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.

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.

Phosphate kinetic modeling as an estimate of daily ingested phosphate in hemodialysis patients with or without residual kidney function

BACKGROUND AND AIM

Daugirdas suggested a 2-pool phosphate kinetic model based on his previously established urea kinetic model. The current study aims to assess the level of agreement between the modeled daily ingested phosphorus (DIP) values and the routine method of dietary recall calculations in hemodialysis patients.

METHOD

The study was conducted on 100 hemodialysis patients; 50 were anuric, and the others had residual kidney function (RKF). The level of correlation and agreement between the dietary calculated and modeled DIP were assessed in both study groups.

RESULTS

A statistically significant positive correlation existed between the calculated and modeled DIP (r = 0.79 for the anuric group, r = 0.84 for the RKF group, p < 0.001). There was a significant level of agreement between calculated and modeled DIP in RKF patients only.

CONCLUSION

These findings suggest that phosphate modeling can estimate phosphate intake in RKF patients and be cost-effective in their management.

Validation of formulas calculating normalized protein catabolic rate in patients undergoing home hemodialysis

Depner and Daugirdas developed a simplified formula to estimate the normalized protein catabolic rate in patients on twice- or thrice-weekly hemodialysis (JASN, 1996). The aim of our work was to establish formulas in more frequent schedules and validate them in home-based hemodialysis patients. We realized that the structure of Depner and Daugirdas' normalized protein catabolic rate formulas has a general meaning and can be expressed as PCRn = C0/[a + b*(Kt/V) + c/(Kt/V)] + d, where C0 is pre-dialysis blood urea nitrogen, Kt/V is dialysis dose, a, b, c, d are the specific coefficients for each combination of home-based hemodialysis schedules and the day of blood sampling. The same applies to the formula that adjusts C0 (C'0) for residual kidney clearance of blood water urea (Kru) and urea distribution volume (V): C'0 = C0*[1 + (a1 + b1/(Kt/V))*Kru/V]. On this basis, we computed the six coefficients (a, b, c, d, a1, b1) for each of the 50 possible combinations and simulated a total of 24,000 weekly dialysis cycles using the Daugirdas Solute Solver software recommended by the KDOQI 2015 guidelines. From the associated statistical analyses we obtained 50 sets of coefficient values, which were validated comparing the paired normalized protein catabolic rate values (i.e., those estimated with our formulas with those modeled with Solute Solver) in 210 datasets of 27 patients on home-based hemodialysis. The mean values ± SD were 1.06 ± 0.262 and 1.07 ± 0.283 g/kg/day, respectively, with a mean difference of 0.004 ± 0.034 g/kg/day (p = 0.11). The paired values were highly correlated (R2 = 0.99). In conclusion, even if the coefficient values were validated in a relatively small sample of patients, they allow an accurate estimation of normalized protein catabolic rate in home-based hemodialysis patients.

Evaluation of Residual Kidney Function during Once-Weekly Incremental Hemodialysis

BACKGROUND

The initial once-weekly administration of incremental hemodialysis to patients with residual kidney function (RKF) has recently attracted considerable interest.

METHODS

The aim of our study was to assess the performance of a series of different methods in measuring serum urea nitrogen and serum Cr (sCr) RKF in patients on once-weekly hemodialysis (1WHD). Evaluations were carried out by means of 24-h predialysis urine collection (Kr-24H) or 6-day inter-dialysis collection (Kr-IDI) and estimation of glomerular filtration rate based on (KrSUN + KrsCr)/2 for the purpose of identifying a simple reference calculation to be used in assessing RKF in patients on 1WHD dialysis. Ninety-five urine samples were collected from 12 1WHD patients. A solute solver urea and Cr kinetic modeling program was used to calculate residual urea and Cr clearances. Mann-Whitney U test, Pearson's correlation coefficient (R), and linear determination coefficient (R2) were used for statistical analysis.

RESULTS

1WHD patients displayed a mean KrSUN-IDI of 4.5 ± 1.2 mL/min, while KrSUN-24H corresponded to 4.1 ± 0.9 mL/min, mean KrsCr-IDI to 9.1 ± 4.0 mL/min, and KrsCr 24H to 8.9 ± 4.2 mL/min, with a high regression between IDI and 24-h clearances (for IDI had R2 = 0.9149 and for 24H had R2 = 0.9595). A good correlation was also observed between KrSUN-24H and (KrSUN + KrsCR/2) (R2 = 0.7466, p < 0.01.

DISCUSSION

Urine collection over a 24-h predialysis period yielded similar results for both KrSUN and KrsCr compared to collection over a longer interdialytic interval (KrSUN + KrsCr)/2 could be applied to reliably assess RKF in patients on 1WHD.

CONCLUSION

The parameters evaluated are suitable for use as a routine daily method indicating the commencement and continued use of the 1WHD Incremental Program.

Equations to Estimate the Normalized Creatinine Generation Rate (CGRn) in 3/Week Dialysis Patients With or Without Residual Kidney Function

OBJECTIVE

Normalized creatinine generation rate (CGRn) can be computed for a variety of dialysis schedules using a recently described kinetic modeling program. However, the availability of estimating equations might facilitate broader study of this metric. We developed equations to estimate CGRn based on modeling and then tested them against modeled CGRn values in the Frequent Hemodialysis Network Nocturnal Trial baseline (3/week) dataset.

DESIGN AND METHODS

We used a "what-if" derivation of a previously published variable volume 2-pool creatinine kinetic model to generate predicted predialysis values of serum creatinine that would result from creatinine generation rates of 250-2000 mg/day in patients with creatinine distribution volumes of 20 to 50 L, dialyzed from 60 to 480 min per treatment three times a week. Then, in patients with residual kidney function, we calculated an "anuric expected predialysis serum creatinine value" before applying the same equations. We then compared estimated CGRn values as predicted by this approach with modeled values in patient data from the Frequent Hemodialysis Network Nocturnal Trial.

RESULTS

The estimating equations for CGRn yielded results similar to those obtained with formal modeling, in both anuric patients and those with residual kidney function, with mean percent error of 0.845 ± 6.15 (SD) in anuric patients, and ‒0.29 ± 4.90 in patients with a mean creatinine clearance of 5.44 ± 4.82 mL/min, with R-squared values of 0.96 in both anuric patients and those with residual renal clearance of creatinine.

CONCLUSIONS

In patients dialyzed 3/week, CGRn can be estimated using prediction equations. Use of these equations may facilitate broader investigation of CGRn as a measure of nutritional status and outcome.

Hemodialysis-Nutritional Flaws in Diagnosis and Prescriptions. Could Amino Acid Losses be the Sharpest "Sword of Damocles"?

This review aims to highlight the strengths and weaknesses emerging from diagnostic evaluations and prescriptions in an intent to prevent progression over time of malnutrition and/or protein-energy wasting (PEW) in hemodialysis (HD) patients. In particular, indications of the most effective pathway to follow in diagnosing a state of malnutrition are provided based on a range of appropriate chemical-clinical, anthropometric and instrumental analyses and monitoring of the nutritional status of HD patients. Finally, based on the findings of recent studies, therapeutic options to be adopted for the purpose of preventing or slowing down malnutrition have been reviewed, with particular focus on protein-calorie intake, the role of oral and/or intravenous supplements and efficacy of some classes of amino acids. A new determining factor that may lead inexorably to PEW in hemodialysis patients is represented by severe amino acid loss during hemodialysis sessions, for which mandatory compensation should be introduced.

Can incremental haemodialysis reduce early mortality rates in patients starting maintenance haemodialysis?

PURPOSE OF REVIEW

Early mortality rates after the start of maintenance haemodialysis therapy are high. Compared with three-times weekly haemodialysis, incremental haemodialysis is associated with better preservation of residual renal function (RRF) and at least equivalent mid-term to long-term survival. However, there is paucity of data in relation to its use as a means of helping patients through the transitional period, when they first become dialysis dependent.

RECENT FINDINGS

Studies of incremental haemodialysis have overlooked early mortality as an outcome measure. This is primarily due to their retrospective design which makes it difficult to link early deaths to the frequency of haemodialysis. New data confirm previous observations associating incremental haemodialysis with favourable outcomes. They also raise the possibility that in selected groups and for short periods, the pursuit of set clearance targets during the early days of dialysis may not necessarily bring additional short-term gains.

SUMMARY

We argue that, while simpler ways of estimating RRF are being explored, future trials must consider implementing incremental haemodialysis focusing on practical aspects of care in the transitional period; safety monitoring in such regimes should be undertaken using conventional methods. Such an approach is likely to benefit a larger subset of haemodialysis population.

Residual renal function in incremental dialysis

Incremental haemodialysis has the potential to allow better preservation of renal function, is less invasive to the patient and has lower cost. Despite these advantages, it is not commonly applied. This may be due to uncertainty about how to account for renal function in the prescription of dialysis and measurement of dose. In this issue, Vartia describes the practical basis for including the effect of renal function in the prescription and quantification of dialysis. He uses a well-known and validated urea kinetic model to calculate time average urea concentrations and the equivalent renal clearance (EKR) from dialysis. The effect of renal function is amplified by a weighting factor to account for the relatively greater effect of renal function compared with dialysis with the same urea clearance. In that way, patients on differing dialysis regimens can be dialysed with the same target dose. A further step would be to use a downward adjusting factor for dialysis to convert the urea clearance by dialysis (as EKR) to a glomerular filtration rate (GFR) equivalent. A factor of 0.75 is suggested. In that way, dialysis dose can be reported as GFR equivalent in mL/min/1.73 m2, comparable between different types of dialysis and also to renal function without dialysis.

A two-pool kinetic model predicts phosphate concentrations during and shortly following a conventional (three times weekly) hemodialysis session

Background

Previous studies have suggested that a conventional two-pool model cannot be used to predict intradialysis and early postdialysis phosphorus concentrations.

Methods

A conventional two-pool urea model was modified by increasing the distal compartment volume from two-thirds to three times the total body water and by the use of a dynamically variable intercompartmental phosphorus clearance during dialysis. The phosphate solver model parameters were derived from an examination of the results in the literature, and fine-tuned using a training set (F4) of 415 Hemodialysis (HEMO) Study patients studied during a dialysis session where phosphorus was measured at 4 months of follow-up. Validation was done in a group of 380 different HEMO Study patients plus 9 from the original F4 group, who were evaluated at 36 months of follow-up.

Results

The model predicted measured median early (1 h) intradialysis, end-dialysis and 30-min postdialysis serum phosphorus levels in the test and validation datasets with little apparent bias, including the highest and lowest deciles of predialysis serum phosphorus. The model tended to underestimate slightly intradialysis serum phosphorus when predialysis serum phosphorus was <3.0 mg/dL (0.97 mmol/L). There was a large scatter and standard deviation among patients, and whether aberrant values represent a patient-specific phenomenon is unclear.

Conclusions

A modified two-pool model using a slightly expanded distal compartment and a dynamically varying intercompartmental clearance, depending on the intradialysis phosphorus concentration, can be used to predict serum phosphorus level during and shortly after dialysis, in patients following a conventional three times per week dialysis prescription.

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.