Does the biocompatibility of the peritoneal dialysis solution matter in assessment of peritoneal function?

BACKGROUND: Peritoneal function tests are performed in peritoneal dialysis (PD) patients to characterize peritoneal membrane status. A low pH/high glucose degradation product (GDP) dialysis solution is used as the test solution. The objective of the present study was to compare a 3.86% glucose, low pH/high GDP dialysis solution (pH 5.5) with a 3.86% glucose, normal pH/low GDP dialysis solution (pH 7.4) in assessments of peritoneal membrane function. METHODS: Two standard peritoneal permeability analyses (SPA) were performed in 10 stable PD patients within 2 weeks. One SPA was done with the 3.86% low pH/high GDP solution, and the other with the 3.86% normal pH/low GDP solution. The sequence of the two tests was randomized. RESULTS: Fluid transport parameters and glucose absorption were not different between the two groups. No differences were found for the mass transfer area coefficients (MTACs) of low molecular weight solutes calculated over the whole dwell. However, MTAC urea in the first hour of the dwell was higher in the test done with low pH/high GDP dialysate, suggesting more peritoneal vasodilation. No difference was found in protein clearances. Sodium sieving at multiple time points during the dwell was similar with the two solutions. CONCLUSION: The results obtained with the glucose-containing normal pH/low GDP dialysis solution were similar to those obtained with the glucose-containing low pH/high GDP dialysate in assessments of peritoneal membrane function.

Peritoneal function and assessment of reference values using a 3.86% glucose solution.

BACKGROUND: The most widely used peritoneal function test, the peritoneal equilibration test (PET), is performed with a 2.27% glucose solution. Recently, the International Society for Peritoneal Dialysis committee on ultrafiltration failure (UFF) advised performing the test with 3.86% glucose solution because it is more sensitive for detecting clinically significant UFF. Because no reference values for this test were available, we analyzed the results of standard peritoneal permeability analyses (SPAs) using 3.86% glucose. METHODS: The tests were performed in our center on 154 clinically stable peritoneal dialysis (PD) patients that were free of peritonitis for at least 4 weeks. For the assessment of reference values, we used two approaches. In approach A, patients with UFF, defined as net ultrafiltration (UF) < 400 mL/4 hours, were excluded. In approach B, only patients within their first 2 years of PD treatment were included, regardless of net UF. Means and 95% confidence intervals (95% CI) were calculated for the transport parameters of the PET and SPA. RESULTS: Means of normal distribution with 95% CI in approach A were as follows: for 2.0-L exchanges, mass transfer area coefficient (MTAC) for creatinine 8.8 mL/minute (4.7 - 12.7 mL/min), dialysate/plasma ratio (D/P) creatinine 0.70 (0.52 - 0.88), glucose absorption 58% (44% - 72%), dialysate240/initial dialysate ratio of glucose (Dt/D0) 0.28 (0.18- 0.38), net UF 675 mL (375 - 975 mL), and maximal dip in D/P sodium after correction for diffusion from the circulation 0.110 (0.050 - 0.164); for 1.5-L exchanges, MTAC creatinine 7.4 mL/min (3.8 - 11.0 mL/min), D/P creatinine 0.69 (0.52 - 0.86), glucose absorption 62% (52% - 72%), Dt/D0 glucose 0.25 (0.17- 0.32), net UF 551 mL (430 - 670 mL), and maximal dip D/P sodium 0.120 (0.048 - 0.166). In approach B, most of the transport values were similar; however, values for lymphatic absorption were significantly higher [1.52 mL/min (2-L) and 1.40 mL/min (1.5-L), p < 0.01] and values for the maximum dip in D/P sodium were lower [0.101 (2-L) and 0.112 (1.5-L), p > 0.05]. This was probably the result of including patients with UFF in approach B, since these parameters can be causative factors of UFF. CONCLUSIONS: A peritoneal transport function test using 3.86% glucose provides data on various aspects of transport. This study gives normal reference values that can be used for analysis of causes of UFF.

Analysis of the prevalence and causes of ultrafiltration failure during long-term peritoneal dialysis: a cross-sectional study.

BACKGROUND: Ultrafiltration failure (UFF) is a major complication of peritoneal dialysis (PD). It can occur at any stage of PD, but develops in time and is, therefore, especially important in long-term treatment. To investigate its prevalence and to identify possible causes, we performed a multicenter study in The Netherlands, where patients treated with PD for more than 4 years were studied using a peritoneal function test (standard peritoneal permeability analysis) with 3.86% glucose. UFF was defined as net UF < 400 mL after a 4-hour dwell. RESULTS: 55 patients unselected for the presence or absence of UFF were analyzed. Mean age was 48 years (range 18 - 74 years); duration of PD ranged from 48 to 144 months (median 61 months); UFF was present in 20 patients (36%). Patients with and without UFF did not differ in age or duration of PD. Median values for patients with normal UF compared to patients with UFF were, for net UF 659 mL versus 120 mL (p < 0.01), transcapillary UF rate 3.8 versus 2.1 mL/ minute (p < 0.01), effective lymphatic absorption 1.0 versus 1.6 mL/min (p < 0.05), mass transfer area coefficient (MTAC) for creatinine 9.0 versus 12.9 mL/min (p< 0.01), dialysate-to-plasma ratio (D/P) for creatinine 0.71 versus 0.86 (p < 0.01), glucose absorption 60% versus 73% (p < 0.01), maximum dip in D/P sodium (as a measure of free water transport) 0.109 versus 0.032 (p < 0.01), and osmotic conductance to glucose 3.0 versus 2.1 microL/min/mmHg (p < 0.05). As causes for UFF, high MTAC creatinine, defined as > 12.5 mL/min, or a glucose absorption > 72%, both reflecting a large vascular surface, a lymphatic absorption rate (LAR) of > 2.14 mL/min, and a decreased dip in D/P sodium of < 0.046 were identified. Most patients had a combination of causes (12 patients), whereas there was only a decreased dip in D/P sodium in 3 patients, only high MTAC creatinine in 1 patient, and only high LAR in 2 patients. We could not identify a cause in 2 patients. Both groups had similar clearances of serum proteins and peritoneal restriction coefficients. However, dialysate cancer antigen 125 concentrations, reflecting mesothelial cell mass, were lower in the UFF patients (2.79 vs 5.38 U/L). CONCLUSION: The prevalence of UFF is high in long-term PD. It is caused mainly by a large vascular surface area and by impaired channel-mediated water transport. In addition, these patients also had signs of a reduced mesothelial cell mass, indicating damage of the peritoneum on both vascular and mesothelial sites.

Free-water transport in fast transport status: a comparison between CAPD peritonitis and long-term PD.

BACKGROUND: Ultrafiltration failure (UFF) in continuous ambulatory peritoneal dialysis (CAPD) is a transient phenomenon during acute peritonitis and a permanent complication in long-term peritoneal dialysis (PD). The high solute transport rates during acute peritonitis are probably caused by an increased number of perfused peritoneal capillaries. Long-term PD is associated with an increased number of peritoneal microvessels, leading to an enlargement of the anatomic vascular surface area. This leads to high mass transfer area coefficients (MTAC) and to UFF. Impaired conductance to glucose, leading to a reduction in free-water transport, may be a contributing factor to UFF in long-term PD. We hypothesized that UFF during acute peritonitis is, in the absence of permanent structural changes, only caused by an increased vascular surface area, while in long-term patients it is often the result of an increased surface area in combination with an impaired conductance to glucose. Therefore, the peritoneal transport parameters of patients with acute peritonitis were compared to those in long-term PD patients. METHODS: A standard peritoneal permeability analysis (SPA) was done in 10 PD patients during the first 48 hours after the diagnosis of peritonitis. The results were compared to those obtained in 10 long-term PD patients matched for the MTAC creatinine. In addition, the results of 8 peritonitis patients were compared with SPA results of 8 recently started PD patients, matched for MTAC creatinine. RESULTS: Peritonitis patients had a deeper maximal dip in D/P sodium, corrected for diffusion, than long-term patients (0.058 vs. 0.039, P < 0.05). Most parameters of peritoneal fluid transport were not different, except that t50 (i.e., the time to reach 50% of the maximum transcapillary ultrafiltration) was reached earlier during the dwell in peritonitis than in long-term PD-128 versus 175 minutes, P < 0.05. This confirmed the difference in the shape of the intraperitoneal volume versus time curve, which was blunted in the long-term patients. No differences were found for the parameters of solute transport between peritonitis patients and recently started patients. CONCLUSION: In contrast to patients with long-term PD, the osmotic conductance to glucose is unaffected in peritonitis, despite the lower net ultrafiltration caused by high solute transport. This implies that impaired free- water transport in chronic PD must be regarded as a contributing factor to UFF.