Peritoneal Transport Kinetics of Proteins in Children on Chronic Peritoneal Dialysis

Objective

This study describes a modified 4-hour peritoneal equilibration test (PET) for analyzing peritoneal transport characteristics of proteins with different molecular weights and predicting daily peritoneal protein losses in children on chronic peritoneal dialysis (PD).

Design

Cross-sectional study.

Setting

A single regional pediatric dialysis unit in a teaching hospital.

Patients

9 stable pediatric dialysis patients; 4 were on continuous ambulatory PD, 5 were on continuous cycling PD.

Main Outcome Measures

Serum and dialysate concentrations of IgG, albumin, β2-microglobulin, and transferrin were determined during a PET. Changes in dialysate-to-plasma (D/P) ratios were determined hourly. Agreement between PET-derived and measured daily peritoneal protein losses was examined.

Results

The D/P ratio decreased with increased molecular radius ( p < 0.0001). Many children had low plasma levels of IgG, albumin, and transferrin, but elevated levels of β2-microglobulin. The D/P ratio increased linearly during the PET for all measured proteins, regardless of molecular weight. There was close correlation between 4-hour PET protein losses and 24-hour losses during routine PD.

Conclusions

Proteins are lost through the peritoneum according to their size, demonstrating linear transport kinetics during a 4-hour PET. The PET-derived data predicted daily protein losses in children on chronic PD. This approach might help to eliminate inaccuracies due to incomplete dialysate collection.

Day-to-day variability of adequacy indexes in peritoneal dialysis

BACKGROUND

The achievement of dialysis adequacy targets in peritoneal dialysis (PD) is assessed by the calculation of the Kt/V and creatinine clearance (C(Cr)) obtained by collecting dialysate and urine, usually two or three times a year. Prescription decisions are based on such adequacy assessments, regardless of any variability in the single measurements. The aim of our study was to assess the day-to-day variability of common dialysis adequacy parameters and to evaluate its impact on the adequacy indexes in PD.

METHODS

Twenty-four patients (14 CAPD, 10 APD) at two centres were studied by means of a triple dialysate and urine collection for a period of 1 week. Variability in the findings for a given patient was expressed by the coefficient of variation (CV%) calculated for peritoneal (p), renal, and total (tot) adequacy parameters. The target Kt/V and C(Cr) values were recalculated on the basis of variability.

RESULTS

Kt/V was less variable (CV 4.0 and 4.4% for peritoneal Kt/V (pKt/V) and total Kt/V (totKt/V) respectively) than C(Cr) (4.7 and 6.0% for peritoneal creatinine clearance (pC(Cr)) and total creatinine clearance (totC(Cr)) respectively) and proved to be a more reliable indicator of adequacy in terms of the CV. Both variability parameters became worse if renal clearance was added to peritoneal clearance. CV in APD proved to be no different from CAPD for all the parameters considered. In our centres dialysis adequacy target correction for variability provided safe values for weekly Kt/V (pKt/V=1.78-2.10 and totKt/V=1.82-2.15 target 1.7-2.0) and C(Cr)/1.73 (pC(Cr)=53.7-64.4 l and totC(Cr)=55.1-66.1 l; target 50-60 l).

CONCLUSIONS

Evaluating the adequacy of PD by means of a single measurement should take into account the weekly variability as demonstrated by a triple dialysate and urine collection. Standard adequacy targets can be corrected to allow for variability. Thus one can obtain safe values for prescription decisions based on a single collection result.

Optimal care of the pediatric end-stage renal disease patient on dialysis

This manuscript is an effort on behalf of the American Society of Pediatric Nephrology to provide recommendations designed to optimize the clinical care of pediatric patients with end-stage renal disease (ESRD). Although many of the recommendations are evidenced-based with the supporting data being derived from a variety of sources, including patient registries, others are opinion-based and derived from the combined clinical experience of the authors. In all cases, it is recommended that the decision to initiate dialysis should be made only after an assessment of a combination of biochemical and clinical characteristics. Irrespective of the choice of dialysis modality (hemodialysis v peritoneal dialysis), dialysis efficacy should be measured regularly, and the dialysis prescription should be designed to achieve target clearances. Attention to dialysis adequacy, control of osteodystrophy, nutrition, and correction of anemia is mandatory, because all may influence patient outcome in terms of growth, cognitive development, and school performance. Finally, the availability of a multidisciplinary team of pediatric specialists is desirable to provide all facets of pediatric ESRD care, including renal transplantation, in an optimal manner. Future clinical research efforts intended to address topics such as dialysis adequacy, anemia management, and growth should be encouraged.