Treatment of severe refractory pruritus with fractionated plasma separation and adsorption (Prometheus)

Liver replacement therapy with extracorporeal blood purification techniques current knowledge and future directions

Clinically, it is highly challenging to promote recovery in patients with acute liver failure (ALF) and acute-on-chronic liver failure (ACLF). Despite recent advances in understanding the underlying mechanisms of ALF and ACLF, standard medical therapy remains the primary therapeutic approach. Liver transplantation (LT) is considered the last option, and in several cases, it is the only intervention that can be lifesaving. Unfortunately, this intervention is limited by organ donation shortage or exclusion criteria such that not all patients in need can receive a transplant. Another option is to restore impaired liver function with artificial extracorporeal blood purification systems. The first such systems were developed at the end of the 20^th century, providing solutions as bridging therapy, either for liver recovery or LT. They enhance the elimination of metabolites and substances that accumulate due to compromised liver function. In addition, they aid in clearance of molecules released during acute liver decompensation, which can initiate an excessive inflammatory response in these patients causing hepatic encephalopathy, multiple-organ failure, and other complications of liver failure. As compared to renal replacement therapies, we have been unsuccessful in using artificial extracorporeal blood purification systems to completely replace liver function despite the outstanding technological evolution of these systems. Extracting middle to high-molecular-weight and hydrophobic/protein-bound molecules remains extremely challenging. The majority of the currently available systems include a combination of methods that cleanse different ranges and types of molecules and toxins. Furthermore, conventional methods such as plasma exchange are being re-evaluated, and novel adsorption filters are increasingly being used for liver indications. These strategies are very promising for the treatment of liver failure. Nevertheless, the best method, system, or device has not been developed yet, and its probability of getting developed in the near future is also low. Furthermore, little is known about the effects of liver support systems on the overall and transplant-free survival of these patients, and further investigation using randomized controlled trials and meta-analyses is needed. This review presents the most popular extracorporeal blood purification techniques for liver replacement therapy. It focuses on general principles of their function, and on evidence regarding their effectiveness in detoxification and in supporting patients with ALF and ACLF. In addition, we have outlined the basic advantages and disadvantages of each system.

Systematic review: efficacy of therapies for cholestatic pruritus

Background

Pruritus is a symptom of several cholestatic liver diseases (CLDs) that can impair health-related quality of life (HRQoL). Despite evidence-based guideline therapy, managing cholestatic pruritus (CP) remains challenging, thus making the need for newer, more effective therapeutic agents more evident.

Objective

Our study evaluated the efficacy of existing CP therapies.

Design

Systematic review.

Data sources

From inception until March 2023, we conducted a comprehensive search of MEDLINE, Cochrane, EMBASE, Scopus, ClinicalTrial.gov, and other sources, including pharmaceutical webpages and conference proceedings published in English that reported on CP interventions.

Methods

Two reviewers independently conducted screening and full-text review of articles with extraction conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The methodological quality of studies included in our qualitative synthesis was assessed by using the Cochrane ROBINS-I and ROBINS-II tools for interventional studies and the National Heart, Lung, and Blood Institute Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. The primary outcome assessed in our systematic review was the severity of CP after therapy.

Results

Of 3293 screened articles, 92 studies were eligible for inclusion in the qualitative synthesis. Some patients' HRQoL improved with evidence-based standard therapy. Others, particularly those with severe and refractory CP, often required conversion to or addition of experimental noninvasive (e.g., ondansetron) or extracorporeal liver support to alleviate CP. In addition, studies investigating a newer class drug, the ileal bile acid transporter inhibitor (IBATi), demonstrate its effectiveness in reducing serum bile acid and alleviating CP with sustained improvement noted in patients with the inherited childhood cholestatic disorders - progressive familial intrahepatic cholestasis and Alagille syndrome.

Conclusion

Our findings consolidate data on the efficacy of guideline-based approaches and newer therapies for CP. While the initial findings are promising, additional clinical trials will be needed to determine the full extent of IBATi's efficacy and potential use in treating other common CLDs. These results provide a foundation for future research and highlight the need for continued investigation into the management and treatment of CLDs.

Efficacy of Treatments for Cholestatic Pruritus: A Systemic Review and Meta-analysis

Cholestatic itch is a disabling symptom that may be secondary to liver or biliary diseases. Management of cholestatic pruritus is complex. A systematic review and meta-analysis on the efficacy of treatments for cholestatic pruritus were performed. PubMed and Cochrane Library were searched using the algorithm “(hepatitis OR cholestatic OR liver) AND (pruritus OR itch) AND (management OR treatment OR treatments)” for 1975–2019. Of the 2,264 articles identified, 93 were included in a systematic review and 15 in a meta-analysis (studies evaluating pruritus with a visual analogue scale). Some treatments act by reducing levels of pruritogens in the enterohepatic cycle, others modify the metabolism or secretion of these pruritogens, or act on pruritus pathways. A further possible treatment is albumin dialysis. However, due to many heterogeneities in the reviewed studies it is difficult to identify and recommend an optimum treatment. Only 15 studies were included in the meta-analysis, due to the small number of randomized studies using a visual analogue scale.

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.

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.

Assessment of the Visual Analogue Score in the Evaluation of the Pruritus of Cholestasis

Background and Aims: A visual analogue score (VAS), based on application of a visual analogue scale, has been widely used to assess pruritus in clinical studies of patients with cholestatic liver disease. A VAS is a numerical score of the severity of the perception of pruritus, and, hence, is inherently subjective. The objective of this study was to assess the reliability of a VAS as an index of pruritus in cholestatic patients. Methods: In 8 patients with chronic pruritus due to primary biliary cholangitis, values for a VAS of pruritus were compared with corresponding measurements of scratching activity, which were generated by a monitoring system specifically designed to quantitate this activity. The relationship between individual values for the VAS and corresponding values for scratching activity during a specific interval immediately preceding the recording of the VAS was examined by determining the Spearman's rank correlation coefficient. Results: The mean Spearman's rank correlation coefficient between individual values for the VAS and corresponding mean values for scratching activity was 0.072; the range of these coefficients was -0.04 to 0.26. A VAS of pruritus is an unreliable index of scratching activity, and, hence, of the pathophysiological process responsible for the pruritus of cholestasis. Conclusions: It is concluded that the use of a VAS as a primary quantitative endpoint in trials of the efficacy of potential therapies for the pruritus of cholestasis may be inappropriate.

Removal of bile acids by extracorporeal therapies: an in vitro study

INTRODUCTION

Bile acids (BAs) accumulating in the circulation in patients with liver failure are considered to be responsible for pruritus, which strongly impairs quality of life of the affected patients. The aim of this study was the in vitro characterization of different BAs regarding their removability with high-flux dialysis as well as with different adsorbents, and the evaluation of their binding to plasma proteins.

METHODS

Dialysis experiments were conducted in pediatric circuits with human plasma. For the adsorption studies, batch tests using 10% adsorbent in spiked human plasma were carried out. The binding of BAs to plasma compounds was determined by centrifugation of spiked plasma through spin columns. Sieving coefficients were determined using an albumin filter and a high-flux dialyzer.

RESULTS

With high-flux dialysis, only hydrophilic BAs such as glycocholic and taurocholic acid could be removed efficiently, while all tested BAs were removed by adsorption.

CONCLUSIONS

In conclusion, the hydrophilicity of BAs plays a major role in their removability using extracorporeal approaches. Adsorption-based systems offer particular advantages for the removal of hydrophobic BAs.

Pharmacological interventions for pruritus in adult palliative care patients

BACKGROUND

This is an update of the original Cochrane review published in 2013 (Issue 6). Pruritus occurs in patients with disparate underlying diseases and is caused by different pathologic mechanisms. In palliative care patients, pruritus is not the most prevalent but is one of the most puzzling symptoms. It can cause considerable discomfort and affects patients' quality of life.

OBJECTIVES

To assess the effects of different pharmacological treatments for preventing or treating pruritus in adult palliative care patients.

SEARCH METHODS

For this update, we searched CENTRAL (the Cochrane Library), and MEDLINE (OVID) up to 9 June 2016 and Embase (OVID) up to 7 June 2016. In addition, we searched trial registries and checked the reference lists of all relevant studies, key textbooks, reviews and websites, and we contacted investigators and specialists in pruritus and palliative care regarding unpublished data.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) assessing the effects of different pharmacological treatments, compared with a placebo, no treatment, or an alternative treatment, for preventing or treating pruritus in palliative care patients.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the identified titles and abstracts, performed data extraction and assessed the risk of bias and methodological quality. We summarised the results descriptively and quantitatively (meta-analyses) according to the different pharmacological interventions and the diseases associated with pruritus. We assessed the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation) and created 10 'Summary of findings' tables.

MAIN RESULTS

In total, we included 50 studies and 1916 participants in the review. We added 10 studies with 627 participants for this update. Altogether, we included 39 different treatments for pruritus in four different patient groups.The overall risk of bias profile was heterogeneous and ranged from high to low risk. However, 48 studies (96%) had a high risk of bias due to low sample size (i.e. fewer than 50 participants per treatment arm). Using GRADE criteria, we downgraded our judgement on the quality of evidence to moderate in seven and to low in three comparisons for our primary outcome (pruritus), mainly due to imprecision and risk of bias.In palliative care participants with pruritus of different nature, the treatment with the drug paroxetine, a selective serotonin reuptake inhibitor, reduced pruritus by 0.78 points (numerical analogue scale from 0 to 10; 95% confidence interval (CI) -1.19 to -0.37; one RCT, N = 48, quality of evidence: moderate) compared to placebo.For participants suffering from uraemic pruritus (UP), gabapentin was more effective than placebo (visual analogue scale (VAS): 0 to 10), mean difference (MD) -5.91, 95% CI -6.87 to -4.96; two RCTs, N = 118, quality of evidence: moderate). The κ-opioid receptor agonist nalfurafine showed amelioration of UP (VAS 0 to 10, MD -0.95, 95% CI -1.32 to -0.58; three RCTs, N = 422, quality of evidence: moderate) and only few adverse events. Moreover, cromolyn sodium relieved UP participants from pruritus by 2.94 points on the VAS (0 to 10) (95% CI -4.04 to -1.83; two RCTs, N = 100, quality of evidence: moderate) compared to placebo.In participants with cholestatic pruritus (CP), data favoured rifampin (VAS: 0 to 100, MD -24.64, 95% CI -31.08 to -18.21; two RCTs, N = 42, quality of evidence: low) and flumecinol (RR > 1 favours treatment group; RR 1.89, 95% CI 1.05 to 3.39; two RCTs, N = 69, quality of evidence: low) and showed a low incidence of adverse events in comparison with placebo. The opioid antagonist naltrexone reduced pruritus for participants with CP (VAS: 0 to 10, MD -2.26, 95% CI -3.19 to -1.33; two RCTs, N = 52, quality of evidence: moderate) compared to placebo. However, effects in participants with UP were inconclusive (percentage difference -12.30%, 95% CI -25.82% to 1.22%, one RCT, N = 32). Furthermore, large doses of opioid antagonists (e.g. naltrexone) could be inappropriate in palliative care patients because of the risk of reducing analgesia.For participants with HIV-associated pruritus, it is uncertain whether drug treatment with hydroxyzine hydrochloride, pentoxifylline, triamcinolone or indomethacin reduces pruritus because the evidence was of very low quality (e.g. small sample size, lack of blinding).

AUTHORS' CONCLUSIONS

Different interventions tended to be effective for CP and UP. However, therapies for patients with malignancies are still lacking. Due to the small sample sizes in most meta-analyses and the heterogeneous methodological quality of the included trials, the results should be interpreted cautiously in terms of generalisability.

Treatment of pruritus with Prometheus dialysis and absorption system in a patient with benign recurrent intrahepatic cholestasis

Benign recurrent intrahepatic cholestasis (BRIC) is an autosomal recessive liver disorder characterized by recurrent episodes of jaundice and itching. Episodes of cholestasis last variously from 1 week to several months, may start at any age and usually resolve spontaneously. No effective treatment has been found as yet. We report a case of genetically proven BRIC in a male patient who developed three episodes of pruritus and jaundice at the age of 14, 16 and 19 years. During the third episode, he did not respond to pharmacological medical therapy, and fractionated plasma separation and absorption (FPSA, Prometheus) was performed to manage intractable pruritus. The treatment immediately alleviated pruritus, lowered serum bilirubin concentration and induced sustained remission in the 5-year follow up. FPSA seems to be a safe and effective way of treatment for BRIC in patients with severe pruritus and prolonged jaundice.

Pharmacological interventions for pruritus in adult palliative care patients

BACKGROUND

Pruritus is not the most prevalent but one of the most puzzling symptoms in palliative care patients. It can cause considerable discomfort and has a major impact on patients' quality of life. In the field of palliative care, pruritus is a symptom occurring in patients with disparate underlying diseases and based on different pathologic mechanisms but ending in the same phenomenon. The pathogenesis of pruritus is complex and not fully elucidated. Thus, it is still very difficult to treat pruritus effectively. Evidence-based treatment approaches are needed.

OBJECTIVES

The objective was to evaluate the efficacy of different pharmacological treatments for preventing or treating pruritus in adult palliative care patients.

SEARCH METHODS

A systematic literature search up to January 2012 was performed and it was updated in August 2012. The following databases were searched: The Cochrane Library (CENTRAL, DARE, CDSR) (2012, issue 8 of 12); MEDLINE (1950 to August 2012); EMBASE (1980 to August 2012) and three other databases. In addition, we searched trials registries and checked the reference lists of all relevant studies, key textbooks, reviews, and websites, and contacted investigators and specialists in pruritus and palliative care regarding unpublished data.

SELECTION CRITERIA

We included randomised controlled trials assessing the effects of different pharmacological treatments on preventing or treating pruritus in palliative care patients.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed identified titles and abstracts. Three independent review authors performed assessment of all potentially relevant studies, data extraction, assessment of risk of bias and methodological quality. Results were summarised descriptively according to the different pharmacological interventions and the type of underlying pruritus. Where possible, results were presented in meta-analyses.

MAIN RESULTS

In total, 38 reports comprising 40 studies and 1286 participants were included in the review. Altogether, 30 different treatments for pruritus in four different patient groups were included.The findings of this review indicated that the treatment of pruritus for palliative care patients is challenging and requires an individualistic approach. Results showed that effective therapeutic choices have to be guided by the pathophysiology of the pruritus. Various forms of pruritus occur, especially in the field of palliative care, and sometimes the origin of the pruritus is difficult to determine. Therefore, identifying the underlying cause of pruritus is of prime importance in order to develop tailored treatment plans, even if in palliative care the treatment is focused towards the symptom and not necessarily the underlying disease.Results show that in palliative care patients with pruritus of different natures, treatment with the drug paroxetine, a selective serotonin reuptake inhibitor, may be beneficial. For patients suffering from pruritus associated with HIV infection, indomethacin was described as the most effective drug, although the evidence was weak. For patients suffering from chronic kidney disease-associated pruritus, gabapentin may be an option. An alternative treatment for this patient group seems to be the κ-opioid receptor agonist nalfurafine, which has shown significant amelioration of pruritus and acceptable adverse effects. As they have exhibited a low incidence of adverse effects, rifampicin and flumecinol may be recommended for patients with cholestatic pruritus. The opioid antagonist naltrexone has been shown to offer a therapeutic alternative for patients suffering from uraemic or cholestatic pruritus. However, these drugs are often inappropriate in the palliative population because of the risk of reducing analgesia when giving high doses of naltrexone.

AUTHORS' CONCLUSIONS

The findings of this review indicate that the number of systemic and topical drugs used for the different subforms of pruritus is increasing. Different interventions have been shown to be effective in the treatment of pruritus of different origins. Nevertheless, an optimal therapy for pruritus is constrained due to the limited understanding of crucial itch mediators and receptors in the various subforms of itch. Ideal antipruritic therapies are still lacking, especially for palliative care patients.This systematic review also indicates that there is insufficient evidence to give any concrete recommendations regarding treatment of pruritus in palliative care patients. Due to the very small sample sizes and poor methodological quality of the majority of studies that were included, the results of this review need to be interpreted with caution. Furthermore, the generalizability is questionable. Additional studies, and particularly carefully designed treatment trials, are needed to provide valid evidence for adequate treatment of pruritus in palliative care patients.

Effects of fractionated plasma separation and adsorption on survival in patients with acute-on-chronic liver failure

BACKGROUND & AIMS

Fractionated plasma separation and adsorption (FPSA) is an extracorporeal procedure that supports liver function by removing endogenous toxins that cause complications from acute-on-chronic liver failure (AOCLF). We performed a randomized trial to investigate survival of patients with AOCLF treated with FPSA.

METHODS

Patients with AOCLF were randomly assigned to groups given a combination of FPSA and standard medical therapy (SMT) (FPSA group, n = 77) or only SMT (SMT group, n = 68). The Prometheus liver support system was used to provide 8 to 11 rounds of FPSA (minimum of 4 hours each) for 3 weeks. Primary end points were survival probabilities at days 28 and 90, irrespective of liver transplantation.

RESULTS

Baseline clinical parameters and number of transplant patients were similar between study arms. Serum bilirubin level decreased significantly in the FPSA group but not in the SMT group. In an intention-to-treat analysis, the probabilities of survival on day 28 were 66% in the FPSA group and 63% in the SMT group (P = .70); on day 90, they were 47% and 38%, respectively (P = .35). Baseline factors independently associated with poor prognosis were high SOFA score, bleeding, female sex, spontaneous bacterial peritonitis, intermediate increases in serum creatinine concentration, and combination of alcoholic and viral etiology of liver disease. There were no differences between the 2 groups in the incidence of side effects.

CONCLUSIONS

Among all patients with AOCLF, extracorporeal liver support with FPSA does not increase the probability of survival. Further studies are needed to assess whether therapy might be beneficial in specific subsets of patients.

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.

Extracorporeal artificial liver support systems in the management of intractable cholestatic pruritus

Pruritus can occur as a severe complication of cholestasis. Several hypotheses suggest an important role for the accumulation of bile acids, endogenous opioids and - mire recently - lysophosphatidic acid. Bile acid sequestrants are the first-line therapeutic agents. In refractory cases, a stepwise approach using rifampicin, oral opiate antagonists and the selective serotonin reuptake inhibitor sertraline should be tested. Recent case series reported effective relief of pruritus using extracorporal liver support systems and plasmapheresis.

Fractionated plasma separation and adsorption: current practice and future options

Fractionated plasma separation and adsorption (FPSA) is a method of albumin dialysis that is integrated into an extracorporeal liver support device (Prometheus(®)). This concept allows the effective removal of both protein-bound and water-soluble substances without the need for external albumin. Several studies comparing the in vivo extraction capacities of FPSA and molecular adsorbent recirculating system (MARS) concluded that detoxification by FPSA seems to be more effective than by MARS. Overall, FPSA therapy has been shown to be safe. Over the last few years, the anticoagulation protocol for FPSA therapy was optimised by using regional anticoagulation with citrate to avoid clotting of system components. Recently, the results of a large randomised-controlled multicentre trial (HELIOS) have been presented. Survival after 1 and 3 months was evaluated in 145 patients with acute-on-chronic liver failure comparing FPSA therapy with standard medical treatment versus standard medical treatment alone. There was no statistically significant survival benefit for patients undergoing FPSA therapy. However, patients with hepatorenal syndrome type I or MELD score >30 showed a significant survival benefit under FPSA in a predefined subgroup analysis. Furthermore, there have been promising results with FPSA in the treatment of refractory cholestatic pruritus. Regarding acute liver failure, only few data are currently available.

Treatment of resistant pruritus from cholestasis with albumin dialysis: combined analysis of patients from three centers

BACKGROUND & AIMS

Albumin dialysis using molecular adsorbent recirculating system (MARS) is a new procedure for treating resistant pruritus from cholestasis, but it is usually published as a case report or a short series. Therefore, we analyzed patients with resistant pruritus treated with MARS from three centers, to assess the changes on pruritus and the indices of cholestasis.

METHODS

Twenty patients (12 female, mean age: 51+/-3.4 years) with chronic cholestatic liver disease or chronic liver-graft rejection were evaluated. The severity of pruritus was assessed using a visual analogue scale (VAS) before and after treatment, and 30 days thereafter. Liver tests, including total bilirubin, alkaline phosphatase, gamma-glutamyl-transferase, cholesterol, triglycerides, and total bile acid were also determined, as well as the number of sessions and the coupled procedure (dialysis or perfusion).

RESULTS

Albumin dialysis resulted in a decrease of pruritus (VAS: from 70.2+/-4.8 to 20.1+/-4.2, p<0.001), which partially resumed after 30 days (38.7+/-6.6). VAS decreased by 72% immediately after treatment and by 51% after 1 month. Pruritus decreased in all but one patient. MARS resulted in a significant bile acid decrease of 41% after treatment and by 37% after 1 month. The effect of MARS on pruritus and markers of cholestasis was similar in patients with different diseases and was independent of the coupled procedure. The improvement of pruritus in individuals was positive in 75% of patients. No major adverse effects were observed.

CONCLUSIONS

Albumin dialysis using MARS is an effective procedure for managing resistant pruritus in most patients with chronic cholestasis and graft rejection.

Extracorporeal liver support therapy with Prometheus in patients with liver failure in the intensive care unit

Acute liver failure (ALF) and acute-on-chronic liver failure (AoCLF) are associated with a high mortality. In these patients an accumulation of both water-soluble and water-insoluble, protein-bound, metabolic waste products occurs. Conventional extracorporeal blood purification techniques based on diffusion and/or convection such as hemodialysis or hemofiltration may only eliminate small molecular weight, water-soluble compounds. In recent years, fractionated plasma separation and adsorption (FPSA) with the Prometheus system has been introduced for extracorporeal liver support therapy. To date, however, only limited data is available regarding the effect of this treatment on mortality and outcome of patients with advanced liver disease. Here we report on our experience with 23 patients with severe liver failure who were treated with Prometheus in our medical intensive care unit. Fourteen patients had AoCLF, and nine patients experienced ALF. The median bilirubin level at the start of Prometheus therapy was 30.5 mg/dL and the median Acute Physiology and Chronic Health Evaluation II (APACHE II) score was 26. During 40 individual treatment sessions lasting 5-6 h, Prometheus therapy reduced serum bilirubin levels from 23.7 mg/dL to 15.0 mg/dL (median values) (P < 0.001), and the overall survival was 26%. ALF patients had a better survival compared to AoCLF patients (44% vs. 22%; P = 0.022). Apart from one patient who developed hemodynamic instability during a treatment session, Prometheus therapy was well tolerated without relevant side-effects. In conclusion, extracorporeal liver support therapy with Prometheus is a novel and safe treatment option in patients with severe liver failure. In this series, patients with ALF showed a significantly better outcome with Prometheus therapy compared to AoCLF 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.

Pruritus in primary biliary cirrhosis: pathogenesis and therapy

Pruritus is a symptom experienced by patients who have primary biliary cirrhosis. It seems to result from pruritogens that (as a result of cholestasis) accumulate in plasma and other tissues, and which lead to altered neurotrasnmission. Administration of medications that change opioid neurotransmission (ie, opiate antagonists) results in relief of pruritus and its behavioral manifestation, scratching. Through unknown mechanisms, other centrally acting medications, including antidepressants, may have ameliorating effects on the pruritus of cholestasis. Stimulating endogenous detoxification pathways in the liver may also lead to the amelioration of pruritus. The removal of pruritogens through administration of nonabsorbable resins, nasobiliary drainage, biliary diversion, plasmapheresis, and various dialysis procedures is reported to decrease pruritus in liver disease, although the substances that are presumably removed are unknown.

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.

Update on the treatment of the pruritus of cholestasis

The pruritus of cholestasis is a difficult clinical problem to manage. It can be severe and interfere with sleep. Clinical behavioral studies have confirmed that the pruritus is mediated at least in part by endogenous opioids. Other neurotransmitter systems may be involved in the mediation of pruritus. Work continues to identify the mechanisms that mediate the pruritus and to develop specific drugs to treat this often maddening symptom.

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.