The KDIGO guideline for dialysate calcium will result in an increased incidence of calcium accumulation in hemodialysis patients

Same therapy, same calcium mobilization? Exploring calcium exchange across body compartments using a patient-specific predictive model

BACKGROUND

Comprehensive, patient-specific models are essential to study calcium deposition and mobilization during dialysis. We aim to develop tools to support clinical prescriptions with a more accurate approach for the prediction of calcium mobilization while also considering major electrolytes and catabolites.

METHODS

We modified a multi-solute model predicting patient-specific dialysis response by incorporating a calcium buffer to represent bone exchanges. Data from four centers, involving 127 patients with six sessions each, were utilized. For each patient, three sessions were allocated for model training (ID123), while the remaining sessions were for validation (PRED456). The normalized root mean square error (nRMSE%) was used to evaluate both descriptive and predictive accuracy. Correlations between initial data and calcium exchanges were also assessed.

RESULTS

The overall nRMSE% for ID123 was 3.92%. For PRED456, it was 3.46% (ranging from a minimum of 1.17% for [Na+] to a maximum of 6.62% for [urea]). The median nRMSE% for plasma calcium varied between 1.13 and 8.32 for SHD sessions, depending on whether Ca_dialysis fluid (Cad) was ≥ or <1.50 mmol/L, respectively. For HDF sessions, the range was between 2.90 and 5.89. A significant and moderate correlation was found between overall calcium removal and the buffer balance. The most robust correlation observed was between the amount of calcium administered via post-dilution fluid and the overall calcium removal in the dialysis filter.

CONCLUSIONS

Identical therapy settings do not uniformly affect calcium mobilization, and our approach offers insight into calcium distribution across body compartments. This understanding will enhance clinical prescription practices.

Calcium mass balance in adults during single hemodialysis and hemodiafiltration treatments using lower calcium dialysate concentrations

BACKGROUND

Debate continues as to the optimum hemodialysis (HD) dialysate calcium concentration. Although current guidelines advocate 1.25-1.5 mmol/L, some investigators have suggested these may cause calcium gains. As such we investigated whether using dialysate calcium of 1.25 mmol/L risked calcium gains, and whether there were differences between hemodiafiltration and high flux HD.

METHODS

We continuously collect an aliquot of effluent dialysate during dialysis sessions, and calculated dialysis calcium mass balance by the difference between the amount of calcium delivered as fresh dialysate and that lost in effluent dialysate.

RESULTS

We studied 106 stable outpatients, 64% male, mean age 64.4 ± 16.2 years, median dialysis vintage 32 (22-60) months. Most sessions (69%) used a 1.0 mmol/L calcium dialysate, with a median sessional loss of 13.7 (11.5-17.1) mmol, whereas using 1.25 mmol/L the median loss was 7.4 (4.9-10.1) mmol, but with 6.9% had a positive balance (p = 0.031 vs dialysate calcium 1.0 mmol/L). Most patients (85.8%) were treated by hemodiafiltration, but there was no difference in sessional losses (11.7 (8.4-15.8) vs 13.5 (8.1-16.8)) with high flux HD. Dialysis sessional calcium balance was associated with the use of lower dialysate calcium concentration (β -19.5, 95% confidence limits (95%CL) -27.7 to -11.3, p < 0.001), and sessional duration (β 0.07 (95% CL) 0.03-012, p = 0.002).

CONCLUSION

Ideally, the choice of dialysate calcium should be individualized, but clinicians should be aware, that even when using a dialysate calcium of 1.25 mmol/L, some patients are at risk of a calcium gain during hemodiafiltration and high-flux hemodialysis.

The mechanisms underlying acute myocardial infarction in chronic kidney disease patients undergoing hemodialysis

Cardiovascular disease (CVD) is a leading cause of death in chronic kidney disease (CKD). Hemodialysis is one of the main treatments for patients with end-stage kidney disease. Epidemiological data has shown that acute myocardial infarction (AMI) accounts for the main reason for death in patients with CKD under hemodialysis therapy. Immune dysfunction and changes in metabolism (including a high level of inflammatory cytokines, a disorder of lipid and mineral ion homeostasis, accumulation of uremic toxins et al.) during CKD can deteriorate stability of atherosclerotic plaque and promote vascular calcification, which are exactly the pathophysiological mechanisms underlying the occurrence of AMI. Meanwhile, the hemodialysis itself also has adverse effects on lipoprotein, the immune system and hemodynamics, which contribute to the high incidence of AMI in these patients. This review aims to summarize the mechanisms and further promising methods of prevention and treatment of AMI in CKD patients undergoing hemodialysis, which can provide an excellent paradigm for exploring the crosstalk between the kidney and cardiovascular system.

Safety and Efficacy of Cinacalcet in Children Aged Under 3 Years on Maintenance Dialysis

Introduction

Secondary hyperparathyroidism (sHPT) is particularly severe in rapidly growing infants in dialysis. Although cinacalcet is effective and licensed in dialysis in children aged >3 years, its efficacy and safety for children aged <3 years is unknown.

Methods

We identified 26 children aged <3 years who were on dialysis and treated with cinacalcet between 2009 and 2021 in 8 European pediatric centers.

Results

Median (interquartile range) age at the start of cinacalcet was 18 (interquartile range: 11-27) months, serum parathyroid hormone (PTH) was 792 (411-1397) pg/ml, corresponding to 11.6 (5.9-19.8) times the upper limit of normal (ULN). Serum calcium was 2.56 (2.43-2.75) mmol/l, and serum phosphate 1.47 (1.16-1.71) mmol/l. Serum 25-OH vitamin D (25-OHD) was 70 (60-89) nmol/l, 3 children were vitamin D deficient (<50 nmol/l). The initial cinacalcet dose was 0.4 (0.2-0.8) mg/kg/d and the maximum dose was 1.1 (0.6-1.2) mg/kg/d. The median follow-up under cinacalcet was 1.2 (0.7-2.0) years. PTH decreased to 4.3 (2.2-7.8) times the ULN after 6 months, to 2.0 (1.0-5.3) times ULN after 12 months, and to 1.6 (0.5-3.4) times thereafter (P = 0.017/0.003/<0.0001, log-transformed PTH). Seven of the 26 infants developed 10 hypocalcemic episodes <2.10 mmol/l. Oral calcium intake was 84% (66%-117%) of recommended nutrient intake at start, 100% (64%-142%) at 3 months and declined to 78% (65%-102%) at 12 months of therapy. Three children developed clinical signs of precocious puberty.

Conclusion

Cinacalcet efficiently controlled severe sHPT in children aged <3 years and was associated with hypocalcemic episodes (similar to what is observed in older children) and precious puberty, thereby mandating meticulous control of calcium (considering nutrition, supplementation, and dialysate) and endocrine changes.

Role of Chronic Kidney Disease (CKD)-Mineral and Bone Disorder (MBD) in the Pathogenesis of Cardiovascular Disease in CKD

Cardiovascular disease (CVD) is the leading cause of death in patients with chronic kidney disease (CKD). Multiple factors account for the increased incidence of cardiovascular morbidity and mortality in patients with CKD. Traditional risk factors for atherosclerosis and arteriosclerosis, including age, hypertension, dyslipidemia, diabetes mellitus, and smoking, are also risk factors for CKD. Non-traditional risk factors specific for CKD are also involved in CVD pathogenesis in patients with CKD. Recently, CKD-mineral and bone disorder (CKD-MBD) has emerged as a key player in CVD pathogenesis in the context of CKD. CKD-MBD manifests as hypocalcemia and hyperphosphatemia in the later stages of CKD; however, it initially develops much earlier in disease course. The initial step in CKD-MBD involves decreased phosphate excretion in the urine, followed by increased circulating concentrations of fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH), which increase urinary phosphate excretion. Simultaneously, the serum calcitriol concentration decreases as a result of FGF23 elevation. Importantly, FGF23 and PTH cause left ventricular hypertrophy, arrhythmia, and cardiovascular calcification. More recently, calciprotein particles, which are nanoparticles composed of calcium, phosphate, and fetuin-A, among other components, have been reported to cause inflammation, cardiovascular calcification, and other clinically relevant outcomes. CKD-MBD has become one of the critical therapeutic targets for the prevention of cardiovascular events and is another link between cardiology and nephrology. In this review, we describe the role of CKD-MBD in the pathogenesis of cardiovascular disorders and present the current treatment strategies for CKD-MBD.

Mathematical Models of Parathyroid Gland Biology: Complexity and Clinical Use

Altered parathyroid gland biology is a major driver of chronic kidney disease-mineral bone disorder (CKD-MBD) in patients with chronic kidney disease. CKD-MBD is associated with a high risk of vascular calcification and cardiovascular events. A hallmark of CKD-MBD is secondary hyperparathyroidism with increased parathyroid hormone (PTH) synthesis and release and reduced expression of calcium-sensing receptors on the surface of parathyroid cells and eventually hyperplasia of parathyroid gland cells. The KDIGO guidelines strongly recommend the control of PTH in hemodialysis patients. Due to the complexity of parathyroid gland biology, mathematical models have been employed to study the interaction of PTH regulators and PTH plasma concentrations. Here, we present an overview of various model approaches and discuss the impact of different model structures and complexities on the clinical use of these models.

Early morning hemodynamic changes and left ventricular hypertrophy and mortality in hemodialysis patients

INTRODUCTION

An exaggeration of the early morning increase in BP, a phenomenon accompanied by a parallel rise in heart rate (HR), is a marker of high cardiovascular risk. The early morning changes in these parameters have not been investigated in the hemodialysis population.

METHODS

In a pilot, single center study including a series of 58 patients we measured the pre-awakening BP and HR surges and the nocturnal dipping of the same parameters as well as other established indicators of autonomic function (weighted 24 h systolic BP and HR variability) and tested their relationship with the left ventricular mass index (LVMI) and with the risk of death over a median follow up of 40 months.

RESULTS

The pre-awakening HR surge (r = - 0.46, P = 0.001) but not the corresponding BP surge (r = - 0.1, P = 0.98) was associated with LVMI and the risk of death [HR (1 unit): 0.89, 95% CI 0.83-0.96, P = 0.001]. The link between the pre-awakening HR surge with these outcome measures was robust and largely independent of established risk factors in the hemodialysis population, including the nocturnal dipping of BP. Weighted 24 h systolic BP and HR variability did not correlate with LVMI (all P > 0.11) nor with the risk of death (P > 0.11) and were also independent of the nocturnal dipping of systolic BP and HR.

CONCLUSION

This pilot study suggests that the low early morning changes in HR, likely reflecting enhanced sympathetic activity, entail a high risk for left ventricular hypertrophy (LVH) and mortality in the hemodialysis population.

Skeletal and cardiovascular consequences of a positive calcium balance during hemodialysis

Patients on hemodialysis are exposed to calcium via the dialysate at least three times a week. Changes in serum calcium vary according to calcium mass transfer during dialysis, which is dependent on the gradient between serum and dialysate calcium concentration (d[Ca]) and the skeleton turnover status that alters the ability of bone to incorporate calcium. Although underappreciated, the d[Ca] can potentially cause positive calcium balance that leads to systemic organ damage, including associations with mortality, myocardial dysfunction, hemodynamic tolerability, vascular calcification, and arrhythmias. The pathophysiology of these adverse effects includes serum calcium changes, parathyroid hormone suppression, and vascular calcification through indirect and direct effects. Some organs are more susceptible to alterations in calcium homeostasis. In this review, we discuss the existing data and potential mechanisms linking the d[Ca] to calcium balance with consequent dysfunction of the skeleton, myocardium, and arteries.

Intradialytic Calcium Kinetics and Cardiovascular Disease in Chronic Hemodialysis Patients

BACKGROUND/OBJECTIVE

Calcium loading has been associated with cardiovascular risk in hemodialysis (HD) patients. However, it remains to be elucidated whether alterations of intradialytic calcium buffering add to the increased cardiovascular disease burden in this high-risk population.

METHODS

Intradialytic calcium kinetics was evaluated in a cross-sectional observational study by measuring dialysate-sided ionized calcium mass balance (iCaMB), calcium buffer capacity, and change in serum calcium levels in 40 chronic HD patients during a routine HD session. A dialysate calcium of 3.5 mEq/L was used to adequately challenge calcium buffer mechanisms. Aortic pulse wave velocity and serum osteocalcin levels were measured prior to the HD session. Presence of cardiovascular disease and diabetes was assessed.

RESULTS

The mean dialysate-sided iCaMB, extracellular fluid ionized calcium mass gain, and buffered ionized calcium mass were 469 (±154), 111 (±49), and 358 (±145) mg/HD, respectively. The mean ionized serum calcium increase (∆iCa) was 0.42 (±0.14) mEq/L per HD. The mean intradialytic calcium buffer capacity was 73 (±18)%. Multivariate regression analysis revealed significant independent association of (1) iCaMB with the dialysate-to-blood calcium gradient at HD start and (2) intradialytic calcium buffer capacity with undercarboxylated osteocalcin. The presence of coronary heart disease was associated with higher ∆iCa but not iCaMB in the multivariate model.

CONCLUSIONS

In line with our proof-of-concept study, we provide clinical evidence for a rapidly accessible and exchangeable calcium pool involved in intradialytic calcium regulation and for the role of osteocalcin as a potential biomarker. Our findings argue for evaluating the prognostic potential of intradialytic calcium kinetics in prospective clinical trials.

Calcium balance in hemodialysis: More uncertainty than certainty

There is controversy about the choice of dialysate calcium concentration (DCa), with strong arguments both in favor of and against the use of a low or high DCa, as they can both be potentially harmful. Evidence suggests that calcium mass balance is positive with a DCa 3.5 mEq/L, negative or neutral with the use of DCa 2.5 mEq/L, whereas both positive and negative balances have been observed with the use of DCa 3.0 mEq/L. Overall, the use of DCa >2.5 mEq/L is usually associated with an increase in serum calcium level and a decrease in serum PTH level and use of lower vitamin D analogue dose, with the opposite effects usually observed with the use of lower DCa. Most of the available evidence is from small-sized and crossover studies; hence, evidence should be regarded with caution and applied in a patient-specific manner. As there are a lot of significant unanswered questions regarding calcium balance and the optimal DCa in hemodialysis patients, further high-quality research is needed to clarify many still unclear aspects of calcium homeostasis and balance in these patients. In conclusion, with the existing evidence the choice of DCa needs to be individualized and contextualized in the setting of each patient's calcium balance needs and homeostatic response, taking also into account oral calcium intake (dietary and medicinal), any other relevant therapy administered, such as vitamin D analogues, the type of renal mineral bone disorder, and associated cardiovascular comorbidity.

Citric-acid dialysate improves the calcification propensity of hemodialysis patients: A multicenter prospective randomized cross-over trial

INTRODUCTION

The concentration of dialysate calcium (dCa) has been suggested to affect vascular calcification, but evidence is scarce. Calcification propensity reflects the intrinsic capacity of serum to prevent calcium and phosphate to precipitate. The use of citric-acid dialysate may have a beneficial effect on the calcification propensity due to the chelating effect on calcium and magnesium. The aim of this study was to compare the intradialytic and short-term effects of haemodialysis with either standard acetic-acid dialysate with dCa1.50 (A1.5) or dCa1.25 (A1.25), as well as citric-acid dialysate with dCa1.50 (C1.5) in bicarbonate dialysis on the calcification propensity of serum.

METHODS

Chronic stable hemodialysis patients were included. This multicenter randomized cross-over study consisted out of a baseline week (A1.5), followed by the randomized sequence of A1.25 or C1.5 for one week after which the alternate treatment was provided after a washout week with A1.5. Calcification propensity of serum was assessed by time-resolved nephelometry where the T50 reflects the transition time between formation of primary and secondary calciprotein particles.

RESULTS

Eighteen patients (median age 70 years) completed the study. Intradialytic change in T50 was increased with C1.5 (121 [90-152]min) compared to A1.25 (83 [43-108]min, p<0.001) and A1.5 (66 [18-102]min, p<0.001). During the treatment week, predialysis T50 increased significantly from the first to the third session with C1.5 (271 [234-291] to 280 [262-339]min, p = 0.002) and with A1.25 (274 [213-308] to 307 [256-337]min, p<0.001), but not with A1.5 (284 [235-346] to 300 [247-335]min, p = 0.33).

CONCLUSION

Calcification propensity, as measured by the change in T50, improved significantly during treatment in C1.5 compared to A1.25 and A1.5. Long-term studies are needed to investigate the effects of different dialysate compositions concentrations on vascular calcification and bone mineral disorders.

Coronary Artery Calcification in Hemodialysis and Peritoneal Dialysis

BACKGROUND

Vascular calcification is seen in most patients on dialysis and is strongly associated with cardiovascular mortality. Vascular calcification is promoted by phosphate, which generally reaches higher levels in hemodialysis than in peritoneal dialysis. However, whether vascular calcification develops less in peritoneal dialysis than in hemodialysis is currently unknown. Therefore, we compared coronary artery calcification (CAC), its progression, and calcification biomarkers between patients on hemodialysis and peritoneal dialysis.

METHODS

We measured CAC in 134 patients who had been treated exclusively with hemodialysis (n = 94) or peritoneal dialysis (n = 40) and were transplantation candidates. In 57 of them (34 on hemodialysis and 23 on peritoneal dialysis), we also measured CAC progression annually up to 3 years and the inactive species of desphospho-uncarboxylated matrix Gla protein (dp-ucMGP), fetuin-A, osteoprotegerin. We compared CAC cross-sectionally with Tobit regression. CAC progression was compared in 2 ways: with linear mixed models as the difference in square root transformed volume score per year (ΔCAC SQRV) and with Tobit mixed models. We adjusted for potential confounders.

RESULTS

In the cross-sectional cohort, CAC volume scores were 92 mm3 in hemodialysis and 492 mm3 in peritoneal dialysis (adjusted difference 436 mm3; 95% CI -47 to 919; p = 0.08). In the longitudinal cohort, peritoneal dialysis was associated with significantly more CAC progression defined as ΔCAC SQRV (adjusted difference 1.20; 95% CI 0.09 to 2.31; p = 0.03), but not with Tobit mixed models (adjusted difference in CAC score increase per year 106 mm3; 95% CI -140 to 352; p = 0.40). Peritoneal dialysis was associated with higher osteoprotegerin (adjusted p = 0.02) but not with dp-ucMGP or fetuin-A.

CONCLUSIONS

Peritoneal dialysis is not associated with less CAC or CAC progression than hemodialysis, and perhaps with even more progression. This indicates that vascular calcification does not develop less in peritoneal dialysis than in hemodialysis.

Overview of the 2017 KDIGO CKD-MBD Update: Practice Implications for Adult Hemodialysis Patients

Renal dietitians play a pivotal role in the ongoing management of chronic kidney disease in patients on hemodialysis. Awareness of changes to clinical practice guidelines that may impact laboratory parameters associated with chronic kidney disease-mineral and bone disorder is important for optimal patient care. In this article, the Kidney Disease: Improving Global Outcomes 2017 Clinical Practice Guideline Update recommendations related to the treatment of secondary hyperparathyroidism in adults on hemodialysis are reviewed and treatment implications for renal dietitians discussed. Specific attention is given to the integration of updated recommendations such as the use of calcimimetics as part of a combination approach to the existing treatment paradigm. Renal dietitians can directly apply the updated clinical recommendations in the evaluation of diet composition; food additives; medication adherence challenges with phosphate binder type and use and serial monitoring of phosphorus, calcium, and parathyroid hormone levels to inform clinical decisions on treatment options for patients.

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.

Impact of post-dialysis calcium level on ex vivo rat aortic wall calcification

OBJECTIVES

Vascular calcification is a frequent complication in chronic haemodialysis patients and is associated with adverse outcomes. Serum calcium and phosphate levels and imbalances in calcification regulators are thought to contribute to the process. In this regard, the dialysate calcium concentration is a modifiable tool for modulating the risk of vascular calcification. We explored pre- and post-dialysis phosphate and calcium concentrations in stable chronic haemodialysis patients treated by dialysis with the KDIGO-suggested 1.5 mmol/L calcium dialysate to investigate the effects on ex vivo calcification of rat aortic rings.

APPROACH AND RESULTS

At the end of haemodialysis, mean serum calcium levels were increased in 88% of paired pre-/post-dialysis samples, while mean serum phosphate and parathyroid hormone levels were decreased. Rat aortic ring cultures grown at the same calcium and phosphate concentrations revealed that pre- and post-dialysis resulted in a similar degree of calcification. By contrast, haemodialysis with unchanged serum calcium resulted in a 5-fold reduction in calcium deposition.

CONCLUSION

Dialysis with the widely prescribed 1.5 mmol/L calcium dose results in persistent high serum calcification potential in a sizable proportion of patients, driven by increased post-dialysis calcium concentration. This could potentially be mitigated by individualising dialysate calcium dosage based on pre-dialysis serum calcium levels.

Effects of low calcium dialysate on the progression of coronary artery calcification in hemodialysis patients: An open-label 12-month randomized clinical trial

BACKGROUND

The association between the dialysate calcium level and coronary artery calcification (CAC) has not yet been evaluated in hemodialysis patients. The objective of this study was to determine whether lowering the dialysate calcium levels would decrease the progression of coronary artery calcification (CAC) compared to using standard calcium dialysate.

METHODS

We conducted an open-label randomized trial with parallel groups. The patients were randomly assigned to either 12-month treatment with low calcium dialysate (LCD; 1.25mmol/L, n=36) or standard calcium dialysate (SCD; 1.5mmol/L, n=40). The primary outcome was the change in the CAC scores assessed by 64-slice multidetector computed tomography after 12months.

RESULTS

During the treatment period, CAC scores increased in both groups, especially significant in LCD group (402.5±776.8, 580.5±1011.9, P=0.004). When we defined progressors as patients at second and third tertiles of CAC changes, progressor group had a higher proportion of LCD-treated patients than SCD-treated patients (P=0.0229). In multivariate analysis, LCD treatment is a significant risk factor for increase in CAC scores (odds ratio=5.720, 95% CI: 1.219-26.843, P=0.027).

CONCLUSIONS

Use of LCD may accelerate the progression of CAC in patients with chronic hemodialysis over a 12-month period.

TRIAL REGISTRATION

Clinical Research Information Service [Internet]; Osong (Chungcheongbuk-do): Korea Centers for Disease Control and Prevention, Ministry of Health and Welfare (Republic of Korea), 2010: KCT0000942. Available from: https://cris.nih.go.kr/cris/search/search_result_st01_kren.jsp?seq=3572&sLeft=2&type=my.

Assessment of intradialysis calcium mass balance by a single pool variable-volume calcium kinetic model

INTRODUCTION

A reliable method of intradialysis calcium mass balance quantification is far from been established. We herein investigated the use of a single-pool variable-volume Calcium kinetic model to assess calcium mass balance in chronic and stable dialysis patients.

METHODS

Thirty-four patients on thrice-weekly HD were studied during 240 dialysis sessions. All patients were dialyzed with a nominal total calcium concentration of 1.50 mmol/L. The main assumption of the model is that the calcium distribution volume is equal to the extracellular volume during dialysis. This hypothesis is assumed valid if measured and predicted end dialysis plasma water ionized calcium concentrations are equal. A difference between predicted and measured end-dialysis ionized plasma water calcium concentration is a deviation on our main hypothesis, meaning that a substantial amount of calcium is exchanged between the extracellular volume and a nonmodeled compartment.

FINDINGS

The difference between predicted and measured values was 0.02 mmol/L (range -0.08:0.16 mmol/L). With a mean ionized dialysate calcium concentration of 1.25 mmol/L, calcium mass balance was on average negative (mean ± SD -0.84 ± 1.33 mmol, range -5.42:2.75). Predialysis ionized plasma water concentration and total ultrafiltrate were the most important predictors of calcium mass balance. A significant mobilization of calcium from the extracellular pool to a nonmodeled pool was calculated in a group of patients.

DISCUSSION

The proposed single pool variable-volume Calcium kinetic model is adequate for prediction and quantification of intradialysis calcium mass balance, it can evaluate the eventual calcium transfer outside the extracellular pool in clinical practice.

Acute calcium kinetics in haemodialysis patients

INTRODUCTION

To avoid excessive calcium loading in haemodialysis (HD) patients, current guidelines suggest a dialysate calcium concentration (dCa) of 2·5 mEq/L based on relatively stable intradialytic serum calcium levels. However, the latter do not account for possible calcium storage in acutely accessible pools. A rapidly exchangeable calcium pool located at the bone level has been previously proposed to be involved in acute (minute-to-minute) extracellular calcium regulation.

DESIGN

To evaluate the contribution of this pool in the maintenance of serum calcium levels, acute calcium buffer capacity was assessed by measuring intradialytic dialysate-sided ionized calcium mass balance (iCa_MB ) and change in extracellular fluid calcium mass in chronic HD patients using a dCa of 3·5 (n = 28) and 2·5 (n = 10) mEq/L. Serum osteocalcin, the most abundant noncollagenous bone protein, was measured before the HD session.

RESULTS

iCa_MB was invariably positive for both 2·5 and 3·5 mEq/L dCa, with a mean of 434 (±125) and 725 (±162) mg/HD, respectively (P < 0·001). Buffered intradialytic calcium load was 410 (±116) and 565 (±130) mg/HD, and acute calcium buffer capacity was 95 (±8)% and 78 (±7)% (mean values at 2·5 and 3·5 mEq/L dCa, respectively) (P < 0·001). Using 3·5 mEq/L dCa, an independent association of acute calcium buffer capacity with undercarboxylated osteocalcin (β = 0·512, P = 0·002) was demonstrated.

CONCLUSIONS

Our data strongly suggest the existence of a rapidly exchangeable calcium pool that counteracts acute serum calcium deviations in HD patients. This study provides, for the first time, experimental evidence for the involvement of bone in acute extracellular calcium regulation in vivo.

Hemostasis biomarkers and risk of sepsis: the REGARDS cohort

Essentials Few studies have investigated the risk of sepsis by baseline hemostasis biomarkers measures. Baseline hemostasis biomarkers and risk of sepsis was examined using case-control study design. Increased fibrinogen, factor IX, and factor XI levels may be associated with risk of sepsis. Hemostasis biomarkers may provide a target for sepsis mitigation or prevention.

SUMMARY

Background Sepsis is a major public health concern, responsible for more than 750 000 hospitalizations and 200 000 annual deaths in the USA. Few studies have investigated the association between baseline measurements of hemostasis biomarkers and the future risk of sepsis. Objective To determine whether hemostasis biomarkers levels measured at baseline in a cohort of community-dwelling participants are associated with the risk of future sepsis events. Methods We performed a nested case-control study within the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort. We identified sepsis hospitalizations occurring over a 10-year period. There were 50 incident sepsis cases with baseline measurements of hemostasis (fibrinogen, factor VIII, FIX, FXI, protein C, and D-dimer). Using incidence density sampling, we matched the 50 sepsis cases with 200 controls by age, sex, and race. We used conditional logistic regression to evaluate the association between baseline hemostasis biomarkers and future sepsis events. Results Comparison of 50 sepsis cases with 200 non-sepsis controls showed that sepsis cases had lower education and income, were more likely to live in the stroke belt, had chronic lung disease, and had higher albumin level/creatinine level ratios (ACRs). Individuals with higher baseline fibrinogen levels (adjusted odds ratio [OR] per standard deviation: 1.40, 95% confidence interval [CI] 1.01-1.94), FIX levels ([OR] 1.46, 95% [CI] 1.03-2.07) and FXI levels ([OR]1.52, 95% [CI] 1.04-2.23) were more likely to experience a sepsis event. Conclusion Baseline fibrinogen, FIX and FXI levels are associated with future episodes of sepsis. Hemostasis biomarkers may provide targets for sepsis mitigation or prevention.

Quantification of Dialytic Removal and Extracellular Calcium Mass Balance during a Weekly Cycle of Hemodialysis

Objectives

The removal of calcium during hemodialysis with low calcium concentration in dialysis fluid is generally slow, and the net absorption of calcium from dialysis fluid is often reported. The details of the calcium transport process during dialysis and calcium mass balance in the extracellular fluid, however, have not been fully studied.

Methods

Weekly cycle of three dialysis sessions with interdialytic breaks of 2-2-3 days was monitored in 25 stable patients on maintenance hemodialysis with calcium concentration in dialysis fluid of 1.35 mmol/L. Total and ionic calcium were frequently measured in blood and dialysate. The volume of fluid compartments was measured by bioimpedance.

Results

Weekly dialytic removal of 12.79 ± 8.71 mmol calcium was found in 17 patients, whereas 9.48 ± 8.07 mmol calcium was absorbed per week from dialysis fluid in 8 patients. Ionic calcium was generally absorbed from dialysis fluid, whereas complexed calcium (the difference of total and ionic calcium in dialysis fluid) was removed from the body. The concentration of total calcium in plasma increased slightly during dialysis. The mass of total and ionic calcium in extracellular fluid decreased during dialysis in patients with the dialytic removal of calcium from the body and did not change in patients with the absorption of calcium from dialysis fluid.

Conclusions

We conclude that about one third of patients on dialysis with calcium 1.35 mmol/L in dialysis fluid may absorb calcium from dialysis fluid and therefore individual prescriptions of calcium concentration in dialysis fluid should be considered for such patients.

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.

Individualizing the dialysate calcium concentration

PURPOSE OF REVIEW

The optimal dialysate calcium concentration (DCC) in hemodialysis patients is still debated. Strategies have varied over time due to developments in the treatments available for mineral metabolism disorders and our increasing knowledge of bone and vascular diseases. International recommendations [Kidney Disease Outcomes Quality Initiative (KDIGO) and European Best Practice Guidelines] urge for DCC individualization in order to meet the patient's specific needs whenever possible. In this review, we aim to discuss the pros and cons of individualizing the DCC in hemodialysis patients.

RECENT FINDINGS

Different regions of the world have various strategies with respect to DCCs. Decreasing the DCC slightly reduces calcemia, but mainly stimulates parathyroid hormone secretion and bone turnover. Conversely, increasing the DCC increases calcemia slightly and reduces parathyroid hormone secretion and bone turnover markedly. Furthermore, higher DCCs favor hemodynamic stability and can prevent ventricular arrhythmias. The impact of DCC individualization on survival rate or cardiovascular calcification progression has not been evaluated.

SUMMARY

Individualizing DCC appears to be useful but requires time, a clear defined strategy, and close biological monitoring. Even though some studies have shown that using individualized DCCs of 1.25 or 1.75 mmol/l is not harmful, the real benefits of this strategy need to be assessed in a large, multicentric trial.

Prehospitalization Risk Factors for Acute Kidney Injury during Hospitalization for Serious Infections in the REGARDS Cohort

BACKGROUND/AIMS

Acute kidney injury (AKI) frequently occurs in hospitalized patients. In this study, we determined prehospitalization characteristics associated with AKI in community-dwelling adults hospitalized for a serious infection.

METHODS

We used prospective data from 30,239 participants of the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a national cohort of community-dwelling adults ≥45 years old. We identified serious infection hospitalizations between 2003 and 2012. Using the Kidney Disease Improving Global Outcomes (KDIGO) criteria, we defined AKI as an increase in serum creatinine (sCr) ≥0.3 mg/dl from the first inpatient sCr measurement during the first 7 hospitalization days. We excluded individuals with a history of renal transplant or preexisting end-stage renal disease as well as individuals with <2 sCr measurements. We identified baseline characteristics (sociodemographics, health behaviors, chronic medical conditions, biomarkers, and nonsteroidal anti-inflammatory, statin, or antihypertensive medication use) independently associated with AKI events using multivariable generalized estimating equations.

RESULTS

Over a median follow-up of 4.5 years (interquartile range 2.4-6.3), we included 2,074 serious infection hospitalizations among 1,543 individuals. AKI occurred in 296 of 2,074 hospitalizations (16.5%). On multivariable analysis, prehospitalization characteristics independently associated with AKI among individuals hospitalized for a serious infection included a history of diabetes [odds ratio (OR) 1.38; 95% CI 1.02-1.89], increased cystatin C (OR 1.73 per SD; 95% CI 1.20-2.50), and increased albumin-to-creatinine ratio (OR 1.19 per SD; 95% CI 1.007-1.40). Sex, race, hypertension, myocardial infarction, estimated glomerular filtration rate, high-sensitivity C-reactive protein, and the use of nonsteroidal anti-inflammatory, statin, or antihypertensive medications were not associated with AKI.

CONCLUSIONS

Community-dwelling adults with a history of diabetes or increased cystatin C or albumin-to-creatinine ratio are at increased risk for AKI after hospitalization for a serious infection. These findings may be used to identify individuals at high risk for AKI.

A neglected issue in dialysis practice: haemodialysate

The intended function of dialysate fluid is to correct the composition of uraemic blood to physiologic levels, both by reducing the concentration of uraemic toxins and correcting electrolyte and acid-base abnormalities. This is accomplished principally by formulating a dialysate whose constituent concentrations are set to approximate normal values in the body. Sodium balance is the cornerstone of intradialysis cardiovascular stability and good interdialytic blood pressure control; plasma potassium concentration and its intradialytic kinetics certainly play a role in the genesis of cardiac arrhythmias; calcium is related to haemodynamic stability, mineral bone disease and also cardiac arrhythmias; the role of magnesium is still controversial; lastly, acid buffering by means of base supplementation is one of the major roles of dialysis. In conclusion, learning about the art and the science of fashioning haemodialysates is one of the best ways to further the understanding of the pathophysiologic processes underlying myriad acid-base, fluid, electrolyte as well as blood pressure abnormalities of the uraemic patient on maintenance haemodialysis.

Black-white racial disparities in sepsis: a prospective analysis of the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort

INTRODUCTION

Sepsis is a major public health problem. Prior studies using hospital-based data describe higher rates of sepsis among black than whites participants. We sought to characterize racial differences in incident sepsis in a large cohort of adult community-dwelling adults.

METHODS

We analyzed data on 29,690 participants from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort. We determined the associations between race and first-infection and first-sepsis events, adjusted for participant sociodemographics, health behaviors, chronic medical conditions and biomarkers. We also determined the association between race and first-sepsis events limited to first-infection events. We contrasted participant characteristics and hospital course between black and white sepsis hospitalizations.

RESULTS

Among eligible REGARDS participants there were 12,216 (41.1%) black and 17,474 (58.9%) white participants. There were 2,600 first-infection events; the incidence of first-infection events was lower for black participants than for white participants (12.10 vs. 15.76 per 1,000 person-years; adjusted HR 0.65; 95% CI, 0.59-0.71). There were 1,526 first-sepsis events; the incidence of first-sepsis events was lower for black participants than for white participants (6.93 vs. 9.10 per 1,000 person-years, adjusted HR 0.64; 95% CI, 0.57-0.72). When limited to first-infection events, the odds of sepsis were similar between black and white participants (adjusted OR 1.01; 95% CI, 0.84-1.21). Among first-sepsis events, black participants were more likely to be diagnosed with severe sepsis (76.9% vs. 71.5%).

CONCLUSION

In the REGARDS cohort, black participants were less likely than white participants to experience infection and sepsis events. Further efforts should focus on elucidating the underlying reasons for these observations, which are in contrast to existing literature.

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.

Vascular calcification in chronic kidney disease: an update

Cardiovascular calcification is both a risk factor and contributor to morbidity and mortality. Patients with chronic kidney disease (and/or diabetes) exhibit accelerated calcification of the intima, media, heart valves and likely the myocardium as well as the rare condition of calcific uraemic arteriolopathy (calciphylaxis). Pathomechanistically, an imbalance of promoters (e.g. calcium and phosphate) and inhibitors (e.g. fetuin-A and matrix Gla protein) is central in the development of calcification. Next to biochemical and proteinacous alterations, cellular processes are also involved in the pathogenesis. Vascular smooth muscle cells undergo osteochondrogenesis, excrete vesicles and show signs of senescence. Therapeutically, measures to prevent the initiation of calcification by correcting the imbalance of promoters and inhibitors appear to be essential. In contrast to prevention, therapeutic regression of cardiovascular calcification in humans has been rarely reported. Measures to enhance secondary prevention in patients with established cardiovascular calcifications are currently being tested in clinical trials.

Calcium-phosphate and parathyroid intradialytic profiles: A potential aid for tailoring the dialysate calcium content of patients on different hemodialysis schedules

Severe hyperparathyroidism is a challenge on hemodialysis. The definition of dialysate calcium (Ca) is a pending issue with renewed importance in cases of individualized dialysis schedules and of portable home dialysis machines with low-flow dialysate. Direct measurement of calcium mass transfer is complex and is imprecisely reflected by differences in start-to-end of dialysis Ca levels. The study was performed in a dialysis unit dedicated to home hemodialysis and to critical patients with wide use of daily and tailored schedules. The Ca-phosphate (P)-parathyroid hormone (PTH) profile includes creatinine, urea, total and ionized Ca, albumin, sodium, potassium, P, PTH levels at start, mid, and end of dialysis. "Severe" secondary hyperparathyroidism was defined as PTH > 300 pg/mL for ≥3 months. Four schedules were tested: conventional dialysis (polysulfone dialyzer 1.8-2.1 m(2) ), with dialysate Ca 1.5 or 1.75 mmol/L, NxStage (Ca 1.5 mmol/L), and NxStage plus intradialytic Ca infusion. Dosages of vitamin D, calcium, phosphate binders, and Ca mimetic agents were adjusted monthly. Eighty Ca-P-PTH profiles were collected in 12 patients. Serum phosphate was efficiently reduced by all techniques. No differences in start-to-end PTH and Ca levels on dialysis were observed in patients with PTH levels < 300 pg/mL. Conversely, Ca levels in "severe" secondary hyperparathyroid patients significantly increased and PTH decreased during dialysis on all schedules except on Nxstage (P < 0.05). Our data support the need for tailored dialysate Ca content, even on "low-flow" daily home dialysis, in "severe" secondary hyperparathyroid patients in order to increase the therapeutic potentials of the new dialysis techniques.

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.

Should dialysate calcium be individualized?

The growing interest in a personalized choice of dialysate calcium concentration faces some important unsolved questions. First, the desired aims to be achieved should be clarified, as different d-Ca concentrations might differentially impact dialysis calcium balance and serum calcium concentration. A second point to be addressed is how to achieve the desired goals; the kinetics of calcium during dialysis treatment are complex. This is not an easy task and probably only an automatic device able to read serum calcium concentration in real-time and adjust d-Ca to it might supply an effective method for individualizing d-Ca. Finally, it is not even clear whether individualizing d-Ca is worth doing; cost-effectiveness studies might give some further insights into this intricate issue.

Correlations and time course of FGF23 and markers of bone metabolism in maintenance hemodialysis patients

OBJECTIVE

Parathyroid hormone (iPTH) and fibroblast growth factor 23 (FGF23) are elevated in secondary hyperparathyroidism. In hemodialysis, higher dialysate calcium (1.5 mmol/L) induces intradialytic suppression of iPTH, whereas its impact on FGF23 and markers of bone metabolism is unknown. We assessed the time course of FGF23 and markers of bone metabolism in relationship to dialysate calcium.

DESIGN AND METHODS

In this prospective cohort study of 19 patients on maintenance hemodialysis, we measured serum calcium (sCa), inorganic phosphate (iP), blood urea nitrogen (BUN), β2-microglobulin (ßMG), iPTH, FGF23, aminoterminal propeptide type 1 procollagen (P1NP), C-telopeptide of type I collagen for bone degradation (CTX-I), osteocalcin (OC), bone specific alkaline phosphatase (BALP), and tartrate-resistant acid phosphatase (TRAP5b) during a single hemodialysis session at baseline, 1, 2, and 3h of dialysis. The time course of measured parameters was compared according to groups of prescribed dialysate calcium of 1.25 mmol/L and 1.5 mmol/L.

RESULTS

iPTH declined in the 1.5 mmol/L dialysis group as serum calcium increased whereas it tended to increase in the 1.25 mmol/L group without significant changes in serum calcium. Patients on long-term dialysate calcium of 1.5 mmol/L had significantly lower CTX-I levels and tended to lower levels of iPTH, FGF23, OC, P1NP and TRAP5b at the start of dialysis compared to those on 1.25 mmol/L. CTX-I, FGF23 and OC but not BALP, P1NP and TRAP5b decreased during dialysis independent of dialysate calcium.

CONCLUSIONS

In spite of immediate effects on iPTH, dialysate calcium does not acutely affect other parameters of bone and mineral metabolism.

SHORT SUMMARY

Dialysate calcium concentration is known to have both immediate and longer-term impact on parathyroid hormone levels in hemodialysis patients. Little is known about the acute impact of dialysate calcium on bone metabolism. In this cross-sectional study of prevalent hemodialysis patients, we found no evidence of immediate short-term dialysate calcium-induced changes of fibroblast growth factor 23 or anabolic and catabolic markers of bone turnover during hemodialysis. However, differences in CTX-I and to a lesser extent other parameters between groups of higher and lower dialysate calcium suggest a longer-term effect that remains to be validated.

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.

Long-term mortality after community-acquired sepsis: a longitudinal population-based cohort study

OBJECTIVE

Prior studies have concentrated on the acute short-term outcomes of sepsis, with little focus on its long-term consequences. The objective of this study was to characterise long-term mortality following a sepsis event.

DESIGN

Population-based data from the 30 239 community-dwelling individuals in the REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort.

SETTING USA PARTICIPANTS

Community-dwelling adults ≥45 years of age. Sepsis was defined as hospitalisation or emergency department treatment for a serious infection with the presence of ≥2 systemic inflammatory response syndrome criteria.

OUTCOMES

6-year all-cause mortality. The analysis utilised a time-varying Cox model adjusted for participant's age, demographic factors, health behaviours and chronic medical conditions.

RESULTS

The participants were observed for a median of 6.1 years (IQR 4.5-7.1). During this period, 975 individuals experienced a sepsis event. Sepsis hospital mortality was 8.9%. One-year, 2-year and 5-year all-cause mortality among individuals with sepsis were 23%, 28.8% and 43.8%, respectively, compared with death rates of 1%, 2.6% and 8.3% among those who never developed sepsis. On multivariable analysis, the association of sepsis with increased all-cause mortality persisted for up to 5 years, after adjustment for confounders; year 0.00-1.00, adjusted HR (aHR) 13.07 (95% CI 10.63 to 16.06); year 1.01-2.00 aHR 2.64 (1.85 to 3.77); year 2.01-3.00 aHR 2.18 (1.43 to 3.33); year 3.01-4.00 aHR 1.97 (1.19 to 3.25); year 4.01-5.00 aHR 2.08 (1.14 to 3.79); year 5.01+ aHR 1.41 (0.67 to 2.98).

CONCLUSIONS

Individuals with sepsis exhibited increased rates of death for up to 5 years after the illness event, even after accounting for comorbidities. Sepsis is independently associated with increased risk of mortality well after hospital treatment.

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.

Clinical evaluation of a model for prediction of end-dialysis systemic ionized calcium concentration in citrate hemodialysis

BACKGROUND/AIM

Citrate anticoagulation in hemodialysis (HD) is increasingly drawing attention in the nephrology community. One of the major deterrents to a more widespread use are the monitoring requirements for fear of systemic calcium derangements. Means of accurately predicting systemic ionized calcium (iCa) may help to overcome this challenge. We have previously presented a mathematical model of regional citrate anticoagulation (RCA) to address this need. Here, we present a refined model and show results in an independent validation cohort of maintenance HD patients on Citrasate®, a calcium- and citrate-containing dialysate.

METHODS

A hybrid RCA model was developed, comprising the previously published 'native' RCA model and a statistical correction based on levels of alkaline phosphatase as a marker of bone turnover. The model was validated in 120 patients on Citrasate, a dialysate containing 0.8 mmol/l citrate and 1.125 mmol/l calcium. Systemic iCa was measured at the beginning and end of one HD treatment in each subject. Serum iCa predictions were compared between our previously published model and the new hybrid model.

RESULTS

On average, the hybrid model predicted end-HD systemic iCa with an error (predicted - measured) of 0.028 mmol/l, compared to -0.051 mmol/l with the previously published model. There were only 4 subjects out of the 120 analyzed in whom the prediction error was <-0.1 mmol/l, and only 6 in whom the error was >+0.1 mmol/l (max: +0.13 mmol/l).

CONCLUSION

This study demonstrates that the novel hybrid model is an improvement over the previously published model and that it is capable of predicting end-dialysis systemic iCa levels with improved accuracy and precision even in a citrate dialysis setting which was much different from the original derivation cohort.

Chronic medical conditions and risk of sepsis

BACKGROUND

We sought to determine the associations between baseline chronic medical conditions and future risk of sepsis.

METHODS

Longitudinal cohort study using the 30,239 community-dwelling participants of the REGARDS cohort. We determined associations between baseline chronic medical conditions and incident sepsis episodes, defined as hospitalization for an infection with the presence of infection plus two or more systemic inflammatory response syndrome criteria.

RESULTS

Over the mean observation time of 4.6 years (February 5, 2003 through October 14, 2011), there were 975 incident cases of sepsis. Incident sepsis episodes were associated with older age (p<0.001), white race (HR 1.39; 95% CI: 1.22-1.59), lower education (p<0.001) and income (p<0.001), tobacco use (p<0.001), and alcohol use (p = 0.02). Incident sepsis episodes were associated with baseline chronic lung disease (adjusted HR 2.43; 95% CI: 2.05-2.86), peripheral artery disease (2.16; 1.58-2.95), chronic kidney disease (1.99; 1.73-2.29), myocardial infarction 1.79 (1.49-2.15), diabetes 1.78 (1.53-2.07), stroke 1.67 (1.34-2.07), deep vein thrombosis 1.63 (1.29-2.06), coronary artery disease 1.61 (1.38-1.87), hypertension 1.49 (1.29-1.74), atrial fibrillation 1.48 (1.21-1.81) and dyslipidemia 1.16 (1.01-1.34). Sepsis risk increased with the number of chronic medical conditions (p<0.001).

CONCLUSIONS

Individuals with chronic medical conditions are at increased risk of future sepsis events.

A brief review of external mass balance and internal calcium redistribution in dialysis patients--is calcium a uremic toxin?

Recent debates between 2 schools of thought on calcium mass balance in dialysis patients and its relevance to disease--one emphasizing external calcium mass balance, and the other, internal calcium redistribution--have created controversy. Due to decreased ability to excrete calcium and loss of endocrine function by the kidney, patients suffering from chronic kidney disease, particularly when requiring dialysis, demonstrate varying degrees of positive or negative calcium balance, vitamin D deficiency, and secondary hyperparathyroidism. Consequently, patients are prone to bone demineralization, with diminished bone strength, and are thus prone to fractures that substantially worsen morbid outcomes in this population. However, intra- and interdialytic positive calcium mass balance creates complications of a different kind, which include the occurrence of vascular and cardiac disease and reduced survival. This review aims to shed light on the mechanisms of and relationships between external calcium mass balance and internal calcium redistribution and their consequences. It also discusses the potential to improve current regimens by means of diffusive and convective calcium mass transfer for the achievement of neutral calcium mass balance.

Effect of dialysate calcium concentrations on parathyroid hormone and calcium balance during a single dialysis session using bicarbonate hemodialysis: a crossover clinical trial

BACKGROUND

In bicarbonate-based hemodialysis, dialysate total calcium (tCa) concentration may have effects on mineral metabolism.

STUDY DESIGN

Randomized crossover trial of 3 dialysate tCa concentrations (2.5, 2.75, and 3.0 mEq/L).

SETTING & PARTICIPANTS

22 stable anuric uremic patients underwent three 4-hour bicarbonate hemodialysis sessions with the 3 different dialysate tCa concentrations using a single-pass batch dialysis system.

OUTCOMES

Hourly measurements of plasma water ionized calcium (iCa) and plasma parathyroid hormone (PTH) concentrations. tCa mass balances were measured from the dialysate side.

RESULTS

Hourly plasma water iCa concentrations were higher with a dialysate tCa concentration of 3.0 compared with 2.75 and 2.5 mEq/L (P < 0.05), as were iCa concentrations at the end of dialysis sessions (2.66 ± 0.1, 2.56 ± 0.12, and 2.4 ± 0.08 mEq/L, respectively; P < 0.001). Mean tCa mass balance values (diffusion gradient from the dialysate to the patient) were positive with all dialysate tCa concentrations and increased progressively with dialysate tCa concentration (75 ± 122, 182 ± 125, and 293 ± 228 mg, respectively; P < 0.001). Plasma PTH levels increased during dialysis using dialysate tCa concentration of 2.5 mEq/L (mean increase, 225 ± 312 pg/mL) and decreased with dialysate tCa concentrations of 2.75 and 3.0 mEq/L (mean decreases, 68 ± 325 and 99 ± 432 pg/mL, respectively).

LIMITATIONS

Small sample size and lack of measurement of total-body calcium mass balances.

CONCLUSIONS

A dialysate tCa concentration of 2.75 mEq/L might be preferable to 2.5 or 3.0 mEq/L because it is associated with mildly positive tCa mass balance values, plasma water iCa levels in the reference range, and stable PTH levels during dialysis.