Standard Kt/Vurea: a method of calculation that includes effects of fluid removal and residual kidney clearance

The impact of dialysate flow rate on haemodialysis adequacy: a systematic review and meta-analysis

Background

Patients with kidney failure treated with maintenance haemodialysis (HD) require appropriate small molecule clearance. Historically, a component of measuring 'dialysis adequacy' has been quantified using urea kinetic modelling that is dependent on the HD prescription. However, the impact of dialysate flow rate on urea clearance remains poorly described in vivo and its influence on other patient-important outcomes of adequacy is uncertain.

Methods

We searched Embase, MEDLINE and the Cochrane Library from inception until April 2022 for randomized controlled trials and observational trials comparing a higher dialysate flow rate (800 ml/min) and lower dialysate flow rate (300 ml/min) with a standard dialysis flow rate (500 ml/min) in adults (age ≥18 years) treated with maintenance HD (>90 consecutive days). We conducted a random effects meta-analysis to estimate the pooled mean difference in dialysis adequacy as measured by Kt/V or urea reduction ratio (URR).

Results

A total of 3118 studies were identified. Of those, nine met eligibility criteria and four were included in the meta-analysis. A higher dialysate flow rate (800 ml/min) increased single-pool Kt/V by 0.08 [95% confidence interval (CI) 0.05-0.10, P < .00001] and URR by 3.38 (95% CI 1.97-4.78, P < .00001) compared with a dialysate flow rate of 500 ml/min. Clinically relevant outcomes including symptoms, cognition, physical function and mortality were lacking and studies were generally at a moderate risk of bias due to issues with randomization sequence generation, allocation concealment and blinding.

Conclusion

A higher dialysate flow increased urea-based markers of dialysis adequacy. Additional high-quality research is needed to determine the clinical, economic and environmental impacts of higher dialysate flow rates.

Comparative effectiveness of an individualized model of hemodialysis vs conventional hemodialysis: a study protocol for a multicenter randomized controlled trial (the TwoPlus trial)

BACKGROUND

Most patients starting chronic in-center hemodialysis (HD) receive conventional hemodialysis (CHD) with three sessions per week targeting specific biochemical clearance. Observational studies suggest that patients with residual kidney function can safely be treated with incremental prescriptions of HD, starting with less frequent sessions and later adjusting to thrice-weekly HD. This trial aims to show objectively that clinically matched incremental HD (CMIHD) is non-inferior to CHD in eligible patients.

METHODS

An unblinded, parallel-group, randomized controlled trial will be conducted across diverse healthcare systems and dialysis organizations in the USA. Adult patients initiating chronic hemodialysis (HD) at participating centers will be screened. Eligibility criteria include receipt of fewer than 18 treatments of HD and residual kidney function defined as kidney urea clearance ≥3.5 mL/min/1.73 m2 and urine output ≥500 mL/24 h. The 1:1 randomization, stratified by site and dialysis vascular access type, assigns patients to either CMIHD (intervention group) or CHD (control group). The CMIHD group will be treated with twice-weekly HD and adjuvant pharmacologic therapy (i.e., oral loop diuretics, sodium bicarbonate, and potassium binders). The CHD group will receive thrice-weekly HD according to usual care. Throughout the study, patients undergo timed urine collection and fill out questionnaires. CMIHD will progress to thrice-weekly HD based on clinical manifestations or changes in residual kidney function. Caregivers of enrolled patients are invited to complete semi-annual questionnaires. The primary outcome is a composite of patients' all-cause death, hospitalizations, or emergency department visits at 2 years. Secondary outcomes include patient- and caregiver-reported outcomes. We aim to enroll 350 patients, which provides ≥85% power to detect an incidence rate ratio (IRR) of 0.9 between CMIHD and CHD with an IRR non-inferiority of 1.20 (α = 0.025, one-tailed test, 20% dropout rate, average of 2.06 years of HD per patient participant), and 150 caregiver participants (of enrolled patients).

DISCUSSION

Our proposal challenges the status quo of HD care delivery. Our overarching hypothesis posits that CMIHD is non-inferior to CHD. If successful, the results will positively impact one of the highest-burdened patient populations and their caregivers.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05828823. Registered on 25 April 2023.

Twice Weekly versus Thrice Weekly Hemodialysis-A Pilot Cross-Over Equivalence Trial

Key Points

Background

The 2015 Update of the Kidney Disease Outcomes Quality Initiative (KDOQI) Guideline for Hemodialysis Adequacy increased the contribution of residual kidney function in calculating standard Kt/Vurea (stdKt/Vurea). However, no study has assessed the effect of prescribing twice weekly hemodialysis according to this guideline on patients' quality of life or uremic solute levels.

Methods

Twenty six hemodialysis patients with average residual urea clearance (Kru) 4.7±1.8 ml/min and hemodialysis vintage of 12±15 months (range 2 months to 4.9 years) underwent a cross-over trial comparing four weeks of twice weekly hemodialysis and four weeks of thrice weekly hemodialysis. Twice weekly hemodialysis was prescribed to achieve stdKt/Vurea 2.2 incorporating Kru using the 2015 KDOQI Guideline. Thrice weekly hemodialysis was prescribed to achieve spKt/Vurea 1.3 regardless of Kru. Quality of life and plasma levels of secreted uremic solutes and β 2 microglobulin were assessed at the end of each period.

Results

Equivalence testing between twice and thrice weekly hemodialysis based on the Kidney Disease Quality of Life instrument (primary analysis) was inconclusive. Symptoms as assessed by the secondary outcomes Dialysis Symptom Index and Post-Dialysis Recovery Time were not worse with twice weekly hemodialysis. StdKt/Vurea was adequate during twice weekly hemodialysis (2.7±0.5), and ultrafiltration rate and plasma potassium were controlled with minimally longer treatment times (twice weekly: 195±20 versus thrice weekly: 191±17 minutes). Plasma levels of the secreted solutes and β 2 microglobulin were not higher with twice weekly than thrice weekly hemodialysis.

Conclusions

Twice weekly hemodialysis can be prescribed using the higher contribution assigned to Kru by the 2015 KDOQI Guideline. With twice weekly hemodialysis, quality of life was unchanged, and the continuous function of the residual kidneys controlled fluid gain and plasma levels of potassium and uremic solutes without substantially longer treatment times.

Clinical Trial registration number:

NCT03874117.

A practical approach to implementing incremental haemodialysis

The majority of end-stage kidney disease patients are treated with haemodialysis (HD). Starting HD can pose physical, social, and psychological challenges to patients, and mortality rates within the first 6 months are disproportionately high, with intensive HD regimens implicated as a potential factor. Starting HD with an incremental approach, taking residual kidney function (RKF) into account, potentially allows for a gentle start with reduced dialysis intensity. Dialysis intensity (session time or frequency) can then be proportionally increased as RKF reduces. This approach to starting HD has been reported in observational studies to result in better patient self-reported health quality of life and reduced costs, and now several definitive randomised controlled trials are underway comparing an incremental approach to the conventional thrice weekly paradigm. Physician concerns over the risk of inadequate dialysis, with consequent increased emergency admissions, and practical challenges of how to estimate RKF and implement incremental dialysis have impeded widespread adoption. Addressing these challenges is paramount to increasing the uptake of incremental HD. Careful patient selection lies at the heart of a successful incremental HD programme. Generally, patients with a residual urea clearance of > 3 ml/min/1.73 m2 can be considered suitable for starting with incremental HD provided they comply with fluid intake, salt and other dietary recommendations. Calculating RKF from regular interdialytic urine collections and appropriately adjusting sessional HD clearance targets are practical and conceptual challenges. In this report we aim to disentangle these complexities and provide a step-by-step guide for patient selection and adjusting dialysis sessional targets.

Prescribing the dialysis dose and treatment frequency in home haemodialysis

BACKGROUND

There is growing interest in home haemodialysis (HHD) performed with low-flow dialysate devices and variable treatment schedules. The target standard Kt/V (stdKt/V) should be 2.3 volumes/week, according to KDOQI guidelines (2015). The current formula for stdKt/V does not help prescribe the dialysis dose (eKt/V) and treatment frequency (TF). The aim of this study was to obtain a formula for stdKt/V that is able to define the minimum required values of eKt/V and TF to achieve the targeted stdKtV.

METHODS

Thirty-eight prevalent patients on HHD were enrolled. A total of 231 clinical datasets were available for urea modelling using the Solute-Solver software (SS), recommended by KDOQI guidelines. A new formula (stdKt/V = a + b × Kru + c × eKt/V) was obtained from multivariable regression analysis of stdKt/V vs eKt/V and residual kidney urea clearance (Kru). The values of coefficients a, b and c depend on the treatment schedules and the day of the week of blood sampling for the kinetic study (labdayofwk) and then vary for each of their foreseen 62 combinations. For practical purposes, we used only seven combinations, assuming Monday as a labdayofwk for each of the most common schedules of the 7 days of the week.

RESULTS

The stdKt/V values obtained with SS were compared with the paired ones obtained with the formula. The mean ± standard deviation stdKt/V values obtained with SS and the formula were 3.043 ± 0.530 and 2.990 ± 0.553, respectively, with 95% confidence interval +0.15 to -0.26. A 'prescription graph' was built using the formula to draw lines expressing the relationship between Kru and required eKt/V for each TF. Using this graph, TF could have been reduced from the delivered 5.8 ± 0.8 to 4.8 ± 0.8 weekly sessions.

CONCLUSIONS

The new formula for stdKtV is reliable and can support clinicians to prescribe the dialysis dose and TF in patients undergoing HHD.

Low-Volume Home Haemodialysis and In-Centre Haemodialysis: Comparison of Dialysis Adequacy in Obese Individuals

Background Although frequent low-flow, low-volume haemodialysis using the NxStage System One is now well-established as an option for home therapy of end-stage chronic kidney disease, its ability to deliver adequate dialysis in people with high BMI remains questionable. This doubt may lead to obese individuals being denied the potential benefits of this modality. To establish if this doubt is justified, we compared dialysis adequacy in two groups of obese individuals; one receiving standard thrice-weekly in-centre haemodialysis and the other receiving frequent haemodialysis at home using the NxStage System One. Methods This is a retrospective observational cohort study of 105 adult dialysis patients with obesity (BMI ≥ 30 kg/m2). All had been on dialysis for at least six months. Fifty-five patients receiving in-centre haemodialysis were compared with 50 patients receiving home haemodialysis using NxStage System One. Dialysis adequacy (standard Kt/V calculated by the Daugirdas equation) was compared between the two groups. The clinical characteristics, laboratory test results, and treatment regimens of each group were also compared. Results The in-centre haemodialysis group was older (63.6 ± 12.8 years vs. 58.5 ± 10.9 years, p=0.033) and had a higher Charlson comorbidity score (5.9 ± 2.1 vs. 4.5 ± 2.5, p=0.003). Standard Kt/V was significantly higher in the home haemodialysis group (2.4 ± 0.5) than in the in-centre haemodialysis group (2.2 ± 0.2) (p = 0.006). The mean serum inorganic phosphate was significantly lower in the home haemodialysis group than in the in-centre haemodialysis group (1.6 ± 0.4 mmol/l vs. 1.8 ± 0.5 mmol/l, p = 0.010). There were no statistically significant differences in the usage of antihypertensives, phosphate binders, or erythropoiesis-stimulating agents between the two groups. Conclusions In this study, dialysis adequacy (expressed as standard Kt/V) was superior to that of standard thrice-weekly in-center haemodialysis delivered by frequent low-volume home haemodialysis using the NxStage System One. Hesitancy about recommending frequent low-volume home haemodialysis to obese individuals is therefore unjustified.

Recent advancement challenges with synthesis of biocompatible hemodialysis membranes

The focus of this study is to enhance the protein fouling resistance, hydrophilicity, biocompatibility, hemocompatibility and ability of the membranes and to reduce health complications like chronic pulmonary disease, peripheral vascular disease, cerebrovascular disease, and cardiovascular disease after dialysis, which are the great challenges in HD applications. In the current study, the PSF-based dialysis membranes are studied broadly. Significant consideration has also been provided to membrane characteristics (e.g., flowrate coefficient, solute clearance characteristic) and also on commercially available polysulfone HD membranes. PSF has gained a significant share in the development of HD membranes, and continuous improvements are being made in the process to make high flux PSF-based dialysis membranes with enhanced biocompatibility and improved protein resistance ability as the major issue in the development of membranes for HD application is biocompatibility. There has been a great increase in the demand for novel biocompatible membranes that offer the best performances during HD therapy, for example, low oxidative stress and low change ability of blood pressure.

Twice-Weekly Hemodialysis With Adjuvant Pharmacotherapy and Transition to Thrice-Weekly Hemodialysis: A Pilot Study

RATIONALE & OBJECTIVE

Thrice-weekly hemodialysis (HD) is the most common treatment modality for kidney failure in the United States. We conducted a pilot study to assess the feasibility and safety of incremental-start HD in patients beginning maintenance HD.

STUDY DESIGN

Pilot study.

SETTING & PARTICIPANTS

Adults with estimated glomerular filtration rate (eGFR) ≥5 mL/min/1.73 m² and urine volume ≥500 mL/d beginning maintenance HD at 14 outpatient dialysis units.

EXPOSURE

Randomized allocation (1:1 ratio) to twice-weekly HD and adjuvant pharmacologic therapy for 6 weeks followed by thrice-weekly HD (incremental HD group) or thrice-weekly HD (conventional HD group).

OUTCOME

The primary outcome was feasibility. Secondary outcomes included changes in urine volume and solute clearance.

RESULTS

Of 77 patients invited to participate, 51 consented to do so, representing 66% of eligible patients. We randomized 23 patients to the incremental HD group and 25 patients to the conventional HD group. Protocol-based loop diuretics, sodium bicarbonate, and patiromer were prescribed to 100%, 39%, and 17% of patients on twice-weekly HD, respectively. At a mean follow-up of 281.9 days, participant adherence was 96% to the HD schedule (22 of 23 and 24 of 25 in the incremental and conventional groups, respectively) and 100% in both groups to serial timed urine collection. The incidence rate ratio for all-cause hospitalization was 0.31 (95% CI, 0.08-1.17); and 7 deaths were recorded (1 in the incremental and 6 in the conventional group). At week 24, the incremental HD group had lower declines in urine volume (a difference of 51.0 [95% CI, -0.7 to 102.8] percentage points) and in the averaged urea and creatinine clearances (a difference of 57.9 [95% CI, -22.6 to 138.4] percentage points).

LIMITATIONS

Small sample size, time-limited twice-weekly HD.

CONCLUSIONS

It is feasible to enroll patients beginning maintenance HD into a randomized study of incremental-start HD with adjuvant pharmacotherapy who adhere to the study protocol during follow-up. Larger multicenter clinical trials are indicated to determine the efficacy and safety of incremental HD with longer twice-weekly HD periods.

FUNDING

Funding was provided by Vifor Inc.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov, identifier NCT03740048.

Glycine increases fat-free mass in malnourished haemodialysis patients: a randomized double-blind crossover trial

BACKGROUND

Protein energy wasting is associated with negative outcome in patients under chronic haemodialysis (HD). Branched-chain amino acids (BCAAs) may increase the muscle mass. This post hoc analysis of a controlled double-blind randomized crossover study assessed the impact of BCAAs on nutritional status, physical function, and quality of life.

METHODS

We included 36 chronic HD patient features of protein energy wasting as plasma albumin <38 g/L, and dietary intakes <30 kcal/kg/day and <1 g protein/kg/day. Patients received either oral BCAA (2 × 7 g/day) or glycine (2 × 7 g/day) for 4 months (Period 1), followed by a washout period of 1 month, and then received the opposite supplement (Period 2). The outcomes were lean body mass measured by dual-energy X-ray absorptiometry, fat-free mass index measured by bioelectrical impedance, resting energy expenditure, dietary intake and appetite rating, physical activity and function, quality of life, and blood parameters. Analyses were performed by multiple mixed linear regressions including type of supplementation, months, period, sex, and age as fixed effects and subjects as random intercepts.

RESULTS

Twenty-seven patients (61.2 ± 13.7 years, 41% women) were compliant to the supplementations (consumption >80% of packs) and completed the study. BCAA did not affect lean body mass index and body weight, but significantly decreased fat-free mass index, as compared with glycine (coeff -0.27, 95% confidence interval -0.43 to -0.10, P = 0.002, respectively). BCAA and glycine intake had no effect on the other clinical parameters, blood chemistry tests, or plasma amino acids.

CONCLUSIONS

Branched-chain amino acid did not improve lean body mass as compared with glycine. Unexpectedly, glycine improved fat-free mass index in HD patients, as compared with BCAA. Whether long-term supplementation with glycine improves the clinical outcome remains to be demonstrated.

Chronic haemodialysis in infants and children less than 15 kg

BACKGROUND

Peritoneal dialysis (PD) is the most commonly used kidney replacement therapy in infants and young children with chronic kidney disease (CKD) stage 5. Chronic haemodialysis (cHD) is the alternative treatment when PD is not possible for technical reasons; however, the difficulties that may be encountered are challenging and require clinicians with specialist training and experience. This study aims to describe the clinical history, complications and outcomes in children < 15 kg on cHD.

METHODS

A retrospective, descriptive study of the clinical records of patients weighing < 15 kg on cHD for more than 3 months. The reasons for CKD stage 5, age at start of treatment, duration of haemodialysis, anthropometric and metabolic variables, as well as vascular access, complications and clinical outcome were recorded.

RESULTS

Fifteen patients were included between 2006 and 2018 with a median age at start of cHD of 30 (interquartile range (IQR) 13, 39) months and median duration of 15 (IQR 7.5, 25.3) months. Five patients were younger than 2 years. The median weight at start of treatment was 11.2 (IQR 6.4, 12.8) kg. Forty-five tunneled catheters with a median survival of 106 days were used. The main cause of loss of vascular access was obstruction or displacement dysfunction (39%). The catheter-associated infection rate was 0.76 per 1000 catheter days. Ten patients received a successful kidney transplant, 4 were transferred to PD and one died from complications during abdominal surgery.

CONCLUSIONS

cHD can be successfully performed in children < 15 kg by addressing specific clinical and technical issues.

The spectrum of kidney dysfunction requiring chronic dialysis therapy: Implications for clinical practice and future clinical trials

Staging to capture kidney function and pathophysiologic processes according to severity is widely used in chronic kidney disease or acute kidney injury not requiring dialysis. Yet the diagnosis of "end-stage kidney disease" (ESKD) considers patients as a single homogeneous group, with negligible kidney function, in need of kidney replacement therapy. Herein, we review the evidence behind the heterogeneous nature of ESKD and discuss potential benefits of recasting the terminology used to describe advanced kidney dysfunction from a monolithic entity to a disease with stages of ascending severity. We consider kidney assistance therapy in lieu of kidney replacement therapy to better reconcile all available types of therapy for advanced kidney failure including dietary intervention, kidney transplantation, and dialysis therapy at varied schedules. The lexicon "kidney dysfunction requiring dialysis" (KDRD) with stages of ascending severity based on levels of residual kidney function (RKF)-that is, renal urea clearance-and manifestations related to uremia, fluid status, and other abnormalities is discussed. Subtyping KDRD by levels of RKF could advance dialysis therapy as a form of kidney assistance therapy adjusted based on RKF and clinical symptoms. We focus on intermittent hemodialysis and underscore the need to personalize dialysis treatments and improve characterization of patients included in clinical trials.

Zinc Deficiency, Plasma Fatty Acid Profile and Desaturase Activities in Hemodialysis Patients: Is Supplementation Necessary?

Background: Desaturation and elongation are critical processes in endogenous metabolic fatty acid pathways. Zinc (Zn) is a cofactor for desaturases and elongases enzymes. There is limited evidence regarding the relationships between biomarkers of Zn status, nutritional intake, plasma phospholipid fatty acid profile and clinical outcomes among patients undergoing hemodialysis (HD). Objective: To examine the relationships between dietary and serum levels of Zn and Cu/Zn ratio and to explore associations of these micronutrients with PUFA profile and estimated desaturase and elongase enzyme activities in serum phospholipids among HD patients. Methods: This study included 40 adult patients undergoing hemodialysis treatment. Repeated 24-h recalls were applied for dietary intake assessment. Serum concentration of Zn and Cu were determined using inductively coupled plasma mass spectrometry and fatty acid composition by gas-liquid chromatography. Desaturase and elongase activities were calculated from product-precursor fatty acid ratios. Results: Inadequate dietary Zn intake was found in 55% of HD patients. They all had serum Zn concentration below the reference value of 60 μg/dL (mean 38.8 ± 7.72 μg/dL). Adequate zinc intake was accompanied with significantly higher intake of energy, total fats, SFA, MUFA and proteins. There was no correlation between Zn serum status and Zn intake estimates. Serum Cu/Zn ratio was high, (2.76 ± 0.68), directly and significantly associated with HD period, CRP, BMI, VFA, and inversely with Kt/V, albumin, iron, and iPTH. The n-6/n-3 ratio in plasma phospholipids was elevated (12.25 ± 3.45) and patients with inadequate Zn intake had lower n-3 PUFA intake and status compared to those with adequate intake. Serum Zn concentrations were inversely correlated with linoleic/dihomo-γ-linolenic acid ratio (LA/DGLA) (p = 0.037), related to D6-desaturase activity (p = 0.033) and directly with DGLA relative abundances (p = 0.024). Cu status was inversely associated with EPA level (p = 0.03) and estimates of elongase activity (p = 0.001). Furthermore, positive relationship was found between the Cu/Zn ratio and determined elongase value (p = 0.01). Conclusion: Findings of this study underpin the high prevalence of Zn deficiency and inadequate n-3 PUFA intake and status among subjects undergoing HD. The results obtained indicate that the assessment of Zn status should be a standard parameter of nutritional status screening in HD patients while emphasizing the importance of Cu/Zn determination. Although further research is warranted, Zn and-n-3 PUFA supplementation in HD patients might be beneficial for the prevention and attenuation of adverse health outcomes.

Is there an association between the plasma levels of uremic toxins from gut microbiota and anemia in patients on hemodialysis?

BACKGROUND

Anemia is one of the most frequent complications in patients with chronic kidney disease (CKD). Despite being multifactorial, the relative or absolute deficiency of erythropoietin production is the leading cause. Recent studies have shown that uremic toxins produced by the gut microbiota also may play a role in the genesis of anemia in these patients.

OBJECTIVE

To evaluate the possible association between uremic toxins plasma levels and anemia in patients with CKD on hemodialysis (HD).

METHODS

This cross-sectional study evaluated one hundred fifty-four patients (53.2% men, 51.2 ± 11.2 years, hemoglobin (Hb) levels of 11.2 ± 1.6 g/dL). Biochemical variables such as urea, creatinine, hemoglobin, hematocrit, were measured according to standard methods and uremic toxins such as indoxyl sulfate (IS), indole-3-acetic acid (IAA), p-cresyl sulfate (p-CS) plasma levels were measured by reverse-phase high-performance liquid chromatography (RP-HPLC).

RESULTS

The levels of uremic toxins such as IS, IAA, p-CS were increased in all patients. However, no correlation was found between uremic toxins plasma levels and anemia parameters. Only patients with Hb < 11 g/dL presented a negative correlation between hematocrit and IAA plasma levels.

CONCLUSION

There is no strong evidence that uremic toxins produced by the gut microbiota may be associated with anemia in patients with CKD on HD.

Monitoring dialysis adequacy: history and current practice

Dialysis adequacy for pediatric patients has largely followed the trends in adult dialysis by judging the success or adequacy of peritoneal or hemodialysis with urea kinetic modeling. While this provides a starting point to establish a dose of dialysis, it is clear that urea is only part of the picture. Many clinical parameters and interventions now have been identified that are just as impactful on mortality and morbidly as urea clearance. As such, our concept of adequacy is evolving to include non-urea parameters and assessing the impact that following an "adequate therapy" has on patient lives. As we move to a new era, we consider the impact these therapies have on patients and how it affects the quality of their lives; we must take these factors into consideration to achieve a therapy that is not just adequate, but livable.

Renal replacement treatment initiation with twice-weekly versus thrice-weekly haemodialysis in patients with incident dialysis-dependent kidney disease: rationale and design of the TWOPLUS pilot clinical trial

INTRODUCTION

The optimal haemodialysis (HD) prescription-frequency and dose-for patients with incident dialysis-dependent kidney disease (DDKD) and substantial residual kidney function (RKF)-that is, renal urea clearance ≥2 mL/min/1.73 m2 and urine volume ≥500 mL/day-is not known. The aim of the present study is to test the feasibility and safety of a simple, reliable prescription of incremental HD in patients with incident DDKD and RKF.

METHODS AND ANALYSIS

This parallel-group, open-label randomised pilot trial will enrol 50 patients from 14 outpatient dialysis units. Participants will be randomised (1:1) to receive twice-weekly HD with adjuvant pharmacological therapy for 6 weeks followed by thrice-weekly HD (incremental HD group) or outright thrice-weekly HD (standard HD group). Age ≥18 years, chronic kidney disease progressing to DDKD and urine output ≥500 mL/day are key inclusion criteria; patients with left ventricular ejection fraction <30% and acute kidney injury requiring dialysis will be excluded. Adjuvant pharmacological therapy (ie, effective diuretic regimen, patiromer and sodium bicarbonate) will complement twice-weekly HD. The primary feasibility end points are recruitment rate, adherence to the assigned HD regimen, adherence to serial timed urine collections and treatment contamination. Incidence rate of clinically significant volume overload and metabolic imbalances in the first 3 months after randomisation will be used to assess intervention safety.

ETHICS AND DISSEMINATION

The study has been reviewed and approved by the Institutional Review Board of Wake Forest School of Medicine in North Carolina, USA. Patient recruitment began on 14 June 2019, was paused between 13 March 2020 and 31 May 2020 due to COVID-19 pandemic, resumed on 01 June 2020 and will last until the required sample size has been attained. Participants will be followed in usual care fashion for a minimum of 6 months from last individual enrolled. All regulations and measures of ethics and confidentiality are handled in accordance with the Declaration of Helsinki.

TRIAL REGISTRATION NUMBER

NCT03740048; Pre-results.

The Nitty-Gritties of Kt/Vurea Calculations in Hemodialysis and Peritoneal Dialysis

In advanced Chronic Kidney Disease, patients require renal replacement therapy (dialysis or transplantation) for clearance of toxins, electrolyte and acid-base balance and removal of excess fluid. Dialysis adequacy should be taken into consideration in the adjustment of the dialysis prescription. Kt/Vurea is one method of measuring dialysis adequacy that is commonly used in clinical practice. Different formulae for calculating Kt/V are available. The appropriate Kt/V formula to be used depends on the clinical scenario, as well as parameters such as gender and size of patient, frequency of dialysis, mode of dialysis (ie hemodialysis vs, peritoneal dialysis), inter-dialysis weight gain, clinical symptoms, complications (fluid overload, hyperkalemia, intolerance to dialysis, etc), and residual kidney function. Nutrition parameters including serum protein and albumin levels, vitamin B12 and β2-microglobulin levels should be factored into the assessment of dialysis adequacy. In this review, we have described how Kt/Vurea is calculated in hemodialysis and peritoneal dialysis with examples. We reviewed the available literature by searching for papers related to calculating Kt/Vurea, single pool Kt/V, double pool Kt/V, weekly Kt/V, standard Kt/V, surface area normalized Kt/V, and various equations commonly practiced in clinical practice. We found several original articles, some review articles along with detailed information from manufacturers of different dialyzers published on their websites or as package inserts. Understanding the different equations available for calculating Kt/Vurea and the application of these results in the clinical setting is important for refining patient care and for designing clinical studies.

Psychosocial Dimensions in Hemodialysis Patients on Kidney Transplant Waiting List: Preliminary Data

Although the donation rate for deceased and living kidneys has been increasing, the donor organ availability meets only the 30% of kidney needs in Italy. Consequently, hemodialysis patients stay for a long time, an average of 3.2 years, on a waiting list for a kidney transplant with consequent relevant psychological distress or even full-fledged psychiatric disorders, as diagnosed with traditional psychiatric nosological systems. Recent studies report, however, a higher prevalence of other psychosocial syndromes, as diagnosed by using the Diagnostic Criteria for Psychosomatic Research (DCPR) in medically ill and kidney transplant patients. Nevertheless, no data regarding DCPR prevalence are available in patients waitlisted for a renal transplant (WKTs). Thus, the primary aim of this study was to identify sub-threshold or undetected syndromes by using the DCPR and, secondly, to analyze its relationship with physical and psychological symptoms and daily-life problems in WKTs. A total of 30 consecutive WKTs were assessed using the DCPR Interview and the MINI International Neuropsychiatric Interview 6.0. The Edmonton Symptom Assessment System (ESAS) and the Canadian Problem Checklist were used to assess physical and psychological distress symptoms and daily-life problems. A total of 60% of patients met the criteria for at least one DCPR diagnosis; of them, 20% received one DCPR diagnosis (DCPR = 1), and 40% more than one (DCPR > 1), especially the irritability cluster (46.7%), Abnormal Illness Behavior (AIB) cluster (23.3%) and somatization cluster (23.3%). Fifteen patients met the criteria for an ICD diagnosis. Among patients without an ICD-10 diagnosis, 77.8% had at least one DCPR syndrome (p < 0.05). Higher scores on ESAS symptoms (i.e., tiredness, nausea, depression, anxiety, feeling of a lack of well-being and distress), ESAS-Physical, ESAS-Psychological, and ESAS-Total were found among DCPR cases than DCPR non-cases. In conclusion, a high prevalence of DCPR diagnoses was found in WKTs, including those who resulted to be ICD-10 non-cases. The joint use of DCPR and other screening tools (e.g., ESAS) should be evaluated in future research as part of a correct psychosocial assessment of WKTs.

Ultrasonography of Quadriceps Femoris Muscle and Subcutaneous Fat Tissue and Body Composition by BIVA in Chronic Dialysis Patients

Protein Energy Wasting (PEW) in hemodialysis (HD) patients is a multifactorial condition due to specific pathology-related pathogenetic mechanisms, leading to loss of skeletal muscle mass in HD patients. Computed Tomography and Magnetic Resonance Imaging still represent the gold standard techniques for body composition assessment. However, their widespread application in clinical practice is difficult and body composition evaluation in HD patients is mainly based on conventional anthropometric nutritional indexes and bioelectrical impedance vector analysis (BIVA). Little data is currently available on ultrasound (US)-based measurements of muscle mass and fat tissue in this clinical setting. The purpose of our study is to ascertain: (1) if there are differences between quadriceps rectus femoris muscle (QRFM) thickness and abdominal/thigh subcutaneous fat tissue (SFT) measured by US between HD patients and healthy subjects; (2) if there is any correlation between QRFM and abdominal/thigh SFT thickness by US, and BIVA/conventional nutritional indexes in HD patients. We enrolled 65 consecutive HD patients and 33 healthy subjects. Demographic and laboratory were collected. The malnutrition inflammation score (MIS) was calculated. Using B-mode US system, the QRFM and SFT thicknesses were measured at the level of three landmarks in both thighs (superior anterior iliac spine, upper pole of the patella, the midpoint of the tract included between the previous points). SFT was also measured at the level of the periumbilical point. The mono frequency (50 KHz) BIVA was conducted using bioelectrical measurements (Rz, resistance; Xc, reactance; adjusted for height, Rz/H and Xc/H; PA, phase angle). 58.5% were men and the mean age was 69 (SD 13.7) years. QRFM and thigh SFT thicknesses were reduced in HD patients as compared to healthy subjects (p < 0.01). Similarly, also BIVA parameters, expression of lean body mass, were lower (p < 0.001), except for Rz and Rz/H in HD patients. The average QRFM thickness of both thighs at top, mid, lower landmarks were positively correlated with PA and body cell mass (BCM) by BIVA, while negatively correlated with Rz/H (p < 0.05). Abdominal SFT was positively correlated with PA, BCM and basal metabolic rate (BMR) (p < 0.05). Our study shows that ultrasound QRFM and thigh SFT thicknesses were reduced in HD patients and that muscle ultrasound measurements were significantly correlated with BIVA parameters.

Relationship between residual kidney function and symptom burden in haemodialysis patients

BACKGROUND

Residual kidney function (RKF) has been associated with improved solute clearance and survival in haemodialysis (HD) patients. However, whether RKF impacts symptom burden in HD patients is unknown.

AIMS

To determine the prevalence of RKF in HD patients and to explore associations between higher levels of RKF with symptom burden, as well as clinical and biochemical parameters.

METHODS

This is a single-centre, retrospective, observational study. RKF was assessed as urea clearance (KRU) by interdialytic urine collection. Symptom burden was measured using the palliative care outcome scale renal questionnaire.

RESULTS

A total of 90 maintenance HD patients was recruited; 31.9% had KRU ≥1 mL/min/1.73 m² . Patients with KRU ≥1 mL/min/1.73 m² reported fewer symptoms (5.3 ± 3.5 vs 7.7 ± 3.8) (P = 0.011), including less shortness of breath (15% vs 55%) (P = 0.0013) and vomiting (0% vs 30%) (P = 0.0016). Higher RKF was associated with lower β₂ -microglobilin (P < 0.0001), and lower serum potassium (P = 0.02), but no difference in phosphate, haemoglobin, C-reactive protein or serum albumin.

CONCLUSION

Higher RKF was significantly associated with fewer symptoms, and lower serum β₂ -microglobulin and potassium, suggesting that strategies to preserve RKF may be beneficial.

Renal Association Clinical Practice Guideline on Haemodialysis

This guideline is written primarily for doctors and nurses working in dialysis units and related areas of medicine in the UK, and is an update of a previous version written in 2009. It aims to provide guidance on how to look after patients and how to run dialysis units, and provides standards which units should in general aim to achieve. We would not advise patients to interpret the guideline as a rulebook, but perhaps to answer the question: "what does good quality haemodialysis look like?"The guideline is split into sections: each begins with a few statements which are graded by strength (1 is a firm recommendation, 2 is more like a sensible suggestion), and the type of research available to back up the statement, ranging from A (good quality trials so we are pretty sure this is right) to D (more like the opinion of experts than known for sure). After the statements there is a short summary explaining why we think this, often including a discussion of some of the most helpful research. There is then a list of the most important medical articles so that you can read further if you want to - most of this is freely available online, at least in summary form.A few notes on the individual sections: 1. This section is about how much dialysis a patient should have. The effectiveness of dialysis varies between patients because of differences in body size and age etc., so different people need different amounts, and this section gives guidance on what defines "enough" dialysis and how to make sure each person is getting that. Quite a bit of this section is very technical, for example, the term "eKt/V" is often used: this is a calculation based on blood tests before and after dialysis, which measures the effectiveness of a single dialysis session in a particular patient. 2. This section deals with "non-standard" dialysis, which basically means anything other than 3 times per week. For example, a few people need 4 or more sessions per week to keep healthy, and some people are fine with only 2 sessions per week - this is usually people who are older, or those who have only just started dialysis. Special considerations for children and pregnant patients are also covered here. 3. This section deals with membranes (the type of "filter" used in the dialysis machine) and "HDF" (haemodiafiltration) which is a more complex kind of dialysis which some doctors think is better. Studies are still being done, but at the moment we think it's as good as but not better than regular dialysis. 4. This section deals with fluid removal during dialysis sessions: how to remove enough fluid without causing cramps and low blood pressure. Amongst other recommendations we advise close collaboration with patients over this. 5. This section deals with dialysate, which is the fluid used to "pull" toxins out of the blood (it is sometimes called the "bath"). The level of things like potassium in the dialysate is important, otherwise too much or too little may be removed. There is a section on dialysate buffer (bicarbonate) and also a section on phosphate, which occasionally needs to be added into the dialysate. 6. This section is about anticoagulation (blood thinning) which is needed to stop the circuit from clotting, but sometimes causes side effects. 7. This section is about certain safety aspects of dialysis, not seeking to replace well-established local protocols, but focussing on just a few where we thought some national-level guidance would be useful. 8. This section draws together a few aspects of dialysis which don't easily fit elsewhere, and which impact on how dialysis feels to patients, rather than the medical outcome, though of course these are linked. This is where home haemodialysis and exercise are covered. There is an appendix at the end which covers a few aspects in more detail, especially the mathematical ideas. Several aspects of dialysis are not included in this guideline since they are covered elsewhere, often because they are aspects which affect non-dialysis patients too. This includes: anaemia, calcium and bone health, high blood pressure, nutrition, infection control, vascular access, transplant planning, and when dialysis should be started.

How to set the stage for a full-fledged clinical trial testing 'incremental haemodialysis'

Most people who make the transition to maintenance haemodialysis (HD) therapy are treated with a fixed dose of thrice-weekly HD (3HD/week) regimen without consideration of their residual kidney function (RKF). The RKF provides an effective and naturally continuous clearance of both small and middle molecules, plays a major role in metabolic homeostasis, nutritional status and cardiovascular health, and aids in fluid management. The RKF is associated with better patient survival and greater health-related quality of life. Its preservation is instrumental to the prescription of incremental (1HD/week to 2HD/week) HD. The recently heightened interest in incremental HD has been hindered by the current limitations of the urea kinetic model (UKM), which tend to overestimate the needed dialysis dose in the presence of a substantial RKF. A recent paper by Casino and Basile suggested a variable target model (VTM), which gives more clinical weight to the RKF and allows less frequent HD treatments at lower RKF as opposed to the fixed target model, based on the wrong concept of the clinical equivalence between renal and dialysis clearance. A randomized controlled trial (RCT) enrolling incident patients and comparing incremental HD (prescribed according to the VTM) with the standard 3HD/week schedule and focused on hard outcomes, such as survival and health-related quality of life of patients, is urgently needed. The first step in designing such a study is to compute the 'adequacy lines' and the associated fitting equations necessary for the most appropriate allocation of the patients in the two arms and their correct and safe follow-up. In conclusion, the potentially important clinical and financial implications of the incremental HD render it highly promising and warrant RCTs. The UKM is the keystone for conducting such studies.

Acute kidney injury management using intermittent low efficiency haemodiafiltration in a critical care unit: 39 dogs (2012-2015)

BACKGROUND

Veterinary studies describing acute kidney injury (AKI) management using renal replacement therapy (RRT) are limited and have primarily focused on intermittent haemodialysis in North American populations. European data are lacking, although differences in populations, pathogen and toxin exposure and RRT modalities may exist between Europe and North America. The present study reviewed RRT-managed cases from the intensive care unit (ICU) of VetAgro Sup, Lyon, France, for the period 2012-2015. The aims were to describe a 4-h RRT protocol of intermittent low efficiency haemodiafiltration, population characteristics and outcomes in canine AKI cases requiring RRT and to identify prognostic variables. We defined DeltaCreat/h as the difference between the serum creatinine level after RRT treatment N and that before treatment N + 1 divided by the time between treatments (in hours).

RESULTS

Thirty-nine dogs were included, and 67% were males. The median (range) age, weight, hospitalization length and number of RRT treatments were 4.4 (0.25-15) years, 26.6 (6.7-69) kg, 8 (1-23) days and 3 (1-8) treatments, respectively. The main AKI causes were leptospirosis (74.4%) and nephrotoxins (15.4%). Age (4.0 vs 5.4 years; P = 0.04), admission urine output (0.5 mL/kg/h vs 0 mL/kg/h; P = 0.02) and hospitalization length (10 vs 4 days; P < 0.001) differed between survivors and non-survivors. Hospitalization length [odds ratio (OR) = 0.4], number of treatments (OR = 5.1), serum potassium level on day 2 (OR = 1.9), DeltaCreat/h between the first and second treatments (OR = 1.2), and UOP during hospitalization (OR = 0.2) were correlated with outcome. The main causes of death were euthanasia (44%) and haemorrhagic diatheses (33%). The overall survival rate was 54%, with 55% of survivors discharged with a median creatinine < 240 µmol/L.

CONCLUSIONS

This is the first description in the veterinary literature of a 4-h protocol of intermittent low efficiency haemodiafiltration to provide RRT in a veterinary critical care unit. While this protocol appears promising, the clinical application of this protocol requires further investigation. Among parameters associated with survival, UOP and DeltaCreat/h between the first and second RRT treatments may be prognostic indicators. The applicability of these parameters to other populations is unknown, and further international, multicentre prospective studies are warranted to confirm these preliminary observations.

Volume of urea cleared as a therapy dosing guide for more frequent hemodialysis

INTRODUCTION

With dialysis delivery systems that operate at low dialysate flow rates, prescriptions for more frequent hemodialysis (HD) employ dialysate volume as the primary parameter for small solute removal rather than blood-side urea dialyzer clearance (K). Such delivery systems, however, yield dialysate concentrations that almost completely saturate with blood (water), suggesting that the volume of urea cleared (the product of K and treatment time or Kt) can be readily estimated from the prescribed dialysate volume to target small solute removal. Methods For more frequent HD, we examined the volume of urea cleared per treatment required to achieve a minimal dose of small solute removal, comparing results based on body surface area (BSA) with those based on KDOQI clinical practice guidelines, that is, a weekly stdKt/V of 2.1. Estimates of the target volume of urea cleared were calculated for 4, 5, and 6 treatments per week, and compared for patients with different anthropometric estimates of total body water volume (V_ant ). BSA was assumed proportional to V_ant ^0.8 , and residual kidney function was neglected. Findings Whether based on BSA or weekly stdKt/V of 2.1, the target volume of urea cleared per treatment required to achieve a minimal dose of small solute removal was lower at higher treatment frequency. As with conventional thrice-weekly HD, target volumes of urea cleared for more frequent HD based on BSA were larger for patients with small V_ant and smaller for patients with large V_ant than those based on a weekly stdKt/V of 2.1. Discussion Prescription of more frequent HD using the volume of urea cleared per treatment, calculated from the prescribed dialysate volume, is simple in principle and can be readily implemented in clinical practice when using dialysis delivery systems that operate at low dialysate flow rates. Other aspects of dialysis adequacy require additional consideration.

Residual renal function in incremental haemodialysis

Background

Equivalent renal clearance (EKR) and standard clearance (stdK) are continuous-equivalent measures of urea clearance and include residual renal function (RRF), if calculated appropriately. RRF is qualitatively better than dialysis with equivalent urea clearance. Instructions for calculating stdKt/V (stdK scaled by urea distribution volume) and its target value (2.3) are presented in the Kidney Disease Outcomes Quality Initiative (KDOQI) 2015 guidelines. EKR targets have not been defined in the current guidelines.

Methods

The stdKt/V in the presence of RRF was calculated with the classic double-pool urea kinetic model and with the Daugirdas modification, which accentuates the renal contribution. The EKR/V (EKR scaled by urea distribution volume) was calculated with nominal and adjusted renal clearance (renal urea clearance multiplied by a weighting factor). New prescriptions with different continuous clearance targets were generated by a computer program.

Results

The contribution of RRF can be weighted flexibly in EKR/V by adjusting the renal clearance value. A new therapeutic index, EKR/V_a (adjusted total EKR/V), was introduced. In 62 incremental dialysis sessions of 16 patients with a renal urea clearance (K_r) of over 1 mL/min, the Daugirdas stdKt/V was, on average, 7.5% higher than classic stdK/V and adjusted EKR/V was 14.4% higher than unadjusted EKR/V.

Conclusions

The stdKt/V is not an optimal descriptor of haemodialysis urea clearance. With EKR/V, the role of RRF can be evaluated more sensibly. Using adjusted EKR/V as the target permits less frequent incremental dialysis.

Is 3-Carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF) a Clinically Relevant Uremic Toxin in Haemodialysis Patients?

3-Carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF) is a metabolite of furan fatty acid and a marker of fish oil intake. CMPF is described as a protein-bound uremic toxin and interacts with free oxygen radicals, which can induce cell damages. However, the clinical consequences of CMPF accumulation in haemodialysis patients remain poorly documented. The aims of this study are to investigate potential association between CMPF levels and (i) biochemical and nutritional parameters; (ii) cardiovascular events and (iii) mortality. Two hundred and fifty-two patients undergoing maintenance haemodialysis were included. Routine clinical biochemistry tests and assay for CMPF by HPLC technique were performed at the inclusion. Body composition parameters were measured using a bioimpedance spectroscopy method. The enrolled patients were prospectively monitored for cardiovascular events and mortality. CMPF level was positively correlated with nutritional parameters and lean mass and is significantly higher in patients without protein-energy wasting. However, the multivariate linear regression analysis indicated that CMPF level was not independently associated with albumin, prealbumin, creatinemia and body mass index. Elevated serum CMPF was not associated with mortality and cardiovascular morbidity. Our results indicate that CMPF is not a relevant uremic toxin in haemodialysis and in contrast could be a marker of healthy diet and omega 3 intakes.

Mathematical Representation of Standard Kt/V Including Ultrafiltration and Residual Renal Function

A new formula for calculating standard Kt/V from clinical data has been derived mathematically. It is based on using the relation between eKt/V and the pre- and postdialysis concentrations in order to find the steady state concentrations. The resulting expression for standard Kt/V depends on the treatment schedule (number, length, and spacing of treatments), residual renal function, and eKt/V and relative ultrafiltration volume of each individual treatment. These results include the effects of ultrafiltration and residual renal function also in the case with unequal treatments that may be arbitrarily distributed over the week. The new formula is found to agree, within small fractions of a percentage, with standard Kt/V from simulations of 3 and 5 days per week schedules. Several approximations are also suggested and their accuracies analyzed. It is shown that the use of the midweek eKt/V and ultrafiltration for all treatments of the week is an acceptable approximation. In the presence of residual renal function, the timing of the treatments is an important factor, and particularly in this case, the new formula shows improved accuracy over previously published formulas.

Weekly Standard Kt/Vurea and Clinical Outcomes in Home and In-Center Hemodialysis

BACKGROUND AND OBJECTIVES

Patients undergoing hemodialysis with a frequency other than thrice weekly are not included in current clinical performance metrics for dialysis adequacy. The weekly standard Kt/Vurea incorporates treatment frequency, but there are limited data on its association with clinical outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We used multivariable regression to examine the association of dialysis standard Kt/Vurea with BP and metabolic control (serum potassium, calcium, bicarbonate, and phosphorus) in patients incidental to dialysis treated with home (n=2373) or in-center hemodialysis (n=109,273). We further used Cox survival models to examine the association of dialysis standard Kt/Vurea with mortality, hospitalization, and among patients on home hemodialysis, transfer to in-center hemodialysis.

RESULTS

After adjustment for potential confounders, patients with dialysis standard Kt/Vurea <2.1 had higher BPs compared with patients with standard Kt/Vurea 2.1 to <2.3 (3.4 mm Hg higher [P<0.001] for home hemodialysis and 0.9 mm Hg higher [P<0.001] for in-center hemodialysis). There were no clinically meaningful associations between dialysis standard Kt/Vurea and markers of metabolic control, irrespective of dialysis modality. There was no association between dialysis standard Kt/Vurea and risk for mortality, hospitalization, or transfer to in-center hemodialysis among patients undergoing home hemodialysis. Among patients on in-center hemodialysis, dialysis standard Kt/Vurea <2.1 was associated with higher risk (adjusted hazard ratio, 1.11; 95% confidence interval, 1.07 to 1.14) and standard Kt/Vurea ≥2.3 was associated with lower risk (adjusted hazard ratio, 0.97; 95% confidence interval, 0.94 to 0.99) for death compared with standard Kt/Vurea 2.1 to <2.3. Additional analyses limited to patients with available data on residual kidney function showed similar relationships of dialysis and total (dialysis plus kidney) standard Kt/Vurea with outcomes.

CONCLUSIONS

Current targets for standard Kt/Vurea have limited utility in identifying individuals at increased risk for adverse clinical outcomes for those undergoing home hemodialysis but may enhance risk stratification for in-center hemodialysis.

The variable target model: a paradigm shift in the incremental haemodialysis prescription

Background

The recent interest in incremental haemodialysis (HD) is hindered by the current prescription based on a fixed target model (FTM) for the total (dialytic + renal) equivalent continuous clearance (ECC). The latter is expressed either as standard Kt/V (stdKt/V), i.e. the pre-dialysis averaged concentration of urea-based ECC, or EKRc, i.e. the time averaged concentration-based ECC, corrected for volume (V) = 40 L. Accordingly, there are two different targets: stdKt/V = 2.3 volumes per week (v/wk) and EKRc = 13 mL/min/40 L. However, fixing the total ECC necessarily implies perfect equivalence of its components-the residual renal urea clearance (Kru) and dialysis clearance (Kd). This assumption is wrong because Kru has much greater clinical weight than Kd. Here we propose that the ECC target varies as an inverse function of Kru, from a maximum value in anuria to a minimum value at Kru levels not yet requiring dialysis. The aim of the present study was to compare the current FTM with the proposed variable target model (VTM).

Methods

The double pool urea kinetic model was used to model dialysis sessions for 360 virtual patients and establish equations predicting the ECC as a function of Kd, Kru and the number of sessions per week. An end-dialysis urea distribution V of 35 L (corresponding to a body surface area of 1.73 m 2 ) was used, so that the current EKRc target of 13 mL/min/40 L could be recalculated at an EKRc 35 value of 12 mL/min/35 L equal to 12 mL/min/1.73 m 2 . The latter also coincides with the maximum value of the EKRc 35 variable target in anuria. The minimum target value of EKRc 35 was assumed to coincide with Kru corrected for V = 35 L (i.e. Krc 35 = 6 mL/min/1.73 m 2 ). The corresponding target for stdKt/V was assumed to vary from 2.3 v/wk at Krc 35 = 0 to 1.7 v/wk at Krc 35 = 6 mL/min/1.73 m 2 . On this basis, the variable target values can be obtained from the following linear equations: target EKRc 35 = 12 - Krc 35 ; target stdKt/V = 2.3 - 0.1 × Krc 35 . Two versions of stdKt/V were considered: the classic version (stdKt/V Gotch ) with Kru at 70%, and the current version (stdKt/V Daug ) with Kru at 100%.

Results

The VTM with stdKt/V Gotch produces results very close to those using the FTM with stdKt/V Daug . Once-weekly HD is virtually not allowed by the FTM. In contrast, the VTM allows dialysis to start at Krc 35 ∼5 mL/min/1.73 m 2 on a once-weekly HD schedule, at least in relatively healthy patients; this schedule can be maintained until Krc 35 falls below 4 mL/min/1.73 m 2 , at which point the schedule should be changed to a twice-weekly HD schedule, that, in turn, could be maintained until Krc 35 falls below 2 mL/min/1.73 m 2 .

Conclusions

A paradigm shift from the FTM to the VTM in the prescription of incremental HD is proposed, whereby the VTM would allow less frequent treatments at lower Kru, with important clinical and economic implications. This approach is likely to be safe but needs to be confirmed by randomized controlled trials.

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.

Clinical safety and performance of VIVIA: a novel home hemodialysis system

Background

The VIVIA Hemodialysis System (Baxter Healthcare Corporation, Deerfield, IL, USA) was designed for patient use at home to reduce the burden of treatment and improve patient safety. It has unique features including extended use of the dialyzer and blood set through in situ hot-water disinfection between treatments; generation of on-line infusible-quality dialysate for automated priming, rinseback and hemodynamic support during hypotension and a fully integrated access disconnect sensor.

Methods

The safety and performance of VIVIA were assessed in two clinical studies. A first-in-man study was a prospective, single-arm study that involved 22 prevalent hemodialysis (HD) patients who were treated for ∼4 h, four times a week, for 10 weeks. A second clinical study was a prospective, single-arm study (6-8 h of dialysis treatment at night three times a week) that involved 17 prevalent patients treated for 6 weeks.

Results

There were 1114 treatments from the two studies (first-in-man study, 816; extended duration study, 298). Adverse events (AEs) were similar in the two studies to those expected for prevalent HD patients. No deaths and no device-related serious AEs occurred. Adequacy of dialysis ( Kt / V ) urea in both clinical trials was well above the clinical guidelines. VIVIA performed ultrafiltration accurately as prescribed in the two studies. The majority of patients achieved 10 or more uses of the dialyzer. Endotoxin levels and bacterial dialysate sampling met infusible-quality dialysate standards.

Conclusion

These results confirm the safety and expected performance of VIVIA.

Long term variation of serum levels of uremic toxins in patients treated by post-dilution high volume on-line hemodiafiltration in comparison to standard low-flux bicarbonate dialysis: results from the REDERT study

PURPOSE OF THE STUDY

Little information have been provided till now regarding the effect of high volume HDF (hv-OL-HDF) in respect to standard bicarbonate dialysis (BHD) in medium-long term protein-bound toxins removal.

PROCEDURES

A randomised cross-over multicentre study (REDERT study) was designed to compare the effects of hv-OL-HDF and low-flux BHD on uremic toxins serum levels in 36 chronic dialysis patients followed for 13 months. Group 1 patients were treated with BHD (Treatment A) for 6 months, and afterwards, they were transferred to hv-OL-HDF for a further 6 months (Treatment B). Group 2 patients were treated with Treatment B for 6 months, and afterwards, they were transferred to Treatment A for a further 6 months. Total and free pre-dialysis indoxyl-sulfate (IS) and p-cresyl-sulfate (pCS) were determined starting a midweek dialysis session at baseline and after six months of hv-OL-HDF or BHD. IS and pCS, were simultaneously measured, by liquid chromatography/electrospray ionization-tandem mass spectrometry, Kt/v and pre and post-dialysis b-2microglobulin (b2MG) levels were measured every three months.

RESULTS

Kt/V was significantly increased in hv-OL-HDF (from 1.47 ± 0.24 to 1.49 ± 0.16; p < 0.01) and was reduced in BHD (from 1.51 ± 0.2 to 1.36 ± 0.21; p < 0.001). The mean infusion volume in HDF was 20.9 ± 2.1 L with a mean total convective volume of 23.8 ± 2.3 L and a significant removal of b2MG was obtained in hv-OL-HDF at month 3 and month 6. Both free and total levels of IS and pCS were significantly reduced in hv-OL-HDF at month 6 in respect to BHD.

CONCLUSIONS

In the present study we confirm the assumption that post-HDF is an effective technique in small and protein-bound uremic toxins removal.

INTRODUCTION

Residual Kidney Function: Implications in the Era of Personalized Medicine

The association of residual kidney function (RKF) with improved outcomes in peritoneal dialysis and hemodialysis patients is now widely recognized. RKF provides substantial volume and solute clearance even after dialysis initiation. In particular, RKF provides clearance of nonurea solutes, many of which are potential uremic toxins and not effectively removed by conventional hemodialysis. The presence of RKF provides a distinct advantage to incident dialysis patients and is an opportunity for nephrologists to individualize dialysis treatments tailored to their patients' unique solute, volume, and quality of life needs. The benefits of RKF present the opportunity to personalize the management of uremia.

Hemodialysis Treatment Time: As Important as it Seems?

Hemodialysis treatment time and Kt/V can both be considered to be primary measures of hemodialysis adequacy, because when either goes to zero, mortality is certain in patients without residual kidney function. Treatment time is important, but it needs to be adjusted based on surface-area-normalized Kt/V, residual kidney function, and expected ultrafiltration rate. Rescaling dose of dialysis measured as Kt/V to body surface area prevents ultrashort dialysis in small patients, women, and children with minimal residual kidney function. Most if not all of the observational studies of associations between outcome and dialysis session length are probably confounded by dose targeting bias. Once adequate Kt/V (taking into account body surface area) has been provided, adequate dialysis time probably is most relevant in terms of limiting the need for a high fluid removal rate. The latter may adversely impact survival by causing recurrent ischemia to cardiovascular and other tissues. There is little high-quality evidence at this time to support a minimum 4-hour treatment time for all patients, regardless of body size, solute removal, or residual kidney function. On the other hand, there is little evidence that prolonging weekly treatment time up to 24 hours per week is harmful. The final decision regarding treatment time is best individualized, based on patient acceptability and experience, residual kidney function, body surface-area-normalized Kt/V, and expected ultrafiltration rate.

Is Hemodialysis Patient Survival Dependent upon Small Solute Clearance (Kt/V)?: If So How Can Kt/V be Adjusted to Prevent Under Dialysis in Vulnerable Groups?

Small solute clearance achieved during a single hemodialysis session has been traditionally evaluated by urea clearance, normalized for total body water (Kt/Vurea) for more than 30 years. By consensus, the target sessional KtVurea for thrice weekly treatments has been increased from 0.9 to 1.2 over the years. Although this is supported by observational studies, there is a fundamental lack of prospective studies to support this threshold target. In clinical practice achieving sessional Kt/Vurea targets are most closely followed in the US. Yet there appears to be a paradox in that by following Kt/Vurea targets in the US hemodialysis patient survival is better for men and the obese, the opposite of what is seen in the general population. Delivery of a lower dose of hemodialysis to women and smaller men can be explained by underestimation of total body water. The advent of bioimpedance techniques which can measure both body water and body composition will potentially allow a rescaling and re-evaluation of the importance of small solute clearances (Kt/Vurea) in the hemodialysis patient population.

Dose Targeting Metrics in Conventional and Intensive Maintenance Dialysis

Hemodialysis has come a long way since its early days and is a life sustaining therapy for millions of people with end-stage kidney disease throughout the world. Although thrice weekly hemodialysis remains the most common form of renal replacement therapy, other therapies such as more frequent, prolonged dialysis modalities have seen a rise recently. In this review, we compare and contrast methods for measuring the dialysis dose, with a focus on small molecule clearance (Kt/V_urea ) among various dialysis modalities. We also describe newer on-line methods to measure dialysis and limitations to current adequacy measurement. Distinguishing dialysis adequacy from adequate treatment of the patient is also emphasized.

Association of low serum aluminum level with mortality in hemodialysis patients

Background

The National Kidney Foundation–Kidney Disease Outcomes Quality Initiative recommends that the serum aluminum level (SAL) should be below 20 µg/L for patients with maintenance hemodialysis (MHD). However, serum aluminum may have toxic effects on MHD patients even when it is in the apparently acceptable range (below 20 µg/L).

Methods

The Medical Ethics Committee approved this study. Initially, 954 MHD patients in dialysis centers were recruited. A total of 901 patients met the inclusion criteria and were followed-up for 1 year. Patients were stratified by SAL into four equal-sized groups: first quartile (<6 µg/L), second quartile (6–9 µg/L), third quartile (9–13 µg/L), and fourth quartile (>13 µg/L). Demographic, biochemical, and dialysis-related data were obtained for analyses. A linear regression model was applied to identify factors associated with SAL. Cox proportional hazard model was used to determine the significance of variables in prediction of mortality.

Results

Only 9.3% of MHD patients had SALs of 20 µg/L or more. At the end of the follow-up, 54 patients (6%) died, and the main cause of death was cardiovascular disease. Kaplan–Meier survival analysis showed that patients in the fourth SAL quartile had higher mortality than those in the first SAL quartile (log rank test, χ²=13.47, P=0.004). Using the first quartile as reference, Cox multivariate analysis indicated that patients in the third quartile (hazard ratio =1.31, 95% confidence interval =1.12–1.53, P=0.038) and the fourth quartile (hazard ratio =3.19, 95% confidence interval =1.08–8.62, P=0.048) had increased risk of all-cause mortality.

Conclusion

This study demonstrates that SAL, even when in an apparently acceptable range (below 20 µg/L), is associated with increased mortality in MHD patients. The findings suggest that avoiding exposure of aluminum as much as possible is warranted for MHD patients.

Preservation of residual kidney function in hemodialysis patients: reviving an old concept

Residual kidney function (RKF) may confer a variety of benefits to patients on maintenance dialysis. RKF provides continuous clearance of middle molecules and protein-bound solutes. Whereas the definition of RKF varies across studies, interdialytic urine volume may emerge as a pragmatic alternative to more cumbersome calculations. RKF preservation is associated with better patient outcomes including survival and quality of life and is a clinical parameter and research focus in peritoneal dialysis. We propose the following practical considerations to preserve RKF, especially in newly transitioned (incident) hemodialysis patients: (1) periodic monitoring of RKF in hemodialysis patients through urine volume and including residual urea clearance with dialysis adequacy and outcome markers such as anemia, fluid gains, minerals and electrolytes, nutritional, status and quality of life; (2) avoidance of nephrotoxic agents such as radiocontrast dye, nonsteroidal anti-inflammatory drugs, and aminoglycosides; (3) more rigorous hypertension control and minimizing intradialytic hypotensive episodes; (4) individualizing the initial dialysis prescription with consideration of an incremental/infrequent approach to hemodialysis initiation (e.g., twice weekly) or peritoneal dialysis; and (5) considering a lower protein diet, especially on nondialysis days. Because RKF appears to be associated with better patient outcomes, it requires more clinical and research focus in the care of hemodialysis and peritoneal dialysis patients.

Incremental Hemodialysis, Residual Kidney Function, and Mortality Risk in Incident Dialysis Patients: A Cohort Study

BACKGROUND

Maintenance hemodialysis is typically prescribed thrice weekly irrespective of a patient's residual kidney function (RKF). We hypothesized that a less frequent schedule at hemodialysis therapy initiation is associated with greater preservation of RKF without compromising survival among patients with substantial RKF.

STUDY DESIGN

A longitudinal cohort.

SETTING & PARTICIPANTS

23,645 patients who initiated maintenance hemodialysis therapy in a large dialysis organization in the United States (January 2007 to December 2010), had available RKF data during the first 91 days (or quarter) of dialysis, and survived the first year.

PREDICTOR

Incremental (routine twice weekly for >6 continuous weeks during the first 91 days upon transition to dialysis) versus conventional (thrice weekly) hemodialysis regimens during the same time.

OUTCOMES

Changes in renal urea clearance and urine volume during 1 year after the first quarter and survival after the first year.

RESULTS

Among 23,645 included patients, 51% had substantial renal urea clearance (≥3.0mL/min/1.73m(2)) at baseline. Compared with 8,068 patients with conventional hemodialysis regimens matched based on baseline renal urea clearance, urine volume, age, sex, diabetes, and central venous catheter use, 351 patients with incremental regimens exhibited 16% (95% CI, 5%-28%) and 15% (95% CI, 2%-30%) more preserved renal urea clearance and urine volume at the second quarter, respectively, which persisted across the following quarters. Incremental regimens showed higher mortality risk in patients with inadequate baseline renal urea clearance (≤3.0mL/min/1.73m(2); HR, 1.61; 95% CI, 1.07-2.44), but not in those with higher baseline renal urea clearance (HR, 0.99; 95% CI, 0.76-1.28). Results were similar in a subgroup defined by baseline urine volume of 600mL/d.

LIMITATIONS

Potential selection bias and wide CIs.

CONCLUSIONS

Among incident hemodialysis patients with substantial RKF, incremental hemodialysis may be a safe treatment regimen and is associated with greater preservation of RKF, whereas higher mortality is observed after the first year of dialysis in those with the lowest RKF. Clinical trials are needed to examine the safety and effectiveness of twice-weekly hemodialysis.

Plasma Lipidomics Investigation of Hemodialysis Effects by Using Liquid Chromatography-Mass Spectrometry

Chronic kidney disease (CKD) has been a global health problem that has a great possibility of being developed into uremia in the end. Hemodialysis (HD) is the most commonly used strategy for treating uremic patients; however, the patients still have a high risk of suffering various complications. It is well recognized that lipid disorder usually occurs in maintenance HD patients. To systemically study the effects of HD on lipid metabolism associated with uremia, we employed an ultraperformance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS)-based lipidomics method. A total of 87 human plasma samples from patients with prehemodialysis (pre-HD)/posthemodialysis (post-HD) treatment and the healthy controls were enrolled in the study. As compared with pre-HD patients, many plasma lipids showed significant changes (p < 0.05) in patients receiving HD therapy. Specifically, sum of free fatty acids (FFA) as well as saturated FFA and eicosanoids and sums of lyso-phosphatidylinositols and lyso-phosphatidylethanolamines, FFA 16:1/FFA 16:0, and FFA 18:1/FFA 18:0 were obviously higher in the pre-HD group than in the controls while they were significantly lower in patients after HD. These results indicated that UPLC-Q-TOF/MS-based lipidomics is a promising approach to investigate lipid alterations in relation to uremia and it is helpful to understand complex complications involved in HD patients.

Estimating residual kidney function in dialysis patients without urine collection

Residual kidney function contributes substantially to solute clearance in dialysis patients but cannot be assessed without urine collection. We used serum filtration markers to develop dialysis-specific equations to estimate urinary urea clearance without the need for urine collection. In our development cohort, we measured 24-hour urine clearances under close supervision in 44 patients and validated these equations in 826 patients from the Netherlands Cooperative Study on the Adequacy of Dialysis. For the development and validation cohorts, median urinary urea clearance was 2.6 and 2.4 ml/min, respectively. During the 24-hour visit in the development cohort, serum β-trace protein concentrations remained in steady state but concentrations of all other markers increased. In the validation cohort, bias (median measured minus estimated clearance) was low for all equations. Precision was significantly better for β-trace protein and β2-microglobulin equations and the accuracy was significantly greater for β-trace protein, β2-microglobulin, and cystatin C equations, compared with the urea plus creatinine equation. Area under the receiver operator characteristic curve for detecting measured urinary urea clearance by equation-estimated urinary urea clearance (both 2 ml/min or more) were 0.821, 0.850, and 0.796 for β-trace protein, β2-microglobulin, and cystatin C equations, respectively; significantly greater than the 0.663 for the urea plus creatinine equation. Thus, residual renal function can be estimated in dialysis patients without urine collections.