Table 1 - uploaded by Antonio Santoro
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-Conductivity (mS/cm) of NaCl, KCl, CaCl 2 , MgCl 2 samples at the different concentration (4.375-280 mEq/l), before and after treatment with the ion-exchange resin.
Source publication
Sodium measurement during hemodialysis treatment is important to preserve the patient from clinical events related to hypo- or hyper-natremia Usually, sodium measurement is performed through laboratory equipment which is typically expensive, and requires manual intervention. We propose a new method, based on conductivity measurement after treatment...
Contexts in source publication
Context 1
... water (18.5 MΩ × cm resistivity, Millipore MilliQ Element system, USA) and sodium chloride (NaCl, >99.5%, Sigma-Aldrich, Italy) was used to prepare a 500 ml sample of NaCl solution at 280 mEq/l, a concentration value certainly including the highest physiological plasma values (being twice the typical value). Afterwards, through dilution process, we obtained other six samples at lower concentrations, reaching the typical concentration values of plasma potassium and calcium : 140, 70, 35, 17.5, 8.75, 4.375 mEq/l (see Table 1). ...
Context 2
... conductivity of the NaCl samples (with concentration from 280 to 4.375 mEq/l) is reported in Table 1. Conductivity increased linearly with the ion concentration. ...
Context 3
... increased linearly with the ion concentration. Similar trend was shown by the KCl, CaCl 2 , MgCl 2 samples (Table 1). ...
Citations
... An accurate and effective in-situ concentration measurement device is required to control the CSD based on supersaturation control. In-situ measurement methods mainly include the use of a conductometer [24][25][26], pH-meter [27][28] or spectrometer [29][30]. Table 1 provides an overview of the commonly applied tools for measuring the solution concentration in a crystallization process. ...
... Roberto et al. [60] realised the on-line monitoring of a solute concentration based on conductivity measurements and established a calibration model between the solution concentration and conductivity within the entire operating range. Tura et al. [26] used the conductivity method to measure the sodium content of a dialysate. Vallière et al. [65] used the standard non-linear Kalman filter method to estimate the concentrations of reactants and intermediate products on-line, and verified the estimation results by measuring the solution concentration using the on-line conductivity method. ...
Measuring the solution concentration of processes for product quality control in industrial crystallization processes is a hot topic. In recent years, with the development of process analysis technology, various innovative measurement technologies for different situations and operating conditions have been developed. This paper systematically reviews the research on various solution concentration measurement technologies that have been developed for the crystallization process. These measurement technologies are divided into off-line, at-line, on-line, and in-situ methods based on their measurement modes and principles. The measurement principle, advantages, disadvantages, application field, and development status of each of the existing measurement technologies are illustrated in detail, with a particular focus on measurement methods based on spectroscopy technology, which are very popular for crystallization processes. In addition, this paper presents the problems of solution concentration measurement technology and points out future research directions.
... To avoid possible contamination of a sample induced by a sensing system, in some applications it is essential to perform contactless measurements. An example of such an application is the continuous in-line monitoring of blood conductivity as a measure of the sodium concentration of blood serum [1][2][3][4][5][6]. Such monitoring is particularly useful for critically ill patients in intensive care units with severe dysnatremia [7][8][9]. ...
Certain applications require a contactless measurement to eliminate the risk of sensor-induced sample contamination. Examples can be found in chemical process control, biotechnology or medical technology. For instance, in critically ill patients requiring renal replacement therapy, continuous in-line monitoring of blood conductivity as a measure for sodium should be considered. A differential inductive sensing system based on a differential transformer using a specific flow chamber has already proven suitable for this application. However, since the blood in renal replacement therapy is carried in plastic tubing, a direct measurement through the tubing offers a contactless method. Therefore, in this work we present a differential transformer for measuring directly through electrically non-conductive tubing by winding the tube around the ferrite core of the transformer. Here, the dependence of the winding type and the number of turns of the tubing on the sensitivity has been analyzed by using a mathematical model, simulations and experimental validation. A maximum sensitivity of 364.9 mV/mol/L is measured for radial winding around the core. A longitudinal winding turns out to be less effective with 92.8 mV/mol/L. However, the findings prove the ability to use the differential transformer as a truly contactless sensing system.
... Therefore, this measurement method has potential in biotechnology and medical technology for the contactless determination of biomass within single-use bioreactors [1,18] or for obtaining tissue information [19][20][21][22][23]. In addition, the differential transformer approach is investigated with respect to continuous in-line monitoring of the sodium concentration in human blood, by measuring the blood plasma conductivity, mainly influenced by the sodium concentration [24][25][26][27]. Continuous monitoring of plasma sodium concentration is particularly important in continuous renal replacement therapy, especially in patients with severe dysnatremia, since both a large deviation from the physiological plasma sodium level [26,[28][29][30] and a rapid change in the concentration can lead to dangerous complications such as central pontine myelinolysis [31,32]. ...
The electrical and dielectric properties of liquids can be used for sensing. Specific applications, e.g., the continuous in-line monitoring of blood conductivity as a measure of the sodium concentration during dialysis treatment, require contactless measuring methods to avoid any contamination of the medium. The differential transformer is one promising approach for such applications, since its principle is based on a contactless, magnetically induced conductivity measurement. The objective of this work is to investigate the impact of the geometric parameters of the sample or medium under test on the sensitivity and the noise of the differential transformer to derive design rules for an optimized setup. By fundamental investigations, an equation for the field penetration depth of a differential transformer is derived. Furthermore, it is found that increasing height and radius of the medium is accompanied by an enhancement in sensitivity and precision.
... Such a differential transformer with fixed ferrite core can be used for determining the biomass in a bioreactor, the tissue properties or for continuous monitoring of blood properties -e.g. the sodium concentration during the dialysis treatment [9][10][11][12][13][14]. [15] has even shown the possibility of measuring directly through a tubing, making it very promising for applications such as continuous and contactless monitoring of sodium in the blood during dialysis treatment. The sodium concentration measurement in blood is realized via blood conductivity measurement, since sodium has the strongest impact on the plasma conductivity (therefore the measuring frequency must be below the β-dispersion, which is at about 1 MHz) [16][17][18][19][20][21][22][23]. In order to achieve high sensitivity, it is an advantage to place the primary coil as close as possible to the sample, as this causes the sample to be penetrated strongly by the primary magnetic flux, and thus high eddy and displacement currents are induced in the sample. ...
... However, these equations do not consider the different ionic compositions of dialysis concentrates. Tura et al. [13] found conductivities of 12.93 and 15.92 mS/cm for a 140 mmol/L sodium chloride or potassium chloride solution, respectively. Therefore it is not surprising that the three dialysates with different sodium concentrations (138, 140 and 142 mmol/L) and different ionic compositions may produce the same conductivity of 13.88 mS/cm (Table 1). ...
... The hemodialysis machine maintains the effective value of NaDial,In(t) within clinically acceptable boundaries of the value set by the operator. Due to the general properties of electrolyte solutions [30], and the fact that sodium is the most concentrated electrolyte in plasma and dialysate, a good correlation can be found between the two fluids' electrical conductivity and sodium concentration [31], [32]. This assumption is exploited in some of the design choices below. ...
Objective:
Non-invasive sensing and reliable estimation of physiological parameters are important features of hemodialysis machines, especially for therapy customization (biofeedback). In this work, we present a new method for joint estimation of two important hemodialysis-related physiological parameters: relative blood volume and plasma sodium concentration.
Methods:
Our method makes use of a non-invasive sensor setup and of a mathematical estimator. The estimator, based on the Kalman filter, allows to merge data from multiple sensors, newly-designed as well as on-board, with modeling knowledge about the hemodialysis process. The system was validated on in-vitro hemodialysis sessions using bovine blood.
Results:
The estimation error we obtained (0.97±0.73% on relative blood volume and 0.47±0.19 mM on plasmatic sodium) proved to be comparable with that of reference data for both parameters: the system is sufficiently accurate to be relevant in a clinical context.
Conclusion:
Our system has the potential to provide accurate and important information on the state of a patient undergoing hemodialysis, while only low-cost modifications to the existing on-board sensors are required.
Significance:
Through improved knowledge of blood parameters during hemodialysis, our method will allow better patient monitoring and therapy customization in hemodialysis.
... Because the conductivities of single ions cannot be measured independently of their counter ions, the conductivities of KCl and NaCl solutions have to be used instead. σ K /σ Na depends only slightly on the actual ion strength and can be deduced from in vitro measurements: Tura et al. (32) found conductivities of 12.93 and 15.92 mS/cm, for a 140 mmol/L sodium chloride or potassium chloride solution respectively. This leads to σ K /σ Na = 1.231. ...
Restoring and controlling fluid volume homeostasis is still a challenge in contemporary end‐stage kidney disease patients treated by intermittent hemodialysis (HD) or hemodiafiltration (HDF). This primary target is achieved by ultrafiltration (dry weight probing) and control of intradialytic sodium transfer (dialysate‐plasma Na gradient). The latter task is mostly ignored in clinical practice by applying a dialysate sodium prescription uniform for all patients of the dialysis center but unaligned to individual plasma sodium levels. Depending on the patient’s natremia, a positive gradient gives rise to intradialytic diffusive sodium load and postdialytic thirst. On the contrary, a negative gradient may cause unwanted diffusive sodium removal and intradialytic symptoms. To overcome these challenges, a new conductivity‐based electrolyte balancing algorithm embedded in a hemodialysis machine with the aim to achieve “zero diffusive sodium balance” in HD and online HDF treatments was tested in the form of a prospective clinical trial. The study comprised two phases: a first phase with a conventional fixed‐sodium dialysate (standard care phase), followed by a phase with the electrolyte balancing control (EBC) module activated (controlled care phase). The results show a reduction in the variability of the intradialytic plasma sodium concentration shift, but it is overlain by a small but statistically significant increase in the mean plasma sodium levels. However, no clinical manifestations were observed. This sodium load can be explained by the design of the algorithm based on dialysate conductivity instead of sodium concentration. Furthermore, the increase in plasma sodium can be corrected by taking into account the potassium shift during the treatment. This study showed that the EBC module incorporated in the HD machine is able to automatically individualize the dialysate sodium to the patient’s plasma sodium without measuring or calculating predialytic plasma levels from previous laboratory tests. This tool has the potential to facilitate fluid management, to control diffusive sodium flux, and to improve intradialytic tolerance in daily clinical practice.
... Correlation accounts for the presence of offset and gain between the 2 compared variables, but the high estimated R 2 value could only be obtained in the case of very similar time dynamics. Values of the regression coefficients are similar to values reported in the literature for the relationship between sodium concentration and conductivity in dialysate: for example, Tura et al (35) reported σ Dial = 0.08•Na Dial + 2.87. The value of the obtained regression slope, 0.092 (mS/cm)/mM, and the presence of a 1.068 mS/cm offset can be explained by the influence of ions other than sodium on total conductivity, as already mentioned in the Methods section. ...
Introduction:
Hollow fiber models describe the exchange of solutes between blood and dialysate across the membrane of a single fiber of the hemodialysis filter (hemodialyzer). This work aims to develop a new approach to simulate the solute exchange in a hollow fiber in a dynamic and realistic way. Sodium was chosen as our solute of interest due to its importance in hemodialysis as an osmotic regulator.
Methods:
A 2-dimensional (2D) hollow fiber model based on the finite element method (FEM) is coupled to a simple blood pool model to dynamically update the concentration of the solute entering the dialyzer. The resulting coupled model maintains the geometrical detail of the 2D fiber representation and gains a dynamic, blood-side inlet solute concentration. In vitro dialysis sessions were carried out for model validation, by implementing a combination of blood volume loss and/or sodium concentration steps. Plasmatic sodium concentration was recorded by blood gas sampling. Dialysate inlet and outlet conductivities were continuously recorded.
Results:
Simulated plasmatic sodium concentration was compared with data from the blood gas samples. A mean error of 1.76 ± 1.03 mM was found for the complete dataset, along with a 3.87 mM maximum error. The simulated outlet dialysate sodium concentration was compared with the recorded outlet dialysate conductivity: a very high correlation was found on the whole dataset (R2 = 0.992).
Conclusions:
Coupling our FEM hollow fiber model to a simple blood pool model proved to be an effective approach for dynamical analysis of the properties of the hemodialyzer.
... Apart from possible accuracy problems, the main limitations in the use of a traditional approach for glucose determination are that (a) consumables are typically required, possibly for each measure: if the measurement is performed several times during the dialysis session, this may result in a relevant expense; (b) in any case, the measurement is discontinuous; thus some possible rapid glucose changes (e.g., leading to a hypoglycemic condition) may not be revealed promptly; (c) for every measure, the action of an operator (nurse or similar figure) is required to get the sample, and this again may have effects on the cost of the dialysis session. It should be noted that sometimes the sample (plasma ultrafiltrate solution, or dialysate) is collected for measurements of several compounds, including glucose, through a hemogas analyzer [22]; thus the need of the operator action could not be attributed to glucose determination exclusively. At any rate, limitation of discontinuous determination remains. ...
The measurement of glycemia in subjects with renal failure, thus treated with hemodialysis, or peritoneal dialysis, is clinically relevant, since glucose levels may influence the determination of other solutes, such as creatinine, as well as some ions, such as sodium, whose degree of removal during dialysis sessions should be controlled carefully. Also, glucose levels should be controlled to avoid possible events of hypoglycemia during the treatment, especially in diabetic subjects. Indeed, even cases of hypoglycemic coma are documented. The glucose measurement during the dialysis treatment can be performed with different sensors and technologies: for instance, with traditional glucose meters, with instruments for continuous glucose monitoring, or with optical sensors. The aim of this review study was to analyze these different approaches and briefly discuss possible advantages and limitations.
The individualization of dialysis treatment using a
customized dialysate composition usually requires a continuous measurement
of electrolytes and urea in blood. The current practices are spot
measurements of blood samples either with blood gas analyzers or in the
laboratory, involving considerable personnel effort. Furthermore, the
measured values are time delayed and not available in a continuous
fashion. In this paper we investigate an in-line concept for continuous
monitoring of important blood parameters such as sodium, potassium, calcium
and urea concentrations in blood serum using ion-selective electrodes. This
concept is evaluated in a preclinical study with human packed red blood
cells as a test medium over a period of 7 h. It has been shown that the
electrolytes can be well monitored. In addition, we present first
measurements with ion-sensitive field-effect transistors in a
miniaturized sensor assembly. Therefore, new low-cost electronics for such
ion-sensitive field-effect transistors have been developed.
