Push-pull sorbent-based pheresis and hemodiabsorption in the treatment of hepatic failure: preliminary results of a clinical trial with the BioLogic-DTPF System

Survival Benefits With Artificial Liver Support System for Acute-on-Chronic Liver Failure: A Time Series-Based Meta-Analysis

The artificial liver support system (ALSS) offers the potential to improve the prognosis of patients with acute-on-chronic liver failure (ACLF). However, the literature has been inconsistent on its survival benefits. We aimed to conduct a time series-based meta-analysis of randomized clinical trials (RCTs) and observational studies which examined differences in mortality in ACLF patients treated with ALSS or not.MEDLINE, EMBASE, OVID, and COCHRANE library database were systemically searched up to December 2014. Quality of included studies was evaluated using the Jadad score. The outcome measure was mortality at different follow-up endpoints. Odds ratios (ORs) and survival curve data were pooled for analysis.Ten studies, 7 RCTs, and 3 controlled cohorts were enrolled, involving a total of 1682 ACLF patients, among whom 842 were treated with ALSS. ALSS was found to reduce the risk of short-term (1-month and 3-month) mortality for patients with ACLF by nearly 30%. Randomized trials and observational studies provided good internal and external validity respectively. The combined Kaplan-Meier curves showed a consistent pattern of findings. Meta-analysis also suggested that ALSS might reduce medium-term (6-month and 1-year) mortality risk by 30% and long-term (3-year) mortality risk by 50% in ACLF patients.ALSS therapy could reduce short-term mortality in patients with ACLF. Meanwhile, its impacts on medium- and long-term survival seem to be promising but remained inconclusive. Clinical utility of this system for survival benefit may be implied.

No sustained impact of intermittent extracorporeal liver support on thrombocyte time course in a randomized controlled albumin dialysis trial

Reduction of platelets is a common finding in patients with liver disease and can be aggravated by extracorporeal therapies, e.g. artificial liver support. The impact of extracorporeal albumin dialysis on the time count and time course of platelets in liver failure patients was evaluated in a randomized controlled clinical trial. Mean thrombocyte reduction during a single extracorporeal liver support therapy was -15.1% [95%CI: -17.7; -12.5]. No differences were found between treatments of patients with a more reduced platelet count (<100 GPT/L: -15.6% [-19.5; -11.7%]; n = 43) compared to patients with normal or slightly decreased thrombocytes (-14.6% [-18.3%; -11.0%]; n = 43; P = 0.719). The variation of platelet count within 24 h after onset of extracorporeal therapy treatment was less, albeit significant (-3.5% [-6.3%; -0.7%], P < 0.016). Absolute thrombocyte variability was comparable between both groups (with extracorporeal therapy -5.6 GPT/L [-9.7; -1.4], without extracorporeal therapy -1.3 GPT/L [-7.3; 4.7]; P = 0.243), whereas relative decrease of thrombocytes within a 24-h period of extracorporeal therapy was greater than the changes in patients without extracorporeal therapy (-3.5% [-6.3%; -0.7%] vs. 2.0% [-2.0%; 5.9%]; P = 0.026]. Within a period of two weeks after enrollment, no significant differences of platelet count were observed either between the two groups or in the time course (P(group) = 0.337, P(time) = 0.277). Reduction of platelets during intermittent extracorporeal liver support was less pronounced within a 24-h period as before and after a single treatment and was comparable to variations in the control group without extracorporeal therapy.

Liver support strategies: cutting-edge technologies

The treatment of end-stage liver disease and acute liver failure remains a clinically relevant issue. Although orthotopic liver transplantation is a well-established procedure, whole-organ transplantation is invasive and increasingly limited by the unavailability of suitable donor organs. Artificial and bioartificial liver support systems have been developed to provide an alternative to whole organ transplantation, but despite three decades of scientific efforts, the results are still not convincing with respect to clinical outcome. In this Review, conceptual limitations of clinically available liver support therapy systems are discussed. Furthermore, alternative concepts, such as hepatocyte transplantation, and cutting-edge developments in the field of liver support strategies, including the repopulation of decellularized organs and the biofabrication of entirely new organs by printing techniques or induced organogenesis are analysed with respect to clinical relevance. Whereas hepatocyte transplantation shows promising clinical results, at least for the temporary treatment of inborn metabolic diseases, so far data regarding implantation of engineered hepatic tissue have only emerged from preclinical experiments. However, the evolving techniques presented here raise hope for bioengineered liver support therapies in the future.

Development of a multifunctional detoxifying unit for liver failure patients

BACKGROUND/AIMS

Extracorporeal blood detoxification strategies aimed at supporting impaired liver function have been explored because of the imbalance between donor organs and waiting patients. A limited number of artificial devices are now available clinically, and these are characterized by the use of multistage adsorption procedures in conjunction with hemodialysis, but these features simultaneously increase system complexity and treatment costs.

METHODS

The authors developed a simpler strategy for liver dialysis based on the use of a multifunctional filter, which enables plasma separation and perfusion in a single unit.

RESULTS

Liver dialysis treatments were successfully performed using the devised unit when bovine blood containing uremic and hepatic toxins was circulated. Removal of the solutes under investigation was significant, and reduction ratios of 78% for urea, 98% for creatinine and 91% for bilirubin were achieved. Plasma free hemoglobin levels were reasonably maintained despite prolonged blood recirculation for 5 h, and platelet, hematocrit and hemoglobin levels remained uniform throughout liver dialysis sessions.

CONCLUSION

The devised liver support unit may offer a straightforward and efficient means of cleansing blood for patients with hepatic failure.

[Acute on chronic liver failure]

Acute-on-Chronic Liver Failure (ACLF) is a recently introduced term defined as severe acute deterioration of an established liver disease. This entity usually develops after an acute insult. The main clinical manifestations are hepatorenal syndrome, hepatic encephalopathy and organ failure, with a high risk of death in the short term. The true incidence of ACLF remains difficult to determine due to confusions surrounding the definition of this entity, but seems to be 40% at 5 years in patients with advanced cirrhosis, which translates into 4,000 cases in Europe within this time span. The treatment of choice is liver transplantation. However, due to the shortage of suitable organs and morbidity and mortality in these patients, other options must be used.

Role of artificial liver support in hepatic encephalopathy

Hepatic encephalopathy (HE) refers to the reversible neuropsychiatric disorders observed in acute liver failure and as a complication of cirrhosis and/or portal hypertension. This review aims to describe the pathophysiology of HE, the rationale for the use of artificial liver support in the treatment of HE, the different concepts of artificial liver support and the results obtained. Ammonia has been considered central to its pathogenesis but recently an important role for its interaction with inflammatory responses and auto-regulation of cerebral hemodynamics has been suggested. Artificial liver support might be able to decrease ammonia and modulate inflammatory mediators and cerebral hemodynamics. Bioartificial liver support systems use hepatocytes in an extracorporeal device connected to the patient's circulation. Artificial liver support is intended to remove protein-bound toxins and water-soluble toxins without providing synthetic function. Both systems improve clinical and biochemical parameters and can be applied safely to patients. Clinical studies have shown that artificial liver support, especially albumin dialysis, is able to improve HE in acute and acute-on-chronic liver failure. Further studies are required to better understand the mechanism, however, artificial liver support can be added to the therapeutic bundle in treating HE.

New methods for hemoglobin detection in a microparticle-plasma suspension

In the extracorporeal adsorption system, MDS (Microspheres based Detoxification System), micro-adsorbent particles measuring 1-25 micrometers circulate in a filtrate circuit for highly specific blood purification/adsorption. The MDS circuit containing the adsorbent microparticles is linked to the patient's blood line by a hollow fiber plasma filter. When the transmembrane pressure or the shear forces due to the red blood cells in the hollow fiber filter are too high, they can be damaged and hemoglobin will be released. In order to detect free hemoglobin (fHb) by optical means, we have designed a new flow-dynamic filter system, placed in the microadsorbent circuit for continuous separation of microparticles from the filtrate. In the flow dynamic filter, we use a high velocity liquid vortex to remove sedimentation and particle plugs on the filter membrane. In our investigations, 3 and 8 micron cellulose nitrate filter membranes for particle separation are used. The obtained particle free bypass filtrate flow rates are typically 0.5 and 0.8 ml/min respectively. The typical sensitivity for fHb detection by the applied noninvasive optical method is 0.15 g/dL. Medical safety regulations require a fail-safe mechanism for fHb detection which monitors the bypass filtrate flow in the flowdynamic filter and shuts down the system in case of membrane occlusion. The bypass filtrate flow is monitored by periodically occluding and releasing the bypass line by means of a clamp. The resulting back pressure profile gives information about the actual filtration rate. This safety principle was proven by statistical analysis and shows its clear functionality.

Formal heparin anticoagulation protocol improves safety of charcoal-based liver-assist treatments

Extracorporeal devices have had limited effectiveness in liver failure due to consequences of inadequate anticoagulation. The purpose of this study was to evaluate an anticoagulation protocol developed for Liver Dialysis Unit (LDU) treatments. Twelve patients underwent 19 LDU treatments for acetaminophen overdose (n = 1), subacute liver failure (n = 1), and refractory encephalopathy in cirrhosis (n = 10). The initial 6 patients (group 1) were treated according to the manufacturer's recommendations. The subsequent 6 patients (group 2) were treated using a formal heparin anticoagulation protocol that included 2000 units in prime solution and 30 units/kg induction, activated clotting time (ACT) measurements, and heparin administered by dose-response curve to maintain 300-second ACT. Protamine reversal was used. Treatments were well tolerated and equally effective in both groups. Adequate (ACT > or = 250 seconds) and therapeutic (ACT 250-350 seconds) anticoagulation was maintained more consistently in group 2 (90.9% vs 50.0%, p < 0.0001; and 77.4% vs 45.8%, p < 0.001). There was less consumption of fibrinogen (12.1% vs 43.3%, p < 0.005) and platelets (13.8% vs 29.9%, p < 0.05) and a trend for less blood product used (8.3 vs 15.8 units/patient, p = 0.13) and fewer complications (16.7% vs 66.7%, p = 0.15) in group 2. Anticoagulation using ACT monitoring, heparin dose-response curves, and a target ACT of 300 seconds improves the safety of LDU treatments.

Slow continuous ultrafiltration with bound solute dialysis

Bound solute dialysis (BSD), often referred to as "albumin dialysis" (practiced clinically as the molecular adsorbents recirculating system, MARS, or single-pass albumin dialysis, SPAD) or "sorbent dialysis" (practiced clinically as the charcoal-based Biologic-DT), is based upon the thermodynamic principle that the driving force for solute mass transfer across a dialysis membrane is the difference in free solute concentration across the membrane. The clinically relevant practice of slow continuous ultrafiltration (SCUF) for maintenance of patients with liver failure is analyzed in conjunction with BSD. The primary dimensionless operating parameters that describe SCUF-BSD include (1) beta, the dialysate/blood binder concentration ratio; (2) kappa, the dialyzer mass transfer/blood flow rate ratio; (3) alpha, the dialysate/blood flow rate ratio; and, (4) gamma, the ultrafiltration/blood flow rate ratio. Results from mathematical modeling of solute removal during a single pass through a dialyzer and solute removal from a one-compartment model indicate that solute removal is remarkably insensitive to gamma. Solute removal approaches an asymptote (improvement in theoretical clearance over that obtainable with no binder in the dialysate) with increasing beta that is dependent on kappa and independent of alpha. The amount of binder required to approach the asymptote decreases with increasing solute-binder equilibrium constant, i.e., more strongly bound solutes require less binder in the dialysate. The results of experimental observations over a range of blood flow rates, 100 to 180 mL/min, dialysate flow rates, 600 to 2150 mL/h, ultrafiltration rates, 0 to 220 mL/h, and dialysate/blood albumin concentration ratios, beta = 0.01 to 0.04, were independently predicted remarkably well by the one-compartment model (with no adjustable parameters) based on BSD principles.

Sorbent Suspensions vs. Sorbent Columns for Extracorporeal Detoxification in Hepatic Failure

Hepatic failure is a significant medical problem which has been unsuccessfully treated by hemodialysis. However, similar therapies using recirculated dialysate regenerated by sorbents in place of single-pass dialysate have been beneficial in treating acute-on-chronic liver failure. The advantages of sorbent-based treatments include some selectivity of toxin removal and improved removal of protein-bound toxins. Activated carbon has been extensively used in detoxification systems, but has often had insufficient toxin capacity. Powdered activated carbon, because of its large surface area, can provide greater binding capacity for bilirubin and other toxins than granular carbon commonly used in detoxifying columns. Methods of using powdered carbon in extracorporeal blood treatment devices are reviewed in the present paper, including liver dialysis and a new sorbent suspension reactor (SSR); and the abilities and limitations of the SSR and columns to process protein solutions are discussed.

Particle Leakage in Extracorporeal Blood Purification Systems Based on Microparticle Suspensions

AIM

The newly developed 'Microspheres based Detoxification System' (MDS) designed for any extracorporeal adsorption therapy uses microparticles as adsorbents characterized by a size of 1-20 microm in diameter which are recirculated in the secondary (filtrate) circuit connected to a hollow fiber filter located in the primary (blood) circuit. In the case of a leakage or rupture in the hollow fiber filter, microspheres can enter patients' blood circuits and cause embolic episodes in different organs with varying degrees of clinical relevance. Aim of this study was to determine the amount of particles infused to a patient during a long-term treatment under different failure conditions of the filter.

METHODS

The filters were prepared by cutting single hollow fibers. Fresh-frozen plasma (FFP) and a mixture of glycerol and water were used as a medium together with microparticles potentially used in the MDS. The amounts of particles transferred from the filtrate into the primary circuit were measured.

RESULTS

The analysis of particle transfer in the case of a single cut hollow fiber inside the membrane results in particle volumes of up to 26 ml calculated for 10 h.

CONCLUSION

Particle leakage in microparticle suspension based detoxification systems can lead to considerable particle transfer to the patient. Therefore, a particle detection unit which is able to detect critical amounts of particles (<1 ml particle volume/treatment) in the extracorporeal blood line is necessary for patient safety.

Detection of Fluorescently Labeled Microparticles in Blood

BACKGROUND

A microsphere-based detoxification system is an adsorption system, whereby microadsorbent particles having diameters of 1-20 microm circulate in an extracorporeal filtrate circle. A thin-wall hollow-fiber membrane filter separates the microparticle-plasma suspension from the bloodstream. For patient safety, it is necessary to have a means to detect membrane ruptures that could lead to a release of microparticles into the patient's bloodstream.

METHODS

An optical detection system was developed to monitor the venous bloodstream for the presence of microparticles from the filtrate circuit. For detection purposes, cellulose microspheres, both ferromagnetic and fluorescence labeled, were included with the microsphere adsorbant particles. In the case of a membrane rupture, the labeled particles would also be released into the bloodstream. By illuminating a small volume of blood with an excitation wavelength (590 nm) of the fluorescence marker, the particles can be detected by their emission light at 620 nm. The detector sensitivity is increased by collecting the ferromagnetic and fluorescently labeled microparticles using a magnetic trap. The efficiency of magnetic trap arrangements was tested by adjusting the magnet placements.

RESULTS

In vitro experiments were performed by pumping whole blood and labeled microparticles through the fluorescence detector. The efficiency of a magnetic trap arrangement was determined. With an optimal trap setup, 5-10 microl of labeled microparticles can be clearly detected in streaming whole blood.

CONCLUSION

An easy to handle microparticle detector was developed, ready for use in particle based blood detoxification systems. The microparticle detection system fulfills the medical and technical requirements to bring the MDS into clinical tests.

Bridges to transplantation

The definitive treatment of patients with acute liver failure is liver transplantation. Organ Procurement and Transplantation Network status 1 patients receive priority, but the median waiting time in 2002 was 11 days. Patients who are small or have an unusual blood type are expected to wait even longer. Because cerebral edema and death may occur before a liver is available, numerous methods of bridging patients to transplantation by artificial means have been proposed. To date, no system of hepatic support has been proven effective at delaying the onset of cerebral edema in controlled trials.

Hepatic tissue engineering for adjunct and temporary liver support: critical technologies

The severe donor liver shortage, high cost, and complexity of orthotopic liver transplantation have prompted the search for alternative treatment strategies for end-stage liver disease, which would require less donor material, be cheaper, and less invasive. Hepatic tissue engineering encompasses several approaches to develop adjunct internal liver support methods, such as hepatocyte transplantation and implantable hepatocyte-based devices, as well as temporary extracorporeal liver support techniques, such as bioartificial liver assist devices. Many tissue engineered liver support systems have passed the "proof of principle" test in preclinical and clinical studies; however, they have not yet been found sufficiently reliably effective for routine clinical use. In this review we describe, from an engineering perspective, the progress and remaining challenges that must be resolved in order to develop the next generation of implantable and extracorporeal devices for adjunct or temporary liver assist.

Extracorporeal liver support: waiting for the deciding vote

Because acute liver cell failure is associated with an exceedingly high mortality, liver support has been proposed since the 1950s to improve patient outcome. Early devices, including hemodialysis, hemofiltration, exchange transfusion, plasmapheresis, hemoperfusion, plasma and cross-hemodialysis or cross-circulation, appeared inefficient. Meanwhile, documented results of extracorporeal liver perfusion (ECLP) suggested its superiority over conventional treatment. These devices were abandoned with the development of liver transplantation (LT), which allowed a better outcome and longer survival rate. In the present day, the fact that patients die while waiting for LT because of organ shortage led to a renewed interest in liver support as bridge to LT or regeneration. These devices can be classified according to the presence or lack of hepatocytes, whereas biologic devices refers to the presence of cells or other organic and biochemical component. The absence of individual success of early models led to the development of combined hepatocyte free devices, or artificial liver, which are based upon the hemodiabsorption principle (Biologic-DT) or on the "albumin bound toxin hypothesis" (Molecular Adsorbents Recirculating System) with encouraging results. Meanwhile, hepatocyte based bioartificial liver devices (BLD) were conceived for a global "metabolic support." BLD were developed with the use of human hepatoma cell line (C3A) or primary or cryopreserved porcine hepatocytes. Preliminary experience gave promising results bridging patients to LT. Based upon the same principle of global hepatocyte metabolic support, ECLP regained interest, particularly with the development of transgenic pigs. Several concerns were raised about these devices. Artificial livers lacked any metabolic synthetic activity, the use of human liver for ECLP seems hardly acceptable because of organ shortage, and the accepted use of borderline livers for transplantation is pending trials for the use of xenogenic livers. For BLD, the concerns were the low hepatocyte mass, the absence of accessory liver cells, and the potential risk of seeding tumor cells into patient with the use of human hepatoma cell line. The use of porcine hepatocytes (BLD or ECLP) raised physiologic and immunologic concerns and particularly the fear of a possible transfer of porcine viral material. Although recent studies clearly demonstrate clinical improvement of patients with the use of recently developed liver support devices, most of reported prospective, controlled, or randomized trials had a small number of patients. To give the deciding vote and avoid previous pitfalls, trials need to be developed with a larger number of patients based upon statistically significant models with the following characteristics: 1) comprehensive understanding of the acute liver cell failure mechanisms, 2) world wide classification of conditions that require liver support, and 3) a clear definition of treatment success pending patients to LT or recovery without transplantation. There has not yet been conclusive evidence to support the benefits of extracorporeal liver support. We are still waiting for the deciding vote.

Artificial and bioartificial support systems for liver failure

BACKGROUND

Artificial and bioartificial liver support systems may 'bridge' patients with acute or acute-on-chronic liver failure to liver transplantation or recovery.

OBJECTIVES

To evaluate beneficial and harmful effects of artificial and bioartificial support systems for acute and acute-on-chronic liver failure.

SEARCH STRATEGY

Trials were identified through The Cochrane Hepato-Biliary Group Controlled Trials Register (September 2002), The Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 3, 2002), MEDLINE (1966 - September 2002), EMBASE (1985 - September 2002), and The Chinese Biomedical Database (September 2002), manual searches of bibliographies and journals, authors of trials, and pharmaceutical companies.

SELECTION CRITERIA

Randomised clinical trials on artificial or bioartificial support systems for acute or acute on-chronic liver failure were included irrespective of blinding, publication status, or language. Non-randomised studies were included in explorative analyses.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by three reviewers. Results were presented as relative risks (RR) with 95% confidence intervals (CI). Sources of heterogeneity were explored through sensitivity analyses and meta-regression. The primary outcome was mortality.

MAIN RESULTS

Twelve trials on artificial or bioartificial support systems versus standard medical therapy (483 patients) and two trials comparing different artificial support systems (105 patients) were included. Most trials had unclear methodological quality. Compared to standard medical therapy, support systems had no significant effect on mortality (RR 0.86; 95% CI 0.65-1.12) or bridging to liver transplantation (RR 0.87; 95% CI 0.73-1.05), but a significant beneficial effect on hepatic encephalopathy (RR 0.67; 95% CI 0.52-0.86). Meta-regression indicated that the effect of support systems depended on the type of liver failure (P = 0.03). In subgroup analyses, artificial support systems appeared to reduce mortality by 33% in acute-on-chronic liver failure (RR 0.67; 95% CI 0.51-0.90), but not in acute liver failure (RR 0.95; 95% CI 0.71-1.29). Two trials comparing artificial support systems showed significant mortality reductions with intermittent versus continuous haemofiltration (RR 0.58; 95% CI 0.36-0.94) and no significant difference between five versus ten hours of charcoal haemoperfusion (RR 1.03; 95% CI 0.65-1.62). The incidence of adverse events was inconsistently reported.

REVIEWER'S CONCLUSIONS

This Review indicates that artificial support systems may reduce mortality in acute-on-chronic liver failure. Artificial and bioartificial support systems did not appear to affect mortality in acute liver failure. However, considering the strength of the evidence additional randomised clinical trials are needed before any support system can be recommended for routine use.

Artificial and bioartificial support systems for liver failure

BACKGROUND

Artificial and bioartificial liver support systems may 'bridge' patients with acute or acute-on-chronic liver failure to liver transplantation or recovery.

OBJECTIVES

To evaluate beneficial and harmful effects of artificial and bioartificial support systems for acute and acute-on-chronic liver failure.

SEARCH STRATEGY

Trials were identified through The Cochrane Hepato-Biliary Group Controlled Trials Register (September 2002), The Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 3, 2002), MEDLINE (1966 - September 2002), EMBASE (1985 - September 2002), and The Chinese Biomedical Database (September 2002), manual searches of bibliographies and journals, authors of trials, and pharmaceutical companies.

SELECTION CRITERIA

Randomised clinical trials on artificial or bioartificial support systems for acute or acute on-chronic liver failure were included irrespective of blinding, publication status, or language. Non-randomised studies were included in explorative analyses.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by three reviewers. Results were presented as relative risks (RR) with 95% confidence intervals (CI). Sources of heterogeneity were explored through sensitivity analyses and meta-regression. The primary outcome was mortality.

MAIN RESULTS

Twelve trials on artificial or bioartificial support systems versus standard medical therapy (483 patients) and two trials comparing different artificial support systems (105 patients) were included. Most trials had unclear methodological quality. Compared to standard medical therapy, support systems had no significant effect on mortality (RR 0.86; 95% CI 0.65-1.12) or bridging to liver transplantation (RR 0.87; 95% CI 0.73-1.05), but a significant beneficial effect on hepatic encephalopathy (RR 0.67; 95% CI 0.52-0.86). Meta-regression indicated that the effect of support systems depended on the type of liver failure (P = 0.03). In subgroup analyses, artificial support systems appeared to reduce mortality by 33% in acute-on-chronic liver failure (RR 0.67; 95% CI 0.51-0.90), but not in acute liver failure (RR 0.95; 95% CI 0.71-1.29). Two trials comparing artificial support systems showed significant mortality reductions with intermittent versus continuous haemofiltration (RR 0.58; 95% CI 0.36-0.94) and no significant difference between five versus ten hours of charcoal haemoperfusion (RR 1.03; 95% CI 0.65-1.62). The incidence of adverse events was inconsistently reported.

REVIEWER'S CONCLUSIONS

This Review indicates that artificial support systems may reduce mortality in acute-on-chronic liver failure. Artificial and bioartificial support systems did not appear to affect mortality in acute liver failure. However, considering the strength of the evidence additional randomised clinical trials are needed before any support system can be recommended for routine use.

Charcoal-based hemodiabsorption liver support for episodic type C hepatic encephalopathy

OBJECTIVES

Episodic (acute) type C hepatic encephalopathy (AHE) fails to respond to 5 days of medical therapy in 10-30% of patients and carries a 10-30% mortality rate. We prospectively studied extracorporeal liver support for AHE failing to respond to medical therapy to assess its safety and efficacy and the role of anticoagulation.

METHODS

A series of patients with cirrhosis and AHE failing to respond to at least 24 h of medical therapy underwent a maximum of three 6-h charcoal-based hemodiabsorption (Liver Dialysis Unit) treatments. A standard anticoagulation protocol, with heparin dosing based on activated clotting time (ACT) determinations, heparin dose-response curve, and target ACT of 275-300 s, was developed. Therapy was terminated if patients met a predetermined clinical response, deteriorated, or underwent transplantation.

RESULTS

Eighteen patients with grade 2-4 AHE despite 5.9 +/- 3.9 days of medical therapy underwent a mean of 1.6 treatments. In 2.6 +/- 1.9 days, 16 patients (88.9%) improved to less than grade 2 HE or achieved at least a 50% hepatic encephalopathy index (HEI) reduction. Median mental status (grade 2 vs 1, p < 0.05) and HEI (0.634 +/- 0.194 vs 0.363 +/- 0.263, p < 0.005) improved significantly. Survival was 94.4% and 72.2% at 5 and 30 days, respectively. Use of our developed anticoagulation protocol resulted in less platelet (14.2% +/- 2.8% vs 32.5% +/- 5.8%, p < 0.005) and fibrinogen consumption (12.1% +/- 3.5% vs 43.3% +/- 8.6%, p < 0.0005) and blood product use (6.2 +/- 1.8 vs 19.0 +/- 5.6 units, p < 0.05) compared with treatments according to manufacturer's guidelines.

CONCLUSIONS

Charcoal-based hemodiabsorption treatments in which a standardized anticoagulation protocol is used is safe and effective treatment for AHE not responding to standard medical therapy.

Bound solute dialysis

We used the thermodynamic principles governing bound solute dialysis, commonly referred to as "albumin dialysis" or "sorbent dialysis" and practiced clinically with the Molecular Adsorbent Recirculating System (MARS) and Biologic-DT approaches, respectively, to develop a comprehensive understanding of the process. Dimensionless parameters emerging from the thermodynamic analysis that govern bound solute dialysis are as follows: (1) lambda, the binding power of the solute binding moiety; (2) kappa, the dialyzer mass transfer/blood flow rate ratio; (3) alpha, the dialysate/blood flow rate ratio; (4) beta, the dialysate/blood binding moiety concentration ratio, and (5) psi, the solute/binding moiety concentration ratio in the blood. Results from a mathematical model of countercurrent bound solute dialysis for phi = 0.9 indicate that for a given binding moiety (fixed lambda), the most important parameter for achieving high removal rates is the dialyzer mass transfer ratio for free (unbound) solute. The results also show solute removal approaching an asymptote with increasing beta that is dependent on kappa and independent of alpha. More importantly, results indicate that once a dialysis membrane is chosen, solute removal is virtually independent of blood flow rate, dialysate flow rate, and amount of binding moiety in the dialysate, provided the amount is greater than approximately 90% of that required to reach the asymptote. Experimental observations over a range of blood flow rates (100-400 ml/ minute), dialysate flow rates (50-400 ml/minute), and dialysate/blood albumin concentration ratios (beta = 0-0.3) corroborate the model predictions and indicate that < 4 g/L albumin in the dialysate solution is required for effective bound solute dialysis. The experimental results also show evidence of enhanced mass transfer once the dialysis membrane pore structure surface saturates with albumin.

Improvement in central nervous system functions during treatment of liver failure with albumin dialysis MARS--a review of clinical, biochemical, and electrophysiological data

The Molecular Adsorbent Recirculating System (MARS) is a nonbiological liver support method based on the principles of dialysis, filtration, and adsorption. It allows the safe and efficient removal of both albumin-bound and water-soluble toxic metabolites, including ammonia, aromatic amino acids, tryptophan, and related phenolic and indolic products, as well as benzodiazepines. A well-documented effect of the treatment is the improvement of the hemodynamic situation of decompensated chronic patients. Systemic vascular resistance, mean arterial pressure, cerebral blood flow, and cerebral oxygen consumption increased significantly. The degree of hepatic encephalopathy decreased significantly. Increased intracranial pressure could be normalized in both chronic and fulminant liver failure. In three randomized clinical trials significant improvement of survival could be demonstrated. In a model of murine neuronal networks cultured on multi-microelectrode array plates and incubated with plasma from liver failure patients, a normalization of the spike and burst pattern could be observed, if plasma samples from MARS-treated patients before and after treatment were compared. In conclusion, MARS significantly improves central nervous system functions. It can serve as a model for the further investigation of the role of protein-bound substances in hepatic encephalopathy and cerebral hemodynamics.

Review of methods to remove protein-bound substances in liver failure

A wide range of toxic substances accumulates in the circulation of patients with liver failure, including more lipid-soluble substances, which bind to plasma proteins. Serum albumin is the most important binding protein for ligands such as bilirubin and bile acids, which are potentially toxic and can cause apoptosis in astrocytes and hepatocytes respectively in vitro. Resin haemoperfusion was originally investigated to remove these compounds, as well as inflammatory cytokines. Current effective methods for removal of protein-bound compounds in patients with liver failure include high volume plasmapheresis and different forms of albumin dialysis. Bioartificial liver support systems need adsorbent and/or dialysis modules to replace the lack of excretory function.

Artificial and bioartificial support systems for liver failure: a Cochrane Hepato-Biliary Group Protocol

AIMS/BACKGROUND

Liver support systems may bridge patients to liver transplantation or recovery from liver failure. This review is to evaluate the beneficial and harmful effects of artificial and bioartificial support systems for acute and acute-on-chronic liver failure.

DATA SOURCES

Randomized trials on any support system versus standard medical therapy will be included irrespective of publication status or language. Non-randomized studies are included in explorative analyses. Trials will be identified through bibliographies, correspondence with original investigators, and electronic searches (Cochrane Hepato-Biliary Group Controlled Trials Register, Cochrane Controlled Trials Register, MEDLINE, EMBASE, and The Chinese Biomedical Database).

METHODS OF THE REVIEW

The extracted data will include characteristics of trials, patients, interventions, and all outcome measures. Methodological quality will be assessed by the randomization, follow up, and blinding. The RevMan and STATA will be used for statistical analyses. Sources of heterogeneity and methodological quality in the assessment of the primary outcome will be explored by sensitivity analyses and meta-regression.

Literature overview on artificial liver support in fulminant hepatic failure: a methodological approach

Artificial liver support is a therapeutic option for subjects with fulminant hepatic failure. Results of these studies suggest a possible favourable effect on this condition. The aim of the present review is to evaluate not the results of the different artificial systems available but the methodology used to achieve these results. A computer and manual search of the literature was performed; 832 pertinent references were retrieved. Seventy-seven were full papers reporting the application of artificial liver support in animals or humans (15 RCTs (3 in humans, 12 in animals), 53 uncontrolled phase I trials, 9 case reports). The results of this review indicate that, although the rationale of artificial liver support as shown by animal studies is acceptable, the widespread use in clinical practice is not justified and a controlled design for the studies on artificial liver support systems is mandatory.

Influence of hydroxy ethyl starch infusion on serum bilirubin levels in cirrhotic patients treated with artificial liver support

Serum bilirubin levels are commonly used to assess extracorporeal detoxification by liver support systems. We tested the hypothesis that intravenous colloids administered before liver support treatment could confound bilirubin values. Eight cirrhotic patients received an infusion of a 6% hydroxy ethyl starch solution (10 ml/kg, 30 minutes) before detoxification using a liver support system (FPSA). Bilirubin was measured before and 1 hour after infusion, and after FPSA treatment (7 hours). Infusion of hydroxy ethyl starch was associated with a drop in bilirubin values (mean, 18%, range, 1-44%, p=0.03 versus baseline values). Bilirubin levels were further reduced during FPSA treatment (mean, 27%, range, 22-34%; p=0.02 versus pretreatment values). In conclusion, hydroxy ethyl starch solution may decrease bilirubin levels in hyperbilirubinemic cirrhotic patients receiving extracorporeal detoxification. The role of potentially confounding factors in liver support studies is discussed further.

Extracorporeal support of the failing liver

Successes in machine-based extracorporeal support for different organ functions stimulated research in the field of liver support approximately 50 years ago. Initial failure to improve outcome using detoxification methods like dialysis, blood and plasma exchange, or plasmapheresis over sorbents fueled interest in biologic liver support concepts using bioreactors or combined methods. New device configurations, technical improvement of existing detoxification methods, and the refinement in cell culture techniques led to a boost in research on biologic and nonbiologic approaches. Currently, many systems are in the preclinical phase or have entered clinical studies. A number of completed clinical trials have reported a favorable therapeutic impact of the most advanced solutions on the course and outcome of liver failure. Often, findings must be reconfirmed. However, current knowledge suggests that extracorporeal liver support can successfully stabilize liver function, improve the clinical condition of patients, and considerably improve survival in certain subgroups of patients with fulminant hepatic failure and acute decompensation of chronic hepatic failure. Although the initial focus of liver support methods was bridging to liver transplantation, bridging to recovery of organ function and treatment of intractable pruritus are now valuable indications.

Extracorporeal blood detoxification by sorbents in treatment of hepatic encephalopathy

Extracorporeal blood detoxification by sorbent therapy long has been applied in treatment of hepatic failure and encephalopathy, starting with hemoperfusion columns and more recently with the currently marketed Liver Dialysis Unit. Liver Dialysis employs hemodiabsorption (dialysis of blood against powdered sorbents including charcoal and cation exchanger) to remove selectively numerous small-molecular-weight toxins of hepatic failure. Liver Dialysis is used in treatment of acute hepatic encephalopathy (AHE) because of decompensation of chronic liver disease (A-on-C) or fulminant hepatic failure (FHF). Controlled, prospective and randomized studies of daily 6-hour Liver Dialysis have shown physiologic and neurologic improvement of patients with AHE, regardless of etiology. Liver dialysis significantly improved the incidence of positive outcomes (recovery of hepatic function or improvement for transplant) of A-on-C patients versus controls (71.5% treated, and 35.7% control, P =.036), but had an insignificant improvement in outcome of patients with FHF as compared with the control group. Other extracorporeal sorbent devices are now in clinical testing phase. The molecular adsorbent regenerating system (MARS) device employs a polysulfone high-permeability dialyzer with albumin on the dialysate side to aid transfer of protein-bound toxins such as bilirubin and bile acids across the membranes. Sorbent columns of charcoal and an anion exchanger remove hepatic toxins from the albumin dialysate, and a second dialyzer removes water-soluble toxins, such as ammonium. Clinical results of daily MARS treatments of patients with hepatic failure are similar to that of Liver Dialysis, with neurologic and physical improvement occurs in most patients with AHE, and improved outcome for patients with A-on-C. The system extends the life of patients with hepatorenal syndrome. PF-Liver Dialysis is an experimental device combining hemodiabsorption with push-pull sorbent-based pheresis with powdered sorbent surrounding plasmafilters. PF-Liver Dialysis (Hemocleanse, Inc, W. Lafayette, IN) has been tested in a few patients with hepatic failure, grade 3-4 encephalopathy, and respiratory and kidney insufficiency. Treatments appeared to be safe and resulted in marked decreases in plasma levels of bilirubin, aromatic amino acids, ammonium, creatinine, and interleukin-1beta (IL-1beta). The PF add-on module adds the capability to Liver Dialysis to remove bilirubin, bile acids, and other strongly protein-bound toxins from treated patients and may be of clinical benefit in management of patients with the most severe hepatic failure and encephalopathy, including patients with FHF or concomitant sepsis.

Treatment of systemic inflammatory response syndrome by push-pull powdered sorbent pheresis: a Phase 1 clinical trial

An FDA-approved Phase 1 feasibility study was performed in two centers to determine the safety of the BioLogic-DTPF (detoxifier/plasma filter) system for the treatment of patients with systemic inflammatory response syndrome (SIRS). This device combines hemodiabsorption (dialysis of blood against powdered sorbents with the BioLogic-DT system) with push-pull sorbent-based pheresis (the PF add-on module). Eight adult ICU patients with both SIRS and multiple organ failure participated in the study. One 6 h treatment was planned for each patient with powdered charcoal as sorbent for 4 patients and a combination of charcoal/silica in the PF sorbent bag for 4 patients. The treatments appeared to have no negative effects in 7 patients, but 1 patient died during treatment due to progressive cardiac failure. Sepsis was resolved in 5 of the 8 patients. However, there were only 2 long-term survivors of the group. The addition of the PF module should improve the chemical function of the BioLogic-DT by allowing removal of protein-bound toxins such as cytokines. The selected patients tolerated treatment by the DTPF system well, but proof of benefit of the device remains to be proven in a Phase 2 clinical trial with randomized controls.

Powdered sorbent liver dialysis and pheresis in treatment of hepatic failure

The Liver Dialysis Unit (the Unit) is a liver-assist device that employs hemodiabsorption (dialysis of blood against powdered sorbents) to selectively remove numerous small molecular weight toxins of hepatic failure. The Unit has been cleared by the Food and Drug Administration and is indicated and marketed for treatment of acute hepatic encephalopathy (AHE) due to decompensation of chronic liver disease (A-on-C) or fulminant hepatic failure (FHF). Controlled, prospective, and randomized studies of liver dialysis were conducted at several centers, enrolling 56 patients with AHE, grades II-IV with or without renal and respiratory insufficiency or failure. Liver dialysis treatments were for 6 h daily, 1-5 days with similar observation periods for control patients. Physiologic status, neurologic status, and outcome (recovery of hepatic function, improvement for transplant, or death) were measured, and results were compared for treated patients versus controls for patients with A-on-C and patients with FHF. Liver dialysis resulted in physiologic and neurologic improvement of patients with AHE, regardless of etiology. Liver dialysis significantly improved the incidence of positive outcomes (recovery of hepatic function or improvement for transplant) of A-on-C patients versus controls (71.5% treated, 35.7% control, p = 0.036), but had an insignificant improvement in the outcome of patients with FHF as compared with the control group. Among the overall 31 treated patients, 51.6% survived. Outcome was not negatively affected by the presence of kidney failure or respiratory failure. The plasmafilter unit (PF-Unit) combines hemodiabsorption with push-pull sorbent-based pheresis (the PF add-on module, with powdered sorbent surrounding plasmafilters). At blood flow rates of 200 ml/min, the system clears creatinine and aromatic amino acids at 120-160 ml/min, unconjugated bilirubin at 20-40 ml/min, and cytokines at 15-25 ml/min. The PF-Unit has been tested in a few patients with hepatic failure with Grades III and IV encephalopathy, and respiratory, and kidney insufficiency. Treatment appeared to be safe, and there were no significant hematologic changes. Physiologic changes included improved blood pressure, and encephalopathy, and stable urine output. Chemical changes included a decrease in the plasma levels of bilirubin, aromatic amino acids, ammonium, creatinine, and IL-1beta. The PF add-on module adds the capability to the Unit to remove bilirubin and other strongly protein-bound toxins from treated patients and may be of clinical benefit in the management of patients with the most severe hepatic failure and encephalopathy, including patients with FHF or concomitant sepsis.