Albumin dialysis has a favorable effect on amino acid profile in hepatic encephalopathy

MARS: Should I Use It?

Severe liver failure, including acute liver failure and acute-on-chronic liver failure, is associated with high mortality, and many patients die despite aggressive medical therapy. While liver transplantation is a viable treatment option for liver failure patients, a large proportion of these patients die given the shortage in the liver donation and the severity of illness, leading to death while waiting for a liver transplant. Extracorporeal liver support devices, including molecular adsorbent recirculating system (MARS), have been developed as bridge to transplantation (bridge for patients who are decompensating while waiting for liver transplantation) and bridge to recovery (for whom recovery is deemed reasonable). In addition to its uses in acute liver failure and acute-on-chronic liver failure, the MARS system has also been applied in various clinical settings, such as drug overdosing and poisoning and intractable cholestatic pruritus refractory to pharmacological treatment. This review aims to discuss the controversies, potential benefits, practicalities, and disadvantages of using MARS in clinical practice.

Clinical effectiveness of MARS treatment - multidirectional analysis of positive clinical response to treatment

Aim of the study

Liver failure is a life-threatening condition which often requires intensive care treatment. It is essential to quickly determine whether there are indications for extracorporeal liver support systems for the patient. The aims of the study were: to assess effectiveness of molecular adsorbent recirculating system (MARS) therapy based on selected clinical criteria, to analyze the moment of clinical response and to create a patient’s profile, who will benefit clinically from the treatment.

Material and methods

The analysis encompassed medical histories of 65 patients treated with MARS. Effectiveness of treatment was evaluated based on selected clinical parameters. Statistical analysis was performed based on medical data gathered.

Results

There were 158 cycles of MARS performed, with effectiveness documented in 57 cycles (36.6%). The first MARS session was effective in 43.1% of patients. They also more often responded to the second cycle (63.6% vs. 15.4%). A significant part of the analysis was devoted to create a profile of the patient in whom positive response can be expected. A low MELD score and low baseline white blood cells (WBC) level are statistically significant factors in multivariate analysis of selected features of positive clinical response to treatment.

Conclusions

MARS therapy is an effective form of treatment in a properly selected group of patients with liver failure. The first MARS session is the most effective one. It is also a good prognostic factor for further clinical response to treatment. Multifactorial analysis of positive clinical response to treatment enables to create a patient’s profile based on the lower baseline MELD score and WBC.

Artificial liver support systems: what is new over the last decade?

The liver is a complex organ that performs vital functions of synthesis, heat production, detoxification and regulation; its failure carries a highly critical risk. At the end of the last century, some artificial liver devices began to develop with the aim of being used as supportive therapy until liver transplantation (bridge-to-transplant) or liver regeneration (bridge-to-recovery). The well-recognized devices are the Molecular Adsorbent Recirculating System™ (MARS™), the Single-Pass Albumin Dialysis system and the Fractionated Plasma Separation and Adsorption system (Prometheus™). In the following years, experimental works and early clinical applications were reported, and to date, many thousands of patients have already been treated with these devices. The ability of artificial liver support systems to replace the liver detoxification function, at least partially, has been proven, and the correction of various biochemical parameters has been demonstrated. However, the complex tasks of regulation and synthesis must be addressed through the use of bioartificial systems, which still face several developmental problems and very high production costs. Moreover, clinical data on improved survival are conflicting. This paper reviews the progress achieved and new data published on artificial liver support systems over the past decade and the prospects for these devices.

Liver dialysis in acute-on-chronic liver failure: current and future perspectives

Patients with acute-on-chronic liver failure (ACLF) are known to have a very high mortality rate as the majority of these patients succumb to multiorgan failure. Liver transplant remains the only option for these patients; however, there are problems with its availability, cost and also the complications and side effects associated with immunosuppression. Unlike advanced decompensated liver disease, there is a potential for hepatic regeneration and recovery in patients with ACLF. A liver support system, cell or non-cell based, logically is likely to provide temporary functional support until the donor liver becomes available or the failing liver survives the onslaught of the acute insult and spontaneously regenerates. Understanding the pathogenesis of liver failure and regeneration is essential to define the needs for a support system. Removal of hepatotoxic metabolites and inhibitors of hepatic regeneration by liver dialysis, a non-cell-based hepatic support, could help to provide a suitable microenvironment and support the failing liver. The current systems, i.e., MARS and Prometheus, have failed to show survival benefits in patients with ACLF based on which newer devices with improved functionality are currently under development. However, larger randomized trials are needed to prove whether these devices can enable restoration of the complex dysregulated immune system and impact organ failure and mortality in these patients.

Hepatocyte transplants improve liver function and encephalopathy in portacaval shunted rats

AIM

Rats with portacaval shunt (PCS) are useful experimental models of human hepatic encephalopathy in chronic liver dysfunction. We have previously shown that PCS modifies amine neurotransmitter systems in the CNS and increases voluntary alcohol intake by rats. Hepatocyte transplantation, used in acute liver failure, has recently also been applied to chronic liver diseases, which prompted us to investigate whether the altered brain amine system and the drinking behavior in long-term shunted rats could be normalized by hepatocyte transplants.

METHODS

Hepatocytes, isolated from syngeneic donors by collagenase digestion, were injected (3 × 10(6) cells/rat) into the pancreatic tail region, 6 months after PCS. Hepatic function was evaluated by measuring urine urea and plasma L-histidine concentrations. A free choice test with two bottles (tap water and 10% ethyl alcohol) was performed for 3 days to assess the rats' preference for alcohol. The rats were euthanized 2 months posttransplantation. Brain histamine and 5-hydroxyindoleacetic acid (5-HIAA) levels were measured by radioenzymatic assay and by HPLC-EC, respectively, N-tele-methylhistamine by GC/MS while MAOA and MAOB activities by isotopic procedures.

RESULTS

Portacaval shunt rats with hepatocyte transplants gave more urea than before transplantation, with lower plasma L-His levels and higher body weight versus the PCS counterparts. Also, those rats consumed less alcohol. The CNS amines and 5-HIAA concentrations, as well as MAO-B activity, being abnormally high in untreated PCS rats, significantly reduced after PCS hepatocyte treatment.

CONCLUSIONS

The results support the therapeutic values of hepatocyte transplants in chronic liver diseases and the temporary character of PCS-exerted CNS dysfunctions.

The effect of fractionated plasma separation and adsorption on cerebral amino acid metabolism and oxidative metabolism during acute liver failure

BACKGROUND & AIMS

Patients with acute liver failure have a disturbed amino acid metabolism and a compromised oxidative metabolism in the brain. A limited number of clinically neuroprotective interventions are available. This study aimed at assessing the effect of fractionated plasma separation and adsorption (FPSA), an extracorporeal liver support system, on cerebral amino acids and lactate to pyruvate ratio.

METHODS

Seven patients with acute liver failure and high risk of intracranial hypertension were included for cerebral microdialysis and intracranial pressure monitoring. Microdialysate, arterial blood, and venous blood from the jugular bulb were sampled, before and after an FPSA session, and the content of nineteen amino acids, lactate, and pyruvate was determined.

RESULTS

The total amino acid concentration in arterial plasma was not significantly reduced by FPSA (11.2 mM (3.0-26.0 mM) vs. 9.7 mM (2.7-13.6 mM); median with range). The total amino acid content in the microdialysate was 5.6 mM both before and after FPSA and no change in glutamine content was observed in plasma or microdialysate. The content of aromatic amino acids in arterial plasma, but not in microdialysate, was marginally reduced (p<0.05). Arterial lactate concentration and lactate to pyruvate ratio in the microdialysate did not change following FPSA.

CONCLUSIONS

One single treatment session with FPSA had a marginal effect on plasma amino acid composition. We found minimal changes in the amino acids content in the microdialysate, and the lactate to pyruvate ratio was unaffected.

Blood glutamate scavenging: insight into neuroprotection

Brain insults are characterized by a multitude of complex processes, of which glutamate release plays a major role. Deleterious excess of glutamate in the brain's extracellular fluids stimulates glutamate receptors, which in turn lead to cell swelling, apoptosis, and neuronal death. These exacerbate neurological outcome. Approaches aimed at antagonizing the astrocytic and glial glutamate receptors have failed to demonstrate clinical benefit. Alternatively, eliminating excess glutamate from brain interstitial fluids by making use of the naturally occurring brain-to-blood glutamate efflux has been shown to be effective in various animal studies. This is facilitated by gradient driven transport across brain capillary endothelial glutamate transporters. Blood glutamate scavengers enhance this naturally occurring mechanism by reducing the blood glutamate concentration, thus increasing the rate at which excess glutamate is cleared. Blood glutamate scavenging is achieved by several mechanisms including: catalyzation of the enzymatic process involved in glutamate metabolism, redistribution of glutamate into tissue, and acute stress response. Regardless of the mechanism involved, decreased blood glutamate concentration is associated with improved neurological outcome. This review focuses on the physiological, mechanistic and clinical roles of blood glutamate scavenging, particularly in the context of acute and chronic CNS injury. We discuss the details of brain-to-blood glutamate efflux, auto-regulation mechanisms of blood glutamate, natural and exogenous blood glutamate scavenging systems, and redistribution of glutamate. We then propose different applied methodologies to reduce blood and brain glutamate concentrations and discuss the neuroprotective role of blood glutamate scavenging.

The end-organ impairment in liver cirrhosis: appointments for critical care

Liver cirrhosis (LC) can lead to a clinical state of liver failure, which can exacerbate through the course of the disease. New therapies aimed to control the diverse etiologies are now more effective, although the disease may result in advanced stages of liver failure, where liver transplantation (LT) remains the most effective treatment. The extended lifespan of these patients and the extended possibilities of liver support devices make their admission to an intensive care unit (ICU) more probable. In this paper the LC is approached from the point of view of the pathophysiological alterations present in LC patients previous to ICU admission, particularly cardiovascular, but also renal, coagulopathic, and encephalopathic. Infections and available liver detoxifications devices also deserve mentioning. We intend to contribute towards ICU physician readiness to the care for this particular type of patients, possibly in dedicated ICUs.

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.

Acute-on-chronic liver failure: extracorporeal liver assist devices

PURPOSE OF REVIEW

Acute-on-chronic liver failure (ACLF), a syndrome precipitated by acute liver injury in patients with advanced cirrhosis, is associated with multiorgan dysfunction and high rates of mortality. Liver support systems have been developed in an attempt to improve survival of patients with ACLF by providing a bridge until recovery of the native liver function.

RECENT FINDINGS

Nonbiological devices such as molecular adsorbent recirculating system (MARS) and fractionated plasma separation and adsorption (Prometheus) are effective in improving severe hepatic encephalopathy and cholestasis, have good safety and tolerability profiles and are frequently employed in patients with ACLD; however, randomized controlled trials (RCTs) failed to show improvement in survival. Biologic devices that incorporate hepatic cells in bioreactors are also under development. Recent data from pilot studies suggested improvement in survival rates in some groups of patients with ACLF; however, their effect on patient survival in RCT is still unknown.

SUMMARY

Liver support systems are safe and well tolerated when used in management of patients with ACLF. Their use should continue in controlled clinical trials to explore their role in bridging patients to liver transplantation or recovery in well defined patient groups.

Continuous veno-venous single-pass albumin hemodiafiltration in children with acute liver failure

OBJECTIVE

To investigate the applicability, efficacy, and safety of single-pass albumin dialysis in children.

DESIGN

Retrospective data review of uncontrolled clinical data.

SETTING

University-based pediatric intensive care unit collaborating with a local center for liver transplantation.

PATIENTS

Nine children, aged 2 to 15 yrs, who were treated with single-pass albumin dialysis for acute liver failure of various origins under a compassionate-use protocol between 2000 and 2006. All patients met high-urgency liver transplantation criteria.

INTERVENTIONS

Single-pass albumin dialysis was performed as rescue therapy for children with acute liver failure.

MEASUREMENTS AND MAIN RESULTS

The decrease in hepatic encephalopathy (grades 1-4) and the serum levels of bilirubin, bile acids, and ammonium were measured to assess the efficacy of detoxification. As a measure of liver synthesis function, thromboplastin time and fibrinogen were analyzed. The safety of the procedure was assessed by documenting adverse effects on mean arterial blood pressure, platelet count, and clinical course. Seven out of nine patients were bridged successfully to either native organ recovery (n = 1) or liver transplantation (n = 6), one of them twice. Six out of nine patients undergoing single-pass albumin dialysis (ten treatments) survived. In six patients, hepatic encephalopathy could be reduced at least by one degree. Ammonium, bilirubin, and bile acid levels decreased in all patients. One patient had an allergic reaction to albumin.

CONCLUSIONS

In childhood acute liver failure, treatment with single-pass albumin dialysis was generally well tolerated and seems to be effective in detoxification and in improving blood pressure, thus stabilizing the critical condition of children before liver transplantation and facilitating bridging to liver transplantation. It may be beneficial in avoiding severe neurologic sequelae after acute liver failure and thereby improve survival. Single-pass albumin dialysis is an inexpensive albumin-based detoxification system that is easy to set up and requires little training. Whether and to what extent single-pass albumin dialysis can support children with acute liver failure until native liver recovery remains unclear.

Bridging Therapies and Liver Transplantation in Acute Liver Failure; 10 Years of MARS Experience from Finland

Acute liver failure is a life-threatening condition in the absence of liver transplantation option. The aetiology of liver failure is the most important factor determining the probability of native liver recovery and prognosis of the patient. Extracorporeal liver assist devices like MARS (Molecular Adsorbent Recirculating System) may buy time for native liver recovery or serve as bridging therapy to liver transplantation, with reduced risk of cerebral complications. MARS treatment may alleviate hepatic encephalopathy even in patients with a completely necrotic liver. Taking this into account, better prognostic markers than hepatic encephalopathy should be used to assess the need for liver transplantation in acute liver failure.

Branched-chain amino acids in liver disease: new aspects of long known phenomena

PURPOSE OF REVIEW

To provide an overview of findings on the role of branched-chain amino acids (BCAAs) in the pathophysiology, pathobiochemistry, and treatment of liver cirrhosis and its complications that have been published since or were not included in the last review on this topic in 2007 in this journal.

RECENT FINDINGS

There has been continued interest in the potential of oral BCAA supplements in improving energy metabolism, nitrogen metabolism, carbohydrate metabolism, insulin resistance, severity of liver disease, serum albumin levels, quality of serum albumin, or postoperative complication rates. Unfortunately, many trials suffer from lacking or inadequate controls or small sample size. In a fine example of scientific perseverance, Dutch researchers uncovered the long-known phenomenon of ingested blood being highly comagenic in patients with cirrhosis to be due to the low biologic value of blood protein. The absence of isoleucine and the abundance of leucine in the hemoglobin molecule by way of BCAA antagonism leads to impaired protein synthesis and azotemia paving the way for hepatic encephalopathy.

SUMMARY

Recognizing hypoisoleucinemia and BCAA antagonism following gastrointestinal bleeding, and its successful treatment by isoleucine infusion has advanced our understanding of the role of BCAA in liver cirrhosis.

[Intensive care of patients with acute liver failure]

BACKGROUND

Acute liver failure and acute decompensated chronic liver failure are two diseases that demand extensive knowledge of etiology and triggering factors, pathophysiology, diagnosis, prognosis and recommended guidelines for treatment. The article defines the diseases, discusses etiological factors, treatment strategies, indications for referral to the transplantation unit at Rikshospitalet and prognostic factors of importance.

MATERIAL AND METHODS

The basis for this article is literature identified through a non-systematic search in PubMed and the authors' clinical experience and experimental research within the field.

RESULTS

In the Western world paracetamol poisoning and toxic reactions to other drugs are the most common triggering factors for acute liver poisoning in adults. Patients can quickly develop multi organ failure requiring advanced intensive care. The most common complications are hepatic encephalopathy, acute renal failure and coagulation disturbances. Acute decompensated chronic liver failure strikes patients with known liver disease and is most often triggered by inflammation, infection, gastrointestinal bleeding, drugs, traumas or disturbances in acid/base/electrolyte balance. Early diagnosing of triggering factors and intensive medical supportive treatment is especially important. Acute renal failure indicates a very bad prognosis.

INTERPRETATION

Patients diagnosed with acute liver failure or acute decompensated chronic liver failure remain a clinical challenge. Optimal treatment requires extensive knowledge of pathophysiological mechanisms and treatment strategies.

1H-NMR-based metabolic signatures of clinical outcomes in trauma patients--beyond lactate and base deficit

The determination of reliable biomarkers capable to predict clinical outcome of a trauma patient remains essential toward better therapeutic management of the patient in the intensive care unit. Assessment of global metabolic profiling using quantitative nuclear magnetic resonance (NMR)-based metabolomics offers an attractive modern methodology for fast and comprehensive determination of multiple circulating metabolites and for establishing metabolic phenotype of survivors versus nonsurvivors. Multivariate data analysis on 43 quantitative metabolic parameters identified three lipid metabolites, triacylglycerol, glycerol heads of phospholipids, and monounsaturated fatty acids, as being the most discriminative markers to separate survivors versus nonsurvivors at the time of admission. Glucose and glutamate were intermediate predictors, followed by lactate and hydroxybutyrate as two low-weight predictors. Ultimately, cellular and subcellular failure in nonsurviving trauma patients results in multiple systemic biochemical effects and in changes in circulating metabolites in the blood that are characteristic for decreased lipid synthesis and urea cycle activity in the liver, and for increased hyperglycemia, lactic, and ketoacidosis.

Cost-utility of molecular adsorbent recirculating system treatment in acute liver failure

AIM: To determine the short-term cost-utility of molecular adsorbent recirculating system (MARS) treatment in acute liver failure (ALF).

METHODS: A controlled retrospective study was conducted with 90 ALF patients treated with MARS from 2001 to 2005. Comparisons were made with a historical control group of 17 ALF patients treated from 2000 to 2001 in the same intensive care unit (ICU) specializing in liver diseases. The 3-year outcomes and number of liver transplantations were recorded. All direct liver disease-related medical expenses from 6 mo before to 3 years after ICU treatment were determined for 31 MARS patients and 16 control patients. The health-related quality of life (HRQoL) before MARS treatment was estimated by a panel of ICU doctors and after MARS using a mailed 15D (15-dimensional generic health-related quality of life instrument) questionnaire. The HRQoL, cost, and survival data were combined and the incremental cost/quality-adjusted life years (QALYs) was calculated.

RESULTS: In surviving ALF patients, the health-related quality of life after treatmeant was generally high and comparable to the age- and gender-matched general Finnish population. Compared to the controls, the average cost per QALY was considerably lower in the MARS group (64 732€vs 133 858€) within a timeframe of 3.5 years. The incremental cost of standard medical treatment alone compared to MARS was 10 928€, and the incremental number of QALYs gained by MARS was 0.66.

CONCLUSION: MARS treatment combined with standard medical treatment for ALF in an ICU setting is more cost-effective than standard medical treatment alone.

Management of acute liver failure

Acute liver failure (ALF) is a syndrome of diverse etiology, in which patients without previously recognized liver disease sustain a liver injury that results in rapid loss of hepatic function. Depending on the etiology and severity of the insult, some patients undergo rapid hepatic regeneration and spontaneously recover. However, nearly 60% of patients with ALF in the US require and undergo orthotopic liver transplantation or die. Management decisions made by clinicians who initially assess individuals with ALF can drastically affect these patients' outcomes. Even with optimal early management, however, many patients with ALF develop a cascade of complications often presaged by the systemic inflammatory response syndrome, which involves failure of nearly every organ system. We highlight advances in the intensive care management of patients with ALF that have contributed to a marked improvement in their overall survival over the past 20 years. These advances include therapies that limit the extent of liver injury and maximize the likelihood of spontaneous recovery and approaches to enable prevention, recognition and early treatment of complications that lead to multi-organ-system failure, the most common cause of death. Finally, we summarize the role of orthotopic liver transplantation in salvage of the most severely affected patients.

7 Leverfalen

De lever vervult tal van essentiële functies in het menselijk lichaam, waaronder ontgifting van het bloed en aanmaak van diverse eiwitten en hormonen. Tevens speelt de lever een rol in het afweersysteem. Leverfalen kan omschreven worden als een situatie van onvoldoende werking van de lever bij deze processen. Dit beeld ontstaat wanneer door het verlies van functionele cellen het totale effectieve levervolume beneden een kritische grens komt. In dit hoofdstuk wordt ingegaan op diverse vormen van leverfalen en twee specifieke bij leverfalen voorkomende problemen, namelijk hepatische encefalopathie en verhoogde bloedingsneiging.