Phosphorus balance with daily dialysis

Phosphorus balance calculator: an individualized tool for treatment of hyperphosphatemia in hemodialysis patients

BACKGROUND

Lack of evaluations of the dietary phosphorus and dialysis phosphorus removal in daily clinical practice are common obstacles to assessing phosphorus balance and controlling phosphorus in hemodialysis patients. We aimed to investigate whether individualized therapy using a phosphorus balance calculator improves phosphorus control.

METHODS

A randomized, open-label, multicenter, 4-week clinical trial was conducted. A total of 119 maintenance hemodialysis patients aged 18-85 years old and with serum phosphorus level >1.45 mmol/L from three university teaching hospitals in Shanghai were enrolled. Patients were randomized in a 1:1 ratio to individualized therapy (n = 60) or conventional therapy (n = 59). The primary outcome was the serum phosphorus concentration after 4-week treatment. Secondary outcomes included the serum calcium and parathyroid hormone (PTH) concentrations, changes in serum phosphorus, calcium and PTH concentrations, and the proportion of patients achieving target ranges of serum phosphorus, calcium and PTH after 4-week treatment.

RESULTS

Among 119 randomized participants [mean age 62 years; 68 male (57%)], 116 completed the trial. Using the phosphorus balance calculator, the individualized group achieved a better phosphorus balance state and significantly reduced serum phosphorus (1.62 ± 0.45 mmol/L versus 1.85 ± 0.45 mmol/L, P = .006), increased the proportions of patients achieving target serum phosphorus range (41% versus 18%, P = .006) and had greater adjusted mean difference in change in serum phosphorus over the 4 weeks (-0.47 versus -0.23 mmol/L, P = .010) when compared with conventional therapy. No significant changes were observed in serum calcium and PTH levels, the proportion of patients achieving target serum calcium or PTH levels, or the adjusted mean difference of serum calcium and PTH levels over the treatment period.

CONCLUSION

Phosphorus balance calculator was proved to improve serum phosphorus control in patients undergoing maintenance hemodialysis, offering a new tool for managing hyperphosphatemia.

Postdialysis serum phosphate equilibrium in hemodialysis patients on a controlled diet and no binders

BACKGROUND

Studies evaluating the change in serum phosphate post hemodialysis (HD) demonstrate an initial decline during dialysis but a rebound post dialysis. However, previous studies were done on usual diet and phosphate binders, with limited number of blood draws, confounding conclusions. We determined serum phosphate reduction, rebound, and equilibrium over 48 h in HD patients consuming a controlled, low phosphorus diet without binders.

METHODS

Serum phosphate (mg/dL) was analyzed before and after a HD treatment and frequently during the ensuing 48 h intradialytic period in the clinical research unit. Thirteen subjects were enrolled and had been off phosphate binders for 10 days and consumed a standardized low phosphate (900 mg/day) diet for 3 weeks prior to the assessments. Linear regression was used to determine relationships between the pre-HD serum phosphate, decline post-HD (post-HD drop); and a 48 h area under curve (AUC) using the trapezoidal method as a measure of overall phosphate levels from the end of dialysis to 48 h post dialysis. Repeated Measures ANOVA with Dunnett's posthoc test was used to determine rebound.

RESULTS

Five of 13 subjects returned to >90% of their pre-HD serum phosphate within the first 24 h post-HD, and serum phosphate was 94 ± 0.11% (range 63%-113%) by 48 h after the completion of HD. The 48 h AUC of serum phosphate during the interdialytic period was correlated with both pre dialysis phosphorus (r = 0.85; p = 0.0002) and the pre-post drop in serum phosphate during dialysis (r = 0.69; p = 0.0085). In contrast, the net ultrafiltration was not related to the 48 h AUC of serum phosphorus (r = 0.20; p = 0.51).

CONCLUSIONS

In hemodialysis patients on standard low phosphorus diet and no phosphate binders, the interdialytic serum phosphorus level, assessed as AUC, is determined by the pre dialysis phosphorus and net-change in serum phosphorus during the dialysis treatment, but not the ultrafiltration volume [Correction added on 25 January, after first online publication: In the last sentence of the Abstract, the word "potassium" has been replaced with "phosphorus" to improve accuracy.].

Phosphorus nutritional knowledge among dialysis health care providers and patients: A multicenter observational study

BACKGROUND-AIMS

Phosphorus nutritional knowledge level of hemodialysis patients and renal nurses has been found to be low, while respective knowledge of nephrologists has not been studied yet. There are equivocal results regarding the association of phosphorus nutritional knowledge level and serum phosphorus values. The aim of this study was to assess phosphorus nutritional knowledge of hemodialysis patients, nephrologists and renal nurses and seek potential interventions to improve patients' adherence to phosphorus and overall nutritional guidelines.

METHODS

This cross-sectional observational study was conducted on sixty eight hemodialysis patients, 19 renal nurses and 11 nephrologists who were recruited from 3 hemodialysis units in Greece. Phosphorus nutritional knowledge of the participants was assessed by a 25-item item questionnaire (CKDKAT-N) which included 15 questions on phosphorus and 10 questions on protein, sodium, and potassium knowledge.

RESULTS

Nephrologists had higher CKDKAT-N total (19.1 ± 3.6 vs 14.1 ± 2.8 and 13.2 ± 2.8, P < 0.01) and phosphorus knowledge scores (10.6 ± 2.7 vs 7.6 ± 2.2 and 7.3 ± 2.0, P < 0.01) compared to renal nurses and patients respectively. There were no differences in total and phosphorus knowledge scores between nurses and patients. Patients and nurses answered correctly significantly less questions regarding phosphorus compared with the rest of the questions (P < 0.01) while no such difference was found in nephrologists. Serum phosphorus was positively correlated with phosphorus knowledge score (r = 0.31, P = 0.02), and negatively correlated with patient age (r = -0.34, P < 0.05). None of the patients, 11% of the nurses and 27% of the nephrologists answered correctly all three questions regarding P, K and Na dietary recommendations (P < 0.01).

CONCLUSIONS

The study confirms that hemodialysis patients have low renal nutrition knowledge while higher nutritional phosphorus knowledge does not lead to lower serum phosphorus values. Alarmingly, renal nurses have been found to have a similar level of knowledge with hemodialysis patients, something that needs to be taken into account when training the new dialysis staff. Nephrologists have superior knowledge; however they are still lacking essential nutritional knowledge that could affect patients' and nurses' overall understanding. Continuing education on nutrition of nephrologists and renal nurses could improve nutrition care of hemodialysis patients.

Prevention of hypophosphatemia during continuous renal replacement therapy-An overlooked problem

Hypophosphatemia is a common and potentially serious complication occurring during continuous renal replacement therapy (CRRT). Phosphate supplementation is required in the vast majority of patients undergoing CRRT, particularly beyond the first 48 hours. Supplementation can be provided either as a standalone oral or parenteral treatment or as an additive to CRRT solutions. Each approach has advantages and disadvantages, and clinicians must weigh the individual factors most relevant in their practice setting. Currently there are no consensus protocols for phosphate replacement in CRRT, and many centers replete phosphate in response to hypophosphatemia as opposed to pre-emptively. Repletion protocols have also been challenged in recent years by shortages in injectable phosphate solutions. More recently a commercially available phosphate-containing CRRT solution was approved in the United States, but there has been limited clinical experience with this product. In this review, we present recommendations for phosphate repletion in CRRT to prevent hypophosphatemia, and describe our experience using phosphate-containing CRRT solutions.

Effects of systematic nursing instruction on a low-phosphorus diet, serum phosphorus level and pruritus of patients on haemodialysis

AIMS AND OBJECTIVES

To investigate the effectiveness of systematic nursing instruction on a low-phosphorus diet, serum phosphorus level and pruritus of haemodialysis patients.

BACKGROUND

A high number of end-stage renal disease patients on haemodialysis are bothered by pruritus. Hyperphosphataemia was reported to be related to pruritus.

DESIGN

An experimental design was applied.

METHODS

Ninety-four patients who received haemodialysis between September 2013 and December 2013 at a medical centre in Taipei, Taiwan, were recruited. An experimental group received individual systematic nursing instruction by the investigator through a nursing instruction pamphlet and reminder card for taking medication. A control group received traditional nursing instruction. The pruritus, blood phosphorus level and five-day diet records were evaluated before and after intervention.

RESULTS

The experimental group had a low-phosphorus diet intake compared with the control group (p < 0·001). A significant difference in serum phosphorus level was observed between the experimental and control groups (p = 0·002). Incidence of pruritus was lower in the experimental group than in the control group (p < 0·001).

CONCLUSION

A systematic nursing instruction included using a pamphlet, pictures and reminder cards, the patients' blood phosphorus levels decreased, the patients consumed more low-phosphorus food, and pruritus decreased.

RELEVANCE TO CLINICAL PRACTICE

This study recommends that clinical nursing staff include systematic nursing instruction as a routine practice for dialysis patients.

Comparative Effectiveness of Phosphate Binders in Patients with Chronic Kidney Disease: A Systematic Review and Network Meta-Analysis

BACKGROUND

Chronic kidney disease-mineral and bone disorder (CKD-MBD) has been linked to poor health outcomes, including diminished quality and length of life. This condition is characterized by high phosphate levels and requires phosphate-lowering agents-phosphate binders. The objective of this systematic review is to compare the effects of available phosphate binders on patient-important outcomes in patients with CKD-MBD.

METHODS

Data sources included MEDLINE and EMBASE Trials from 1996 to February 2016. We also searched the Cochrane Register of Controlled Trials up to April 2016. Teams of two reviewers, independently and in duplicate, screened titles and abstracts and potentially eligible full text reports to determine eligibility, and subsequently abstracted data and assessed risk of bias in eligible randomized controlled trials (RCTs). Eligible trials enrolled patients with CKD-MBD, randomized them to receive calcium (delivered as calcium acetate, calcium citrate or calcium carbonate), non-calcium-based phosphate binders (NCBPB) (sevelamer hydrochloride, sevelamer carbonate, lanthanum carbonate, sucroferric oxyhydroxide and ferric citrate), phosphorus restricted diet, placebo or no treatment, and reported effects on all-cause mortality, cardiovascular mortality or hospitalization at ≥4 weeks follow-up. We performed network meta-analyses (NMA) for all cause-mortality for individual agents (seven-node analysis) and conventional meta-analysis of calcium vs. NCBPBs for all-cause mortality, cardiovascular mortality and hospitalization. In the NMAs, we calculated the effect estimates for direct, indirect and network meta-analysis estimates; for both NMA and conventional meta-analysis, we pooled treatment effects as risk ratios (RR) and calculated 95% confidence intervals (CIs) using random effect models. We used the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach to rate the quality of evidence for each paired comparison.

RESULTS

Our search yielded 1190 citations, of which 71 RCTs were retrieved for full review and 15 proved eligible. With 13 eligible studies from a prior review, we included 28 studies with 8335 participants; 25 trials provided data for our quantitative synthesis. Results suggest higher mortality with calcium than either sevelamer (NMA RR, 1.89 [95% CI, 1.02 to 3.50], moderate quality evidence) or NCBPBs (conventional meta-analysis RR, 1.76 [95% CI, 1.21 to 2.56, moderate quality evidence). Conventional meta-analysis suggested no difference in cardiovascular mortality between calcium and NCBPBs (RR, 2.54 [95% CI, 0.67 to 9.62 low quality evidence). Our results suggest higher hospitalization, although non-significant, with calcium than NCBPBs (RR, 1.293 [95% CI, 0.94 to 1.74, moderate quality evidence).

DISCUSSION/CONCLUSIONS

Use of calcium results in higher mortality than either sevelamer in particular and NCBPBs in general (moderate quality evidence). Our results raise questions about whether administration of calcium as an intervention for CKD- MBD remains ethical. Further research is needed to explore the effects of different types of phosphate binders, including novel agents such as iron, on quality and quantity of life.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD-42016032945.

Effectiveness of a nurse-led intensive educational programme on chronic kidney failure patients with hyperphosphataemia: randomised controlled trial

AIMS AND OBJECTIVES

To prospectively evaluate the effects of a nurse-led educational intervention on the management of hyperphosphataemia as well as knowledge of phosphate among patients with end-stage renal disease.

BACKGROUND

Haemodialysis and phosphate binder therapy are the major methods used to reduce the phosphate level in dialysis patients. However, patient education related to hyperphosphataemia, diet and phosphate binders may be another important factor associated with the success of the control of the hyperphosphataemia.

DESIGN

This prospective randomised controlled trial was conducted during the period from June 2009-March 2011 at the HD units of two hospitals in Tianjin, China.

METHODS

A total of 80 participants were randomly assigned to experimental group (n=40) and control group (n=40). Participants in the experimental group received the nurse-led intensive educational programme, including individualised education and educational session about diet and medicine regimes, etc., while participants in the control group received the routine guidance.

RESULTS

There were statistically significant differences between the study groups in decline in serum phosphorus and calcium-phosphorus product levels and improvement in patients' general knowledge three months postintervention, and these differences sustained until the end of the study. Increased serum calcium level was observed both in the experimental group and in the control group, but there was no significant difference between groups. No statistical significance was found regarding serum albumin level between the groups. No significant difference in the serum parathyroid hormone level was found between the groups by month 6.

CONCLUSIONS

Nurse-led intensive educational programme plays an important role in the control of hyperphosphataemia among patients with end-stage renal disease.

RELEVANCE TO CLINICAL PRACTICE

Chronic kidney failure patients with hyperphosphataemia are more likely to benefit from nurse-led intensive educational programmes.

Phosphate control in end-stage renal disease: barriers and opportunities

Hyperphosphatemia is a nearly universal complication of end-stage renal disease that is widely recognized as one of the most important and most challenging clinical targets to meet in the care of dialysis patients. Left untreated, it can lead to bone pain, pruritus and worsening secondary hyperparathyroidism. Data from observational studies demonstrate that an elevated serum phosphorus level is an independent risk factor for mortality, and that treatment with phosphate binders is independently associated with improved survival. Experimental studies provide support for the epidemiologic findings: phosphate excess promotes vascular calcification, induces endothelial dysfunction and may contribute to other emerging chronic kidney disease-specific mechanisms of cardiovascular toxicity. On the basis of this evidence, clinical practice guidelines recommend specific targets for serum phosphorus levels in the dialysis population. The purpose of this review is to summarize common challenges in meeting these targets and to identify potential opportunities for improvement.

The adequacy of phosphorus binder prescriptions among American hemodialysis patients

Because hemodialysis treatment has a limited ability to remove phosphorus, dialysis patients must restrict dietary phosphorus intake and use phosphorus binding medication. Among patients with restricted dietary phosphorus intake (1000 mg/d), phosphorus binders must bind about 250 mg of excess phosphorus per day and among patients with more typical phosphorus intake (1500 mg/d), binders must bind about 750 mg/d. To determine the phosphorus binding capacity of binder prescriptions among American hemodialysis patients, we undertook a cross-sectional study of a random sample of in-center chronic hemodialysis patients. We obtained data for one randomly selected patient from 244 facilities nationwide. About one-third of the patients had hyperphosphatemia (serum phosphorus level > 5.5 mg/dL). Among the 224 patients prescribed binders, the mean phosphorus binding capacity was 256 mg/d [standard deviation (SD) 143]. A total of 59% of prescriptions had insufficient binding capacity for restricted dietary phosphorus intake, and 100% had insufficient binding capacity for typical dietary phosphorus intake. Patients using two binders had a higher binding capacity than patients using one binder (451 vs. 236 mg/d, p < 0.001). A majority of binder prescriptions have insufficient binding capacity to maintain phosphorus balance. Use of two binders results in higher binder capacity. Further work is needed to understand the impact of binder prescriptions on mineral balance and metabolism and to determine the value of substantially increasing binder prescriptions.

Phosphate mass removal during hemodialysis: a comparison between eKT/V-matched conventional and extended dialysis

BACKGROUND AND OBJECTIVES

The control of hyperphosphatemia is an unmet need in dialysis care. Compared to conventional hemodialysis (cHD), extended hemodialysis (eHD) appears to more easily control blood phosphate levels in chronically dialyzed patients. Here, we sought to compare eKT/V-matched cHD and eHD procedures in order to quantify the contribution of dialysis prescription and time in the mass removal of phosphate.

METHODS

Eight stable hemodialysis patients with negligible residual renal function underwent cHD and eHD sessions adjusted to provide the same eKT/V(urea). Total dialysate, total and hourly partial dialysate and blood samples were collected for comparison of mass extraction of urea, creatinine, and phosphate.

RESULTS

Mean eKT/V(urea) was similar in eHD and cHD (1.30 vs. 1.28, p = nonsignificant). Likewise, mass removal of urea and creatinine during cHD and eHD were not significantly different. Conversely, phosphate mass removal was 40% higher with eHD as compared to cHD (1,219 ± 262 vs. 858 ± 186 mg, p = 0.015). Although hourly mass removal of phosphate was higher during cHD, the prolonged period of lesser but continuous removal was responsible for higher total phosphate elimination during eHD.

CONCLUSION

In dialysis sessions matched to provide a similar eKT/V(urea), removal of phosphate increases by 40% when time is extended from 4 to 8 h. Urea-based adequacy models cannot be used to predict the amount of phosphorus removal during hemodialysis.

Dietary potassium intake and mortality in long-term hemodialysis patients

BACKGROUND

Hyperkalemia has been associated with higher mortality in long-term hemodialysis (HD) patients. There are few data concerning the relationship between dietary potassium intake and outcome.

STUDY DESIGN

The mortality predictability of dietary potassium intake from reported food items estimated using the Block Food Frequency Questionnaire (FFQ) at the start of the cohort was examined in a 5-year (2001-2006) cohort of 224 HD patients in Southern California using Cox proportional hazards regression.

SETTING & PARTICIPANTS

224 long-term HD patients from 8 DaVita dialysis clinics.

PREDICTORS

Dietary potassium intake ranking using the Block FFQ.

OUTCOMES

5-year survival.

RESULTS

HD patients with higher potassium intake had greater dietary energy, protein, and phosphorus intakes and higher predialysis serum potassium and phosphorus levels. Greater dietary potassium intake was associated with significantly increased death HRs in unadjusted models and after incremental adjustments for case-mix, nutritional factors (including 3-month averaged predialysis serum creatinine, potassium, and phosphorus levels; body mass index; normalized protein nitrogen appearance; and energy, protein, and phosphorus intake) and inflammatory marker levels. HRs for death across the 3 higher quartiles of dietary potassium intake in the fully adjusted model (compared with the lowest quartile) were 1.4 (95% CI, 0.6-3.0), 2.2 (95% CI, 0.9-5.4), and 2.4 (95% CI, 1.1-7.5), respectively (P for trend = 0.03). Restricted cubic spline analyses confirmed the incremental mortality predictability of higher potassium intake.

LIMITATIONS

FFQs may underestimate individual potassium intake and should be used to rank dietary intake across the population.

CONCLUSIONS

Higher dietary potassium intake is associated with increased death risk in long-term HD patients, even after adjustments for serum potassium level; dietary protein; energy, and phosphorus intake; and nutritional and inflammatory marker levels. The potential role of dietary potassium in the high mortality rate of HD patients warrants clinical trials.

Association of dietary phosphorus intake and phosphorus to protein ratio with mortality in hemodialysis patients

BACKGROUND AND OBJECTIVES

Epidemiologic studies show an association between higher predialysis serum phosphorus and increased death risk in maintenance hemodialysis (MHD) patients. The hypothesis that higher dietary phosphorus intake and higher phosphorus content per gram of dietary protein intake are each associated with increased mortality in MHD patients was examined.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Food frequency questionnaires were used to conduct a cohort study to examine the survival predictability of dietary phosphorus and the ratio of phosphorus to protein intake. At the start of the cohort, Cox proportional hazard regression was used in 224 MHD patients, who were followed for up to 5 years (2001 to 2006).

RESULTS

Both higher dietary phosphorus intake and a higher dietary phosphorus to protein ratio were associated with significantly increased death hazard ratios (HR) in the unadjusted models and after incremental adjustments for case-mix, diet, serum phosphorus, malnutrition-inflammation complex syndrome, and inflammatory markers. The HR of the highest (compared with lowest) dietary phosphorus intake tertile in the fully adjusted model was 2.37. Across categories of dietary phosphorus to protein ratios of <12, 12 to <14, 14 to <16, and > or =16 mg/g, death HRs were 1.13, 1.00 (reference value), 1.80, and 1.99, respectively. Cubic spline models of the survival analyses showed similar incremental associations.

CONCLUSIONS

Higher dietary phosphorus intake and higher dietary phosphorus to protein ratios are each associated with increased death risk in MHD patients, even after adjustments for serum phosphorus, phosphate binders and their types, and dietary protein, energy, and potassium intakes.

Phosphorus and potassium content of enhanced meat and poultry products: implications for patients who receive dialysis

BACKGROUND AND OBJECTIVES

Uncooked meat and poultry products are commonly enhanced by food processors using phosphate salts. The addition of potassium and phosphorus to these foods has been recognized but not quantified.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We measured the phosphorus, potassium, and protein content of 36 uncooked meat and poultry products: Phosphorus using the Association of Analytical Communities (AOAC) official method 984.27, potassium using AOAC official method 985.01, and protein using AOAC official method 990.03.

RESULTS

Products that reported the use of additives had an average phosphate-protein ratio 28% higher than additive free products; the content ranged up to almost 100% higher. Potassium content in foods with additives varied widely; additive free products all contained <387 mg/100 g, whereas five of the 25 products with additives contained at least 692 mg/100 g (maximum 930 mg/100 g). Most but not all foods with phosphate and potassium additives reported the additives (unquantified) on the labeling; eight of 25 enhanced products did not list the additives. The results cannot be applied to other products. The composition of the food additives used by food processors may change over time.

CONCLUSIONS

Uncooked meat and poultry products that are enhanced may contain additives that increase phosphorus and potassium content by as much as almost two- and three-fold, respectively; this modification may not be discernible from inspection of the food label.