Prescription and assessment of tidal peritoneal dialysis delivery with a specific equilibration test

Objective: To propose a simplified equilibration test specific for tidal peritoneal dialysis (TPD) that will overcome the inconveniences of the measurement of TPD peritoneal solute clearances through whole dialysate collection. This will enable the prediction of peritoneal creatinine and urea clearances, the suitability of patients for TPD, and routine assessment of TPD delivery. Design: In a prospective study, patients had a standardized TPD run, and dialysate-to-plasma (D/P) ratios for creatinine and urea were calculated at various TPD and peritoneal equilibration test (PET) time points and on total TPD dialysate. Solute clearances were estimated and measured, and correlation coefficients were obtained among all these variables. Setting: Dialysis unit of a pediatric nephrology department and patients' homes. Patients: Eleven pediatric patients with end-stage renal disease in stable clinical conditions treated with TPD. Interventions: Dialysate and blood sample collections. Main Outcome Measures: D/P ratios for creatinine and urea at the fifth and seventh TPD exchanges, at 15-, 30-, 60- and 120-minute PET times, and on total TPD dialysate and TPD peritoneal creatinine and urea clearances. Results: Correlation coefficients between PET-derived and total TPD dialysate-derived D/P ratios, and those between PET-derived and measured creatinine and urea clearances were more significant at the 120-minute PET time point compared with the other PET time points. Best correlations were obtained at the fifth and seventh TPD exchanges. D/P ratios for creatinine and urea of the fifth and seventh TPD exchanges correlated significantly with the D/P ratios calculated from total TPD dialysate. A significant correlation was also found between peritoneal creatinine and urea clearances on total dialysate volume (measured clearances) and those derived from the dialysate collection of the fifth and seventh TPD exchanges (estimated clearances) - that based on the seventh exchange being slightly more significant. Moreover, the estimated clearances derived from the seventh exchange were within 10% of the measured value in 90.9% of patients both for creatinine and urea. Conclusion: The significant correlation between measured and estimated peritoneal creatinine and urea clearances and the low percentage of underestimates of measured clearances obtained using the seventh TPD exchange-derived indices confirm the accuracy of the D/P ratios for creatinine and urea derived from any exchange after the fifth (preferably the seventh) of a standardized TPD run in estimating peritoneal creatinine and urea clearances. This method could represent a simple and accurate means for prescribing TPD and routinely assessing TPD delivery.