The use Prometheus FPSA system in the treatment of acute liver failure: preliminary results

Extracorporeal blood purification in patients with liver failure: Considerations for the low-and-middle income countries of Latin America

Severe liver failure is common in Low-and-Medium Income Countries (LMIC) and is associated with a high morbidity, mortality and represents an important burden to the healthcare system. In its most severe state, liver failure is a medical emergency, that requires supportive care until either the liver recovers or a liver transplant is performed. Frequently the patient requires intensive support until their liver recovers or they receive a liver transplant. Extracorporeal blood purification techniques can be employed as a strategy for bridging to transplantation or recovery. The most common type of extracorporeal support provided to these patients is kidney replacement therapy (KRT), as acute kidney injury is very common in these patients and KRT devices more readily available. However, because most of the substances that the liver clears are lipophilic and albumin-bound, they are not cleared effectively by KRT. Hence, there has been much effort in developing devices that more closely resemble the clearance function of the liver. This article provides a review of various non-biologic extracorporeal liver support devices that can be used to support these patients, and our perspective keeping in mind the needs and unique challenges present in the LMIC of Latin America.

The Potential Clinical Use of Stem/Progenitor Cells and Organoids in Liver Diseases

The liver represents the most important metabolic organ of the human body. It is evident that an imbalance of liver function can lead to several pathological conditions, known as liver failure. Orthotropic liver transplantation (OLT) is currently the most effective and established treatment for end-stage liver diseases and acute liver failure (ALF). Due to several limitations, stem-cell-based therapies are currently being developed as alternative solutions. Stem cells or progenitor cells derived from various sources have emerged as an alternative source of hepatic regeneration. Therefore, hematopoietic stem cells (HSCs), mesenchymal stromal cells (MSCs), endothelial progenitor cells (EPCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are also known to differentiate into hepatocyte-like cells (HPLCs) and liver progenitor cells (LPCs) that can be used in preclinical or clinical studies of liver disease. Furthermore, these cells have been shown to be effective in the development of liver organoids that can be used for disease modeling, drug testing and regenerative medicine. In this review, we aim to discuss the characteristics of stem-cell-based therapies for liver diseases and present the current status and future prospects of using HLCs, LPCs or liver organoids in clinical trials.

Artificial liver support systems

Artificial liver systems are used to bridge between transplantation or to allow a patient's liver to recover. They are used in patients with acute liver failure (ALF) and acute-on-chronic liver failure. There are five artificial systems currently in use: molecular adsorbent recirculating system (MARS), single-pass albumin dialysis (SPAD), Prometheus, selective plasma filtration therapy, and hemodiafiltration. The aim is to compare existing data on the efficiency of these devices. A literature search was conducted using online libraries. Inclusion criteria included randomized control trials or comparative human studies published after the year 2000. A systematic review was conducted for the five individual devices with a more detailed comparison of the biochemistry for the SPAD and MARS systems. Eighty-nine patients were involved in the review comparing SPAD and MARS. Results showed that there was an average reduction in bilirubin (-53 μmol/L in MARS and -50 μmol/L in SPAD), creatinine (-19.5 μmol/L in MARS and -7.5 μmol/L in SPAD), urea (-0.9 mmol/L in MARS and -0.75 mmol/L in SPAD), and gamma-glutamyl transferase (-0.215 μmol/L·s in MARS and -0.295 μmol/L·s in SPAD) in both SPAD and MARS. However, there was no significant difference between the changes in the two systems. This review demonstrated that both MARS and SPAD aid recovery of ALF. There is no difference between the efficiency of MARS and SPAD. Because of the limited data, there is a need for more randomized control trials. Evaluating cost and patient preference would aid in differentiating the systems.

Management of Amanita phalloides poisoning: A literature review and update

Amanita phalloides poisoning with a high mortality is a serious health problem in the world. The typical clinical manifestations are usually characterized by the absence of any symptoms followed by severe gastrointestinal disorders and acute liver failure. Inhibition of RNA polymeraseII (RNAP II) activity, apoptosis, and oxidative stress are considered as the major mechanism of amatoxins intoxication. The current treatment measures mainly include prevention of amatoxins absorption, elimination of absorbed amatoxins, potential antidotes therapy, and liver transplantation. Nevertheless, there are no widely accepted treatment criteria for Amanita phalloides poisoning. This paper will focus on the treatment measures based on the previous studies and provide the currently available information for clinicians.

Prometheus: From Legend to the Real Liver Support Therapy

Background

A large number of patients develop liver disease that may evolve into progressive chronic failure. Artificial liver support systems (e.g., MARS and Prometheus) are considered in the framework of the steady increase in the number of patients who could possibly benefit from these blood purification devices. Albumin dialysis and adsorption are now two integrated concepts. The present know-how enabling us to appropriately modify several intrinsic characteristics of the adsorbents - e.g., their chemical nature, the particle and pore size distribution, as well as a larger surface offered to adsorption - has helped in better fine-tuning liver support systems to improve adsorption kinetics and flow characteristics specifically for the intended clinical application. These properties together with an improved biocompatibility have made possible the development of adsorptive techniques for which clearances and total removal rates of target compound would be unthinkable with conventional hemodialysis or hemofiltration. Several adsorptive techniques are already available commercially for the treatment of sepsis and septic shock and of acute liver failure, but controlled studies with clinical end points are still lacking.

Extracorporeal Liver Support Systems in Paediatric Liver Failure

Extracorporeal liver support systems (ELSS), encompassing artificial and bioartificial devices, have been used for decades, with the aim of supporting patients with acute liver failure and acute-on chronic liver failure, as a bridge to recovery (acute liver failure only) or liver transplantation, in an era of organ donation shortage. Although biochemical efficacy has been consistently demonstrated by these devices, translation into clinical and survival benefits has been unclear, due to study limitations and lack of reliable prognostic scoring in liver failure. Consequently, extracorporeal devices are not widely accepted as routine therapy in adult liver failure. Recent large multicentre trials using artificial liver systems have not revealed beneficial outcomes associated with albumin dialysis but plasma exchange practices have shown some potential. In paediatric liver failure, data on extracorporeal systems is scarce, comprising few reports on albumin dialysis (namely, Molecular Adsorbent Recirculating System; MARS) and plasma exchange. When extrapolating data from adult studies differences in disease presentation, aetiology, prognosis and the suitability, and safety of such devices in children must be considered. The aim of this review is to critically appraise current practices of extracorporeal liver support systems to help determine efficacy in paediatric liver failure.

Efficacy of coupled low-volume plasma exchange with plasma filtration adsorption in treating pigs with acute liver failure: A randomised study

BACKGROUND & AIMS

Extracorporeal blood purification systems for supportive therapy of liver failure are widely used. We developed a novel blood purification system, named Li's artificial liver system (Li-ALS), which couples low-volume plasma exchange (low-volume PE) with plasma filtration adsorption (PFA). This study aims to evaluate the efficacy of our novel system in pigs with acute liver failure (ALF).

METHODS

Thirty-two pigs were infused with D-galactosamine (1.3g/kg) to induce ALF. All animals were equally and randomly divided into four groups: the ALF control group received intensive care, the PFA group underwent five hour plasma recycling filtration and adsorption purification, the low-volume PE group received one hour low-volume PE, and the Li-ALS group underwent one hour low-volume PE, followed by five hour PFA. Intervention was initiated 36hours after drug administration. The efficacy of each treatment was assessed by survival time and improvement in hematological, biochemical, and immunohistological parameters.

RESULTS

Pigs in the Li-ALS group survived longer than those in the other groups (p<0.001, ALF control: 60±2h; PFA group: 74±2h; low-volume PE group: 75±2h; and Li-ALS group: 90±3h). Liver enzyme, bilirubin, bile acid and blood ammonia levels were decreased significantly after Li-ALS treatment, and increases in inflammatory cytokines were ameliorated. A higher hepatocyte regeneration index was also observed in the Li-ALS group.

CONCLUSION

Our novel Li-ALS could expedite liver regeneration and improve survival time; hence, it could be promising for treating ALF.

Liver depurative techniques: a single liver transplantation center experience

BACKGROUND

In a liver transplant (LT) center, treatments with Prometheus were evaluated. The main outcome considered was 1 and 6 months survival.

METHODS

During the study period, 74 patients underwent treatment with Prometheus; 64 were enrolled, with a mean age of 51 ± 13 years; 47 men underwent 212 treatments (mean, 3.02 per patient). The parameters evaluated were age, sex, laboratorial (liver enzymes, ammonia) and clinical (model for end-stage liver disease and Child-Turcotte-Pugh score) data.

RESULTS

Death was verified in 23 patients (35.9%) during the hospitalization period, 20 patients (31.3%) were submitted to liver transplantation, and 21 were discharged. LT was performed in 4 patients with acute liver failure (ALF, 23.7%), in 7 patients with acute on chronic liver failure (AoCLF, 43.7%), and in 6 patients with liver disease after LT (30%). Seven patients who underwent LT died (35%). In the multivariate analysis, older age (P = .015), higher international normalized ratio (INR) (P = .019), and acute liver failure (P = .039) were independently associated with an adverse 1-month clinical outcome. On the other hand, older age (P = .011) and acute kidney injury (P = .031) at presentation were both related to worse 6-month outcome. For patients with ALF and AoCLF we did not observe the same differences.

CONCLUSIONS

In this cohort, older age was the most important parameter defining 1- and 6-month survival, although higher INR and presence of ALF were important for 1-month survival and AKI for 6-month survival. No difference was observed between patients who underwent LT or did not have LT.

Cell and tissue engineering for liver disease

Despite the tremendous hurdles presented by the complexity of the liver's structure and function, advances in liver physiology, stem cell biology and reprogramming, and the engineering of tissues and devices are accelerating the development of cell-based therapies for treating liver disease and liver failure. This State of the Art Review discusses both the near- and long-term prospects for such cell-based therapies and the unique challenges for clinical translation.

Liver support systems--a review

Liver failure is associated with a high morbidity and mortality rate and is the seventh leading cause of death worldwide. Orthotopic liver transplantation remains the definitive treatment; however, because of the limited number of available organs many patients expire while on the transplant list. Currently, there are no established means for providing liver support as a means of bridging patients to transplantation or allowing for recovery from liver injury. Analogous to the clinical situation of renal failure, there is great interest in developing liver support systems that replace the metabolic and waste removal functions of the liver. These support systems are of two general types: artificial and bioartificial livers. In this review, based on a presentation from the 57th American Society of Artificial Internal Organs Annual Meeting (Washington, D.C., June 2011), we review the current status of liver support systems.

Evaluation of a novel hybrid bioartificial liver based on a multi-layer flat-plate bioreactor

AIM: To evaluate the efficacy and safety of a hybrid bioartificial liver (HBAL) system in the treatment of acute liver failure.

METHODS: Canine models with acute liver failure were introduced with intravenous administration of D-galactosamine. The animals were divided into: the HBAL treatment group (n = 8), in which the canines received a 3-h treatment of HBAL; the bioartificial liver (BAL) treatment group (n = 8), in which the canines received a 3-h treatment of BAL; the non-bioartificial liver (NBAL) treatment group (n = 8), in which the canines received a 3-h treatment of NBAL; the control group (n = 8), in which the canines received no additional treatment. Biochemical parameters and survival time were determined. Levels of xenoantibodies, RNA of porcine endogenous retrovirus (PERV) and reverse transcriptase (RT) activity in the plasma were detected.

RESULTS: Biochemical parameters were significantly decreased in all treatment groups. The TBIL level in the HBAL group was lower than that in other groups (2.19 ± 0.55 μmol/L vs 24.2 ± 6.45 μmol/L, 12.47 ± 3.62 μmol/L, 3.77 ± 1.83 μmol/L, P < 0.05). The prothrombin time (PT) in the BAL and HBAL groups was significantly shorter than the NBAL and control groups (18.47 ± 4.41 s, 15.5 ± 1.56 s vs 28.67 ± 5.71 s, 21.71 ± 3.4 s, P < 0.05), and the PT in the HBAL group was shortest of all the groups. The albumin in the BAL and HBAL groups significantly increased and a significantly higher level was observed in the HBAL group compared with the BAL group (27.7 ± 1.7 g/L vs 25.24 ± 1.93 g/L). In the HBAL group, the ammonia levels significantly decreased from 54.37 ± 6.86 to 37.75 ± 6.09 after treatment (P < 0.05); there were significant difference in ammonia levels between other the groups (P < 0.05). The levels of antibodies were similar before and after treatment. The PERV RNA and the RT activity in the canine plasma were all negative.

CONCLUSION: The HBAL showed great efficiency and safety in the treatment of acute liver failure.

Use of the molecular adsorbent recirculating system (MARS™) for the management of acute poisoning with or without liver failure

INTRODUCTION

There is an increasing interest in recent developments in bioartificial and non-bioartificial devices, so called extracorporeal liver assist devices, which are now used widely not only to increase drug elimination, but also to enhance the removal of endogenous substances in acute liver failure. Most of the non-bioartificial techniques are based on the principle of albumin dialysis. The objective is to remove albumin-bound substances that could play a role in the pathophysiology of acute liver failure by dialysing blood against an albumin-containing solution across a high flux permeable membrane. The most widely used device is the Molecular Adsorbent Recirculating System (MARS™).

METHODS

The relevant English and French literature was identified through Medline using the terms, 'molecular adsorbent recirculating system', 'MARS', 'acute liver failure', 'acute poisoning', 'intoxication'. This search identified 139 papers of which 48 reported on a toxic cause for the use of MARS™. Of these 48 papers, 39 specified the substance (eighteen different substances were identified); two papers reported on the same group of patients. BIOARTIFICIAL AND NON-BIOARTIFICIAL SYSTEMS: Bioartificial systems based on porcine hepatocytes incorporated in the extracorporeal circuit are no longer in use due to the possibility of porcine retroviral transmission to humans. Historically, experience with such devices was limited to a few cases of paracetamol poisoning. In contrast, an abundant literature exists for the non-bioartificial systems based on albumin dialysis. The MARS™ has been used more widely than other techniques, such as the one using fractionated plasma separation and adsorption (Prometheus™). All the extracorporeal liver assist devices are able to some extent to remove biological substances (ammonia, urea, creatinine, bilirubin, bile acids, amino acids, cytokines, vasoactive agents) but the real impact on the patient's clinical course has still to be determined. Improvement in cardiovascular or neurological dysfunction has been shown both in acute liver failure and acute-on-chronic liver failure but no impact on mortality has been reported. ACUTE POISONING WITH LIVER FAILURE: Randomized controlled trials are very limited in number and patients poisoned by paracetamol or Amanita phalloides are usually included for outcome analysis in larger groups of acute liver failure patients. Initial results look promising but should be confirmed. Beyond its effect in liver failure, MARS™ could also enhance the elimination of the drug or toxin responsible for the failure, as is described with paracetamol. ACUTE POISONING WITHOUT LIVER FAILURE: Extracorporeal liver assist devices have also been used to promote elimination of drugs that are highly protein bound. Data in various case reports confirm a high elimination of phenytoin, theophylline and diltiazem. However, definite conclusions on the toxicokinetic or clinical efficacy cannot be drawn.

CONCLUSIONS

Despite the lack of large multicentre randomized trials on the use of MARS™ in patients with acute liver failure, the literature shows clinical and biological benefit from this technique. In drug or toxin-induced acute liver failure, such as paracetamol or mushroom poisoning, MARS™ has been used extensively, confirming in a non-randomized fashion, the positive effect observed in the larger population of acute liver failure patients. Furthermore, as MARS™ has been shown in experimental studies to remove protein-bound substances, it is potentially a promising treatment for patients with acute poisoning from drugs that have high protein-binding capacity and are metabolized by the liver, especially, if they develop liver failure concomitantly.

Artificial extracorporeal liver support therapy in patients with severe liver failure

Severe liver failure is common and carries a high mortality risk in patients with both acute and acute-on-chronic liver failure. The failing liver constitutes a medical emergency, and in many cases liver transplantation is the only definite treatment. Extracorporeal liver support can be employed as a strategy for bridging to transplantation or recovery. This article focuses on options for artificial (nonbiological) extracorporeal treatment: single-pass albumin dialysis, fractionated plasma separation and adsorption (Prometheus(®)) and the molecular adsorbent recirculatory system. Their different principles, potential advantages and indications are discussed. Despite proven biochemical efficacy, there are little data regarding clinical end points. Thus far, molecular adsorbent recirculatory system therapy in acute and acute-on-chronic liver failure showed no survival benefit compared with standard medical therapy. Prometheus therapy showed reduced mortality in subgroups of higher severity of disease compared with standard medical therapy. Nevertheless, the value of extracorporeal liver support remains to be corroborated by further clinical studies that include the optimal timing, mode, intensity and duration of this treatment.

Acute liver failure and liver assist devices

Survival of patients presenting with acute liver failure (ALF) has improved over the past decades due to earlier disease recognition, advances in supportive measures, intensive care, and liver transplantation. Liver assist devices may have a role in future care of patients with ALF, bridging them to recovery or to transplantation. A multidisciplinary team approach to the care of patients with ALF is critical for achieving good patient outcomes.

The treatment of acute liver failure with fractionated plasma separation and adsorption system: Experience in 85 applications

INTRODUCTION

Artificial liver support systems represent a potential useful option for the treatment of liver failure. The outcomes of patients treated with the fractionated plasma separation and adsorption (FPSA) system are presented.

PATIENTS AND METHODS

FPSA was performed 85 times for 27 patients (median 3 treatments/patient) with liver failure [85.2% acute liver failure (ALF) and 14.8% acute-on-chronic liver failure] using the Prometheus 4008H (Fresenius Medical Care) unit. Citrate was used for anticoagulation. A variety of clinical and biochemical parameters were assessed. Comparisons between pretreatment and post-treatment data were performed using paired t-test.

RESULTS

The 85 sessions had a mean duration of 6 h. There were significant decreases in total bilirubin (13.18 +/- 9.46 mg/dL vs. 9.76 +/- 7.05 mg/dL; P < 0.0001), ammonia (167.6 +/- 75 mg/dL vs. 120 +/- 43.8 mg/dL; P < 0.0001), blood urea nitrogen (BUN; 12.55 +/- 13.03 mg/dL vs. 8.18 +/- 8.15 mg/dL; P < 0.0001), creatinine (0.54 +/- 0.47 mg/dL vs. 0.46 +/- 0.37 mg/dL; P = 0.0022) levels, and in pH (7.48 +/- 0.05 vs. 7.44 +/- 0.08; P = 0.0045). Four patients (14.8%) received liver transplantation after the treatments; in nine patients, transplantation was not necessary anymore (33%); the remaining 14 patients did not receive a transplantation because they were either not appropriate candidates or no organ was available. Overall survival was 48.1% (4 transplanted and 9 treated patients). No hematological complications related to FPSA were observed.

CONCLUSIONS

FPSA system is a safe and effective detoxification method for patients with liver dysfunction, including ALF. The system is useful as a symptomatic treatment before liver transplantation; in up to 1/3 of the cases, it can even be used as a sole method of treatment.

[Evaluation of extracorporeal liver support systems in the treatment of liver failure. A systematic review]

OBJECTIVE

To evaluate the safety and efficacy of the MARS and Prometheus extracorporeal liver support systems in the treatment of liver failure.

DESIGN

We performed a systematic review of the literature from January 1999 to June 2009 in the Medline, Embase, HTA, DARE, NHSEED, Cochrane Library Plus, Clinical Trials Registry and HSRPROJ databases. Study selection was based on a series of previously established inclusion criteria related to the study design, population, type of intervention, language, and outcome measures.

PATIENTS AND INTERVENTIONS

Patients with acute liver failure or acute exacerbations of chronic liver failure treated with the MARS or Prometheus systems.

OUTCOME MEASURES

Data on safety, long-term survival, clinical effects and biochemical and hemodynamic variables.

RESULTS

We selected 22 studies evaluating the safety and efficacy of the MARS and Prometheus systems. Adequate evaluation of these techniques was hampered by the heterogeneity of the studies and their methodological limitations.

CONCLUSIONS

Extracorporeal liver support systems are able to purify both hydrosoluble and protein-bound substances. However, current data show that only the MARS system reduces mortality in acute liver failure and in acute exacerbations of chronic liver failure, although this reduction is non-significant. These techniques can be considered safe, with adverse effects similar to those of the control group. Their main indication is severe liver failure, for short periods while the liver recovers or a liver transplant becomes available.

Results of treatment of acute liver failure patients with use of the prometheus FPSA system

OBJECTIVE

Herein we have presented the results of treatment of acute liver failure (ALF) patients with the use of the Prometheus FPSA dialysis system.

MATERIALS AND METHODS

To January 2009, we performed 278 FPSA procedures in 114 patients, including 52 experience and ALF. The patients who underwent the FPSA procedure consisted of 32 women and 20 men of overall mean age of 33 +/- 12 years. The causes of ALF were: Wilson's disease (n = 15), unknown origin ALF (n = 11), amanita phalloides intoxication (n = 7), paracetamol intoxication (n = 8), acute hepatitis B virus (HBV)/hepatitis C virus (HCV) infection (n = 7), liver insufficiency after parenchymal resection (n = 2) drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome (n = 1), rabdomyolysis (n = 1), or primary nonfunction (PNF) after orthotopic liver transplantation (OLT) (n = 1). All procedures were performed using the Prometheus 4008H Fresenius Medical Care liver support system. The average number of treatments per patient was 2.41 and the average time for each FPSA treatment was 6.3 hours. The average heparin dose used during the procedure was 750 IU/h.

RESULTS

After the whole treatment regimen, we observed significant improvements in the biochemical results. The average concentrations improved: serum ammonia (before 249.2 mug/dL versus after 109.7 mug/dL); serum bilirubin (before 21.53 mg/dL versus after 8.81 mg/dL), serum aspartate aminotransferase (AST; before 2456.4 U/L versus after 1068.8 U/L); serum alanine aminotransferase (ALT; before 2958.2 U/L versus after 1595.8 U/L); serum urea (before 58.5 mg/dL versus after 21.1 mg/dL); serum creatinine (before 2.9 mg/dL versus after 1.7 mg/dL); and pH value (before 7.11 versus after 7.32). After Prometheus treatment OLT was performed in 33 patients. Among the 28 who survived (53.8%), 22 underwent OLT and 6 did not have OLT. Among the 24 patients who died (46.2%), 13 were before OLT and 11 after OLT.

CONCLUSION

The Prometheus 4008H Fresenius Medical Care Liver support system was useful method of detoxification for patients with ALF, serving as an element of pretransplantation care.

Severe acetaminophen poisoning treated with a fractionated plasma separation and absorption system: A case report

Acetaminophen is an analgesic drug that is frequently used in suicide attempts. In this paper, we report on a 17-year-old girl who was admitted to an emergency department 15 hours after taking acetaminophen pills in a suicide attempt. Her serum acetaminophen level was 73 mg/L on admission; she had elevated liver enzymes suggesting hepatic necrosis. She was started on N-acetyl cystein (NAC), and treated successfully with a fractionated plasma separation and absorption system.

ICU management of acute liver failure

Survival of patients presenting with acute liver failure (ALF) has improved because of earlier disease recognition, better understanding of pathophysiology of various insults leading to ALF, and advances in supportive measures including a team approach, better ICU care, and liver transplantation. This article focuses on patient management and evaluation that takes place in the ICU for patients who have acute liver injury. An organized team approach to decision making about critical care delivered during this period of time is important for achieving a good patient outcome.

Extracorporeal treatment of acute liver failure

Acute liver failure (ALF) is a widespread problem with typically unfavorable prognosis. With the implementation of a liver support device in the clinical setting for treatment of patients with ALF, anticipated improvements include prolonging time available for spontaneous recovery and bridging to liver transplantation. Liver support could also serve to prevent systemic manifestations of ALF such as renal failure, pulmonary edema, systemic inflammatory response syndrome and cerebral edema evolving to brain death. Both non-cell based and cell based (bio-artificial) systems have been used in clinical trials. Systems with closed or open loop organization present different advantages and disadvantages; systems also differ in the membrane pore size for filtrate/dialysate exchange. Further optimization of liver assist devices is still required; when a system has proved to be successful in treating the debilitating results of ALF, the benefits will be enormous to liver failure patients.

Extracorporeal albumin dialysis

Patients with liver failure still present a high mortality. It can only be significantly improved by the rare resource of liver transplantation. Extracorporeal liver support devices have been developed to temporarily support liver detoxification. Artificial devices without hepatocytes ("liver dialysis" or "albumin dialysis") are already widely used in Europe. The two best-known systems, MARS and Prometheus, use a different technical approach to remove water-soluble as well as albumin-bound toxins from the blood. In MARS, toxins diffuse along a concentration gradient through an albumin-impermeable membrane into a secondary circuit that is pre-filled with an albumin solution. The albumin is continuously "recycled" inside the secondary circuit by different adsorber and low flux dialysis. In contrast, Prometheus includes an albumin-permeable filter allowing separation of the albumin fraction into the secondary circuit where the albumin-bound toxins are directly removed by two adsorbers. Thereafter, high flux dialysis is performed inside the primary circuit. For both extracorporeal systems, an improvement of hepatic encephalopathy and biochemical markers such as bilirubin is consistently reported. In-vivo comparisons of both systems showed significantly higher extraction capacities for protein-bound and water-soluble substances under Prometheus than under MARS treatment. Possible pathophysiological mechanisms could be a reduction of portal pressure or a removal of vasoactive cytokines. However, only few randomised controlled trials with low patient numbers and conflictive results regarding patient survival exist. Nevertheless, a Cochrane meta-analysis revealed a significant survival benefit for extracorporeal liver support devices in patients with acute-on-chronic liver failure. Other promising indications are severe refractory cholestatic pruritus, intoxication with protein-bound substances and graft dysfunction after liver transplantation. As large randomised controlled multi-center trials are currently underway, better evidence will be available soon to define the clinical role of extracorporeal liver support devices.

Acetaminophen-induced acute liver failure treated with single-pass albumin dialysis: report of a case

BACKGROUND

Acetaminophen (paracetamol) overdose is a leading cause of acute liver failure (ALF). When patients fulfill the King's College criteria for acetaminophen-induced ALF (AALF), they have a poor prognosis for survival without liver transplantation. Recent advances in artificial liver support have used albumin as a binding and scavenging molecule in ALF. One method, single-pass albumin dialysis (SPAD), involves dialyzing blood against an albumin-containing solution across a high-flux membrane to remove albumin-bound toxins. Herein, we describe our protocol for SPAD and report its use in a case of AALF as a bridge to native liver recovery.

CASE

A 41-year-old female with no documented history of liver disease presented with acute acetaminophen toxicity and developed hepatic encephalopathy, coagulopathy and lactic acidosis. The patient met King's College criteria for liver transplantation, based on pH and INR, but was deemed not suitable as a candidate due to psychosocial comorbidities. On day 3 of her ICU admission, she received the first of five consecutive daily runs (total ~77 hours) of SPAD. The patient's course was complicated by cerebral edema requiring mannitol. She was extubated on day 11 and transferred to the ward by day 13. At ICU discharge, her liver function (INR 1.9, bilirubin 435 mmol/L) and kidney function were recovering. She did not have any long-term neurological sequelae. By hospital discharge (day 46) her native liver function had recovered with a bilirubin <100mmol/L.

CONCLUSION

We describe a case of a patient with acetaminophen-induced acute liver failure who was successfully bridged to spontaneous native liver recovery as a result of SPAD treatment. In patients with ALF, SPAD may be an additional intervention for temporary extracorporeal support. Further investigation in larger prospective studies is warranted.

Thermodynamic considerations in solid adsorption of bound solutes for patient support in liver failure

New detoxification modes of treatment for liver failure that use solid adsorbents to remove toxins bound to albumin in the patient bloodstream are entering clinical evaluations, frequently in head-to-head competition. While generally effective in reducing toxin concentration beyond that obtainable by conventional dialysis procedures, the solid adsorbent processes are largely the result of heuristic development. Understanding the principles and limitations inherent in competitive toxin binding, albumin versus solid adsorbent, will enhance the design process and, possibly, improve detoxification performance. An equilibrium thermodynamic analysis is presented for both the molecular adsorbent recirculating system (MARS) and fractionated plasma separation, adsorption, and dialysis system (Prometheus), two advanced systems with distinctly different operating modes but with similar equilibrium limitations. The Prometheus analysis also applies to two newer approaches: sorbent suspension reactor and microsphere-based detoxification system. Primary results from the thermodynamic analysis are that: (i) the solute-albumin binding constant is of minor importance to equilibrium once it exceeds about 10(5) L/mol; (ii) the Prometheus approach requires larger solid adsorbent columns than calculated by adsorbent solute capacity alone; and (iii) the albumin-containing recycle stream in the MARS approach is a major reservoir of removed toxin. A survey of published results indicates that MARS is operating under mass transfer control dictated by solute-albumin equilibrium in the recycle stream, and Prometheus is approaching equilibrium limits under current clinical protocols.

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.

Sorbent-based artificial liver devices: principles of operation, chemical effects and clinical results

Devices for support of patients with liver failure are of two types: bioartificial livers and artificial livers. Bioartificial livers include hepatocytes in bioreactors to provide both excretory and synthetic liver functions. Artificial livers use nonliving components to remove toxins of liver failure, supply nutrients and macromolecules. Current artificial liver devices use columns or suspensions of sorbents (including adsorbents and absorbents) to selectively remove toxins and regenerate dialysate, albumin-containing dialysate, plasma filtrate or plasma. This article reviews three artificial liver devices. Liver Dialysis uses a suspension of charcoal and cation exchangers to regenerate dialysate. MARS uses charcoal and an anion exchanger to regenerate dialysate with albumin. Prometheus uses neutral and anion exchange resins to regenerate a plasma filtrate containing albumin and small globulins. We review the operating principles, chemical effects, clinical effects and complications of use of each type of artificial liver. These devices clearly improve the clinical condition of patients with acute or acute-on-chronic liver failure. Further randomized outcome studies are necessary to prove clinical outcome benefit of the artificial liver support devices, and define what types of patients appear most amenable to therapy.

The therapeutical efficiency of the newest extracorporal elimination procedure (Prometheus® treatment) in acute liver failure caused by intoxication

Az akut májelégtelenség mortalitása az intenzív terápia ellenére májtranszplantáció nélkül 60–90%. Az átültethető szervek korlátozott száma miatt azonban a betegek jelentős része a várólistán exitál. A mortalitás csökkentése érdekében számos próbálkozás történt a májelégtelenségben felhalmozódó albuminhoz kötött és vízoldékony méreganyagok eltávolítására, elősegítve ezzel a máj spontán regenerációját, illetve a beteg életben tartását a májtranszplantációig. A Prometheus®-kezelés egy viszonylag új technika, a frakcionált plazmaszeparáció és -adszorpció (FPSA) és egy high-flux dialízis kombinációja. Az eljárás során a beteg saját, szeparált, albuminban gazdag plazmája speciális adszorbereken halad keresztül, lehetővé téve az albuminhoz kötött toxinok eliminációját, miközben a vízoldékony toxinok eltávolítása hemodialízissel történik. Célkitűzés: A szerzők szándéka az volt, hogy a Prometheus®-kezelés hatékonyságát igazolják mérgezés okozta akut májelégtelenségben. Betegek és módszer: A Prometheus®-kezelést három, konzervatív kezeléssel nem uralható akut májelégtelenségben szenvedő, súlyos, paracetamol-, káliumpermanganát- és Amanita phalloides-mérgezett beteg esetében alkalmazták. Eredmények: A három nőbetegnél 10 kezelés történt. Súlyos szövődményt nem észleltek. A kezelések során az albuminhoz kötött (indirekt bilirubin p = 0,048; epesav p = 0,001) és a vízoldékony (direkt bilirubin p = 0,002; kreatinin p = 0,007) toxinok szignifikáns csökkenését tapasztalták. Az ammónia, a karbamid, a fibrinogén és az antitrombin III szint szignifikánsan nem változott. Mindhárom beteg májtranszplantáció nélkül meggyógyult. Következtetés: A Prometheus®-kezelés hatékonyan távolítja el az akut májelégtelenségben akkumulálódó toxinokat. Biztonságos eljárás. Konzervatív terápiával nem uralható esetekben lehetővé teszi a beteg életben tartását a máj spontán regenerációjáig vagy a májtranszplantációig.

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.

Anticoagulation Minimization Is Safe and Effective in Albumin Liver Dialysis Using the Molecular Adsorbent Recirculating System

The molecular adsorbent recirculating system (MARS) is a blood purification device with renal and hepatic dialytic effects. This study examined the use of low-dose unfractionated heparin in MARS. This was a prospective, observational study of 15 MARS treatment sessions (mean duration per treatment cycle = 12.2 +/- 4.5 h) in four patients with severe acute decompensation of chronic liver disease (n = 3) and fulminant hepatic failure (n = 1) treated with intermittent MARS. All patients were critically ill (APACHE II 24.8 +/- 3.3). Renal dialysis was with continuous hemofiltration and/or slow low-efficiency dialysis. One MARS session was terminated because of vascular access occlusion (1/15; 6.7%). Bleeding was noted in two sessions (2/15; 13%). Twelve MARS sessions were heparin-free and three treatments were with mean heparin dose of 833 +/- 382 IU. Serum biochemical parameters pre- and post-MARS were total bilirubin (micromol/L): 409.4 +/- 141.6 versus 282.9 +/- 90, P < 0.05; plasma ammonia (micromol/L): 44.3 +/- 21.2 versus 28.8 +/- 20.2, P = 0.002; urea (mmol/L): 15.9 +/- 11.8 versus 7.9 +/- 6.6, P = 0.002; creatinine (micromol/L): 252.4 +/- 151.9 versus 150.1 +/- 96.6, P = 0.003. Pre-MARS versus post-MARS systolic (SBPs) and diastolic (DBPs) blood pressures (mm Hg) were SBP = 129.2 +/- 27.7 versus 124 +/- 25, P = 0.838; and DBP = 60.7 +/- 15.3 versus 56 +/- 13, P = 0.595. Prothrombin time (PT), activated partial thromboplastin time (aPTT) and platelet count (Plt) pre- and post-MARS were PT(s): 22 +/- 7.9 versus 23.8 +/- 10.2, P = 0.116; aPTT (s): 64.5 +/- 40.9 versus 85.5 +/- 50.6, P = 0.092; and Plt (x10(3)/mm(3)): 87 +/- 67.6 versus 68.8 +/- 39, P = 0.098. MARS priming with heparin saline was safe. Heparin-minimized MARS did not compromise circuit function and longevity in extended intermittent MARS.