What is the Optimal Frequency of Cycling in Automated Peritoneal Dialysis?

Abstract

Objective The recent increase in the use of automated peritoneal dialysis (APD) has led to concerns about the adequacy of clearances delivered by this modality. Few clinical studies looking at the effects of varying the individual components of the APD prescription on delivered clearance have been done, and most published data are derived from computer modeling. Most controversial is the optimal frequency of exchanges per APD session. Many centers prescribe 4 to 6 cycles per night but it is unclear if this is optimal. The purpose of this study was to address at what point the beneficial effect of more frequent cycles is outweighed by the concomitant increase in the proportion of the total cycling time spent draining and filling. Methods A comparison was made between the urea and creatinine clearances (CCrs) achieved by 4 different APD prescriptions, used for 7 days each, in 18 patients. The prescriptions were for 9 hours each and were all based on 2-L dwell volumes, but differed in the frequency of exchanges. They were 5 x 2 L, 7 x 2 L, and 9 x 2 L, as well as a 50% tidal peritoneal dialysis (TPD) prescription using 14 L. Ultrafiltration, dwell time, glucose absorption, sodium and potassium removal, protein excretion, and relative cost were also compared. Clearances due to day dwells and residual renal function were not included in the calculation. Results Mean urea clearances were 7.5, 8.6, 9.1, and 8.3 L/night for the four prescriptions respectively. Urea clearance with 9 x 2 L was significantly greater than with the other three prescriptions ( p < 0 0.05). Urea clearance with 7 x 2 L and TPD were superior to 5 x 2 L ( p < 0.05). Mean CCr was 5.1, 6.1, 6.4, and 5.6 L/night, respectively. Compared to 5 x 2-L, the 7 x 2-L, 9 x 2-L, and TPD prescriptions achieved greater CCr ( p < 0.05). Taking both urea and CCr into account, 9 x 2 L was the optimal prescription in 12 of the 18 patients. Ultrafiltration and sodium and potassium removals were all significantly greater with the higher frequency prescriptions. Conclusion The 5 x 2-L prescription significantly underutilizes the potential of APD to deliver high clearances, and 7 x 2 L is a consistently superior prescription if 2-L dwells are being used. Although more costly, 9 x 2 L should be considered if higher clearances are required.

The role of tidal peritoneal dialysis in modern practice: A European perspective

“…In contrast, Hölttä et al 10 found similar total albumin losses in the dialysate in pediatric patients on CCPD and TPD. In the study by Perez et al, 21 there was also no difference in protein loss between non-tidal APD (5 Â 2, 7 Â 2 and 9 Â 2 l) and 50% TPD (treatment volume 14 l). In agreement with these results there was neither an influence of dialysate flow nor of treatment modality (50% TPD vs IPD) on total protein and albumin loss into the dialysate in our previous study.…”

“…No data on treatment volumes are included in this abstract. In the study by Perez et al, 21 there was no significant difference in peritoneal ultrafiltration and glucose absorption between 50% TPD (14 l) and 7 Â 2 l nontidal APD. Sodium removal with 50% TPD was 181.67 79.8 mmol/treatment vs 138.2774.9 mmol/treatment with 7 Â 2 l non-tidal APD.…”

“…When increasing the treatment volume to 14 or 24 l, no significant difference was found between the two treatment modalities. Perez et al 21 reported that there were no differences in creatinine clearances, urea clearances, and potassium removal between non-tidal APD (7 Â 2 l per night) and 50% TPD (14 l/night, fill volume 2 l, tidal volume 1 l).…”

“…Small solute clearances on APD in H/HA patients are higher than in L/LA patients when treatment volume is kept constant. 13,18,21,22 There is the question if peritoneal transport type also influences the effect of TPD vs other APD modalities on clearances. In the study by Edefonti et al, 13 improvement of small solute clearances with TPD as compared to nightly intermittent peritoneal dialysis was more marked in patients with H/HA peritoneal transport rates than in L/LA patients.…”

Briefly Noted

“…A study of 18 patients receiving 9‐hour automated peritoneal dialysis regimens of five, seven, or nine 2 L exchanges found that the increased inflow/outflow “downtime” of more frequent exchanges generally did not have a negative impact on clearances (11). Mean urea (and creatinine) nightly clearances in the three groups were 7.5, 8.6, and 9.1 L (5.1, 6.1, and 6.4 L) with a similar pattern in both low/low‐average and high/high‐average transporters.…”