Polymyxin-B hemoperfusion inactivates circulating proapoptotic factors

Removal of increased circulating CD4+CD25+Foxp3+ regulatory T cells in patients with septic shock using hemoperfusion with polymyxin B-immobilized fibers

BACKGROUND

Although sepsis-induced immunosuppression has long been considered to be a factor in the late mortality of patients with sepsis, little is known about regulatory T cell (Treg)-mediated immunosuppression and the effect of polymyxin B-immobilized fiber (PMX-F) on sepsis-induced immunosuppression. We sought to investigate the role of CD4(+)CD25(+)Foxp3(+) Tregs in septic patients, and to evaluate the effect of hemoperfusion with PMX-F on the recovery from immunosuppression owing to septic shock.

METHODS

Thirty-two septic patients who had an identified focus of infection in the abdominal cavity were enrolled in this study. Peripheral blood mononuclear cells in the septic patients were examined to evaluate the roles of Tregs and the serum cytokine levels. We also examined the effects of PMX-F therapy on CD4(+) T cells, especially Tregs and serum cytokine levels in patients with septic shock.

RESULTS

The percentage of Tregs in the CD4(+) T-cell population, and the serum IL-6 and IL-10 levels, were significantly higher among patients with septic shock compared with those without septic shock, and PMX-F therapy significantly decreased the number of Tregs, as well as the serum IL-6 and IL-10 levels. Furthermore, a significant increase in the number of CD4(+) T cells, a significant decrease in the percentage of Tregs in the CD4(+) T-cell population, and a significant decrease in the serum IL-6 and IL-10 levels 24 hours after PMX-F therapy were observed in septic shock survivors compared with nonsurvivors.

CONCLUSION

We found a major increase in the percentage of Tregs in peripheral blood circulating CD4(+) T cells from patients with septic shock, and observed that the removal of Tregs by hemoperfusion with PMX-F might represent a novel strategy for inducing recovery from the immunosuppression associated with sepsis.

Novel polymyxin derivatives are less cytotoxic than polymyxin B to renal proximal tubular cells

The emergence of very multiresistant Gram-negative bacterial strains has reinstated polymyxins (polymyxin B, colistin), pentacationic lipopeptides, in the therapy, in spite of their nephrotoxicity. Extensive tubular reabsorption concentrates polymyxin in proximal tubular cells. The novel polymyxin derivatives NAB739, NAB7061 and NAB741 have their cyclic part identical to that of polymyxin B, but their side chain consists of uncharged octanoyl-threonyl-d-serinyl, octanoyl-threonyl-aminobutyryl, and acetyl-threonyl-D-serinyl respectively. In this study, we compared the toxicities of NAB739, NAB7061 and NAB741 with that of polymyxin B by using the porcine renal proximal tubular cell line LLC-PK1 electroporated or incubated with the selected compound. Both the ability to cause cell necrosis (quantified as the leakage of lactate dehydrogenase) and the ability to cause apoptosis (as quantified by counting apoptotic nuclei) were assessed. In electroporated cells, polymyxin B induced total (>85%) necrosis of the cells at 0.016 mM, whereas an approx. 8-fold concentration of NAB739 and NAB7961 and an approx. 32-fold concentration of NAB741 was required for the same effect. In cells treated without electroporation (incubated), polymyxin B elicited a marked degree (approx. 50%) of necrosis at 0.5mM, whereas the NAB compounds were inert even at 1mM. Neither polymyxin B nor the NAB compounds induced apoptosis.

Polymyxin B-immobilized fiber column hemoperfusion therapy for septic shock

Endotoxin, an outer membrane component of gram-negative bacteria, plays an important role in the pathogenesis of septic shock. Endotoxin adsorption therapy by polymyxin B-immobilized fiber column hemoperfusion (PMX) has been used for the treatment of septic shock patients in Japan since 1994. The covalent binding of polymyxin B onto the surface of the polystyrene-based carrier fiber in PMX inactivates the endotoxin in the blood without exerting toxicity. This study was performed as a systematic review to evaluate the efficacy and mechanism of PMX treatment in patients with septic shock. The PubMed database and references from identified articles were used to search and review the literature relating to the efficacy and mechanism of PMX treatment in patients with septic shock. Polymyxin B-immobilized fiber column hemoperfusion adsorbed monocytes, activated neutrophils, and anandamide, as well as endotoxin through direct covalent bond, hydrophobic and ionic interactions, and hydrodynamics, and reduced the blood concentrations of inflammatory cytokines, plasminogen activator inhibitor 1 and adhesion molecules. Polymyxin B-immobilized fiber column hemoperfusion increased blood pressure and reduced the dosage requirements for vasopressive/inotropic agents. The meta-analysis showed that PMX treatment had beneficial effects on the hemodynamics, pulmonary oxygenation, and mortality. These beneficial effects may be attributable to the direct adsorption of endotoxin, monocytes, activated neutrophils, and anandamide, as well as indirect decrease in inflammatory cytokines and other mediators. Polymyxin B-immobilized fiber column hemoperfusion treatment has additional effects on reducing endothelial damage, proapoptotic activity, and immunosuppression. Further studies will be needed to confirm the efficacy and mechanism of PMX treatment in septic shock.

Cost-effectiveness analysis of polymyxin-B immobilized fiber column and conventional medical therapy in the management of abdominal septic shock in Italy

INTRODUCTION

Severe abdominal sepsis and septic shock are common problems in intensive care units (ICUs), and carry high mortality. The purpose of this economic analysis was to determine the cost-effectiveness of polymyxin B immobilized fiber column (PMX-F) plus conventional therapy (CT) (PMX-F-CT) versus CT alone for patients with severe sepsis/septic shock of abdominal origin, in the perspective of the Italian hospital.

METHODS

This was a retrospective cost-effectiveness analysis (CEA) based on data of clinical efficacy and consumption of resources collected alongside an Italian randomized clinical trial. 64 patients were enrolled following emergency surgery for intra-abdominal infection in 10 tertiary care ICUs from December 2004 to December 2007. Direct medical costs analyzed in the study included the consumption of hospital days, ICU days, catecholamine treatment days, renal replacement therapy days, mechanical ventilation treatment days, and the use of the PMX-F device. Resources were valued using published 2010 tariffs and market values. All-cause hospital mortality was extrapolated to survival as expected life years (LY) per patient/arm: for each survivor, average age-gender-related years of life expectancy were retrieved from national life tables; for deceased patients, only the number of CRF reported survival days was retained. Baseline expected years of survival were weighed by the severity of sepsis, according to individual Acute Physiology and Chronic Health Evaluation (Apache) II scores, showing that age/disease severity were comparable in the two groups before treatment initiation. Life expectancy per patient in each treatment group was thus calculated as the combination of life expectancy from Italian National Statistics Institute life tables and intra-hospital mortality detected in the Early Use of Polymyxin B Hemoperfusion in Abdominal Septic Shock (EUPHAS) study. After all costs and 3% discounted survival years were calculated per patient per treatment arm, the incremental CEA was run to obtain the incremental cost-effectiveness ratio (ICER). Univariate sensitivity analyses and 2,000 bootstrap replications were run to test the robustness of the study results.

RESULTS

Based on the expected survival years (mean discounted PMX-F-CT 9.37 LY/patient, CT 4.92 LY/patient; difference for PMX-F-CT 4.45 LY/patient; mean undiscounted PMX-F-CT 13.92 LY/patient, CT 7.19 LY/patient; difference +6.73 LY/patient), and the expected mean cost (PMX-F-CT mean 59,922 EUR/patient, CT mean 42,712 EUR/patient; difference for PMX-F-CT 17,211 EUR/patient), the mean ICER for PMX- F-CT resulted in 3,864 EUR/life year gained (LYG; ICER 2,558/undiscounted LYG). Results of the base-case CEA were confirmed by all sensitivity analyses, with ICER values always well below commonly accepted value thresholds.

CONCLUSION

PMX-F-CT versus CT is a cost-effective intervention for treatment of severe sepsis/septic shock of abdominal origin and could be considered for use in the Italian National Health System hospital setting.

Extracorporeal therapies in sepsis

The treatment of sepsis is an ongoing challenge for clinicians; despite the wide choice of effective antibiotics to treat infection, sepsis remains the leading cause of morbidity and mortality for patients admitted to an intensive care unit. Dysregulation of the immune response is now recognized to be a key factor in multiple organ dysfunction, yet our therapy for inflammation remains ineffective. It has been advocated for more than a decade that cytokine reduction in blood compartment could lead to a reduction in mortality in sepsis. Over the years, multiple extracorporeal techniques have evolved, with the intent of influencing the circulating levels of inflammatory mediators like cytokines and chemokines, the complement system, as well as factors of the coagulation system. These include high-volume hemofiltration, use of high cutoff membranes, and systems based on adsorption, such as coupled plasma filtration adsorption and the polymyxin-B column. In addition, new experimental systems that utilize human phagocytic cells and immobilized antibodies for targeted immunomodulation have emerged. In the context of limited resources and growing expansion in the availability of technologies, a better understanding of these therapies is required before they can be properly integrated into standard clinical practice in the hope of influencing major clinical outcomes. In this article, we will provide a concise overview of selected extracorporeal modalities currently in clinical use and briefly introduce some new promising techniques for sepsis.

Adsorption of various antimicrobial agents to endotoxin removal polymyxin-B immobilized fiber (Toraymyxin®)

The presence/absence of adsorption of 9 representative types of antimicrobial agent used in combination with a polymyxin-B immobilized fiber (PMX-F) were determined and the degree of adsorption to PMX-F was quantitatively evaluated. Various antimicrobial agents were dissolved at appropriate concentrations, and PMX-F was added to each solution and incubated at 37°C. Antimicrobial solutions without PMX-F were also similarly incubated as controls. After 2 and 4h, the concentration of each antimicrobial agent was determined using HPLC. To produce an environment closer to the in vivo state, albumin or serum was added, and similar evaluation was performed. In the presence of albumin, the rate of adsorption to PMX-F was relatively high for Cefmetazon(®), Pentcillin(®), Ciproxan(®) and Zyvox(®). In the presence of serum, the adsorption rate was 4.02±2.83% for Pentcillin(®), 5.59±1.00% for Ciproxan(®), and 22.12±3.23% for Zyvox(®). The results of this study suggest that adequate caution is necessary on the clinical use of Zyvox(®), which was adsorbed in the presence of serum as an environment close to the in vivo environment, but the use of other antimicrobial agents in combination with PMX-F may have only slight influences on adsorption to PMX-F.

Toll-like receptor-4 antagonist eritoran tetrasodium for severe sepsis

The human innate immune system initiates inflammation in response to bacterial molecules, particularly Gram-negative bacterial endotoxin. The steps by which endotoxin exposure leads to systemic inflammation include binding to Toll-like receptor-4 that specifically recognizes endotoxin and subsequently triggers cellular and molecular inflammatory responses. Severe sepsis is a systemic inflammatory response to infection that induces organ dysfunction and threatens a person's survival. Severe sepsis is frequently associated with increased blood levels of endotoxin. It is a significant medical problem that effects approximately 700,000 patients every year in the USA, resulting in 250,000 deaths. Eritoran tetrasodium is a nonpathogenic analog of bacterial endotoxin that antagonizes inflammatory signaling by the immune receptor Toll-like receptor-4. Eritoran is being evaluated for the treatment of patients with severe sepsis.

Septic AKI in ICU patients. diagnosis, pathophysiology, and treatment type, dosing, and timing: a comprehensive review of recent and future developments

Evidence is accumulating showing that septic acute kidney injury (AKI) is different from non-septic AKI. Specifically, a large body of research points to apoptotic processes underlying septic AKI. Unravelling the complex and intertwined apoptotic and immuno-inflammatory pathways at the cellular level will undoubtedly create new and exciting perspectives for the future development (e.g., caspase inhibition) or refinement (specific vasopressor use) of therapeutic strategies. Shock complicating sepsis may cause more AKI but also will render treatment of this condition in an hemodynamically unstable patient more difficult. Expert opinion, along with the aggregated results of two recent large randomized trials, favors continuous renal replacement therapy (CRRT) as preferential treatment for septic AKI (hemodynamically unstable). It is suggested that this approach might decrease the need for subsequent chronic dialysis. Large-scale introduction of citrate as an anticoagulant most likely will change CRRT management in intensive care units (ICU), because it not only significantly increases filter lifespan but also better preserves filter porosity. A possible role of citrate in reducing mortality and morbidity, mainly in surgical ICU patients, remains to be proven. Also, citrate administration in the predilution mode appears to be safe and exempt of relevant side effects, yet still requires rigorous monitoring. Current consensus exists about using a CRRT dose of 25 ml/kg/h in non-septic AKI. However, because patients should not be undertreated, this implies that doses as high as 30 to 35 ml/kg/h must be prescribed to account for eventual treatment interruptions. Awaiting results from large, ongoing trials, 35 ml/kg/h should remain the standard dose in septic AKI, particularly when shock is present. To date, exact timing of CRRT is not well defined. A widely accepted composite definition of timing is needed before an appropriate study challenging this major issue can be launched.

Effective use of polymyxin B hemoperfusion in septic shock complicated by urosepsis

Direct hemoperfusion using polymyxin B–immobilized fiber (PMX-DHP) is an established treatment method for septic shock caused by Gram-negative infections. Here we report one instance in which PMX-DHP therapy has been used successfully in a patient with septic shock from urosepsis. After antibiotic therapy, direct hemoperfusion using polymyxin B helped in cardiovascular stability. The patient recovered from the shock within a few days after treatment with polymyxin-B hemoperfusion. As far as we are aware, this is the first reported case of effective treatment of urosepsis complicated by septic shock using PMX-DHP therapy in India.

Preventing acute kidney injury after noncardiac surgery

PURPOSE OF REVIEW

In surgical patients, outcome is strictly dependent on the occurrence of postoperative complications, and a postoperative failing kidney has a significant independent effect on outcome. Acute kidney injury (AKI) occurs in 1% of noncardiac surgical patients and is commonly associated with more serious complications. It is important to prevent AKI wherever possible.

RECENT FINDINGS

The mainstay of postoperative AKI prevention is perioperative maintenance of blood volume with adequate cardiac output by hemodynamic monitoring and fluids/inotropes infusion. There is a growing interest for pharmacological and metabolic interventions. Most interventions, however, have been predominantly evaluated in cardiac surgery and no definite conclusion can be translated in other settings. Tight control of glycemia is still matter of debate and a role, if any, may be limited to cardiac surgical patients.

SUMMARY

Adopting adequate nephroprotective strategies is favored by knowing the moment of the actual insult to the kidney. Nevertheless, in the literature too many areas of uncertainty still exist due to the lack of renal risk stratification, of adequately powered studies, of uniform AKI definition, and of appropriate sample composition. The only recommendation for renal protection still consists in maintaining an optimal blood volume and an adequate cardiac output.

Acute kidney injury: current perspectives

Acute kidney injury (AKI) increases morbidity and mortality, particularly for the critically ill. Recent definitions standardizing AKI to reflect graded changes in serum creatinine and urine output (per the Risk, Injury, Failure, Loss, and End-stage renal failure [RIFLE] and Acute Kidney Injury Network [AKIN] criteria) with severity of renal injury and developments in AKI pathobiology are being utilized to identify biomarkers of early kidney injury. These developments may be useful in the early intervention of preventing AKI. Although there has been progress in the management of AKI, therapeutic challenges include appropriate prophylaxis prior to contrast administration, use of diuretics, vasopressors, and the type and dose of renal replacement therapy. Future use of bioartificial dialyzers, plasma therapies, and the possibility of stem cell regeneration of injured kidney tissue are being actively investigated to provide alternative treatment options for AKI. This review aims to provide an overview of current practices, available therapies, and continued research in AKI therapy.

Endotoxin removal devices for the treatment of sepsis and septic shock

A substantial body of experimental and clinical evidence suggests that neutralising or removing lipopolysaccharide endotoxin would be an effective adjunctive approach to the management of Gram-negative sepsis. Polymyxins are a group of cyclic cationic polypeptide antibiotics. Although they have useful antimicrobial activity against Gram-negative bacteria, their clinical use has been limited because of toxicity. However, in addition to their antimicrobial property, polymyxins can bind to and neutralise endotoxin. Thus, investigators have explored the possibility of using polymyxin bound to a solid-phase carrier for specific haem-adsorption in patients with sepsis, thereby retaining the lipopolysaccharide-binding properties but minimising systemic toxic effects. This system has been widely used in Japan for many years, but convincing clinical evidence of efficacy is lacking. A recent Italian study has some promising data. Although polymyxin has been the principal agent used to explore this approach, other molecules have the ability to bind endotoxin, and some of these have very recently been proposed as the basis for other endotoxin-removal devices. The available evidence is reviewed to assess the potential use of such devices in clinical practice.

Histopathology of septic shock induced acute kidney injury: apoptosis and leukocytic infiltration

PURPOSE

Septic shock is one of the leading causes of acute kidney injury. The mechanisms of this injury remain mostly unknown notably because of the lack of data on renal histological lesions in humans.

METHODS

Kidney biopsy was performed immediately post-mortem in consecutive patients who died of septic shock. Comparisons were made with specimens from eight patients who died of trauma on scene and nine ICU patients that died of non-septic causes.

RESULTS

Nineteen septic patients were included, 11 were male, and age was 72 +/- 12 years. Anuria occurred in all patients 2.2 +/- 1.4 days before death. Seven patients had disseminated intravascular coagulation. In all patients we observed (1) acute tubular lesions whose intensity correlated with blood lactate concentration; (2) intense infiltration by leukocytes, mainly monocytic, in glomeruli and interstitial capillaries as compared to controls; (3) presence of tubular cell apoptosis proved by the presence of apoptotic bodies (2.9% of tubular cells) significantly more frequently than in controls and confirmed by TUNEL and activated caspase-3 staining. Arteriolar/arterial thromboses were observed in only 4 of 19 patients, without any association with presence of disseminated intravascular coagulation.

CONCLUSIONS

Kidney lesions in septic shock go beyond those associated with simple acute tubular injury, notably capillary leukocytic infiltration and apoptosis. Vascular thrombosis, however, did not appear to play a major role in the majority of patients. The extent to which these lesions are specific to sepsis or are common to all multi-organ failure independent of its cause is yet to be elucidated. Electronic supplementary material The online version of this article (doi:10.1007/s00134-009-1723-x) contains supplementary material, which is available to authorized users.

Targeting endotoxin in the treatment of sepsis

The role of endotoxin in the genesis of sepsis has long been recognized and multiple treatments aimed at neutralizing it have been studied. Endotoxin can be bound by antibodies (whose role as a therapeutic agent is unlikely), binding proteins such as BPI or human lactoferrin (effectiveness debated and promising respectively) and phospholipid emulsion (which has not improved outcomes in a recent study). Alternatively, the action of endotoxin could be blocked by lipid A analogs (initial study showed no overall benefit and another large trial is near completion targeting a subpopulation of that study). Finally, endotoxin can be bound by polymyxin B embedded in hemoperfusion cartridges. The later treatment has been used for more than a decade in Japan. Since both pre-clinical rationale and studies support the targeting of endotoxin to ameliorate the pro-inflammatory and pro-coagulation response of severe sepsis, this therapeutic intervention is being pursued.

Effects of polymyxin B-immobilized fiber using a rat cecal ligation and perforation model

We evaluated the efficacy of polymyxin B-immobilized fiber (PMX-F) on organ dysfunction using a rat cecal ligation and perforation (CLP) model. Fifteen-week-old Sprague-Dawley rats (n = 21) were divided into three groups. For a PMX group, n = 7, peritonitis was induced by CLP. After 24 hours from CLP, endotoxin adsorption was performed for 1 hour with a PMX-F column. A sham group, n = 7, external circulation was performed with nonimmobilized fiber column. A control group, n = 7, were sacrificed 25 hours after CLP (no hemoperfusion performed). The changes in interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-alpha and plasminogen activator inhibitor (PAI)-1 were measured. The lungs, liver, and kidneys were stained with hematoxylin and eosin and anti-PAI-1 antibodies. Terminal uridine-triphosphate nick-end labeling assay was performed to evaluate apoptosis. The PMX group showed a tendency to decrease in blood levels of IL-6 and PAI-1 compared with the sham group. Anti-PAI-1 antibody staining was seen in the lungs of the control and sham groups. The PMX group showed significantly decreased apoptotic cells in renal tubule cells compared with sham and control groups. We conclude that PMX-F may have inhibited PAI-1 expression in the lungs and decreased apoptosis of renal tubule cells.

Clinical review: RIFLE and AKIN--time for reappraisal

In recent years, the use of the consensus definitions of acute kidney injury (RIFLE and AKIN) in the literature has increased substantially. This indicates a highly encouraging acceptance by the medical community of a unifying definition for acute kidney injury. This is a very important and positive step in the right direction. There remains some variation in how the criteria are interpreted and used in the literature, including use/nonuse of urine output criteria, use of change in estimated glomerular filtration rate rather than change in creatinine, and choice of baseline creatinine. The present review is intended to aid the reader in critically appraising studies using these consensus definitions. Since no single definition will be perfect, a logical next step would be to reconcile existing definitions, moving the medical community towards using a single consensus definition as has been done with sepsis and acute lung injury/acute respiratory distress syndrome. As new data emerge, integration of novel biomarkers into the consensus definition will be a welcome refinement.