Improved urea reduction ratio and Kt/V in large hemodialysis patients using two dialyzers in parallel

Successful hemodialysis treatment of a Quarter Horse mare with silver maple leaf toxicity and acute kidney injury

An adult American Quarter Horse mare presented for pigmenturia and lethargy of 12 hours' duration and was diagnosed with silver maple leaf toxicity. The mare had intravascular hemolysis and azotemia. The mare was treated with a transfusion of whole blood, fluids administered IV, antibiotics, oxygen insufflation, and supportive care. The azotemia persisted despite conventional medical management and hemodialysis was elected. After 2 intermittent hemodialysis treatments over 3 days, the azotemia almost resolved, clinical signs improved, and the mare was discharged. The blood urea nitrogen, creatinine, and electrolyte concentrations remained normal 6 months later after examination by the referring veterinarian. Hemodialysis treatment can be feasible in horses if equipment and expertise are available and should be considered as a treatment option if indicated.

Reporting of "dialysis adequacy" as an outcome in randomised trials conducted in adults on haemodialysis

Background

Clinical trials are most informative for evidence-based decision-making when they consistently measure and report outcomes of relevance to stakeholders, especially patients, clinicians, and policy makers. However, sometimes terminology used is interpreted differently by different stakeholders, which might lead to confusion during shared decision making. The construct dialysis adequacy is frequently used, suggesting it is an important outcome both for health care professionals as for patients.

Objective

To assess the scope and consistency of the construct dialysis adequacy as reported in randomised controlled trials in hemodialysis, and evaluate whether these align to the insights and understanding of this construct by patients.

Methods

To assess scope and consistency of dialysis adequacy by professionals, we performed a systematic review searching the Cochrane Central Register of Controlled Trials (CENTRAL) up to July 2017. We identified all randomised controlled trails (RCT) including patients on hemodialysis and reporting dialysis adequacy, adequacy or adequacy of dialysis and extracted and classified all reported outcomes. To explore interpretation and meaning of the construct of adequacy by patients, we conducted 11 semi-structured interviews with HD patients using thematic analysis. Belgian registration number B670201731001.

Findings

From the 31 included trials, we extracted and classified 98 outcome measures defined by the authors as adequacy of dialysis, of which 94 (95%) were biochemical, 3 (3%) non-biochemical surrogate and 2 (2%) patient-relevant. The three most commonly reported measures were all biochemical. None of the studies defined adequacy of dialysis as a patient relevant outcome such as survival or quality of life. Patients had a substantially different understanding of the construct dialysis adequacy than the biochemical interpretation reported in the literature. Being alive, time spent while being on dialysis, fatigue and friendliness of staff were the most prominent themes that patients linked to the construct of dialysis adequacy.

Conclusion

Adequacy of dialysis as reported in the literature refers to biochemical outcome measures, most of which are not related with patient relevant outcomes. For patients, adequate dialysis is a dialysis that enables them to spend as much quality time in their life as possible.

Extracorporeal Treatment in the Management of Acute Poisoning: What an Intensivist Should Know?

Extracorporeal treatment (ECTR) represents a treatment modality promoting removal of endogenous or exogenous poisons and supporting or temporarily replacing a vital organ. This article aims to provide a brief overview of the technical aspects and the potential indications and limitations of the different ECTRs, highlighting the important characteristics of poison amenable to ECTR and the most appropriate prescriptions used in the setting of acute poisoning. The various principles that govern poison elimination by ECTR (diffusion, convection, adsorption, and centrifugation) and how components of the ECTR can be adjusted to maximize clearance have also being discussed.

Diffusive Clearance of Small and Middle-Sized Molecules in Combined Dialyzer Flow Configurations

Clearance of low (LMW) and middle molecular weight (MMW) solutes was investigated in vitro for different dialyzer configurations and mutual flow directions. Single pass tests were performed with two low flux Fresenius F6HPS hemodialyzers placed in series (12 tests) and in parallel (6 tests), and results were compared with those for one single dialyzer (2 tests). Either high concentrated (45mS/cm) bicarbonate dialysis fluid (surrogate LMW) or trisodiumphosphate (surrogate MMW) concentration (31mS/cm) was used as blood substitution fluid. Standard blood and dialysate flows of 250 and 500ml/min, respectively, were prescribed. Clearance was derived from conductivity measurements in blood and dialysate compartment, correcting for the overall ultrafiltration rate of 0.1–0.5l/h. In a single dialyzer, changing the counter current flow to co-current deteriorates diffusive clearance by 14% (LMW) and 18% (MMW). Compared to one single dialyzer using counter current flow, clearance increases by 3 to 8% (LMW) and by 15 to 18% (MMW) using two dialyzers in parallel and in series, respectively. As a consequence, the benefit by using a second dialyzer is more prominent for larger molecules. Moreover, pressure profiles drawn for the different configurations show the impact of limited convection on diffusive clearance.

The Impact of Kt/V Urea-Based Dialysis Adequacy on Quality of Life and Adherence in Haemodialysis Patients: A Cross-Sectional Study in Greece

There is clear evidence of a link between dialysis adequacy (as measured by urea kinetic modeling or urea reduction ratio) and such important clinical outcomes as morbidity and mortality. Evidence regarding the relationship between dialysis adequacy and quality of life (QOL) outcomes as well as adherence is less clear. The present paper is a study protocol which is planning to answer the following research question: what is the impact of dialysis adequacy on QOL and adherence in a sample of hemodialysis patients? The final sample size will be around 100 patients undergoing hemodialysis. Each subject’s QOL and adherence will be measured using the following instruments: i) the Missoula-VITAS quality of life index 25; ii) the multidimensional scale of perceived social support and iii) the simplified medication adherence questionnaire. Dialysis adequacy is expected to be related to QOL and adherence scores.

Principles and operational parameters to optimize poison removal with extracorporeal treatments

A role for nephrologists in the management of a poisoned patient involves evaluating the indications for, and methods of, enhancing the elimination of a poison. Nephrologists are familiar with the various extracorporeal treatments (ECTRs) used in the management of impaired kidney function, and their respective advantages and disadvantages. However, these same skills and knowledge may not always be considered, or applicable, when prescribing ECTR for the treatment of a poisoned patient. Maximizing solute elimination is a key aim of such treatments, perhaps more so than in the treatment of uremia, because ECTR has the potential to reverse clinical toxicity and shorten the duration of poisoning. This manuscript reviews the various principles that govern poison elimination by ECTR (diffusion, convection, adsorption, and centrifugation) and how components of the ECTR can be adjusted to maximize clearance. Data supporting these recommendations will be presented, whenever available.

Determination of the relationship between adequacy of dialysis and quality of life and self-care agency

AIM AND OBJECTIVES

To investigate the relationship between the dialysis adequacy and the quality of life and self-care agency.

BACKGROUND

Haemodialysis (HD), which is the leading treatment option for chronic renal failure (CRF), leads to significant changes in the life of the patient. These changes affecting almost all the dimensions of life also negatively affect the quality of life and self-care agency.

DESIGN

Descriptive study.

METHODS

The research was conducted with a total of 112 patients who had been admitted to two private dialysis centres between May 2009 and September 2010, who met the research criteria. The Data Collection Form for the Socio-demographic and Medical Characteristics, the Biochemical and Medical Parameters Form to determine the adequacy of dialysis, the SF-36 Quality of Life Scale and the Self-Care Agency Scale were used in the research.

RESULTS

A significant relationship was found between Kt/V, one of the parameters used for the assessment of dialysis adequacy, and the emotional role scores of the SF-36 Quality of Life Scale and between the URR level and physical functioning (r = +0.192, p = 0.045) and emotional role scores (r = +0.284, p = 0.003). No significant relationship could be found between the self-care agency and the evaluated parameters.

CONCLUSIONS

Kt/V and URR, which have an effect on dialysis adequacy, may affect the quality of life. Our results are similar to those of previous studies, which showed that Kt/V and URR affect the quality of life.

RELEVANCE TO CLINICAL PRACTICE

It was recommended to regularly control the parameters used for the assessment of dialysis adequacy and to evaluate their effects on the quality of life, to determine the most affected quality of life subparameters and to address these problems and solve them.

The effect of increasing dialysis dose in overweight hemodialysis patients on quality of life: a 6-week randomized crossover trial

BACKGROUND

Using standard hemodialysis regimens, overweight patients often do not reach Kidney Disease Outcomes Quality Initiatives (KDOQI) Kt/V targets, and this has been associated with lower health-related quality of life (HRQL). Whether increasing dialysis adequacy in large patients not achieving KDOQI targets improves HRQL is unknown.

STUDY DESIGN

Randomized blinded crossover study.

SETTING & PARTICIPANTS

Overweight (>80 kg) underdialyzed patients from 6 dialysis units in 2 Canadian dialysis programs.

INTERVENTIONS

Six-week treatment periods with a standard dialysis regimen (4 hours 3 times weekly) and 3 augmented regimens: 4.5 hours of hemodialysis, 4 hours of hemodialysis with increased dialysate flow, and 4 hours of hemodialysis with 2 dialyzers in parallel.

OUTCOMES & MEASUREMENTS

The End-Stage Renal Disease Symptom domain of the Kidney Disease Quality-of-Life Short-Form questionnaire (primary outcome) and the Health Utilities Index Mark 2 (secondary outcome).

RESULTS

We enrolled 18 patients (mean weight, 109.7 +/- 16.2 [SD] kg); 12 completed all 4 regimens. Mean Kt/Vs during the study were 1.27 (95% confidence interval [CI], 1.19 to 1.35), 1.41 (95% CI, 1.32 to 1.50), 1.31 (95% CI, 1.22 to 1.39), and 1.41 (95% CI, 1.33 to 1.49) for patients receiving standard dialysis, 4.5 hours of hemodialysis, hemodialysis with increased dialysate flow, and hemodialysis with 2 dialyzers, respectively. Kidney Disease Quality-of-Life End-Stage Renal Disease Symptom domain and Health Utilities Index Mark 2 scores were 75.9 (95% CI, 70.7 to 81.2) and 0.69 (95% CI, 0.56 to 0.81) for patients receiving standard dialysis, respectively. These did not differ when patients received the 3 augmented dialysis regimens (P = 0.2 and P = 0.5, respectively).

LIMITATIONS

Small sample size and inability to fully blind patients to the treatment they were receiving.

CONCLUSION

Improving hemodialysis adequacy for large underdialyzed patients did not lead to improved HRQL. Our findings suggest that augmentation of the dialysis regimen is not required for these patients in the absence of overt uremic symptoms.

Clinical evaluation of dual-dialyzer hemodialysis (DDHD)

A higher beta(2)-microglobulin (beta(2)MG) removal rate is possible in dual-dialyzer hemodialysis (DDHD) because of the large internal filtration provided. In this treatment, in the first dialyzer, a large amount of water moves from the blood side to the dialysate side, and in the second dialyzer, it moves from the dialysate side to the blood side. Thus, both the direction of the water shift and the amount of water change within the dialyzer from the blood inlet port to the outlet port. A blood volume monitor was used to confirm that the internal filtration rate remains stable during the course of the dialysis treatment. The beta(2)MG removal rate and the weekly amount of solute removal by DDHD treatment was much higher than that for conventional HD.

Improving hollow fiber dialyzer efficiency with a recirculating dialysate system II: comparison against two-chamber dialysis systems

The theoretical basis of the nonregenerated recirculating dialysate system (RDS) was derived in Part I of this work [M. Prado, L. M. Roa, A. Palma, and J. A. Milán, Ann. Biomed. Eng. (2005)]. This system pursues the maximization of the clearance of hollow fiber dialyzers whose performance is controlled by diffusion, as occurred in standard hemodialysis. In this second part we perform a comparison by digital simulation of the RDS against three well-known two-chamber dialysis systems. As a major outcome, the efficiency of the RDS increased by a factor of five-eight with respect to the efficiency of a single dialyzer operating with a number of transfer units equal to 0.1, that is when the diffusive mass-transfer of the dialyzer is exhausted. Present low-flux dialyzers do not take advantage of the full potential of this technique, but the functional domain where high-flux and high-area dialyzers operate could be more suitable to exploit this technique. We conclude that RDS can be a competitive efficient technique for optimizing the dialysis efficiency.

Middle molecule removal in low-flux polysulfone dialyzers: Impact of flows and surface area on whole-body and dialyzer clearances

Some studies found that the removal of middle molecules has a long-term effect on mortality and, even more, is enhanced by high-flux dialysis. In order to enhance middle molecule removal in a low-flux dialyzer, the present study aimed at investigating the combined impact of dialyzer flows and membrane surface area. Blood and dialysate flows were varied within the clinical range 300-500 and 500-800 mL/min, respectively, while the ultrafiltration rate was kept constant at 0.1 L/hr. Single-pass tests were performed in vitro in a single Fresenius F6HPS dialyzer (3 tests) and serially (5 tests) and parallel (3 tests) connected dialyzers. The blood substitution fluid consisted of dialysis fluid in which radioactive-labeled vitamin B12 (molecular weight 1355 Da) was dissolved. Dialyzer clearance as well as whole-body clearance was calculated from radioactivity concentrations of samples taken from the inlet and outlet bloodline. Adding a second dialyzer in series or parallel ameliorated the overall dialyzer and whole-body clearance significantly, except for the highest applied blood flows of 500 mL/min. Better solute removal was also obtained with higher dialysate flows, while the use of higher blood flows seemed advantageous only when using a single dialyzer. Analysis of the ultrafiltration profiles in the different configurations illustrated that enhancing the internal filtration rate ameliorates convective transport of middle molecules. Adequate solute removal results from a number of interactions, as there are blood and dialysate flows, membrane surface area, filtration profile and concentration profiles in the blood and dialysate compartment.

Tandem dialyzers with two monitors to meet target KT/V

This preliminary trial was conducted to verify the impact upon delivered KT/V, the percentage change in the urea reduction ratio (%URR), and the frequency of meeting prescribed targets of these parameters of a novel method of combining two dialyzers in series with two monitors in patients with a large body mass or suboptimal vascular access performance. Double dialyzers in parallel are in regular use at our center. Tandem use of dialyzers in series with a single hemodialysis monitor was frustrated by frequent technical difficulties (transmembrane pressure reversal and excessive ultra filtration). We developed a technique of using double dialyzers in series to overcome these technical difficulties with two monitors and limiting all of the ultrafiltration to the second dialyzer. Three patients with A-V grafts and two with catheters had five treatments each with single dialyzers, double dialyzers in parallel, and double dialyzers in series with two monitors after a washout period encompassing the first two sessions in each configuration. Treatment times were set to process exactly 85 L of blood in patients with A-V grafts and 60 L in patients with catheters. The dosages of heparin and ultrafiltration goals were unchanged during the study. In patients with A-V grafts, mean KT/V increased from 1.15 with single dialyzers to 1.35 with double parallel (p < 0.02) and 1.48 with tandem (p < 0.001) dialyzers. %URR (mean) increased from 61.82 for single to 68.32 for double parallel (p < 0.05) and 71.38 (p < 0.001) for tandem dialyzers. Tandem dialyzers with two monitors achieved insignificantly greater %URR and KT/V compared with double parallel dialyzers. The frequency of meeting targets for KT/V improved with double parallel and tandem configurations (p < 0.001). Tandem dialyzers were more frequently successful in delivering target KT/V (p < 0.05) and target %URR (p < 0.001) than double parallel dialyzers. In patients with catheters, neither configuration of double dialyzers succeeded in improving %URR, KT/V, or the frequency with which targets for these parameters were met. Our method of using tandem dialyzers with two monitors is more frequently successful than double parallel dialyzers in enhancing delivered KT/V and %URR in patients with A-V grafts but not catheters as dialysis access.

A comparison of dual dialyzers in parallel and series to improve urea clearance in large hemodialysis patients

BACKGROUND

Dialysis adequacy targets frequently are difficult to achieve in large hemodialysis patients. Dual dialyzers can be used to improve clearance. It is unknown whether series or parallel configurations are superior.

METHODS

Eighteen large hemodialysis patients (mean weight, 92.4 kg) were enrolled in a randomized, crossover trial to directly compare dual dialyzers in parallel and series configurations. Treatment times, blood flow rates, and dialysate flow rates were kept constant.

RESULTS

Compared with a single dialyzer, parallel dual dialyzers increased the single-pool Kt/V (spKt/V) from 1.25 +/- 0.22 to 1.43 +/- 0.29 (P < 0.003). Series dual dialyzers improved urea clearance measured by spKt/V (spKt/V(urea)) to 1.46 +/- 0.26 (P < 0.0003 compared with a single dialyzer). Kt/V and urea reduction ratio of dual dialyzers in parallel were not significantly different from those of dual dialyzers in series. Half the subjects failed to meet the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative recommended adequacy target for spKt/V(urea) of 1.2 or less using a single dialyzer. With the use of dual dialyzers, 83% of subjects achieved this adequacy target. Serum levels of a middle molecule, beta2-microglobulin, were reduced 34% after 2 months of dual-dialyzer therapy. Cost analysis estimates annual net savings of 1,260 dollars with dual-dialyzer therapy, primarily from projected savings in inpatient expenses.

CONCLUSION

In large hemodialysis patients, our study shows that dual dialyzers in parallel and series are equally effective at improving urea clearance without prolonging dialysis treatment times.

Dialysis adequacy and health related quality of life in hemodialysis patients

Patients with end-stage renal disease have significant impairments in health related quality of life (HRQOL). The determinants of HRQOL, including the effect of dialysis adequacy, have not been well studied. This study was designed to investigate whether dialysis adequacy is associated with HRQOL in hemodialysis patients. A cross-sectional survey of 128 patients who had been on hemodialysis for more than 6 months was conducted. Baseline information on demographic factors and detailed clinical information was collected. Average Kt/V levels (for the 3 months preceding HRQOL assessment) were determined. HRQOL was assessed with the Kidney Disease Quality of Life Short Form, the Short Form-36 (SF-36), and the EuroQol EQ-5D. Multiple linear regression was performed to control for differences in important baseline covariates. Patients with average Kt/V levels greater than or equal to 1.3 had better HRQOL as measured by significantly higher scores (p < 0.05) in 4 of 11 kidney disease targeted domains, 6 of 8 SF-36 domains, and on the EQ-5D visual analog scale and index score. Using multiple linear regression to control for important covariates, the adjusted EQ-5D index score was higher by 0.036 (95% confidence intervals 0.015, 0.057) for each 0.1 increment in Kt/V, which is both statistically and clinically significant. Dialysis adequacy was significantly associated with HRQOL in hemodialysis patients. Controlled studies that examine the effect of increasing Kt/V on HRQOL are needed.

Phosphorus Clearance Using Two Hemodialyzers Placed in Parallel

Control of hyperphosphatemia is a major goal in patients with end-stage renal disease. However, removal of retained inorganic phosphorus during hemodialysis remains a major problem. We compared clearances and total phosphate removal in large patients treated with two F-80 dialyzers (Fresenius Medical Care of North America, Lexington, MA, U.S.A.) placed in parallel, and small patients dialyzed with a single F-80 dialyzer (SD). Clearances were obtained using total dialysate collections. Eight dialysate collections (5 patients) using double parallel dialyzers (DD group) were compared with 5 dialysate collections (4 patients) using single dialyzers (SD group). Blood and dialysate flow rates and time of dialysis treatment were identical between the groups. The DD group's Kt/V _urea was 1.46 ± 0.13; SD group's Kt/V _urea was 1.35 ± 0.09 (p = 0.2). Absolute phosphorus removal was 1594 ± 300 mg for the DD group, compared to 1108 ± 285 mg in the SD group (p = 0.03). Urea clearance in the DD group was 285 ± 25 mL/minute and 251 ± 27 mL/ min in the SD group (p = 0.082). Phosphorus clearance was 178 ± 32 mL/min in the DD group and 149 ± 38 mL/min in the SD group (p = 0.039). There was no correlation between phosphorus clearance and dialyzer reuse. The bulk of phosphorus removal was achieved during the first 2 hours of hemodialysis. This finding is consistent with the hypothesis that there are at least two pools of body phosphorus. Using hemodialyzers placed in parallel led to higher phosphate clearance and total phosphorus removal. This higher phosphate removal may be related in part to increasing the concentration gradient for transfer out of a second compartment.

HEMO equilibrated Kt/V goals are difficult to achieve in large male patients

The long-term outcome of chronic hemodialysis patients is influenced by the adequacy of dialysis treatment. A major objective of the ongoing US HEMO Study is to determine if a higher target value of treatment as measured by the equilibrated Kt/V (eKt/V), a calculation of dialysis adequacy developed for the study, of 1.45 results in a better outcome than the presently accepted target value for eKt/V of 1.05 (approximately equal to spKt/V of 1.2). eKt/V corrects for urea rebound and gives a better estimate of actual treatment received. To examine the feasibility of achieving the higher eKt/V in large hemodialysis patients, a retrospective analysis of 389 monthly eKt/V values from 65 men on chronic hemodialysis of larger than average size dialyzed at high blood and dialysate flows (QB 400, QD 800 ml/min) with large dialyzers (1.8-2.2 m2) for longer than 4 hours three times weekly was performed. A total of 278 treatments considered optimal by a blood water urea clearance estimate were included in the final analyses. The mean body weight and Chertow water volume were 84.3+/-16.5 kgm and 50.0+/-6.7 L, respectively. The mean sp Kt/V was 1.29+/-0.17. The mean eKt/V was 1.16+/-0.14 and was inversely correlated with weight and water volume (p < 0.0001). Despite the large dialyzers and high blood and dialysate flow rates, no patient weighing more than 80 kgm or with body water volume exceeding 46 liters achieved an eKt/V of 1.45. This study suggests that creative dialyses will be required to achieve the HEMO "high arm" target in large patients.