impact on morbidity and mortality due to skeletal and extraskeletal manifestations. Cinacalcet, a newly developed calcimimetic, is reported to decrease parathyroidism, as well as serum levels of phosphorus (P) and calcium (Ca) and therefore Ca x P product. Available evidence has shown that cinacalcet decreases the rate of parathyroidectomy and bone fracture in hemodialysis patients, but the death rate remains the same. Although, it is not yet available in Japan, cinacalcet is expected to be available as a possible drug for patients undergoing hemodialysis due to secondary hyperparathyroidism associated with refractory hyperphosphatemia and hypercalcemia. Except for the high cost, cinacalcet will be a welcome therapeutic option for end-stage renal disease and probably also for pre-end-stage renal disease patients. Dietary phosphate restriction and adequate hemodialysis, however, are still the main strategy for the control of hyperphosphatemia and secondary hyperparathyroidism.

Anaesthesia for renal transplant surgery

Renal transplantation is the preferred therapeutic option for patients with end-stage renal disease. Survival rates are much higher in patients who receive a transplant. Patients with renal failure have significant concomitant medical conditions, such as cardiovascular disease. This article provides an overview of the important issues to be considered in patients undergoing renal transplant, and discusses the anaesthetic management of these patients.

Effects of parathyroidectomy on bone remodeling markers and vitamin D status in patients with chronic kidney disease–mineral and bone disorder

BACKGROUND/AIMS

Chronic renal failure (CRF) is often associated with bone disorders including chronic kidney disease-mineral and bone disorder (CKD-MBD). Parathyroid hormone (PTH) has a relationship to bone remodeling, and so this study was undertaken to evaluate changes in bone remodeling markers after parathyroidectomy (PTX).

METHODS

Twelve adult patients, mean age 43.4 +/- 12.7 years, of both genders, were evaluated, prior to and six months after PTX. Analysis of biochemical markers of bone metabolism, such as total and ionized calcium, phosphorus, 25(OH)D(3), total alkaline phosphatase (TAP), bone-specific alkaline phosphatase (BAP), intact PTH, osteoprotegerin (OPG), and tartrate-resistant acid phosphatase isoform 5b (TRAP), were measured.

RESULTS

No changes were observed after PTX in the serum total and ionized calcium, TAP, BAP, and 25(OH)D(3). After surgery there was a significant decrease in serum phosphorus, iPTH, and TRAP (P < 0.001). No significant change was observed in OPG; however there was a positive correlation between OPG and 25(OH)D(3) before and after surgery (r = 0.774, P = 0.014; and r = 0.706, P = 0.01, respectively). The percentage of patients with vitamin D deficiency decreased from 16.7% to 8.3%, while those with sufficient levels increased from 41.7% to 58.3%.

CONCLUSION

The small number of patients in the study notwithstanding, the present study is unique because it provides information on bone metabolism and vitamin D status six months after PTX. The removal of parathyroid glands significantly decreased bone resorption and indicated a tendency of 25(OH)D(3) concentration to increase. However, the precise role of OPG and BAP in the improvement in bone remodeling in patients with CKD-MBD requires further study.

Body composition changes in haemodialysis patients with secondary hyperparathyroidism after parathyroidectomy measured by conventional and vector bioimpedance analysis

Considering the negative effects of secondary hyperparathyroidism (SHPT) in patients with chronic renal failure (CRF), the objective of the present study was to evaluate body composition changes using conventional and vector bioimpedance analysis in patients before and after parathyroidectomy (PTX). Twelve adult patients, mean age 43·4 (sd 12·7) years, were evaluated prior to and 6 months after PTX. Diets were assessed with 3d dietary records, and mean energy, protein, calcium and phosphorus intake were estimated from these inventories. Weight, height, BMI and bioelectrical impedance were measured; and biochemical markers of nutritional status (albumin and total protein) and bone metabolism (calcium, phosphorus and intact parathyroid hormone) were determined. No significant differences were observed in mean energy, protein and phosphorus after surgery. There was a significant increase in calcium intake after PTX (382·3 (sd 209·6) mg to 656·6 (sd 313·8) mg;P<0·05). Mean weight, BMI, conventional bioelectrical impedance measurements, total body fat, lean body mass and total body water were unaffected by surgery. However, the phase angle and reactance significantly increased after PTX (5·0° (sd 1·4) to 5·6° (sd 1·3); 44·1 (sd 15·6) Ω to 57·1 (sd 14·4) Ω, respectively). The high levels of intact parathyroid hormone before surgery had a negative effect on total body fat (r−0·69,P<0·05). After PTX, the mean albumin significantly increased (3·9 (sd 0·4) g/dl to 4·2 (sd 0·6) g/dl;P<0·05). PTX for SHPT is associated with certain changes in laboratory values, dietary intake and body composition. The latter is best seen with bioimpedance vector analysis.

Intensified and daily hemodialysis in children might improve statural growth

In children conventional hemodialysis does not often improve growth. We determined linear growth in five children on in-center intensified and daily hemodialysis (IDd) regimen, with a mean age of 8 years 7 months at enrollment. Four of five were on growth hormone started for a median of 28.5 months before IDd. IDd was delivered 5 to 6 times weekly, for three hours each session. Mean follow up of IDd was 18.6 months. Dropout from IDd was kidney transplantation (n=4) or transfer to another center (n=1). IDd and free diet improved appetite, thereby protein intake, was above 2 g/kg/BW. Median weekly Kt/V(urea) was 9.1 (8.7 to 10.4). Predialysis phosphorus blood levels were higher at the start (2.04+/-0.34 mmol/L) than at end of IDd (1.39+/-0.41 mmol/L) without need for carbonate of calcium in four of five cases. During conventional dialysis ht SDS decreased from -0.8 to -1.44, which occurred predominantly before rhGH start. Conversion to IDd significantly increased growth velocity to a mean of 13 cm/year (10.3-18) with a mean change of +1.84 ht SDS/year (0.4 to 2.7). This preliminary report suggests the potential efficacy of IDd regimen in promising growth velocity, either directly from a higher dialysis dose or indirectly through an improved nutritional status.

Mild Hyperphosphatemia and Mortality in Hemodialysis Patients

BACKGROUND

Severe hyperphosphatemia (serum phosphate level > 6.5 mg/dL [>2.10 mmol/L]) has been associated directly with increased overall and cardiovascular mortality in hemodialysis (HD) patients. Currently, clinical guidelines recommend maintaining phosphate levels within normal range (3.0 to 5.0 mg/dL [0.97 to 1.61 mmol/L]). However, mild hyperphosphatemia (phosphate, 5.01 to 6.5 mg/dL [1.62 to 2.10 mmol/L]) is still to be addressed as an independent mortality risk factor in HD patients.

METHODS

The association between serum phosphate level and survival in maintenance HD patients was explored prospectively in 385 incident patients from 1990 to 2001. Cox regression was performed using phosphate level as: (1) a continuous variable; (2) stratified as low phosphate level (<3 mg/dL [<0.97 mmol/L]), normal phosphate level (3.0 to 5.0 mg/dL [0.97 to 1.61 mmol/L]), mild hyperphosphatemia (phosphate, 5.01 to 6.5 mg/dL [1.62 to 2.10 mmol/L]), or severe hyperphosphatemia (phosphate > 6.5 mg/dL [>2.10 mmol/L]); and (3) phosphate level greater or less than 5.0 mg/dL (> or <1.61 mmol/L).

RESULTS

As a continuous variable, relative risk (RR) for mortality for serum phosphate level was 1.26 (confidence interval [CI], 1.09 to 1.47) after adjusting for age, sex, diabetes, Kt/V, albumin level, hemoglobin level, serum calcium level, normalized protein catabolic rate, and parathyroid hormone level. Compared with a normal phosphate level, mild hyperphosphatemia showed an adjusted mortality RR of 1.94 (CI, 1.17 to 3.19), and severe hyperphosphatemia, an RR of 2.02 (CI, 1.10 to 3.73). Patients with a phosphate level cutoff value greater than 5.0 mg/dL (>1.61 mmol/L) showed a 2-fold increase in adjusted RR for mortality compared with those with a phosphate level of 5.0 mg/dL or less (< or =1.61 mmol/L; RR, 2.11; CI, 1.44 to 3.08).

CONCLUSION

A serum phosphate level greater than 5.0 mg/dL (>1.61 mmol/L) is independently associated with an increased risk for death in HD patients.

Calcification and cardiovascular problems in renal failure

Extraosseus calcification has plagued management of renal failure since the beginning of hemodialysis, but the issue has largely been neglected because the impact on survival was thought to be limited. The recent recognition that hyperphosphatemia is a strong predictor of all-cause mortality, and particularly of cardiac mortality, has transformed the situation. Relatively stringent, though difficult to implement, guidelines have been proposed for the management of hyperphosphatemia. Important recent insights document that, for different reasons, both high and low turnover of bone disease increase the risk of vascular calcifications. Vascular calcification impacts cardiac death not only by complicating coronary atherosclerosis, but also by increasing the stiffness of central arteries, impacting on heart function (increased impedance, reduced coronary perfusion). While in the past extraosseous calcification, including vascular calcification, was thought to be a passive process resulting from transgression of a critical Ca x P product, recent studies show that the adverse effect of hyperphosphatemia is also mediated by active processes (e.g., induction of "osteogenic" genetic programs), and is modulated by calcification inhibitors.

Low water-soluble uremic toxins

The uremic syndrome is the result of the retention of solutes, which under normal conditions are cleared by the healthy kidneys. Uremic retention products are arbitrarily subdivided according to their molecular weight. Low-molecular-weight molecules are characterized by a molecular weight below 500 D. The purpose of the present publication is to review the main water soluble, nonprotein bound uremic retention solutes, together with their main toxic effects. We will consecutively discuss creatinine, glomerulopressin, the guanidines, the methylamines, myo-inositol, oxalate, phenylacetyl-glutamine, phosphate, the polyamines, pseudouridine, the purines, the trihalomethanes, and urea per se.

Differential management of cardiovascular disease in ESRD by nephrologists and cardiologists

BACKGROUND

Mortality and morbidity from cardiovascular disease are high in patients with end-stage renal disease (ESRD). The cardiovascular profile of patients with ESRD may differ from that of the general population. We examined how nephrologists and cardiologists differ in managing hypertension and cardiovascular disease in patients with ESRD.

METHODS

Seven cases incorporating relevant clinical and echocardiographic findings common to this population were developed based on a chart review of an ESRD population. Each ESRD case incorporated a clinical presentation designed to test for a specific dichotomous response to a common and important clinical problem. Nine nephrology and 7 cardiology faculty members, each paired with a senior clinical fellow from the discipline, were surveyed.

RESULTS

Nephrologists were less likely than cardiologists to initiate beta-blockade in patients with echocardiographic evidence of regional wall motion abnormalities if there was no history of coronary artery disease (CAD; P < 0.01). In patients with known CAD, cardiologists were more likely than nephrologists to intensify antihypertensive therapy, even in the setting of a history of fractures associated with orthostatic hypotension (P < 0.02). Decision making did not differ between subspecialists in the management of left ventricular hypertrophy, congestive heart failure, or diastolic dysfunction.

CONCLUSION

Nephrologists and cardiologists differ in their management of hypertension in the presence of ischemic heart disease in the ESRD population. Only limited data specific to the ESRD population are available to assess which approach is superior. The discipline-driven differential management approaches observed emphasize the need for better evidence-based management strategies for this population.

Percutaneous ethanol (PEIT) and calcitrol (PCIT) injection therapy are ineffective in treating severe secondary hyperparathyroidism

BACKGROUND

Secondary hyperparathyroidism (2HPT) is a frequent complication of long-term dialysis treatment and, despite recent advances in medical therapy, surgical parathyroidectomy (PTX) is required in a considerable number of uraemic patients. Recently, other modalities of therapy, such as ultrasound-guided percutaneous parathyroid injection of ethanol (PEIT) or of calcitriol (PCIT), have been used to treat refractory 2HPT. Our objectives were to evaluate the efficacy of these therapeutic modalities and to analyse their effects on parathyroid cell proliferation.

METHODS

Nineteen haemodialysis patients with severe 2HPT were studied. Ten underwent PEIT (Group I) and nine underwent PCIT (Group II). After treatment, five patients in each group were submitted to PTX. Parathyroid cell proliferation was appraised at the beginning and at the end of the study by fine-needle aspiration biopsy, making use of immunocytochemical testing for Ki-67. The surgically removed glands were submitted to histopathological analysis and cellular proliferation was evaluated.

RESULTS

Both PEIT and PCIT proved inefficient in controlling 2HPT. Comparing study onset with day 60, both groups showed a significant decrease in serum-ionized calcium: 5.3+/-0.3 vs 5.1+/-0.5 mg/dl (P = 0.03) in Group I and 5.5+/-0.4 vs 5.4+/-0.3 mg/dl (P = 0.03) in Group II. Other laboratory parameters were unchanged. There was a significant, although transitory, enlargement in glandular volume in Group II at day 30 when compared with study onset (1.5+/-0.6 vs 1.7+/-0.7 cm(3), P = 0.02). When comparing the two groups, Group I showed a glandular volume smaller than that of Group II at days 30 (1+/-0.5 vs 1.7+/-0.7 cm(3), P = 0.003), 60 (0.8+/-0.4 vs 1.5+/-0.9 cm(3), P = 0.006) and 90 (0.8+/-0.5 vs 1+/-0.7 cm(3), P = 0.02). Cellular proliferation, which was equally elevated in both groups at the beginning of the study, could not be evaluated at the end due to lack of material. The majority of glands obtained through PTX presented intensive cellular proliferation and contained areas of nodular hyperplasia, even those glands with a volume of <0.5 cm(3).

CONCLUSION

In our experience, both PCIT and PEIT were unable to control severe 2HPT in chronic haemodialysis patients. We believe that the severity of the 2HPT in the study patients, in conjunction with the fact that we excluded from treatment parathyroid glands with a volume of <0.5 cm(3), were the most important causes of this failure.

Percutaneous ethanol injection treatment of severe hyperparathyroidism in maintenance dialysis: risks and benefits

Renal hyperparathyroidism is one of the main and serious complications that occur in chronic kidney disease and particularly during long-term maintenance dialysis. Several recent trials indicate that a high calcium phosphorus product is correlated with high cardiovascular morbidity and mortality and poor outcome. Thus, it is important to improve the control of hyperparathyroidism in chronic renal failure patients. Several methods have been reported for treating severe hyperparathyroidism resistant to medical therapy. Total parathyroidectomy and transplantation or excision of tumor is considered as the treatment of choice. More recently, interventional methods with percutaneous ethanol or calcitriol injection have been developed. These latter techniques have been reported as an alternative to surgical treatment for patients with high perioperative risk. We report the occurrence of laryngeal recurrent nerve palsy, vocal fold paralysis, and hemiplegia after a successful injection of ethanol in a left parathyroid adenoma in a maintenance hemodialysis patient and discuss the restrictions of the procedure and alternative treatments in view of the available studies.

The Consequences of Uncontrolled Secondary Hyperparathyroidism and Its Treatment in Chronic Kidney Disease

Secondary hyperparathyroidism (HPT) is a common complication of chronic kidney disease (CKD) and a frequent cause of clinically significant bone disease. Soft-tissue and vascular calcification, cardiovascular disease, and calcific uremic arteriolopathy (CUA) are additional serious consequences of the disorder that may contribute directly to cardiovascular morbidity and mortality in patients with CKD. Less widely appreciated manifestations include neurological disturbances, hematological abnormalities, and endocrine dysfunction. Secondary HPT arises from alterations in calcium, phosphorus, and vitamin D metabolism that develop early in the course of CKD and become more pronounced as kidney function declines. Treatment is often delayed, however, until the disease is well established. Current therapeutic strategies rely largely on the use of vitamin D sterols to diminish excess parathyroid hormone (PTH) synthesis and to lower serum or plasma PTH levels, but their use is often confounded by increases in serum calcium and phosphorus concentrations, changes that can aggravate soft-tissue and vascular calcification. As such, there is a need for new therapeutic interventions that can effectively lower serum or plasma PTH levels without producing untoward side effects. The current review summarizes the diverse manifestations of secondary HPT in patients with CKD. The consequences of inadequately controlled secondary HPT and the adverse effects of selected therapeutic interventions for the disorder on vascular calcification and cardiovascular disease in those with CKD are discussed.

Time and exercise improve phosphate removal in hemodialysis patients

BACKGROUND

Control of serum phosphate remains a difficult clinical issue in most hemodialysis (HD) patients. This study examines 2 nonpharmacological approaches to improving phosphate control in HD patients.

METHODS

First, 9 stable HD patients underwent dialysis in random fashion for either 4 hours 3 times weekly or 5 hours 3 times weekly. Adjustments were made to blood flow rates such that Kt/V was the same for all sessions, thus allowing independent assessment of the influence of time. The primary end point was weekly dialysate phosphate removal. In the second study, 12 different patients underwent an exercise program in which they pedaled a bicycle ergometer either immediately before or during dialysis. Again, weekly dialysate phosphate removal was measured.

RESULTS

In the time study, urea reduction ratio (69% +/- 0.02% versus 68% +/- 0.07, 4 versus 5 hours) and weekly urea removal were no different between the 2 groups. However, weekly phosphate removal (3,007 +/- 641 versus 3,400 +/- 647 mg; P < 0.02) significantly improved with longer dialysis duration. Serum phosphate levels improved, but did not reach statistical significance in this short-term study. In the exercise study, weekly phosphate removal improved with exercise, but did not reach significance (2,741 +/- 715 [no exercise] versus 2,917 +/- 833 [exercise predialysis] versus 2,992 +/- 852 mg [exercise during dialysis]; P = 0.055), although comparing only exercise during dialysis with no exercise reached significance (P = 0.02). There was no significant difference in serum phosphate levels.

CONCLUSION

Both increased dialysis time and exercise result in increased dialytic removal of phosphate and could be expected in the long term to improve phosphate control.

Hyperphosphataemia in renal failure: causes, consequences and current management

Hyperphosphataemia is prevalent among chronic renal failure and dialysis patients. It is known to stimulate parathyroid hormone and suppress vitamin D3 production, thereby inducing hyperparathyroid bone disease. In addition, it may independently contribute to cardiac causes of death through increased myocardial calcification and enhanced vascular calcification. Hyperphosphataemia is also associated with cardiac microcirculatory abnormalities. Therefore, phosphate control is of prime importance. It is important to control phosphate levels early in the course of chronic renal failure in order to avoid and treat secondary hyperparathyroidism, and cardiovascular and soft tissue calcifications. Dietetic restrictions are often difficult to follow long term. Because of its large sphere of hydration and the complex kinetics of phosphate elimination, phosphate is not easily removed by dialysis. Long, slow dialysis may be effective, but this needs logistics and acceptance by patients. Thus, oral phosphate binders are generally required to control serum levels. None of the existing phosphate binding agents is truly satisfactory. Aluminium-containing agents are highly efficient but many clinicians have abandoned their use because of the potential toxicity. Despite of the wide use of calcium-containing agents, there was a link with hypercalcaemia and soft tissue calcifications. Novel phosphate binders in the form of polyallylamine hydrochloride, polyuronic acid derivatives and lanthanum carbonate appear promising. In this review, we discuss causes of hyperphosphataemia, pathological consequences and modalities of treatment.

The uremic syndrome: therapeutic-evaluative discordance

Significant discordances are observed between the therapeutic needs of patients with end-stage renal disease and the current emphasis in renal science and technologies. These discordances manifest in the observation that renal replacement therapies fail to attenuate the impact of the patient status at the time of initiation of renal replacement on mortality and morbidity; in the failure to apply a rigorous approach for fluid management, despite its technical simplicity; in the inadequacy of dialysis in the correction of deficient excretion of some solutes (phosphate and potassium), and in the greater impact of hormonal replacement on outcome than that observed by dialytic techniques. We suggest that these discordances find their root in the limited spectrum of uremic solute removal that is currently available with various dialytic techniques, and we suggest that a re-examination of the therapeutic targets in dialytic therapy may be needed in order to supercede the therapeutic plateau at which the therapy is currently fixed.

Cardiovascular disease in patients with chronic kidney disease

Cardiovascular disease (CVD) is the major cause of morbidity and mortality in patients with renal failure. Patients with chronic kidney disease have significant CVD, and carry a high cardiovascular burden by the time they commence renal replacement therapy (RRT). The severity of CVD that has been observed in dialysis patients lead to a growing body of research examining the pathogenesis and progression of CVD during the progression of chronic kidney disease (CKD) to end-stage renal disease (ESRD) (ie, predialysis phase). Multiple factors are involved in the development of CVD in CKD. More importantly, critical and key factors seem to develop early in the course of CKD, and result in preventable worsening of CVD in this patient population. Anemia is common in patients with CKD, and has been shown to have an independent role in the genesis of left ventricular hypertrophy (LVH) and subsequent CVD. Unfortunately, it is underdiagnosed and undertreated in patients with CKD. Early intervention, and better correction of anemia, seems to gain a great momentum in the prevention and management of CVD in CKD. Hypertension is another risk factor that has been targeted by the National Kidney Foundation Task Force on CVD in chronic kidney disease. This article reviews the different factors involved in the pathogenesis of CVD in CKD and the evidence supporting early and aggressive intervention.

Influence of progressive renal dysfunction in chronic heart failure

Chronic heart failure (CHF) is often associated with impaired renal function due to hypoperfusion. Such patients are very sensitive to changes in renal perfusion pressure, and may develop acute tubular necrosis if the pressure falls too far. The situation is complicated by the use of diuretics, ACE inhibitors and spironolactone, all of which may affect renal function and potassium balance. Chronic renal failure (CRF) may also be associated with fluid overload. Anaemia and hypertension in CRF contribute to the development of left ventricular hypertrophy (LVH), which carries a poor prognosis, so correction of these factors is important.

Online hemodiafiltration versus acetate-free biofiltration: a prospective crossover study

Online hemodiafiltration (online HDF) and acetate-free biofiltration (AFB) are 2 innovative renal replacement therapies. Convincing evidence has shown that both techniques are superior to conventional hemodialysis in many aspects. The aim of the present investigation was to compare online HDF and AFB in 12 stable maintenance hemodialysis patients in a prospective, randomized crossover trial. Twelve stable dialysis patients, age 49.7 +/- 11.3 years and on dialysis for 83.5 +/- 76.7 months, were treated prospectively and randomly by either AFB, predilution HDF (pre-HDF), or postdilution HDF (post-HDF) for a total of 36 weeks using exclusively F60S high-flux dialyzers. Routine blood biochemical tests, bone metabolism parameters, and clearance for both small and larger molecular weight substances were measured at defined intervals. During the trial period inter- and intradialysis symptoms, e.g., hypotensive episodes and intradialysis arterial blood gas analyses, were recorded. Both online HDF and AFB were well accepted by the overwhelming majority of patients and also by the dialysis staff. Pretreatment sodium, total and ionized calcium, chloride, bicarbonate, and urea did not differ within or between the 3 treatment groups. Potassium increased slightly in HDF patients while phosphate and beta2-microglobulin (beta2-M) decreased in all groups. After dialysis, AFB patients exhibited a significantly higher bicarbonate concentration and lower potassium level when identical potassium concentrations in dialysate were used. Patients receiving AFB manifested less intradialysis partial pressure of oxygen drop and partial pressure of carbon dioxide rise than those on HDF treatments. HDF treatments could afford higher single-pool and double-pool Kt/V, higher effective urea and beta2M clearance, and lower total interdialysis symptom scores than the AFB treatment method. While bone metabolism parameters did not differ between the 3 dialysis modalities, some parameters such as deoxypyridinoline in HDF and osteocalcin, pyridinoline, and deoxypyridinoline in AFB deteriorated at the end of the crossover study. Aluminum concentration decreased progressively to about one-third of prestudy values at the end of the study with all 3 treatments. AFB was associated with a lower predialysis mean arterial pressure (MAP), a smaller drop in MAP during treatment, and similar hypotension episodes compared with the 2 HDF treatments. Albumin concentration showed a trend to decrease during the first 2 months of the trial period followed by a slight increase thereafter but still significantly lower than initial value at the end of crossover. Both online HDF and AFB share most of the features of optimal renal replacement therapy. Online HDF is superior to AFB in such aspects as increased delivered dialysis dose both for small and larger molecular weight toxins and less interdialysis symptoms. On the other hand, AFB is associated with a smaller effect on arterial blood gas values and improved intradialysis hemodynamic tolerance. Some dialysis-related symptoms and complications in the case of our AFB practice could be attributable, at least in part, to low dialysate calcium level.

Compounds in development to combat hyperphosphataemia

Hyperphosphataemia in haemodialysis patients is associated with secondary hyperparathyroidism and more importantly with an increased cardiovascular mortality in dialysed patients. Removal of phosphate during dialysis is less than net intestinal uptake. This imbalance results in a positive phosphate balance. To control serum phosphate concentration oral phosphate binders have to be taken to reduce net intestinal uptake. The use of classical phosphate binders such as calcium carbonate, calcium acetate and aluminium-containing phosphate binders is limited by their side effects. Hypercalcaemia aggravates vascular calcification and cardiovascular risk. Aluminium intoxication causes aluminium osteopathy, anaemia and encephalopathy. Therefore, the development of calcium- and aluminium free phosphate binders has become a challenge to clinical nephrology. Polyallylamine hydrochloride (sevelamer) is one of the new alternative compounds which has been shown to effectively bind phosphate in dialysis patients. A promising approach in the development of alternative phophate binders are trivalent-iron (Fe(III)) containing phosphate binders. They were not only successfully tested in experimental animals but have also been shown to reduce urinary phosphate excretion and serum phosphate concentrations in patients with preterminal failure and those on maintenance haemodialysis. This review outlines the experimental and clinical data on Fe-III based phosphate binders providing evidence that they will be as effective and safe as phosphate binders without the major side effects of classical phosphate-binding compounds.

Coronary artery disease in uremia: Etiology, diagnosis, and therapy

Cardiovascular disease is a major challenge to nephrologists, whether we deal with patients with pre-end-stage renal failure, on dialysis or after successful renal transplantation. It is the most common cause for death in patients with a functional allograft, and prevents many dialysis patients from being engrafted. Coronary artery disease is a diagnostic and therapeutic challenge, as it differs in some respects from that seen in non-uremic cohorts, and lacks much of the evidence-base on which therapeutic intervention rests. This review examines the experimental and clinical literature on cardiovascular disease in uremia, focusing on coronary artery disease. We focus on the incidence, presenting syndromes, screening tools, and interventions in the context of acute and chronic coronary syndromes. Recent evidence comparing coronary angioplasty, coronary artery stenting, and bypass surgery in subjects with renal failure is also reviewed. Coronary artery disease is more prevalent in uremia, more difficult to diagnose and less rewarding to treat compared to non-uremic subjects. Many more randomized trials are needed. In the absence of information from such trials, we advocate aggressive control of conventional and novel cardiovascular risk factors, and early intervention for symptomatic coronary disease.

Arterial changes in paediatric haemodialysis patients undergoing renal transplantation

BACKGROUND

The relationship between primary renal disease and arterial wall changes in paediatric haemodialysis patients has been little studied. The aim of the present work was to determine the influence of primary renal disease on arterial wall pathology in uraemic paediatric patients.

METHODS

Twelve paediatric haemodialysis patients (seven girls, five boys) aged 11-17 years were included in the study. The primary renal diseases were urinary malformations in six patients (uropathy group) and acquired glomerular diseases (glomerulopathy group) in six patients. Age, sex distribution, duration of chronic renal failure, duration of haemodialysis, blood pressure, serum glucose, triglycerides, cholesterol, fibrinogen, calcium, phosphorus and parathyroid hormone levels were compared. Internal iliac artery samples were obtained at the time of related-donor renal transplantation. Artery samples were fixed in formaldehyde and sections were stained separately with haematoxylin and eosin, Orcein, Verhoef-van Gieson, and Masson trichrome.

RESULTS

Five arteries had fibrous or fibroelastic intimal thickening, medial mucoid ground substance and disruption of the internal elastic lamella. Two of these had microcalcification in the intimal layer; another two demonstrated atheromatous plaques; the remaining five were normal. These pathological changes were found in the arteries of all six patients with uropathy, whereas of the six patients with glomerulopathy only one had arterial changes (P<0.001). The duration of chronic renal failure was 4.8+/-1.9 years in the uropathy group and 2.2+/-1.2 in the glomerulopathy group (P<0.05). The two groups were comparable in terms of serum glucose, triglycerides, cholesterol, fibrinogen, calcium, and parathyroid hormone levels, presence of hypertension, sex distribution, and duration of haemodialysis. Plasma phosphorus and the calcium x phosphate product were higher in the uropathy group than in the glomerulopathy group (P<0.05).

CONCLUSIONS

This study demonstrated that pathological changes are common in the arteries of uraemic paediatric patients, and that calcification and atherosclerosis are integral to this disease process. In our study, these alterations were more common in the patients with uropathy. We speculate that the patients with uropathy are more prone to these alterations due to slower progression and a longer duration of renal insufficiency.

Non-invasive assessments of cardiovascular disease in patients with renal failure

Vascular calcification is common in patients with chronic renal failure, and it may contribute to the very high mortality rate from cardiovascular causes in the end-stage renal disease population. Vascular calcification in chronic renal failure can arise from the calcification of the intimal layer of arteries as a result of atherosclerosis or from medial wall calcification due largely to alterations in mineral metabolism. Although several reports indicate that coronary artery calcification, as measured by electron-beam computed tomography, is quite common in patients with end-stage renal disease who are treated with dialysis, the clinical significance of these findings remain uncertain. In the general population, electron-beam computed tomography evidence of coronary calcification serves as a useful index of atherosclerotic burden and has value as a predictor of adverse coronary events. The relationship between coronary artery calcification and atherosclerotic cardiovascular disease has not been adequately studied, however, in patients with end-stage renal disease, and calcification scores in this population may reflect both intimal and medial wall calcification. Assessments using coronary angiography are needed to determine the diagnostic value of electron-beam computed tomography as a predictor of atherosclerotic cardiovascular disease in patients with chronic renal failure. Nevertheless, electron-beam computed tomography makes it possible to detect the presence and monitor the progression of coronary calcification in those undergoing long-term dialysis. The technique may provide important information about the impact of new therapeutic strategies aimed at reducing the risks of vascular calcification in those with chronic renal failure.

Management of disturbed calcium metabolism in uraemic patients: 1. Use of vitamin D metabolites

Chronic renal failure is characterized by diminished synthesis of, and resistance to, the active vitamin D metabolite 1,25-dihydroxy-vitamin D3 (1,25(OH)2D3, calcitriol). Calcitriol results from the biotransformation of the precursor 25-hydroxy-vitamin D3 (25(OH)D3) to 1,25(OH)2D3. 25(OH)D3 is synthesized in the liver, and 1alpha-hydroxylase, the rate-limiting enzyme for its biotransformation into the most active metabolite, 1,25(OH)2D3, is located in the kidney. The regulation of 1alpha-hydroxylase in renal failure is not well known. Recent work indicates that, in contrast to previous opinion, 1alpha-hydroxylase is predominantly expressed not in the proximal tubule but in the distal tubule [1]. In vivo, the main stimulatory signal is presumably parathyroid hormone (PTH) and the main inhibitory signal hyperphosphataemia. Both signals are altered in renal failure. There is also evidence that the renal 1alpha-hydroxylase becomes substrate-dependent in patients with renal failure. This means that a higher concentration of the precursor 25(OH)2D3 will result in a higher rate of transformation into the active metabolite 1,25(OH)2D3 in renal patients. Calcitriol is not exclusively synthesized in the kidney, but may also be synthesized in extra-renal tissues, e.g. activated monocytes/macrophages [2], particularly in granuloma [3] as shown by anephric uraemic patients who develop hypercalcaemia and elevated calcitriol concentrations when sarcoidosis [4] or tuberculosis [5] supervenes. On the other hand, calcitriol is less effective in uraemia. This may be to some extent due to diminished expression of vitamin D receptors [6], particularly in parathyroid glands when they undergo nodular transformation [7], but there may also be resistance to calcitriol at the post-receptor level [8]. In a series of elegant experiments [9,10], calcitriol resistance has been related to disturbed genomic effects of active vitamin D because the interaction of the vitamin D receptor ligand complex with vitamin D-responsive elements (VDREs) upstream of vitamin D-regulated genes was disturbed by the action of low molecular weight substances in uraemia, which have not been completely characterized. The role of genetically determined polymorphisms of the vitamin D receptor in the genesis of disturbed calcium metabolism of renal failure is currently unclear.

Cardiovascular disease determinants in chronic renal failure: clinical approach and treatment

INTRODUCTION

Cardiovascular disease (CVD), as the leading cause of morbidity and mortality in patients on renal replacement therapy (RRT), has a central role in everyday nephrological practice.

METHODS

Consensus was reached on key points relating to the clinical approach and treatment of the main cardiovascular risk factors in RRT patients (hypertension, anaemia, hyperparathyroidism, dyslipidaemia, new emerging risk factors). In addition, the role of convective treatments on cardiovascular outcomes was examined.

RESULTS

Hypertension should be managed by aiming at blood pressure values of < or =140/90 mmHg (< or =160/90 mmHg in the elderly), firstly by ensuring target dry body weight is achieved. No single class of drug has proved superior to others in RRT patients, provided that the blood pressure target is achieved, although ACE inhibitors have shown specific organ protection in high-risk patients (HOPE study) and are well tolerated. Anaemia should be managed by using erythropoietin and iron supplements, aiming at haemoglobin levels of 12 g/dl and keeping serum ferritin levels < 500 ng/ml. The management of hyperparathyroidism is currently unsatisfactory, as calcium supplements have the potential to increase cardiovascular calcification. While awaiting new calcium- and aluminium-free phosphate binders, it is essential to ensure dialysis adequacy. Clinical studies are in progress to assess the real impact of lipid-lowering drugs in RRT. In the meantime, serum LDL-cholesterol < 160 mg/dl and triglycerides < 500 mg/dl may be desirable targets. The impact of new emerging risk factors (inflammation and chronic infection, hyperhomocysteinaemia, metabolic waste-product accumulation) and their proper management are still under research. Convective dialysis treatments may confer some degree of protection from dialysis-related amyloidosis and mortality, but clinical data on this important issue are still controversial and no definitive conclusions can be drawn at present.

CONCLUSION

CVD prevention and treatment is a great challenge for the nephrologist. Achieving evidence-based consensus can help in encouraging the implementation of best clinical practice in line with the progress of current knowledge.

Phosphate removal and hemodialysis conditions

Hyperphosphatemia is frequently found in hemodialysis patients, and the association with an increased risk of mortality has been demonstrated. Other authors have linked hyperphosphatemia to increased cardiovascular mortality. The normalization of phosphate plasma levels is therefore an important goal in the treatment of end-stage renal disease patients. Absorption of phosphate from the food exceeds the elimination through a hemodialysis treatment, and this leads to a chronic phosphate load for the majority of hemodialysis patients. This imbalance should be improved by either a reduction of phosphate absorption or an increased removal of phosphate. A reduction of phosphate absorption can be achieved by reducing the amount of phosphate in the diet or by the administration of phosphate binders. Unfortunately, these measures imply practical difficulties, for example, a lack of patient compliance or other side effects. When considering modifications of the hemodialysis treatment, an essential understanding of the kinetics of dialytic phosphate removal is mandatory. Phosphate is unevenly distributed in different compartments of the body. Only a very small amount of phosphate is present in the easily accessible plasma compartment. The major part of phosphate removed during hemodialysis originates from the cytoplasm of cells. A transfer from intracellular space to the plasma and further from the plasma to the dialysate is necessary. However, if we consider improvement to phosphate removal by dialysis procedures, full dialyzer clearance is effective in only the initial phase of the dialysis treatment. After this initial phase, the transfer rate for phosphate from the intracellular space to the plasma becomes the rate-limiting step for phosphate transport. Attempts to improve this transfer rate have recently been investigated by acidosis correction, but turned out not to be consistently successful. Furthermore, modifications of the treatment schedule have been described in the literature as measures to influence the phosphate balance consistently. Successful improvements of the phosphate balance can be achieved specifically through increasing the frequency of the dialysis treatments.

Parathormon, calcium, phosphorus, and left ventricular structure and function in normotensive hemodialysis patients

Clinical and experimental data suggest that Parathormon (PTH), calcium, and phosphorus participate in left ventricular hypertrophy (LVH) and affect myocardial contractility in end-stage renal disease. Cellular calcium overload and interstitial fibrosis induced by PTH may lead to impairment of left ventricular diastolic function. Hyperphosphatemia is an independent risk of cardiovascular mortality in dialysis patients. The aim of the study was to estimate the influence of PTH and calcium-phosphorus metabolism on left ventricular structure and function in hemodialysis patients, without hypertension and antihypertensive drug therapy (SBP = 126.2 +/- 11.1 DBP = 75.8 +/- 6.5 mmHg). Echocardiographic findings in a group of 22 normotensive HD patients had been compared to 43 hypertensive HD patients. Relationships between PTH, calcium-phosphorus metabolism and echocardiography in normotensive group were then evaluated. Left ventricular mass index (LVMI) was lower in normotensive patients: 128.3 +/- 46.2 versus 165.8 +/- 46.7 (p < 0.01). The prevalence of LVH was 55% in normotensive HD patients compared to 86% in hypertensive group (p < 0.01). In normotensive group we found correlation between PTH and LVMI (r = 0.44; p < 0.05). There were also significant relationships between calcium and posterior wall thickness (r = -0.44; p < 0.05), phosphorus and LVMI (r = 0.47; p < 0.05). A significant correlation was observed between both phosphorus, calcium x phosphorus product and E/A ratio: r = -0.47 and r = -0.43, respectively (p < 0.05 both). Disturbances of calcium-phosphorus metabolism and secondary hyperparathyroidism contributes to left ventricular hypertrophy, and impaired left ventricular diastolic function in normotensive hemodialysis patients.

Lipid Metabolism and Cardiovascular Morbidity and Mortality in Hemodialysis Patients: Role of Factors Modulating Cytosolic Calcium

Animal studies indicate that insulin resistance and glucose intolerance leading to dyslipidemia in uremic rats are associated with increased cytosolic calcium ([Ca⁺⁺ i]). The resistance and intolerance are reversed with verapamil, but recur after its discontinuation. This finding suggests that hyperparathyroid-induced [Ca ⁺⁺ i] increase is responsible for the metabolic derangement. We retrospectively examined, over a 12-year period, the effects of factors that lower [Ca ⁺⁺ i] on total serum cholesterol and triglycerides in 332 hemodialysis (HD) patients. Because the study was retrospective, detailed lipid profiles were not available. We therefore relied on morbidity and mortality outcomes related to atherosclerotic vascular disease. Patients with diabetes mellitus were excluded, because their dyslipidemia and vascular disease are mediated via a different mechanism. Four groups emerged: group I [high parathormone (PTH) in the absence of calcium channel blockers (CCBs), n = 107], representing the highest [Ca⁺⁺ i]; group II (high PTH in the presence of CCBs, n = 76) and group III (lower PTH in the absence of CCBs, n = 66), representing intermediate [Ca ⁺⁺ i]; and group IV (lower PTH in the presence of CCBs, n = 83) representing the lowest [Ca ⁺⁺ i]. The theoretically lower [Ca ⁺⁺ i] was achieved via CCB therapy or lower PTH, or both. The mean serum cholesterol in group I was 322 ± 24 mg/dL and the level of triglycerides was 398 ± 34 mg/dL. Group II had mean serum cholesterol of 196 ± 16 mg/dL and triglycerides of 157 ± 17 mg/dL. Group III had a mean serum cholesterol of 202 ± 19 mg/dL and triglycerides of 160 ± 15 mg/dL. Group IV had a mean serum cholesterol of 183 ± 9 mg/dL and triglycerides of 94 ± 6 mg/dL. The differences in cholesterol and triglyceride levels among four groups were significant (p < 0.001) by one-way analysis of variance (ANOVA). The incidence of cardiovascular morbidity and mortality events was 61% in group I, 24% in group II, 28% in group III, and 18% in group IV (χ ² = 47.7, p < 0.001). We conclude that, in non diabetic HD patients, hyperparathyroidism, especially in the absence of CCBs, is associated with severe dyslipidemia and increased risk of cardiovascular morbidity and mortality. Dyslipidemia may be related to a hyperparathyroid-induced increase in cytosolic calcium [Ca⁺⁺ i]. Lowering [Ca⁺⁺ i] by decreasing PTH or by blocking calcium entry into cells (via CCBs), or both, is associated with less dyslipidemia and improved long-term cardiovascular morbidity and mortality. Prospective randomized studies, with actual measurement of [Ca ⁺⁺ i], are needed to verify the results of this study.

Vitamin D therapy in patients with chronic renal disease: the role of the renal dietitian

Chronic renal failure causes decreased vitamin D production, which profoundly alters parathyroid hormone (PTH) metabolism, and calcium and phosphorus balance. Correcting this deficiency is an important strategy in managing secondary hyperparathyroidism (SHPT) and helping to restore mineral balance. However, hypercalcemia and hyperphosphatemia are common side effects that hamper vitamin D hormone therapy by increasing dietary calcium and phosphorus absorption. This limitation has led to the development of D-hormone analogs that retain the ability to suppress PTH levels without causing drastic changes in calcium and phosphorus metabolism. These analogs have the potential to advance the management of SHPT. Renal dietitians can play a leading role in ensuring successful management of SHPT by participating in early patient intervention for abnormal mineral and vitamin D metabolism, by encouraging long-term phosphorus control, and by updating and implementing clinical protocols that promote optimal hormone levels (D and PTH), mineral levels (phosphorus and calcium), and nutritional factors.