The Biology of the Mesothelium during Peritoneal Dialysis

Substantial derangements of mesothelial biology are observed during experimental simulations of dialysis conditions, inferred from the content of human dialysis effluent and visualized by microscopy of human mesothelial biopsies. Canosmotically active solutions be made biocompatible with the osmoregulatory system of the mesothelium? Can the contributions of the mesothelium to host defenses against inflammation and/or infection be supported during CAPD? Do underlying metabolic derangements present in various kidney diseases and end-stage renal disease, regardless of cause, require customized CAPD protocols and solutions? Use of dialysis solutions less directly toxic to the mesothelium is a necessary step toward some day manipulating peritoneal biology by pharmacological and therapeutic modalities.

A new peritoneal dialysis fluid for Japanese patients: a randomized non-inferiority clinical trial of safety and efficacy

BACKGROUND

We report here two new peritoneal dialysis fluids (PDFs) for Japan [BLR 250, BLR 350 (Baxter Limited, Japan)]. The PDFs use two-chamber systems, and have bicarbonate and lactate buffer to a total of 35 mmol/L. In separate trials, the new PDFs were compared to two "standard" systems [PD-4, PD-2 (Baxter Limited, Japan)]. The trials aimed to demonstrate non-inferiority of peritoneal creatinine clearance (pCcr), peritoneal urea clearance (pCurea) and ultrafiltration volume (UF), and compare acid-base and electrolyte balance.

METHODS

We performed randomized, multicenter, parallel group, controlled, open-label clinical trials in stable continuous ambulatory peritoneal dialysis (CAPD) patients. The primary endpoints were pCcr and UF. The secondary endpoints were serum bicarbonate and peritoneal urea clearance. The active phase was 8 weeks. These trials were performed as non-inferiority studies, with the lower limit of non-inferiority for pCcr and UF set at 3.2 L/week/1.73 m² and 0.12 L/day, respectively.

RESULTS

108 patients (28 centers) and 103 patients (29 centers) took part in the two trials. Groups were well balanced at baseline. The investigative PDFs were non-inferior to the "standard" ones in terms of primary endpoints, comparable in terms of pCurea, and superior in terms acid-base balance, especially correcting those with over-alkalinization at baseline.

CONCLUSIONS

We demonstrated fundamental functionality of two new PDFs and showed superior acid-base balance. Given the propensity of Japanese CAPD patients for alkalosis, it is important to avoid metabolic alkalosis which is associated with increased cardiovascular mortality risk and accelerated vascular calcification. The new PDFs are important progress of CAPD treatment for Japanese patients.

In vitro effects of glucose polymer-containing peritoneal dialysis fluids on phagocytic activity

Commercially available peritoneal dialysis fluids (PDFs) are known to impair peritoneal cellular defense mechanisms. We have investigated the influence of glucose polymer-containing PDFs on phagocytic function in vitro. Polymorphonuclear neutrophils (PMNLs) and monocytes (MNs) from 10 continuous ambulatory peritoneal dialysis patients and 10 healthy donors were incubated in PDFs containing either 7.5% icodextrin (glucose polymer) or 1.5% glucose at original pH and pH 7.4. Chemiluminescence response and H202 production were measured following stimulation with preopsonized Staphylococcus epidermidis or phorbol myristate acetate. Phagocytosis of radiolabeled bacteria and killing capacity of the cells were determined. A comparison of the impact of glucose polymer versus glucose-containing solutions at their original pH on the oxidative metabolism of the cells showed a highly significant difference (P < 0.0001) in favor of glucose polymers for H202 production of PMNLs (7.78 +/- 4.5 nmol cytochrome C reduction/10(6) cells/min v 1.11 +/- 0.67 nmol cytochrome C reduction/10(6) cells/min) and MNs (7.66 +/- 3.6 nmol cytochrome C reduction/10(6) cells/min v 1.29 +/- 0.86 nmol cytochrome C reduction/10(6)cells/min). Correspondingly, PMNLs and MNs incubated in glucose polymers showed a significantly higher chemiluminescence response irrespective of the stimulant used (P < 0.0001). Applying the killing assay on PMNLs also revealed a significantly higher percentage of inactivated bacteria (45.5% +/- 11.0% v 29.2% +/- 15.5%; P < 0.05). After adjustment of pH to 7.4, a significant difference could only be found for H202 production of PMNLs in favor of glucose polymers (16.73 +/- 6.98 nmol cytochrome C reduction/10(6) cells/min v 11.65 +/- 5.37 nmol cytochrome C reduction/10(6) cells/min; P < 0.05). In addition, we compared the glucose-polymer solution to an otherwise equally composed equiosmolar solution that contained 0.274% glucose instead of glucose polymers. No significant differences were detected with any of the tests applied. Our data suggest that glucose polymer solutions are comparatively less suppressive to phagocytic function than currently used glucose-containing PDFs. This effect may be attributed to the low osmolarity of these solutions.