Background: The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) has evidence- and opinion-based recommendations for weekly Kt/V(urea) and weekly total creatinine clearance (CC) in chronic peritoneal dialysis (CPD) patients. Using standard continuous ambulatory peritoneal dialysis technique, it is often difficult to achieve the suggested targets in anuric patients with large body mass. Thus, the use of automated peritoneal dialysis (APD) has been increasingly utilized to achieve adequate clearances. Automated dialysis is usually performed at night over an 8- to 10-hour period. The role of increases in dialysate volume and frequency of exchanges during this time period to achieve these target K/DOQI recommendations remains uncertain. We decided to study the effects of increasing the volume and number of exchanges in a fixed period of time in CPD patients.
Methods: In the New Haven CAPD unit, 29 patients maintained on APD were considered eligible for the study and 11 agreed to participate. The patients were characterized according to standard peritoneal equilibration test criteria. The patients were placed into two groups: group 1 included high (H) and high-average (HA), and group 2 low-average (LA) transporters. The patients were dialyzed at night for 9 hours with standard cycling technique, using 2.5% Dianeal (Baxter Healthcare, Deerfield, Illinois, USA) solution, with a cycle volume of 2,500 mL, and a 2,000-mL daytime dwell. Three studies were done on each patient using a total dialysis volume of 9.5 L (3 cycles), 14.5 L (5 cycles), and 19.5 L (7 cycles). Daily Kpt/V(urea) and daily CCp (peritoneal) (L/day/1.73 m2) were obtained.
Results: Six patients were H or HA (group 1) and 5 were LA transporters (group 2). For the group 1 patients, mean weight was 86.6 +/- 13.5 kg; Kpt/V(urea) was 1.68 +/- 0.21 using 9.5 L, 2.03 +/- 0.28 for 14.5 L (p < 0.05 compared to 10 L), and 2.28 +/- 0.28 with 19.5 L (p < 0.05 compared to 10 L and 15 L); mean weekly CCp was 45.43 +/- 7.63 L/1.73 m2 for 9.5 L (p < 0.05 compared to 14.5 L and 19.5 L), 51.17 +/- 7.07 with 14.5 L, and 54.67 +/- 10.08 for 19.5 L; ultrafiltration rates were not different in the three studies. For the group 2 patients, mean weight was 74.3 +/- 17.7 kg; mean weekly Kpt/V(urea) was 1.68 +/- 0.35 using 9.5 L, 2.10 +/- 0.42 for 14.5 L (p < 0.05 compared to 9.5 L), and 2.31 +/- 0.56 for 19.5 L (p < 0.05 compared to 9.5 L and 14.5 L); mean weekly CCp was 42.56 +/- 10.64 L/1.73 m2 for 9.5 L (p < 0.05 compared to 14.5 L and 19.5 L), 50.89 +/- 12.66 for 14.5 L, and 51.94 +/- 11.20 for 19.5 L; ultrafiltration was lower in the 9.5-L study than in the 14.5-L and 19.5-L studies, but was not different in the 14.5-L and 19.5-L studies.
Conclusions: In both H/HA and LA transporters, Kpt/V(urea) and CCp rise significantly when the frequency of exchanges and total volume of dialysate are increased. Thus, the use of larger volumes of dialysate with cycling peritoneal dialysis may result in increased clearances of urea and creatinine.