Prophylactic Oral Application of Activated Charcoal Mitigates Acute Campylobacteriosis in Human Gut Microbiota-Associated IL-10-/- Mice

The incidence of human Campylobacter jejuni infections is increasing worldwide. It is highly desirable to prevent campylobacteriosis in individuals at risk for severe disease with antibiotics-independent non-toxic compounds. Activated charcoal (AC) has long been used as an anti-diarrheal remedy. Here, we tested the disease-mitigating effects of oral AC versus placebo in human gut microbiota-associated (hma) IL-10-/- mice starting a week prior to C. jejuni infection. On day 6 post-infection, the gastrointestinal C. jejuni loads were comparable in both infected cohorts, whereas campylobacteriosis symptoms such as wasting and bloody diarrhea were mitigated upon AC prophylaxis. Furthermore, AC application resulted in less pronounced C. jejuni-induced colonic epithelial cell apoptosis and in dampened innate and adaptive immune cell responses in the colon that were accompanied by basal concentrations of pro-inflammatory mediators including IL-6, TNF-α, IFN-γ, and nitric oxide measured in colonic explants from AC treated mice on day 6 post-infection. Furthermore, C. jejuni infection resulted in distinct fecal microbiota shift towards higher enterobacterial numbers and lower loads of obligate anaerobic species in hma mice that were AC-independent. In conclusion, our pre-clinical placebo-controlled intervention study provides evidence that prophylactic oral AC application mitigates acute murine campylobacteriosis.

Efficacy of extracorporeal membrane oxygenation in pediatric COVID-19 and MIS-C cases: A single-center experience

Background

This study aimed to evaluate the need and the indication of extracorporeal membrane oxygenation (ECMO) in patients diagnosed with coronavirus disease 2019 (COVID-19) and multisystem inflammatory syndrome in children (MIS-C) followed up in the pediatric intensive care unit by the demographic, clinical, and laboratory data and treatment response.

Methods

A total of 79 patients (43 males, 36 females; median age: 138 months; range, 6 to 210 months) with COVID-19 and MIS-C followed up between September 2020 - September 2021 were included in this retrospective study. Demographic and clinical data were retrospectively collected from patient files, and clinical data, laboratory findings, chest X-rays, and echocardiography results of six patients (1 male and 5 female, median age: 159 months, range, 13 to 210 months) who needed ECMO due to poor response to medical treatment were recorded before and after the ECMO therapy.

Results

Extracorporeal membrane oxygenation therapy was performed on one patient with a positive COVID-19 polymerase chain reaction test and five patients with MIS-C in our unit. Five patients were supported with venoarterial (v-a) ECMO, and one patient was supported with venovenous ECMO. Median hospitalization time was 29 (range, 24 to 50) days, median Pediatric Risk of Mortality score was 19.5 (range, 11 to 36), and median length of mechanical ventilation was 23.5 (range, 10 to 45) days. The median vasoactive inotropic score was 55.5 (range, 18 to 110) before ECMO, while the median vasoactive inotropic score was 11 (range, 0 to 34) after ECMO. Four patients were successfully weaned off ECMO, and one of these patients was lost due to brain death 15 days after the weaning. One patient infected with the delta variant of COVID-19, which remained positive during the clinical course, and one patient diagnosed with MIS-C was lost despite the v-a ECMO support. Three of the patients were discharged. Thrombosis developed in the superficial femoral artery of one patient on the cannulated side during v-a ECMO. No death due to complications of ECMO was recorded.

Conclusion

In our study, although the majority of our patients followed up with the diagnosis of COVID-19 and MIS-C showed a mild or moderate clinical course, it was observed that a severe clinical course could develop in a small number of patients and that ECMO treatment may be needed in these patients. In agreement with the ECMO studies with different indications in the literature, we conclude that ECMO therapy may markedly contribute to the prognosis in COVID-19 and MIS-C patients when the initiation and termination timing of therapy is correct.

Disease-Alleviating Effects of Peroral Activated Charcoal Treatment in Acute Murine Campylobacteriosis

Foodborne Campylobacter jejuni infections are on the rise and responsible for worldwide serious health issues. Increasing resistance of C. jejuni strains against antimicrobial treatments, necessitates antibiotics-independent treatment options for acute campylobacteriosis. Activated charcoal (AC) constitutes a long-known and safe compound for the treatment of bacterial enteritis. In this preclinical intervention study, we addressed potential anti-pathogenic and immune-modulatory effects of AC during acute experimental campylobacteriosis. Therefore, microbiota-depleted IL-10^-/- mice were infected with C. jejuni by gavage and challenged with either AC or placebo via the drinking water starting on day 2 post-infection. On day 6 post-infection, AC as compared to placebo-treated mice did not only harbor lower intestinal pathogen loads but also presented with alleviated C. jejuni-induced clinical signs such as diarrhea and wasting symptoms. The improved clinical outcome of AC-treated mice was accompanied by less colonic epithelial cell apoptosis and reduced pro-inflammatory immune responses in the intestinal tract. Notably, AC treatment did not only alleviate intestinal, but also extra-intestinal and systemic immune responses as indicated by dampened pro-inflammatory mediator secretion. Given the anti-pathogenic and immune-modulatory properties of AC in this study, a short-term application of this non-toxic drug constitutes a promising antibiotics-independent option for the treatment of human campylobacteriosis.

Development of boronic acid-functionalized mesoporous silica-coated core/shell magnetic microspheres with large pores for endotoxin removal

Endotoxins are found almost everywhere and possess high toxicity in vivo and in vitro. Here we design a novel boronate affinity material, called boronic acid-functionalized mesoporous silica-coated core/shell magnetic microspheres (Fe₃O₄@nSiO₂@mSiO₂-BA) with large pores (pore size > 20 nm) based on the chemical structure and physical properties of endotoxins, for facile and highly efficient removal of endotoxins. Dual modes for endotoxin removal were proposed and confirmed in this work: the endotoxin aggregates with size < 20 nm were bound with boronic acid ligands chemically modified on the inner and outer surface of the large pores of Fe₃O₄@nSiO₂@mSiO₂-BA microspheres; while the larger endotoxin micelles (size >20 nm) were absorbed on the outer surface of the prepared material based on boronate affinity. Transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms and Fourier transform infrared (FT-IR) spectroscopy confirm that Fe₃O₄@nSiO₂@mSiO₂-BA microspheres possess core/shell structure, uniform diameter (520 nm), high surface area (205.57 m²/g), large mesopores (21.8 nm) and boronic acid ligands. The purification procedures of Fe₃O₄@nSiO₂@mSiO₂-BA microspheres for endotoxin were optimized, and 50 mM NH₄HCO₃ (pH 8.0) and 0.05 M fructose were selected as loading/washing, elution buffers, respectively. The binding capacity of Fe₃O₄@nSiO₂@mSiO₂-BA microspheres for endotoxin was calculated to be 60.84 EU/g under the optimized conditions. Finally, the established analytical method was applied to remove endotoxins from plasmid DNA. After endotoxin removal, the endotoxin content in plasmid DNA was reduced from 0.0026 to 0.0006 EU/mL for two-fold concentration, and from 0.0088 to 0.0022 EU/mL for five-fold concentration after binding, respectively. Additional advantages of the prepared boronate affinity material include excellent stability, reusability/repeatability, and low cost. Boronate affinity materials with large pores could thus prove to be powerful adsorbents for endotoxin removal and the potential applications in the aspects of biological research, pharmaceutical industry, and life health.

Cytokine Removal during Continuous Renal Replacement Therapy: An Ex Vivo Comparison of Convection and Diffusion

Background and objectives

It is unknown whether cytokine adsorption to the membrane during continuous renal replacement therapy is affected by the technique. Such knowledge might affect the choice of technique in vivo. Accordingly, we conducted an ex vivo study to test whether continuous veno-venous hemofiltration (CVVH) or continuous veno-venous hemodialysis (CVVHD) affect cytokine adsorption differently.

Setting

Laboratory attached to the Intensive Care Unit of a tertiary hospital

Design

Six healthy human volunteers donated blood, which was incubated with endotoxin. Control blood was left at room temperature, and treatment blood was recirculated for eight hours through closed circuits using polyacrylonitrile membranes (AN69). The effect of CVVH and CVVHD on cytokine removal from the circuits was compared.

Measurements

The concentrations of interleukins (IL)-1ß, 6, 8, 10 and TNF were measured in the control samples, pre-and post-filter and in the effluent at baseline and hourly thereafter. The clearances by adsorption, and filtration were calculated.

Results

Control cytokine concentrations remained the same or increased slightly. Adsorption was the major mechanism of removal for all cytokines with the exception of IL-1ß, but the effect was short-lived. Peak adsorption generally occurred at baseline before the start of CVVH and CVVHD, with clearances ranging from 43.7ml/min (for IL-8) to 7.6ml/min (for IL-10). The time-weighted average total clearances during CVVH were 23.3, 4.3, 3.8, –2.0, and 15ml/min for IL-8, IL-1ß, TNF, IL-6, and IL-10 respectively. The corresponding clearances during CVVHD were 19.0, 10.7, 2.7, 2.4, and 0.3ml/min. IL-10 clearances were greater during CVVH than CVVHD (p=0.03). Non adsorptive CVVH clearance of IL-1ß was greater than CVVHD clearance, but this advantage was outweighed by an increased tendency of the membrane to release IL-1ß into the circuit during HF.

Conclusions

The technique of solute removal had only a minor effect on the magnitude of cytokine adsorption, and neither technique had the advantage for all the measured cytokines.

Techniques of extracorporeal cytokine removal: a systematic review of the literature

BACKGROUND AND AIMS

Attempts at achieving cytokine homeostasis include blood purification to deliver cytokine removal. Assessment of ex vivo studies for optimal operating conditions is a vital step.

METHODS

We conducted a systematic search for ex vivo studies on cytokine removal using known modalities of extracorporeal circulation. We selected 29 articles and analyzed data according to clearance, sieving coefficient, ultrafiltrate concentration and percentage removal.

RESULTS

We identified four main techniques for cytokine removal: standard techniques, high cut-off (HCO) techniques, adsorption techniques and combined plasma filtration adsorption. HCO hemofiltration (HCO/HF) showed greatest consistency in cytokine removal among all approaches. Mean albumin clearance with HCO filters was 3.74 ml/min.

CONCLUSION

Ex vivo data support the view that HCO/HF is the most consistently effective approach in terms of sieving and clearance. Further investigation of HCO/HF in randomized controlled trials in animal models and humans seems desirable.

Development of sorbent therapy for multiple organ dysfunction syndrome (MODS)

As a syndrome, multiple organ dysfunction (MODS) is defined as an altered organ function in the setting of sepsis, septic shock or systemic inflammatory response syndrome (SIRS) and is the most common cause of death in intensive care units. Endotoxin, a constituent of cell walls of Gram-negative bacteria, plays an important role in the initiation and development of MODS. The cytokines, especially tumor necrosis factor alpha (TNF-alpha), are early regulators of the immune response and can induce the release of secondary cytokines. To remove endotoxin and TNF-alpha from patients with MODS, the adsorption method has proven to be most effective. In this review, we provide various methods of removal of endotoxins and TNF-alpha using different adsorbents.

Chromatographic removal of endotoxin from protein solutions by polymer particles

Endotoxins, constituents of cell walls of gram-negative bacteria, are potential contaminants of the protein solutions originating from biological products. Such contaminants have to be removed from solutions used for intravenous administration, because of their potent biological activities causing pyrogenic reactions. Separation methods used for decontamination of water, such as ultrafiltration, have little effect on endotoxin levels in protein solutions. To remove endotoxin from a solution of high-molecular-mass compounds, such as proteins, the adsorption method has proven to be most effective. In this review, we first introduce endotoxin-specific properties in an aqueous solution, and then provide various methods of chromatographic separation of endotoxins from cellular products using polymer adsorbents. We also provide the design of novel endotoxin-specific polymer adsorbents.

Review of methods to remove protein-bound substances in liver failure

A wide range of toxic substances accumulates in the circulation of patients with liver failure, including more lipid-soluble substances, which bind to plasma proteins. Serum albumin is the most important binding protein for ligands such as bilirubin and bile acids, which are potentially toxic and can cause apoptosis in astrocytes and hepatocytes respectively in vitro. Resin haemoperfusion was originally investigated to remove these compounds, as well as inflammatory cytokines. Current effective methods for removal of protein-bound compounds in patients with liver failure include high volume plasmapheresis and different forms of albumin dialysis. Bioartificial liver support systems need adsorbent and/or dialysis modules to replace the lack of excretory function.

Endotoxin and cytokine removal in sepsis

Sepsis, the leading cause of mortality in intensive care units, is a complex series of interrelated effects caused by the overproduction of multiple mediators and their unrestrained biological activity. Both proinflammatory and antiinflammatory mediators participate in the high complexity of sepsis and explain the failure of specific therapies to improve survival. Continuous extracorporeal therapies have been proposed as therapeutic options and as tools for blood purification in sepsis. Along these lines and in order to achieve higher clearances and mass removal rates, we studied the effects of plasmafiltration coupled with adsorption and provided in vitro and in vivo evidence that adsoprtion of multiple cytokines, activated complement components, and lipid mediators such as the platelet-activating factor occurs. We also showed that such treatment may lead to improved survival in a rabbit model of sepsis and to improved hemodynamics, reduced norepinephrine dose, and restoration of near-to-normal responsiveness of blood leukocytes to endotoxin in humans. It is anticipated that treatment of plasma, as a modular device to conventional hemofiltration, may pave the way to innovative approaches in the extracorporeal treatment of septic patients.

Hepatorenal syndrome. Definition, pathophysiology, and intervention

Hepatorenal syndrome is a well characterized entity in which vasodilation of splanchnic vessels and intense constriction of the renal cortical vasculature occur in concert. The condition is often fatal unless orthotopic liver transplantation (OLT) is performed. Many extracorporeal blood purification techniques exist which can be offered to patients awaiting OLT. Continuous hemofiltration, with or without other modalities such as therapeutic plasma exchange and hemoperfusion, may be helpful in improving the level of consciousness of these patients. Unfortunately, mortality and hepatic regeneration do not appear to be affected by such interventions. The development of a hybrid bioartifical liver support system and pharmacologic manipulation of the hemodynamic perturbations that occur in HRS provide particularly appealing prospects as a means of providing a bridge to liver transplantation in the future.

Artificial liver support devices for fulminant liver failure

Artificial liver-support devices attempt to bridge patients with fulminant hepatic failure until either a suitable liver allograft is obtained for transplantation or the patient's own liver regenerates sufficiently to resume normal function. It is thought that toxins contribute to the clinical picture of fulminant hepatic failure. The earliest reports of successful toxin removal were blood- and plasma-exchange transfusions. Given these successful case reports, mechanical liver-support devices were designed to filter toxins. These mechanical devices used hemodialysis, charcoal hemoperfusion, hemoperfusion through cation-exchange resins, hemodiabsorption, and combinations of all of these techniques as in the MARS liver-support device. Despite promising case reports and small series, no controlled studies of mechanical devices have ever showed a long-term survival benefit. Thus, the removal of presumed toxins seems to be insufficient to support patients with fulminant hepatic failure, and the biologic function of the liver must also be replaced. Attempts at replacing the biologic function have included extracorporeal liver perfusion, cross-circulation, and hepatocyte transplantation. Current technologies have combined mechanical and biologic support systems in hybrid liver-support devices. The mechanical component of these hybrid devices serves both to remove toxins and to create a barrier between the patient's serum and the biologic component of the liver-support device. The biologic component of these hybrid liver support devices may consist of liver slices, granulated liver, or hepatocytes from low-grade tumor cells or porcine hepatocytes. These biologic components are housed within bioreactors. Currently the most clinically studied bioreactors are those that use capillary hollow-fiber systems. Both the bioartificial liver by Demetrious and the extracorporeal liver-assist device by Sussman and Kelly are in clinical trials. Although the trials seemed to have yielded good survival data when the devices are used as a bridge to transplantation, the type and degree of liver support provided by these devices remains uncertain. Thus, despite decades of great progress in the field of artificial liver support, no one technique alone yet provides sufficient liver support. A hybrid system seems to be the best option at present. Still to be determined is the best tissue to use, how much liver tissue should be used, and the optimal design of the bioreactor.

Selective adsorption of endotoxin inside a polycationic network of flat-sheet microfiltration membranes

For the removal of remaining amounts of endotoxin, sorbents with high selectivity for endotoxin are required. Typically, particulate sorbents with positively charged ligands, such as histidine, polymyxin B poly-L-lysine and poly(ethyleneimine) (PEI), display moderate to high removal efficiencies in an environment of low ionic strength. It was found that polycationic ligands are most suitable to meet an endotoxin concentration which is below the threshold level required for parenteralia. Furthermore, protein recoveries close to 100% are obtained if the decontamination is performed at a pH close to the pI of acidic proteins. The high selectivity is probably caused by complexation of the polycationic ligand with the polyanionic endotoxin, leading to interactions with KD < 10(-9) M using PEI and assuming M(r) = 10 kDa for monomeric endotoxin; with BSA the same ligand reveals only KD = 4 x 10(-6) M. Using polymer-coated microfiltration membranes, immobilization of positively charged ligands leads to membrane adsorbers which are generally superior to chromatographic adsorbers and allow faster processing. Since immobilization takes place at polymer chains, low-molecular-weight ligands mainly add positive charges to the hydrophilic polymer. Consequently, membrane adsorbers with low-molecular-weight ligands, even DEAE, demonstrate similar selectivity to PEI or poly-L-lysine.

Renal replacement therapies

Slow continuous renal replacement therapy is more hemodynamically stabilizing and is replacing conventional hemodialysis as the therapy of choice for acute renal failure in the intensive care unit. This article presents practical information, including basic terminology, basic physiology, technical aspects, and indications for and application of this technique.

Non-renal indications for continuous renal replacement therapy

While there is clear support for the use of continuous renal replacement therapy (CRRT) in critically ill acute renal failure patients, there are other illnesses without renal involvement where CRRT might be of value. These include sepsis and other inflammatory syndromes such as acute respiratory distress syndrome (ARDS) and cardiopulmonary bypass where removal of inflammatory mediators by hemofiltration is hypothesized to improve outcome. Adsorption appears to be the predominant mechanism of mediator elimination. However, the observed hemodynamic improvement can, at least partially, be attributed to a reduction of body temperature or to fluid removal, and the evidence for a clinically important removal of proinflammatory cytokines remains limited. Continuous and therefore smooth fluid removal may improve organ function in ARDS, after surgery with cardiopulmonary bypass, and in patients with refractory congestive heart failure. Continuous removal of endogenous toxins, eventually combined with intermittent hemodialysis, is probably beneficial in inborn errors of metabolism, severe lactic acidosis, or tumor lysis syndrome.

Hemofiltration treatment for sepsis: is it time for controlled trials?

While the use of hemofiltration to treat septic shock has potential benefits, the existing studies are difficult to compare because of their variety of inclusion criteria. The concept is to remove the various mediators of severe sepsis and septic shock, such as cytokines and eicosanoids, so that acute renal failure and the resultant multi-organ failure and possible death can be delayed or prevented. The dilemmas include: (a) hemofiltration cannot distinguish between these pro-inflammatory mediators as they are of similar molecular weights, and thus it is difficult to determine which one or combination should be eliminated for the best hemodynamics; (b) timing of the hemofiltration to remove a particular cytokine may make a difference in patient outcome; (c) the most efficacious convection rate of ultrafiltration has not been determined yet; (d) since these mediators quickly saturate the membrane, it should be frequently changed, and thus biocompatibility, availability and costs are added issues; (e) the choice of buffer is different according to the diagnosis of these critically ill patients. Before designing clinical trials, further experimentation is necessary to explore these problems.

Review article: liver support systems in acute hepatic failure

The treatment of acute hepatic failure has developed rapidly over the last 40 years, reducing morbidity and mortality from this syndrome. Whilst this has been partly attributed to significant improvements in the specialist medical management of these patients, advances in surgical techniques and pharmaceutical developments have led to the establishment of successful liver transplantation programmes, which have improved mortality significantly. This review will examine the clinical impact of alternative methods that have been used to provide extra-corporeal hepatic support. Non-biological, bio- logical and hybrid hepatic extra-corporeal support will be explored, offering a comprehensive historical overview and an appraisal of present and future advances.

Removal of detergent and solvent from solvent-detergent-treated immunoglobulins

The solvent-detergent (S/D) method was applied for inactivation of lipid-enveloped viruses during the production of immunoglobulins. Amberlite XAD-7 resin was used for removal of solvent (tri-n-butyl phosphate, TnBP) and detergent (Triton X-100) after the performed S/D inactivation procedure. The S/D reagents from the immunoglobulin preparation were adsorbed on Amberlite XAD-7, while immunoglobulins passed through the column and retained their biological activity. Using the method developed here, the final immunoglobulin preparation contains less than 1 ppm of Triton X-100 and less than 2 ppm TnBP.

Removal of endotoxin and cytokines by plasma exchange in patients with acute hepatic failure

OBJECTIVES

To compare the circulating concentrations of endotoxin and cytokines in patients with fulminant hepatitis and patients with the severe form of acute hepatitis, and to assess the effects of plasma exchange on the circulating concentrations of these inflammatory mediators in patients with acute hepatic failure.

DESIGN

Prospective, consecutive entry study of patients meeting fulminant hepatitis criteria and the severe form of acute hepatitis criteria.

SETTING

University hospital, intensive care unit.

PATIENTS

Five patients with fulminant hepatitis, eight patients with the severe form of acute hepatitis, two patients with acute-on-chronic hepatic failure, and one patient with postoperative hepatic failure.

INTERVENTIONS

Plasma endotoxin, serum tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 were determined on admission in five patients with fulminant hepatitis and eight patients with the severe form of acute hepatitis. Circulating concentrations of the inflammatory mediators were measured before and after a single course of plasma exchange in eight patients with acute liver failure, including five patients with fulminant hepatitis, two patients with acute-on-chronic hepatic failure, and one patient with postoperative hepatic failure.

MEASUREMENTS AND MAIN RESULTS

TNF-alpha and IL-6 in patients with fulminant hepatitis were significantly higher than in patients with the severe form of acute hepatitis, whereas endotoxin concentrations did not differ between patients with fulminant hepatitis or the severe form of acute hepatitis. IL-1beta was not detectable in patients with either fulminant hepatitis or the severe form of acute hepatitis. Plasma endotoxin concentrations decreased immediately after plasma exchange. Serum concentrations of TNF-alpha and IL-6 were significantly lower after plasma exchange than before plasma exchange.

CONCLUSION

TNF-alpha and IL-6 may be important in the pathogenesis of the clinical symptoms that differentiate fulminant hepatitis from the severe form of acute hepatitis, and plasma exchange removes these inflammatory mediators from the circulation of patients with severe liver disease.

Mediator removal with CRRT: complement and cytokines

The evidence from animal sepsis models that hemofiltration may ameliorate the hemodynamic changes that occur in septic shock has led to speculation that continuous renal replacement therapy may have nonrenal benefits in septic patients. Much of the subsequent work has been done to elucidate the mechanisms of this benefit, in particular the role of removal of inflammatory mediators including cytokines and complement. The significance of extracorporeal removal of such products is dependent on the relative importance of endogenous production and clearance in the setting of sepsis and multiple organ failure and on the method of blood purification. This article reviews the evidence thus far, consisting of in vitro, animal, and human studies; a range of mediators (TNFalpha, IL-1beta, IL-6, IL-8, complement factors C3a, C5a, and D); various membranes (polyacrylonitrile, polysulfone, and polyamide); and clearance by diffusion, convection, and adsorption. The most consistent results suggest that the plasma levels of some mediators are lowered by a combination of membrane adsorption and convection, the clinical significance of which is still uncertain. The review shows the need for further work to unravel the role of CRRT in treating septic patients.

Relevance of platelet-activating factor in inflammation and sepsis: mechanisms and kinetics of removal in extracorporeal treatments

Sepsis can be considered a systemic inflammatory response syndrome (SIRS) caused by infection. When an excessive and/or persistent activation of humoral and cellular mechanisms of host defense is present, an exaggerated and generalized activation of inflammatory mechanisms can lead to a multiple organ dysfunction syndrome. Mediators thought to be involved in this syndrome include the major plasma cascade systems (complement, coagulation, and fibrinolytic systems) and soluble cell-derived mediators (cytokines, reactive oxygen species, platelet-activating factor (PAF), arachidonic acid metabolites, and nitric oxide and related compounds). Several findings indicate that among these mediators, PAF may exert an important role in the pathophysiology of septic shock. Evidence is accumulating that in human sepsis this scenario is far more complicated and that removal of inflammatory mediator excess from plasma, rather than blockade of their potentially beneficial local production, might provide a rationale for the use of continuous renal replacement therapy (CRRT). There is an emerging view that CRRT should be considered in the light of broader concept (ie, the use of blood purification for the treatment of sepsis). Recent studies, performed in an experimental model of continuous arteriovenous hemofiltration with exogenous PAF, demonstrated that polysulfone membranes can adsorb substantial amounts of biologically active PAF. These studies also showed that the removal of this mediator occurs by a two-step process involving early adsorption followed by ultrafiltration. Although the removal of cytokines, such as tumor necrosis factor-alpha (TNF-alpha), remains controversial, mainly because of differences in membrane used, operational conditions, and inter- and intra-assay variability, the crucial point is that no evidence has yet been given to show real benefit from CRRT in significantly reducing the plasma concentration of cytokines. The net advantage of CRRT, however, may not only be the removal of cytokines per se, but also the simultaneous elimination of cytokine-inducing substances. Experimental and human studies will be discussed as to whether extracorporeal treatments may remove an excess of circulating cytokines, either by increasing the turnover rate (the so-called high-volume hemofiltration), or by using sorbent systems to regenerate plasma filtrate.

Effect of hemocarboperfusion on organ blood flow and survival in porcine endotoxic shock

OBJECTIVE

To evaluate the effects of hemocarboperfusion on hemodynamics, organ blood flow, and survival in endotoxin shock.

DESIGN

Prospective, placebo-controlled, animal trial.

SETTING

Research laboratory in a major university teaching hospital.

SUBJECTS

Pentobarbital-anesthetized pigs.

INTERVENTIONS

Twenty-eight pentobarbital-anesthetized pigs (18.5 to 22.3 kg) received 100 micrograms/kg of Escherichia coli endotoxin (lipopolysaccharide 0127) over 30 mins. Group 1 animals (n = 14) were controls and had blood diverted through an extracorporeal circuit without activated charcoal for 60 mins after lipopolysaccharide infusion. Group 2 animals (n = 14) underwent nonpulsatile hemocarboperfusion (activated charcoal SCN-1K).

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure, cardiac output, systemic vascular resistance, mean pulmonary arterial pressure, pulmonary vascular resistance, oxygen delivery, and regional blood flow (radiolabeled microsphere technique) were determined at baseline and every 30 mins for 150 mins. Results are presented as mean +/- SD. Parameters in the two groups were compared by two-way analysis of variance. A p < .05 was considered significant. The survival rate was ten (71%) of 14 animals in group 1 compared with 14 (100%) of 14 animals in group 2 (p < .05, Fisher's exact test). The mean cardiac output at the end of hemocarboperfusion was 1.6 +/- 0.6 L/min in group 1 compared with 3.0 +/- 0.9 L/min in group 2, and remained lower in group 1 animals throughout the experiment. Pulmonary arterial pressure and pulmonary vascular resistance were lower in the hemocarboperfusion-treated animals during and after hemocarboperfusion. Systemic vascular resistance increased by 70% after lipopolysaccharide infusion and returned to baseline values in the hemocarboperfusion group but remained increased in controls. Oxygen delivery was lower in group 1 at 90 and 150 mins (287 +/- 34 vs. 478 +/- 48 mL/min and 251 +/- 24 vs. 356 +/- 21 mL/min, respectively). Blood flow rates to the brain (38.5 +/- 7.5 vs. 27.1 +/- 5.4 mL/min/100 g), large intestine (26.6 +/- 1.1 vs. 17.7 +/- 2.5 mL/ min/100 g), and adrenal cortex (200 +/- 45 vs. 139 +/- 41 mL/min/100 g) were higher in the hemocarboperfusion group at the completion of carboperfusion but not at later time points.

CONCLUSION

These data suggest that hemocarboperfusion may be of value in the treatment of septic shock.

Removal of endotoxins by affinity sorbents

Histidine, histamine and polymyxin B affinity sorbents were employed for the removal of Escherichia coli-derived endotoxins. Their effectiveness was compared with those of poly-L-lysine-Sepharose and DEAE-Sepharose. All sorbents reduced the concentration of endotoxins from an E. coli culture filtrate to tolerable levels. However, their effectiveness was not higher than that of the anion exchanger, which displayed clearance rates of up to 15,000. Endotoxin removal from protein solutions depended on the net charge of the desired protein. Lysozyme as a model for positively charged proteins enhanced endotoxin removal. In contrast, only low initial contamination levels (< 34 EU/ml) were reduced to tolerable levels from bovine serum albumin (BSA) as the negatively charged protein model owing to competition of BSA and endotoxins for adsorption sites. Hence also a low BSA recovery was observed after the treatment whereas the lysozyme recovery was almost 100%. At pH values below the isoelectric point of BSA, endotoxin removal was also more effective. The best conditions for the decontamination were found at neutral pH and low ionic strength (< or = 20 mM phosphate). Ionic forces between ligands and endotoxins are dominant at this ionic strength; hydrophobic interactions are not very effective. Hence the selectivities of all sorbents towards endotoxins are not exceptionally high. DEAE-anion exchangers are the most suitable sorbents for the removal of endotoxins from solutions accommodating positively charged proteins owing to their low cost and high capacity. Poly-L-lysine-Sepharose was most effective for the removal of small amounts of endotoxins from solutions of negatively charged proteins. The "affinity ligands" histamine, histidine and polymyxin B were effective for the removal of endotoxins from E. coli filtrate; however, their effectiveness decreased dramatically in the presence of BSA and it was lower than for poly-L-lysine- and DEAE-Sepharose in the presence of lysozyme.