Factors related to ultrafiltration volume with icodextrin dialysate use in children

BACKGROUND

Icodextrin has a lower absorption rate, and icodextrin peritoneal dialysate contributes to more water removal than glucose dialysate in patients with high peritoneal permeability. There are limited data on icodextrin dialysate use in children.

METHODS

This study included all pediatric patients who received peritoneal equilibration tests and peritoneal dialysis with icodextrin dialysate at the study center. The factors related to ultrafiltration volume with icodextrin dialysate with long dwell time were statistically analyzed. Then the ultrafiltration volume with icodextrin and medium-concentration glucose dialysate was compared in individual cycles in the same patients.

RESULTS

Thirty-six samples were included in the icodextrin group, and nine samples were used to compare the ultrafiltration volume with icodextrin and glucose dialysate. Dwell time, D/P-creatinine, D/D₀-glucose, age, height, and weight correlated significantly with the ultrafiltration volume of icodextrin dialysate (p < 0.05). A dwell volume equal to or more than 550 mL/m² was associated with a significantly higher ultrafiltration volume than a lower dwell volume (p = 0.039). Multiple regression analysis revealed that dwell time (p = 0.038) and height (p < 0.01) correlated with ultrafiltration volume significantly. In addition, the ultrafiltration volume was superior (p < 0.01), and dwell time was longer (p = 0.02), with icodextrin dialysate than with medium-concentration glucose dialysate.

CONCLUSIONS

The ultrafiltration volume with icodextrin dialysate decreases in patients with small stature. Providing sufficient dwell time and volume is important for maximal water removal even in children. Ultrafiltration volume is superior with icodextrin than medium-concentration glucose dialysate for long dwell times. A higher resolution version of the Graphical abstract is available as Supplementary information.

Effects of Conventional and New Peritoneal Dialysis Solutions on Human Peritoneal Mesothelial Cell Viability and Proliferation

Objective

To investigate the biocompatibility of “new” peritoneal dialysis (PD) solutions with bicarbonate/lactate buffer, non glucose osmotic agents (icodextrin or amino acids), neutral pH, and low levels of glucose degradation products (GDPs).

Design

Using M199 culture medium as a control, we compared conventional and new PD solutions with respect to their effects on the viability of human peritoneal mesothelial cells (HPMCs) [using lactate dehydrogenase (LDH) release], on DNA damage in HPMCs [using single-cell gel electrophoresis (Comet assay)], and on HPMC proliferation (using [3H]-thymidine incorporation). The experiments were performed after cell growth was synchronized by incubation with serum-free media for 24 hours. The PD solutions tested included commercial 1.5% glucose and 4.25% glucose solutions with 40 mmol/L lactate (D 1.5 and D 4.25, respectively), 7.5% icodextrin (E), 1.1% amino acid (N), 1.5% glucose solution in a triple-chambered bag (Bio 1.5), 1.5% glucose solution in a dual-chambered bag with neutral pH (Bal 1.5), and 1.5% glucose and 4.25% glucose solution containing 25 mmol/L bicarbonate and 15 mmol/L lactate (P 1.5 and P 4.25, respectively).

Results

When HPMCs were continuously exposed to undiluted PD solutions, D 1.5, D 4.25, P 4.25, and E increased LDH release by more than 60% at 24 hours. All PD solutions tested increased LDH release by more than 75% at 96 hours. With 2-fold diluted PD solutions, only D 4.25 significantly increased LDH release at 96 hours, though not at 24 hours. When cells were exposed to undiluted PD solutions for 60 min and allowed to recover in M199 for up to 96 hours, LDH release was significantly higher at 24 – 96 hours in E (55% – 69%) and D 1.5 (48% –72%) as compared with control [M199 (18%)]. Release of LDH was significantly lower with PD solutions containing lower levels of GDPs than those in D 1.5, suggesting that GDPs may have a role in cell viability. The D solutions (D 1.5 and D 4.25) and E solution also induced significant DNA damage. Both LDH release and DNA damage by D and E were significantly attenuated by adjusting the solution pH to 7.4, suggesting that low pH may be implicated in PD solution–induced DNA damage and cell death. When diluted 2-fold, D 1.5, D 4.25, and P 4.25 decreased [3H]-thymidine incorporation to 43%, 34%, and 41% of control, respectively, at 24 hours and to 45%, 26%, and 35% of control, respectively, at 96 hours. When cells were exposed to undiluted PD solutions for 5 minutes and allowed to recover in M199 for up to 96 hours, D 1.5 and P 4.25—but not D 4.25—significantly inhibited cell proliferation at 24 hours. This effect was sustained up to 96 hours.

Conclusions

The present in vitro data demonstrate that PD solutions with low pH, or high levels of GDPs, or both, promote HPMC death and DNA damage, and that PD solutions with high osmolality inhibit cell proliferation. Solutions with neutral pH, amino acids, and “low GDPs” appear to be more biocompatible than conventional PD solutions. These results require confirmation in in vivo animal and clinical studies.

Biocompatibility of New Peritoneal Dialysis Solutions: What Can We Hope to Achieve?

Despite the bioincompatibility of the “old”, standard, high glucose, lactate-buffered peritoneal dialysis (PD) solutions, PD is itself a highly successful dialysis modality with patient survival equivalent to that of hemodialysis (HD) during the initial 3 – 5 years of dialysis therapy. Nevertheless, PD technique survival is often limited by infectious complications and alterations in the structure and function of the peritoneal membrane. These local changes also have a negative impact on patient survival owing to systemic effects such as those often seen in patients with high peritoneal transport rate and loss of ultrafiltration (UF) capacity.

Patient mortality remains unacceptably high in both HD and PD patients, with most premature deaths being associated with signs of malnutrition, inflammation, and atherosclerotic cardiovascular disease (MIA syndrome). These systemic signs are likely to be influenced by PD solutions both directly and indirectly (via changes in the peritoneal membrane). New, biocompatible PD solutions may have favorable local effects (viability and function of the peritoneal membrane) and systemic effects (for example, on MIA syndrome). Amino acid–based solution [Nutrineal (N): Baxter Healthcare Corporation, Deerfield, IL, U.S.A.] may improve nutritional status as well as peritoneal membrane viability. Bicarbonate/lactate–buffered solution [Physioneal (P): Baxter Healthcare Corporation] may ameliorate local and systemic effects of low pH, high lactate, and high glucose degradation products. Icodextrin-based solution [Extraneal (E): Baxter Healthcare SA, Castlebar, Ireland] may improve hypertension and cardiovascular problems associated with fluid overload and may extend time on therapy in patients with loss of UF capacity.

The positive effects of each of these new, biocompatible solutions have been demonstrated in several studies. It is likely that the combined use of N, P, and E solutions will produce favorable synergies in regard to both local effects (peritoneal viability) and systemic effects (less malnutrition, inflammation, and fluid overload). Solution combination is an exciting area for clinical study in the coming years. Furthermore, dialysis fluid additives such as hyaluronan, which protects and improves the function of the peritoneal membrane, may further improve PD solutions. The new, biocompatible PD solutions represent an entirely new era in the evolution of the PD therapy; they are likely to have markedly positive effects on both PD technique and PD patient survival in coming years.

One-shot optimization of multiple enzyme parameters: Tailoring glucose oxidase for pH and electron mediators

Enzymes are biological catalysts with many industrial applications, but natural enzymes are usually unsuitable for industrial processes because they are not optimized for the process conditions. The properties of enzymes can be improved by directed evolution, which involves multiple rounds of mutagenesis and screening. By using mathematical models to predict the structure-activity relationship of an enzyme, and by defining the optimal combination of mutations in silico, we can significantly reduce the number of bench experiments needed, and hence the time and investment required to develop an optimized product. Here, we applied our innovative sequence-activity relationship methodology (innov'SAR) to improve glucose oxidase activity in the presence of different mediators across a range of pH values. Using this machine learning approach, a predictive model was developed and the optimal combination of mutations was determined, leading to a glucose oxidase mutant (P1) with greater specificity for the mediators ferrocene-methanol (12-fold) and nitrosoaniline (8-fold), compared to the wild-type enzyme, and better performance in three pH-adjusted buffers. The k_cat /K_M ratio of P1 increased by up to 121 folds compared to the wild type enzyme at pH 5.5 in the presence of ferrocene methanol.

The Role of Automated Peritoneal Dialysis in Peritoneal Dialysis Programme: One Centre Experience

The results of the Automated Peritoneal Dialysis (APD) therapy in adult patients in the Department of Nephrology in Gdansk during the years 1995–98 are presented. Seventeen patients (8-M, 9-F) aged 25–86 years (mean age 55.3 years), including 7 diabetics, were treated with different forms of APD. The most common indication for APD therapy was patients' loss of ability to perform Continuous Ambulatory Peritoneal Dialysis due to progressive blindness, leg amputation related to diabetic foot complications or cerebrovascular episodes (8 pts). The cumulative therapy period was 231.5 patient-months.

During the observation 4 patients died, 1 received kidney transplant and 12 were still treated with APD at the end of the study. No patient was transferred to long-term hemodialysis. The peritonitis rate in the APD group was 1/57.5 patient-months. Most patients reached adequacy targets, the mean Kt/V value was 1.97 (range 1.17 - 2.36). To achieve this, 12–19 litres of dialysate were used per day (mean 14.6 L/d). There were significant differences between CCPD and NPD groups with respect to dialysis adequacy, body weight and dialysis fluid volume. We conclude that APD may be used with success in patients in whom continuation of CAPD or HD therapy is very difficult due to its complications or comorbid conditions.

Intraperitoneal adhesions--an ongoing challenge between biomedical engineering and the life sciences

Peritoneal adhesions remain a relevant clinical problem despite the currently available prophylactic barrier materials. So far, the physical separation of traumatized serosa areas using barriers represents the most important clinical strategy for adhesion prevention. However, the optimal material has not yet been found. Further optimization or pharmacological functionalization of these barriers could give an innovative input for peritoneal adhesion prevention. Therefore, a more complete understanding of pathogenesis is required. On the basis of the pathophysiology of adhesion formation the main barriers currently in clinical practice as well as new innovations are discussed in the present review. Physiologically, mesothelial cells play a decisive role in providing a frictionless gliding surface on the serosa. Adhesion formation results from a cascade of events and is regulated by a variety of cellular and humoral factors. The main clinically applied strategy for adhesion prevention is based on the use of liquid or solid adhesion barriers to separate physically any denuded tissue. Both animal and human trials have not yet been able to identify the optimal barrier to prevent adhesion formation in a sustainable way. Therefore, further developments are required for effective prevention of postoperative adhesion formation. To reach this goal the combination of structural modification and pharmacological functionalization of barrier materials should be addressed. Achieving this aim requires the interaction between basic research, materials science and clinical expertise.

Icodextrin improves the serum potassium profile with the enhancement of nutritional status in continuous ambulatory peritoneal dialysis patients

The impact of glucose-free icodextrin (ID) for overnight dwell as compared to conventional glucose-containing dialysate (GD) on potassium (K⁺) metabolism in continuous ambulatory peritoneal dialysis (CAPD) patients has not yet been investigated. Serum K⁺ in a total of 255 stable patients (116 on GD and 139 on ID) on CAPD for more than 6 months and in 139 patients on ID before and after ID use (Pre-ID and Post-ID) were observed along with nutritional markers in a 2-year study period (Jan. 2006 to Dec. 2007). The prevalence of hypokalemia was similar between patients on GD and ID (16.7% vs 17.3%), but was lower on Post-ID than Pre-ID (17.3% vs 20.5%) without statistic significance. The mean serum K⁺ level was higher on ID than on GD (P<0.05) as well as Post-ID than Pre-ID (P<0.001). In the multivariate analysis, serum K⁺ levels were positively correlated with serum albumin, and creatinine in all patients (P<0.05), and ID-use in younger patients (age≤56, P<0.001). Serum albumin, creatinine, total CO₂, and body mass index were significantly higher on Post-ID than Pre-ID. Icodextrin dialysate for chronic overnight dwell could increase serum K⁺ levels and lower the prevalence of hypokalemia compared to conventional glucose-containing dialysate. The improved chronic K⁺ balance in CAPD patients on icodextrin could be related to enhanced nutritional status rather than its impact on acute intracellular K⁺ redistribution.

Endocrinology and Dialysis: Management of Lipid Abnormalities Associated with End-Stage Renal Disease

The management of lipid abnormalities in patients with end-stage renal disease (ESRD) remains controversial. Large, well-designed studies investigating the effects of dyslipidemia on cardiovascular (CV) morbidity and mortality and the role of cholesterol lowering drugs in reducing mortality in ESRD patients are lacking. While it seems reasonable to suspect that dyslipidemia and its treatment in ESRD patients will affect CV morbidity and mortality similar to that in the general population, recent studies have suggested that this may not be the case. Furthermore, the pharmacokinetics of lipid lowering drugs are altered in patients with ESRD and must be considered when treating this group of patients. This article reviews the major classes of drugs used to treat dyslipidemia, emphasizing their role in patients with ESRD.

Peritoneal clearance of homocysteine with icodextrin or standard glucose solution exchange

BACKGROUND

The aim of the study was to assess plasma homocysteine concentration in peritoneal dialysis patients, and to compare the effect of different peritoneal solutions (glucose-based and icodextrin-based) on peritoneal clearance of homocysteine.

METHODS

The study group comprised 10 chronic peritoneal dialysis patients; the control group comprised 15 healthy, age-matched non-obese subjects with normal renal function. Patients with vitamin B(12) or folate deficiency were excluded. In all subjects, plasma homocysteine and dialysis adequacy parameters were assessed at baseline. The clearance study was carried out with 2.27% glucose and 7.5% icodextrin solutions (12-h dwell time).

RESULTS

Mean dialysate concentration of homocysteine was similar for both glucose and icodextrin solutions (8.3 +/- 3.2 and 8.4 +/- 1.9 micromol/L, respectively), but homocysteine clearance was significantly higher for icodextrin than glucose solution (1.82 +/- 0.57 vs 1.39 +/- 0.53 mL/min per 1.73 m(2)P = 0.01). Net ultrafiltration after icodextrin solution was also higher than after glucose solution (599 +/- 136 mL vs 134 +/- 337 mL, P < 0.01). A correlation between total plasma level of homocysteine and its peritoneal clearance was found (r = 0.69; P = 0.03).

CONCLUSION

It appears that peritoneal elimination of homocysteine depends primarily on its plasma concentration. Icodextrin-based solution for peritoneal dialysis seems to be more efficient in homocysteine elimination than a standard glucose-based solution.

Icodextrin: a review of its use in peritoneal dialysis

Icodextrin (Extraneal) is a high molecular weight glucose polymer developed specifically for use as an alternative osmotic agent to dextrose during the once-daily long-dwell exchange in peritoneal dialysis (PD). Isosmotic 7.5% icodextrin solution induces transcapillary ultrafiltration (UF) by a mechanism resembling 'colloid' osmosis (unlike hyper-osmolar dextrose-based solutions, which induce UF by crystalline osmosis). In addition, absorption of icodextrin from the peritoneal cavity is relatively slow compared with that of dextrose; this results not only in UF of longer duration, but also a lower carbohydrate load compared with medium (2.5%) and strong (4.25%) dextrose exchanges. In randomised clinical trials of up to 2 years in duration, administration of icodextrin for the long (8- to 16-hour) overnight exchange in continuous ambulatory peritoneal dialysis (CAPD) or daytime exchange in automated peritoneal dialysis (APD) produced net UF which exceeded that with 1.5% and 2.5% dextrose solutions (thereby improving fluid balance), and was equivalent to that with 4.25% dextrose solution. Icodextrin also increased peritoneal clearances of creatinine and urea nitrogen compared with 2.5% dextrose solution. The increase in UF volume with icodextrin was enhanced in CAPD patients with high peritoneal membrane permeability (i.e. high and high-average transporters), maintained in the small number of patients followed-up for 2 years and sustained during episodes of peritonitis. Icodextrin reduced the percentage of patients with net negative UF in contrast to 1.5% and 2.5% dextrose and, in noncomparative studies, extended PD technique survival in patients who had failed dextrose-based dialysis. The use of icodextrin was also associated with some symptomatic improvements and health-related quality of life advantages, and no adverse effect on patient survival, compared with dextrose, although confirmation of these findings is ideally required in appropriately designed studies. The tolerability of icodextrin was generally similar to that of dextrose-based solutions in controlled clinical trials, although there was an approximate three-fold increase in the risk of new skin rash (5.5% vs 1.7%). However, reports of severe cutaneous hypersensitivity reactions remain rare; this possibility should not preclude the use of the polymer.

CONCLUSION

7.5% icodextrin solution offers the first feasible alternative to conventional dextrose solutions for the once-daily long-dwell exchange in PD. It is effective, generally well tolerated and appears to be most useful in situations of reduced or inadequate UF with dextrose, including in high and high-average transporters, during episodes of peritonitis and patients who have failed dextrose-based dialysis.

Nutritional effects of increasing dialysis dose by adding an icodextrin daytime dwell to Nocturnal Intermittent Peritoneal Dialysis (NIPD) in children

BACKGROUND

To assess the need to adapt dietary prescriptions, we studied potential effects of increasing the dialysis dose by adding a daytime icodextrin dwell, in children on Nocturnal Intermittent Peritoneal Dialysis (NIPD), on peritoneal amino acids (AA) and albumin loss, AA, albumin, cholesterol and fibrinogen plasma levels and nutritional intake.

METHODS

A cross-over study in eight children (age 2-12 years) on NIPD at baseline (week 1).

INTERVENTION

to increase dialysis dose we added a daytime dwell with 1100 ml/m(2) icodextrin solution for a week (week 2).

MAIN OUTCOME MEASURES

peritoneal albumin loss (quantified by nephelometry) and AA loss (quantified by liquid chromatography mass spectrometry) in the last 72 h dialysate collections of weeks 1 and 2. On days 7 and 14, morning blood sample was taken for urea, creatinine, plasma AA levels, serum albumin, cholesterol and fibrinogen determination. Nutritional intake diaries were kept throughout the study period.

RESULTS

Weekly dialysis creatinine clearance increased from 35 to 65 l/1.73 m(2) (P<0.0001) and Kt/V from 1.99 to 2.54 (P<0.01). Peritoneal albumin loss did not change significantly (2.4+/-0.4 to 2.4+/-0.3 g/m(2)/24 h) nor did serum albumin (3.25+/-0.52 to 3.21+/-0.25 g/dl), cholesterol (216+/-73 to 240+/-61 mg/dl) and fibrinogen (385+/-40 to 436+/-64 mg/dl). There was a significant increase in loss of essential (EAA) [1122+/-200 to 2104+/-417 mg/m(2)/week (P<0.0001)] and non-essential amino acids (NEAA) [6160+/-1341 to 10406+/-2899 mg/m(2)/week (P<0.001)]. Plasma AA levels did not change significantly except for a drop in histidine and glutamine. Dietary protein intake did not change from 43+/-12 to 41+/-8 g/m(2)/day, caloric intake from 73+/-21 to 70+/-24 kcal/kg/day.

CONCLUSIONS

Increasing dialysis dose by introducing a daytime icodextrin dwell during a week does not affect peritoneal albumin loss, serum albumin, cholesterol and fibrinogen levels nor dietary intake on a short term. There is a significant increase in EAA and NEAA loss without change in plasma levels. We suggest monitoring dietary intake when adding a daytime icodextrin dwell in children.

Icodextrin-induced lipid peroxidation disrupts the mesothelial cell cycle engine

Fluids commonly used for peritoneal dialysis hold poor biocompatibility vis a vis the peritoneal membrane, basically due to the presence of osmotic agents. When rat mesothelium was exposed to glucose-enriched dialysis solutions for 2 h in vivo, an early and short-lived acceleration of cell life cycle was observed, which, after 30 d of exposure, resulted in a depopulated monolayer of senescent cells. These changes appear to result from persistent oxidative stress due to continuous exposure to high concentration of glucose and to substances generated by the Maillard reaction. Long-term exposure (30 d) of the peritoneal mesothelium to 7.5% icodextrin resulted in a depopulated monolayer consisting mostly of senescent cells, which, additionally, showed atypical nuclear changes and atypical mitosis suggesting DNA damage. These changes coincided with substantial lipid peroxidation, starting immediately after the introduction of the icodextrin solution into the rat's abdominal cavity. So far, the currently used osmotic agents in peritoneal dialysis fluids induce substantial oxidative injury to the exposed monolayer in vivo. Use of high concentrations of glucose results in premature senescence of the exposed cell population. The 7.5% icodextrin dialysis fluid induces through lipid peroxidation substantial genomic damage, which, in turn, sets the biological mechanisms leading to protective cellular suicide in motion.