Large-pore hemodialysis in acute endotoxin shock

High Cut-off Point Membranes in Septic Acute Renal Failure: A Systematic Review

Objectives

To review the literature on the experimental, physiological and clinical effects of blood purification with high cut-off (HCO) point membranes in septic acute renal failure (ARF).

Study Design

MEDLINE and PubMed database search combining relevant terms and integrating data from studies on the use of HCO membranes.

Setting and Population

Ex vivo studies of endotoxemia, animal studies of bacteremia and clinical studies using HCO membranes in patients with septic ARF. Selection Criteria for Studies: Original data from primary publications. Interventions: HCO membrane-based hemodialysis, hemodiafiltration or hemofiltration. Outcomes: Plasma cytokine clearance, immunological and physiological effects and safety parameters of HCO membranes.

Results

HCO membranes effectively remove cytokines from blood. Treatment using HCO membranes has beneficial effects on immune cell function and increases survival in animal models of sepsis. Preliminary clinical studies show that HCO membranes decrease plasma cytokine levels and the need for vasopressor therapy. HCO membrane-based blood purification has now been applied in four pilot randomized controlled studies of 70 patients with septic ARF with no reports of serious adverse effects.

Limitations

Because of substantial heterogeneity, no formal quantitative analysis could be performed.

Conclusions

The available evidence on HCO blood purification justifies larger randomized controlled trials in patients with septic ARF.

Cytokine removal with high cut-off membrane: review of literature

During the last decade, blood purification therapies have been proposed as an effective therapy to control the cytokines dysregulation in systemic inflammatory syndromes. Among them, the treatment with high cut-off membranes is characterized by larger pore size and more effective clearance for middle molecular weight molecules (cytokines). In this paper, we performed a thoughtful review of the literature on HCO being used for blood purification indications in all systemic inflammation syndromes. Clinical and experimental studies show that the use of high effluent flows in a pure diffusive treatment effectively removes serum cytokines with a safe profile in albumin clearance. In clinical studies, the removal of these inflammatory mediators is associated with a significant improvement in hemodynamic condition, oxygenation indices, and organ dysfunction.

Continuous renal replacement therapy in sepsis and multisystem organ failure

This study reviews the role of continuous renal replacement therapy (CRRT) in sepsis with acute kidney injury (AKI) and septic shock with multiple organ failure. In addition to the conventional aim of replacing renal function in AKI, CRRT is often used with the concept of modulating immune response in sepsis. With the intention of influencing circulating levels of inflammatory mediators like cytokines and chemokines, the complement system, as well as factors of the coagulation system, several modifications of CRRT have been developed over the last years. These include high volume hemofiltration, high adsorption hemofiltration, use of high cut-off membranes, and hybrid systems like coupled plasma filtration absorbance. One of the most promising concepts may be the development of renal assist devices using renal tubular cells for implementing renal tubular function into CRRT.

Hemodialysis membrane with a high-molecular-weight cutoff and cytokine levels in sepsis complicated by acute renal failure: a phase 1 randomized trial

BACKGROUND

Sepsis is the leading cause of acute renal failure. Intermittent hemodialysis (IHD) is a common treatment for patients with acute renal failure. However, standard hemodialysis membranes achieve only little diffusive removal of circulating cytokines. Modified membranes may enable both successful IHD treatment and simultaneous diffusive cytokine removal.

STUDY DESIGN

Double-blind, crossover, randomized, controlled, phase 1 trial.

SETTING & PARTICIPANTS

Tertiary intensive care unit. 10 septic patients with acute renal failure according to RIFLE class F.

INTERVENTION

Each patient was treated with 4 hours of high-cutoff (HCO)-IHD and 4 hours of high-flux (HF)-IHD.

OUTCOMES & MEASUREMENTS

We chose relative change in plasma interleukin 6 (IL-6) concentrations from baseline to 4 hours as the primary outcome for effective cytokine removal. We measured plasma and effluent concentrations of cytokines (IL-6, IL-8, IL-10, and IL-18) and albumin.

RESULTS

Median age was 53 years (25(th) to 75(th) percentiles, 43 to 71 years). Both treatments achieved equal control of uremia. Four hours of HCO-IHD accomplished a greater decrease in plasma IL-6 levels (-30.3%) than 4 hours of HF-IHD (1.1%; P = 0.05). HCO-IHD, but not HF-IHD, achieved substantial diffusive clearance of several cytokines (IL-6, 14.1 mL/min; IL-8, 75.2 mL/min; and IL-10, 25.5 mL/min). Such clearance also was associated with greater relative decreases in plasma IL-8 and IL-10 levels in favor of HCO-IHD (P = 0.02, P = 0.04). We found significantly greater relative changes from prefilter to postfilter plasma IL-6, IL-8, and IL-10 values in favor of HCO-IHD (P = 0.02, P = 0.01, P < 0.01). During HCO-IHD, cumulative albumin loss into the effluent was 7.7 g (25(th) to 75(th) percentiles, 4.8 to 19.6) versus less than 1.0 g for HF-IHD (P < 0.01).

LIMITATIONS

Small phase 1 trial.

CONCLUSION

In septic patients with acute renal failure, HCO-IHD achieved simultaneous uremic control and diffusive cytokine clearances and a greater relative decrease in plasma cytokine concentrations than standard HF-IHD.

Cardiac effects of endothelin receptor antagonism in endotoxemic pigs

Myocardial depression in sepsis is frequently encountered clinically and contributes to morbidity and mortality. Increased plasma levels of endothelin-1 (ET-1) have been described in septic shock, and previous reports have shown beneficial effects on cardiovascular performance and survival in septic models using ET receptor antagonists. The aim of the current study was to investigate specific cardiac effects of ET receptor antagonism in endotoxicosis. Sixteen domestic pigs were anesthetized and subjected to endotoxin for 5 h. Eight of these pigs were given tezosentan (dual ET receptor antagonist) after 3 h. Cardiac effects were evaluated using the left ventricular (LV) pressure-volume relationship. Endotoxin was not associated with any effects on parameters of LV contractile function [end-systolic elastance (Ees), preload recruitable stroke work (PRSW), powermax/end-diastolic volume (PWRmax/EDV) and dP/d tmax/end-diastolic volume (dP/d tmax/EDV)] but with impairments in isovolumic relaxation (time constant for pressure decay, tau) and mechanical efficiency. Tezosentan administration decreased Ees, PWRmax/EDV, and dP/d tmax/EDV, while improving tau and LV stiffness. Thus, dual ET receptor antagonism was associated with a decline in contractile function but, in contrast, improved diastolic function. Positive hemodynamic effects from ET receptor antagonism in acute endotoxemia may be due to changes in cardiac load and enhanced diastolic function rather than improved contractile function.

Blood purification therapy for sepsis

Accumulating evidences of underlining pathogenesis of sepsis have contributed to the therapeutic strategy for sepsis. Not only endotoxin and cytokine, but also signal transduction through Toll-like receptors could be a strategic target for the management of sepsis. Blood purification therapy including polymyxin B-immobilized hemoperfusion cartridge and continuous hemodiafiltration has shown the beneficial effect on patients with sepsis in Japan. Although they were initially designed to remove endotoxin and cytokines respectively, they might eliminate unexpected mediators responsible for sepsis. Further elucidation of mechanism and randomized controlled studies are needed to establish the role of blood purification therapy in sepsis.

Extracorporeal therapies in non-renal disease: treatment of sepsis and the peak concentration hypothesis

In the setting of intensive care, patients with acute renal failure often present a clinical picture of the systemic inflammatory response syndrome (SIRS). SIRS can be caused by bacterial stimuli or by non-microbiological stimuli that induce a significant inflammatory response. When this response is exaggerated, the patient experiences multiple organ system failure and a condition of sepsis also defined as a systemic malignant inflammation. This is mostly characterized by an invasion of cytokines and other pro-inflammatory mediators into the systemic circulation where major biological effects take place, including vasopermeabilization, hypotension and shock. At the same time, the monocyte of the septic patient seems to be hyporesponsive to inflammatory stimuli to a certain extent. In this condition, the patient faces a situation of hyperinflammation but at the same time of immunodepression expressing a clinical entity defined as counter anti-inflammatory response syndrome. The general picture of the clinical disorder is therefore better characterized by an immunodysregulation than by a simple pro- or anti-inflammatory disorder. Due to the short half-life of cytokines and other mediators spilled over into the circulation, it is extremely difficult to approach the problem at the right moment with the right pharmacological agent. For these reasons, the peak concentration hypothesis suggests that continuous renal replacement therapies, due to their continuity and unspecific capacity of removal, might be beneficial in cutting the peaks of the concentrations of both pro- and anti-inflammatory mediators, restoring a situation of immunohomeostasis. Thus the patient may benefit from a lesser degree of immunodysregulation and he/she may restore a close-to-normal capacity of response to exogenous stimuli.

Is circulating phospholipase A2 removed by large-pore continuous venovenous hemodiafiltration in septic acute renal failure?

Group II A phospholipase A2 (PLA2) produces many inflammatory lipid mediators, and the elevation in the level during sepsis has been correlated positively with the decrease in the arterial blood pressure. We studied the effect of large-pore continuous venovenous hemodiafiltration (LP-CVVHDF) on the plasma PLA2 concentration and the clearance mechanism during septic acute renal failure. The subjects were 10 consecutive patients with septic acute renal failure receiving CVVHDF. Simultaneous samples of arterial, and filter inlet and outlet blood, and ultradiafiltrate were collected before starting CVVHDF (0 hr), and 4 hr, 12 hr and 24 hr after starting CVVHDF. PLA2 activity was measured in plasma and ultradiafiltrate. We eluted PLA2 bound to hemofilter from patient and the classification of PLA2 type of eluting solution and ultradiafiltrate was done using Western blot analysis. Plasma clearance (mL/min) was 28.1+/-7.6 at 4 hr, 23.2+/-8.9 at 12hr and 17.5+/-8.0 at 24 hr. Plasma clearance at 4 hr was higher than that at either 12 hr or 24 hr. Plasma clearance mainly consisted of adsorption by LP-CVVHDF. The changes in arterial plasma PLA2 activity were not statistically significant. One mg/mL of heparin eluted PLA2 bound to the large-pore hemofilter. The PLA2 in eluting solution and in ultradiafiltrate were identified as an approximately 70 kD band in Western blot analysis using anti-human secretory II A-PLA2 monoclonal antibody. The results show that circulating PLA2 can be removed by adsorption with LP-CVVHDF to some extent and that plasma PLA2 activity is not significantly decreased. Because PLA2 clearance with LP-CVVHDF is estimated as <1% of total body PLA2 clearance, LP-CVVHDF could not be a clinically efficient therapy to remove the circulating PLA2.

Cytokine removal in septic patients with continuous venovenous hemofiltration

Despite the progress that has been made in intensive care medicine, multiple organ failure is still associated with high mortality. Apart from the prevention of infectious complications, numerous efforts are being made to improve the treatment of sepsis through adequate antibiotic therapy, the development of new respirator therapies, better control of the hemodynamic situation, and adequate renal replacement therapy. Some authors advocate continuous renal replacement therapy not only for acute renal failure but also for the elimination of inflammatory molecules such as cytokines. Continuous renal replacement therapy improves the cardiovascular hemodynamics in patients with multiple organ failure. Therapeutic options such as volume control, clearance of uremic toxins, correction of acid base disturbances and temperature control are improved. Suitable renal replacement therapy improves not only cardiovascular hemodynamics but also patient survival. In current practice, continuous renal replacement therapy is not used to eliminate mediators such as cytokines. In patients with multiple organ failure and compromised cardiovascular hemodynamics, renal replacement therapy should be carried out as early as possible. In the following review, experimental and clinical findings concerning mediator elimination by continuous and intermittent renal replacement therapy are summarized.

Interpreting the mechanisms of continuous renal replacement therapy in sepsis: the peak concentration hypothesis

Severe sepsis and septic shock are the primary causes of multiple organ dysfunction syndrome (MODS), which is the most frequent cause of death in intensive care unit patients. Many water-soluble mediators with pro- and anti-inflammatory action such as TNF, IL-6, IL-8, and IL-10 play a strategic role in septic syndrome. In intensive care medicine, blocking any one mediator has not led to a measurable outcome improvement in patients with sepsis. CRRT is a continuously acting therapy, which removes in a nonselective way pro- and anti-inflammatory mediators; "the peak concentration hypothesis" is the concept of cutting peaks of soluble mediators through continuous hemofiltration. Furthermore, there is evidence of increased efficacy of high-volume hemofiltration compared to conventional CVVH, and other blood purification techniques that utilize large-pore membranes or sorbent plasmafiltration are conceptually interesting.

Acute renal failure and multiple organ dysfunction in the ICU: from renal replacement therapy (RRT) to multiple organ support therapy (MOST)

Renal replacement therapy (RRT) has evolved from the concept that we need to treat the dysfunction of a single organ (the kidney). As intensive care units have become more and more complex, it has become clear that the majority of patients with acute renal failure often have dysfunction of several other organs. In order to facilitate single organ support in this setting, continuous renal replacement therapy (CRRT) techniques have been developed. However, CRRT has opened the door to the concept that targeting renal support as the only goal of extracorporeal blood purification may be a simplistic view of our therapeutic aims. In this article we argue that it is now time to move from the simple goal of achieving adequate renal support. The proper goal of extracorporeal blood purification in ICU should be multi-organ support therapy (MOST). We explain why MOST represents the most logical future conceptual and practical evolution of CRRT and illustrates the biological rationale, supplying animal and clinical evidence that confirms the need to move rapidly in this direction theoretically, practically and technologically.

Artificial organ treatment for multiple organ failure, acute renal failure, and sepsis: recent new trends

Sepsis remains the major cause of mortality worldwide, claiming millions of lives each year. The past decade has seen major advances in the understanding of the biological mechanisms involved in this complex process. Unfortunately, no definitive therapy yet exists that can successfully treat sepsis and its complications. At variance with targeting single mediators, therapeutic intervention aimed at the nonselective removal of pro- and anti-inflammatory mediators seems a rational concept and a possible key to successful extracorporeal therapies. A further advantage may lie in the continuous nature of such therapy. With such continuous therapy, sequentially appearing peaks of systemic mediator overflow may be attenuated and persistently high plasma levels reduced. This theoretical framework is proposed as the underlying biological rationale for a series of innovative modalities in sepsis. In this editorial, we will review recent animal and human trials that lend support to this concept. We will also review the importance of treatment dose during continuous renal replacement therapy as a major factor affecting survival in critically ill patients with acute renal failure. Additionally, we will review novel information related to other blood purification techniques using large pore membranes or plasma filtration with adsorbent perfusion. Although these approaches are still in the early stages of clinical testing, they are conceptually promising and might represent an important advance.

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.