PubMed Health⌕ Search

Biomedical subjects

T Petitclerc

Publications and source records attributed to T Petitclerc.

At least 37 records · Page 2Linked to original sources
PubMed1994

[The pitfalls of the clearance concept in hemodialysis].

The "clearance concept" is rigorously defined by the physicists and bioengineers. However its extension in clinical routine of dialysis therapy is not easy, but essential also to understand the rationale on which is based the currently widely used Kt/V index. The purpose of this paper is to describe the difficulties and pitfalls encountered in measuring the clearance of a substance either provided by a dialyzer or observed in a dialyzed patient. Ambiguities in the definition of clearance may account for sometimes moot estimations of the Kt/V index.

Humans↗
PubMed1993

A model for non-invasive estimation of in vivo dialyzer performances and patient's conductivity during hemodialysis.

On-line monitoring of hemodialysis sessions requires a non-invasive estimation of the parameters concerning the patient's status and the dialyzer performances. We describe here a model based on a new method for non-invasive dialysance and patient conductivity measurements. In this technique the same probe measures alternately the conductivity at the dialysate inlet and outlet for two different dialysate conductivity values. From these data, an appropriate model allows to determine the patient's conductivity as well as the effective dialysance of ionised solutes, that is to say the dialysance corrected for recirculation. A strong correlation is evidenced between the effective dialysance measured by this method and the urea clearance measured by conventional methods (r = 0.98 for in vitro solutions; r = 0.82 in vivo situations).

Humans↗
PubMed1992

Endothelin in chronic renal failure.

The aims of the present study were to determine plasma endothelin (ET) in chronically uraemic patients, the renal clearance of endogenous ET in normal dog and man, and the effect of acute volaemic expansion on ET. The mean plasma ET concentration in haemodialysis patients was 57.5 +/- 5 pg/ml before haemodialysis and remained unchanged at 52.5 +/- 5 pg/ml after haemodialysis. They were thus significantly elevated both before and after haemodialysis (P less than 0.01) compared with plasma ET in normal subjects of 20.8 +/- 0.8 pg/ml. There was no evidence of ET clearance across the cuprophane membrane of the dialyser. Resting plasma ET values in the 15 non-dialysed uraemic patients ranged between 20 and 52.5 pg/ml (mean 38.2 +/- 2.3 pg/ml), significantly greater than those observed in controls (P less than 0.01). In CAPD patients, plasma ET was also significantly (P less than 0.01), elevated (63 +/- 10 pg/ml) when compared to controls, and similar to those observed in patients before haemodialysis. In dogs, mean ET did not diminish between the aorta and the renal vein (28.1 +/- 1 versus 28.4 +/- 2 pg/ml). In man mean ET did not significantly decline between the renal artery and the renal vein (17 +/- 3 to 13 +/- 0.8 pg/ml). In the seven healthy subjects who received 2000 ml of isotonic saline intravenously ET remained unchanged (24 +/- 2; 23 +/- 1 and 23 +/- 2 pg/ml before and 1 and 2 h after starting hydration respectively). We have thus shown that plasma ET is elevated in patients with chronic renal failure especially those on dialysis and CAPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Tumoral calcifications in hemodialysis patients: possible role of aluminum intoxication.

Uremic patients may develop extraskeletal calcifications. Among the latter, periarticular tumoral calcifications (TC) represent massive, multiloculated calcium-phosphate deposits. The aim of this report was to analyze a series of 10 cases of TC in hemodialysis patients who were admitted at the Necker Hospital between 1974 and 1988. They were all male. An increased plasma calcium x phosphorus product was observed in 8 of the 10 patients. Plasma calcium level was increased in only 2 patients. In contrast, hyperphosphatemia was a constant feature in all the patients, as was the absence of an increase in plasma alkaline phosphatase activity. Using the bone histomorphometry technique, osteitis fibrosa of mild degree was observed in 2 patients, of moderate degree in 2 and of severe degree in 2 others. Evidence of aluminum (Al) overload was found in the 8 patients in whom it was searched based on bone histomorphometry, bone histochemistry, bone Al content and increased serum Al levels either in the basal state or after a deferoxamine test. In addition, Al overload was strongly suspected in the 2 remaining patients because of prolonged exposure to Al-contaminated dialysate. Various treatment strategies, including parathyroidectomy (PTx), were undertaken that remained unsuccessful in modifying the course of TC to a significant extent. Remarkably, TC occurred for the first time after PTx in 1 patient and worsened after PTx in 2 others. In conclusion, overt secondary hyperparathyroidism appears not to be an essential prerequisite for TC development in hemodialysis patients, and PTx must not be performed in such patients on the sole basis of the presence of TC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Which index to choose for quantification of the adequacy of filtration method in the hemodialysis patient?].

On the basis of a retrospective re-analysis of the data from the National Cooperative Dialysis Study, Sargent and Gotch have proposed the normalized index KT/V as an index of the level of dialytic therapy. However the current methods of calculating KT/V are complex for routine clinical use and require great care in order to avoid major inaccuracies on the estimation of dialyzer urea clearance and the subsequent calculation of the volume of distribution of urea. As the pre to post-dialytic plasma urea ratio C0/CF is a function of dialyzer urea clearance, duration of dialysis and urea distribution volume of the patient, it might well correlate with KT/V. The simplified index I = 1.2 x ln (C0/CF) is well correlating (r = 0.9; n = 15) and well approximating (3%) with KT/V and with other indexes derived from various formulas. Consequently the use of this index is electively proposed for routine determination of the quantification of dialysis.

Humans↗
PubMed1985

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.

Humans↗
PubMed1985

[Modelling in hemodialysis. Why? How?].

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.

Body Fluid Compartments↗
PubMed1984

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.

Body Water↗
PubMed1983

[Advantage of a high-sodium hemodialysis solution: theoretical bases].

In hemodialysis, an excessive oversimplification leads to confuse the transfer direction of a given solute (patient towards dialysate or dialysate towards patient) and the direction of transmembranar concentration gradient. Applied to sodium, this confusion leads to the usual iso- or hypotonic dialysate use, in order to eliminate the patient's sodium overload. We show here how the use of a high sodium dialysate allows the elimination of the sodium overload and makes the free water clearance (approached by the Na-free water clearance) positive, which is the necessary condition to restore an hydro-electrolytic equilibrium near from the normal. That allows a disappearance of hypovolemic symptoms during hemodialysis, a better general condition and a possible increase of water intake between sessions.

Humans↗
PubMedDate not supplied

Hemolytic and uremic syndrome after heart transplantation.

Two cases of hemolytic and uremic syndrome in heart transplant recipients are reported. Among solid organ transplantations, this complication mainly occurred in renal transplantation and only 1 case was reported in heart transplantation in the literature. Cyclosporine was the only etiologic factor found. The renal outcome was severe with end-stage renal failure and no recovery of the renal function despite stopping cyclosporine, corticoids and plasma exchange.

Adult↗
PubMedDate not supplied

Duocart biofiltration: a new method of hemodialysis.

DuoCart biofiltration (DCB) is a new hemodialysis method using a dialysate with only sodium chloride and bicarbonate obtained from two separate powder cartridges (BiCart and SelectCart, Gambro, Sweden). The ionic complement is directly reinfused in postdilution mode, using one 2 L bag of a specially designed sterile solution. The adaptation of the quantity of these infused substances to their removal through the dialysis membrane is made possible by repeated measurements of ionic dialysance (D), which are automatically performed every 30 min by the Diascan module, systematically available on the Integra dialysis monitor (Hospal, Italy), and by subsequent modification of the infusion rate (Q(R)). An appropriate kinetic model was used to determine the composition of the reinfusion solution (mM: 57 K, 47 Ca, 14.5 Mg, 180 Cl), the conductivity dialysate (set at 14.8 mS/cm) and the ratio Q(R)/D (set at 1/28). This ratio is kept constant by updating Q(R) after each measurement of D. The implementation of this technique requires an Integra dialysis monitor equipped with a two-powder-cartridge dialysate generation system. Fifteen dialysis sessions were performed (duration: 213+/-38 min; blood flow: 238+/-26 ml/min; ultrafiltration rate: 16+/-6 ml/min). The per-dialytic changes of ion plasma concentrations were monitored and found to be within the predicted range. The results substantiate the feasibility of this new hemodialysis method that presents several advantages: dialysate concentrates are in powder form, an alkaline and acetate-free dialysate is used with superior dialysate biocompatibility, no precipitation of Ca and Mg carbonate occurs in the dialysate circuit, the supply of calcium and potassium is easily adapted to individual patients' needs by change in the composition of the reinfusion solution, and a calcium-free dialysate that facilitates citrate anticoagulation is used.

Bicarbonates↗