Patients treated with peritoneal dialysis (PD)are investigated twice of different days with a single 4h dwell study: once with solution with a solution with bicarbonate 15 mmol/L abd Lactate 15 mmol/L as buffer (Physioneal TM) and once with conventional lactate-buffered (40 mmol/L) PD solution (Dianeal TM). Aproximately 2 liter of PD solution was infused each time. Intraperitoneal fluid was sampled during the dwell at t = 0, 3, 6, 10, 15, 20, 25, 30, 40, 50, 60, 90, 120, 180, and 240 minutes from the end of the dialysis fluid infusion and the start of the peritoneal dwell. Venous blood samples were drawn from the patient before the start of the dwell and at t = 15, 60, 120, 240 minutes.
New and spent dialysate bags were weighed before and after each dwell to assess infused and drain volumes, respectively; the volumes were adjusted for the weight of the empty bags. Radio-iodinated serum albumin (RISA) added to the solutions before infusion was used as volume marker to estimate intraperitoneal volume. The residual volume (after the previous dwell) was calculated from the dilution of the marker upon infusion of fresh dialysate; after the dwell the peritoneal cavity was rinsed with 1 liter of solution (glucose 1.36%) in order to estimate post-drain residual volume.
Ultrafiltration volume was calculated from the changes in intraperitoneal volume (using 3 minutes after infusion as reference) and corrected for volumes of taken samples. The rate of peritoneal absorption was estimated from the disappearance of the marker from the peritoneal cavity\].
The composition of the pre-dialysis (residual) fluid was assessed based on the sample taken from the spent dialysate from the previous dwell.
Concentrations of urea, creatinine, glucose, phosphate, chloride, and lactate, in plasma and dialysate, were measured by Monarch 1000 (Instrumentation Laboratory, MA), while flame photometry was used for sodium and potassium. Dialysate pH was measured with a pH meter. The concentrations of calcium, CO2, bicarbonate, and plasma pH were measured by AVL OMNI Combi Blood Gas Analyzer (AVL, Graz, Austria). The plasma concentrations of glucose, sodium, urea, creatinine, potassium, chloride, and phosphate were corrected for plasma water fraction. Creatinine measurements in dialysate were corrected for glucose concentration. Albumin and beta-2 microglobulin (B2M) concentration were measured with immunological methods.
Advanced mathematical modelling is used to analyze the results and tgo asses transport parameters.
