Mathematical modeling of the glucose-insulin system during peritoneal dialysis with glucose-based fluids.

The purpose of this study was to analyze the effect of peritoneal dialysis with glucose-based solution on plasma glucose and insulin responses in patients on continuous ambulatory peritoneal dialysis (CAPD), describe the glucose-insulin system using a mathematical model, and identify abnormalities in this system. Six-hour dwell studies--using glucose 3.86% solution with a volume marker--were performed in 13 stable, fasting, nondiabetic CAPD patients. We used a mathematical model based on the previous works of Stolwijk and Hardy (1974) and Tolic et al (2000) to estimate the parameters of glucose-insulin system, insulin sensitivity index (Sl), and glucose effectiveness at basal (SG) and zero (GEZI) insulin. The individual peaks in plasma glucose and insulin concentrations occurred after 30-60 minutes of the dwell, with the average increase of 52% and 168% over the initial values, respectively. Increased insulin resistance was found in most of these patients. Both clinical and simulation results demonstrated a high interpatient variability in glucose and insulin kinetics and glucose-insulin system parameters in the patients. We demonstrated a successful control of increasing plasma glucose by insulin, despite an increased insulin resistance, during CAPD.

The kinetics of water transperitoneal transport during long-term peritoneal dialysis performed using icodextrin dialysis fluid.

INTRODUCTION: Dialysis fluid containing icodextrin is used in patients on peritoneal dialysis (PD) because of its significant ultrafiltration properties. The use of the fluid in treating patients with congestive heart failure resistant to diuretics has also been reported. OBJECTIVES: The aim of the study was to evaluate water peritoneal transport during a 16-hour dialysis exchange performed using icodextrin-containing dialysis fluid. PATIENTS AND METHODS: Eleven clinically stable patients were enrolled in the study (5 women and 6 men; mean age, 50.4 +/- 18.3 years), treated with PD for 26.9 +/- 22.4 months. Water transperitoneal transport was evaluated using a modified version of Babb-Randerson-Farrell thermodynamic model of membrane transport with human albumin marked with iodine as the marker of intraperitoneal volume. Based on blood and dialysate samples collected during the 16-hour dialysis exchange, the intraperitoneal volume of dialysate and dialysate reverse absorption were calculated. RESULTS: There were no clinical complications associated with the use of icodextrin fluid during the study. A significant increase in intraperitoneal volume of dialysate (950 ml on average) compared to the initial value was observed in the whole group at the 16th hour of the exchange. CONCLUSIONS: The study demonstrated that dialysis fluid with icodextrin ensured effective ultrafiltration during a 16-hour dialysis exchange. This indicates its potential usefulness in the treatment of patients with severe congestive heart failure with or without coexisting end-stage renal disease.

Isolation, banking, encapsulation and transplantation of different types of Langerhans islets.

INTRODUCTION: The discovery of a cure for diabetes is a dream of many medical researchers. The transplantation of Langerhans islets is a potential treatment of choice for patients with type 1 diabetes as a source of endogenous insulin for the recipient. OBJECTIVES: The aim of the experiment was to transplant Langerhans islets without immunosuppression. To protect the grafts against transplant rejection, semipermeable membranes could be used. MATERIAL AND METHODS: Langerhans islets were isolated from rats and pigs and immunoisolated by encapsulation in alginate-protamine-heparin (APH) or alginate-poly-L-lysine-alginate (APA) membranes. Islets were pooled in a controlled manner. Tests for cryopreservation and biocompatibility were also performed. RESULTS: The capsules coated with APH are more resistant than the capsules coated with APA. After transplantation of the islets immunoisolated with APA, euglycemia is maintained longer than after transplantation of the islets immunoisolated with APH. Microencapsulation protects the islets from destruction by the host. CONCLUSIONS: It is feasible to treat experimental diabetes by transplantation of encapsulated Langerhans islets without immunosuppression.

Kinetic analysis of peritoneal fluid and solute transport with combination of glucose and icodextrin as osmotic agents.

BACKGROUND: Controlling extracellular volume and plasma sodium concentration are two crucial objectives of dialysis therapy, as inadequate sodium and fluid removal by dialysis may result in extracellular volume overload, hypertension, and increased cardiovascular morbidity and mortality in end-stage renal disease patients. A new concept to enhance sodium and fluid removal during peritoneal dialysis (PD) is the use of dialysis solutions with two different osmotic agents. AIM: To investigate and compare, with the help of mathematical modeling and computer simulations, fluid and solute transport during PD with conventional dialysis fluids (3.86% glucose and 7.5% icodextrin; both with standard sodium concentration) and a new combination fluid with both icodextrin and glucose (CIG; 2.6% glucose/6.8% icodextrin; low sodium concentration). In particular, this paper is devoted to improving mathematical modeling based on critical appraisal of the ability of the original three-pore model to reproduce clinical data and check its validity across different types of osmotic agents. METHODS: Theoretical investigations of possible causes of the improved fluid and sodium removal during PD with the combination solution (CIG) were carried out using the three-pore model. The results of computer simulations were compared with clinical data from dwell studies in 7 PD patients. To fit the model to the low net ultrafiltration (366+/-234 mL) obtained after a 4-hour dwell with 3.86% glucose, some of the original parameters proposed in the three-pore model (Rippe & Levin. Kidney Int 2000; 57:2546-56) had to be modified. In particular, the aquaporin-mediated fractional contribution to hydraulic permeability was decreased by 25% and small pore radius increased by 18%. RESULTS: The simulations described well clinical data that showed a dramatic increase in ultrafiltration and sodium removal with the CIG fluid in comparison with the two other dialysis fluids. However, to adapt the three-pore model to the selected group of PD patients (fast transporters with small ultrafiltration capacity on average), the peritoneal pore structure had to be modified. As the mathematical model was capable of reproducing the clinical data, this shows that the enhanced ultrafiltration with the combination fluid is caused by the additive effect of the two different osmotic agents and not by a specific impact of the new dialysis fluid on the transport characteristics of the peritoneum.

Impact of oxygenation of bioartificial liver using perfluorocarbon emulsion perftoran on metabolism of human hepatoma C3A cells.

One of the most important challenges in bioartificial liver designed for patients suffering from acute liver failure is oxygenation of cells within the bioreactor. The aim of this study was to evaluate the impact of oxygenation of bioartificial liver using perfluorocarbon (PFC) emulsion on the metabolic activity of hepatic cells in vitro. Mineral fibers coated with collagen type I were used as scaffolds for hepatic cells. Significantly higher total protein synthesis by hepatic C3A cells cultured in the bioreactor for 24 hours, in the group treated with medium supplemented with PFC emulsion, was observed in comparison with medium without PFC. Albumin production increased in the group treated with PFC after 1 hour of perfusion and was continuously, statistically, significantly higher during perfusion then the control group. In conclusion, the use of oxygen carriers, such as the PFC emulsion, can significantly improve synthetic performance of the bioreactor. Mineral fibers coated with extracellular proteins may serve as support for hepatic cells in the bioreactor.

Spongy polyethersulfone membrane for hepatocyte cultivation: studies on human hepatoma C3A cells.

There are different types of membranes used for hepatocyte cultivation. In our studies, spongy polyethersulfone (PES) membranes were examined as a support for hepatic cell cultivation in vitro. The extended surface of the membranes allows to introduce a high cell number especially in three-dimensional gel structure. Scanning electron microscopy analysis indicated that C3A cells used in our experiments grew well on PES membranes forming microvilli characteristic for normal hepatocytes. Analysis of cell viability proved that spongy PES membrane is well tolerated by J774 macrophages and did not stimulate nitric oxide synthesis. Bile canalicular structures were observed in fluorescence microscopy after F-actin staining with tetramethyl rhodamine iso-thiocyanate (TRITC)-phalloidin. The C3A cells showed high affinity to the PES membranes and adhered to almost 90% during the initial 24 h of incubation. Albumin production increased during static culture from the value of 805.2 +/- 284.4 (ng/24 h/initial 10(6) cells) during the first days, to 2017.6 +/- 505.9 (ng/24 h/initial 10(6) cells) after 10 days of culture. In conclusion, the spongy PES membranes can be used as scaffold for hepatocyte cultivation, especially for the creation of three-dimensional environments.

Rate of synthetic oligosaccharide degradation as a novel measure of amylase activity in peritoneal dialysis patients.

BACKGROUND: Plasma alpha-amylase activity is elevated in uremic patients but lower in peritoneal dialysis (PD) patients using icodextrin in comparison to healthy controls. We studied the rate by which an exogenous oligosaccharide (maltoheptaose; G7) is degraded ex vivo by amylase in plasma from PD patients treated with glucose or icodextrin PD solutions. METHODS: Plasma amylase (pancreatic and total) activity and concentration were measured in 11 controls and in PD patients treated with glucose (n = 11) and icodextrin (n = 19). The plasma was spiked with G7 and/or synthetic amylase and the metabolites formed were measured by HPLC following incubation at 37 degrees C for 4 hours. RESULTS: The relationship between amylase activity and amylase concentration was similar in all patients and controls. The G7 degradation rate was slower in plasma from icodextrin patients but it was also reduced in patients using glucose compared with the controls, in spite of the higher amylase activity in the glucose group. Normalization (by spiking) of patient plasma with porcine amylase increased but did not normalize the speed of G7 degradation. At a given endogenous amylase activity level, the efficiency of G7 degradation was similar for both patient groups. CONCLUSIONS: An ex vivo model to study the relationship between amylase activity and the actual rate of carbohydrate (represented by G7) breakdown was developed and showed that PD patients using glucose and icodextrin degrade G7 at a slower speed than controls. This suggests that amylase-mediated carbohydrate metabolism is reduced in PD patients. Further clinical studies are needed to confirm if these findings hold true also in other groups of uremic patients with varying degrees of kidney failure, as well as in patients undergoing hemodialysis.

Peritoneal transport in peritoneal dialysis patients using glucose-based and amino acid-based solutions.

OBJECTIVE: To evaluate peritoneal transport of fluid and solutes in continuous ambulatory peritoneal dialysis (CAPD) patients using amino acid (AA)-based versus glucose-based dialysis solutions. METHODS: Using iodine-labeled human serum albumin ((125)I-HSA) as intraperitoneal volume marker, peritoneal transport was investigated in a group of 20 clinically stable patients (11 females and 9 men, age 53 +/- 15 years) on CAPD for 15 - 101 months. Two paired 4-hour dwells, one with 1.36% glucose and one with 1.1% AA dialysis solution, were performed in each patient. Intraperitoneal dialysate volume, fluid absorption rate, and diffusive mass transport coefficients (K(BD)) and sieving coefficients (S) for glucose, creatinine, urea, potassium, and total protein were estimated for each dwell study. Dwell studies with AA solution were used to estimate K(BD) values for individual AAs. RESULTS: Intraperitoneal dialysate volume was higher for AA solution in comparison with glucose solution due to the higher osmolality of the AA solution. No statistically significant difference was found for K(BD) or S for creatinine, urea, potassium, or total protein in the dwell studies with either solution, whereas K(BD) for glucose was higher with AA than with glucose solution. Mean values of K(BD) of AA were similar but with high standard deviation, reflecting inter-individual variations in peritoneal transport rate. CONCLUSION: Our results indicate that the AA peritoneal transport rate is strongly dependent on transport characteristics of the individual peritoneal membrane.

Icodextrin metabolism and alpha-amylase activity in nonuremic rats undergoing chronic peritoneal dialysis.

OBJECTIVE: To study the metabolism of icodextrin and alpha-amylase activity following daily exposure to dialysis solutions containing either glucose or icodextrin as osmotic agent in rats. METHODS: Male Wistar rats with implanted peritoneal catheters were infused twice daily for 3 weeks with 20 mL 7.5% icodextrin-based peritoneal dialysis fluid (IPDF; ICO group, n = 12) or 3.86% glucose-based peritoneal dialysis fluid (GLU group, n = 11). A 4-hour dwell study using 30 mL IPDF was performed on day 10 (D1) and day 21 (D2) in both the ICO and the GLU groups. Radiolabeled serum albumin (RISA) was used as a macromolecular volume marker. Dialysate samples were collected at 3, 15, 30, 60, 90, 120, and 240 minutes. Blood samples were drawn before the start and at the end of the dwell. RESULTS: During all dwell studies, the dialysate concentrations of total icodextrin decreased due to decrease in high molecular weight (MW) fractions, whereas there was a marked increase in icodextrin low MW metabolites. alpha-Amylase activity increased in dialysate and decreased in plasma. About 60% of the total icodextrin was absorbed from the peritoneal cavity during the 4-hour dwells. Low MW icodextrin metabolites were present in the dialysate already at 3 minutes, and maltose (G2), maltotriose (G3), maltotetraose (G4), and maltopentaose (G5) increased progressively, reaching maximum concentrations at 60 minutes. Maltohexaose (G6) and maltoheptaose (G7) were also detected already at 3 minutes but did not change significantly during the dwells. During the two 4-hour dwell studies (D1 and D2), the concentrations of total icodextrin and icodextrin metabolites and alpha-amylase activity in dialysate did not differ between the ICO and GLU groups, during either D1 or D2. No icodextrin metabolites were detected in plasma at the end of the dwells. alpha-Amylase activity in the dialysate increased six- to eightfold whereas plasma alpha-amylase activity decreased by 21% - 26% during the two 4-hour dwells in both the ICO and the GLU groups; there were no significant differences between the ICO and the GLU groups during either D1 or D2. alpha-Amylase activity in the dialysate correlated strongly with the disappearance rate of icodextrin from the peritoneal cavity during the 4-hour dwells, and with the concentrations of G2, G3, G6, and G7 in dialysate. CONCLUSIONS: The decline in the dialysate concentrations of high MW fractions and the increase in low MW metabolites of icodextrin suggest intraperitoneal alpha-amylase mediated the metabolism of icodextrin and the transport of predominantly the smaller icodextrin metabolites from dialysate. However, no icodextrin could be detected in plasma, suggesting that it was metabolized and excreted by the kidney in these nonuremic rats. In contrast to uremic peritoneal dialysis patients, chronic exposure to IPDF did not seem to further affect alpha-amylase activity or icodextrin metabolism. The much higher alpha-amylase activity in plasma and dialysate in rats than in humans explains the much more rapid metabolism of icodextrin in rats compared with peritoneal dialysis patients.

Combination of crystalloid (glucose) and colloid (icodextrin) osmotic agents markedly enhances peritoneal fluid and solute transport during the long PD dwell.

BACKGROUND: Fluid and sodium removal is often inadequate in peritoneal dialysis patients with high peritoneal solute transport rate, especially when residual renal function is declining. METHOD: We studied the effects of using simultaneous crystalloid (glucose) and colloid (icodextrin) osmotic agents on the peritoneal transport of fluid, sodium, and other solutes during 15-hour single-dwell exchanges using 3.86% glucose, 7.5% icodextrin, and a combination fluid with 2.61% glucose and 6.8% icodextrin in 7 prevalent peritoneal dialysis patients with fast peritoneal solute transport rate. RESULTS: The combination fluid enhanced net ultrafiltration (mean 990 mL) and sodium removal (mean 158 mmol) compared with 7.5% icodextrin (mean net ultrafiltration 462 mL, mean net sodium removal 49 mmol). In contrast, the 3.86% glucose-based solution yielded negligible ultrafiltration (mean -85 mL) and sodium removal (mean 16 mmol). The combination solution resulted in significantly improved urea (+41%) and creatinine (+26%) clearances compared with 7.5% icodextrin. CONCLUSION: A solution containing both crystalloid (glucose 2.61%) and colloid (icodextrin 6.8%) osmotic agents enhanced fluid removal by twofold and sodium removal by threefold compared with 7.5% icodextrin solution during a dwell of 15 hours, indicating that such a combination solution could represent a new treatment option for anuric peritoneal dialysis patients with high peritoneal solute transport rate.

The kinetic analysis of sodium and fluid transport in peritoneal dialysis.

In the article the principles of kinetic (compartmental) analysis of fluid and solute transport in peritoneal dialysis have been presented. Using results from published studies it has been shown that convective transport plays a dominant role in sodium transport. In high transport groups of patients the mass of sodium removed was the lowest because of increased fluid absorption rate. The analysis of ultrafiltration capacity loss demonstrated that several phenomena contributed to this loss.

Determination of high and low molecular weight molecules of icodextrin in plasma and dialysate, using gel filtration chromatography, in peritoneal dialysis patients.

OBJECTIVE: The aim of this study was to apply high performance liquid chromatography (HPLC) with modern gel filtration media to determine high molecular weight (HMW) icodextrin fractions and low molecular weight (LMW) icodextrin metabolites in dialysate and plasma in peritoneal dialysis (PD) patients on treatment with icodextrin, and to explore the potential relationships between these compounds, alpha-amylase activity, and glomerular filtration rate. DESIGN: Retrospective study of dialysate and plasma samples from PD patients. SETTING: Samples were collected at one PD center. PATIENTS: Blood and dialysate samples were obtained from PD patients who were subdivided into three groups: patients using only glucose-based peritoneal dialysis fluid (GPDF; GLU group, n = 23), patients studied after the first long dwell with icodextrin-based peritoneal dialysis fluid (IPDF; 1st ICO group, n = 24), and patients who were regular users of IPDF for the long dwells (ICO group, n = 9). METHODS: LMW icodextrin metabolites [i.e., maltose (G2), maltotriose (G3), maltotetraose (G4), maltopentaose (G5), maltohexaose (G6), and maltoheptaose (G7)] and HMW fractions were determined in plasma and dialysate using two different gel filtration HPLC methods. Enzymatic hydrolysis with amyloglucosidase to glucose yielded the total carbohydrate content and this was used to validate the HPLC results. alpha-Amylase activity was determined using a routine method. RESULTS: The results obtained by gel filtration HPLC yielded values of LMW metabolites and HMW fractions in plasma and dialysate in agreement with results obtained with enzymatic hydrolysis. HMW fractions were not detectable in plasma. Absorption of icodextrin from the peritoneal cavity during the long dwell (10 - 16 hours) was, on average, 39% of the amount instilled. During the long dwell, there was a relative decrease in the dialysate concentration of the largest HMW fractions (>21.4 kDa). Plasma concentration of the LMW icodextrin metabolites G2-G7 was highest in the ICO group (2.65+/-0.54 mg/mL) but also higher in the 1st ICO group (1.97+/-0.57 mg/mL) compared with the GLU group (0.52+/-0.23 mg/mL). Plasma alpha-amylase activity was significantly lower in the 1st ICO group and in the ICO group compared with the GLU group. CONCLUSIONS: Accurate analysis of HMW icodextrin fractions in dialysate and LMW icodextrin metabolites in plasma and dialysate in PD patients can be achieved by gel filtration HPLC with two different columns. This method can be used to study the complex pattern of changes in icodextrin and its metabolites in plasma and dialysate. The finding that HMW icodextrin fractions were not detected in plasma was unexpected, and differs from results of previous studies by other researchers.

Peritoneal fluid transport in CAPD patients with different transport rates of small solutes.

BACKGROUND: Continuous ambulatory peritoneal dialysis (CAPD) patients with high peritoneal solute transport rate often have inadequate peritoneal fluid transport. It is not known whether this inadequate fluid transport is due solely to a too rapid fall of osmotic pressure, or if the decreased effectiveness of fluid transport is also a contributing factor. OBJECTIVE: To analyze fluid transport parameters and the effectiveness of dialysis fluid osmotic pressure in the induction of fluid flow in CAPD patients with different small solute transport rates. PATIENTS: 44 CAPD patients were placed in low (n = 6), low-average (n = 13), high-average (n = 19), and high (n = 6) transport groups according to a modified peritoneal equilibration test (PET). METHODS: The study involved a 6-hour peritoneal dialysis dwell with 2 L 3.86% glucose dialysis fluid for each patient. Radioisotopically labeled serum albumin was added as a volume marker.The fluid transport parameters (osmotic conductance and fluid absorption rate) were estimated using three mathematical models of fluid transport: (1) Pyle model (model P), which describes ultrafiltration rate as an exponential function of time; (2) model OS, which is based on the linear relationship of ultrafiltration rate and overall osmolality gradient between dialysis fluid and blood; and (3) model G, which is based on the linear relationship between ultrafiltration rate and glucose concentration gradient between dialysis fluid and blood. Diffusive mass transport coefficients (K(BD)) for glucose, urea, creatinine, potassium, and sodium were estimated using the modified Babb-Randerson-Farrell model. RESULTS: The high transport group had significantly lower dialysate volume and glucose and osmolality gradients between dialysate and blood, but significantly higher K(BD) for small solutes compared with the other transport groups. Osmotic conductance, fluid absorption rate, and initial ultrafiltration rate did not differ among the transport groups for model OS and model P. Model G yielded unrealistic values of fluid transport parameters that differed from those estimated by models OS and P. The K(BD) values for small solutes were significantly different among the groups, and did not correlate with fluid transport parameters for model OS. CONCLUSION: The difference in fluid transport between the different transport groups was due only to the differences in the rate of disappearance of the overall osmotic pressure of the dialysate, which was a combined result of the transport rate of glucose and other small solutes. Although the glucose gradient is the major factor influencing ultrafiltration rate, other solutes, such as urea, are also of importance. The counteractive effect of plasma small solutes on transcapillary ultrafiltration was found to be especially notable in low transport patients. Thus, glucose gradient alone should not be considered the only force that shapes the ultrafiltration profile during peritoneal dialysis. We did not find any correlations between diffusive mass transport coefficients for small solutes and fluid transport parameters such as osmotic conductance or fluid and volume marker absorption. We may thus conclude that the pathway(s) for fluid transport appears to be partly independent from the pathway(s) for small solute transport, which supports the hypothesis of different pore types for fluid and solute transport.

Influence of process conditions during impulsed electrostatic droplet formation on size distribution of hydrogel beads.

In the medical applications of microencapsulation of living cells there are strict requirements concerning the high size uniformity and the optimal diameter, the latter dependent on the kind of therapeutic application, of manufactured gel beads. The possibility of manufacturing small size gel bead samples (diameter 300 microm and below) with a low size dispersion (less than 10%), using an impulsed voltage droplet generator, was examined in this work. The main topic was the investigation of the influence of values of electric parameters (voltage U, impulse time tau and impulse frequency f) on the quality of obtained droplets. It was concluded that, owing to the implementation of the impulse mode and regulation of tau and f values, it is possible to work in a controlled manner in the jet flow regime (U> critical voltage UC). It is also possible to obtain uniform bead samples with the average diameter, deff, significantly lower than the nozzle inner diameter dI (bead diameters 0.12-0.25 mm by dI equal to 0.3 mm, size dispersion 5-7%). Alterations of the physical parameters of the process (polymer solution physico-chemical properties, flow rate, distance between nozzle and gellifying bath) enable one to manufacture uniform gel beads in the wide range of diameters using a single nozzle.

Polypropylene hollow fiber for cells isolation: methods for evaluation of diffusive transport and quality of cells encapsulation.

Formulation of membrane properties is important prior the successful implantation of encapsulated cells producing therapeutically relevant compounds. The purpose of our study was to specify the methods allowing preliminary evaluation of hollow fibers (HF) chosen for immunoisolation. We have selected as estimates (1) diffusive permeability for small and large solutes, and HF cut off (in vitro), (2) histological evaluation of tissue overgrowth after sc. implantation into mice. It was found that diffusive coefficients were linearly dependent on the particle diameter except that of albumin (2-3 times higher than theoretically estimated). This discrepancy imply that for certain particles the interaction with membrane material may be significant. The histological evaluation showed that siliconized HF implanted for 105 days were accepted (there was thin fibrotic layer on the external surface of the HF, no surrounding haemopoietic cells were found). It is concluded that proposed methods for preliminary evaluation of hollow fibers chosen for immunoisolation seems to be reliable and suitable for testing diffusive permeability of each relevant cell product.

KT/V: the denominator dilemma.

The efficacy of solute removal by renal replacement therapy can be assessed by the commonly used index of KT/V. However, KT/V has a different meaning in hemodialysis (HD) and peritoneal dialysis (PD), and KT/V in HD and PD can therefore not be compared. For example, in HD one uses an instantaneous clearance K = (solute removal rate)/CB, where CB is solute concentration in blood. Thus, K is the clearance of the purification device (hemodialyzer) and in continuous ambulatory peritoneal dialysis (CAPD) it is the diffusive mass transport parameter (KBD, MTAC) but this is not used in clinical practice. Instead, in CAPD one uses a treatment clearance KT = (average rate of solute removal per treatment)/CBO, where CBO is CB at the beginning of the treatment. Whereas K is constant, KT decreases during the CAPD dwell. The current practice of using KTT/V for CAPD but KT/V for HD leads to confusion. Furthermore, T is different in CAPD (about 150 hours per week) and HD (about 12 hours per week). Finally, V, the distribution volume of the solute (usually urea), is calculated in different ways in HD and PD. V is strongly related to nutritional status and as such it is a strong predictor of survival. KT in HD, and KTT in CAPD, represents the dialysis dose and as such also a predictor of survival. This may at least in part explain why the recent Ademex study in PD patients and the Hemo study in HD patients could not demonstrate any strong impact of different levels of KT/V (KTT/V) on clinical outcome. In this review, we discuss the shortcomings of the "KT/V" concept, in particular its limited value for comparisons between dialysis efficiency in PD and HD, as well as the dilemma of using V as the denominator considering that V in itself may represent a strong predictor of outcome.

[Comparison of peritoneal transport of solutes and water during CAPD with glucose or amino acids solutions. Preliminary report]. / Porównanie transportu przezotrzewnowego czasteczek i wody podzas ciaglej ambulatoryjnej dializy otrzewnowej prowadzonej z zastosowaniem plynu glukozowego lub aminokwasowego. Doniesienie wstepne.

The aim of the study was the comparison of peritoneal transport of solutes and water during dialysis with presently used 1.1% amino acid solution in relation to 1.36% glucose solution. 20 clinically stable patients on CAPD for 50.0 +/- 27.6 months were enrolled into the study. On the basis of blood and dialysate samples taken during 4-hour CAPD, intraperitoneal dialysate volume and diffusive mass transport coefficients (KBD) for: glucose, creatinine, urea, sodium, potassium and total protein were calculated. Intraperitoneal dialysate volume was higher in the case of amino acid solution in comparison to glucose solution. The KBD values for the investigated solutes were higher when amino acid solution was used, but for glucose and sodium the KBD values were statistically significantly higher. In conclusion, the differences in transperitoneal transport of solutes and water between both solutions found in our study suggest better clinical usefulness of amino acid solution than standard glucose solution for achieving adequate ultrafiltration.