**3.1 Development**

296 Technical Problems in Patients on Hemodialysis

system and cause leucopenia (Rousseau et al., 1999). Biocompatibility of regenerated cellulose dialyzer membranes was tentatively improved by the chemical modification of the hydroxyl groups, e.g., by acetylation to obtain tri-acetate cellulose, or by adding polyethylene glycol (PEG) chains to obtain PEG-grafted cellulose. Another and more successful approach was the de novo development of synthetic polymer membranes such as polysulfone or polyether sulfone membranes with no bio-incompatible groups in their chemical structures (Bowry, 2002). At present, high-flux synthetic membranes are more frequently used, and represent a cost-effective solution with proven clinical superiority

Antioxidants such as vitamin C, vitamin E, and glutathione have been used as oral supplements to alleviate HD-induced oxidative stress (Galli and Azzi, 2010). The clinical course of chronic kidney disease (CKD) includes a progressive decrease in the levels of blood antioxidants such as vitamins C, vitamin E, and glutathione. As a result, CKD patients who undergo regular HD treatment show severe deficiencies, particularly of water-soluble antioxidants (such as vitamin C). Few studies, however, provided clear evidence of the clinical advantage of oral antioxidants. The most convincing evidence was obtained from the randomized clinical trial on vitamin E supplementation in HD patients. This trial, known as SPACE study (Boaz et al., 2000), showed a significant reduction (54%) of the primary endpoint variable (a composite variable including myocardial infarction, ischemic stroke, peripheral

vascular disease, and unstable angina) and 70% reduction in myocardial infarction.

**2. Cellulose-based vitamin E-bonded dialyzer membranes** 

One of the most original approaches for antioxidant therapy in HD involved the use of vitamin E as a lipophilic modifier of the surface of the dialysis membrane. The bonded vitamin E on the surface of the dialyzer membrane is expected to reduce the production of reactive oxygen species (ROS) at the site where blood cells are exposed to the dialyzer membrane, thereby providing the blood cells with antioxidant protection in a timely and targeted manner. Two generations of vitamin E-bonded dialyzers based on this concept, namely, cellulosic- and polysulfone-based membrane dialyzers, have been successfully developed and launched in the market over the last 2 decades. This chapter provides a review of the literature and a critical examination of the available clinical data on vitamin E-

In 1990, cellulose-based vitamin E-bonded dialyzer membranes (Excebrane) were developed and introduced into the market by Terumo Corporation. The base membrane was made of regenerated cellulose hollow fiber, and the surface of the hollow fiber was covalently modified by hydrophilic polymers as well as by oleic alcohol. Vitamin E (-tocopherol) was then bonded to oleic alcohol via hydrophobic interaction. Sasaki et al., 2000, reported the outline of the production process as well as the results of *in vitro* and *in vivo* studies on Excebrane, which showed much better biocompatibility than the original regenerated cellulose membrane.

Early trials using Excebrane indicated that its use would have positive clinical effects (Galli, 2002). The potential therapeutic effects of using this membrane in HD were reduction of oxidative stress and inflammation. Cardiovascular endpoints were investigated in several small clinical trials and in a meta-analysis of 14 peer-reviewed articles by Sosa et al., 2006; these studies concluded that Excebrane treatment was associated with a significant decrease in

over cellulosic membranes (Krane et al., 2007).

bonded dialyzer membranes.

**2.1 Development** 

**2.2 Clinical outcomes** 

Synthetic membrane dialyzers have been developed by many manufacturers in the past decades to achieve higher depurative and biocompatibility standards. Polysulfone has shown better performance among these synthetic biomaterials; as a result, it has become popular in clinical practice (Bowry, 2002). In order to achieve the synergistic effect of the biocompatibility of synthetic membranes and the antioxidant activity of vitamin E, polysulfone-based vitamin E-coated membranes were developed and introduced in the market in 1998. These dialyzers were initially developed by Terumo Corporation; subsequently, they were produced using a new technique and are now manufactured by Asahi Kasei Kuraray Medical Co. Ltd., with the membrane name of VitabranE. Preliminary *in vitro* analyses on these membranes were reported by Sasaki, 2006; the antioxidant capacity of VitabranE was recently confirmed and quantified by Floridi A, et al., 2009, by means of *in vitro* re-circulation tests carried out on mini-module dialyzers. These tests, which used an unbiased procedure, showed that at least one-third of the vitamin E present on the membrane participates in the one-electron transfer reaction with transition metals. This reaction, together with scavenging of peroxyl radicals, characterizes the antioxidant mechanism of vitamin E and is of putative relevance in its biological function.

#### **3.2 Improvement of anemia**

On the basis of the early evidence obtained in the Excebrane studies described in section 2.2, VitabranE was proposed as a more biocompatible dialyzer membrane to achieve a better control of anemia in HD patients. This aspect was investigated in clinical trials that

Review of the Effectiveness of Cellulose-

et al., manuscript in preparation).

and Polysulfone-Based Vitamin E-Bonded Dialysis Membranes 299

Andrulli et al., 2010. In this study, these protein-damaged markers were investigated as oxidative and carbonyl stress indices associated with the correction of ERI. Although IL-6 and CRP levels were not affected, the 2 indices showed better control in the patients receiving with VitabranE than in those receiving treatment with polysulfone dialyzer (Galli

Vitamin E-bonded dialyzer membranes were originally developed with the aim of reducing oxidative stress. As shown in the section 2.2, lowered lipid peroxidation was observed in clinical trials with Excebrane, a cellulose-based vitamin E-bonded membrane. In the case of VitabranE, 2 studies were conducted, considering LDL oxidation as an end point. Morimoto et al., 2005, reported that the 15 patients who received 6 months of treatment with VitabranE showed significant reduction in the levels of asymmetric dimethylarginine (ADMA), malondialdehyde low density lipoprotein (MDA-LDL), and oxidized low density lipoprotein (Ox-LDL). The levels returned to baseline when the membrane was changed to a polysulfone dialyzer membrane. In a matched control group, patients treated with polysulfone dialyzers showed no change in ADMA, Ox-LDL, and MDA-LDL levels during the entire treatment period of 18 months. The other report from Calò et al., 2011, showed that VitabranE improved the levels of inflammation markers and also reduced plasma levels

Intradialytic hypotension (IDH) is a common clinical trait in HD patients. Matsumura et al., 2010, conducted a pilot study to assess the effectiveness of VitabranE in improving IDH. Eight IDH patients who had been receiving HD with conventional dialyzers were switched to VitabranE dialyzers, and intradialytic blood pressure (BP) was monitored regularly for 10 months. The results showed that hypotension, monitored during the session by measuring systolic BP (SBP), diastolic BP (DBP), and pulse pressure (PP), improved after changing the dialyzer membrane. Moreover, after 8 to 10 months, SBP recorded before dialysis was significantly lower than that at baseline, which suggests a stable improvement in the

In a recent report, Aoun et al., 2010, described the potential clinical advantages of VitabranE in anticoagulant management. In an observational trial, these authors evaluated the minimum requirement of low molecular weight heparin (LMWH) in pediatric dialysis patients. Seven children and adolescent patients received HD with VitabranE dialyzer and their LMWH dose was decreased every week without any other change in the clinical management; the findings of this study consistently indicated a lower requirement of anticoagulants, which may help

The available literature suggests that vitamin E bonding on the cellulosic membrane Excebrane can reduce oxidative stress, as assessed by the levels of lipid peroxidation markers, and improve laboratory indices of inflammation and uremic anemia. The newly developed synthetic polysulfone-based dialysis membrane VitabranE appears to produce even more relevant clinical advantages as it is a homologue of most widely used synthetic membrane dialyzers. Randomized studies carried out in the past few years, which have

of Ox-LDL, which was evaluated by enzyme-linked immunosorbent assay.

**3.5 Improvement of intradialytic hypotension** 

**3.6 Anticoagulation management** 

**4. Conclusion** 

vascular compliance to intra- and inter-dialysis control of BP.

reducing bleeding problems and simplifying post-dialysis hemostasis.

compared VitabranE with polysulfone membranes. A pilot study by Andrulli et al., 2010, carried out with a 2-arm randomized controlled design showed that 8-month treatment with VitabranE decreased the erythropoiesis-stimulating agent (ESA)–resistance index (ERI); ERI is calculated as the ratio between ESA dosage (IU/kg/w) and hemoglobin levels (g/dL). In the primary analysis, ERI showed no significant deference between the groups treated with VitabranE and the control polysulfone membrane. However, in the secondary analysis where the baseline parathyroid hormone (PTH) and serum vitamin E levels were included as covariates, the ERI was significantly decreased in the group treated with VitabranE than in the group treated with the control polysulfone membrane. Therefore, the authors concluded that VitabranE membranes have potentially beneficial effects on ERI of HD patients. This conclusion was confirmed in another and more recent multicenter study by Panichi et al., 2011. In this report, a crossover design was employed and 62 HD patients from 13 dialysis units were randomized to receive treatments with VitabranE or polysulfone dialyzer controls. The patients were studied for 2 steps of 6 months in each treatment. In this study, hemoglobin levels significantly increased after 6 months of VitabranE treatment, whereas these remained unchanged in the control group. Moreover, at the same ESA dose, the ERI was significantly lower during the VitabranE treatment period.

Further support for the findings of these randomized trials came from a pilot cross-over study by Mandolfo et al. (in press), which was conducted on patients using central venous catheters for blood access. Sixteen patients were enrolled and divided into 2 treatment groups (VitabranE dialyzer versus synthetic membrane dialyzers) and were followed for 2 periods of 6 months each. The results showed that the ERI decreased significantly in the group that received treatment with VitabranE, whereas it did not change in the control group. Hemoglobin levels were not affected; thus, the authors concluded that VitabranE membranes might help reducing the ESA dose required in anti-anemic therapy.

#### **3.3 Improvement of inflammatory markers**

In the report by Panichi et al., 2011, the authors observed that beside of ERI reduction, CRP and IL-6 levels decreased during VitabranE treatment, whereas no significant changes were found during the control polysulfone treatment. The study by Mandolfo et al. (in press) on catheterized patients with a high inflammatory burden also reported a better control of CRP levels during the VitabranE treatment. In these studies, a lower inflammatory response was associated with improved ERI, which is consistent with the role of chronic inflammation and oxidative stress as pathogenic factors of uremic anemia (Del Vecchio et al., 2011).

Calò et al., 2011, conducted a 1-year study on 25 HD patients to evaluate the effects of VitabranE on the biochemical markers of inflammation. The authors employed a molecular approach by using immunoblot (western blot) analysis to assess the expression of p22phox, plasminogen activator inhibitor (PAI)-1, phosphorylated extracellular signal-regulated kinase (pERK)1/2 and heme oxygenase (HO)-1 in circulating mononuclear leukocytes at the beginning of the study and after 6 and 12 months of treatment with VitabranE. The treatment with VitabranE significantly decreased the expression of inflammatory markers of p22phox*,* PAI-1, and pERK1/2, while the treatment increased the expression of antiinflammatory marker of HO-1.

#### **3.4 Reduction in the levels of oxidative stress makers**

Preliminary investigations of blood levels of advanced protein oxidation products (AOPP) and fluorescent AGEs were performed in the randomized controlled pilot trial reported by

compared VitabranE with polysulfone membranes. A pilot study by Andrulli et al., 2010, carried out with a 2-arm randomized controlled design showed that 8-month treatment with VitabranE decreased the erythropoiesis-stimulating agent (ESA)–resistance index (ERI); ERI is calculated as the ratio between ESA dosage (IU/kg/w) and hemoglobin levels (g/dL). In the primary analysis, ERI showed no significant deference between the groups treated with VitabranE and the control polysulfone membrane. However, in the secondary analysis where the baseline parathyroid hormone (PTH) and serum vitamin E levels were included as covariates, the ERI was significantly decreased in the group treated with VitabranE than in the group treated with the control polysulfone membrane. Therefore, the authors concluded that VitabranE membranes have potentially beneficial effects on ERI of HD patients. This conclusion was confirmed in another and more recent multicenter study by Panichi et al., 2011. In this report, a crossover design was employed and 62 HD patients from 13 dialysis units were randomized to receive treatments with VitabranE or polysulfone dialyzer controls. The patients were studied for 2 steps of 6 months in each treatment. In this study, hemoglobin levels significantly increased after 6 months of VitabranE treatment, whereas these remained unchanged in the control group. Moreover, at the same ESA dose,

Further support for the findings of these randomized trials came from a pilot cross-over study by Mandolfo et al. (in press), which was conducted on patients using central venous catheters for blood access. Sixteen patients were enrolled and divided into 2 treatment groups (VitabranE dialyzer versus synthetic membrane dialyzers) and were followed for 2 periods of 6 months each. The results showed that the ERI decreased significantly in the group that received treatment with VitabranE, whereas it did not change in the control group. Hemoglobin levels were not affected; thus, the authors concluded that VitabranE

In the report by Panichi et al., 2011, the authors observed that beside of ERI reduction, CRP and IL-6 levels decreased during VitabranE treatment, whereas no significant changes were found during the control polysulfone treatment. The study by Mandolfo et al. (in press) on catheterized patients with a high inflammatory burden also reported a better control of CRP levels during the VitabranE treatment. In these studies, a lower inflammatory response was associated with improved ERI, which is consistent with the role of chronic inflammation and

Calò et al., 2011, conducted a 1-year study on 25 HD patients to evaluate the effects of VitabranE on the biochemical markers of inflammation. The authors employed a molecular approach by using immunoblot (western blot) analysis to assess the expression of p22phox, plasminogen activator inhibitor (PAI)-1, phosphorylated extracellular signal-regulated kinase (pERK)1/2 and heme oxygenase (HO)-1 in circulating mononuclear leukocytes at the beginning of the study and after 6 and 12 months of treatment with VitabranE. The treatment with VitabranE significantly decreased the expression of inflammatory markers of p22phox*,* PAI-1, and pERK1/2, while the treatment increased the expression of anti-

Preliminary investigations of blood levels of advanced protein oxidation products (AOPP) and fluorescent AGEs were performed in the randomized controlled pilot trial reported by

the ERI was significantly lower during the VitabranE treatment period.

membranes might help reducing the ESA dose required in anti-anemic therapy.

oxidative stress as pathogenic factors of uremic anemia (Del Vecchio et al., 2011).

**3.3 Improvement of inflammatory markers** 

inflammatory marker of HO-1.

**3.4 Reduction in the levels of oxidative stress makers** 

Andrulli et al., 2010. In this study, these protein-damaged markers were investigated as oxidative and carbonyl stress indices associated with the correction of ERI. Although IL-6 and CRP levels were not affected, the 2 indices showed better control in the patients receiving with VitabranE than in those receiving treatment with polysulfone dialyzer (Galli et al., manuscript in preparation).

Vitamin E-bonded dialyzer membranes were originally developed with the aim of reducing oxidative stress. As shown in the section 2.2, lowered lipid peroxidation was observed in clinical trials with Excebrane, a cellulose-based vitamin E-bonded membrane. In the case of VitabranE, 2 studies were conducted, considering LDL oxidation as an end point. Morimoto et al., 2005, reported that the 15 patients who received 6 months of treatment with VitabranE showed significant reduction in the levels of asymmetric dimethylarginine (ADMA), malondialdehyde low density lipoprotein (MDA-LDL), and oxidized low density lipoprotein (Ox-LDL). The levels returned to baseline when the membrane was changed to a polysulfone dialyzer membrane. In a matched control group, patients treated with polysulfone dialyzers showed no change in ADMA, Ox-LDL, and MDA-LDL levels during the entire treatment period of 18 months. The other report from Calò et al., 2011, showed that VitabranE improved the levels of inflammation markers and also reduced plasma levels of Ox-LDL, which was evaluated by enzyme-linked immunosorbent assay.
