Icodextrin Simplifies PD Therapy by Equalizing UF and Sodium Removal Among Patient Transport Types During Long Dwells: A Modeling Study

Can one long peritoneal dwell with icodextrin replace two short dwells with glucose?

Background

Due to the slower dissipation of the osmotic gradient, icodextrin-based solutions, compared to glucose-based solutions, can improve water removal. We investigated scenarios where one icodextrin-based long dwell (Extraneal) replaced two glucose-based exchanges.

Methods

The three-pore model with icodextrin hydrolysis was used for numerical simulations of a single exchange to investigate the impact of different peritoneal dialysis schedules on fluid and solute removal in patients with different peritoneal solute transfer rates (PSTRs). We evaluated water removal (ultrafiltration, UF), absorbed mass of glucose (AbsGluc) and carbohydrates (AbsCHO, for glucose and glucose polymers), ultrafiltration efficiency (UFE = UF/AbsCHO) per exchange, and specified dwell time, and removed solute mass for sodium (ReNa), urea (ReU), and creatinine (ReCr) for a single peritoneal exchange with 7.5% icodextrin (Extraneal®) and glucose-based solutions (1.36% and 2.27%) and various dwell durations in patients with fast and average PSTRs.

Results

Introducing 7.5% icodextrin for the long dwell to replace one of three or four glucose-based exchanges per day leads to increased fluid and solute removal and higher UF efficiency for studied transport groups. Replacing two glucose-based exchanges with one icodextrin exchange provides higher or similar water removal and higher daily sodium removal but slightly lower daily removal of urea and creatinine, irrespective of the transport type present in the case of reference prescription with three and four daily exchanges.

Conclusion

One 7.5% icodextrin can replace two glucose solutions. Unlike glucose-based solutions, it resulted only in minor differences between PSTR groups in terms of water and solute removal with UFE remaining stable up to 16 h.

Peritoneal dialysis fluids

There have been significant advances in the understanding of peritoneal dialysis (PD) in the last 40 years, and uptake of PD as a modality of kidney replacement therapy is increasing worldwide. PD fluids, therefore, remains the lifeline for patients on this treatment. Developing these fluids to be efficacious in solute clearance and ultrafiltration, with minimal adverse consequences to peritoneal membrane health and systemic effects is a key requirement. Since the first PD fluid produced in 1959, modifications to PD fluids have been made. Nonetheless, the search for that ideal PD fluid remains elusive. Understanding the components of PD fluids is a key aspect of optimizing the successful delivery of PD, allowing for individualized PD prescription. Glucose remains an integral component of PD fluids; however, its deleterious effects continue to be the impetus for the search of an alternative osmotic agent, and icodextrin remains the main alternative. More biocompatible PD fluids have been developed and have shown benefits in preserving residual kidney function. However, high cost and reduced accessibility remain deterrents to its widespread clinical use in many countries. Large-scale clinical trials are necessary and very much awaited to improve the narrow spectrum of PD fluids available for clinical use.

Modelling of icodextrin hydrolysis and kinetics during peritoneal dialysis

In peritoneal dialysis, ultrafiltration is achieved by adding an osmotic agent into the dialysis fluid. During an exchange with icodextrin-based solution, polysaccharide chains are degraded by α-amylase activity in dialysate, influencing its osmotic properties. We modelled water and solute removal taking into account degradation by α-amylase and absorption of icodextrin from the peritoneal cavity. Data from 16 h dwells with icodextrin-based solution in 11 patients (3 icodextrin-exposed, 8 icodextrin-naïve at the start of the study) on dialysate volume, dialysate concentrations of glucose, urea, creatinine and α-amylase, and dialysate and blood concentrations of seven molecular weight fractions of icodextrin were analysed. The three-pore model was extended to describe hydrolysis of icodextrin by α-amylase. The extended model accurately predicted kinetics of ultrafiltration, small solutes and icodextrin fractions in dialysate, indicating differences in degradation kinetics between icodextrin-naïve and icodextrin-exposed patients. In addition, the model provided information on the patterns of icodextrin degradation caused by α-amylase. Modelling of icodextrin kinetics using an extended three-pore model that takes into account absorption of icodextrin and changes in α-amylase activity in the dialysate provided accurate description of peritoneal transport and information on patterns of icodextrin hydrolysis during long icodextrin dwells.

Research hotspots and emerging trends of automated peritoneal dialysis: A bibliometric analysis from 2000 to 2020

BACKGROUND

The implementation of automated peritoneal dialysis (APD) has considerably increased in many countries. We conducted a bibliometric analysis to evaluate the accumulating studies on APD in the last two decades quantitatively and qualitatively.

METHODS

Publications regarding APD research between 2000 and 2020 were retrieved from the Web of Science Core Collection database by using the index term "automated peritoneal dialysis." CiteSpace, VOSviewer, and an online platform were employed to analyze the number of publications and the collaboration relationships between countries, institutions, authors, and co-cited journals. Cluster analysis and burst keywords detection were performed on co-cited references and keywords, respectively.

RESULTS

We obtained a record of 545 publications related to APD in total. The United States was the country that contributes most, and Baxter Healthcare Corporation was the leading institution. Peritoneal Dialysis International was the most active journals in this field. Claudio Ranco was the most productive author, and Simon J Davies ranked the first in the cited authors. Co-cited reference cluster analysis and high frequency keywords showed that survival, ultrafiltration and peritonitis are continuous hot topics. While remote monitoring (RM) and telemedicine may be APD research frontiers according to burst keywords detection.

CONCLUSION

This bibliometric study provides comprehensive overview on the publications of APD over the past two decades. These findings help to identify the hotspots and explore new directions for future research. RM has become an emerging trend in APD field.

The prognosis and risk factors of baseline high peritoneal transporters on patients with peritoneal dialysis

The relationship between baseline high peritoneal solute transport rate (PSTR) and the prognosis of peritoneal dialysis (PD) patients remains unclear. The present study combined clinical data and basic experiments to investigate the impact of baseline PSTR and the underlying molecular mechanisms. A total of 204 incident CAPD patients from four PD centres in Shanghai between 1 January 2014 and 30 September 2020 were grouped based on a peritoneal equilibration test after the first month of dialysis. Analysed with multivariate Cox and logistic regression models, baseline high PSTR was a significant risk factor for technique failure (AHR 5.70; 95% CI 1.581 to 20.548 p = 0.008). Baseline hyperuricemia was an independent predictor of mortality (AHR 1.006 95%CI 1.003 to 1.008, p < 0.001) and baseline high PSTR (AOR 1.007; 95%CI 1.003 to 1.012; p = 0.020). Since uric acid was closely related to high PSTR and adverse prognosis, the in vitro experiments were performed to explore the underlying mechanisms of which uric acid affected peritoneum. We found hyperuricemia induced epithelial‐to‐mesenchymal transition (EMT) of cultured human peritoneal mesothelial cells by activating TGF‐β1/Smad3 signalling pathway and nuclear transcription factors. Conclusively, high baseline PSTR induced by hyperuricaemia through EMT was an important reason of poor outcomes in CAPD patients.

Icodextrin Is Associated with a Lower Mortality Rate in Peritoneal Dialysis Patients

Background:Icodextrin (ICO) improves fluid removal in peritoneal dialysis (PD) patients. However, whether physiological benefits of ICO translate into patient survival remains unclear. We examine the association of ICO and clinical outcomes.Methods:We identified patients who initiated long-term PD from the National Health Insurance Research Database of Taiwan. We matched ICO users with non-users according to propensity score and survival status when ICO was prescribed. We utilized time-dependent analyses to avoid immortal time bias. Additional competing risk models were utilized for the outcomes except for death. The outcomes of interest were time to death, technique failure, peritonitis, major adverse cardiovascular events (MACE), and hospitalization.Results:A total of 4,914 PD patients were enrolled and 2,836 PD patients (57.7%) were identified as ICO users. The ICO users had significantly better overall survival (hazard ratio [HR] 0.74; 95% confidence interval [CI] 0.63 - 0.86), especially among early ICO users (HR 0.64; 95% CI 0.54 - 0.77, p value for interaction: 0.007). The ICO users were associated with higher risk of peritonitis (subdistribution HR 1.22, 95% CI 1.06 - 1.14) and hospitalization (subdistribution HR 1.14, 95% CI 1.05 - 1.24), considering competing risk of death. However, when considering ICO use as a time-varying covariate, ICO users shared similar risks for technique failure, peritonitis, MACE, and hospitalization as non-users. The effect of ICO on mortality was especially prominent among those early users.Conclusions:After adjustments for immortal time biases, ICO users were significantly associated with approximately 20% reduction in mortality, especially among early users.

Single Daily Icodextrin Exchange as Initial and Solitary Therapy

Background

Incremental dialysis utilizes gradually increasing dialysis doses in response to declines in residual kidney function, and it is the preferred renal replacement therapy for patients who have just transitioned to end-stage renal disease (ESRD). Incremental peritoneal dialysis (PD) may impose fewer restrictions on patients’ lifestyle, help attenuate lifetime peritoneal and systemic exposure to glucose and its degradation products, and minimize connections that could compromise the sterile fluid path. In this study, we utilized a 3-pore kinetic model to assess fluid and solute removal during single daily icodextrin treatments for patients with varying glomerular filtration rates (GFR).

Methods

Single icodextrin exchanges of 8 to 16 hours using 2- and 2.5-L bag volumes were simulated for different patient transport types (i.e., high to low) to predict daily peritoneal ultrafiltration (UF), daily peritoneal sodium removal, and weekly total (peritoneal + residual kidney) Kt/V (Kt/VTotal) for patients with residual renal GFRs ranging from 0 to 15 mL/min/1.73 m2.

Results

Daily peritoneal UF varied from 359 to 607 mL, and daily peritoneal Na removal varied from 52 to 87 mEq depending on length of icodextrin exchange and bag volume. Both were effectively independent of patient transport type. All but very large patients (total body water [TBW] > 60 L) were predicted to achieve adequate dialysis (Kt/VTot al ≥ 1.7) with a GFR of 10 mL/min/1.73 m2, and small patients (TBW: 30 L) were predicted to achieve adequate dialysis with a GFR of 6 mL/min/1.73 m2.

Conclusions

A single daily icodextrin exchange can be tailored to augment urea, UF, and Na removal in patients with sufficient residual kidney function (RKF). A solitary icodextrin exchange may therefore be reasonable initial therapy for some incident ESRD patients.

Kinetic Modeling of Incremental Ambulatory Peritoneal Dialysis Exchanges

Background

Incremental peritoneal dialysis (PD), the gradual introduction of dialysate exchanges at less than full-dose therapy, has been infrequently described in clinical reports. One concern with less than full-dose dialysis is whether urea clearance targets are achievable with an incremental regimen. In this report, we used a large database of PD patients, across all membrane transport types, and performed urea kinetic modeling determinations of possible incremental regimens for an individual membrane type.

Methods

Using a modified 3-pore model of peritoneal transport, various incremental manual continuous ambulatory PD (CAPD) exchanges employing glucose and/or icodextrin were evaluated. Peritoneal urea clearances from those simulations were added to residual kidney urea clearance for patients with various glomerular filtration rates (GFRs), and the total weekly urea clearance was then compared to the total weekly urea Kt/V target of 1.7. All 4 peritoneal membrane types were modeled. For each simulated prescription, net ultrafiltration and carbohydrate absorption were also calculated.

Results

Incremental CAPD regimens of 2 exchanges a day met adequacy targets if the GFR was 6 mL/min/1.73 m2 in all membrane types. For regimens employing 3 exchanges a day, Kt/V targets were achieved at GFR levels of 4 to 5 mL/min/1.73 m2 in high transporters to low transporters but higher tonicity 2.5% glucose solutions or icodextrin were required in some regimens.

Conclusions

This work demonstrates that with incremental CAPD regimens, urea kinetic targets are achievable in most new starts to PD with residual kidney function. Incremental PD may be a less intrusive, better accepted initial treatment regime and a cost-effective way to initiate chronic dialysis in the incident patient. The key role of intrinsic kidney function in incremental regimens is highlighted in this analysis and would warrant conscientious monitoring.

Evaluating Hyponatremia in Non-Diabetic Uremic Patients on Peritoneal Dialysis

♦

BACKGROUND

An approach to hyponatremia in uremic patients on peritoneal dialysis (PD) necessitates the assessment of intracellular fluid volume (ICV) and extracellular volume (ECV). The aim of the study was to evaluate the association of plasma sodium (Na(+)) concentration and body fluid composition and identify the causes of hyponatremia in non-diabetic PD patients. ♦

METHODS

Sixty non-diabetic uremic patients on PD were enrolled. Baseline body fluid composition, biochemistry, hand-grip test, peritoneal membrane characteristics, dialysis adequacy, Na(+) and water balance, and residual renal function (RRF) were measured. These parameters were reevaluated for those who developed hyponatremia, defined as serum Na(+) concentration < 132 mmol/L and a decline in serum Na(+) > 7 mmol/L, during monthly visits for 1 year. Body fluid composition was determined by multi-frequency bioelectrical impedance (BIA). ♦

RESULTS

There was no significant correlation between serum Na(+) concentrations and any other parameters except a negative correction with overnight ultrafiltration (UF) amount (p = 0.02). The ICV/ECV ratio was positively correlated with serum albumin (p < 0.005) and hand grip strength (p < 0.05). Over 1 year, 9 patients (M:F = 3:6, aged 35 - 77) with 4 different etiologies of hyponatremia were identified. Hyponatremic patients with a body weight (BW) loss had either an increased ICV/ECV ratio associated with primarily a negative Na(+) balance (n = 2) or a reduced ratio of ICV/ECV associated with malnutrition (n = 2). In contrast, hyponatremic patients with a BW gain had either a reduced ICV/ECV ratio associated with a rapid loss of RRF and a higher peritoneal permeability (n = 2) or a normal to increased ICV/ECV ratio associated with high water intake (n = 3). ♦

CONCLUSION

Besides BW change and ultrafiltration rate, the assessment of ICV/ECV ratio is valuable in identifying the etiologies of hyponatremia in PD and provides a guide for optimal therapy.

Volume-Based Peritoneal Dialysis Prescription Guide to Achieve Adequacy Targets

♦

BACKGROUND

The use of automated and continuous ambulatory peritoneal dialysis (APD and CAPD) prescriptions (Rxs) to achieve adequate uremic toxin and fluid removal targets is important for attaining optimal patient outcomes. One approach for predicting such Rxs is the use of kinetic modeling. ♦

METHODS

Demographic data and peritoneal membrane characteristics derived from a peritoneal equilibration test (PET) were available from 1,005 patients in North American centers who participated in a national adequacy initiative in 1999. Twelve patient subgroups were identified according to peritoneal membrane transport type and tertiles of total body water, assumed equal to urea distribution volume (Vurea). Each patient was then modeled using PD Adequest 2.0 to be treated by 12 CAPD and 34 APD Rxs using both glucose and icodextrin solutions to achieve adequacy targets of weekly urea Kt/V of 1.7 and 1 L of daily ultrafiltration (UF). Residual kidney function (RKF) was assumed to be 0, 2, 4, and 6 mL/min. Feasible peritoneal dialysis (PD) Rxs were identified where: 1) the 95% confidence limit achieved the goal of meeting the targets for urea Kt/V, daily UF, and both in 85%, 75%, and 70% of patients, respectively; 2) average PD solution dextrose concentration was < 2.5%; and 3) the number of daytime exchanges was minimized. ♦

RESULTS

Feasible PD Rxs were similar when RKF was ≥ 2 mL/min, allowing condensed recommendations based on RKF ≥ 2 mL/min or < 2 mL/min. Individuals with lower or slower membrane transport required relatively greater 24-h solution volumes to achieve adequacy targets when RKF fell below 2 mL/min. With increasing Vurea, there was disproportionately greater dependence on RKF to achieve targets. While multiple Rxs achieving urea Kt/V and daily UF goals were identified for all membrane transport types, use of icodextrin in the long dwell reduced the need for a midday exchange in APD, glucose exposure, required fill and 24-h dwell volumes, irrespective of RKF and Vurea. While these benefits were most notable in high and high-average transporters, similar results were also seen in low and low-average transporters. ♦

CONCLUSIONS

Kinetic modeling identified multiple APD and CAPD Rxs that achieved adequate uremic solute and fluid removal for patients, irrespective of RKF and Vurea. Use of icodextrin rather than glucose in the long dwell reduced the complexity of the PD regimen, total glucose exposure, and 24-h total treatment solution volumes. Irrespective of modeling, adequacy of any PD prescription should be based upon individual clinical evaluation both for volume and solute removal.