The impact of low and high dialysate calcium concentrations on cardiovascular disease and death in patients undergoing maintenance hemodialysis: a systematic review and meta-analysis

BACKGROUND

The optimal dialysate calcium (Ca) concentration for patients undergoing hemodialysis remains inconclusive, particularly concerning cardiovascular protection.

METHODS

We conducted a systematic review of 19 randomized controlled trials (RCTs) and a meta-analysis of eight RCTs to determine the optimal dialysate Ca concentration for cardiovascular protection. We compared outcomes in patients receiving maintenance hemodialysis treated with either a low-Ca dialysate (LCD) (1.125 or 1.25 mmol/L) or a high-Ca dialysate (HCD) (1.5 or 1.75 mmol/L). The outcomes were coronary artery calcification score (CACS), all-cause and cardiovascular death, cardiovascular function and structure, and serum biochemical parameters.

RESULTS

There was no significant difference between LCD and HCD concerning CACS (standardized mean difference [SMD] = -0.16, 95% confidence interval [CI]: [-0.38, 0.07]), the risk of all-cause death, and cardiovascular death in patients treated with chronic maintenance hemodialysis. Conversely, LCD was associated with a significantly lower intima-media thickness (SMD = -0.49, 95% CI [-0.94, -0.05]) and pulse wave velocity than HCD (SMD = -0.86, 95% CI [-1.21, -0.51]). Furthermore, LCD significantly decreased serum Ca levels (mean difference [MD] = 0.52 mg/dL, 95% CI [0.19, 0.85]) and increased serum parathyroid hormone levels (MD = 44.8 pg/mL, 95% CI [16.2, 73.3]) compared with HCD. Notably, most RCTs examined in our analysis did not include patients receiving calcimimetics.

CONCLUSIONS

Our meta-analysis showed no significant differences in cardiovascular calcification and death between LCD and HCD and revealed a paucity of RCTs on dialysate Ca concentrations, including those involving patients on calcimimetics, indicating the urgent need for further studies.

Can we reverse arterial stiffness by intervening on CKD-MBD biomarkers?

The increased cardiovascular risk of chronic kidney disease may in part be the consequence of arterial stiffness, a typical feature of kidney failure. Deranged homeostasis of minerals and hormones involved (CKD-MBD), are also strongly associated with this increased risk. It is well established that CKD-MBD is a main driver of vascular calcification, which in turn worsens arterial stiffness. However, there are other contributors to arterial stiffness in CKD than calcification. An overlooked possibility is that CKD-MBD may have detrimental effects on this potentially better modifiable component of arterial stiffness. In this review, the individual contributions of short-term changes in calcium, phosphate, PTH, vitamin D, magnesium, and FGF23 to arterial stiffness, in most studies assessed as pulse wave velocity, is summarized. Indeed, there is evidence from both observational studies and interventional trials that higher calcium concentrations can worsen arterial stiffness. This, however, has not been shown for phosphate, and it seems unlikely that, apart from being a contributor to vascular calcification and having effects on the microcirculation, phosphate has no acute effect on large artery stiffness. Several interventional studies, both by infusing PTH and by abrupt lowering PTH by calcimimetics or surgery, virtually ruled out direct effects on large artery stiffness. A well-designed trial using both active and nutritional vitamin D as intervention found a beneficial effect for the latter. Unfortunately, the study had a baseline imbalance and other studies did not support its finding. Both magnesium and FGF23 do not seem do modify central arterial stiffness.

Triiodothyronine and Protein Malnutrition Could Influence Pulse Wave Velocity in Pre-Dialysis Chronic Kidney Disease Patients

Cardiovascular diseases (CVD) are the first cause of chronic kidney disease (CKD) mortality. For personalized improved medicine, detecting correctable markers of CVD can be considered a priority. The aim of this study was the evaluation of the impact of nutritional, hormonal and inflammatory markers on brachial-ankle Pulse Wave Velocity (PWV) in pre-dialysis CKD patients. A cross-sectional observational study was conducted on 68 pre-dialysis CKD patients (median age of 69 years, 41.2% with diabetes mellitus, 52.9% male). Laboratory data were collected, including levels of prolactin, triiodothyronine, TGF α, IL-6, and IL-1β. The high values of brachial-ankle PWV were associated with reduced muscle mass (p = 0.001, r = -0.44), low levels of total cholesterol (p = 0.04, r = -0.26), triglycerides (p = 0.03, r = -0.31), triiodothyronine (p = 0.04, r = -0.24), and prolactin (p = 0.02, r = -0.27). High PWV was associated with advanced age (p < 0.001, r = 0.19). In the multivariate analysis, reduced muscle mass (p = 0.018), low levels of triiodothyronine (p = 0.002), and triglycerides (p = 0.049) were significant predictors of PWV, but age (p < 0.001) remained an important factor. In conclusion, reduced triiodothyronine together with markers of malnutrition and age were associated with PWV in pre-dialysis CKD patients.

Why is Intradialytic Hypotension the Commonest Complication of Outpatient Dialysis Treatments?

Intradialytic hypotension (IDH) is the most frequent complication of hemodialysis (HD) treatments with a frequency of 10% to 12% for patients with chronic kidney disease attending for outpatient treatments and is associated with both temporary ischemic stress to vital organs, including the heart and brain, and increased patient mortality. Although there have been many different definitions of IDH over the years, an absolute nadir systolic blood pressure (SBP) has the strongest association with patient outcomes. The unifying pathophysiology is one of reduced effective blood volume, resulting in lower plasma tonicity, and if this cannot be adequately compensated for by activation of neurohumeral systems, then arteriolar tone and blood pressure fall. The risk factors for developing IDH are numerous, ranging from patient-related factors, including age and comorbidity with reduced cardiac reserve, to patient compliance with dietary and lifestyle advice, to reactions with the extracorporeal circuit and medications, choice of dialysate composition and temperature, setting of postdialysis target weight, ultrafiltration rate, and profiling. Advances in dialysis machine technology by providing real time estimates of the effective circulating volume and adjusting dialysate composition to maintain vascular tonicity are being developed, but currently require more sophisticated biofeedback loops to be clinically effective in preventing IDH. While awaiting advances in artificial intelligence, the clinician continues to rely on patient education to limit interdialytic weight gains, frequent assessment of the postdialysis target weight, adjusting dialysate composition and temperature, introducing convective therapies to increase thermal losses, and altering dialysis session duration and frequency to reduce ultrafiltration rate requirements.

CYP17A1-ATP2B1 SNPs and Gene-Gene and Gene-Environment Interactions on Essential Hypertension

Background: The association between the CYP17A1 and ATP2B1 SNPs and essential hypertension (referred to as hypertension) is far from being consistent. In addition to the heterogeneity of hypertension resulting in inconsistent results, gene–gene and gene–environment interactions may play a major role in the pathogenesis of hypertension rather than a single gene or environmental factor.

Methods: A case–control study consisting of 1,652 individuals (hypertension, 816; control, 836) was conducted in Maonan ethnic minority of China. Genotyping of the four SNPs was performed by the next-generation sequencing technology.

Results: The frequencies of minor alleles and genotypes of four SNPs were different between the two groups (p < 0.001). According to genetic dominance model analysis, three (rs1004467, rs11191548, and rs17249754) SNPs and two haplotypes (CYP17A1 rs1004467G-rs11191548C and ATP2B1 rs1401982G-rs17249754A) were negatively correlated, whereas rs1401982 SNP and the other two haplotypes (CYP17A1 rs1004467A-rs11191548T and ATP2B1 rs1401982A-rs17249754G) were positively associated with hypertension risk (p ≤ 0.002 for all). Two best significant two-locus models were screened out by GMDR software involving SNP–environment (rs11191548 and BMI ≥ 24 kg/m²) and haplotype–environment (CYP17A1 rs1004467G-rs11191548C and BMI ≥ 24 kg/m²) interactions (p ≤ 0.01). The subjects carrying some genotypes increased the hypertension risk.

Conclusions: Our outcomes implied that the rs1004467, rs11191548, and rs17249754 SNPs and CYP17A1 rs1004467G-rs11191548C and ATP2B1 rs1401982G-rs17249754A haplotypes have protective effects, whereas the rs1401982 SNP and CYP17A1 rs1004467A-rs11191548T and ATP2B1 rs1401982A-rs17249754G haplotypes showed adverse effect on the prevalence of hypertension. Several SNP–environment interactions were also detected.

Does Pulse Wave Velocity Increase Over Time in Hemodialysis Patients?

OBJECTIVES

Arterial stiffness, measured by pulse wave velocity (PWV), is reported to be increased in hemodialysis (HD) patients and increases cardiovascular mortality. Previous studies have reported an association between extracellular water (ECW) and PWV. We wished to review whether PWV increases over time and whether this is associated with ECW.

METHODS

We reviewed repeat aortic PWV measurements using an oscillograph method along with corresponding ECW measured by multifrequency bioimpedance in HD patients a minimum of 5 years apart.

RESULTS

Twenty-four patients (16 [66.7%] male and 11 [45.8%] diabetic, mean age 61.7 ± 15.2 years) had PWV and ECW initially measured after 46 (26-124) months of HD and then after 112 (97-202) months. Overall, there was no change in PWV or ECW (9.4 ± 2.2 vs. 8.1 ± 2.5 cm/s; 14.7 ± 2.5 vs. 15.2 ± 2.9 L, respectively), whereas the ECW/total body water ratio increased (0.399 ± 0.015 vs. 0.408 ± 0.021, p < 0.05). We found no association between changes in PWV and ECW (r = -0.05, p = 0.84), whereas there was an association with the change in peri-dialytic systolic blood pressure (SBP) (r = 0.59, p = 0.007).

CONCLUSION

In our small observational study, there was no overall change in PWV, after 5 years of HD, with PWV increasing in 50% and falling in 50%. Changes in PWV were not associated with changes in ECW but were associated with changes in peri-dialytic SBP. Our study demonstrates that PWV does not increase in all HD patients with time, and interventional studies are required to determine whether targeted blood pressure control reduces PWV in HD patients.

Cardiovascular Risk Assessment Using Ultrasonographic Surrogate Markers of Atherosclerosis and Arterial Stiffness in Patients With Chronic Renal Impairment: A Narrative Review of the Evidence and a Critical View of Their Utility in Clinical Practice

PURPOSE OF THE REVIEW

Validated tools to improve cardiovascular disease (CVD) risk assessment and mortality in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) are lacking. Noninvasive measures of arteriosclerosis and subclinical atherosclerosis such as pulse wave velocity (PWV) and carotid intima-media thickness (cIMT), respectively, have emerged as promising risk stratification tools and potential modifiable biomarkers. Their wide use as surrogate markers in clinical research studies is based on the strong pathophysiological links with CVD. However, whether their effect as risk stratification or intervention targets is superior to established clinical approaches is uncertain. In this review, we examine the evidence on the utility of PWV, cIMT, and plaque assessment in routine practice and highlight unanswered questions from the clinician's perspective.

SOURCES OF INFORMATION

Electronic databases PubMed and Google Scholar were searched until February 2020.

METHODS

This narrative review is based on peer-reviewed meta-analyses, national and international societies' guidelines, and on focused critical review of recent original studies and landmark studies in the field.

KEY FINDINGS

Although patients with CKD are considered in the high-risk CVD groups, there is still need for tools to improve risk stratification and individualized management strategies within this group of patients. Carotid intima-media thickness is associated with all-cause mortality, CVD mortality, and events in CKD and hemodialysis cohorts. However, the evidence that measurement of cIMT has a clinically meaningful role over and above existing risk scores and management strategies is limited. Plaque assessment is a better predictor than cIMT in non-CKD populations and it has been incorporated in recent nonrenal-specific guidelines. In the CKD population, one large observational study provided evidence for a potential role of plaque assessment in CKD similar to the non-CKD studies; however, whether it improves prediction and outcomes in CKD is largely understudied. Pulse wave velocity as a marker of arterial stiffness has a strong pathophysiological link with CVD in CKD and numerous observational studies demonstrated associations with increased cardiovascular risk. However, PWV did not improve CVD reclassification of dialysis patients when added to common risk factors in a reanalysis of ESRD cohorts with available PWV data. Therapeutic strategies to regress PWV, independently from blood pressure reduction, have not been studied in well-conducted randomized trials.

LIMITATIONS

This study provides a comprehensive review based on extensive literature search and critical appraisal of included studies. Nevertheless, formal systematic literature review and quality assessment were not performed and the possibility of selection bias cannot be excluded.

IMPLICATIONS

Larger, prospective, randomized studies with homogeneous approach, designed to answer specific clinical questions and taking into consideration special characteristics of CKD and dialysis, are needed to study the potentially beneficial role of cIMT/plaque assessment and PWV in routine practice.

Changes in aortic pulse wave velocity in peritoneal dialysis do not mirror changes in extracellular water measured by bioimpedance

BACKGROUND

Pulse wave velocity is a measurement of arterial stiffness and associated with increased cardiovascular mortality. Previous reports in peritoneal dialysis have linked increased pulse wave velocity with an expansion in extracellular water. As cardiovascular mortality is increased in peritoneal dialysis patient, we wished to determine whether changes in pulse wave velocity mirrored changes in extracellular water.

METHODS

We repeated aortic pulse wave velocity and bioimpedance-derived extracellular water measurements in peritoneal dialysis patients attending for assessment of peritoneal membrane function.

RESULTS

Sixty-six patients, 41 males (62.1%), mean age of 66.2 ± 13.9 years, median duration of peritoneal dialysis treatment (14.3 (3.1-31.9) months) had repeated measurement 6.4 (5.8-10.2) months apart, with no significant change in aortic pulse wave velocity (10.1 ± 3.2 to 9.9 ± 2.8 m/s). In univariate analysis, the initial aortic pulse wave velocity was associated with extracellular water (r = 0.26, p = 0.034) and serum N-terminal pro brain-type natriuretic peptide (r = 0.25, p = 0.04), and on follow-up, aortic pulse wave velocity with N-terminal pro brain-type natriuretic peptide (r = 0.31, p = 0.01). Aortic pulse wave velocity increased in 50% of patients, and these patients had greater serum C-reactive protein 3(2-10) versus 2(1-4) mg/L, and ferritin (778(444-1099) versus 585(313-811), p < 0.05), but there were no differences in either absolute or adjusted extracellular water. Both log C-reactive protein (odds ratio 4.7 (95% confidence limits 1.3-17.1), p = 0.019) and prescription of calcium channel blockers (odds ratio 4.9 (95% confidence limits 1.2-19.1), p = 0.024) were independently associated with an increase in aortic pulse wave velocity.

CONCLUSION

We did not find an independent association between a change in aortic pulse wave velocity and extracellular water, suggesting that changes in aortic stiffness in peritoneal dialysis patients are more complex than simply following changes in extracellular water.

A Systematic Review and Meta-analysis of Nonpharmacologic-based Interventions for Aortic Stiffness in End-Stage Renal Disease

Introduction

Increased carotid-femoral pulse wave velocity (cf-PWV) in end-stage renal disease (ESRD) indicates enhanced aortic stiffness and mortality risk. We conducted a systematic review and meta-analysis of nonpharmacologic interventions in adults with ESRD to determine their effects on cf-PWV, systolic blood pressure (SBP), and intervention-associated adverse events.

Methods

MEDLINE, EMBASE, and EBM databases were searched. Study screening, selection, data collection, and methodological quality assessments were performed by 2 independent reviewers. Pooled-effect estimates from mean differences and 95% confidence intervals (CIs) were calculated using random effect models.

Results

A total of 2166 subjects with ESRD from 33 studies (17 randomized; 16 nonrandomized) were included. Four intervention-comparator pairs were meta-analyzed. Quality of evidence ranged from very low to moderate. Kidney transplantation decreased cf-PWV (−0.70 m/s; CI: –1.3 to −0.11; P = 0.02) and SBP (−8.3 mm Hg; CI: −13.2 to −3.3; P < 0.001) over pretransplantation. In randomized trials, control of fluid overload by bio-impedance reduced cf-PWV (−1.90 m/s; CI: −3.3 to −0.5); P = 0.02) and SBP (−4.3 mm Hg; CI: −7.7 to −0.93); P = 0.01) compared with clinical assessment alone. Cross-sectional studies also demonstrated significantly lower cf-PWV and SBP in normovolemia compared with hypervolemia (P ≤ 0.01). Low calcium dialysate decreased cf-PWV (−1.70 m/s; CI: −2.4 to −1.0; P < 0.00001) without affecting SBP (−1.6 mm Hg; CI: −8.9 to 5.8; P = 0.61). Intradialytic exercise compared with no exercise reduced cf-PWV (−1.13 m/s; CI: −2.2 to −0.03; P = 0.04), but not SBP (+0.5 mm Hg; CI: −9.5 to 10.4); P = 0.93).

Conclusions

Several nonpharmacologic interventions effectively decrease aortic stiffness in ESRD. The impact of these interventions on cardiovascular outcomes and mortality risk reduction in ESRD requires further study.

Chronic Kidney Disease and Pulse Wave Velocity: A Narrative Review

Chronic kidney disease (CKD) is associated with excess cardiovascular mortality, resulting from both traditional and nontraditional, CKD-specific, cardiovascular risk factors. Nontraditional risk factors include the entity Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) which is characterised by disorders of bone and mineral metabolism, including biochemical abnormalities of hyperphosphatemia and hyperparathyroidism, renal osteodystrophy, and vascular calcification. Increased arterial stiffness in the CKD population can be attributed amongst other influences to progression of vascular calcification, with significant resultant contribution to the cardiovascular disease burden. Pulse wave velocity (PWV) measured over the carotid-femoral arterial segments is the noninvasive gold-standard technique for measurement of aortic stiffness and has been suggested as a surrogate cardiovascular end-point. A PWV value of 10 m/s or greater has been recommended as a suitable cut-off for an increased risk of cardiovascular mortality. CKD is a risk factor for an excessive rate of increase in aortic stiffness, reflected by increases in PWV, and increased aortic PWV in CKD shows faster progression than for individuals with normal kidney function. Patients with varying stages of CKD, as well as those on dialysis or with a kidney transplant, have different biological milieu which influence aortic stiffness and associated changes in PWV. This review discusses the pathophysiology of arterial stiffness with CKD and outlines the literature on PWV across the spectrum of CKD, highlighting that determination of arterial stiffness using aortic PWV can be a useful diagnostic and prognostic tool for assessing cardiovascular disease in the CKD population.

Aortic pulse wave velocity is greater in peritoneal dialysis patients with lower dual energy X-ray absorptiometry (DXA) femoral neck bone mineral density

BACKGROUND

Increased vascular stiffness is associated with low bone mineral density (BMD) in the general population, and both are risk factors for mortality. We wished to determine whether vascular stiffness is associated with BMD in peritoneal dialysis (PD) patients.

METHODS

We measured vascular stiffness by aortic pulse wave velocity (aPWV), BMD by dual electron absorptiometry (DXA) scanning, and body composition using bioimpedance.

RESULTS

We reviewed DXA scans in 125 PD patients, 56.8% male, mean age 64.4 ± 15.3 years, mean aPWV, 10.2 ± 2.6 m/s. We divided patients by aPWV (< 10 and > 10 m/s), and there were no statistical differences in patient demographics, body composition, PD adequacy, peritoneal and urinary calcium losses. On univariate analysis aPWV was negatively associated with total body T score (r = - 0.20, p = 0.037). On multivariable logistic regression patients with higher aPWV were prescribed fewer non-calcium containing phosphate binders, odds ratio (OR) 0.83, 95% confidence interval (CI) 0.70-0.99, p = 0.039, more had lower 25 hydroxy-vitamin D₃ concentrations < 50 ng/L (OR 0.34, CI 0.12-0.93, p = 0.035, and lower femoral BMD OR 0.03 (CI 0-0.3.4), p = 0.029, but there was no association with total or lumbar spine BMD.

CONCLUSION

Our study reinforces the hypothesis of a link between bone disease and vascular disease in dialysis patients. As patients with higher aPWV were prescribed fewer non-calcium containing phosphate binders and fewer had higher 25 hydroxy-vitamin D₃ concentrations, then this raises the possibility that differences in clinical practice and drug prescribing may help to reduce vascular stiffness, which will require testing in future trials.

Long-term effects of low calcium dialysates on the serum calcium levels during maintenance hemodialysis treatments: A systematic review and meta-analysis

Hypercalcemia and hyperparathyroidism in patients receiving maintenance hemodialysis (MHD) can cause the progression of cardiovascular diseases (CVD) and mineral bone disorders (MBD). The KDIGO recommends the dialysates with a calcium (Ca) concentration of 1.25–1.5 mmol/L for MHD treatments, but the optimal concentration remains controversial. Here, we conducted a systematic review and a meta-analysis of seven randomized controlled trials examining a total of 622 patients to investigate the optimal concentration for MHD for 6 months or longer. The dialysates with a low Ca concentration (1.125 or 1.25 mmol/L) significantly lowered the serum Ca and raised the intact parathyroid hormone levels by 0.52 mg/dL (95% confidence interval, 0.20–0.85) and 39.59 pg/mL (14.80–64.38), respectively, compared with a high Ca concentration (1.50 or 1.75 mmol/L). Three studies showed that a low concentration was preferred for lowering arterial calcifications or atherosclerosis in different arteries, but one study showed that coronary arterial calcifications increased with a low concentration. Two studies showed contradictory outcomes in terms of MBD. Our meta-analysis showed that a dialysate with a low Ca concentration lowered the serum Ca levels in patients receiving long-term MHD, but further studies are needed to determine the optimal Ca concentration in terms of CVD and MBD.

The influence of low calcium dialysate on left ventricular diastolic function in peritoneal dialysis patients

Left ventricular (LV) diastolic function was found to be a significant predictor of cardiovascular events and general mortality in dialysis. Studies have indicated that dialysate calcium concentrations were significantly associated with cardiac function. However, the relationship between low calcium dialysate and LV diastolic function has not been clear. The aim of this study was to investigate the influence of low calcium dialysate on cardiac function in peritoneal dialysis (PD) patients. A total of 60 PD patients were enrolled in this study, with a calcium content of the PD solution of 1.25 mmol/L in 30 patients (low-calcium group) and 1.75 mmol/L in 30 patients (standard-calcium group). Standard M-mode and two-dimensional ultrasound measurements were applied to detect the cardiac function. After 12-month follow-up, we found no significant difference in blood pressure, calcium, phosphorus, parathyroid hormone (PTH), etc., between the two groups. Residual renal function (RRF), which is associated with LV cardiac function, was significantly decreased in the standard-calcium group compared with the low-calcium group (5.64 ± 3.23 vs. 9.38 ± 3.17, p = .001). Compared with the low-calcium group, E_max (peak early diastolic velocity) and A_max (peak late diastolic velocity) were significantly decreased (p < .05), whereas myocardial performance index (MPI) was obviously increased in standard-calcium group (9.69 ± 2.71 vs. 7.75 ± 0.93, p < .05). In conclusion, our data suggest that low calcium dialysate treatment is significantly associated with better LV diastolic function.

Low versus high dialysate calcium concentration in alternate night nocturnal hemodialysis: A randomized controlled trial

INTRODUCTION

Higher calcium dialysate is recommended for quotidian nocturnal hemodialysis (NHD) (≥6 nights/week) to maintain bone health. It is unclear what the optimal calcium dialysate concentration should be for alternate night NHD. We aimed to determine the effect of low calcium (LC) versus high calcium (HC) dialysate on cardiovascular and bone parameters in this population.

METHODS

A randomized controlled trial where participants were randomized to LC (1.3 mmol/L, n = 24) or HC dialysate (1.6 or 1.75 mmol/L, n = 26). Primary outcome was change in mineral metabolism markers. Secondary outcomes included change in vascular calcification (VC) scores [CT abdominal aorta (AA) and superficial femoral arteries (SFA)), pulse wave velocity (PWV), bone mineral density (BMD) and left ventricular mass index (LVMI) over 12 months.

FINDINGS

In the LC group, pre-dialysis ionised calcium decreased -0.12 mmol/L (-0.18-0.06, P = 0.0001) and PTH increased 16 pmol/L (3.5-28.5, p = 0.01) from baseline to 12 months with no significant change in the HC group. In both groups, there was no progression of VC in AA or SFA and no change in PWV, LVMI or BMD. At 12 months, calcimimetics were prescribed in a higher percentage in the LC vs. HC groups (45.5% vs. 10.5%) with a lower proportion of the HC group being prescribed calcitriol (31.5% vs. 72%).

DISCUSSION

Although dialysate calcium prescription influenced biochemical parameters it was not associated with difference in progression of VC between HC and LC groups. An important finding was the potential impact of alternate night NHD in attenuating progression of VC and inducing stabilisation of LVMI and PWV.

Impact of Dialysate Calcium Concentration on Clinical Outcomes in Incident Hemodialysis Patients

The association between dialysate calcium (DCa) concentration and mortality in hemodialysis (HD) patients is controversial. In this study, we evaluated the impact of DCa concentration on mortality in incident HD patient. Incident HD patients were selected from the Clinical Research Center registry-a prospective cohort study on dialysis patients in Korea. Patients were categorized into 3 groups according to the prescribed DCa concentration at the time of enrollment. High DCa was defined as a concentration of 3.5 mEq/L, mid-DCa as 3.0 mEq/L, and low DCa as 2.5 to 2.6 mEq/L. The primary outcome was all-cause mortality and secondary outcomes were cardiovascular or infection-related hospitalization. A total of 1182 patients with incident HD were included. The number of patients in each group was 182 (15.4%) in high DCa group, 701 (59.3%) in the mid-DCa group, and 299 (25.3%) in the low DCa group. The median follow-up period was 16 months. The high DCa group had a significantly higher risk of all-cause mortality compared with the mid-DCa group (hazard ratio [HR] 2.23, 95% confidence interval [CI] 1.28-3.90, P = 0.005) and the low DCa group (HR 3.67, 95% CI 1.78-7.55, P < 0.001) after adjustment for clinical variables. The high DCa group was associated with higher risk of cardiovascular and infection-related hospitalization compared with the low DCa group (HR 3.25, 95% CI 1.53-6.89, P = 0.002; and HR 2.77, 95% CI 1.29-5.94, P =  .009, respectively). Of these 1182 patients, 163 patients from each group were matched by propensity scores. In the propensity score matched analysis, the high DCa group had a significantly higher risk of all-cause mortality compared with the mid-DCa group (HR 2.52, 95% CI 1.04-6.07, P = 0.04) and the low DCa group (HR 4.25, 95% CI 1.64-11.03, P = 0.003) after adjustment for clinical variables. Our data showed that HD using a high DCa was a significant risk factor for all-cause mortality and cardiovascular or infection-related hospitalization in incident HD patients.

Arteriosclerosis and vascular calcification: causes, clinical assessment and therapy

BACKGROUND

Arteriosclerosis is a pathological, structural (media vascular calcification) and physiological (modified vascular smooth vessel cells; increased arterial stiffness) alteration of the vessel wall. Through improved assessment methods (functional and imaging), it has become a well-known phenomenon in recent decades. However, its clinical importance was underestimated until recently.

MATERIALS AND METHODS

Currently available English-speaking data about conditions/diseases associated with arteriosclerosis, its clinical sequels, available diagnostic procedures and therapeutic modalities were reviewed and summarized.

RESULTS

In recent decades, emerging data have brought about a better understanding of causes and consequences of arteriosclerosis and highlight its growing clinical impact.

CONCLUSION

Although arteriosclerosis showed an independent clinical impact on cardiovascular morbidity and mortality, especially in patients with chronic kidney disease/end-stage renal disease (CKD/ESRD) and diabetes mellitus, convincing clinical therapy concepts are not available until now. The establishment of novel therapeutic strategies derived from basic research is strongly needed.

Arterial Stiffness and Renal Replacement Therapy: A Controversial Topic

The increase of arterial stiffness has been to have a significant impact on predicting mortality in end-stage renal disease patients. Pulse wave velocity (PWV) is a noninvasive, reliable parameter of regional arterial stiffness that integrates the vascular geometry and arterial wall intrinsic elasticity and is capable of predicting cardiovascular mortality in this patient population. Nevertheless, reports on PWV in dialyzed patients are contradictory and sometimes inconsistent: some reports claim the arterial wall stiffness increases (i.e., PWV increase), others claim that it is reduced, and some even state that it augments in the aorta while it simultaneously decreases in the brachial artery pathway. The purpose of this study was to analyze the literature in which longitudinal or transversal studies were performed in hemodialysis and/or peritoneal dialysis patients, in order to characterize arterial stiffness and the responsiveness to renal replacement therapy.

Dialysate Calcium Concentration, Mineral Metabolism Disorders, and Cardiovascular Disease: Deciding the Hemodialysis Bath

Patients with end-stage kidney disease treated with dialysis are at increased risk to experience fractures and cardiovascular events than similar-aged people from the general population. The enhanced risk for these outcomes in dialysis patients is not completely explained by traditional risk factors for osteoporosis and cardiovascular disease. Mineral metabolism abnormalities are almost universal by the time patients require dialysis therapy, with most patients having some type of renal osteodystrophy and vascular calcification. These abnormalities have been linked to adverse skeletal and cardiovascular events. However, it has become clear that the treatment regimens used to modify the serum calcium, phosphate, and parathyroid hormone levels almost certainly contribute to the poor outcomes for dialysis patients. In this article, we focus on one aspect of mineral metabolism management; dialysate calcium concentration and the relationships among dialysate calcium concentrations, mineral and bone disorder, and cardiovascular disease in hemodialysis patients.

Individualization of dialysate calcium concentration according to baseline pre-dialysis serum calcium

BACKGROUND

A positive calcium balance may contribute to vascular calcification, while a negative balance increases iPTH. We explored the impact of different dialysate calcium concentrations on bone and mineral metabolism parameters according to pre-dialysis serum calcium levels.

RESULTS

Fifty-six hemodialysis patients were dialyzed with 3.0 or 2.5 mEq/l dialysate [calcium] in a crossover study of two weeks. Bone mineral metabolites were measured prior to and following the hemodialysis session. A 3.0 mEq/l dialysate [calcium] increased more post-dialysis total calcium and ionized calcium than 2.5 mEq/l dialysate [calcium]. The mildest dialysis-induced changes in calcium and PTH were observed in patients with pre-dialysis serum calcium <8.75 mg/dl dialyzed with 2.5 mEq/l dialysate [calcium] and in patients with pre-dialysis serum calcium >9.15 mg/dl dialyzed with 3.0 mEq/l calcium dialysate.

CONCLUSION

In conclusion, the individualization of dialysate calcium concentration according to baseline pre-dialysis serum calcium may prevent major excursions in post-dialysis serum calcium and iPTH levels.

SHORT SUMMARY

High calcium dialysate may increase serum calcium in hemodialysis patients, while low dialysate calcium may increase PTH. Individualization of dialysate calcium according to predialysis serum calcium levels may prevent or decrease unwanted excursions of both serum calcium and PTH.

Calcium profiling in hemodiafiltration: a new way to reduce the calcium overload risk without compromising cardiovascular stability

BACKGROUND

Low and high dialysate calcium (Ca²⁺) content may have positive and harmful effects depending on the considered pathological aspect: hemodynamic instability, cardiac arrhythmias, parathormone release, adynamic bone disease, cardio-vascular calcifications. We hypothesized that a time-profiled Ca²⁺ concentration would keep the cardiovascular advantages of high Ca²⁺ but would reduce the risk of calcium overload.

METHODS

A prospective, multicenter study using a particular hemodiafiltration technique that allows the profiling of electrolytes was designed. Patients (n = 22) underwent randomly a 3-week dialysis session with low and high constant dialysate Ca²⁺ (Ld(Ca,), 1.25 mM and Hd(Ca,), 2 mM) and profiled Ca²⁺ (Pd(Ca)), respectively. Plasma and spent dialysate Ca²⁺, systolic and diastolic arterial pressure (SAP, DAP) and QT interval corrected for heart rate (QTc) were analyzed.

RESULTS

Plasma Ca²⁺ concentration decreased in Ld(Ca), whereas it increased in Hd(Ca) and to a lesser extent, in Pd(Ca). Total amount of Ca²⁺ given to the patient in Pd(Ca) (15.5 ± 1.0 mmol) was higher than in Ld(Ca) (4.3 ± 1.6 mmol) but lower than in Hd(Ca) (21.9 ± 3.3 mmol). SAP and DAP decreased in Ld(Ca), whereas it was almost constant in both Hd(Ca) and Pd(Ca·). QTc significantly increased, up to critical values (>460 msec), only during Ld(Ca·).

CONCLUSIONS

Pd(Ca) seems to retain the advantages of high Ca²⁺ in terms of hemodynamic stability and modification of QTc while reducing the excessive positive calcium balance typical of dialysis with high Ca²⁺ content.

Calcium balance and negative impact of calcium load in peritoneal dialysis patients

Like hemodialysis patients, peritoneal dialysis (PD) patients are facing an excessively increased burden of vascular and valvular calcification. According to some surveys, more than 80% of prevalent PD patients are complicated with vascular calcification, and more than one third have heart valve calcification. Dysregulated phosphate metabolism is well recognized to play an important role in inducing vascular calcification, but increasing evidence is suggesting that dysregulated calcium metabolism also promotes vascular calcification and might in fact be more potent than phosphate in inducing that calcification. Growing evidence from randomized controlled trials shows more progression of vascular calcification and higher mortality among chronic kidney disease (CKD) patients receiving calcium-based phosphate binders than among those receiving non-calcium-containing phosphate binders. Those results raise important safety concern about the use of high-dose calcium-based phosphate binders in the CKD population, including both non-dialysis and dialysis patients (especially anuric dialysis patients), who have markedly reduced urinary calcium excretion. To prevent calcium overload, this review recommends restricting the dose of calcium-based phosphate binders in CKD patients, especially those who are elderly, who have increased cardiovascular risk, who already have baseline vascular or valvular calcification, or who have low intact parathyroid hormone and adynamic bone disease.

Do higher dialysate calcium concentrations increase vascular stiffness in haemodialysis patients as measured by aortic pulse wave velocity?

Background

Haemodialysis patients have an increased prevalence of hypertension and risk of cardiovascular mortality and stroke. Higher dialysate calcium concentrations have been reported to cause both an acute and chronic increase in arterial stiffness. We therefore looked at changes in arterial stiffness in established haemodialysis patients to determine whether there was a threshold effect of dialysate calcium concentration linked to change in arterial stiffness.

Methods

We performed pulse wave velocity measurements six months apart in patients dialysing with calcium concentrations of 1.0, 1.25, 1.35 and ≥1.5 mmol/l.

Results

289 patients, 62.2% male, mean age 65.5 ± 15.7 years, weight body mass index 25.8 ± 5.4 kg/m² ,47.9% diabetic were studied. Systolic blood pressure (SBP) was 148.4 ± 28.6 mmHg and diastolic blood pressure (DBP) 80.2 ± 15.5 mmHg. Mean pulse wave velocity increased over time (9.66 ± 2.0 vs 10.13 ± 2.16 m/s; p < 0.001), but there was no change in aortic augmentation index (38.7 ± 16.3 vs 39.8 ± 15.6%) or central aortic pressure (149.6 ± 33.3 vs 150.4 ± 31.9 mmHg).

Pulse wave velocity did not differ between the four groups either at start or end of the study, but increased both in the groups dialysing with a calcium concentration of 1.0 mmol/l (9.64 ± 1.94 vs 10.45 ± 1.98 m/s, p = 0.0028) and also with 1.35 mmol/l (9.75 ± 1.96 vs 10.21 ± 2.18 m/s, p = 0.02).

Conclusions

Pulse wave velocity increased over the six months study. As pulse wave velocity increased in the group dialysing using the lowest dialysate calcium, it is likely that factors, other than simple net calcium influx and efflux during dialysis according to dialysate calcium concentration are involved with vascular stiffening.

Association of parathyroid hormone and 25-OH-vitamin D levels with arterial stiffness in postmenopausal women with vitamin D insufficiency

AIM

Vitamin D insufficiency and increased parathyroid hormone (PTH) levels have been suggested as prognostic indices for cardiovascular disease. Arterial stiffness, a surrogate marker for cardiovascular disease, is often increased in patients with primary hyperparathyroidism. PTH levels increase in patients with low 25-OH-vitamin D levels, but the influence of such an increase on arterial stiffness has not been investigated in postmenopausal women with reduced 25-OH-vitamin D levels. We therefore investigated the association between PTH and aortic stiffness in postmenopausal women with reduced 25-OH-vitamin D levels.

METHODS

One hundred fifty postmenopausal women with 25-OH-vitamin D insufficiency (<30 ng/mL) were recruited. Aortic pulse wave velocity (aPWV), a measure of arterial stiffness, PTH and 25-OH-vitamin D levels were measured. Cardiovascular risk factors and markers of bone formation were evaluated.

RESULTS

The 25-OH-vitamin D levels were associated with aPWV (rho=-0.23, p=0.006), but the association was not significant when controlling for PTH. Significant correlates of aPWV included age, body mass index, mean arterial pressure and PTH (rho=0.39, p<0.001). Arterial stiffness was predicted by logarithmically transformed PTH levels (β=0.23, p=0.007), independent of traditional cardiovascular risk factors and factors involved in bone formation. Increased PTH levels (>62 pg/mL) were associated with a 3.0-5.4-fold increased probability of having a mild-severe increase in aortic stiffness, irrespective of confounders.

CONCLUSION

Among postmenopausal women with reduced 25-OH-vitamin D levels, elevated PTH levels were a significant predictor of aortic stiffness, irrespective of cardiovascular risk factors and of factors involved in bone formation. PTH accounted for the association between 25-OH-vitamin D levels and aortic stiffness.