To achieve more adequate dialysis in a shorter treatment time, seven children, characterized as high/high average (H/HA, 5 patients) and low/low average (L/LA, 2 patients) transporters according to the peritoneal equilibration test, were treated with tidal peritoneal dialysis (TPD) for 13.7 +/- 5.7 months, after being treated with nightly intermittent peritoneal dialysis (NIPD) for a similar period. We determined the TPD prescription necessary to provide improved clearances compared with NIPD within the same or less treatment time. Dialysis flow rate was significantly higher in TPD than NIPD, due to a reduction of dwell time and an increase in the number of exchanges. Peritoneal and total clearances of urea and creatinine were higher, whereas serum creatinine and urea nitrogen levels were lower and treatment duration shorter during TPD than NIPD, notwithstanding a decrease of residual renal function. Moreover, a mean time-averaged blood urea nitrogen level as low as 48.5 +/- 11.6 mg/dl was achieved during TPD. The improvement was more significant in H/HA than in L/LA patients.

We tested a new bedside method to determine the function of native arteriovenous fistula in 16 patients performed during hemodialysis without stopping the treatment. We initially measured vascular access flow (Q(a)) in each patient using the Transonic HD01(plus) device. We then measured the pressure in arterial and venous drip chambers at different blood pump flow rates (Q(bset)=0, 50, 100, 250, 300, 350 ml/min). The intravascular blood pressure gradient (P(f)) between arterial and venous puncture sites was estimated by a mathematical model. P(f) was positive for low Q(bset), but became negative when Q(bset) overcame the threshold value (Q(Inv)). Such critical flow showed a high correlation with Q(a), even if it was systemically lower. Computer analysis of fluid dynamics showed that when the blood pump flow overcame the Q(Inv) threshold, a critical transition from laminar flow to vortex circulation took place downstream of the venous needle, causing a dangerous shearstress on the vessel wall. Our results show that Q(Inv) provides an indication of the maximal blood pump flow rate needed to be reached to maximize blood flow supply in order to limit hemodynamic stress on the vascular access.

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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 (DIP) 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 DIP ratios for creatinine and urea at the fifth and seventh TPD exchanges, at 15–,30–,60, and 120-minute PETtimes, and on total TPD dialysate and TPD peritoneal creatinine and urea clearances. Results Correlation coefficients between PET -derived and total TPD dialysate-derived DIP 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. DIP ratios for creatinine and urea of the fifth and seventh TPD exchanges correlated significantly with the DIP 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 DIP 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.

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