Biomedical subjects

A Werynski

Publications and source records attributed to A Werynski.

At least 19 recordsLinked to original sources

PubMed2000

Kinetic modeling of fluid and solute transport in peritoneal dialysis.

Mathematical models for fluid and solute transport during peritoneal dialysis are described. A model for the transport of the so-called volume marker enables the correct estimation of the kinetics of the intraperitoneal dialysate volume as well as the rate of peritoneal fluid absorption. On the basis of these estimations, the solute transport components (diffusion, convective solute transport with ultrafiltrate and peritoneal solute absorption) may be separated within the net solute transport using a modified version of the Babb-Randerson-Farrell (BRF) model. The diffusive mass transport coefficient and sieving coefficient are given by the model. A simplified method for the estimation of the diffusive mass transport coefficient during the so-called isovolemia period is also described and compared to the BRF modeling. The three-pore model and the distributed model, which describe the structure-function relationship for the peritoneum, are also addressed.

Dialysis Solutions↗

PubMed1999

Effect of blood perfusion on diffusive transport in peritoneal dialysis.

BACKGROUND: Diffusive transport between blood and dialysate during peritoneal dialysis is evaluated in clinical and experimental studies by the diffusive mass transport coefficient, KBD. This global parameter depends on the local diffusive characteristics of the blood capillary wall (permeability) and the tissue, as well as on the density and distribution of capillaries within the tissue. It also depends on the rate of delivery (or washout) of solutes from the tissue with blood flow, that is, on the rate of tissue perfusion. However, the role of blood perfusion in peritoneal transport has not been theoretically evaluated. METHODS: The relationship between the local characteristics of the peritoneal tissue and the global diffusive mass transport coefficient was studied using a new extended version of the distributed model for peritoneal transport, which included the effect of tissue perfusion and capillary surface area on the blood-tissue transport. RESULTS: The solute concentration profiles within the tissue were found to depend on the solute penetration depth, which is equal to the square root of the ratio of the solute diffusivity in tissue to the solute clearance from the capillary bed to tissue. It was shown that KBD might be interpreted as the dialysance of a capillary bed of a characteristic size that would be immersed directly in dialysate. A definition of the effective peritoneal blood flow (EPBF; the blood flow within the tissue layer) was formulated, and it was shown that EPBF depends on the local transport characteristics for the solute. Assuming typical values of the model parameters (known from physiological studies), the values of KBD and EPBF for urea, creatinine, glucose, and CO2 were calculated and compared with the measured values with good qualitative agreement. The transient initial increase of KBD values observed at the beginning of the peritoneal dialysis dwell was interpreted as a transient sixfold increase in tissue perfusion and a twofold increase in the capillary surface area. CONCLUSION: The distributed model can be useful as a theoretical tool for detailed physiological interpretations of changes in peritoneal transport associated with changes in peritoneal microcirculation and structure of the interstitium.

Ascitic Fluid↗

PubMed1999

A simple and fast method to estimate peritoneal membrane transport characteristics using dialysate sodium concentration.

BACKGROUND: The peritoneal equilibration test (PET) is widely used to classify a patient's peritoneal transport characteristics. However, PET is laborious and the prediction of fluid removal based on PET is generally poor. It is believed that osmosis by glucose occurs partially through transcellular water channels, resulting in sieving of sodium and decrease of dialysate sodium concentration when using hypertonic glucose dialysate. OBJECTIVE: In this study, we investigated the possibility of using dialysate sodium concentration to classify the patient's peritoneal transport characteristics. METHODS: A 6-hour dwell study with frequent dialysate and plasma sampling was performed in 46 patients using 2 L of 3.86% glucose dialysate with 131I-albumin as an intraperitoneal volume (IPV) marker. The peritoneal transport of sodium, creatinine, glucose, and fluid was evaluated. RESULTS: The dialysate sodium concentration at 240 min (D(Na240)) significantly correlated with D/P creatinine (r = 0.76, p < 0.001) and D/D0 glucose (r = -0.83, p < 0.001) at 240 min of the dwell (better than dialysate sodium concentration at any other time of the dwell). DNa240 also significantly correlated with IPV at 240 min of the dwell (r = -0.61, p < 0.001)(better than D/P creatinine and D/D0 glucose). There were significant correlations between D(Na240) and the sodium-sieving coefficient (r = 0.71, p < 0.001) and the diffusive mass transfer coefficient for sodium (r = 0.50, p < 0.001). When using D(Na240) to divide the patients into four groups, as in the PET method, no significant difference was found between the two methods. CONCLUSION: Using 3.86% glucose solution, D(Na240) can be used instead of D/P creatinine to classify patients into different transport groups. D(Na240) provides a better prediction of peritoneal fluid transport and reflects both the diffusive and convective transport properties of the membrane. As only one dialysate sample (and no blood sample) is needed, D(Na240) may offer important clinical advantages compared with PET.

Biological Transport↗

PubMed1997

A quantitative analysis of sodium transport and removal during peritoneal dialysis.

To quantitatively evaluate peritoneal sodium transport, the diffusive mass transport coefficient (KBD) and sieving coefficient (S), as well as the mass of sodium transported by diffusion (DM), by convection (CM) and by fluid absorption (AM) and the total sodium mass removed (RM) were calculated during a series of single dwell studies in CAPD patients. A six-hour dwell study was performed in 68 patients using 2 liter of 1.36% (N = 13), 2.27% (N = 9) or 3.86% (N = 46) glucose dialysis fluid with 131I-albumin as the intraperitoneal volume marker. The patients in whom the 3.86% glucose dialysis fluid was applied were further divided into four transport groups according to a modified peritoneal equilibration test: high (H), high-average (H-A), low-average (L-A), and low (L) transport. There was no significant difference in KBD nor in S for sodium among different solutions. However, the removed sodium mass (RM) was significantly higher in the 3.86% (70.5 +/- 31.5 mmol) and 2.27% (36.0 +/- 21.0 mmol) solutions as compared to that of the 1.36% (-1.8 +/- 26 mmol) solution mainly due to increased both CM and DM. In general, CM was twice as high as DM. AM substantially decreased sodium removal. Among the different transport groups, the KBD and S values for sodium were significantly higher in the H group as compared to the other transport groups (both P < 0.05). However, RM was significantly lower in the H group mainly due to higher AM. Using a 3.86% glucose solution, the D/P for sodium was found to be significantly different (but only after 120 min of the dwell) between all the different transport groups. In conclusion, sodium removal in CAPD is strongly related to the fluid removal. The ultrafiltration induced convective transport (CM) and peritoneal absorption of sodium (AM) were of similar magnitude and were twice as high as the diffusive transport (DM) and both play an important role in the peritoneal sodium balance. A D/P for sodium using the 3.86% glucose solution, especially at the end of the dwell, can be used to discriminate between different transport categories of patients. High transport patients have a poor fluid and sodium removal that are likely to affect their clinical outcome.

Biological Transport↗

PubMed1996

Paradoxes in peritoneal transport of small solutes.

Analysis of kinetic studies of peritoneal solute transport involves the need for discrimination between three transport components: diffusion, convective transport, and peritoneal absorption. The description of convective transport in standard clinical conditions of continuous ambulatory peritoneal dialysis (CAPD), as well as in isochratic measurements, has met some problems related to the paradoxical and often anomalous values of sieving coefficient, a parameter that characterizes solute drag with the flow of ultrafiltrate. A possible explanation of some of these results is the time dependence of the transport parameters, which is in contrast to their assumed steadiness. These anomalies as well as the time dependence of the transport parameters are confined more to the standard glucose-based dialysis fluid than to some alternative dialysis fluids. Furthermore, the most striking anomalies have been found for small electrolytes as well as for osmotic agents, which are applied in high, unphysiological concentrations. These solutes may be involved in the transport between intracellular and extracellular compartments within the peritoneal membrane, which phenomena are not included in the current modeling.

Absorption↗

PubMed1996

Simple models for fluid transport during peritoneal dialysis.

Peritoneal fluid transport can be predicted using different simplified formulas. To evaluate three such models, fluid transport was studied in 38 single six hour dwell studies using standard glucose 1.36% (n = 9), 2.27% (n = 9) and 3.86% (n = 20) dialysis fluids as well as amino acid 2.70% fluid (n = 8) in 33 patients on continuous ambulatory peritoneal dialysis (CAPD). Dialysate volume and the peritoneal absorption rate were measured using radioiodinated serum albumin (RISA) as a marker. The dialysate volume over dwell time curves were examined using three mathematical models of fluid transport for solutions with a crystalloid osmotic agent: Model P based on phenomenologically derived exponential function of time (Pyle, 1981), Model OS based on linear relationship between the rate of net volume change, Qv, to the difference of osmolality in dialysate and blood, and Model G based on linear relationship between Qv and the difference of glucose concentration in dialysate and blood. All these models provided a good description of the measured dialysate volume over time curves, however the descriptions with Models OS and G for glucose 3.86% fluid were slightly but significantly less precise. The coefficients of Model OS were stable in time, but the coefficients of Model G and P dependend in general on the time period used for their estimation, especially for glucose 3.86% dialysis fluid. The evaluation of dwell studies with solutions containing amino acid 2.70% (instead of glucose) as osmotic agent, using Model OS and P, showed that the transport coefficients were stable in time and both models provided equally precise descriptions. These results suggested that all three models can be used but models P and OS can be preferred for practical applications such as predictions of fluid transport with alternative cristalloid osmotic agents. Furthermore, we found that the peritoneal barrier for fluid transport may change transiently during exchanges with the standard glucose-based dialysis fluid, whereas such changes were not observed with the amino acid-based fluid. This discrepancy may be due to a different composition of the dialysis fluids, including osmotic agent, buffer and pH.

Ascitic Fluid↗

PubMed1995

Diffusive and convective solute transport in peritoneal dialysis with glucose as an osmotic agent.

To investigate possible effects of glucose concentration, dwell time, and peritoneal reabsorption on the combined diffusive and convective peritoneal solute transport, dialysate to plasma concentration ratios (D/P) and solute clearances were evaluated for 6-h peritoneal dwell studies with 1.36, 2.27, and 3.86% glucose solutions. The diffusive mass transport coefficient, KBD, and sieving coefficient, S, were estimated using the Babb-Randerson-Farrell model of peritoneal transport. Dialysate volumes over time and peritoneal reabsorption rates, KE, were assessed using radiolabeled iodinated serum albumin (RISA). The transport parameters were estimated with and without peritoneal reabsorption of solutes taken into account. To test the stability of the transport parameters throughout a single peritoneal dwell, KBD and S values were estimated for the initial 3-120 min, the final 120-360 min, and the entire 3-360 min dwell period for dialysis with 3.86% glucose solution. The transport parameters did not differ between the three dialysis fluids although clearances of small solutes were higher with the 3.86% solution. Values of KBD, but not S, were dependent on the correction for peritoneal reabsorption of solutes. Computer simulations showed that S could be estimated even with the 1.36% glucose solution. A significant change of the transport parameters, with increased values of KBD during the initial period of the dwell, was found for urea, potassium, sodium, and total protein during dialysis with the 3.86% solution. S values for urea and potassium were close to 1 during the initial period whereas unphysical (higher than 1) S values were found for the whole dwell period. The transient increase of KBD during the initial part of the dwell may reflect changes in the peritoneal barrier possibly induced by fresh dialysis fluid. In conclusion, the transport parameters KBD and S are not influenced by the concentration of glucose in the dialysis fluid. Moreover, the estimation of KBD but not of S is dependent on the assumed rate of peritoneal reabsorption. Finally, the current results challenge the assumption that KBD and S are constant throughout a peritoneal dialysis exchange.

Biological Transport↗

PubMed1995

Albumin-based solutions for peritoneal dialysis: investigations with a rat model.

To evaluate albumin, an osmotic agent for peritoneal dialysis, the peritoneal fluid and solute transport were investigated during a 4-h single cycle peritoneal dialysis with albumin-based dialysis solutions. Two different albumin solutions were used in 15 normal Sprague-Dawley rats: isotonic 7.5% albumin solution (ADS 1, n = 7) and a combined 7.5% albumin and 1.35% glucose solution (ADS 2; n = 8). A standard 1.36% Dianeal solution was used to provide control values (n = 6). The rate of the intraperitoneal volume change (Qv) was positive during the initial 90 min with ADS 2 and during the initial 60 min with Dianeal 1.36% solution but negative with ADS 1. The peritoneal bulk flow reabsorption rate, Qa, was similar in all three groups. The estimated rate of transcapillary ultrafiltration (Qu = Qv + Qa) was positive with all three solutions throughout the dialysis. With ADS 1, Qu increased gradually during the initial 90 min and then remained stable, but it decreased with ADS 2 and Dianeal 1.36% solution. Qu with ADS 2 did not differ from that with Dianeal 1.36% solution during the initial 60 min, but it was significantly higher during the latter part of dialysis. The value of Qu during the last 2 h of dialysis was 0.026 +/- 0.010 and 0.025 +/- 0.009 ml/min with ADS 1 and ADS 2, respectively, and it was significantly higher than that with Dianeal 1.36% solution (0.005 +/- 0.007 ml/min; p < 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗

PubMed1995

Theoretical description of mass transport in medical membrane devices.

The application of the one-dimensional theory of mass transport to the derivation of mathematical formulas for clearances of a variety of membrane mass exchangers, namely hemodialyzers, hemofilters, plasma separators, and the cascade filtration procedure, has been reviewed. The applied theory predicts that clearances depend approximately on fluid inlet flow rates but not on concentrations, and with constant fluid flow rates, clearances are constant. Also, the application of device clearance in kinetic modeling has been discussed.

Algorithms↗

PubMed1994

Bidirectional solute transport in peritoneal dialysis.

OBJECTIVE: Three transport components are involved in solute transport in peritoneal dialysis: diffusion, convective transport, and peritoneal reabsorption of dialysate (fluid and solutes). The relative impact of these components on measureable transport characteristics (dialysate-to-plasma concentration ratio, diffusive mass transport coefficient, unidirectional clearances) may depend on the direction of solute transport, that is, from blood to dialysate or vice versa. The application of the bidirectional characteristics for the assessment of fluid and solute transport in peritoneal dialysis is reviewed and evaluated. DATA SOURCES: Theoretical analysis as well as computer simulations were applied to discuss available data from our own studies on peritoneal transport as well as from published clinical, experimental, and theoretical studies in the same field. STUDY SELECTION: Thirty-three relevant clinical and experimental studies as well as theoretical analyses derived from the literature were reviewed. DATA EXTRACTION: Data were extracted to highlight current controversies in the literature concerning the assessment of peritoneal reabsorption rate based on transport of macromolecules, middle molecules, and small solutes. RESULTS: Peritoneal reabsorption is the main component of the transport of macromolecules infused into the peritoneal cavity, and these solutes are currently being used for the assessment of the rate of reabsorption. In contrast, diffusive transport and peritoneal reabsorption cannot be experimentally discriminated for small solutes which exhibit negligible sieving through the membrane in convective transport (i.e., solutes with sieving coefficient equal to 1). For middle molecules each transport component may be of importance and may have an independent impact on bidirectional transport characteristics. CONCLUSIONS: Middle molecules, with sieving coefficients substantially less than 1, may be applied for estimation of peritoneal reabsorption rate using bidirectional transport characteristics, as apparent diffusive mass transport coefficients or unidirectional clearances. However, an independent measurement of sieving coefficient is necessary for this method.

Absorption↗

PubMed1994

Evaluation of an experimental rat model for peritoneal dialysis: fluid and solute transport characteristics.

The aim of this study was to develop a reference model of fluid and solute transport during experimental peritoneal dialysis in rats, which would simulate the conditions of clinical dialysis in CAPD patients as much as possible. For this purpose a 4-h dialysis study was performed in 13 normal Sprague-Dawley rats with conventional glucose solutions (Dianeal 1.36% solution, n = 6 and Dianeal 3.86% solution, n = 7) and a protocol and methods like those used in clinical dwell studies. The dilution of a marker, radioactive human serum albumin (RISA), was used to determine the intraperitoneal dialysate volume with corrections for the elimination of RISA from the peritoneal cavity and sample volumes. The isovolumetric method was employed to calculate the diffusive mass transport coefficients. To compare our data with reference values in CAPD patients, the data were scaled by a factor calculated as a ratio of the dialysate volume in CAPD to the dialysate volume in the rats. In a separate series of experiments the intraperitoneal hydrostatic pressure was monitored with increasing infusion volumes. The fluid transport characteristics, described as the percentage changes of the initial intraperitoneal volume, were essentially comparable to those in CAPD patients. However, the intraperitoneal volume curves were shifted more to the left than were the reported values in CAPD patients. The scaled diffusive mass transport coefficient for urea was similar to that in CAPD patients. However, the transport of other solutes, in particular glucose, was faster in the rats than in CAPD patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Dialysate to plasma solute concentration (D/P) versus peritoneal transport parameters in CAPD.

The relationship between dialysate to plasma solute equilibration ratio (D/P) and diffusive (diffusive mass transport coefficients, KBD) as well as convective (sieving coefficient, S, and net ultrafiltration) transport characteristics were studied in clinically stable CAPD patients and in patients with loss of ultrafiltration capacity (UFC). Forty-one 6-h single-dwell studies with standard glucose-based dialysis fluids containing 1.36% (n = 9), 2.27% (n = 9), and 3.86% (n = 23) anhydrous glucose were carried out in 33 clinically stable CAPD patients. Eleven patients with loss of UFC were studied with 3.86% glucose solution. Intraperitoneal dialysate volumes were calculated from the dilution of the tracer (131I-albumin) with a correction applied for its elimination from the peritoneal cavity. KBD and S were estimated using the Pyle-Popovich-Moncrief model with aqueous plasma concentrations. A theoretical D/P curve was derived with and without taking convective transport and peritoneal reabsorption into account. The three different glucose solutions yielded D/P curves which were similar for urea and potassium. For creatinine a slower equilibration and for glucose and sodium a faster decrease in dialysate concentration were observed with more hypertonic solutions. In general, there was a strong correlation which was best at 240 min between D/P (for glucose dialysate/initial dialysate concentration, D/Do) and KBD for all solutes (except sodium), whereas the correlation between D/P and convective transport parameters was much weaker. KBD for creatinine (with 3.86% glucose solution) could be estimated (r = 0.98) from aqueous D/P using the experimental formula: creatinine KBD = -1.8 - ln (1 - D240/P)/0.1. Patients with loss of UFC due to increased diffusive transport (n = 8) could be discriminated from the clinically stable patients using KBD and D/P (or D/D0) for creatinine and glucose or D/P for sodium. However, patients with loss of UFC associated with increased peritoneal reabsorption (n = 2) could not be identified using these parameters. Theoretically derived D/P curves were in excellent agreement with measured D/P for 1.36% glucose solution and simulations were satisfactory also for the 2.27% and 3.86% solutions provided that the effect of convective transport was taken into account. The standardized peritoneal equilibration tests (PET) as proposed by Twardowski et al. [17] seems to be appropriately designed as regards duration of the dwell and the choice of glucose and creatinine as investigated solutes. Thus, PET can be recommended as a sensitive routine investigation for the monitoring of normal/abnormal peritoneal transport behaviour in peritoneal dialysis patients.

Biological Transport↗

PubMed1994

Methods for estimation of peritoneal dialysate volume and reabsorption rate using macromolecular markers.

Reabsorption of fluid and solutes from the peritoneal cavity poses several problems for the correct estimation of peritoneal dialysate volume and ultrafiltration rate with macromolecular volume markers. Although physiological mechanisms of peritoneal reabsorption (direct lymphatic absorption vs reabsorption to the peritoneal tissue) are being currently discussed, many experimental and clinical studies have demonstrated that peritoneal reabsorption of the marker is mainly a bulk "backflow" out of the peritoneal cavity. Theoretical bases for the estimation of peritoneal dialysate volume and cumulative ultrafiltration of fluid including the correction for peritoneal reabsorption are reviewed. A widely applied simplified method which, however, neglects the impact of ultrafiltration on marker concentration is also discussed. The systematic errors involved in the application of the simplified method are usually less than 10% in the standard conditions; however, in specific cases they may be much higher. Therefore, the correct method is suggested for practical applications.

Absorption↗

PubMed1993

Alternative descriptions of combined diffusive and convective mass transport in hemodialyzer.

Two alternative versions of the mathematical description of the combined diffusive and convective membrane transport in hemodialyzers were compared using the one-dimensional theory of hemodialyzers. The first version is based on the assumption of homogeneity of the membrane. The second version is a widely used "ad hoc" formulation, which can be interpreted as a description of the membrane as tighter at the dialysate side than at the blood side. Theoretical predictions of the increase of dialyzer clearance caused by ultrafiltration, as assessed by transmittance coefficient, were compared to experimental data about transport of small solutes (urea, creatinine, and sodium) as well as middle molecules (vitamin B12) in three types of hollow-fiber hemodialyzer. For one type of dialyzer, the theory assuming the homogeneous membrane yielded the correct predictions for the small solutes. For two other types of dialyzer, the alternative version of the theory was adequate. For vitamin B12, the experimental values of transmittance coefficient were between the values predicted by the two versions of the theory for all three types of hemodialyzer. Thus, the two versions should be considered as a possible adequate description of solute transport in hemodialyzers.

Membranes, Artificial↗

PubMed1993

Effect of alternative osmotic agents on peritoneal transport.

To investigate the impact of osmotic agents on solute transport in continuous ambulatory peritoneal dialysis single 6-hour dwell studies were performed in nondiabetic patients using different osmotic agents: glucose 3.86%, amino acids 2.70, and glycerol 2.50%. Diffusive mass transport coefficient (KBD) and sieving coefficient (S) were assessed for urea, creatinine, glucose, glycerol, potassium, sodium, and total protein using the Babb-Randerson-Farrell model. The estimated KBD values for small solutes were higher in peritoneal dialysis fluid based on amino acids than in both glucose- and glycerol-based dialysis solutions. S values for small solutes were higher in glucose-based peritoneal dialysis fluid than in dialysis solutions based on amino acids and glycerol. Moreover, nonphysical, i.e., out of the range 0-1, S values were obtained for urea and potassium in glucose-based peritoneal dialysis fluid and for glucose and glycerol applied as osmotic agents. No difference in the transport parameters for total protein was found between the three investigated dialysis fluids. We conclude that the composition of dialysis fluid (osmotic agent, buffer solute, pH) can change the transport characteristics of the peritoneum. Furthermore, other physiological processes besides the diffusive and convective transport can contribute to the net peritoneal transport of some solutes.

Adult↗

PubMed1993

Protein catabolic rate in patients with acute renal failure on continuous arteriovenous hemofiltration and total parenteral nutrition.

Continuous arteriovenous hemofiltration (CAVH) has been used to provide nutrition support to critically ill patients in acute renal failure (ARF). Limited information exists regarding protein needs of these patients. Nineteen postoperative patients in ARF and on CAVH and total parenteral nutrition (TPN) were studied (10 men; 9 women; mean age, 65 yr) to determine protein needs (protein catabolic rate; PCR), urea nitrogen appearance (UNA), and total nitrogen appearance (TNA). TPN was adjusted to meet the needs estimated by the Harris-Benedict and Long equations. A total of 38 24-h studies were conducted on the 19 subjects. TNA, UNA, and PCR were determined by direct measurement of body losses and calculation of body pool nitrogen changes. Patients received an average of 93.9 +/- 30.5 g of protein (1.4 g/kg) and 2,600 +/- 534 kcal/day in TPN. Mean PCR was 117.5 +/- 42.8 g/day; UNA was 18.3 +/- 6.9 g/day. TNA and UNA were strongly correlated (r = 0.99; P < 0.001). PCR was less strongly correlated with estimated protein needs (r = 0.35; P = 0.03). A regression equation was developed describing the relationship between TNA and UNA as follows: TNA = 1.895 + 0.9444 (UNA) or UNA = 0.1602 (PCR) - 0.916. On the basis of this study, CAVH permits the provision of adequate nutrition support to critically ill, unstable patients. It appears that the protein needs of patients in ARF on CAVH can be accurately estimated by determining UNA through the measurement of urea losses and urea body pool changes and by regression equations to calculate PCR.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗

PubMed1993

Peritoneal transport during dialysis with amino acid-based solutions.

OBJECTIVE: To evaluate the potential clinical role of amino acids as an osmotic agent. DESIGN: The peritoneal transport of fluid, amino acids, and other solutes was investigated during a 6-hour single-cycle peritoneal dialysis with PDA 1% versus 1.36% glucose (n = 6) or PDA 2.7% versus 3.86% glucose solution (n = 9). PATIENTS: Fifteen stable nondiabetic continuous ambulatory peritoneal dialysis (CAPD) patients. RESULTS: The fractional absorption of the osmotic agents at 6 hours was higher with PDA 2.7% versus glucose 3.86% (p < 0.005). The diffusive mass transport coefficient, KBD, calculated for a period of dialysate isovolemia was higher with PDA 2.7% versus PDA 1% for essential, nonessential (p < 0.005), and total (p < 0.05) amino acids. The intraperitoneal volume-over-time curves and KBD values for urea, creatinine, glucose, albumin, beta 2-microglobulin, and total protein did not differ between the amino acid solutions and the corresponding glucose solutions. KBD for urea was significantly higher during the dwell with PDA 2.7% versus PDA 1% (p < 0.05). Plasma amino acid concentrations increased substantially during the first 1-2 hours and then decreased gradually. Valine and methionine rose to 792% and 1119% of baseline values, respectively. CONCLUSIONS: We conclude that the peritoneal transport of fluid and investigated solutes, except amino acids, was not different with the amino acid solutions compared with the corresponding equimolar glucose solutions. However, ultrafiltration tended to be lower with amino acid solutions. Furthermore, the fractional absorption of amino acids and KBD values for amino acids was higher with PDA 2.7% versus PDA 1%, suggesting an effect of the hypertonic amino acid solution on the peritoneal membrane transport properties. Also, the hypertonic PDA 2.7% solution yielded nonphysiologically high plasma levels of several amino acids. We therefore consider this solution not to be safe enough for long-term clinical use.

Absorption↗

PubMed1992

Selective removal of cholesterol by plasmapheresis and the progression of atherosclerosis.

There is a strong correlation of plasma cholesterol levels with the risk of coronary heart diseases as shown by epidemiologic studies. This study was undertaken to evaluate the effect of plasma cholesterol lowering on the progression of atherosclerosis in the homozygous Watanabe heritable hyperlipidemic (WHHL) rabbit. The effect of cholesterol lowering, which was accomplished by thermofiltration (on-line plasma separation with plasma filtration at 39 degrees C) was evaluated by comparison between treated and untreated control groups. Thermofiltration reduced significantly the mean plasma level of total cholesterol (284 vs. 655 mg/dl, P = 0.0005) and the percent aortic area occupied by atherosclerotic plaque (15.0 vs. 44.2%, P = 0.0003). The total lipid and cholesterol contents in the aortas in the treated group were also significantly lower than those in the control group. Microscopically, thickness measurements of the lesions showed that the mean thickness of the fibrous cap and the ratio of the thickness of the intima to that of the media were smaller for the treated group than the control group. This study demonstrated the slowing or stopping of the progression of atherosclerosis by lowering the plasma total cholesterol level in WHHL rabbits.

Animals↗