Phosphorus control in peritoneal dialysis patients

A 6-Month clinical practice pilot study of sucroferric oxyhydroxide on nutritional status in patients on peritoneal dialysis

Background

Hyperphosphatemia is common in patients on peritoneal dialysis (PD). Restricting dietary phosphorus often leads to a decrease in protein intake, which may result in hypoalbuminemia. The high pill burden of phosphate binders may also contribute to compromised appetite and dietary intake. Hypoalbuminemia is associated with an increased risk of morbidity and mortality in PD patients. The goal of this study was to determine if sucroferric oxyhydroxide improves albumin and self-reported measures of appetite in PD patients.

Methods

We performed a prospective, open-label, 6-month, pilot study of 17 adult PD patients from the Denver Metro Area. Patients had to use automated peritoneal dialysis for ≥ 3 months, have a serum albumin ≤ 3.8 g/dL, and have serum phosphate ≥ 5.5 mg/dL or ≤ 5.5 mg/dL on a binder other than SO. SO was titrated to a goal serum phosphate of < 5.5 mg/dL. The primary outcome was change in serum phosphate, albumin, and phosphorus-attuned albumin (defined as albumin divided by phosphorus) over 6 months.

Results

The mean (SD) age and dialysis vintage was 55 ± 13 years and 3.8 ± 2.7 years, respectively. Participants’ serum phosphate significantly decreased with fewer phosphate binder pills/day after switching to SO. There was no change in serum albumin, appetite, or dietary intake. However, participants had significant improvements in phosphorus-attuned albumin.

Conclusion

The transition to SO improved phosphorus control, phosphorus-attuned albumin, and pill burden. There were no significant changes in self-reported appetite or dietary intake during the study. These findings suggest that PD patients maintained nutritional status with SO therapy.

Trial registration

First registered at ClinicalTrials.gov (NCT04046263) on 06/08/2019.

Serum Phosphorus Levels are Associated with Intradialytic Hypotension in Hemodialysis Patients

BACKGROUND

Intradialytic hypotension (IDH) is a common serious complication in hemodialysis (HD) patients. Hyperphosphatemia is also common in HD patients and promotes vascular calcification. Given the association between vascular calcification and IDH, we investigated the association between IDH and serum phosphorus in HD patients.

METHODS

We enrolled 173 patients who received HD for 3 months or more. IDH was defined as a nadir systolic blood pressure (SBP) <90 mm Hg or as a decrease in SBP ≥20 mm Hg or a decrease in mean arterial pressure by 10 mm Hg with the occurrence of hypotension-related symptoms requiring intervention. Serum phosphorus levels were analyzed both as a continuous variable and as a categorical variable.

RESULTS

IDH occurred in 40 (23.1%) of the 173 patients. The mean phosphorus level was 4.9 mg/dL. A 1 mg/dL higher serum phosphorus resulted in a 2.1-fold greater odds of IDH. The fully adjusted odds ratio (OR) and 95% confidence interval (CI) were 2.11 (1.48-3.01). High categorized phosphorus levels were also associated with IDH. The highest tertile of serum phosphorus was associated with 6.5-fold greater odds of developing IDH compared to the referent group (the middle tertile of serum phosphorus, 4.0-<5.3 mg/dL); the fully adjusted OR (95% CIs) were 6.53 (2.23-19.09). In subgroup analyses, diabetes and pre-dialysis SBP modified the association between IDH and phosphorus levels, with a more pronounced association in diabetic patients and pre-dialysis SBP ≥140 mm Hg.

CONCLUSION

In HD patients, higher phosphorus levels were associated with an increased occurrence of IDH.

High prevalence of biochemical disturbances of chronic kidney disease - mineral and bone disorders (CKD-MBD) in a nation-wide peritoneal dialysis cohort: are guideline goals too hard to achieve?

INTRODUCTION

Chronic kidney disease - mineral and bone disorders (CKD-MBD) are common in dialysis patients. Definition of targets for calcium (Ca), phosphorus (P), parathormone (iPTH), and alkaline phosphatase (ALP) and their treatment recommendations, are provided by international guidelines. There are few studies analyzing CKD-MBD in peritoneal dialysis (PD) patients and the impact of guidelines on mineral metabolism control. The aim of our study was to describe the prevalence of biomarkers for CKD-MBD in a large cohort of PD patients in Brazil.

METHODS

Data from the nation-wide prospective observational cohort BRAZPD II was used. Incident patients were followed between December 2004 and January 2011. According to KDOQI recommendations, reference ranges for total Ca were 8.4 to 9.5 mg/dL, for P, 3.5 to 5.5 mg/dL, for iPTH, 150-300 pg/mL, and for ALP, 120 U/L.

RESULTS

Mean age was 59.8 ± 16 years, 48% were male, and 43% had diabetes. In the beginning, Ca was 8.9 ± 0.9 mg/dL, and 48.3% were on the KODQI target. After 1 year, Ca increased to 9.1 ± 0.9 mg/dL and 50.4% were in the KDOQI preferred range. P at baseline was 5.2 ± 1.6 mg/dL, with 52.8% on target, declining to 4.9 ± 1.5 mg/dL after one year, when 54.7% were on target. Median iPTH at baseline was 238 (P25% 110 - P75% 426 pg/mL) and it remained stable throughout the first year; patients within target ranged from 26 to 28.5%. At the end of the study, 80% was in 3.5 meq/L Ca dialysate concentration, 66.9% of patients was taking any phosphate binder, and 25% was taking activated vitamin D.

CONCLUSIONS

We observed a significant prevalence of biochemical disorders related to CKD-MBD in this dialysis population.

In vitro efficacy and safety of a system for sorbent-assisted peritoneal dialysis

A system for sorbent-assisted peritoneal dialysis (SAPD) was designed to continuously recirculate dialysate via a tidal mode using a single lumen peritoneal catheter with regeneration of spent dialysate by means of sorbent technology. We hypothesize that SAPD treatment will maintain a high plasma-to-dialysate concentration gradient and increase the mass transfer area coefficient of solutes. Thereby, the SAPD system may enhance clearance while reducing the number of exchanges. Application is envisaged at night as a bedside device (12 kg, nighttime system). A wearable system (2.0 kg, daytime system) may further enhance clearance during the day. Urea, creatinine, and phosphate removal were studied with the daytime and nighttime system (n = 3 per system) by recirculating 2 liters of spent peritoneal dialysate via a tidal mode (mean flow rate: 50 and 100 mL/min, respectively) for 8 h in vitro. Time-averaged plasma clearance over 24 h was modeled assuming one 2 liter exchange/day, an increase in mass transfer area coefficient, and 0.9 liters ultrafiltration/day. Urea, creatinine, and phosphate removal was 33.2 ± 4.1, 5.3 ± 0.5, and 6.2 ± 1.8 mmol, respectively, with the daytime system and 204 ± 28, 10.3 ± 2.4, and 11.4 ± 2.1 mmol, respectively, with the nighttime system. Time-averaged plasma clearances of urea, creatinine and phosphate were 9.6 ± 1.1, 9.6 ± 1.7, and 7.0 ± 0.9 mL/min, respectively, with the nighttime system and 10.8 ± 1.1, 13.4 ± 1.8, and 9.7 ± 1.6 mL/min, respectively, with the daytime and nighttime system. SAPD treatment may improve removal of uremic toxins compared with conventional peritoneal dialysis, provided that peritoneal mass transport will increase.

Aortic stenosis in patients with kidney failure: Is there an advantage for a PD-first policy?

Aortic stenosis (AS) is the most common valvular disease. It is twice as prevalent in patients with kidney failure as compared to the general population. In addition, AS progresses at a faster rate and is associated with a higher risk of death and poorer quality of life in patients on dialysis. Chronic kidney disease–mineral and bone disorder (CKD-MBD), inflammation, and hemodynamic disturbances contribute to the pathophysiology and progression of AS. Whether the type of dialysis modality, that is, hemodialysis (HD) versus peritoneal dialysis (PD), has a differential impact on the development and progression of AS in patients with kidney failure remains debated. Recent data indicate that the prevalence of valvular calcifications might be lower and the development of AS delayed in PD patients, as compared to those treated with HD. This could be accounted for by several mechanisms including reduced valvular shear stress, better preservation of residual kidney function (with better removal of protein-bound uremic toxins and CKD-MBD profile), and lower levels of systemic inflammation. Given the high morbidity and mortality rates related to interventional procedures in the population with kidney failure, surgical and transcatheter aortic valve replacement should be considered in selected patients with severe AS. Strategies slowing down the progression of aortic valve remodeling should remain the cornerstone in the management of individuals with kidney failure and mild to moderate AS. This review explores the potential benefits of PD in patients with kidney failure and AS and provides some clues to help clinicians in the decision-making process when options for kidney replacement therapy are considered in patients with AS.

Diabetes Mellitus and Younger Age Are Risk Factors for Hyperphosphatemia in Peritoneal Dialysis Patients

Hyperphosphatemia has been associated with adverse outcomes in patients with end stage kidney disease (ESKD). The purpose of this study was to determine risk factors for hyperphosphatemia in ESKD patients treated with peritoneal dialysis (PD). This information will be used to develop a patient specific phosphate binder application to facilitate patient self-management of serum phosphate. Adult PD patients documented their food, beverage, and phosphate binder intake for three days using a dietitian developed food journal. Phosphate content of meals was calculated using the ESHA Food Processor SQL Software (ESHA Research, Salem, UT, USA). Clinic biochemistry tests and an adequacy assessment (Baxter Adequest program) were done. Univariate logistic regression was used to determine predictors of serum phosphate >1.78 mmol/L. A multivariable logistic regression model was then fit including those variables that achieved a significance level of p < 0.20 in univariate analyses. Sixty patients (38 men, 22 women) completed the protocol; they were 60 ± 17 years old, 50% had a history of diabetes mellitus (DM) and 33% had hyperphosphatemia (PO₄ > 1.78 mmol/L). In univariate analysis, the variables associated with an increased risk of hyperphosphatemia with a p-value < 0.2 were male gender (p = 0.13), younger age (0.07), presence of DM (0.005), higher dose of calcium carbonate (0.08), higher parathyroid serum concentration (0.08), lower phosphate intake (0.03), lower measured glomerular filtration rate (0.15), higher phosphate excretion (0.11), and a higher body mass index (0.15). After multivariable logistic regression analysis, younger age (odds ratio (OR) 0.023 per decade, 95% confidence interval (CI) 0.00065 to 0.455; p = 0.012), presence of diabetes (OR 11.40, 95 CI 2.82 to 61.55; p = 0.0003), and measured GFR (OR 0.052 per mL/min decrease; 95% CI 0.0025 to 0.66) were associated with hyperphosphatemia. Our results support that younger age and diabetes mellitus are significant risk factors for hyperphosphatemia. These findings warrant further investigation to determine the potential mechanisms that predispose younger patients and those with DM to hyperphosphatemia.

Association Between Hypertension and Residual Renal Function in Hemodialysis Patients

Introduction. Cardiovascular diseases are the leading cause of death in hemodialysis patients. The decline of residual renal function increases the prevalence and severity of risk factors of cardiovascular morbidity and mortality in these patients. Hypertension is common in dialysis patients and represents an important independent factor of survival in these patients.

Methods. The study included 77 patients who are on chronic HD for longer than 3 months. Depending on the measured residual diuresis patients were divided into two groups. The study group consisted of patients with residual diuresis >250 ml/day, while patients from control group had residual diuresis <250 ml/day. All patients had their blood pressure measured before 10 consecutive hemodialysis treatments. Collected data were statistically analyzed using SPSS 16.0.

Results. The study included 77 hemodialysis patients, mean age of 56.56±14.6 years and mean duration of hemodialysis treatment of 24.0 months. Of the total number of patients, 39(50.6%) had preserved residual renal function. Hypertension was more common in the group of patients who did not have preserved residual renal function (68.4% vs 25.6%). There was statistically significant negative linear correlation between the volume of residual urine output and the residual clearance of urea and values of systolic blood pressure [(rho=−0.388; p<0.0001); (rho=−0.392; p<0.0005)], values of mean arterial pressure [(rho =−0.272; p<0.05); (rho=−0.261; p=0.023; p<0.05)] and values of pulse pressure in hemodialysis patients [(rho =−0.387; p<0.001); (rho=−0.400; p<0.0005)].

Conclusions. Residual renal function plays an important role in controlling blood pressure in patients on hemodialysis. More attention should be directed to preserve residual renal function, and after the start of hemodialysis by avoiding intensive ultrafiltration with optimal antihypertensive therapy.

Biomarkers Associated with Vascular Calcification in Peritoneal Dialysis

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BACKGROUND

Vascular calcification is strongly associated with cardiovascular disease and mortality. However, some factors related to vascular calcification in patients with end-stage renal disease receiving peritoneal dialysis (PD) remain unknown. This study aimed to evaluate the associations of osteoprotegerin (OPG), osteopontin (OPN), osteocalcin (OCN), fibroblast growth factor 23 (FGF-23), magnesium, and phosphate clearance with vascular calcification in PD subjects, assessed by plain radiographs. ♦

METHODS

Simple vascular calcification scores (SVCS) obtained from plain X-rays of the pelvis and hands, and the Kauppila Index (KI) from lateral lumbar X-rays were assessed in 76 adults receiving PD for ≥ 6 months (43 women, median age 39 years, median time on PD 1.4 years). Levels of OPG, OPN, OCN, and FGF-23 were determined by luminometry. ♦

RESULTS

Serum OPG levels were higher in subjects with vascular calcification (n = 22 with SVCS > 3; n = 19 with KI > 7) compared with those with less calcification (p < 0.001). Spearman's correlation coefficients between OPG and SVCS and KI were r = 0.49 and r = 0.51, respectively (both p < 0.001). Subjects with vascular calcification had significantly lower renal phosphate clearance. Multiple regression analysis showed that vascular calcification assessed by SVCS was associated with age (r = 0.2, p = 0.042), diabetes mellitus (r = 2.4, p < 0.001), body mass index (BMI) (r = 0.09, p = 0.037), and OPG (r = 0.22, p = 0.001). Vascular calcification assessed by KI was associated with age (r = 0.16, p < 0.001), time on PD (r = 0.54, p = 0.001) and OPG (r = 0.08, p = 0.04). Osteocalcin, OPN, FGF-23, and magnesium were not associated with vascular calcification. ♦

CONCLUSIONS

Higher levels of OPG were consistently associated with vascular calcification in subjects on PD.

Hyperphosphatemia as an independent risk factor for coronary artery calcification progression in peritoneal dialysis patients

Background

Coronary artery calcification (CAC) is associated with cardiovascular mortality in end-stage renal disease (ESRD) patients. The present study aimed to identify modifiable risk factors for CAC progression in peritoneal dialysis (PD) patients.

Methods

Adult patients who received regular PD for more than 6 months and underwent a series of coronary artery calcification score (CaCS) measurements by multislice spiral computed tomography (MSCT) with an interval of ≥ 6 months were included in this observational cohort study. The demographic characteristics and clinical data, including laboratory data and adequacy of PD, were collected. Curve estimation was used to fit the straight line and obtain the slope. Binary logistic regression was performed to identify the independent risk factors for CAC progression in the PD patients, and multivariate linear regression was conducted to identify factors associated with hyperphosphatemia.

Results

A total of 207 adult patients on PD (116 men, 56.0 %) with a mean age of 59.8 ± 15.9 years were recruited to this study, and 157 of them (75.8 %) received three or more CaCS assessments. The patients were divided into a slow group (n = 137) and a rapid group (n = 70) according to the linear regression slope or the average speed of development. The follow-up time was 33.0 ± 18.8 months. Multivariate logistic regression revealed that age and serum phosphate level were independent risk factors for CAC progression after adjustments. Multivariate linear regression revealed that hyperphosphatemia was associated with elevations in the transferrin and serum albumin levels and normalized protein catabolic rate (nPCR) and reductions in the hemoglobin level, residual Ccr, and PD Ccr.

Conclusions

Hyperphosphatemia is an independent risk factor for CAC progression, and the serum phosphate level may be associated with protein intake and PD adequacy. These results provide important information for the clinical management of ESRD patients.

Evaluation of a mineral metabolism protocol in peritoneal dialysis patients

OBJECTIVES

To determine if there is an improvement in the number of peritoneal dialysis (PD) patients who meet target goals for serum phosphorus and parathyroid hormone (iPTH) after the implementation of a dietitian led mineral metabolism protocol.

DESIGN

Retrospective, comparative, analytic study.

SETTING

Fraser Health Authority PD units in Abbotsford and New Westminster, British Columbia.

SUBJECTS

One hundred fourty patients from 2009 and 139 patients from 2011 stable on PD for a minimum of 3 months.

MAIN OUTCOME MEASURE

Change in number of patients meeting target goals for serum phosphorus and iPTH after the implementation of a mineral metabolism protocol for 6 months.

RESULTS

After 6 months of the protocol being initiated, there was no significant difference in number of patients meeting serum phosphorus targets (82.0% vs. 74.5%, P = .126); however, a significant increase in the number of patients who met target iPTH range (60.4% vs. 48.5%, P = .048) was shown.

CONCLUSIONS

Use of a mineral metabolism protocol by dietitians in PD units supports an improvement in iPTH targets.

Analysis of serum phosphate control and phosphate binder utilization in incident hemodialysis patients

The purpose of this study was to conduct a retrospective analysis of serum phosphate level variability in patients new to hemodialysis (HD) and to identify patient characteristics associated with this variability. The medical records of 47,742 incident HD patients attending US outpatient dialysis centers between January 1, 2006 and March 31, 2009 were analyzed. Monthly mean serum phosphate levels determined over a 6-month evaluation period (months 4–9 after HD initiation) were assigned to one of three strata: low (<1.13 mmol/L [<3.5 mg/dL]); target (1.13–1.78 mmol/L [3.5–5.5 mg/dL]); or high (>1.78 mmol/L [>5.5 mg/dL]). Patients were classified into one of six serum phosphate variability groups based on variability among monthly mean phosphate levels over the 6-month evaluation period: consistently target; consistently high; high-to-target; high-to-low; target-to-low; or consistently low. Only 15% of patients (consistently target group) maintained monthly mean serum phosphate levels within the target range throughout the 6-month evaluation period. Age, Charlson comorbidity index, serum phosphate, and intact parathyroid hormone levels prior to HD initiation were strongly associated (P<0.001) with serum phosphate levels after HD initiation. Overall patient-reported phosphate binder usage increased from 35% at baseline to 52% at end of study. The low proportion of patients achieving target phosphate levels and low rates of phosphate binder usage observed during the study suggest that alternative strategies could be developed to control serum phosphate levels. Possible strategies that might be incorporated to help improve the management of hyperphosphatemia in incident HD patients include dietary modification, dialysis optimization, and earlier and sustained use of phosphate binders.

Rationale and study design of a three-period, 58-week trial of ferric citrate as a phosphate binder in patients with ESRD on dialysis

Chronic kidney disease associated mineral and bone disorders arise as a result of aberrant bone mineral metabolism in patients with advancing levels of renal dysfunction and end-stage renal disease. One of the cornerstones of treatment is the use of phosphate-binding agents. We describe the rationale and study design for a clinical trial to assess the safety and efficacy of ferric citrate as a phosphate binder. This trial is a three-period, international, multicenter, randomized, controlled clinical trial to assess the safety and efficacy of ferric citrate as a phosphate binder, consisting of a 2-week washout period, a 52-week safety assessment period in which subjects are randomized to ferric citrate or active control, and a 4-week efficacy assessment period in which subjects randomized to ferric citrate in the safety assessment period are randomized to ferric citrate or placebo. Eligible subjects include end-stage renal disease patients who have been treated with thrice-weekly hemodialysis or peritoneal dialysis for at least 3 months in dialysis clinics in the United States and Israel. Primary outcome measure will be the effect of ferric citrate vs. placebo on the change in serum phosphorus. Safety assessments will be performed by monitoring adverse events, concomitant medication use, and sequential blood chemistries (including iron parameters, phosphorus, and calcium). This three-period trial will assess the efficacy of ferric citrate as a phosphate binder. If proven safe and efficacious, ferric citrate will likely provide an additional phosphate binder to treat chronic kidney disease associated mineral and bone disorders.

Clinical benefit of preserving residual renal function in dialysis patients: an update for clinicians

Residual renal function (RRF) remains important even after beginning of dialysis. RRF contributes significantly to the overall health and well-being of patients on dialysis. It plays an important role in maintaining fluid balance, phosphorus control, nutrition, and removal of middle molecular uremic toxins and shows inverse relationships with valvular calcification and cardiac hypertrophy in patients on dialysis. RRF may allow for a reduction in the duration of hemodialysis sessions and the need for dietary and fluid restrictions in both patients on peritoneal dialysis and hemodialysis. More importantly, the loss of RRF is a powerful predictor of mortality. This article will review the evidence supporting the importance of RRF on outcome and outline potential strategies that may better preserve RRF in patients on dialysis.

Acid-base balance in peritoneal dialysis patients: a Stewart-Fencl analysis

BACKGROUND

Evaluation of acid-base disorders using the Stewart-Fencl principle is based on assessment of independent factors: strong ion difference (SID) and the total concentration of non-volatile weak acids (Atot). This approach allows for a more detailed evaluation of the cause of acid-base imbalance than the conventional bicarbonate-centered approach based on the Henderson-Hasselbalch principle, which is a necessary yet insufficient condition to describe the state of the system. The aim of our study was to assess acid-base disorders in peritoneal dialysis (PD) patients using both of these principles.

METHODS

A total of 17 patients with chronic renal failure (10 men), aged 60.7 (22-84) years, treated by PD for 25.7 (1-147) months were examined. A control group included 17 healthy volunteers (HV) (8 males), with a mean age of 42.7 (22-77) years and normal renal function. Patients were treated with a solution containing bicarbonate (25 mmol/L) and lactate (15 mmol/L) as buffers; eleven of them used, during the nighttime dwell, a solution with icodextrin buffered by lactate at a concentration of 40 mmol/L. The following equations were employed for calculations of acid-base parameters according to the Stewart-Fencl principle. The first is SID = [Na+] + [K+] + 2[Ca(2+)] + 2[Mg(2+)] - [Cl-] - [UA-], where SID is the strong ion difference and [UA-] is the concentration of undetermined anions. For practical calculation of SID, the second equation, SID = [HCO3-] + [Alb-] + [Pi-], was used, where [Alb-] and [Pi-] are the charges carried by albumin and phosphates. The third is Atot, the total concentration of weak non-volatile acids, albumin [Alb] and phosphates [Pi].

RESULTS

The capillary blood pH in PD group was 7.41 (7.27-7.48), [HCO3-] levels 23.7 (17.6-29.5) mmol/L, SID 36.3 (29.5-41.3) mmol/L, sodium-chloride difference 39.0 (31.0-44.0) mmol/L, [Pi] 1.60 (0.83-2.54) mmol/L, and [Alb] 39.7 (28.8-43.4) g/L (median, min-max). Bicarbonate in blood correlated positively with SID (Rho = 0.823; p < 0.001), with the sodium-chloride difference (Rho = 0.649; p < 0.01) and pH (Rho = 0.754; p < 0.001), and negatively with residual renal function (Rho = -0.517; p < 0.05). Moreover, the sodium-chloride difference was also found to correlate with SID (Rho = 0.653; p < 0.01). While the groups of PD and HV patients did not differ in median bicarbonate levels, significantly lower median value of SID were observed in PD patients, 36.3 vs. 39.3 mmol/L (p < 0.01); additionally, PD patients were shown to have significantly lower mean value of serum sodium levels, 138 vs. 141 mmol/L (p < 0.01), and serum chlorides levels, 100 vs. 104 mmol/L (p < 0.001). Despite the higher [UA-] levels in PD patients, 9.1 vs. 5.4 mmol/L (p < 0.001), this parameter was not found to correlate with bicarbonate levels.

CONCLUSIONS

The results suggest that the decreased bicarbonate in PD patients results from a combination of decreased sodium-chloride difference and mildly increased unmeasured anions.