[Network form of the Kedem-Katchalsky equations for ternary non-electrolyte solutions. 8. evaluation of Pij Peusner's coefficients for polymeric membrane]

BACKGROUND

Methods of Peusner's network of thermodynamics (PNT) allow to obtain network forms of Kedem-Katchalsky (K-K) equations. The equations are the result of symmetric and/or hybrid transformation of the classic form of the K-K equations. For ternary non-electrolyte solutions, comprising a dissolvent and two solutions dissolved, the following network forms of the K-K equations may be obtained: two symmetric forms (containing Rij or Lij Peusner's coefficients) and six hybrid forms (containing Hij, Wij, Nij, Kij, Sij or Pij Peusner's coefficients).

OBJECTIVES

Using the network form of the K-K equations for homogeneous ternary non-electrolyte solutions containing Pij (i, j ∈ {1, 2, 3}) Peusner's coefficients, the objective is to calculate concentration dependences Pij and compare them to concentration dependences of Sij (i, j ∈ {1, 2, 3}) coefficients, presented in the 7th part in this paper (Polim. Med. 2014, 44, 39-49).

MATERIAL AND METHODS

In the experiment, a polymeric hemodialysis Nephrophan membrane with specified transport properties (Lp, σ, ω) was used for glucose solutions in aqueous ethanol. The method involves the PNT formalism and K-K equations for ternary non-electrolyte solutions.

RESULTS

The objective of calculations were dependences of Pij Peusner's coeffcients and Pij/Sij (i, j ∈ {1, 2, 3}) quotients within the conditions of solution homogeneity upon an average concentration of one component of solution (C1) with a determined value of the second component (C2).

CONCLUSIONS

The network form of K-K equations containing Peusner's coefficients Pij (i, j ∈ {1, 2, 3}) is a new tool that may be applicable in studies on membrane transport. Calculations showed that the coefficients are sensitive to concentration and composition of solutions separated by a polymeric membrane.

[Analysis of the membrane transport using a transformed Kedem-Katchalsky equations]

On the basis of transformed Kedem-Katchalsky equations the analysis of transport of aqueous glucose solutions through horizontally oriented polymeric membrane was occurred. Using experimentally determined membrane parameters, the resistance coefficients were calculated. Moreover, taking into account the resistance coefficients and experimentally determined volume and solute fluxes, the thermodynamic forces for homogeneous and nonhomogeneous solutions were calculated.

Experimental study on long-term exposure to a biocompatible, hypertonic, pyruvate-buffered dialysis solution

BACKGROUND

Chronic exposure to glucose and glucose degradation products (GDPs) in dialysis solutions is involved in the pathogenesis of peritoneal neoangiogenesis and fibrosis, potentially leading to encapsulating peritoneal sclerosis (EPS). High lactate concentrations may contribute to glucose toxicity by creating a state of pseudohypoxia, which stimulates the formation of various growth factors.

OBJECTIVE

To study the effects of long-term peritoneal exposure to a filter-sterilized pyruvate-buffered solution with a combination of 3 osmotic agents (amino acids, glycerol, glucose: PYRAGG) on peritoneal function and morphology.

METHODS

Rats were exposed daily for a period of 20 weeks to PYRAGG, or to a conventional heat-sterilized solution (LH), or to a filter-sterilized solution (LF), after which a peritoneal function test was done and peritoneal tissue was obtained.

RESULTS

Peritoneal solute and fluid transport characteristics at 20 weeks were similar in all groups. Fibrosis was most pronounced in the LH group compared to the others, suggesting an effect of GDPs. A marked reduction in the number of omental vessels was noted in the PYRAGG group (59% reduction compared to LH). A modest reduction (28%) was found in the LF animals. This points to a marked effect of reduced exposure to glucose.

CONCLUSIONS

PYRAGG was more biocompatible than a filter-sterilized glucose/lactate solution because it did not induce marked peritoneal abnormalities after long-term exposure. This did not lead to altered peritoneal transport characteristics. It is likely that further development of PYRAGG-like solutions will decrease the incidence of EPS.

Hyperosmolar conjunctival provocation for the evaluation of nonspecific hyperreactivity in healthy patients and patients with allergy

BACKGROUND

Tissue hyperreactivity of target organs to nonspecific stimuli is known to be an important factor in influencing the clinical picture of allergic disease.

OBJECTIVE

To identify the sensitivity and specificity of a hyperosmolar conjunctival provocation test in predicting conjunctival hyperreactivity and to relate this reactivity to the presence of ocular discomfort in subjects with and without allergy.

METHODS

In 50 healthy patients and 19 patients with allergic conjunctivitis during remission phase, symptoms of ocular discomfort triggered by nonspecific stimuli were identified and graded with a discomfort score. Subjects were then challenged with a glucose solution at increasing concentrations (from 10% to 50%). The glucose concentration that elicited 2+ conjunctival hyperemia was considered the provoking dose. The response to this hyperosmolar provocation in subjects with ocular discomfort was compared with that of asymptomatic subjects. Sensitivity and specificity of the test in predicting conjunctival hyperreactivity were analyzed.

RESULTS

Six of 50 healthy subjects and 12 of 19 subjects with allergy complained of ocular discomfort after exposure to nonspecific stimuli. The hyperosmolar provocation test discriminated between subjects with and without ocular discomfort (mean provoking dose: 39.5% +/- 5% and 47.5% +/- 5% glucose, respectively; P < .001). Forty percent glucose was the optimal threshold dose that demonstrated the highest sensitivity and specificity for prediction of conjunctival hyperreactivity. Discomfort scores were significantly related to provoking dose values (P < .05).

CONCLUSION

This study provides a standardized procedure to detect nonspecific conjunctival hyperreactivity independent of underlying atopy.

CLINICAL IMPLICATIONS

Hyperosmolar provocation test may be useful for identifying conjunctival hyperreactivity in subjects with and without allergy with a history of ocular discomfort.

Superior patient survival for continuous ambulatory peritoneal dialysis patients treated with a peritoneal dialysis fluid with neutral pH and low glucose degradation product concentration (Balance)

BACKGROUND

In recent years, laboratory and clinical research has suggested the need for peritoneal dialysis fluids (PDFs) that are more biocompatible than the conventional PDFs commonly used today. Bioincompatibility of PDF has been attributed to low pH, lactate, glucose, glucose degradation products (GDPs), and osmolality. PDFs with neutral pH and low GDPs are now available commercially. In vitro and early clinical studies suggest that these solutions are indeed more biocompatible but, as of now, there is no evidence that their use improves patient outcome.

METHODS

Using a dedicated database of over 2000 patients treated with PD in Korea, we were able to conduct a retrospective observational study comparing outcomes for incident continuous ambulatory PD patients treated with a standard, conventional, heat-sterilized PDF to the outcomes for patients treated with a novel, low GDP, neutral-pH PDF prepared in a dual-compartment, double-bag PD system (Balance; Fresenius Medical Care, St. Wendel, Germany). In an intention-to-treat analysis, patient and technique survival, peritonitis-free survival, and peritonitis rates were compared in 611 patients treated with Balance for up to 30 months and 551 patients with a standard PDF (stay . safe; Fresenius Medical Care) treated in the same era and with equivalent follow-up.

RESULTS

The patients were well matched for most relevant characteristics except older age distribution for the patients treated with the standard PDF. Patients treated with Balance had significantly superior survival compared to those treated with the standard PDF (74% vs 62% at 28 months, p = 0.0032). In a multivariate Cox regression model including age, diabetes, and gender, the survival advantage persisted (relative risk of death for Balance 0.75, 95% confidence interval 0.56 - 0.99, p = 0.0465). Modality technique survival was similarin Kaplan-Meieranalysis for both PDFs. No differences were detected in peritonitis-free survival or in peritonitis rates between the two solutions.

CONCLUSION

This study, for the first time, suggests that treatment with a novel biocompatible PDF with low GDP concentration and neutral pH confers a significant survival advantage. The exact mechanisms for such a survival advantage cannot be determined from this study. The usual criticisms of observational studies apply and the results reported here strongly warrant the undertaking of appropriately designed, randomized, controlled clinical trials.

[Streaming gravity-diffusive effect for a series of two flat polymeric membranes oriented horizontally]

In this paper the results of study flux gravidiffusive effect for a double-membrane osmotic-diffusive cell, in which series of two (Ml and M(r)), microporous and symmetrical flat polymeric membranes (Nephrophane and Cellulose IMP-1). These membranes separate three compartments (l, m, r) containing the heterogeneous and binary (aqueous glucose or ethanol solutions) or ternary (glucose solutions in 0.75 mole.l-1 aqueous ethanol solution or ethanol solutions in 0.1 mole.l-1 aqueous glucose solution) non-ionic solutions. The solution concentrations fulfil the condition Ckl > Ckm > Ckr. The inter-membrane compartment (m) consists of the infinitesimal layer of solution. The volume of compartment m and external compartment (l and r) fulfill the conditions Vm-->0 and Vl = Vr-->infinity respectively. The study of flux gravidiffusive effect for configurations A and B of the double-membrane osmotic-diffusive cell were elaborated. In configuration A solution was placed in compartment below membrane M(r) and water above membrane Ml. In configuration B solution was placed in compartment above membrane Ml and water below membrane Ml. These results are interpreted in terms of the convective instability that increases the diffusive permeability coefficients of complexes: concentration boundary layers/membrane Ml or M(r)/concentration boundary layer.

[Streaming gravity-osmotic effect for a series of two flat polymeric membranes oriented horizontally and ternary non-ionic solutions]

In this paper the results of study flux graviosmotic effect for a double-membrane system, in which two (Ml and M(r)), microporous and symmetrical flat polymeric membranes (Nephrophane and Cellulose IMP-1) separate three compartments (l, m, r) containing the heterogeneous and binary (aqueous glucose or ethanol solutions) or ternary (glucose solutions in 0.75 mole.l-1 aqueous ethanol solution or ethanol solutions in 0.1 mol.l-1 aqueous glucose solution) non-ionic solutions. In this system the solution concentrations fulfill the condition Ckl > Ckm > Ckr. The inter-membrane compartment (m) consists of the infinitesimal layer of solution. The volume of compartment m and external compartment (l and r) fulfill the conditions Vm-->0 and Vl = Vr-->infinity respectively. The calculations of flux graviosmotic effect for configurations A and B of the double-membrane osmotic-diffusive cell were elaborated. In configuration A solution was placed in compartment below membrane M(r) and water above membrane Ml. In configuration B solution was placed in compartment above membrane Ml and water below membrane Ml. These calculated results are interpreted in terms of the convective instability that increases the diffusive permeability coefficients of complexes: concentration boundary layers/membrane Ml or M(r)/concentration boundary layer.

[A pressure gravity-diffusive effect for flat polymeric membrane and ternary non-electrolyte solutions]

In this paper the pressure gravidiffusive model equation in a single-membrane osmotic-diffusive cell is elaborated. In this cell the flat, microporous and symmetric polymeric membrane so-called Nephrophane positioned horizontally separated water and binary (aqueous glucose or aqueous ethanol) or ternary (glucose in 0.2 mol.l-1 aqueous ethanol or ethanol in 0.05 mol.l-1 aqueous glucose) non-electrolyte solutions. The calculations of pressure gravidiffusive effects for the configurations A and B of the single-membrane osmotic-diffusive cell were elaborated. In configuration A solution was placed in compartment below membrane and in configuration B--above membrane. The calculated result are interpreted in terms of the convective instability that increases the diffusive permeability coefficient of complex: concentration boundary layer/membrane/concentration boundary layer.

Peritoneal solvent drag reflection coefficients are within the physiological range

Previous estimates of the peritoneal solvent drag reflection coefficient (sigma) are widely disparate; some are outside the range expected for a semipermeable membrane (i.e., between 0 and 1). We have evaluated a novel method for determining sigma in a rabbit model of peritoneal dialysis. Test solute was infused intravenously, and sequential 2-hour isotonic and hypertonic exchanges (40 ml/kg) were performed in random order. Test solute was also added to the instilled hypertonic dialysis solution to inhibit transperitoneal solute diffusion during this exchange. Eight experiments were performed with creatinine as test solute and glucose as osmotic solute, and six experiments were performed with glucose as test solute and mannitol as osmotic solute. When using isotonic dialysis solution, the dialysate/plasma concentration ratio (D/P) for both test solutes increased throughout the exchange (p < 0.001). When using hypertonic dialysis solution, D/P creatinine was initially near 1 and decreased during the 1st hour of the exchange (p < 0.05); D/P glucose (as test solute) was initially 0.82 +/- (SEM) 0.07 and did not change during the exchange. The peritoneal diffusive permeability-area product (PA) was determined by fitting a mathematical model to the time dependence of the dialysate test solute concentration during the isotonic exchange using PA as an adjustable parameter, and sigma was determined in like manner during the hypertonic exchange using sigma as an adjustable parameter (and assuming a PA value equal to that during the isotonic exchange). The creatinine PA (1.37 +/- 0.28 ml/min) was higher than that for glucose (0.62 +/- 0.07 ml/min) as expected based on their solution diffusion coefficients. Creatinine and glucose sigma values were 0.38 +/- 0.06 and 0.43 +/- 0.05, respectively. We conclude that peritoneal sigma values for creatinine and glucose are within the physiological range.