Preserving residual renal function in dialysis: what we know

The impact of low-protein diet on residual renal function in dialysis patients: a systematic review and metaanalysis

OBJECTIVE

A low-protein diet is essential for the nutritional management of chronic kidney diseases as it can reduce renal burden. However, the effect of low-protein diets on dialysis patients compared to pre-dialysis patients remains unclear. This study aims to compare residual renal function among dialysis patients following a low-protein diet versus a normal diet, offering valuable insights into the optimal nutritional strategy for preserving residual renal function.

METHODS

This meta-analysis has been registered on PROSPERO, an international registry of prospective systematic reviews. We conducted a comprehensive and systematic literature search using PubMed, Cochrane Library and Web of Science (WOS). Our search strategy was designed to discover all relevant studies investigating the influence of low-protein diets on residual renal function among dialysis patients. Four studies met the inclusion criteria. Heterogeneity was discussed through subgroup analysis of dialysis method, the addition of ketoacid and other relevant factors.

RESULTS

We included four prospective studies of low-protein diets among dialysis patients, each of which included at least 40 participants. Individuals receiving a 12-months low-protein diet had a higher GFR (MD = 1.37 ml/min; 95% CI:0.18 to 2.55), while daily urine volume decreasing more slowly (MD = 660 ml; 95% CI: 110 to 1210). In addition, dialysis patients undergoing a low-protein diet for 4 or 12 months had reduced serum phosphorus (MD=-0.74 g/dl; 95% CI: -1.04 to -0.45). Their serum albumin was higher than dialysis patients received a free-choice diet (MD = 4.00 g/dl; 95% CI: 2.46 to 5.54).

CONCLUSION

Dialysis patients who adhere to a long-term low-protein diet may have a positive effect on residual kidney function. In addition, dialysis patients receiving a low-protein diet increased serum albumin, reduced serum phosphorus levels, and maintained a better nutritional status and electrolyte balance.

Staying home when peritoneal dialysis ends: the integrated home dialysis approach

PURPOSE OF REVIEW

Home dialysis has been promoted for several years for patients starting dialysis. Although incident use of peritoneal dialysis (PD) and home hemodialysis (HHD) is increasing in several regions, patients on home dialysis remain at high risk of transfer to facility-hemodialysis (HD). The integrated home dialysis model, where patient start dialysis on PD and eventually transition to HHD when PD cannot be optimally continued has gain interest from dialysis stakeholders.

RECENT FINDINGS

Transfers from PD to HHD are infrequently used among patients ending PD, representing between 2% and 6% of transfers to HD in registry studies. Nonetheless, this approach is associated with several clinical benefits as well as favorable cost-effectiveness.

SUMMARY

In this review, we will present data pertaining to home dialysis and the integrated home dialysis model, with broad discussion of the implementation challenges, including identifying patients who could most benefit from this approach, timely planning of the transitions and challenges relating to unexpected PD endings.

Integrated home dialysis model: facilitating home-to-home transition

Peritoneal dialysis (PD) and home hemodialysis (HHD) are the two home dialysis modalities offered to patients. They promote patient autonomy, enhance independence, and are generally associated with better quality of life compared to facility hemodialysis. PD offers some advantages (enhanced flexibility, ability to travel, preservation of residual kidney function, and vascular access sites) but few patients remain on PD indefinitely due to peritonitis and other complications. By contrast, HHD incurs longer and more intensive training combined with increased upfront health costs compared to PD, but is easier to sustain in the long term. As a result, the integrated home dialysis model was proposed to combine the advantages of both home-based dialysis modalities. In this paradigm, patients are encouraged to initiate dialysis on PD and transfer to HHD after PD termination. Available evidence demonstrates the feasibility and safety of this approach and some observational studies have shown that patients who undergo the PD-to-HHD transition have clinical outcomes comparable to patients who initiate dialysis directly on HHD. Nevertheless, the prevalence of PD-to-HHD transfers remains low, reflecting the multiple barriers that prevent the full uptake of home-to-home transitions, notably a lack of awareness about the model, home-care "burnout," clinical inertia after a transfer to facility HD, suboptimal integration of PD and HHD centers, and insufficient funding for home dialysis programs. In this review, we will examine the conceptual advantages and disadvantages of integrated home dialysis, present the evidence that underlies it, identify challenges that prevent its success and finally, propose solutions to increase its adoption.

Fluid management protocols in hemodialysis patients using bioimpedance validation: time to look elsewhere?

The management of volume status in dialysis patients is an important determinant of the rate of decline of residual kidney function. The implementation of clinical protocols to guide volume management in the in-center hemodialysis unit resulted in comparable rates of development of anuria and decline in residual kidney function when compared with bioimpedance spectroscopy-guided volume management. Clinical judgment and experience are important drivers of patient outcomes. The importance and applicability of bioimpedance spectroscopy in other clinical settings, such as units without clear volume management protocols or in home dialysis units, remain to be seen.

Role of the Microbiome in Gut-Heart-Kidney Cross Talk

Homeostasis is a prerequisite for health. When homeostasis becomes disrupted, dysfunction occurs. This is especially the case for the gut microbiota, which under normal conditions lives in symbiosis with the host. As there are as many microbial cells in and on our body as human cells, it is unlikely they would not contribute to health or disease. The gut bacterial metabolism generates numerous beneficial metabolites but also uremic toxins and their precursors, which are transported into the circulation. Barrier function in the intestine, the heart, and the kidneys regulates metabolite transport and concentration and plays a role in inter-organ and inter-organism communication via small molecules. This communication is analyzed from the perspective of the remote sensing and signaling theory, which emphasizes the role of a large network of multispecific, oligospecific, and monospecific transporters and enzymes in regulating small-molecule homeostasis. The theory provides a systems biology framework for understanding organ cross talk and microbe-host communication involving metabolites, signaling molecules, nutrients, antioxidants, and uremic toxins. This remote small-molecule communication is critical for maintenance of homeostasis along the gut-heart-kidney axis and for responding to homeostatic perturbations. Chronic kidney disease is characterized by gut dysbiosis and accumulation of toxic metabolites. This slowly impacts the body, affecting the cardiovascular system and contributing to the progression of kidney dysfunction, which in its turn influences the gut microbiota. Preserving gut homeostasis and barrier functions or restoring gut dysbiosis and dysfunction could be a minimally invasive way to improve patient outcomes and quality of life in many diseases, including cardiovascular and kidney disease.

On the importance of the interplay of residual renal function with clinical outcomes in end-stage kidney disease

Chronic kidney disease (CKD) is one of the most important public health concerns of the century, and is associated with high rates of morbidity, mortality and social costs. CKD evolving towards end-stage kidney disease (ESKD) is on the rise resulting in a greater number of patients requiring peritoneal dialysis (PD) and hemodialysis (HD). The aim of this manuscript is to review the current literature on the interplay of residual renal function (RRF) with clinical outcomes in ESKD. The persistence of RRF is one of the most important predictors of decreased morbidity, mortality, and better quality of life in both PD and HD patients. RRF contributes to the well-being of ESKD patients through various mechanisms including higher clearance of solutes, maintenance of fluid balance, removal of uremic toxins and control of electrolytes. Furthermore, RRF has beneficial effects on inflammation, anemia, malnutrition, diabetes mellitus, obesity, changes in the microbiota, and cardiac diseases. Several strategies have been proposed to preserve RRF, such as blockade of the renin-angiotensin-aldosterone system, better blood pressure control, incremental PD and HD. Several clinical trials investigating the issue of preservation of RRF are ongoing. They are needed to broaden our understanding of the interplay of RRF with clinical outcomes in ESKD.

Efficacy of Roxadustat on anemia and residual renal function in patients new to peritoneal dialysis

Background

Both early correction of anemia and preserving residual renal function (RRF) are reported to improve patient survival. The aim of this study was to explore the efficacy and safety of Roxadustat for treatment of renal anemia in patients new to peritoneal dialysis (PD) and to assess its impact on RRF.

Methods

A retrospective analysis was performed on 60 initial peritoneal dialysis (PD) patients with renal anemia. Twenty-eight cases were treated with Roxadustat (Roxadustat group) and 32 with recombinant human erythropoietin (control group). Clinical characteristics, hemoglobin (Hb), C-reactive protein, blood lipids, iron metabolism, dialysis adequacy and RRF of the two groups were evaluated and adverse events were recorded. All patients were followed up for at least 40 weeks.

Results

After 40 weeks of treatment, mean Hb levels were significantly higher from baseline values in both groups, the mean Hb change in Roxadustat group was higher than control group (3.46 ± 1.59 g/dL vs. 2.28 ± 2.27 g/dL, p < 0.05). At 40 weeks, 92.9% patients met the target level of Hb in Roxadustat group and 84.4% in control group. Total iron binding was higher and ferritin was lower in Roxadustat group from baseline values and Roxadustat-induced Hb increases were independent of baseline C-reactive protein levels and history of rhuEPO administration. RRF decreased over time in both groups, the mean RRF change was lower in Roxadustat group than control group (1.15 ± 1.66 mL/min/1.73 m² vs. 2.31 ± 1.46 mL/min/1.73 m², p < 0.01). Compared with control group, patients in Roxadustat group had higher levels of total iron binding, 24 h urine volume, total weekly Ccr, and lower systolic pressure, ferritin, C-reactive protein, total cholesterol, LDL. No serious adverse reactions occurred in either group.

Conclusion

In patients new to PD, Roxadustat effectively and safely improved renal anemia and delay the decline of RRF.

Residual Renal Function - How Fast Does the Residual Urine Output Function Decline in the First Year of Haemodialysis? - A Scoping Review

Background

Haemodialysis is the most common treatment method in Australia for individuals requiring renal replacement therapy. Although it is known that the residual renal function in these patients has many advantages for their overall health outcomes and that the residual urine volume production is also declining over time, it is unknown how fast this functional decline occurs when patients are embarking on their first year on haemodialysis.

Aim

This scoping review sought to determine if the functional decline in renal residual function in the first year of haemodialysis has been previously investigated, documented or quantified.

Method

The scoping review was performed using variety of nursing and medical databases comprising MEDLINE, Embase, Web of Science and CINAHL Plus with Full Text.

Results

The decline of renal residual function in patients on Peritoneal dialysis over the first year of treatment has previously been described, but not in detail for patients receiving haemodialysis. There is a paucity of knowledge how fast residual urine production can decline in patients receiving haemodialysis during their first year of treatment. A PRISMA checklist has been used to validate the results of this scoping review.

Conclusions

The extended preservation of renal residual function in patients on haemodialysis is crucial for their survival and may have a positive impact on their quality of life. An observational study is needed to examine how fast the functional decrease of the residual urine production function within patients receiving haemodialysis generally occurs. This information could prove to be useful in the context of treatment goals and could inform clinical practice.

IHDIP: a controlled randomized trial to assess the security and effectiveness of the incremental hemodialysis in incident patients

BACKGROUND

Most people who make the transition to renal replacement therapy (RRT) are treated with a fixed dose thrice-weekly hemodialysis réegimen, without considering their residual kidney function (RKF). Recent papers inform us that incremental hemodialysis is associated with preservation of RKF, whenever compared with conventional hemodialysis. The objective of the present controlled randomized trial (RCT) is to determine if start HD with one sessions per week (1-Wk/HD), it is associated with better patient survival and other safety parameters.

METHODS/DESIGN

IHDIP is a multicenter RCT experimental open trial. It is randomized in a 1:1 ratio and controlled through usual clinical practice, with a low intervention level and non-commercial. It includes 152 incident patients older than 18 years, with a RRF of ≥4 ml/min/1.73 m2, measured by renal clearance of urea (KrU). The intervention group includes 76 patients who will start with incremental HD (1-Wk/HD). The control group includes 76 patients who will start with thrice-weekly hemodialysis régimen. The primary outcome is assessing the survival rate, while the secondary outcomes are the morbidity rate, the clinical parameters, the quality of life and the efficiency.

DISCUSSION

This study will enable to know the number of sessions a patient should receive when starting HD, depending on his RRF. The potentially important clinical and financial implications of incremental hemodialysis warrant this RCT.

TRIAL REGISTRATION

U.S. National Institutes of Health, ClinicalTrials.gov . Number: NCT03239808 , completed 13/04/2017.

SPONSOR

Foundation for Training and Research of Health Professionals of Extremadura.

Rationale and design of DiPPI: A randomized controlled trial to evaluate the safety and effectiveness of progressive hemodialysis in incident patients

INTRODUCTION

Progressive haemodialysis (HD) is a starting regime for renal replacement therapy (RRT) adapted to each patient's necessities. It is mainly conditioned by the residual renal function (RRF). The frequency of sessions with which patients start HD (one or two sessions per week), is lower than that for conventional HD (three times per week). Such frequency is increased (from one to two sessions, and from two to three sessions) as the RRF declines.

METHODOLOGY/DESIGN

IHDIP is a multicentre randomised experimental open trial. It is randomised in a 1:1 ratio and controlled through usual clinical practice, with a low intervention level and non-commercial. It includes 152 patients older than 18 years with chronic renal disease stage 5 and start HD as RRT, with an RRF of ≥4ml/min/1.73m², measured by renal clearance of urea (KrU). The intervention group includes 76 patients who will start with one session of HD per week (progressive HD). The control group includes 76 patients who will start with three sessions per week (conventional HD). The primary purpose is assessing the survival rate, while the secondary purposes are the morbidity rate (hospital admissions), the clinical parameters, the quality of life and the efficiency.

DISCUSSION

This study will enable us to know, with the highest level of scientific evidence, the number of sessions a patient should receive when starting the HD treatment, depending on his/her RRF.

TRIAL REGISTRATION

Registered at the U.S. National Institutes of Health, ClinicalTrials.gov under the number NCT03239808.

Feasibility of Incremental 2-Times Weekly Hemodialysis in Incident Patients With Residual Kidney Function

INTRODUCTION

We hypothesized that at least half of incident hemodialysis (HD) patients on 3-times weekly dialysis could safely start on an incremental, 2-times weekly HD schedule if residual kidney function (RKF) had been considered.

METHODS

RKF is assessed in all our HD patients. This single-center, retrospective cohort study of incident adult HD patients, who survived ≥6 months on a 3-times weekly HD regimen and had a timed urine collection within 3 months of starting HD, assessed each patient's theoretical ability to achieve adequate urea clearance, ultrafiltration rate, and hemodynamic stability if on 2-times weekly HD.

RESULTS

Of the 410 patients in the cohort, we found that 112 (27%) could have optimally and 107 (26%) could have been appropriately considered for 2-times weekly incremental HD. In general, diuretics were underutilized in >50% of subjects who had adequate RKF urea clearance. The optimal 2-times weekly patients had better potassium and phosphorus control. The correlation coefficient of calculated residual kidney urea clearance with 24-hour urine volume and with kinetic model residual kidney clearance was 0.68 and 0.99, respectively.

DISCUSSION

More than 50% of incident HD patients with RKF have adequate kidney urea clearance to be considered for 2-times weekly HD. When additionally ultrafiltration volume and blood pressure stability are taken into account, more than one-fourth of the total cohort could optimally start HD in an incremental fashion.

Interplay of volume, blood pressure, organ ischemia, residual renal function, and diet: certainties and uncertainties with dialytic management

Extracellular fluid volume overload and its inevitable consequence, hypertension, increases cardiovascular mortality in the long term by leading to left ventricular hypertrophy, heart failure, and ischemic heart disease in dialysis patients. Unlike antihypertensive medications, a strict volume control strategy provides optimal blood pressure control without need for antihypertensive drugs. However, utilization of this strategy has remained limited because of several factors, including the absence of a gold standard method to assess volume status, difficulties in reducing extracellular fluid volume, and safety concerns associated with reduction of extracellular volume. These include intradialytic hypotension; ischemia of heart, brain, and gut; loss of residual renal function; and vascular access thrombosis. Comprehensibly, physicians are hesitant to follow strict volume control policy because of these safety concerns. Current data, however, suggest that a high ultrafiltration rate rather than the reduction in excess volume is related to these complications. Restriction of dietary salt intake, increased frequency, and/or duration of hemodialysis sessions or addition of temporary extra sessions during the process of gradually reducing postdialysis body weight in conventional hemodialysis and discontinuation of antihypertensive medications may prevent these complications. We believe that even if an unwanted effect occurs while gradually reaching euvolemia, this is likely to be counterbalanced by favorable cardiovascular outcomes such as regression of left ventricular hypertrophy, prevention of heart failure, and, ultimately, cardiovascular mortality as a result of the eventual achievement of normal extracellular fluid volume and blood pressure over the long term.

Angiotensin-converting enzyme inhibitor/angiotensin receptor blocker use and cardiovascular outcomes in patients initiating peritoneal dialysis

Background

Data on the effectiveness of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) in reducing cardiovascular (CV) risk in patients undergoing peritoneal dialysis (PD) are limited. We investigated the association between ACEI/ARB use and CV outcomes in patients initiating PD.

Methods

In this observational cohort study, we identified from the United States Renal Data System all adult patients who initiated PD from 2007 to 2011 and participated in Medicare Part D, a federal prescription drug benefits program, for the first 90 days of dialysis. Patients who filled a prescription for an ACEI or ARB in those 90 days were considered users. We applied Cox regression to an inverse probability of treatment weighted cohort to estimate the hazard ratios (HRs) for the combined outcome of death, ischemic stroke or myocardial infarction (MI) and each outcome individually.

Results

Among 4879 patients, 2063 (42%) used an ACEI/ARB. Patients were followed up for a median of 1.2 years. We recorded 1771 events, for a composite rate of 25 events per 100 person-years. ACEI/ARB use (versus nonuse) was associated with a reduced risk of the composite outcome {HR 0.84 [95% confidence interval (CI) 0.76-0.93]}, all-cause mortality [HR 0.83 (95% CI 0.75-0.92)] and CV death [HR 0.74 (95% CI 0.63-0.87)], but not MI [HR 0.88 (95% CI 0.69-1.12)] or ischemic stroke [HR 1.06 (95% CI 0.79-1.43)]. Results were similar in as-treated analyses. In a subgroup analysis, we did not find any effect modification by residual renal function.

Conclusions

ACEI/ARB use is common in patients initiating PD and is associated with a lower risk of fatal CV outcomes.

Advances in Understanding and Management of Residual Renal Function in Patients with Chronic Kidney Disease

BACKGROUND

Residual renal function (RRF), defined as the ability of native kidneys to eliminate water and uremic toxins, is closely correlated with mortality and morbidity rates among patients receiving either peritoneal dialysis (PD) or hemodialysis (HD) via continuous clearance of middle-sized molecules and protein-bound solutes. Therefore, preserving RRF is considered to be one of the primary goals in managing patients with end-stage renal disease (ESRD).

SUMMARY AND KEY MESSAGES

In this article, we provide a review on the understanding and management of RRF in patients on dialysis. RRF may be estimated and measured by calculating the mean 24-hour urine creatinine level and urea clearance. Currently, several middle-sized molecules are reported but rarely used in practice. Many risk factors such as original renal diseases, dietary intake, and nephrotoxic agents impair RRF. Targeting such factors may halt the decline in RRF and offer better outcomes for patients on PD or HD. Except for in PD patients, RRF is a powerful predictor of survival in HD patients. RRF requires more clinical and research attention in the care of patients with ESRD on dialysis.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers for preserving residual kidney function in peritoneal dialysis patients

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) are widely used in peritoneal dialysis (PD) patients, yet controversy exists about their impact on residual kidney function.

OBJECTIVES

This review aimed to evaluate the benefits and harms of ACEis and ARBs for preserving residual kidney function in PD patients.

SEARCH METHODS

The Cochrane Renal Group's specialised register, Cochrane Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE (OvidSP interface), Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI) and other resources were searched by applying a prespecified comprehensive search strategy. Date of last search: 01 May 2014.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing ACEis or ARBs with placebo, other antihypertensive drugs or each other in PD patients were included.

DATA COLLECTION AND ANALYSIS

Screening, selection, data extraction and quality assessments for each retrieved article were carried out by two authors using standardised forms. Authors were contacted when published data were incomplete. Statistical analyses were performed using the random effects model and results expressed as risk ratio (RR) with 95% confidence intervals (CI). Heterogeneity among studies was explored using the Cochran Q statistic and the I² test, subgroup analyses and random effects meta-regression.

MAIN RESULTS

Six open-label studies (257 patients) were identified. One study compared ACEi with other antihypertensive drugs, three compared ARBs with other antihypertensive drugs, and two studies compared an ARB with an ACEi. Long-term use (≥ 12 months) of an ARB showed significantly benefit of preserving residual kidney function in continuous ambulatory PD (CAPD) patients (MD 1.11 mL/min/1.73 m², 95% CI 0.38 to 1.83), although there was no significant benefit when an ARB were used short-term (≤ six months). One study showed that compared with other antihypertensive drugs, long-term use (12 months) of the ACEi ramipril showed a significant reduction in the decline of residual kidney function in patients on CAPD (MD -0.93 mL/min/1.73m², 95% CI -0.75 to -0.11), and delayed the progression to complete anuria (RR 0.64, 95% CI 0.41 to 0.99). There was no significant difference in serum potassium, urinary protein excretion, Kt/V, weekly creatinine clearance and blood pressure for ARBs versus other antihypertensive drugs. Compared with other antihypertensive drugs, ramipril showed no difference in mortality and cardiovascular events. Compared with an ACEi, ARBs did not show any difference in residual kidney function.The selection bias assessment was low in four studies and unclear in two. Five studies were open-label; however the primary outcome (residual kidney function) was obtained objectively from laboratory tests, and were not likely to be influenced by the lack of blinding. Reporting bias was unclear in all six studies.

AUTHORS' CONCLUSIONS

Compared with other antihypertensive drugs, long-term use (≥ 12 months) of ACEis or ARBs showed additional benefits of preserving residual kidney function in CAPD patients. There was no significant difference on residual kidney function preservation between ARBs and ACEis. However, limited by the small number of RCTs enrolling small number of participants, there is currently insufficient evidence to support the use of an ACEi or an ARB as first line antihypertensive therapy in PD patients.