Biomedical subjects

B Béné

Publications and source records attributed to B Béné.

6 recordsLinked to original sources

PubMed2006

Analysis of the optical concentration curve to detect access recirculation.

The optical blood volume curve sometimes presents either a positive or a negative rapid and reversible variation (spike) during the step of the dialysate conductivity, automatically set by the monitor for the ionic dialysance (ID) measurement. We studied whether this feature was in relation with access recirculation. Firstly, we studied if the manoeuvre of reversed position of the blood lines created the same feature in the blood volume curve. Secondly, two medical teams systematically checked for the presence of spikes and measured the access recirculation by way of an ultrasound dilution technique. The manoeuvre of reversed position of the blood lines invariably reproduced the same feature on the curve of the optical blood volume measurement in case of a recirculation greater than 20%. In the normal position of the blood lines, the 16 patients with an access recirculation greater than 20% had spikes. Spikes during ID measurement were not constant for an access recirculation between 10 and 20% and did not occur for an access recirculation of less than 10% or an undetectable one. The special spike of the optical blood volume curve occurring during the ID measurement clearly detects access recirculation. The specificity is of 100% when this modification is present all along the dialysis session for all the ID measurements and the sensitivity is 100% when the access recirculation is greater than 20%.

Arteriovenous Shunt, Surgical↗

PubMed1999

Determination of access blood flow from ionic dialysance: theory and validation.

BACKGROUND: Several noninvasive techniques have been recently developed for calculating blood flow rate of vascular access in hemodialyzed patients from the on-line measurement of recirculation ratio by injecting a saline bolus when the blood lines are reversed. Here we describe a new noninvasive method based on ionic dialysance measurements without the need of a saline bolus. METHODS: Mathematical modeling allows to calculate blood flow in vascular access (QA) from the recirculation ratio (Rrev) measured when the blood lines are reversed, without the need to stop ultrafiltration, by using the formula: QA = (QB - QF) 1 - Rrev/Rrev where QB is the blood flow at the dialyzer inlet and QF the ultrafiltration rate. Because the ionic dialysance takes recirculation into account, we tested a new method to assess QA from the measurement of ionic dialysance at normal (D) and reverse (Drev) positions of the blood lines for the same QB. Assuming the absence of access recirculation at normal position of the blood lines, mathematical modeling provides the following relationship: QA = (D - QF)Drev/D - Drev. The estimation of QA from measurement of ionic dialysance (QA-ID) was compared in 28 patients to the estimation of QA by ultrasound dilution technique (QA-US). RESULTS: The two methods were strongly correlated (QA-ID = 1.24 * QA-US, r2 = 0.86, P < 0.0001). The difference between QA-ID and QA-US was 107 +/- 387 ml/min (mean +/- SD). CONCLUSIONS: Our method provides a valuable estimation of the vascular access flow and is fully noninvasive, easy to perform (no need of bolus injection and of accurate measurement of QB) and totally inexpensive. Consequently this method is suitable for monitoring access blood flow in hemodialyzed patients in order to predict access thrombosis and to treat significant stenotic lesions before thrombosis.

Blood Circulation↗

PubMed1998

Is ionic dialysance a valid parameter for quantification of dialysis efficiency?

The on-line measurement during hemodialysis of ionic dialysance provides an estimation of urea clearance with a good and already proven correlation. Some discrepancies remain controversial, and the influence of the dialyzer membrane is still being debated. Eighty-eight measurements of ionic dialysance (ID) were performed with a Diascan module (Hospal R&D, Int., Lyon, France), 51 with cellulosic membranes, and 37 with synthetic membranes, chosen according to their surface charges. The ID was compared to the urea clearance (UK) measured from the blood (n=16) and dialysate (n=88) sides. The ID is closely correlated (r=0.91) but significantly (p < 0.01) lower than the UK by 5% (ID/UK=0.95+/-0.06). The correlation is improved by a semilogarithmic regression analysis (r=0.93). Regarding the influence of the membrane charge, a slight difference is only evidenced for UK < 180 ml/min whereby ID is closer to the urea clearance for the charged membranes (ID/UK=0.98+/-0.05 for charged membranes versus 0.95+/-0.05 for noncharged membranes, p < 0.05). The discrepancy between ID and UK could be related with the difference in the blood distribution volume of urea and that of electrolytes. The good correlation provides the major argument for ID being used as a monitoring parameter of the delivered dialysis dose. Having integrated the discrepancy between ID and UK, prescription can be guided by ID for delivering the adequate normalized dialysis dose as defined by Kt/V.

Hemodialysis Solutions↗

PubMed1995

Non-invasive monitoring of effective dialysis dose delivered to the haemodialysis patient.

Assessment of normalized dialysis dose Kt/V actually delivered to the patient carries the drawback of requiring several blood or dialysate samplings and urea concentration measurements. In order to easily quantify Kt/V, we validate here the routine implementation of an original technique for the non-invasive, on-line, and fully automatic estimation of total mean urea clearance. This estimation is obtained from the measurement by a conductivity method of the effective ionic dialysance DR, which is the dialysance of electrolytes taking into account ultrafiltration and recirculation. The observed increase in DR with ultrafiltration rate and decrease in DR with elevation of access recirculation ratio show that the estimation of DR is affected by ultrafiltration and recirculation in a consistent manner. The mean value Keff of ionic dialysance DR was compared with the value Kdc of effective urea clearance obtained by dialysate collection during 12 haemodialysis sessions. The similarity (magnitude of variation 5%) between the ionic dialysance Keff and the effective urea clearance Kdc supports the validity of the equivalence between the transfer characteristics of electrolytes and urea through the dialyser membrane. Given an estimate of the urea distribution volume V, this estimation of effective urea clearance by ionic dialysance measurement allows an on-line estimation of the normalized dialysis dose Kt/V actually delivered to the patient.

Electric Conductivity↗

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↗

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↗