Can a 1-h peritoneal equilibration test accurately assess free water transport in peritoneal dialysis patients?

Background In peritoneal dialysis, approximately 40% of the total osmotic ultrafiltration (UF) induced by glucose can be predicted to be due to “free” water transport across aquaporin-1 (APQ-1). Theoretically, it would be possible to assess the fraction of free water transport in the early phase of a hypertonic dwell, when UF rate is high and the relative contribution of Na+ diffusion is low. La Milia et al. [La Milia V. et al. Fast-fast peritoneal equilibration test (FAST-FAST-PET): a simple method for peritoneal hydraulic permeability study [Abstract]. Nephrol Dial Transplant 2002; 17 (Suppl 1):17–18] suggested a technique to assess sodium-associated water transport based on sodium removal (Na+R) divided by the plasma Na+ concentration during a “fast-fast” (60 minute) peritoneal equilibration test (PET) for 3.86% glucose, yielding an estimate of the UF passing through the small pores (UFSP). Free water transport (UF through ultrasmall pores; UFUSP) was obtained by subtracting UFSP from total UF. Although peritoneal Na+ transport is almost totally convective, this technique will slightly overestimate small-pore UF due to the presence of some small-pore Na+ diffusion from the circulation during the dwell. A way of dealing with this problem was presented recently by Smit (Smit W. et al. Quantification of free water transport in peritoneal dialysis. Kidney Int 2004; 66:849–854). Methods In the present study we used the three-pore model of peritoneal transport to predict the degree of overestimation of UFSP for the technique presented by La Milia et al., and any potential deviations from theory for the technique presented by Smit et al. Simulations were performed under ordinary conditions and during simulated UF failure for 3.86% glucose. The fractional UF coefficient accounted for by APQ-1 was set at 2%. Results Estimating the UFSP from the sodium-associated water transport according to the method by La Milia et al. consistently overestimated UFSP and underestimated UFUSP. These errors were, however, minimal for dwells lasting between 30 and 80 minutes. The technique by Smit et al. to calculate aquaporin-mediated water flow (UFUSP), using an elaborate correction for Na+ diffusion from the circulation during the dwell, seemed accurate in most situations but, in general, tended to moderately overestimate UFUSP at early dwell times (<30 minutes) and underestimate UFUSP at long dwell times (4 hours). Conclusions The technique presented by La Milia et al. to calculate free water transport during a fast-fast PET was found to be surprisingly accurate, although the procedure would further improve by the introduction of a correction algorithm. The technique by Smit is even more accurate for dwells up to 4 hours’ duration. However, since the Smit technique is elaborate, it is less practical for routine determinations of aquaporin-mediated water transport in peritoneal dialysis.

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Quantification of Free Water Transport during the Peritoneal Equilibration Test

Peritoneal Dialysis International ◽

10.1177/089686080902900509 ◽

2009 ◽

Vol 29 (5) ◽

pp. 523-527 ◽

Cited By ~ 19

Author(s):

Trijntje T. Cnossen ◽

Watske Smit ◽

Constantijn J.A.M. Konings ◽

Jeroen P. Kooman ◽

Karel M. Leunissen ◽

...

Keyword(s):

Peritoneal Dialysis ◽

Water Transport ◽

Peritoneal Cavity ◽

Glucose Solution ◽

Free Water ◽

Peritoneal Equilibration Test ◽

Additional Information

Objective Free water transport (FWT) can be calculated after a dwell of 1 hour with a 3.86% glucose solution using sodium kinetics (mini-PET, as developed by LaMilia et al.). This requires measurement of the intraperitoneal volume after drainage of the abdomen. Since valuable information of a 4-hour peritoneal equilibration test (PET) may be lost, the aim of the present study was to investigate whether temporary drainage of the peritoneal cavity after 1 hour and re-instillation thereafter would influence the results of the 4-hour PET. Methods and Patients Two PETs were performed in 10 stable peritoneal dialysis (PD) patients (mean age 59 ± 13 years, mean duration on PD 33 ± 15 months) within a mean period of 54 (range 13 – 104) days: one standardized 4-hour PET using 3.86% glucose (PET A) and one with drainage after 1 hour followed by re-instillation (PET B). Results Mean total ultrafiltration (UF) of PETs A and B was 667 ± 210 mL and 621 ± 206 mL (NS). Mean FWT at 60 minutes was 164 ± 74 mL and mean UF through the small pores was 204 ± 181 mL; FWT correlated well with total UF ( r = 0.720, p = 0.019). Classification of transport categories was identical for 9 of the 10 patients. Comparison of 1-hour and 4-hour results in test B showed a good correlation between dialysate-to-plasma ratios (D/P) of creatinine and urea and Dt/D0 ratios of glucose. Conclusion A 4-hour 3.86% glucose PET, including temporary drainage after 1 hour for assessment of free water transport, does not influence the results of D/P creatinine or Dt/D0 glucose and gives essential additional information on aquaporin function.

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Longitudinal follow-up of Free Water Transport, D/P Cr and Effluent Ca125 in patients on Peritoneal Dialysis

10.26226/morressier.59a56f96d462b8028d895fbf ◽

2017 ◽

Author(s):

Miguel Oliveira

Keyword(s):

Peritoneal Dialysis ◽

Water Transport ◽

Free Water

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Endothelial Glycocalyx and the Peritoneal Barrier

Peritoneal Dialysis International ◽

10.1177/089686080802800102 ◽

2008 ◽

Vol 28 (1) ◽

pp. 6-12 ◽

Cited By ~ 33

Author(s):

Michael F. Flessner

Keyword(s):

Peritoneal Dialysis ◽

Water Transport ◽

Critical Role ◽

Basic Research ◽

Endothelial Glycocalyx ◽

Dialysis Patients ◽

Solute Transfer ◽

Histological Studies ◽

Initial Resistance

Recent advances in the study of the microcirculation have demonstrated the critical role of the endothelial glycocalyx in transcapillary transport from the plasma to the tissue interstitium. Since the capillary wall represents the initial resistance to solute transfer from the plasma through the tissue to the dialysate, the glycocalyx is potentially of major importance to peritoneal dialysis. Inadvertently removed in early histological studies, this thin, delicate layer of glycosaminoglycans and proteoglycans is now recognized as a primary barrier in transendothelial solute and water transport. Subperitoneal endothelia are exposed to inflammation, angiogenesis, and hyperglycemia, which have been shown to affect the layer by increasing permeability. This entity permits new hypotheses concerning the factors that influence the transport characteristics of peritoneal dialysis patients and provides new avenues of basic research into the fundamental mechanisms of alteration of the peritoneal barrier.

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The cellular contribution to effluent potassium and its relation to free water transport during peritoneal dialysis

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfm497 ◽

2007 ◽

Vol 22 (12) ◽

pp. 3593-3600 ◽

Cited By ~ 10

Author(s):

A. M. Coester ◽

D. G. Struijk ◽

W. Smit ◽

D. R. de Waart ◽

R. T. Krediet

Keyword(s):

Peritoneal Dialysis ◽

Water Transport ◽

Free Water

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Peritoneal Water Transport Characteristics of Diabetic Patients Undergoing Peritoneal Dialysis: A Longitudinal Study

American Journal of Nephrology ◽

10.1159/000477829 ◽

2017 ◽

Vol 46 (1) ◽

pp. 47-54 ◽

Cited By ~ 4

Author(s):

Ana Fernandes ◽

Roi Ribera-Sanchez ◽

Ana Rodríguez-Carmona ◽

Antía López-Iglesias ◽

Natacha Leite-Costa ◽

...

Keyword(s):

Peritoneal Dialysis ◽

Water Transport ◽

Free Water ◽

Volume Overload ◽

Diabetic Patients ◽

Longitudinal Analyses ◽

Cross Sectional ◽

Sodium Removal ◽

Essential Stability ◽

Stability Of Water

Background: Volume overload is frequent in diabetics undergoing peritoneal dialysis (PD), and may play a significant role in the excess mortality observed in these patients. The characteristics of peritoneal water transport in this population have not been studied sufficiently. Method: Following a prospective, single-center design we made cross-sectional and longitudinal comparisons of peritoneal water transport in 2 relatively large samples of diabetic and nondiabetic PD patients. We used 3.86/4.25% glucose-based peritoneal equilibration tests (PET) with complete drainage at 60 min, for these purposes. Main Results: We scrutinized 59 diabetic and 120 nondiabetic PD patients. Both samples showed relatively similar characteristics, although diabetics were significantly more overhydrated than nondiabetics. The baseline PET disclosed lower ultrafiltration (mean 439 mL diabetics vs. 532 mL nondiabetics, p = 0.033) and sodium removal (41 vs. 53 mM, p = 0.014) rates in diabetics. One hundred and nine patients (36 diabetics) underwent a second PET after 12 months, and 45 (14 diabetics) underwent a third one after 24 months. Longitudinal analyses disclosed an essential stability of water transport in both groups, although nondiabetic patients showed a trend where an increase in free water transport (p = 0.033) was observed, which was not the case in diabetics. Conclusions: Diabetic patients undergoing PD present lower capacities of ultrafiltration and sodium removal than their nondiabetic counterparts. Longitudinal analyses disclose an essential stability of water transport capacities, both in diabetics and nondiabetics. The clinical significance of these differences deserves further analysis.

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Free Water Transport and its Association with Cardiovascular Status in Children on Peritoneal Dialysis

Peritoneal Dialysis International ◽

10.3747/pdi.2018.00113 ◽

2019 ◽

Vol 39 (4) ◽

pp. 323-329

Author(s):

Lilian Bolte ◽

Maria Jose Ibacache ◽

Iris Delgado ◽

Francisco Cano

Keyword(s):

Peritoneal Dialysis ◽

Left Ventricular Hypertrophy ◽

Water Transport ◽

Ventricular Hypertrophy ◽

Roc Analysis ◽

Characteristic Curve ◽

Negative Relationship ◽

Free Water ◽

Inverse Correlation ◽

Left Ventricular

BackgroundVolume overload is one of the most important factors associated with left ventricular hypertrophy (LVH) and cardiovascular disease in chronic peritoneal dialysis (PD) patients. MiniPET is a reliable tool to evaluate free water transport (FWT). In a clinical setting, the significance of FWT has not been evaluated in terms of outcome in children on PD. The objective was to define a FWT value of clinical significance in children on PD, fixing its relationship to left ventricular mass index (LVMI) as a well-known outcome parameter.MethodsMiniPET was performed with 3.86% glucose, 1-h long, to measure FWT in PD patients > 6 years old. An echocardiogram (ECG) was performed within 2 months of the MiniPET. Left ventricular hypertrophy was defined as LVMI ≥ 38.6 g/height2.7(95th percentile). Receiver operating characteristic curve (ROC) analysis was used to determine the cut-off value of FWT searching the highest sensitivity and specificity to differentiate patients with normal/abnormal LVMI. A p < 0.05 was considered significant.ResultsForty-six studies were performed on 32 patients, 16 males; mean age 11.59 ± 3.07 years. Mean normalized FWT (nFWT) was 144.4 ± 84.8 mL/m2, corresponding to 46.7% of total ultrafiltration. Mean LVMI was 42 ± 11.3 g/m2.7with a negative correlation to nFWT ( p < 0.01). Eighteen out of 32 patients had LVH. The ROC analysis (nFWT vs LVMI) showed an area under the curve of 0.71 (95% confidence interval [CI], 0.53 – 0.89; p = 0.04), allowing a cut-off nFWT value of 110 mL/m2to be defined, dividing the population into 2 groups of patients according to the LVMI cut-off value of 38,6 g/m2.7.ConclusionsThe nFWT showed an inverse correlation to LVMI. A nFWT value < 110 mL/m2was significantly associated with LVH. The negative relationship observed between nFWT and LVMI, and the cut-off level for nFWT according to the 95th percentile of LVMI, suggest that the regular evaluation of nFWT could become a useful tool in assessing the capacity of PD treatment to keep patients’ volume status under control, avoiding cardiovascular impairment.

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Measuring Peritoneal Absorption with the Prolonged Peritoneal Equilibration Test from 4 to 8 Hours Using Various Glucose Concentrations

Peritoneal Dialysis International ◽

10.3747/pdi.2013.00235 ◽

2014 ◽

Vol 34 (6) ◽

pp. 605-611 ◽

Cited By ~ 4

Author(s):

Josep Teixidó–Planas ◽

Maria Isabel Troya–Saborido ◽

Guillermo Pedreira–Robles ◽

Milagros Del-Rio–Lafuente ◽

Ramon Romero–Gonzalez ◽

...

Keyword(s):

Water Transport ◽

Peritoneal Fluid ◽

Glucose Solution ◽

Free Water ◽

Random Order ◽

Practical Method ◽

University Hospital ◽

Transport Parameters ◽

Peritoneal Equilibration Test ◽

Small Pore

BackgroundPeritoneal fluid flows such as small-pore ultrafiltration and free water transport can now be calculated by means of the modified peritoneal equilibration test (PET). To calculate peritoneal fluid absorption, volume markers have been used, but that method is not easily applicable in clinical practice. Alternatively, absorption can be estimated using the personal dialysis capacity test. However, a method of measuring overall peritoneal absorption together with the PET is lacking. The aim of the present study was to assess whether overall peritoneal absorption was different when measured from the 4th to 8th hour in a prolonged PET using three different glucose solutions.MethodsThe study enrolled 32 stable peritoneal dialysis (PD) patients from a tertiary university hospital, who underwent three 8-hour prolonged PETs with 1.36%, 2.27%, and 3.86% glucose solution. The PETs were performed in random order over a period of less than 1 month. During the prolonged PET, the peritoneal volume was emptied and reinfused at 60 and 240 minutes and drained at 480 minutes. Peritoneal absorption was calculated as the volume difference between the 4th and the 8th hour.ResultsThe dialysate-to-plasma ratio (D/P) of urea, the D/P creatinine, and the mass transfer area coefficient (MTC) of creatinine at 240 minutes were not significantly different with the three glucose solutions. The end-to-initial (D/D0) glucose, MTC urea, and MTC glucose were significantly different. All water transport parameters were significantly different, except for the 4- to 8-hour absorption volumes and rates. The peritoneal absorption rates were, for 1.36% solution, 1.03 ± 0.58 mL/min [95% confidence interval (CI): 0.83 to 1.24 mL/min]; for 2.27% solution, 0.86 ± 0.71 mL/min (95% CI: 0.61 to 1.11 mL/min); and for 3.86% solution, 1.05 ± 0.78 mL/min (95% CI: 0.77 to 1.33 mL/min). Peritoneal absorption volumes and rates from the 4th to the 8th hour showed good correlations for the various solutions.ConclusionsUsing any glucose solution, the prolonged PET with voiding and reinfusion at the 4th hour could be a practical method for calculating overall peritoneal absorption from the 4th to the 8th hour in PD patients.

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