Effect of the molecular adsorbent recirculating system and Prometheus devices on systemic haemodynamics and vasoactive agents in patients with acute-on-chronic alcoholic liver failure

The future of extracorporeal support

Extracorporeal therapy has expanded significantly over the past few decades from solely artificial renal replacement therapy. In patients with multiple organ dysfunction syndrome, it becomes necessary to provide multiple organ support therapy. Technological advances have opened the door to a multifaceted intervention directed at supporting the function of multiple organs through the treatment of blood. Indications for "old" therapies such as hemofiltration and adsorption have been expanded, and using these therapies in combination further enhances blood detoxification capabilities. Furthermore, new devices are constantly in development. Nanotechnology allows us to refine membrane characteristics and design innovative monitoring/biofeedback devices. Miniaturization is leading down the path of wearable/implantable devices. With the incorporation of viable cells within medical devices, these instruments become capable not only of detoxification but synthetic functions as well, bringing us closer to the holy grail of complete replacement of organ function. This article provides a brief overview of current and future direction in extracorporeal support in the critical care setting.

Effect of Prometheus liver assist system on systemic hemodynamics in patients with cirrhosis: A randomized controlled study

AIM: To evaluate treatment safety and hemodynamic changes during a single 6-h treatment with the Prometheus™ liver assist system in a randomized, controlled study.

METHODS: Twenty-four patients were randomized to either the study group or to one of two control groups: Fractionated Plasma Separation Adsorption and Dialysis, Prometheus™ system (Study group; n = 8); Molecular Adsorbent Recirculation System (MARS)™ (Control group 1, n = 8); or hemodialysis (Control group 2; n = 8). All patients included in the study had decompensated cirrhosis at the time of the inclusion into the study. Circulatory changes were monitored with a Swan-Ganz catheter and bilirubin and creatinine were monitored as measures of protein-bound and water-soluble toxins.

RESULTS: Systemic hemodynamics did not differ between treatment and control groups apart from an increase in arterial pressure in the MARS group (P = 0.008). No adverse effects were observed in any of the groups. Creatinine levels significantly decreased in the MARS group (P = 0.03) and hemodialysis group (P = 0.04). Platelet count deceased in the Prometheus group (P = 0.04).

CONCLUSION: Extra-corporal liver support with Prometheus is proven to be safe in patients with end-stage liver disease but does not exert the beneficial effects on arterial pressure as seen in the MARS group.

The pervading influence of alcoholic liver disease in hepatology

Rising levels of alcohol consumption in the UK are leading to substantial increases in morbidity and mortality from liver disease. Drinking is starting at an earlier age with binging an increasing common pattern, and women are overtaking men in the consumption. Manifestations of liver damage range from fatty liver to end-stage cirrhosis, but it is the increasing number of cases presenting with an acute alcoholic hepatitis (AAH) that are the cause for greatest concern. Development of well-validated prognostic scoring systems (Maddrey Modified Discriminant Function, Glasgow Alcohol Score) makes it possible to select those patients with AAH who are most likely to respond to corticosteroids. The results of early pilot studies of a number of anti-TNF agents are encouraging and with infliximab, reduction in portal pressure has been demonstrated to be consequent on controlling inflammatory processes in the liver. For those deteriorating to the stage of liver failure, artificial liver support with MARS is of value in correcting major pathophysiological disturbances and as a bridge to liver transplantation, the results of which both for end-stage alcoholic cirrhosis and for AAH--of which there is limited experience, are excellent. Even as the stringent regulatory measures needed to control rising alcohol consumption are introduced by government, the burden of liver disease in the UK will remain high for years to come.

Liver support devices

PURPOSE OF REVIEW

Liver support devices are used either as a bridge to liver transplantation or liver recovery in patients with acute or acute-on-chronic liver failure. The review analyzes the recent literature and asks if the current enthusiasm for these devices is justified.

RECENT FINDINGS

Many liver support devices exist and are discussed. Clinical data on artificial devices are rapidly emerging, especially on the molecular adsorbents recirculating system, and fractionated plasma separation and adsorption (Prometheus). While hepatic encephalopathy is improved by the molecular adsorbents recirculating system and probably Prometheus too, neither system has been shown to improve survival. Less clinical data exist for bioartificial support devices. These may use human hepatocytes, such as the extracorporeal liver assist device, although most devices use porcine hepatocytes, such as HepatAssist.

SUMMARY

Enthusiasm in liver support devices is justified as many nonrandomized studies have suggested some biochemical and clinical benefits. The results of several ongoing multicenter randomized controlled trials are anxiously awaited. Meanwhile, because mortality without liver transplantation remains high despite the use of liver support devices, these devices should only be used in the research setting or by experts proficient in their use and as a bridge to liver transplantation rather than liver recovery.

Bench-to-bedside review: current evidence for extracorporeal albumin dialysis systems in liver failure

Acute liver failure (ALF) and acute on chronic liver failure (AoCLF) carry a high mortality. The rationale for extracorporeal systems is to provide an environment facilitating recovery or a window of opportunity for liver transplantation. Recent technologies have used albumin as a scavenging molecule. Two different albumin dialysis systems have been developed using this principle: MARS (Molecular Adsorbent Recirculation System) and SPAD (Single-Pass Albumin Dialysis). A third system, Prometheus (Fractionated Plasma Separation and Adsorption), differs from the others in that the patient's albumin is separated across a membrane and then is run over adsorptive columns. Although several trials have been published (particularly with MARS), currently there is a lack of controlled studies with homogenous patient populations. Many studies have combined patients with ALF and AoCLF. Others have included patients with different etiologies. Although MARS and Prometheus have shown biochemical improvements in AoCLF and ALF, additional studies are required to show conclusive benefit in short- and long-term survival. The appropriate comparator is standard medical therapy rather than head-to-head comparisons of different forms of albumin dialysis.

Hypercoagulation and thrombophilia in liver disease

A complex balance exists between endogenous procoagulants and the anticoagulant system in liver disease patients. Hypercoagulable events occur in cirrhosis patients despite the well-known bleeding diathesis of liver disease. These events may be clinically evident, such as in portal vein thrombosis or pulmonary embolism, but these conditions may also be a silent contributor to certain disease states, such as portopulmonary hypertension or parenchymal extinction with liver atrophy as well as thrombosis of extracorporeal circuits in dialysis or liver assist devices. Moreover, liver disease-related hypercoagulability may contribute to vascular disease in the increasingly common condition of non-alcoholic fatty liver disease. Despite the incidence of these problems, there are few widely accessible and practical laboratory tests to evaluate the risk of a hypercoagulable event in cirrhosis patients. Furthermore, there is little research on the use of commonly accepted anticoagulants in patients with liver disease. This article is a result of an international symposium on coagulation disorders in liver disease and addresses several areas of specific interest in hypercoagulation in liver disease. Critical areas lacking clinical information are highlighted and future areas of research interest are defined with an aim to foster clinical research in this field.

Major coagulation disturbances during fractionated plasma separation and adsorption

Fractionated Plasma Separation and Adsorption (FPSA) is a novel nonbiologic detoxification system for the removal of protein-bound solutes. FPSA is used to bridge patients during fulminant liver failure, either to functional recovery or to liver transplantation. Besides liver failure associated protein bound solutes, several important uremic retention solutes share important protein binding. We observed repeated occlusive thrombosis of the arterio-venous conduit during FPSA in hemodialysis (HD) patients, resulting in acute loss of function. A major reduction of several coagulation factors was demonstrated, exceeding 50% for factor II, factor X and protein C. Broad disturbances of the coagulation system were confirmed in FPSA treated liver failure patients. An ex vivo recirculation model demonstrated nonspecific adsorption of coagulation factors protein S and protein C on the anion exchange cartridge. Direct contact between fractionated plasma and the Prometh02 anion exchanger causes significant adsorption of procoagulant and anti-coagulant factors, associated with clinically relevant adverse events.

Vascular endothelial dysfunction in cirrhosis

Endothelial dysfunction is regarded as an early key event in multiple diseases. The assessment of vascular nitric oxide (NO) level is an indicative of endothelial dysfunction. In liver cirrhosis, on one hand, endothelial dysfunction is known as impaired endothelium-dependent relaxation in the liver microcirculation and contributes to increased intra-hepatic vascular resistance, leading to portal hypertension. On the other, increased production of vasodilator molecules mainly NO contributes to increased endothelium-dependent relaxation in the arteries of the systemic and splanchnic circulation. The aims of this review are to summarize and discuss: (1) unique characteristics of sinusoidal endothelial cell (SECs) and SEC dysfunctions in cirrhosis, and (2) endothelial dysfunctions in the arterial splanchnic and systemic circulation in cirrhosis with portal hypertension.

Technology Insight: artificial extracorporeal liver support—how does Prometheus® compare with MARS®?

Artificial extracorporeal liver support or 'liver dialysis' has been used in patients with severe liver failure with increasing frequency since the Molecular Adsorbents Recirculating System (MARS), a variant of albumin dialysis, was introduced in 1999. Nevertheless, liver dialysis must still be thought of as experimental because its contribution to improved patient survival has not been proven in large randomized trials. Prometheus is a novel device for fractionated plasma separation via an albumin-permeable filter that was developed to improve removal of albumin-bound toxins. Initial studies have proven clinical use of Prometheus to be feasible and safe. Head-to-head comparisons of Prometheus and MARS have shown treatment with the former to be more efficient with respect to removal of most albumin-bound and water-solved markers. As controlled studies with clinical end points are lacking, it is not known whether the observed greater detoxification capacity of Prometheus will translate into clinical benefit; two small studies indicate that there might be a beneficial effect in hepatic encephalopathy and pruritus. In a recent randomized comparison of MARS and Prometheus, however, hemodynamic improvement was observed in response to MARS, but not Prometheus, treatment. A large randomized controlled trial investigating the effect of Prometheus on survival--the HELIOS study--has been initiated. First results are expected in 2008 and will be crucial to establishing a role for Prometheus in the field of extracorporeal liver support.

Acute liver failure: liver support therapies

PURPOSE OF REVIEW

We summarize the therapeutic approach to patients with acute liver failure with the main focus on bioartificial and artificial liver support. We also describe specific and general therapeutic approaches based upon recent advances in the understanding of the pathophysiology of acute liver failure.

RECENT FINDINGS

Bioartificial liver support systems use hepatocytes in an extracorporeal device connected to the patient's circulation. Artificial liver support is intended to remove protein-bound toxins and water-soluble toxins without providing synthetic function. Both systems improve clinical and biochemical parameters and can be applied safely to patients. Although bioartificial liver-assist devices have not been shown to improve the survival of patients with acute liver failure, further development is underway. Artificial liver support systems have been shown to alter several pathophysiological mechanisms involved in the development of acute liver failure but survival data are still limited.

SUMMARY

Mortality in patients with acute liver failure is still unacceptably high. The most effective treatment, liver transplantation, is a limited resource and so other therapeutic options to bridge patients to recovery or stabilization have to be considered. Better understanding of the pathophysiology of acute liver failure and device development is necessary to achieve the elusive goal of effective extracorporeal liver assist.

Effect of extracorporeal liver support by MARS and Prometheus on serum cytokines in acute-on-chronic liver failure

Introduction

Cytokines are believed to play an important role in acute-on-chronic liver failure (ACLF). Extracorporeal liver support systems may exert beneficial effects in ACLF via removal of cytokines. At present, two systems are commercially available, the Molecular Adsorbent Recirculating System (MARS™) and Fractionated Plasma Separation, Adsorption and Dialysis (Prometheus™). The aim of this study was to compare the effects of MARS and Prometheus treatments on serum cytokine levels and their clearances.

Methods

Eight patients with ACLF underwent alternating treatments with either MARS or Prometheus in a randomized cross-over design. Thirty-four treatments (17 MARS, 17 Prometheus) were available for analysis. Serum cytokines were measured before and after each treatment, and cytokine clearance was calculated from paired arterial and venous samples and effective plasma flow one hour after the start of treatment.

Results

Baseline serum levels of interleukin (IL)-6, IL-8, IL-10, tumor necrosis factor-alpha (TNF-α), and soluble TNF-α receptor 1 were significantly elevated in patients with ACLF. Measurable plasma clearances were detected for all cytokines tested, but no significant changes in serum levels of any cytokine were found after treatments with MARS or Prometheus. In MARS treatments, IL-10 was cleared from plasma more efficiently than IL-6. Clearance of IL-10 was higher in Prometheus than in MARS treatments.

Conclusion

Cytokines are cleared from plasma by both MARS and Prometheus, but neither system is able to change serum cytokine levels. This discrepancy is probably due to a high rate of cytokine production in patients with ACLF.

Alcoholic steatohepatitis: management and prognosis

Alcoholic hepatitis is a disease with a wide range of severity. Patients with severe disease have short-term mortality rates above 35%. In these high-risk patients, pharmacologic therapy is an important adjunct to supportive medical care and has been proved to improve survival. Given the benefit of drug treatment, it is important to identify patients at risk of early mortality from alcoholic hepatitis. A number of validated scoring systems are useful for this purpose, including the Maddrey Discriminant Function, the Model of End-Stage Liver Disease score, and the Glasgow Alcoholic Hepatitis score. Patients judged by one or more of these criteria to have severe alcoholic hepatitis should be treated with corticosteroids or pentoxifylline, provided they have no contraindications for this treatment. Adequate nutrition is also critical and should be provided by tube feeding if necessary. A prompt decline in serum bilirubin indicates a favorable response to therapy. Patients who do not exhibit a reduction in serum bilirubin within 1 week are considered nonresponders and have a 6-month mortality rate of 50% or higher.

Treatment of hepatorenal syndrome

<zakljucak> Hepatorenalni sindrom je funkcionalna insuficijencija bubrega u sklopu terminalne insuficijencije jetre. U patogenezi ovog sindroma ucestvuju hemodinamske promene (snizeni srednji arterijski pritisak i perfuzioni pritisak bubrega) i povecano stvaranje sistemskih i bubreznih vazoaktivnih medijatora sa stimulacijom bubreznog simpatickog sistema. Standardna medicinska farmakoloska terapija usmerena je na prethodno navedene patofizioloske poremecaje. U poslednje vreme postupci detoksikacije, npr. jedan od vidova albuminske dijalize, pojavljuju se sve vise u lecenju bolesnika sa HRS, ali se jos ne preporucuju kao standardna procedura. Oba vida lecenja preduzimaju se samo kao premoscenje perioda do transplantacije jetre ili u slucajevima kada se ocekuje oporavak funkcije jetre, jer bubrezna funkcija direktno zavisi od funkcije jetre. Standardna hemodijaliza ne pomaze u poboljsanju funkcije bubrega. Jedino kauzalno resenje ovog problema donosi transplantacija jetre.