Mineral Metabolism In Hemodialysis Patients Research Articles

Acute effects of dietary phosphorus intake on markers of mineral metabolism in hemodialysis patients: post hoc analysis of a randomized crossover trial

Background Long-term dietary phosphorus excess influences disturbances in mineral metabolism, but it is unclear how rapidly the mineral metabolism responds to short-term dietary change in dialysis populations. Methods This was a post hoc analysis of a randomized crossover trial that evaluated the short-term effects of low-phosphorus diets on mineral parameters in hemodialysis patients. Within a 9-day period, we obtained a total of 4 repeated measurements for each participant regarding dietary intake parameters, including calorie, phosphorus, and calcium intake, and markers of mineral metabolism, including phosphate, calcium, intact parathyroid hormone (iPTH), intact fibroblast growth factor 23 (iFGF23), and C-terminal fibroblast growth factor 23 (cFGF23). The correlations between dietary phosphorus intake and serum mineral parameters were assessed by using mixed-effects models. Results Thirty-four patients were analyzed. In the fully adjusted model, we found that an increase in dietary phosphorus intake of 100 mg was associated with an increase in serum phosphate of 0.3 mg/dL (95% confidence intervals [CI], 0.2–0.4, p < .001), a decrease in serum calcium of 0.06 mg/dL (95% CI, −0.11 to −0.01, p = .01), an increase in iPTH of 5.4% (95% CI, 1.4–9.3, p = .01), and an increase in iFGF23 of 5.0% (95% CI, 2.0–8.0, p = .001). Dietary phosphorus intake was not related to cFGF23. Conclusions Increased dietary phosphorus intake acutely increases serum phosphate, iPTH, and iFGF23 levels and decreases serum calcium levels, highlighting the important role of daily fluctuations of dietary habits in disturbed mineral homeostasis in hemodialysis patients.

Impact of Weekly Teriparatide on the Bone and Mineral Metabolism in Hemodialysis Patients With Relatively Low Serum Parathyroid Hormone: A Pilot Study.

Adynamic bone disease in HD patients is characterized by skeletal resistance to parathyroid hormone (PTH) or suppression of PTH release, leading to a downregulated bone turnover and bone fracture. Hence, we examined the efficacy of weekly teriparatide for HD patients with low PTH indicating adynamic bone disease without a history of parathyroidectomy. Fifteen HD patients with low PTH were recruited in this prospective observational study. Of them, 10 received teriparatide for 12 months and five nontreated patients were enrolled as control. Primary outcomes were defined as the changes in bone mineral density and bone turnover markers. Bone mineral density at the lumbar spine increased by 3.7% and 2.5% at 6 and 12 months, respectively, and bone formation markers increased, while bone resorption markers did not change in the teriparatide group. At 12 months after teriparatide administration, endogenous PTH was secreted followed by the recovery of low bone turnover. 40% of patients in the teriparatide group dropped out due to adverse events and the most common adverse event was transient hypotension. This study suggests that weekly teriparatide for HD patients with low PTH in the absence of parathyroidectomy accelerates bone formation and bone turnover, leading to increased trabecular bone mass and secretion of endogenous PTH.

Frequent monitoring of mineral metabolism in hemodialysis patients with secondary hyperparathyroidism: associations with achievement of treatment goals and with adjustments in therapy.

Background: Dialysis guidelines in Japan recommend more frequent measurement of mineral metabolism markers than the Kidney Disease: Improving Global Outcomes guidelines. However, the extent to which frequent marker measurement contributes to achievement of target ranges and to therapy adjustment is unknown. Methods: This multicenter cohort study involved 3276 hemodialysis patients with secondary hyperparathyroidism. Data on laboratory measurements and drug prescriptions were collected every 3 months. Main exposures were frequencies of measuring serum calcium and phosphorus [weekly/biweekly/monthly (reference)] and serum parathyroid hormone (PTH) [monthly/bimonthly/trimonthly (reference)] levels. Outcomes were achievement of guideline-specified ranges of mineral metabolism markers when serum levels were over, and maintenance of ranges when levels were already within, respective specified ranges, use of intravenous vitamin D receptor activator (VDRA) and initiation of cinacalcet use. Associations were examined via generalized estimating equations. Results: When serum marker levels exceeded the target range, weekly measurement of calcium and phosphorus was positively associated with achievement of the guideline-specified calcium range [adjusted odds ratio (AOR): 1.57, 95% confidence interval (CI) 1.09–2.26] but not phosphorus range (AOR: 0.99, 95% CI 0.74–1.33). Monthly measurement of PTH was positively associated with achievement of the guideline-specified PTH range (AOR: 1.14, 95% CI 1.01–1.27). When serum marker levels were within the guideline-specified range, increased frequency of measurements was not associated with in-range maintenance of marker levels for any of the three mineral markers assessed. Regarding treatment regimen, relatively frequent measurement of serum calcium and phosphorus was positively associated with cinacalcet initiation and relatively frequent measurement of serum PTH with cinacalcet initiation and intravenous VDRA use. Conclusions: Our results suggest that increasing frequency of measurements is helpful when serum marker levels exceed the target range, partially via adjustment in the therapeutic regimen. We found no evidence that frequent measurements are helpful when mineral levels are already within target ranges.

Effects of lanthanum carbonate versus calcium carbonate on vascular stiffness and bone mineral metabolism in hemodialysis patients with type 2 diabetes mellitus: a randomized controlled trial

BackgroundVascular calcification contributes to cardiovascular disease in hemodialysis (HD) patients with diabetes. The randomized controlled trial reported here compared the effects of lanthanum carbonate (LC) and calcium carbonate (CC) on vascular stiffness assessed using brachial-ankle pulse wave velocity (ba-PWV), intima-media thickness (IMT), bone mineral density (BMD), and serum markers of chronic kidney disease – mineral and bone disorder in such patients.MethodsBa-PWV, IMT, BMD, and the biomarkers osteocalcin (OC) and bone alkaline phosphatase (BAP) were examined in 43 type 2 diabetes HD patients treated with LC (n=21) or CC (n=22) for 2 years.ResultsForty-one patients completed the study (19, LC; 22, CC). The mean ba-PWV significantly increased only in the CC group (median: 2,280.5 to 2,402.5 cm/s, P<0.05), after 24-month treatment; it remained unchanged in the LC group (median: 1,830.5 to 2,018.3 cm/s). However, the difference between the groups did not reach statistical significance. Changes in IMT and BMD were not different between the two groups. Changes in serum phosphorus, corrected calcium, and intact parathyroid hormone levels were similar between the groups. The incidence of fracture was 0% (0/19) in the LC group, and 13.6% (3/22) in the CC group (P=0.2478). The OC/BAP ratio increased significantly in the LC group (median: 0.83 to 2.47), compared with in the CC group (median: 0.77 to 1.40) (P=0.036).ConclusionFrom this study, in Japanese type 2 diabetes HD patients, we conclude that 2-year treatment with LC might have slowed the progression of ba-PWV; however, it did not cause a difference in ba-PWV, IMT, BMD, or fracture, compared with CC. Further, LC increased the OC/BAP ratio to a greater extent than CC.

Cross-Talk Between Endothelin-1 and Mineral Metabolism in Hemodialysis Patients: a Cross-Sectional Study

Background:Endotheline-1 (ET-1), an endothelial mediator, influences on mineral metabolism; especially vascular calcification in uremic patients.Objectives:The aim of the present study was to evaluate of ET-1, high-sensitivity C-reactive protein (hs-CRP) and mineral metabolites as the main factors for vascular calcification and inflammation in hemodialysis (HD) patients.Patients and Methods:In this cross-sectional study, 46 chronic stable HD patients were selected from nephrology departments of Tabriz University of Medical Sciences affiliated hospitals and classified based on phosphorus (P), Ca-P product (Ca × P) and intact Parathyroid Hormone (iPTH) levels. We evaluated fasting serum ET-1and hs-CRP levels by the standard methods and compared with 46 healthy control subjects.Results:The levels of serum hs-CRP and ET-1 were significantly higher in the patient’s group compared with controls (4.40 ± 1.26 vs. 1.38 ± 1.61, P < 0.0001, and 2.31 ± 0.87 vs. 0.75 ± 0.48, P < 0.0001, respectively) and with regard to Ca × P product cut-off point (3.99 ± 0.78 vs. 5.33 ± 1.64, P < 0.0001, and 2 ± 0.73 vs. 3.04 ± 0.73, P < 0.0001 respectively). ET-1 was correlated significantly with hs-CRP level (r = 0.776, P < 0.0001). Serum P, Ca × P and iPTH levels directly and Ca indirectly were correlated with serum ET-1 in HD patients (r = 0.932, P < 0.0001, r = 0.766, P < 0.0001, r = 0.514, P < 0.0001, r = -0.538, P < 0.0001 respectively). Multiple regression analysis demonstrated that serum P were independently associated with ET-1 levels (β = 0.932, P < 0.0001).Conclusions:Serum P and iPTH levels were independently associated with ET-1 and those may play a role in development of endothelial dysfunction in chronic kidney disease.

Management of mineral metabolism in hemodialysis patients: discrepancy between interventions and perceived causes of failure.

Mineral and bone disorders (MBD) in patients undergoing hemodialysis (HD) are a major clinical complication. Current therapeutic strategies do not attain the expected results. The Italian audit on mineral metabolism was implemented to investigate MBD management through a "patient-oriented" approach. Clinical and laboratory data pertinent to MBD from 509 prevalent adult patients on chronic HD were recorded and examined (audit), after which individual strategies were elaborated to improve MBD control. Their effectiveness was evaluated 6 months after the audit (Post-6). The audit disclosed poor MBD control in a high percentage of patients (56 %). Low compliance to treatment was the major determinant of failure (in 43.5 % of cases). Logistic regression showed a direct correlation between high degree of compliance and the achievement of therapeutic targets, e.g. parathyroid hormone: odds ratio (OR) 2.48, p = 0.015. In contrast, a minority of the proposed interventions (14.7 %) included strategies to improve patient compliance. At Post-6, despite a significant increase in drug prescription (p < 0.05 vs. audit), the rate of successful MBD control was unchanged. Low compliance with treatment is a major, but still neglected, cause of failure in the achievement of MBD control in HD patients.

Reply to 'Management of mineral metabolism in haemodialysis patients: need for new strategies’

Reply to 'Management of mineral metabolism in haemodialysis patients: need for new strategies’

Effects of Switching From Calcium Carbonate to Lanthanum Carbonate on Bone Mineral Metabolism in Hemodialysis Patients

Phosphate binders are useful for the treatment of hyperphosphatemia in hemodialysis (HD) patients. This study was performed to examine the effects of switching from calcium carbonate (CC) to lanthanum carbonate (LC) on bone mineral metabolism and inflammatory markers in HD patients. We conducted 29 stable HD patients receiving CC, which was replaced by LC and followed-up for 12 weeks. Patients underwent determinants of blood chemistries such as serum calcium (Ca), phosphorus, parathyroid hormone (PTH) and vitamin D status, and interleukin-6 (IL-6) mRNA levels in whole blood cells were evaluated by real-time PCR just before and after the treatment with LC. Corrected Ca [corrected] levels were significantly reduced, but serum phosphorus levels (P levels) were unchanged after LC treatment. Switching to LC increased whole-PTH, osteocalcin, 1,25(OH)(2) D(3) levels and 1,25(OH)(2) D(3)/25(OH)D(3) ratio. 1,25(OH)(2) D(3)/25(OH)D(3) ratio was negatively correlated with HD duration. Furthermore, whole blood cell IL-6 mRNA levels were significantly reduced by LC treatment. We provided that the switching from CC to LC improved Ca overload and ameliorated vitamin D and inflammatory status in HD patients. These observations suggest that LC may play a protective role for the progression of atherosclerosis and vascular calcification in these patients.

Compliance with objectives based on different guidelines (KDIGO/S.E.N.) and analysis of the individual variability of mineral metabolism in haemodialysis patients in the medium term.

To assess the level of compliance and variability of mineral metabolism parameters over time in a sample of haemodialysis patients for the different ranges proposed (KDIGO guidelines/S.E.N recommendations) in both groups and individuals continuously. Every four months, we collected data on calcium, phosphorus, PTH and treatment in a sample of 44 patients followed up continuously for 32 months. We established the percentages of patients who complied with the objectives set for each parameter in both ranges: optimal (KDIGO) and acceptable (S.E.N.) in each control and the percentage that individually complied with the objectives in at least 75% of the determinations. Compliance with the objective using the optimal range improved, although PTH did not exceed 50%. Using the acceptable range, the objective was achieved in the three parameters in over 70% and over 50% of patients achieved the three simultaneously while using the optimal range, 30% was never achieved. Individually, compliance with the optimal range was continuously achieved in 52.3% (calcium), 45.5% (phosphorus) and in only one patient in PTH, while when using the acceptable range, compliance was achieved in 84.1% (calcium) and 70.5% (phosphorus and PTH). The use of less stringent criteria than the KDIGO guidelines in calcium, phosphorus and PTH objectives allows patients to remain continuously within appropriate ranges with less intervention and less individual variability.

Effect of post-dilutional on-line haemodiafiltration on serum calcium, phosphate and parathyroid hormone concentrations in uraemic patients

Strict control of serum calcium and phosphate concentrations is paramount to prevent secondary hyperparathyroidism in haemodialysis (HD) patients. Standard intermittent low-flux HD (Lf-HD) is not sufficient to reach this goal. The aim of this study was to evaluate the effect of on-line haemodiafiltration (Ol-HDF) on serum calcium (sCa), phosphate (sPO4) and parathyroid hormone (PTHint) concentrations. Of the 220 patients screened, 65 met the inclusion criteria for the study; 30 of whom agreed to participate in the study (Study group), the others were considered as the control group (Controls). Protocol for Study the group consisted of 6 months conventional Lf-HD (Period 1) and 6 months of post-dilutional Ol-HDF (Period 2). Controls continued their usual Lf-HD and were followed for 12 months. The main variables evaluated at the start and at the end of each period were sCa, sPO(4) and PTHint. The switchover from Lf-HD to Ol-HDF resulted in a significant reduction of sPO4 (from 5.1 ± 1.0 to 4.0 ± 0.7; P < 0.0001) and PTHint concentrations (from 307 ± 167 to 194 ± 98; P < 0.0001), no significant changes were found in both sCa concentrations (from 9.1 ± 0.7 to 8.9 ± 0.6) and phosphate binder dose. Kt/Vurea increased significantly, and beta(2) microglobulin concentrations decreased significantly. In the Controls, no significant variations of the same variables were observed over time, except for a significant increase in sevelamer intake. This study supports the idea that Ol-HDF could be better than Lf-HD in controlling mineral metabolism in HD patients.

Effect of Intravenous Saccharated Ferric Oxide on Serum FGF23 and Mineral Metabolism in Hemodialysis Patients

Background/Aims: Fibroblast growth factor-23 (FGF23) plays a central role in the development of hypophosphatemia and inappropriately low 1,25-dihydroxyvitamin D induced by iron therapy for iron-deficiency anemia. The aim of this study was to examine the effect of intravenous saccharated ferric oxide on serum FGF23 levels and mineral metabolism in hemodialysis patients. Methods: This prospective study enrolled 27 hemodialysis patients who had iron-deficiency anemia defined by a hemoglobin concentration <10.5 g/dl and serum ferritin <100 ng/ml. Intravenous saccharated ferric oxide at a dose of 40 mg was administered three times weekly over 3 weeks. The dose of active vitamin D and phosphate binders was kept unchanged. Serum FGF23, intact parathyroid hormone (PTH) and other parameters were prospectively monitored for 5 weeks. Results: Serum FGF23 levels were markedly elevated [3,453 (338–6,383) pg/ml] at baseline. After 3 weeks of intravenous saccharated ferric oxide treatment, serum FGF23 further increased to 4,701 (1,251–14,396) pg/ml, and returned to the baseline values after 2 weeks of observation. There was also a significant decrease in intact PTH but no changes in serum calcium and phosphorus. Conclusions: Intravenous saccharated ferric oxide induces further increase in elevated FGF23 levels in hemodialysis patients. This increase does not induce hypophosphatemia and inappropriately low 1,25-dihydroxyvitamin D in the absence of functioning kidney, but may result in transient PTH suppression – possibly by directly acting on the parathyroid.

Achievement of recommended treatment targets for bone and mineral metabolism in haemodialysis patients using paricalcitol: An observational study

Secondary hyperparathyroidism (SHPT) is a common problem among patients with chronic kidney disease (CKD) on haemodialysis. This study was conducted to assess the use, effectiveness and safety of intravenous paricalcitol in haemodialysis patients with various degrees of SHPT. This observational, multicentre, prospective study was conducted in 14 Swedish dialysis centres from May 2007 to June 2008 and included 92 haemodialysis patients with a diagnosis of SHPT associated with CKD. The decision to initiate treatment with intravenous paricalcitol was made by the treating physician. No treatment algorithms were provided. Mean patient age was 64 years. Of the 92 patients included, 74 had an intact parathyroid hormone (iPTH) level of >300 pg/ml at baseline. Median iPTH was 584 pg/ml in patients with a baseline PTH of >300 pg/ml. During follow-up there was a decrease in iPTH to 323 pg/ml at 6 months (-45%, p < 0.0001). In parallel, there was a small increase in serum calcium, but serum phosphorus and the calcium × phosphorus product remained unchanged. This study showed that intravenous paricalcitol substantially and safely decreased iPTH in haemodialysis patients with a baseline iPTH above the Kidney Disease Outcomes Quality Initiative recommended target range (150-300 pg/ml) and had minimal impact on serum minerals.

Avaliação da associação entre as alterações no metabolismo mineral e o prurido nos pacientes em hemodiálise

Uremic pruritus is the most frequent symptom in long-term hemodialysis patients. Abnormal laboratory parameters have been found with conflicting data. To correlate the prevalence of pruritus with alterations in mineral metabolism in hemodialysis patients. This was a case-control study. A hundred and five patients on maintenance hemodialysis were evaluated: a group of patients with pruritus and a control group. They answered a research protocol questionnaire; laboratory data were collected from medical records and the patients with pruritus filled out a visual analogue scale (VAS) to measure pruritus level. The mean age was 51.9 years; 59% of the patients were men and 43% of the patients had pruritus. Xeroderma occurred in 45% of the patients. High levels of calcium were demonstrated in 55% of the patients and 47% had pruritus. 60% of the patients had high phosphorus levels and 43% had pruritus. The Ca/P ratio was normal for all the patients. Parathyroid hormone was high in 95% of the patients, all of them referring pruritus. There was a statistically significant association between the group of patients with pruritus and xeroderma. Serum calcium and phosphorus levels, Ca/P ratio, PTHi and size of the dialyzer did not show a statistically significant association with pruritus. Therefore, we found an important relationship between xeroderma and pruritus, with no relation with the assessed laboratory parameters.

Dialysis Delivery in Canada and the United States: A View From the Trenches

Although the general framework for health care delivery is vastly different in Canada and the United States, the framework for dialysis delivery is less divergent. However, the 2 systems have evolved very differently. Examined during the past 20 years, it is apparent that the dialysis system in the United States has undergone profound change, whereas the system in Canada is relatively stagnant. Most of the change in the United States has been positive, and this evolutionary change is expected to continue. In Canada, a system that historically has worked reasonably well is now showing severe signs of suboptimal performance that would be expected to get worse if no effort is made to improve it. This article, written from the perspective of 2 academic clinicians, tries to describe similarities and differences, identify strengths and weaknesses, and serve as a catalyst for discussions about improving both systems. Just as no dialysis treatment modality is perfect, the same can be said for dialysis delivery systems. Empirical methods to objectively evaluate the impact of change must be included in the design and implementation of new initiatives in the United States and Canada.

Relationship Between the Weight of Parathyroid Glands and Their Secretion of Parathyroid Hormone in Hemodialysis Patients With Secondary Hyperparathyroidism

Secondary hyperparathyroidism is one of the common and important abnormalities of mineral metabolism in hemodialysis patients. In this study we investigated the relationship between the weight of individual parathyroid glands (PTG) and their secretion of parathyroid hormone (PTH). Sixty-four PTGs in 16 patients undergoing parathyroidectomy (PTx) at our hospital were included in this study. Patients' ages ranged from 34 to 68 years (60.3 +/- 6.6 years). They were undergoing maintenance dialysis therapy for 81-256 months (175.3 +/- 56.0 months). The cause of end-stage renal failure was chronic glomerulonephritis in all patients. We measured whole PTH (wPTH) levels before PTx and 15 min after the resection of each individual gland (Delta whole PTH). A positive correlation was found between the weight of individual gland and ultrasonography (US) size of individual PTG (r = 0.91, P < 0.001, N = 53). A positive correlation was found between the total mass of the gland and the total volume of PTG on US (r = 0.896, P < 0.001, N = 16). A positive correlation was found between the mass of each individual gland and Delta whole PTH (r = 0.625, P < 0.001, N = 64); however, massive PTGs did not secrete more whole PTH per unit mass (0.01 g). Determination of the volume of PTGs by US is a good indicator of their weight. Larger PTGs secrete more whole PTH per gland, whereas these PTGs did not have the ability to secrete more PTH per unit volume.

Disordered Mineral Metabolism in Hemodialysis Patients: An Analysis of Cumulative Effects in the Hemodialysis (HEMO) Study

Serum markers of disordered mineral metabolism have been associated with adverse outcomes in patients requiring long-term dialysis therapy. Although the values of these markers often evolve over time, no study has examined the accumulated effects of these abnormalities on important clinical end points. Retrospective cohort study. 1,846 prevalent hemodialysis patients randomly assigned in the Hemodialysis (HEMO) Study. Serum phosphorus, calcium, calcium-phosphorus (Ca x P) product, and intact parathyroid hormone, each analyzed at the time of randomization (baseline), as a standard time-dependent covariate and as a cumulative time-dependent covariate. All-cause mortality and the composite of all-cause mortality and first cardiac hospitalization. Cox proportional hazards models. In all analyses, serum phosphorus level greater than 6 mg/dL was associated with a heightened risk of mortality of approximately 25% compared with phosphorus values of 4.1 to 5 mg/dL. Serum calcium level greater than 11 mg/dL was associated with a 60% greater risk of death, but only when this parameter was analyzed as either a time-dependent or cumulative time-dependent variable. Ca x P product greater than 50 mg(2)/dL(2) was strongly associated with mortality, but only when assessed cumulatively. Similar relationships were observed when phosphorus, calcium, and Ca x P product values were related to the composite end point of all-cause mortality and first cardiac hospitalization. No relationships between baseline, time-dependent, and cumulative time-dependent intact parathyroid hormone levels and the outcomes of interest were observed. Residual confounding, lack of access to patient information before randomization in the HEMO Study, and concerns regarding generalizability given changes in practice patterns since the completion of the HEMO Study. Cumulative time-dependent analyses provide a different framework for analyzing the impact of factors that may mediate adverse events in hemodialysis patients. Our findings support maintaining serum phosphorus levels at less than 6 mg/dL, calcium levels at less than 11 mg/dL, and Ca x P product at less than 50 mg(2)/dL(2).

Effects of 22‐Oxacalcitriol and Calcitriol on PTH Secretion and Bone Mineral Metabolism in a Crossover Trial in Hemodialysis Patients With Secondary Hyperparathyroidism

The purpose of this crossover comparison study is to elucidate the differences between the effects of a novel calcitriol analog, 22-oxacalcitriol, and calcitriol on parathyroid hormone (PTH) and bone mineral metabolism in hemodialysis patients with secondary hyperparathyroidism (SHPT). Twenty-three patients with moderate to severe SHPT were included in a random 2 x 2 crossover trial with two vitamin D analogs (12 weeks for each treatment). Two patients withdrew during the run-in period for personal reasons. Serum electrolyte, bone metabolic marker, intact PTH (iPTH) and whole PTH (wPTH) levels were measured periodically. The primary endpoint measure was a decrease in serum iPTH level, and the secondary outcome measures included changes in serum calcium (Ca), phosphate (P), and metabolic bone marker levels. Both treatments decreased iPTH and wPTH levels by similar degrees. Serum Ca, P, and Ca x P product levels at the end of each treatment were comparable and the frequencies of hypercalcemia and hyperphosphatemia were also similar during each treatment period. 22-Oxacalcitriol significantly decreased the levels of bone metabolic markers, namely, bone-specific alkaline phosphate, intact osteocalcin, pyridinoline, and cross-linked N-telopeptide of type I collagen, after a 12-week treatment. In contrast, calcitriol did not change any of the levels of bone metabolic markers. The present study showed that 22-oxacalcitriol is equally effective for PTH suppression, and Ca and P metabolism. In addition, 22-oxacalcitriol might have putative actions on bone remodeling independent of its PTH suppression. Further study is necessary to confirm the effects of 22-oxacalcitriol on bone metabolism in SHPT.

Calcium in Chronic Kidney Disease: Recommended Intake and Serum Targets

Abnormal mineral metabolism has the potential to significantly increase mortality in patients with chronic kidney disease, especially by the time renal replacement therapy is required. While excess phosphorus and hyperphosphatemia have long been identified as risks for increased morbidity and mortality, the roles of calcium load and serum calcium levels have been less clear. Calcium-based recommendations in the K/DOQI Clinical Practice Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease were labeled as expert opinion. The rationale behind the opinion-based recommendations is reviewed along with additional supportive information that has become available since the bone and mineral guidelines were published.

Low-calcium dialysate improves mineral metabolism in hemodialysis patients

The Kidney Disease Outcomes Quality Initiative (K/DOQI) Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease recommend 1.25 mmol/l Ca dialysate for both hemodialysis and peritoneal dialysis, while 1.5 mmol/l Ca dialysate has been used in our dialysis center. Therefore, we switched the dialysate calcium concentration from 1.5 - 1.25 mmol/l and observed the effects on serum calcium (S-Ca), phosphorus (S-P), 1-84 parathyroid hormone (whole PTH, w-PTH), bone-specific alkaline phosphatase (BAP), and tartrate-resistant acid phosphatase isoform 5b (TRACP-5b) for 6 months in 58 hemodialysis patients. Prescription of active vitamin D (VD) metabolites and Ca carbonate was increased in response to the changes in laboratory data. Decrease of S-Ca was evident at 2 weeks and S-Ca remained low for 6 months. Transient elevation of S-P, which might be caused by stimulated bone resorption, was observed after the switch. In patients with low PTH (w-PTH less than 90 pg/ml before the switch), continuous increase of w-PTH, BAP, and TRACP-5b was observed. This appeared to be a favorable response because the risk ofadynamic bone disease was high in this group of patients. On the other hand, acute elevation of the 3 parameters was well-controlled in patients with moderate and high PTH (w-PTH from 90 - 180 pg/ml, w-PTH more than 180 pg/ml, respectively) by increased dosage of active VD. These results demonstrate that 1.25 mmol/l Ca dialysate improved mineral metabolism by lowering S-Ca and releasing oversuppression of PTH. Our data also suggest that appropriate use of active VD could prevent acute rise of PTH.

Review of dialysate calcium concentration in hemodialysis

The dialysate calcium (Ca) concentration for hemodialysis (HD) patients can be adjusted to manage more optimally the body's Ca and phosphate balance, and thus improve bone metabolism as well as reduce accelerated arteriosclerosis and cardiovascular mortality. The appropriate dialysate Ca concentration allowing this balance should be prescribed to each individual patient depending on a multitude of variable factors relating to Ca load. A lower dialysate Ca concentration of 1.25 to 1.3 mmol/L will permit the use of vitamin D supplements and Ca-based phosphate binders in clinical practice, with much less risk of Ca loading and resultant hypercalcemia and calcification. Low Ca baths are useful in the setting of adynamic bone disease where an increase in bone turnover is required. However, low Ca levels in the dialysate may also predispose to cardiac arrhythmias and hemodynamically unstable dialysis sessions with intradialytic hypotension. Higher Ca dialysate is useful to sustain normal serum Ca levels where patients are not taking Ca-based binders or if Ca supplements are not able to normalize serum levels. Suppression of hyperparathyroidism is also effective with dialysate Ca of 1.75 mmol/L, but hypercalcemia, metastatic calcification, and oversuppression of parathyroid hormone are risks. Dialysate Ca of 1.5 mmol/L may be a compromise between bone protection and reduction in cardiovascular risk for conventional HD and is a common concentration used throughout the world. The increase in longer, more frequent dialysis such as short-daily and nocturnal HD, however, provides another challenge with regard to optimal dialysate Ca levels and higher levels of 1.75 mmol/L are probably indicated in this setting. Difficulties in determining the ideal dialysate Ca occur because of the complex pathophysiology of bone and mineral metabolism in HD patients and there needs to be a balance between dialysis prescription and other treatment modalities. To optimize management of the abnormal Ca balance, other aspects of this disorder need to be more fully clarified and, with evolving medications for phosphate control and treatment of secondary hyperparathyroidism, as well as the emergence of a multitude of different HD regimes, further studies are required to make definitive recommendations. At present, we need to maintain flexibility with HD treatments and so dialysate Ca needs to be individualized to meet the specific requirements of patients by optimizing management of renal bone disease and simultaneously reducing metastatic calcification and cardiovascular disease.