Clinical review: Blood purification for sepsis

Sepsis is the primary cause of death in the intensive care unit. Extracorporeal blood purification therapies have been proposed for patients with sepsis in order to improve outcomes since these therapies can alter the host inflammatory response by non-selective removal of inflammatory mediators or bacterial products or both. Recent technological progress has increased the number of techniques available for blood purification and their performance. In this overview, we report on the latest advances in blood purification for sepsis and how they relate to current concepts of disease, and we review the current evidence for high-volume hemofiltration, cascade hemofiltration, hemoadsorption, coupled plasma filtration adsorption, high-adsorption hemofiltration, and high-cutoff hemofiltration/hemodialysis. Promising results have been reported with all of these blood purification therapies, showing that they are well tolerated, effective in clearing inflammatory mediators or bacterial toxins (or both) from the plasma, and efficacious for improvement of various physiologic outcomes (for example, hemodynamics and oxygenation). However, numerous questions, including the timing, duration, and frequency of these therapies in the clinical setting, remain unanswered. Large multicenter trials evaluating the ability of these therapies to improve clinical outcomes (that is, mortality or organ failure), rather than surrogate markers such as plasma mediator clearance or transient improvement in physiologic variables, are required to define the precise role of blood purification in the management of sepsis.


Introduction
Sepsis is the primary cause of death in the intensive care unit [1], and more than 35% of patients are admitted with sepsis or develop it during their intensive care unit stay. Hospital mortality rates are 27%, reaching 54% in the case of septic shock [2].
Extracorporeal blood purifi cation therapies have been proposed to improve outcomes for patients with sepsis. Th ese therapies are based on the principle that removal of infl ammatory mediators or bacterial toxins (or both) from the blood will favorably modulate the host infl amma tory response. Recently, signifi cant technological progress has greatly broadened the spectrum of techniques available for blood purifi cation. Indeed, promising results have been reported with high-volume hemofi ltration (HVHF), cascade hemofi ltration, hemoadsorption, plasmapheresis, coupled plasma fi ltration adsorption (CPFA), high-adsorption hemofi ltration, and high-cutoff (HCO) hemodialysis/hemofi ltration. However, these techniques have not entered into mainstream clinical practice around the world.
Th is overview has three aims. First, we will report on the latest advances in blood purifi cation for sepsis. Th en, we will briefl y describe each therapy and explain how they work and discuss how they relate to current concepts of disease. Finally, we will review the current evidence from the medical literature, highlighting the most important studies related to each therapy. To select articles from medical literature, we conducted a systematic review of the MEDLINE database using PubMed with the following search terms: blood purifi cation, highvolume hemofi ltration, sepsis, hemoadsorption, highcutoff membranes, and coupled plasma fi ltration adsorption. Th e search included experimental and clinical studies.

Concept of blood purifi cation
Systemic infl ammatory states such as severe sepsis and septic shock result in immunologic disturbances with the release of numerous infl ammatory mediators. Th e systemic infl ammatory response, though a result of innate immunity, can become deleterious when excessive or uncontrolled, leading to the development of multi-organ failure syndrome and death. At least two mecha nisms are identifi ed to explain the potential harmful eff ects of this host infl ammatory response: cyto kines have the capacity to damage the cells (cytotoxic eff ects) [3], and the prolonged release of infl ammatory mediators leads to severely impaired immunity [4]. Th is 'immunoparalysis'

Abstract
Sepsis is the primary cause of death in the intensive care unit. Extracorporeal blood purifi cation therapies have been proposed for patients with sepsis in order to improve outcomes since these therapies can alter the host infl ammatory response by non-selective removal of infl ammatory mediators or bacterial products or both. Recent technological progress has increased the number of techniques available for blood purifi cation and their performance. In this overview, we report on the latest advances in blood purifi cation for sepsis and how they relate to current concepts of disease, and we review the current evidence for high-volume hemofi ltration, cascade hemofi ltration, hemoadsorption, coupled plasma fi ltration adsorption, high-adsorption hemofi ltration, and high-cutoff hemofi ltration/hemodialysis. Promising results have been reported with all of these blood purifi cation therapies, showing that they are well tolerated, eff ective in clearing infl ammatory mediators or bacterial toxins (or both) from the plasma, and effi cacious for improvement of various physiologic outcomes (for example, hemodynamics and oxygenation). However, numerous questions, including the timing, duration, and frequency of these therapies in the clinical setting, remain unanswered. Large multicenter trials evaluating the ability of these therapies to improve clinical outcomes (that is, mortality or organ failure), rather than surrogate markers such as plasma mediator clearance or transient improvement in physiologic variables, are required to defi ne the precise role of blood purifi cation in the management of sepsis.
state plays a major role in mortality because it favors severe secondary nosocomial infections. Secondary infections can be bacterial but also may be related to reactivation of dormant viruses [5,6].
Th e overall concept of blood purifi cation is therefore to attenuate this overwhelming systemic expression of proand anti-infl ammatory mediators. Restoration of immune homeostasis is thought to be able to improve outcomes and survival. Multiple mediators are involved in this infl ammatory response [7], but past attempts to modulate it by targeting single components have failed, at least at the clinical phase [8]. Th us, over time, the blood puri fication concept and therapies have evolved toward the non-specifi c removal of a broad spectrum of infl ammatory mediators, which can also include microbial toxins.
Recently, a number of theories to explain the eff ects of blood purifi cation have been proposed. First, Ronco and colleagues [9] hypothesized that eliminating the peaks of cytokine blood concentrations during the early phase of sepsis could stop the infl ammatory cascade, limit organ damage, and consequently decrease the incidence of multi-organ failure syndrome. Second, Honoré and Matson [10] proposed the 'threshold immunomodulation hypothesis' , postulating that the cytokine removal from the blood compartment leads to the removal of cytokines located at the tissue level because of an equilibration of their concentrations between these two compartments. Th is theory explains why numerous studies assessing blood purifi cation techniques found an improvement of outcomes with no modifi cation of cytokine blood concen trations as cytokines from the tissues replace those removed from the blood. Th ird, Di Carlo and Alexander [11] proposed the 'mediator delivery hypothesis' , in which HVHF is responsible for an increase of the lymphatic fl ow because of the high amounts of crystalloid fl uids used for replacement with this technique. Th is leads to a signifi cant drag and displacement of infl ammatory media tors to the blood compartment, making them available for removal [11].
Finally, Peng and colleagues [12] recently suggested that blood purifi cation therapies act at the infl ammatory cell level to restore the immune function through the regulation of monocytes, neutrophils, or even lymphocytes. Th is theory is supported by recent studies [13,14]. Indeed, it has been reported that polymyxin B hemoadsorption could increase the expression of leukocyte surface markers such as HLA-DR [13]. Th us, hemoadsorption would act as a 'reprogrammation system' for the leukocytes. However, the mechanism by which hemoadsorption stimulates HLA-DR expression remains unknown. If this 'cellular level' theory with immune response restoration is confi rmed, timing indications for blood purifi cation would need to be reconsidered since optimal timing for initiating a blood purifi cation therapy would not be only in the early phase of septic shock as it is suggested today. Furthermore, a novel component of this hypothesis is that, by removing mediators from the plasma in the setting of systemic infl ammation, one can restore the concentration gradient from plasma to infected tissues [12]. Th is gradient has signifi cant eff ects on leukocyte traffi cking and bacterial clearance [14]. Th us, the 'cytokinetic model' may be more relevant than cytotoxic models to explain the association between high cytokine levels and mortality (Figure 1).

High-volume hemofi ltration
By increasing plasma water exchanges, HVHF appears to be an attractive therapy to remove a signifi cant amount of infl ammatory mediators from the plasma. First, these circulating molecules are predominately water-soluble and convection carries both plasma water and solutes across a semi-permeable membrane along a hydrostatic pressure gradient. Second, most infl ammatory mediators are so-called middle-molecular-weight molecules with a wide range of mass (from 5 to 60 kDa) and convection is far more eff ective than diff usion in removing middle molecules [15,16]. Th ird, depending on their composition, most hemofi ltration membranes also have some adsorptive properties. Th e ultrafi ltrate contains the molecules from the plasma which are able to cross the membrane (molecular weight below the membrane cutoff ), and adsorption allows the removal of some other molecules with a molecular weight higher than the membrane cutoff .
HVHF is not well defi ned in the medical literature. Recently, Honoré and colleagues [17] convened a con sensus conference to clarify the defi nition of HVHF. Th ey agreed that HVHF includes continuous high-volume treatment of 50 to 70 mL/kg per hour 24 hours a day and intermittent HVHF with brief, very-high-volume treatment at 100 to 120 mL/kg per hour for a short period of 4 to 8 hours, followed by conventional continu ous venovenous hemofi ltration (CVVH). Th is latter strategy is also called 'pulse HVHF' [18]. However, for experts from the Acute Dialysis Quality Initiative work group, greater than 35 mL/kg per hour is already con sidered HVHF [19]. Indeed, given that 'renal dose' hemo fi ltration for acute kidney injury has been standardized at 25 to 30 mL/kg per hour (see reference [20] for justifi cation), defi ning HVHF at greater than 35 mL/kg per hour seems reasonable.
Many animal studies have been performed to assess HVHF, especially in the 1990s, when HVHF was still very experimental in humans. Grootendorst and colleagues [21] reported an improvement in cardiac performance in pigs with endotoxin-induced shock when HVHF was applied. Th e authors hypothesized that some vasoactive mediators, responsible for the myocardial depression, were removed with HVHF. Even though other authors recently suggested a positive eff ect on the myocardial mitochondrial dysfunction [22], the pathophysiologic explanation of the hemodynamic improvement with HVHF remains unclear [23]. In septic dogs, Bellomo and colleagues [24] also found that HVHF improved hemodynamic parameters compared with a sham circuit with no hemofi lter. Furthermore, some animal studies assessed HVHF by looking at ultrafi ltrate obtained from either healthy donor or septic donor animals and infused into a healthy acceptor animal. Th e ability of HVHF to remove toxic mediators is suggested when ultrafi ltrate obtained from septic animals leads to hemodynamic distur bances or even death in healthy animals. In a prospective randomized controlled study including 65 septic pigs, Lee and colleagues [25] reported an increase survival time in fi ltered animals compared with matched non-fi ltered ones. Increments in survival time even increased directly with fi ltration fraction. Moreover, ultrafi ltrate concentrate obtained from septic pigs produced death in healthy ones whereas the infusion of 'clean' ultrafi ltrate concentrate produced no response.
Numerous human studies have shown benefi cial hemodynamic eff ects of HVHF. In a randomized crossover study of 11 patients with septic shock and multiorgan failure, an 8-hour period of HVHF (6 L/hour) was associated with a greater reduction in norepinephrine requirements in comparison with a similar period of CVVH (1 L/hour) [26]. Reduction of vasopressor requirements with HVHF was also found more recently in a pilot randomized study comparing CVVH at 65 mL/kg per hour versus 35 mL/kg per hour in 20 septic shock patients with acute kidney injury [27]. Large randomized controlled studies of HVHF in septic shock which use mortality as the primary outcome are lacking. One such study, known as the IVOIRE (High Volume in Intensive Care) study, which compares 70 mL/kg per hour versus 35 mL/kg per hour, is currently ongoing in Europe. Although results from this study have not yet been released, the investigators have reported that the enrollment process was very slow and therefore the number of patients included is likely to be less than 150, making conclusions regarding mortality diffi cult to establish. Th us, the only available studies regarding mortality have relied on comparisons with expected mortality based on the patients' severity scores at admission. Th ough uncontrolled, at least six studies have found signifi cant (and sometimes spectacular) reductions in mortality rate with HVHF compared with predicted mortality [28][29][30][31][32][33]. Honoré and colleagues [29] reported a reduction of the mortality rate from 79% (expected mortality based on APACHE II [Acute Physiology and Chronic Health Evalua tion II] score and SAPS II [Simplifi ed Acute Physiology Score II]) to 55%. Several years later, Joannes-Boyau and colleagues [30] obtained a similar result with a predicted 28-day mortality of 70% and an observed mortality of 46% in a study assessing the eff ect of 40 to 60 mL/kg per hour maintained for 96 hours in patients with septic shock. In patients without sepsis but with systemic infl ammation, the eff ect of HVHF on mortality was evaluated in two randomized controlled trials [34,35]. In 61 resuscitated cardiac arrest patients, veryhigh-volume hemofi ltration (200 mL/kg per hour during 8 hours) was associated with improved 6-month survival and a decreased risk of death from early intractable shock [35]. Th e most important recent studies assessing mortality with HVHF as a blood purifi cation therapy are summarized in Table 1. Unlike HVHF, standard 'renal dose' continuous renal replacement therapy (CRRT) appears to be ineff ective as an immune modulating therapy. Like Cole and colleagues [36] in 2002, Payen and colleagues [37] found no diff erence (and even a trend toward worse outcomes) between septic shock patients who did not have acute kidney injury and who underwent CVVH (25 mL/kg per hour for a 96-hour period) at the early phase of sepsis and those who were managed conventionally.
HVHF has important limitations such as a theoretical depletion of low-molecular-weight molecules (nutrients, vitamins, trace elements, and drugs such as antibiotics), an elevated cost due mainly to the requirement of large replacement fl uid amounts, and a high nursing workload [38,39]. Cascade hemofi ltration was recently developed to limit some of these drawbacks [40]. It allows application of HVHF select ively on middle-molecular-weight molecules with a low replacement fl uid fl ow rate because of a particular circuit that combines two hemofi ltration membranes having diff erent cutoff s (Figure 2).

Hemoadsorption
Hemoadsorption places sorbents in direct contact with blood via an extracorporeal circuit. Th e sorbent attracts solutes through hydrophobic interactions, ionic attrac tion, hydrogen bonding, and van der Waals interactions [41]. Until recently, poor biocompatibility has been the main clinical limitation of hemoadsorption, as evidenced by severe thrombocytopenia and leukopenia [41]. Th e interesting feature of hemoadsorption is its high-molecular-weight adsorption potential, allowing it to target large molecules, exceeding the cutoff of conventional synthetic high-fl ux hemofi lters.
Polymyxin B is a cyclic basic polypeptide that disrupts the permeability of the cell membrane of Gram-negative bacteria. It was developed as an antibiotic but its severe renal toxicity precludes systemic use. However, polymyxin B-immobilized polystyrene-derived fi bers have been developed for use in extracoporeal therapy as a means to remove endotoxin from the blood. Th ough still under evaluation in Europe and the US, polymyxin B hemoadsorption (Toraymyxin; Toray Industries, Inc., Tokyo, Japan) is widely used in Japan as a blood purification therapy and is covered by the Japanese national health insurance [42]. Th e EUPHAS (Early Use of Polymyxin B Hemoperfusion in Abdominal Sepsis) study was a prospective, multicenter randomized controlled study that was performed in 10 Italian intensive care units [43]. Sixty-four patients with severe sepsis or septic shock were randomly assigned to one of two groups (either conventional therapy or conventional therapy along with two sessions of polymyxin B hemoadsorption) within the 6 hours following emergency surgery for intraabdominal infection. Hemodynamics, the PaO 2 /FiO 2 (arterial partial pressure of oxygen/fraction of inspired oxygen) ratio, and the SOFA (Sequential Organ Failure Assessment) score of patients from the hemoadsorption group improved within 72 hours, whereas the conventional group did not. Th e main result (though not the primary outcome) of this study was the 28-day mortality rate, which was drastically reduced to 32% in the hemoadsorption group compared with 53% in the control group (P = 0.03). However, the conclusions of this study should be taken with caution. Indeed, although mortality was only a secondary endpoint, the study was prematurely stopped because it was judged to be unethical to deprive patients of hemoadsorption. Th e decision to halt the study seems extremely debatable because it was based upon a secondary analysis of an underpowered study and a diff erent outcome in a single patient would have abolished the statistical diff erence in mortality [44]. Moreover, the fact that the study was controlled is also debatable since hemodynamic and respiratory parameters were only analyzed independently within each group, comparing 72-hour to baseline levels. No statistical comparison was performed between the two groups at 72 hours. No statistical comparison was performed between the two groups at 72 hours.
Other trials showed interesting results with polymyxin B hemoadsorption. Vincent and colleagues [45] conducted a multicenter randomized controlled study that enrolled 36 postsurgical patients with septic shock. Nineteen patients were allocated to standard treatment, and 17 were given an additional polymyxin B hemoadsorption session. Endotoxin and interleukin-6 concentrations were not diff erent between the two groups within the 24 hours following the start of treatment. However, patients treated with hemoadsorption had a marked improvement in hemodynamics and oxygen transport function, and the need for CRRT after the study was less important in the hemoadsorption group. Th ese benefi cial eff ects were also reported in a systematic review of 28 publications (1,425 patients) [46]. Indeed, although Cruz and colleagues [46] highlighted the suboptimal quality of the studies, favorable eff ects regarding blood pressure, vasopressor require ment, gas exchanges, and even mortality were  reported. Importantly, this review points out the need for further rigorous studies of this therapy. Two large multicenter studies, similar to the EUPHAS study, were expected to be started in the US and Europe in 2010. Th e CytoSorb™ technology (CytoSorbents Corporation, Monmouth Junction, NJ, USA) is composed of cartridges containing biocompatible polystyrene divinyl benzene copolymer beads. Th is technology does not target endotoxin but has been shown to result in rapid in vitro and in vivo elimination of several key cytokines [47]. Recently, 33 septic rats were randomly assigned to receive either hemoadsorption or sham treatment for 3 hours [48]. Cytokine concentrations were lower in the hemoadsorption group at the end of the treatment and this diff erence lasted 6 hours after treatment. Blood pressure of the rats from the hemoadsorption group was higher than that of the sham group. Finally, the overall survival rate (defi ned at 12 hours after randomization) was also signifi cantly greater in the hemoadsorption group (11/17 versus 2/16; P <0.01).
Th e resin referred to by its manufacturer as "CTR resin" (Kaneka Corporation, Osaka, Japan) is an adsorbent composed of porous cellu lose beads. Taniguchi and colleagues [49] reported that CTR eff ectively adsorbed small-to middle-sized proteins such as cytokines, enterotoxins, and toxic shock syn drome toxin-1 in vitro. Addition ally, in an endotoxemic rat model, hemoadsorption with CTR dramatically reduced the mortality rate 8 hours after endotoxin injection (14% versus 92% for endo toxemia alone) [49]. Interestingly, the same authors further demon strated in rats the dose-related eff ects of hemoadsorption with CTR on mortality [50].

Plasmapheresis and coupled plasma fi ltration adsorption
Only very limited data are available in the medical literature regarding plasmapheresis, plasma exchanges, and related techniques for this indication [51][52][53][54][55]. Nevertheless, it has been suggested that these therapies might be benefi cial, especially for patients with Gram-negative sepsis [52,54,56,57] and when implemented as early as possible [58]. Additional studies are therefore warranted to better assess these therapies for blood purifi cation [59].
CPFA fi rst separates plasma from the blood by means of a plasma fi lter. Th e plasma then circulates through a sorbent, allowing infl ammatory mediator adsorption, and fi nally returns to the blood, where a second blood fi lter is used for renal support (hemofi ltration, hemodialysis, or hemodiafi ltration) (Figure 3). Performing adsorption with plasma, rather than with blood, avoids coagulation issues, platelet aggregation, and hemolysis and allows the use of a low fl ow rate, extending the time of contact between the infl ammatory mediators and the sorbent and consequently maximizing their adsorption.
Several studies have demonstrated the safety and the eff ectiveness of CPFA for removing infl ammatory mediators from the circulation [60,61]. Moreover, CPFA was able to increase the survival of a rabbit model of endotoxic shock and to improve hemodynamics and the pulmonary function of patients with septic shock [62,63]. Recently, CPFA was compared with other extracorporeal blood purifi cation techniques. In a small pilot study, Lentini and colleagues [64] reported no diff erence in hemodynamic eff ects between pulse HVHF and CPFA in patients with septic shock. In pigs with hyperdynamic septic shock, continuous hemofi ltration, unlike CPFA, was able to remove some infl ammatory mediators involved in delayed cardiac repolarization [65]. Conversely, Ronco and colleagues [61] reported in patients with septic shock that CPFA combined with hemodialysis was associated with greater improved hemodynamics compared with continuous hemodiafi ltration. Th e authors hypothesized that this result could be due to the ability of CPFA to restore leukocyte responsiveness to lipo polysaccharide. Interestingly, eff ects of CPFA on immune function were also shown by Mao and colleagues [66] in a small crossover study comparing CPFA with HVHF in septic patients with multiple organ dysfunction syndrome. HLA-DR expression increased after CPFA but there was no change after HVHF. In addition, spontaneous and lipopolysaccharide-induced tumor necrosis factor production increased over time with CPFA but did not change with HVHF. Th e authors therefore suggested that CPFA was superior to HVHF in restoring leukocyte responsiveness.

High-adsorption hemofi ltration and high-cutoff membranes
Other approaches proposed for blood purifi cation therapies consist of optimizing the performances of the hemofi lters regarding cytokine or endotoxin removal (or both) by manipulating their composition or structure. High-adsorption hemofi ltration is a technique whereby the adsorption properties of a hemofi lter are enhanced. Positive hemodynamic eff ects of a polyacrylonitrile hemofi ltration membrane having endotoxin adsorption properties were recently reported in septic pigs [67]. Th e membrane surface polarity was modifi ed by adjunction of a polyethylenimine coating, a positively charged polymer, allowing it to catch negatively charged endotoxins via surface adsorption. Th is study highlights another potentially important aspect of blood purifi cation for the future: the synergy between diff erent blood purifi cation mechanisms (HVHF + high adsorption) [67,68]. In the same line, other models in which HVHF and highpermeability hemofi ltration work synergistically have shown promising results [69].
Th e use of HCO membranes represents another logical strategy to increase mediator removal. When the membrane pore size is increased from 0.01 to 0.02 μm (Figure 4), the spectrum of molecules aff ected by the therapy is signifi cantly broadened [70]. In experimental models of sepsis, HCO membranes improve hemodynamics and prolong survival [71]. In patients with sepsis-induced acute kidney injury, Morgera and colleagues [72] reported a reduction in vasopressor require ments with the use of HCO hemofi ltration and not with conventional CVVH. Additionally, cytokine clear ance rates were signifi cantly higher in the HCO hemo fi ltration group. In another randomized study, HCO hemofi ltration restored the monocyte proliferation capacity of septic patients, probably by eliminating immunomodulatory mediators [73]. However, the use of HCO hemofi ltration has been challenged by the albumin loss, which can be up to 15 g per 4-hour session [74]. Consequently, HCO membranes are now proposed for use with hemodialysis. Indeed, the use of diff usion rather than convection is suggested to reduce the albumin loss without signifi cantly impacting cytokine clearances, especially in cases of elevated dialysate fl ow rates [74]. Haase and colleagues [75] showed that HCO hemodialysis was more effi cient than standard hemo dialysis in regard to diff usive cytokine clearances. While some decreases in plasma cytokine levels were even reported after only 4 hours of treatment, the albumin loss was limited and plasma albumin concentrations remained stable. Conversely, Lee and colleagues [76] recently highlighted reductions in serum albumin levels after HCO hemodialysis sessions, leaving this question open to further clinical investigation. To address this issue, membrane parameters and aspects other than the type of modality (diff usion versus convection) -for example, membrane homogeneity in terms of pore size, membrane surface, the use of super-high-fl ux hemofi lters that have a slightly lower cutoff , and the use of the association HVHF-high permeability -certainly need to be taken into account [69]. Finally, it should be mentioned that the medical literature regarding HCO membranes contains signifi cant heterogeneity due to diff erences in terms of type of HCO membrane (cutoff points, surface area, and composition), modality used, and type of cytokines measured, making conclusions regarding this strategy diffi cult to establish.

Conclusions
Considerable work remains in order to fi nd and optimize the best blood purifi cation strategy for treatment of sepsis. A better understanding of how these therapies work by modulating the cytotoxic and cytokinetic eff ects of infl ammatory mediators is essential. Convection, diff usion, and adsorption should probably not be seen as competitive mechanisms for blood purifi cation but rather as complementary ones. Many experimental and clinical studies have reported promising results showing that blood purifi cation therapies are well tolerated, eff ective in clearing infl ammatory mediators or endotoxins (or both) from the plasma, and responsible for an improvement of diff erent physiologic parameters (hemodynamics and oxygenation). However, important questions, including timing, duration, and frequency of these therapies in the clinical setting, remain unanswered. Large multicenter trials evaluating the ability of these therapies to improve clinical outcomes (that is, mortality or organ failure), rather than focusing on surrogate markers such as plasma mediator clearance or transient improvement in physiologic variables, are required to defi ne the precise role of blood purifi cation in the management of sepsis.

Competing interests
TR has received research funding from Gambro (Stockholm, Sweden) and Fresenius Medical Care (Bad Homburg, Germany) as well as consulting fees from Gambro. JK has received research funding from Gambro, CytoSorbents Corporation (Monmouth Junction, NJ, USA), and Kaneka Corporation (Osaka, Japan) as well as consulting fees from Gambro, Baxter (Deerfi eld, IL, USA), and CytoSorbents Corporation.