[The future of hemodialysis in the adult]. / Les perspectives de l'hémodialyse de l'adulte.

By the year 2000, the perspectives for hemodialysis performed in adults will be oriented towards facilitation of the practice of hemodialysis as a better control of clinical symptoms observed in end stage renal failure treated by hemodialysis. Blood access is the main problem which remains to be solved. The authors describe the advantages and disadvantages of the methods presently used and give the "state of the art" of "blood access" prosthesis. Almost all symptoms encountered in renal failure patients treated by hemodialysis can be efficiently treated. Hypotensive drugs usually reduce hypertension which resists adequate treatment by hemodialysis. Most of the symptoms of osteodystrophy can be avoided by adequate diet associated with the prescription of vitamin D analogs. Nevertheless, the prolongation of hemodialysis treatment duration over 7 years has led to the apparition of destructive arthropathies which are very painful and handicapping. They are related to amyloid deposit of beta 2-microglobulins. Progress in hemodialysis technics and a better control of uremic symptoms allow application of this treatment at all ages of life. The authors examine specific problems concerning school-aged teenagers and aged persons. They show that results already achieved allow a daily treatment of these patients. This is a first step for the generalisation of this procedure to all patients and its advantages are described. Improvement of hemodialysis technics for the year 2000, as can be expected, mainly depends upon progress in knowledge of biocompatibility parameters between materials used in the artificial kidney and patients tissues, mainly blood vessels.

Toward dialysis "a la carte".

From the very beginning, the artificial kidney postponed the death of patients with end-stage renal failure. For years, owing to the performance of the machine, the patient was obliged to follow a severe diet in order to maintain good humoral and circulatory status. Now technological improvements allow "dialysis à la carte," whereby each individual achieves a better clinical status. The next step will be automation of the procedure to improve its security, mainly for dialysis performed at home.

[Retinal complications in diabetics with renal failure]. / Complications rétiniennes du diabétique en insuffisance rénale.

The following conclusion, are based on this series of 27 patients, all diabetics with end-stage renal failure: All, except one, with both diabetes and nephropathy exhibited retinopathy. Retinopathy, its severity and the prevalence of complications are primarily related to the evolution of diabetes, whatever the type and severity of the nephropathy, and independent of the presence or severity of hypertension. Good glycemia control did not induce efficient prevention of retinopathy. In insulin-dependent diabetic patients, the type of insulin used had no influence on the evolution or severity of the retinopathy. The duration of diabetes and the beginning in childhood are the major factors for complications risks.

The current status and future of the artificial kidney.

The use of the artificial kidney can presently be extended to almost all patients with end-stage renal failure. To reduce the cost of treatment, technological choices have to be made. These are always a compromise between cost and adequacy. The liberty obtained by technical improvements to perform a dialysis "à la carte," depending on patient and doctor wishes, is one of the main characteristics of the present status of hemodialysis.

Clinical validation of a predictive modeling equation for sodium.

Changes in plasma sodium (Na) concentration during hemodialysis were predicted by changes in Na concentration of the dialysate at equilibrium with the plasma, according to the formula C't = CD - (CD - C'0) [(V0 - QFt)/V0]A/QF, where C'0 and C't are the Na concentration of the dialysate at equilibrium with the plasma at times 0 and t, respectively; QF is the ultrafiltration flow rate; V0 is the initial total body water; and CD is the Na dialysate concentration. This modeling involves only one parameter, A, which is the effective sodium dialysance and depends on the dialyzer, the QF, the plasma water flow rate, and the actual Donnan coefficient. Parameter A was evaluated after 1 h of dialysis. Seven routine 4-h dialysis sessions were performed in which the Na concentration of dialysate at equilibrium with the plasma was measured at varying times. The mean (+/- SEM) difference between predicted and measured values was delta C = 0.5 +/- 0.2 mmol/L. These data support the validity of the model that allows the monitoring of Na dialysate concentration to obtain a prescribed Na plasma concentration at the end of a dialysis session.

[Modelling in hemodialysis. Why? How?]. / Modélisation de l'hémodialyse. Pourquoi? Comment?

It is an imperative necessity to adapt dialysis therapy patient to patient. This adaptation of dialysis procedure requires appropriate representation of water and solute exchanges. Kinetic modelling of hemodialysis was investigated in this respect. The goal of kinetic modelling is either to estimate one or several biologic parameters which are not easily measurable or to reach a prerequisite optimal physiologic state for a given patient. Constructing a model implies a physiological conception of solute and water exchanges that allows a definition of biologic parameters concerned. Mathematic equations only translate quantitatively water and solute transfers. A suitable model is in agreement with experimental data, and the best is the simplest. Therefore the capital point resides in the choice of assumptions which determine the model's precision and complexity. This review also outlined the limits of kinetic modelling which allows neither the determination of the best target nor the "a posteriori" justification of assumptions.

Sodium modeling during hemodialysis: a new approach.

Sodium volume modeling during hemodialysis encounters several difficulties. First, the actual sodium distribution volume is the extracellular water, whereas the ultrafiltration flow reflects the variation of total body water. Thus, a two-pool model must be considered. This will complicate the model by increasing the number of parameters and boundary conditions. An alternative is to consider the total body water as the apparent distribution volume of loaded or removed sodium, which leads to a single-pool model. Second, convective sodium transfer induced by ultrafiltration is not negligible compared with diffusive sodium transfer. Therefore, sodium transfer modeling must simultaneously take into account the diffusive and the convective part, with the coupling part related to both processes. Third, the Donnan effect due to nondiffusible anionic plasma proteins modifies the sodium transfer through the membrane. Adequate sodium volume modeling should be a compromise between oversimplification, resulting in discrepancies between calculated values and experimental data, and overcomplexity, involving a great number of parameters and boundary conditions, which leads to a model unsuitable for clinical application. A single-pool model is proposed with only one parameter that is estimated during the first period of the hemodialysis session.

Semi-automated determination of the uremic toxin "b4-2".

A semi-automated two-stage chromatographic system is described for use in evaluating neurotoxin b4-2 in body fluids of uremic patients and healthy subjects. The only manual step is the injection, thus decreasing the risk of operator error inherent in the previous manual method (Clin Chem 29: 703-707, 1983) and concurrently improving CV from 9% to 6.4% as measured during a 16-month period.

Drug interaction in middle molecule analysis, with special reference to acetylsalicylic acid.

Concerning the middle molecules in uremia and other diseases, the potential artifact that can impede an accurate quantitation of middle molecules and that is related to the absorption of a very commonly used drug, namely aspirin, is discussed. Peak 7c and peak b 4-2 are two different middle molecules separated by gel permeation chromatography followed by anion-exchange chromatography. Oral ingestion of acetylsalicylic acid modifies the chromatographic pattern of the middle molecule fraction in normal subjects and uremic patients. Peak 7c is increased in the urine of healthy subjects, whereas this is not the case for peak b 4-2: With the b 4-2 technique, ingestion of acetylsalicylic acid produces a higher peak b 5. This is consistent with the previous demonstration that peak 7c was eluted as peak b 5. Structural analogies between salicylate metabolites and orthohydroxyhippuric acid beta-glucuronate (i.e., the main component of peak 7c) could explain this drug-related artifact.