Glucose polymer for ultrafiltration failure in CAPD

Protein Clearance and Icodextrin

Objective

To analyze the peritoneal transport of serum proteins during continuous ambulatory peritoneal dialysis (CAPD) with icodextrin.

Design

A comparison was made between CAPD with glucose-based dialysate and, in the same patients, 4 weeks after the instillation of icodextrin for the long night dwell, with icodextrin-based dialysate.

Patients

Ten stable CAPD patients, who participated in a large randomized multicenter study comparing icodextrin with glucose-based dialysate. Five patients used glucose 1.5% dialysate for the night dwell before its replacement by icodextrin (good ultrafiltration group), and 5 used glucose 4.25% (poor ultrafiltration group).

Results

The clearance of β2-microglobulin increased by 28% on icodextrin, due to increased convective transport. The clearances of the larger proteins -albumin, IgG, fibronectin, and α2-macroglobulin -remained unaltered, indicating transport of these proteins across the large pore system. The patients with poor ultrafiltration had a higher β2-microglobulin clearance on glucosebased dialysate than the high ultrafiltration group. This indicates that the ultrafiltration failure was caused by a large effective peritoneal surface area, leading to a rapid absorption of glucose. Icodextrin produced significantly more ultrafiltration in the poor ultrafiltration patients than in the high ultrafiltration group. A correlation was found for the β2-microglobulin clearance on glucose-based dialysate and the ultrafiltration produced by icodextrin.

Conclusions

Icodextrin causes ultrafiltration through the small pore system, whereas glucose-based dialysate has its effect on transcellular water transport. Therefore, the use of icodextrin causes an increased clearance of β2 microglobulin, but not of larger proteins. Icodextrin was especially useful in patients with a large effective surface area leading to ultrafiltration failure during treatment with glucose-based dialysate.

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.