Newer peritoneal dialysis solutions

Maltose, a promising osmotic agent in peritoneal dialysis solution

Peritoneal dialysis has undergone considerable development from a technological point of view, and osmotic agent has played the essential role in peritoneal dialysis fluid. Because the most commonly used osmotic agent is glucose and icodextrin, there are some disadvantages related to the use of glucose-based solutions and icodextrin. So it is urgent to develop a new peritoneal dialysis osmotic agent. According to these characteristics of glucose and icodextrin, it is promising to explore a better osmotic agent of peritoneal dialysis solution which is able to allow maintenance of the maximum ultrafiltration gradient, and prevent toxicity or accumulation of unwanted substances in the blood, being non-toxic or less-toxic, furthermore the metabolite should not cause significant metabolic disturbance. Maltose may be one of promising osmotic agent and may put an important influence on development of peritoneal dialysis.

Citrate supplementation of PD fluid: effects on net ultrafiltration and clearance of small solutes in single dwells

BACKGROUND

Inflammatory reactions affect the general performance as well as the technique survival of peritoneal dialysis (PD). Anti-inflammatory additives like heparin and sodium citrate have shown favourable results in these respects. The present study is the first to evaluate citrate-supplemented PD fluids (PDFs) in humans.

METHODS

Crossover design was used to evaluate sodium citrate and heparin-supplemented Gambrosol Trio (2.5% glucose) in 28 stable outpatients from the PD unit. Comparisons were made between single dwells of each fluid. Citrate supplementation at 5 mM/L was compared with standard PDF, and citrate supplementation at 10 mM/L was compared with low-molecular-weight heparin (4500 units of tinzaparin) supplementation and standard PDF. The initial osmolarity of the fluids was equalized by adding sodium chloride.

RESULTS

Citrate supplementation at 5 mM/L significantly increased net ultrafiltration, measured as drained volume gain, by 126 mL. Creatinine and phosphate clearance, but not glucose clearance, was significantly improved by supplementation with citrate or heparin. Heparin supplementation created an insignificant trend towards an increased ultrafiltration (P = 0.08). No negative side effects were reported for any of the treatments; however, citrate supplementation led to a small calcium loss by the drained PD fluid (0.4 mmol) and a transient fall in the plasma concentration (0.04 mM/L) of free calcium ions at 5 mM/L citrate. Effects on plasma bicarbonate concentration were insignificant.

CONCLUSIONS

Citrate supplementation of PD fluid improved ultrafiltration and clearance of small solutes with only minor effects on calcium turnover. The mechanism is unknown and, according to the results, not related to complement inhibition.

Editorials: Will Peritoneal Dialysis be Left Behind?

Peritoneal dialysis (PD) enjoyed huge growth in the 1980s, followed by a rapid decline in the late 1990s, and a now persistently low utilization rate in many countries, including the United States. Recent clinical data indicate a survival advantage for patients started on PD. Residual renal function is better preserved with PD. Adequacy targets are being revised and will likely allow PD prescriptions to be simplified. The physiology of the peritoneum is better understood and treatment strategies reflect that understanding. New solutions have been developed in response to studies that have assessed the impact of conventional PD dialysate on the structure and function of the peritoneum. A remaining challenge is to ensure that nephrology trainees and nephrologists in practice are fully informed of the advantages of PD for many patients and of the advances in the therapy. If this can be achieved, PD should start to grow again.

In vitro biocompatibility performance of Physioneal

In vitro biocompatibility performance of Physioneal. toneal dialysis (PD) has been a successful and effective form of chronic renal replacement therapy since its introduction over 20 years ago. Despite its overall success, there is a growing body of evidence that suggests shortcomings in the preservation of membrane integrity. This has led to the development of several second-generation PD solutions that demonstrate improved biocompatibility. Physioneal, a neutral pH, bicarbonate/lactate-buffered solution, was one of the first of these new PD solutions to become commercially available. This review will focus on one of the first preclinical stages in the development of Physioneal: studies on in vitro biocompatibility testing. Studies in leukocyte, mesothelial cell, and fibroblast populations demonstrated significantly improved biocompatibility of neutral pH, bicarbonate/lactate-based solutions compared to conventional solutions. The solutions contributed to improved leukocyte viability and response to bacterial infection (e.g., phagocytosis, superoxide radical generation, and endotoxin-stimulated cytokine release). Studies on peritoneal mesothelial cells demonstrate improved cell viability, proliferation, and response to proinflammatory stimuli, and a reduced potential for angiogenesis and peritoneal fibrosis, all suggesting a better preservation of membrane structure and function. The bicarbonate/lactate-based solutions demonstrated decreased cytotoxicity and preserved cell growth in fibroblast cultures as well. In vitro biocompatibility testing has clearly demonstrated that neutral pH, bicarbonate/lactate-buffered Physioneal solutions are superior to conventional solutions in preserving cell viability and function in cell populations that contribute to peritoneal homeostasis. This positive assessment now provides a foundation and rationale for moving forward with the next stages in preclinical testing: in vivo animal models and human ex vivo studies.

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.

Development of a formulation that enhances gene expression and efficacy following intraperitoneal administration in rabbits and mice

We conducted a series of experiments to determine if intraperitoneal (IP) delivery of recombinant adenovirus (rAd)-based therapies is improved through carrier vehicle selection, and compared an icodextrin solution (a high molecular weight dextrin with a prolonged peritoneal cavity residence time) with a standardized phosphate buffered saline (PBS) delivery solution. In vitro, comparative adenovirus particle concentration determination (27 h) and bioactivity assay (24h) indicated equivalent compatibility with icodextrin or PBS. In vivo, rabbits treated IP (100 ml) with rAd-betagal 1 x 10(9) P/ml in icodextrin showed improved transgene expression throughout the peritoneal wall compared to rAd-betagal in PBS. In PC-3 tumor-bearing mice treated IP with 5 x 10(9) P/0.5 ml or 1 x 10(10) P/0.5 ml rAd-betagal, transgene expression was significantly enhanced (p < 0.01) with icodextrin compared to PBS in both tumor specimens and peritoneal wall. In subsequent studies we compared prolongation of survival in intraperitoneal PC-3 and MDAH-2774 human xenograft tumor models in nude mice using rAd-p53 in icodextrin or PBS in multi-dose ranging (1 x 10(8) to 1 x 10(10) P) experiments. The icodextrin formulation alone significantly increased rAd-p53 mediated survival (p < 0.05). In animals, these results show that IP rAd gene therapy can be improved with the use of icodextrin, and suggest that prolonged retention and distribution in the peritoneal cavity is an important factor.

Peritoneal ultrafiltration for chronic congestive heart failure: rationale, evidence and future

Peritoneal dialysis (PD) was the first dialytic therapy used to achieve euvolemia in individuals with refractory congestive heart failure. PD remains a viable therapy for the short-term management of refractory congestive heart failure, and fluid removal rates comparable to those obtained with the continuous extracorporeal therapies can be achieved. However, with advances in extracorporeal therapies, the role of PD in these situations is limited to those individuals in whom vascular access cannot be obtained or if extracorporeal therapies are not available. On the other hand, PD is the ultrafiltration therapy of choice for the long-term ambulatory management of individuals with refractory congestive heart failure, either as a palliative therapy or as a bridge to definitive surgery or transplantation. A reduction in hospitalization rates and an improvement in functional capacity can be expected under such circumstances; however, survival is unlikely to be affected.