Cross-over study. Patients treated with peritoneal dialysis are investigated twice with a single 4h dwell study: once with Bicarbonate-Lactate solution as buffer (Physioneal TM) and once with conventional lactate PD solution (Dianeal TM). Radioidinated human serum albumin is used as a volume marker to assess ultrafiltration and frequent dialysis and blood sampling to assess peritneal transport of solutes and pH changes.
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.
All patients were studied twice with a 4-h dwell study (one peritoneal dialysis dwell) about 7 days apart. The two arms represent different order of the used periteonal dialysis fluid for the two dwell studies.
Research unit, renal medicine
Stockholm, Sweden
Difference in net ultrafiltration (ml)
Assessment of fluid transport during a PD dwell. Intraperitoenal volume changes during the 4 hour dwells will be assesed from dilution of the added volume marker with correction for absorption of the marker. Amount of marker remaining in the drained fluid after four hours will be subratcted from the initial added amount to calculate amount of marker absorbed during the dwell. Residual volumes before and after the dwell can also be calculated from dilution of the marker. This makes it possible to calculate the intraperitoneal volume of time curve during the dwell and net ultrafiltration (=net fluid removal). To simplify, the intraperitoneal volume (ml) at 240 minutes of the dwell minus the intraperitoneal volume after infusion of the dialysis fluid.
Time frame: 4 hours
Changes to acid-base homeostasis
Assessment of pH, concentrationa of bicarbonate and lactate i dialysate and plasma. Frequent dialysate sampling will be used and plasma levels will be assessed mutiple times. For each solute, the mass removed/absorbed will be calculated as the difference between the dialysate mass the end of the dwell (dialysate concentration times dialysate volume, corrected for total volume of samples) and mass immediately after infusion of fresh dialysate. The latter is calculated adding up the mass in residual and infused fluids. As the conventional lactate-buffered solution is acidic (pH 5.3) and the bicarbonate-lactate buffered solution is neutral (pH 7.4) the difference in pH between the solutions over time of the dwell may be described.
Time frame: 4 hours
Differences in small solute transport
Frequent dialysate sampling will be used and plasma levels will be assessed mutiple times for several small solutes. For each solute, the mass removed/absorbed will be calculated as the difference between the dialysate mass the end of the dwell (dialysate concentration times dialysate volume, corrected for total volume of samples) and mass immediately after infusion of fresh dialysate. The latter is calculated adding up the mass in residual and infused fluids. As the conventional lactate-buffered solution is acidic (pH 5.3) and the bicarbonate-lactate buffered solution is neutral (pH 7.4) it makes it possible to assess if pH affects transport characteristics of other solutes, in particular small solutes (Na, K, Ca, bicarbonate, lactate, creatinine, urea).
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Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
OTHER
Masking
NONE
Enrollment
7
Time frame: 4 hours
Differences in protein transport
Frequent dialysate sampling will be used and plasma levels will be assessed mutiple times for several small solutes. For each solute, the mass removed/absorbed will be calculated as the difference between the dialysate mass the end of the dwell (dialysate concentration times dialysate volume, corrected for total volume of samples) and mass immediately after infusion of fresh dialysate. The latter is calculated adding up the mass in residual and infused fluids. As the conventional lactate-buffered solution is acidic (pH 5.3) and the bicarbonate-lactate buffered solution is neutral (pH 7.4) it makes it possible to assess if pH affects transport characteristics of proteins (albumin and beta-2-microglobuline).
Time frame: 4 hours