Extracorporal liver support with molecular adsorbents recirculating system in patients with hepatitis B-associated fulminant hepatic failure

Extracorporeal Liver Support Systems in Paediatric Liver Failure

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

Effects of intraperitoneal albumin on systemic and cerebral hemodynamics in a swine model of acute liver failure

BACKGROUND

Currently, albumin dialysis is the most widely used nonbiological liver support system. We hypothesized that direct peritoneal albumin exposure in the peritoneal cavity would stabilize blood flow and prevent liver and brain injury, in the same way that had previously been seen with extracorporeal albumin dialysis systems.

MATERIALS AND METHODS

Fourteen Landrace pigs (weight 25-30 kg) underwent 70% right hepatectomy and were randomly assigned into a control (C, n = 7) and an intraperitoneal albumin treated group (A, n = 7). The systemic, cerebral, and pulmonary hemodynamic parameters of the animals were recorded at 0, 6, 9, and 12 hr following reperfusion of the liver remnant.

RESULTS

Mean arterial blood pressure, cardiac output, and stroke volume were significantly higher in group A at the end of the experiment. Significantly higher mean intracranial pressure (ICP) values were observed in group C compared to group A, both at 9 hr (21.3 ± 5.2 versus 14.1 ± 3.5 mmHg, p < .0005) and 12 hr (23 ± 4.3 versus 11 ± 3.5 mmHg, p < .0005). On the contrary, cerebral perfusion pressure (CPP) remained stable in albumin-treated groups after the sixth postreperfusion hour. Mean pulmonary artery pressure and pulmonary vascular resistance (PVR) were significantly lower in group A compared to group C at 12 hr, while pulmonary capillary wedge pressure (PCWP) stabilized in albumin-treated animals.

CONCLUSIONS

This study provides the first evidence that intraperitoneal albumin may be able to attenuate systemic, pulmonary, and cerebral hemodynamic disturbances associated with acute liver failure.

Hemodynamic effects of albumin dialysis in patients with liver failure: for better or for worse?

Liver failure, irrespective of is cause, is frequently associated with multi-organ dysfunction, including hemodynamic instability, and renal and cerebral insufficiency. As a result of the combined impact of these complications, liver failure carries an exceptionally high risk of mortality. A central role in the etiopathogenesis of different end-organ manifestations, as well as in the aggravation of the underlying liver failure, has been attributed to the hyperdynamic (hypotensive) state, which is characterized by a reduced systemic vascular resistance and mean arterial pressure, as well as an increased cardiac index, heart rate, and total plasma volume. Since the accumulation of toxins due to the decreased detoxification capacity by the failing liver is considered vital herein, the emergence of extracorporeal liver support has provided a rational basis for the potential reversal of these phenomena. The present article critically reviews data with regard to the hemodynamic effects of artificial liver support in the context of liver failure. Although these are scarce for acute liver failure, several uncontrolled series and small randomized trials have clearly documented that artificial liver support is able to improve both portal hypertension and the associated systemic circulatory dysfunction in patients with acute-on-chronic liver failure. The molecular basis for these effects have been related to temporary changes and/or elimination in endogenous vasoactive substances, improved albumin binding capacity, or restoration of oxidative stress-mediated damage to albumin.

Hemodynamics and metabolic studies on septic shock in patients with acute liver failure

BACKGROUND

Acute liver failure is often accompanied by hyperdynamic circulation, which is also a characteristic of septic shock. Pre-existing acute liver failure may worsen the hemodynamic impairment and prognosis in sepsis.

AIMS

To evaluate the hemodynamic and metabolic characteristics and clinical outcomes of septic shock in patients with acute liver failure.

METHODS

Twenty patients with acute liver failure and 19 patients without preexisting liver disease were evaluated. Systemic hemodynamics, arterial and mixed vein blood gases, arterial lactate levels, plasma renin activity, and plasma aldosterone levels were checked during the early phase of septic shock.

RESULTS

In acute liver failure group, cardiac index (4.92 +/- 1.13 vs 3.69 +/- 1.06 L/min per square meter, P < .001) and oxygen delivery (604.7 +/- 139.7 vs 485.4 +/- 137.3 mL/min per square meter, P = .011) were significantly higher than those without preexisting liver diseases, while systemic vascular resistance index (1041.2 +/- 503.3 vs 1409 +/- 505.25 dyne.s/cm(5).m(2)), oxygen consumption (119.1 +/- 29.2 vs 162.4 +/- 49.4 mL/min per square meter) and oxygen extraction ratio (20% +/- 6% vs. 32% +/- 8%) were significantly higher in the latter group. Furthermore, the patients with acute liver failure had higher arterial lactate (P = .026), plasma renin activity (P = .03), plasma aldosterone levels (P < .001), and intensive care unit as well as hospital mortality rates (P = .005, and 0.02 respectively).

CONCLUSIONS

In patients with acute liver failure, septic shock was characterized by an accentuated hyperdynamic circulation, hyperlactatemia and an augmented renin-angiotensin-aldosterone system activity. Pre-existing liver failure has a significant impact on the disease severity of septic shock and portends a grave prognosis.

Liver transplantation in children with fulminant hepatic failure: The UCL experience

The outcome of pediatric LT for FHF was shown to be poor in our center. To better understand such results, recipient and transplant parameters with a putative impact on post-transplant outcome were analyzed in LT for FHF. Between March 1984 and June 2002, 33 children with FHF received a primary liver allograft. The overall results in this series were studied with respect to pre-operative demographic and metabolic variables, peri-operative events, and outcome. Five-yr patient and graft survivals were 71% and 66%, respectively, with a retransplantation rate at 18%. Incidences of perioperative hemorrhage, of HAT and PVT were 14%, 8%, and 4%, respectively. Five-yr acute rejection-free survival rate was 55%. These data confirm the worse outcome following LT for FHF when compared with LT in elective, non-malignant indications such as BA; results in FHF could not be related to surgical or immunological complications in the post-transplant period and it is hypothesized that the MOF associated with FHF contributes to early post-transplant mortality which would justify special management, including aggressive renal and hepatic support.

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

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

Association of reduced extracellular brain ammonia, lactate, and intracranial pressure in pigs with acute liver failure

We previously demonstrated in pigs with acute liver failure (ALF) that albumin dialysis using the molecular adsorbents recirculating system (MARS) attenuated a rise in intracranial pressure (ICP). This was independent of changes in arterial ammonia, cerebral blood flow and inflammation, allowing alternative hypotheses to be tested. The aims of the present study were to determine whether changes in cerebral extracellular ammonia, lactate, glutamine, glutamate, and energy metabolites were associated with the beneficial effects of MARS on ICP. Three randomized groups [sham, ALF (induced by portacaval anastomosis and hepatic artery ligation), and ALF+MARS] were studied over a 6-hour period with a 4-hour MARS treatment given beginning 2 hours after devascularization. Using cerebral microdialysis, the ALF-induced increase in extracellular brain ammonia, lactate, and glutamate was significantly attenuated in the ALF+MARS group as well as the increases in extracellular lactate/pyruvate and lactate/glucose ratios. The percent change in extracellular brain ammonia correlated with the percent change in ICP (r(2) = 0.511). Increases in brain lactate dehydrogenase activity and mitochondrial complex activity for complex IV were found in ALF compared with those in the sham, which was unaffected by MARS treatment. Brain oxygen consumption did not differ among the study groups.

CONCLUSION

The observation that brain oxygen consumption and mitochondrial complex enzyme activity changed in parallel in both ALF- and MARS-treated animals indicates that the attenuation of increased extracellular brain ammonia (and extracellular brain glutamate) in the MARS-treated animals reduces energy demand and increases supply, resulting in attenuation of increased extracellular brain lactate. The mechanism of how MARS reduces extracellular brain ammonia requires further investigation.

Epidemiology of acute liver failure

Acute liver failure (ALF) is an uncommon disorder that leads to jaundice, coagulopathy, and multisystem organ failure. Its definition is based on the timing from onset of jaundice to encephalopathy. In 2005, ALF accounted for 6% of liver-related deaths and 7% of orthotopic liver transplants (OLT) in the United States. Several classification systems have been developed for ALF, with the King's College criteria most widely used for prediction of OLT. Specific diagnostic tests should be implemented to identify the cause of ALF, which will help to determine its treatment and prognosis. Viral hepatitis was previously reported to be the most common cause of ALF in the United States, but acetaminophen overdose and idiosyncratic drug reactions have emerged as the most frequent causes in recent studies. Malignancy is an uncommon cause of ALF, and thus imaging studies may not be useful in this setting, but liver biopsy may be beneficial in selected cases. An overall strategy for ALF should start with identifying the cause, assessing the prognosis, and early transfer to a transplantation center for suitable candidates. OLT has emerged as a life-saving procedure leading to marked improvement in survival rates. Improved surgical techniques, immunosuppression, and comprehensive care have led to an overall survival rate of approximately 65% with OLT. N-acetylcysteine is effective in ALF caused by acetaminophen overdose, with results strongly related to how soon it is given rather than the route of administration. Liver support systems show potential for the treatment of ALF, but their role needs validation in large multicenter randomized trials.

MARS in the treatment of liver failure: controversies and evidence

Molecular Adsorbent Recirculation System (MARS) is a form of extracorporeal detoxification system used as an artificial liver support system. Numerous studies have been published on the topic, with the majority of them describing the capability of MARS in removing albumin-bound toxins and improving systemic hemodynamics. Whether such improvement could be translated into survival benefit is still uncertain, given the paucity of randomized controlled trials available. The outcome of patients receiving MARS treatment is difficult to analyze because liver failure patients constitute a heterogeneous population and different subgroups carry different prognoses. An evidence-based recommendation on the timing of MARS initiation is not available and currently MARS is usually commenced for hyperbilirubinemia or presence of complications of liver failure. MARS is in general a safe procedure, but there are still potential complications that need to be cautioned, along with various operative issues that are worth attention. The future prospects of MARS would rely on the completion of adequately powered randomized controlled trials.