**6. References**

160 Technical Problems in Patients on Hemodialysis

the breakthrough curve will be more inclined, whereas if the zone is wider, the curve will be more elongated. From Figure 6, it is possible to see that such zones differed from charcoal to charcoal according to the operational parameters established in each experiment such as initial concentration, flow and bed height. Hence, in the case of the Breakthrough curves obtained for the AC-R-G, AC-A-B and AC-R-H beds, a narrower S-shaped curved indicating a narrower mass transfer zone and, therefore, with mass transfer resistance to be considered. Nonetheless, the breakthrough curve obtained from the bed packaged with charcoal AC-B-F (Hemodialysis Center B) displayed a more elongated S-shaped curved, as seen on Figure 5, indicating a broader mass transfer zone and, therefore, little resistance to mass transfer. The supposition of the adsorption zone provides the basis for a method for a much simpler project, which makes it possible to scale up the experiments from a small laboratory scale. However, besides the Mass Transfer Zone (MTZ) concept, the estimative of parameters such as average residence time and dimensionless variance can help in the design of an

Granulated Activated charcoals are largely used in adsorption continuous processes in fixed bed for the water treatment in Hemodialysis Centers. The quality of the water used in these centers is intrinsically associated with the quality of these charcoals. As in Brazil, there are no norms, and neither, entities which control the quality of these adsorbents; it is each day more important to find the correct parameters indicators of quality. Activated charcoals used in two water treatment stations in hemodialysis centers were sampled as to assess their qualities. The Specific Surface Area (SBET) of the charcoal sampled in the water treatment stations in the two centers have presented values between 600 and 1000 m2/g approximately. SBET values around 800 m2/g are usually taken as reference value, for those who acquire such adsorbents, mainly those destined to the water treatment. From that principle, it is verified that the sampled charcoals of both Hemodialysis Centers are in accordance with this parameter, however, it was also observed, that the same charcoals have mesopores volume of (0.01-0.09 cm3/g), which are significantly below from those specified in the literature (0.40 cm3/g), thus, the charcoals from both centers must be rejected for such aim or used with caution. The blue methylene adsorption was proposed as adsorption capacity measure of activated charcoals, as this molecule has been used as to estimate the charcoal mesopores volume. It was observed that the activated charcoals which have presented higher mesopores+ secondary micropores volume have more adsorption capacity to that molecule, and, hence, may be taken as a model to estimate the referred pores region,

Regarding the first estimate of the adsorption capacity in batch of the activated charcoal in both hemodialysis centers for the cyanobacterium toxin [D-Leu1]MCYST-LR, low removal efficiencies for that toxin were observed (close to 4%), compared with the activated charcoal from sugarcane bagasse (close 99%). The behavior in the adsorption of the sampled charcoals in the hemodialysis centers is associated with its low mesopores volumes, smaller than 0.04 cm3/g, contrary to the sugarcane bagasse based-activated charcoal whose

Preliminary studies regarding the dynamic adsorption of the [D-Leu1]MCYST-LR in fixed beds of the activated charcoals in the Hemodialysis Centers have shown low adsorption capacity between 3.67 and 5.31 g/mg. Regarding the coconut shell and the sugarcane

adsorption column (activated charcoal filter).

which is important for the charcoals used in the water treatment.

mesopores volume is around 0.40 cm3/g.

**4. Conclusion** 


Specifications of the Quality of Granulated Activated Charcoal

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**10** 

*France* 

**Bioimpedance Measurement** 

**in the Kidney Disease Patient** 

*Université Henri Poincaré Nancy 1* 

Joëlle Cridlig, Mustapha Nadi and Michèle Kessler

**1.1 The problematic of hydration status in the kidney disease patient** 

certain degree of dehydration at the end of each hemodialysis session.

cellular volume; there are also unserviceable in detecting volume depletion.

Dry weight corresponds to the body weight of a person with normal extracellular fluid volume [1]. In the context of hemodialysis, dry weight is the weight reached at the end of the dialysis session by patients who will remain free of orthostatic hypotension or hypertension until the next session. Clinicians are thus obliged to estimate the appropriate dry weight each individual patient should reach at the end of a dialysis session. If this weight is underestimated, the patients are at risk of various incidents ranging from simple yawning to death. Low dry weight also carries a permanent risk of hypotension, cramps, nausea, vomiting or ischemia. If this weight is overestimated, chronic hyperhydration can cause acute events including pulmonary edema, or hypertension, but also long-term consequences affecting cardiovascular morbidity and mortality [2]. This important notion of dry weight is however quite problematic because it corresponds to a transient state, making it necessary to anticipate weight gain between two dialysis sessions and thus to reach a

The many methods proposed for measuring dry weight and body composition are still under investigation. The difficulty encountered in establishing a reliable comparative tool for measuring these parameters arises from inevitable physiological, anatomical and physical variability. Most approaches remain empirical, relying on feedback from trial

In practice, dry weight is estimated clinically [4]. Physical examination is a classic but limited tool. Solid evidence-based analysis of specific physical findings such as systolic blood pressure, orthostatic blood pressure, or the presence or not of edema is lacking. Such clinical symptoms can also be related to conditions other than a dry weight or body composition problem. Several tests have been proposed to assess the dry weight of hemodialysis patients [5]. Echocardiographic inferior vena cava diameter and biochemical markers are available but results exhibit high variability and poor correlation with extra-

Bioimpedance spectroscopy measurement has been demonstrated as a potentially useful method to determine the physiological status of living tissues [6]. Disease-related alterations are associated with variations in essential tissue parameters such as physical structure or ionic composition that can be detected as changes in passive electrical properties.

**1. Introduction** 

and error [3].

