A Comparison of Clearances on Tidal Peritoneal Dialysis and Intermittent Peritoneal Dialysisa

Objectives To compare the small molecule clearances on tidal peritoneal dialysis (TPD) and intermittent peritoneal dialysis (IPD), controlling for dialysate flow rate.Design Alternating 8-hour treatments on IPD and TPD (2 of each in 6 patients), each treatment separated by 3 or more days [patients returning to continuous ambulatory peritoneal dialysis (CAPD) in the interim] were performed. IPD treatments consisted of 15 exchanges with 2 Llexchange for a total of 30 Lltreatment. TPD treatments consisted of 29 exchanges, with an initial fill volume of 2 L, followed by 1 L tidal volume for the subsequent exchanges (reserve volume of 1 L) for a total of 30 Lltreatment.Patients Six patients, with a mean dialysatelplasma (DIP) creatinine as determined by the peritoneal equilibration test (PET) of 0.64±0.1 0, were studied. Four had a low -average DIP creatinine, while 2 had a high-average DIP creatinine.Measurements Urea nitrogen, creatinine, phosphate, and potassium clearances on TPD and IPD were compared using the paired t-test.Results The dialysate flow rates were 3.7±0.1 Llhour for IPD and 3.8±0.2 Llhour for TPD. The mean dialysate dextrose was 1.9±0.5 gldL for both. The creatinine clearances were 9±2 versus 10±3 mLlminute, the urea nitrogen clearances 19±3 versus 20±3 mLlminute, and phosphate clearances 10±3 versus 11±3 mLlminute for IPD and TPD, respectively (all not different). The ultrafiltration rates were 2.9±0.9 mLlminute on IPD and 3.3±1.6 mLI minute on TPD (not different). On both IPD and TPD the clearances of urea nitrogen, creatinine, and phosphate for the 2 patients with high-average DIP creatinine were higher than for the 4 patients with low -average DIP creatinine.Conclusions When the dialysate flow rate is controlled and a TPD prescription of 1 L reserve and tidal volumes is used, the small molecule clearances on IPD are similar to those on TPD.