Hepatic blood flow and splanchnic oxygen consumption in patients with liver failure. Effect of high-volume plasmapheresis

Therapeutic plasma exchange provides native liver survival benefit in children with acute liver failure: A propensity score-matched analysis

OBJECTIVES

This study aimed to evaluate the safety and efficacy of therapeutic plasma exchange (TPE) in pediatric acute liver failure (PALF).

METHODS

All children aged 2-18 years with PALF were included. The intervention cohort included a subset of PALF patients undergoing complete three sessions of TPE, whereas the matching controls were derived by propensity score matching from the patient cohort who did not receive any TPE. Propensity matching was performed based on the international normalized ratio (INR), grade of hepatic encephalopathy (HE), age, bilirubin, and ammonia levels. The primary outcome measure was native liver survival (NLS) in the two arms on day 28.

RESULTS

Of the total cohort of 403 patients with PALF, 65 patients who received TPE and 65 propensity-matched controls were included in analysis. The 2 groups were well balanced with comparable baseline parameters. On day 4, patients in the TPE group had significantly lower INR (P = 0.001), lower bilirubin (P = 0.008), and higher mean arterial pressure (MAP) (P = 0.033) than controls. The NLS was 46.15% in the TPE arm and 26.15% in the control arm. The overall survival (OS) was 50.8% in the TPE arm and 35.4% in the control arm. Kaplan-Meier survival analysis showed a significantly higher NLS in patients receiving TPE than controls (P = 0.001). On subgroup analysis, NLS benefit was predominantly seen in hepatitis A-related and indeterminate PALF.

CONCLUSION

TPE improved NLS and OS in a propensity-matched cohort of patients with PALF. Patients receiving TPE had lower INR and bilirubin levels and higher MAP on day 4.

Hepatic encephalopathy

Hepatic encephalopathy (HE) is a prognostically relevant neuropsychiatric syndrome that occurs in the course of acute or chronic liver disease. Besides ascites and variceal bleeding, it is the most serious complication of decompensated liver cirrhosis. Ammonia and inflammation are major triggers for the appearance of HE, which in patients with liver cirrhosis involves pathophysiologically low-grade cerebral oedema with oxidative/nitrosative stress, inflammation and disturbances of oscillatory networks in the brain. Severity classification and diagnostic approaches regarding mild forms of HE are still a matter of debate. Current medical treatment predominantly involves lactulose and rifaximin following rigorous treatment of so-called known HE precipitating factors. New treatments based on an improved pathophysiological understanding are emerging.

Definition and classification of acute-on-chronic liver diseases

Patients with chronic liver diseases (CLDs) develop acute liver injury and/or acute decompensation under the attack of various precipitants and present with significantly elevated alanine aminotransferase and/or total bilirubin levels, liver failure, or acute decompensation of liver cirrhosis, which is called acute-on-CLD (AoCLD). AoCLD accounts for the majority of patients hospitalized in the Department of Hepatology or Infectious Diseases. AoCLD is complicated by various clinical types, the severity of the disease, and may pose a high risk of death. To date, the definition of AoCLD is still vague, and a consensus concept of the clinical classification is lacking. This review aimed to define the concept and clinical types of AoCLD based on related studies and the literature.

Plasma Exchange in Acute and Acute on Chronic Liver Failure

Liver failure in the context of acute (ALF) and acute on chronic liver failure (ACLF) is associated with high mortality in the absence of a liver transplant. For decades, therapeutic plasma exchange (TPE) is performed for the management of immune-mediated diseases. TPE has emerged as an attractive extracorporeal blood purification technique in patients with ALF and ACLF. The basic premise of using TPE is to remove the toxic substances which would allow recovery of native liver functions by facilitating liver regeneration. In recent years, encouraging data have emerged, suggesting the benefits of TPE in patients with liver failure. TPE has emerged as an attractive liver support device for the failing liver until liver transplantation or clinical recovery. The data in patients with ALF suggest routine use of high-volume TPE, while the data for such a strategy are less robust for patients with ACLF.

Safety of treating acute liver injury and failure

INTRODUCTION

Acute liver injury and progression to acute liver failure can be life-threatening conditions that require prompt careful clinical assessment and therapeutic management.

AREAS COVERED

The aim of this article is to review the safety and side effect profile of pharmacological therapies used in the treatment of acute liver injury with specific focus on hepatic toxicity. We performed an extensive literature search with the terms 'acute liver injury,' 'acute liver failure,' 'therapy,' 'safety,' 'adverse reactions' and 'drug induced liver injury.' A thorough discussion of the main drugs and devices used in patients with acute liver injury and acute liver failure, its safety profile and the management of complications associated to therapy of these conditions is presented.

EXPERT OPINION

Several pharmacological approaches are used in acute liver injury and acute liver failure in an empirical basis. Whilst steroids are frequently tried in serious drug-induced liver injury there is concern on a potential harmful effect of these agents because of the higher mortality in patients receiving the drug; hence, statistical approaches such as propensity score matching might help resolve this clinical dilemma. Likewise, properly designed clinical trials using old and new drugs for subjects with serious drug-induced liver injury are clearly needed.

Association between effective hepatic blood flow and the severity and prognosis of hepatitis B virus-related acute on chronic liver failure

BACKGROUND

Hepatic inflammation resulted in hepatocyte necrosis and microcirculatory dysfunction in acute on chronic liver failure (ACLF) with cirrhosis or not. The influence of effective hepatic blood flow (EHBF) on the severity of liver failure has not been fully elucidated.

AIM

The aim of this study was to assess the correlation between the EHBF and the severity and the prediction of 90-day mortality rate of hepatitis B virus-related ACLF (HBV-ACLF).

METHODS

In this retrospective study, patients hospitalized for HBV-ACLF or decompensated cirrhosis and who underwent an indocyanine green (ICG) clearance test between June 2016 and July 2018 were enrolled. EHBF was measured by the ICG clearance test and patients were categorized into the ACLF without cirrhosis (HBV-ACLF-no-Cir), ACLF with cirrhosis (HBV-ACLF-Cir) and decompensated cirrhosis (HBV-De-Cir).

RESULTS

A total of 522 patients (HBV-ACLF-no-Cir: 84, HBV-ACLF-Cir: 111 and HBV-De-Cir: 327) were enrolled. The mean EHBF in the HBV-De-Cir was significantly higher than that in the HBV-ACLF-no-Cir and HBV-ACLF-Cir (0.36 vs. 0.21 vs. 0.20 L/min, P < 0.001). EHBF was significantly correlated with the total bilirubin, prothrombin activity and model for end-stage liver disease (MELD) in the HBV-ACLF-no-Cir. The predicted 90-day mortality rate using the MELD, EHBF, ICG-retention rate at 15 min (R15%) and EHBF-R15% scores were similar. The sensitivity and specificity of the EHBF varied between 68.5-80.2% and 45.8-73.7%, respectively. The EHBF-MELD score had the highest specificity.

CONCLUSION

EHBF was significantly lower in the patients with ACLF compared to decompensated cirrhosis. The EHBF were closely related to the severity of HBV-ACLF and can be used for predicting the 90-day mortality rate of HBV-ACLF.

Initial experience with high-volume plasma exchange in patients with acute liver failure

BACKGROUND/AIMS

High-volume plasma exchange (HVPE), defined as an exchange of 8 to 12 L per day per procedure or 15% of the ideal body weight with fresh frozen plasma, has shown promising results in improving the survival of patients with acute liver failure (ALF). However, clinical evidence is limited. The aim of this study was to report our initial experience using HVPE as a bridge treatment in patients with ALF.

METHODS

We retrospectively reviewed 32 consecutive patients awaiting liver transplantation (LT) due to ALF between 2013 and 2020 at Samsung Medical Center in Korea. HVPE has been used for patients with ALF since May 2016 at our institution.

RESULTS

During the study period, 16 patients received HVPE. After HVPE, coagulopathies (INR, 4.46 [2.32-6.02] vs 1.48 [1.33-1.76], P < .05), total bilirubin (22.6 [9.1-26.4] vs 8.9 [5.6-11.3], P < .05), alanine aminotransferase (506 [341-1963] vs 120 [88-315], P < .05), and ammonia levels (130.6 [123.7-143.8] vs 98.2 [84.2-116.5], P < .05) were improved. Improvement in the hepatic encephalopathy grade was observed in four patients. Among 16 patients who received HVPE, 12 patients were bridged to LT, and three patients recovered spontaneously. The overall survival was 94% and 69%, respectively at 30 days in patients who received and did not receive HVPE (P = .068). Among 18 patients with high chronic liver failure-sequential organ failure assessment scores (≥13), the overall survival was significantly better for those who received HVPE than for those who did not (91% vs 29%, respectively, at 30 days, P < .05).

CONCLUSIONS

Our initial clinical experience with HVPE suggests that HVPE can be a viable option in improving the outcomes of patients presenting with ALF.

Infectious Complications in Patients Who Received High-Volume Plasma Exchange Prior to Liver Transplant: A Case Report

Acute liver failure is a rare but life-threatening medical emergency. Despite advancements in medical management, mortality rates of acute liver failure remain high. Currently, liver transplant is the only definitive therapeutic option available. High-volume plasma exchange has been shown to increase transplant-free survival in patients with acute liver failure before liver transplant. However, the occurrence of infectious complications in patients who receive this treatment has not been well studied. We report 2 cases of severe opportunistic infections occurring within 30 days of transplant in patients who underwent high-volume plasma exchange before liver transplant.

Enhancing Filtration Rates by the use of Blood Flow around the Capillaries of Plasmafilters: An in Vitro Study

As the low clearance rate of plasmaseparation limits its use in the treatment of patients suffering from liver failure, sepsis or MOF, we intend to develop strategies for a plasmaseparation unit which increases plasmafiltration rates. Our first question focused on whether commercially available plasmaseparation filters, and in particular their membranes, are suitable for the inversion of blood and plasma compartments. This experimental study was performed using in vitro systems. Commercially available plasmafilters PF2000N (Gambro) and Plasmaflo (Asahi) were compared in both their normal operating mode with blood flow through the capillary lumen, and in the inverse mode. Inverse mode means that blood flows through the outer space of the capillaries while plasma was obtained from the lumen. Heparinised porcine blood (5 I.U./ml) was used in a heated, recirculating in vitro circuit. Our main results were that the normal use of both filter types Plasmaflo and PF2000N enabled maximal blood flows (Qb) of 200 ml/min and filtration rates (Qf) of 25–40 ml/min. Operating the filters in the inverse mode enabled Qb up to 500 ml/min and Qf up to 100 ml/min. Hemolysis, platelet counts and coagulation parameters did not differ significantly regardless of whether the normal or inverse mode was used. The tested plasmafiltration membranes appear to be suitable for use in inverse mode. Although in our experiments, hemocompatibility tests did not indicate severe problems induced by the module geometry, the development of a module specially constructed for blood flow outside of the hollow fibers appears to be necessary in order to minimise shunts and low perfusion areas.

EASL Clinical Practical Guidelines on the management of acute (fulminant) liver failure

The term acute liver failure (ALF) is frequently applied as a generic expression to describe patients presenting with or developing an acute episode of liver dysfunction. In the context of hepatological practice, however, ALF refers to a highly specific and rare syndrome, characterised by an acute abnormality of liver blood tests in an individual without underlying chronic liver disease. The disease process is associated with development of a coagulopathy of liver aetiology, and clinically apparent altered level of consciousness due to hepatic encephalopathy. Several important measures are immediately necessary when the patient presents for medical attention. These, as well as additional clinical procedures will be the subject of these clinical practice guidelines.

Hyperammonemia Is Associated with Increasing Severity of Both Liver Cirrhosis and Hepatic Encephalopathy

Background. Hyperammonemia resulting from chronic liver disease (CLD) can potentially challenge and damage any organ system of the body, particularly the brain. However, there is still some controversy regarding the diagnostic or prognostic values of serum ammonia in patients with over hepatic encephalopathy, especially in the setting of acute-on-chronic or chronic liver failure. Moreover, the association of serum ammonia with worsening Child-Pugh grade of liver cirrhosis has not been studied. Objective. This study was conducted to solve the controversy regarding the association between hyperammonemia and cirrhosis, especially hepatic encephalopathy in chronically failed liver. Material and Methods. In this study, 171 cirrhotic patients had their serum ammonia measured and analyzed by SPSS version 16. Chi-squared test and one-way ANOVA were applied. Results. The study had 110 male and 61 female participants. The mean age of all the participants in years was 42.33 ± 7.60. The mean duration (years) of CLD was 10.15 ± 3.53 while the mean Child-Pugh (CP) score was 8.84 ± 3.30. Chronic viral hepatitis alone was responsible for 71.3% of the cases. Moreover, 86.5% of participants had hepatic encephalopathy (HE). The frequency of hyperammonemia was 67.3%, more frequent in males (N = 81, z-score = 2.4, and P < 0.05) than in females (N = 34, z-score = 2.4, and P < 0.05), and had a statistically significant relationship with increasing CP grade of cirrhosis (χ²(2) = 27.46, P < 0.001, Phi = 0.40, and P < 0.001). Furthermore, serum ammonia level was higher in patients with hepatic encephalopathy than in those without it; P < 0.001. Conclusion. Hyperammonemia is associated with both increasing Child-Pugh grade of liver cirrhosis and hepatic encephalopathy.

High-volume plasma exchange in patients with acute liver failure: An open randomised controlled trial

BACKGROUND & AIMS

Acute liver failure (ALF) often results in cardiovascular instability, renal failure, brain oedema and death either due to irreversible shock, cerebral herniation or development of multiple organ failure. High-volume plasma exchange (HVP), defined as exchange of 8-12 or 15% of ideal body weight with fresh frozen plasma in case series improves systemic, cerebral and splanchnic parameters.

METHODS

In this prospective, randomised, controlled, multicentre trial we randomly assigned 182 patients with ALF to receive either standard medical therapy (SMT; 90 patients) or SMT plus HVP for three days (92 patients). The baseline characteristics of the groups were similar. The primary endpoint was liver transplantation-free survival during hospital stay. Secondary-endpoints included survival after liver transplantation with or without HVP with intention-to-treat analysis. A proof-of-principle study evaluating the effect of HVP on the immune cell function was also undertaken.

RESULTS

For the entire patient population, overall hospital survival was 58.7% for patients treated with HVP vs. 47.8% for the control group (hazard ratio (HR), with stratification for liver transplantation: 0.56; 95% confidence interval (CI), 0.36-0.86; p=0.0083). HVP prior to transplantation did not improve survival compared with patients who received SMT alone (CI 0.37 to 3.98; p=0.75). The incidence of severe adverse events was similar in the two groups. Systemic inflammatory response syndrome (SIRS) and sequential organ failure assessment (SOFA) scores fell in the treated group compared to control group, over the study period (p<0.001).

CONCLUSIONS

Treatment with HVP improves outcome in patients with ALF by increasing liver transplant-free survival. This is attributable to attenuation of innate immune activation and amelioration of multi-organ dysfunction.

Cerebral effects of ammonia in liver disease: current hypotheses

Hyperammonemia is necessary for development of the cerebral complications to liver disease including hepatic encephalopathy and cerebral edema but the mechanisms are unclear. Ammonia is taken up by the brain in proportion to its arterial concentration. The flux into the brain is most likely by both diffusion of NH3 and mediated transport of NH4 (+) . Astrocytic detoxification of ammonia involves formation of glutamine at concentrations high enough to produce cellular edema, but compensatory mechanisms reduce this effect. Glutamine can be taken up by astrocytic mitochondria and initiate the mitochondrial permeability transition but the clinical relevance is uncertain. Elevated astrocytic glutamine interferes with neurotransmission. Thus, animal studies show enhanced glutamatergic neurotransmission via the NMDA receptor which may be related to the acute cerebral complications to liver failure, while impairment of the NMDA activated glutamate-NO-cGMP pathway could relate to the behavioural changes seen in hepatic encephalopathy. Elevated glutamine also increases GABA-ergic tone, an effect which is aggravated by mitochondrial production of neurosteroids; this may relate to decreased neurotransmission and precipitation of encephalopathy by GABA targeting drugs. Hyperammonemia may compromise cerebral energy metabolism as elevated cerebral lactate is generally reported. Hypoxia is unlikely since cerebral oxygen:glucose utilisation and lactate:pyruvate ratio are both normal in clinical studies. Ammonia inhibits α-ketoglutaratedehydrogenase in isolated mitochondria, but the clinical relevance is dubious due to the observed normal cerebral oxygen:glucose utilization. Recent studies suggest that ammonia stimulates glycolysis in excess of TCA cycle activity, a hypothesis that may warrant further testing, in being in accordance with the limited clinical observations.

Liver support systems--a review

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

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

BACKGROUND & AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Hepatorenal syndrome: the 8th International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group

Introduction

Renal dysfunction is a common complication in patients with end-stage cirrhosis. Since the original publication of the definition and diagnostic criteria for the hepatorenal syndrome (HRS), there have been major advances in our understanding of its pathogenesis. The prognosis of patients with cirrhosis who develop HRS remains poor, with a median survival without liver transplantation of less than six months. However, a number of pharmacological and other therapeutic strategies have now become available which offer the ability to prevent or treat renal dysfunction more effectively in this setting. Accordingly, we sought to review the available evidence, make recommendations and delineate key questions for future studies.

Methods

We undertook a systematic review of the literature using Medline, PubMed and Web of Science, data provided by the Scientific Registry of Transplant Recipients and the bibliographies of key reviews. We determined a list of key questions and convened a two-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated recommendations and/or directions for future research.

Results

Of the 30 questions considered, we found inadequate evidence for the majority of questions and our recommendations were mainly based on expert opinion. There was insufficient evidence to grade three questions, but we were able to develop a consensus definition for acute kidney injury in patients with cirrhosis and provide consensus recommendations for future investigations to address key areas of uncertainty.

Conclusions

Despite a paucity of sufficiently powered prospectively randomized trials, we were able to establish an evidence-based appraisal of this field and develop a set of consensus recommendations to standardize care and direct further research for patients with cirrhosis and renal dysfunction.

Acute liver failure

PURPOSE OF REVIEW

Acute liver failure (ALF) results in a multitude of serious complications that often lead to multi-organ failure. This brief review focuses on the pathophysiological processes in ALF and how to manage these.

RECENT FINDINGS

The clinical presentation in ALF ranges from slightly altered conscious level with profound coagulopathy to coma with a catastrophic failure of multiple organs, including uncontrollable cerebral edema and brain death, which is rarely seen in decompensated cirrhosis. Interestingly, ALF patients who recover as the liver is regenerating, usually do not suffer from hepatic or extrahepatic sequelae. In contrast patients surviving acute-on-chronic liver failure will return to a state with incompensated cirrhosis, and eventually need transplantation for survival.In the management of ALF, the use of noradrenalin in combination with continuous high-dose renal replacement therapy, terlipressin, hypertonic sodium chloride, and mannitol can ameliorate systemic vasodilation and attenuate brain edema. Furthermore, liver assist devices seem to improve extrahepatic organ dysfunction and survival.

SUMMARY

Insight into the of pathopysiological mechanisms of ALF that lead to cardiovascular instability, brain edema and development of multiorgan failure has advanced and resulted in improved survival. The role of liver assisting is still unknown but preliminary results indicate a positive effect on survival.

Adjuvant therapeutic plasma exchange in liver failure: assessments of clinical and laboratory parameters

BACKGROUND

Therapeutic plasma exchange (TPE) seems to be an effective approach for clearing toxins, immune-mediated antigens, and other particles from the circulation. The aim of this study was to analyze the positive effects of TPE on clinical and biochemical parameters of liver failure.

PATIENTS AND METHODS

Between January 2001 and March 31, 2005 individuals (men/women, 17/14; median age, 42.7+/-15.8 y) with acute and chronic liver failure who underwent a total of 113 TPEs (median session 3.7) were retrospectively reviewed. TPE was performed using the Fresenius AS-TEC 204 cell separator (Fresenius AG, Germany). The indication for TPE was severe coagulopathy (prothrombin time >20 s), severe hepatic encephalopathy, hyperbilirubinemia, and candidacy for liver transplantation. All patients were examined before and immediately after the last TPE session.

RESULTS

When compared with baseline, there was significant improvement in hepatic encephalopathy stage (from median score 3.0 to 1.0, P=0.001), serum prothrombin time (from median 26.0 to 20.0 s, P=0.003), aminotransferases (P<0.001), and total bilirubin levels (from median 35.0 to 23.3 mg/dL, P<0.001) after TPE. Thirteen of the thirty-one individuals (41.9%) died in the hospital. The mean follow-up period of 18 survival patients was 35.9+/-5.6 months and 10 of those survived (55.6%, 10/18). No serious adverse effect of TPE was observed in any of the patients during or after completion of TPE. Only 6 patients experienced minor transfusion reactions.

CONCLUSIONS

TPE seems to be effective in improving hepatic encephalopathy stage and liver tests in individuals with acute and chronic liver failure. The data suggest that TPE is safe and tolerable in such individuals, however, overall survival remains poor despite TPE.

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.

Personal view: current role of artificial liver support devices

Enthusiasm for liver support devices, particularly cell-based biological systems and albumin dialysis, increased over the last decade and there has been considerable clinical activity both within and without the construct of clinical trials. Most data have been generated on patients with acute liver failure or in patients with decompensation of chronic liver disease, often referred to as acute-on-chronic liver failure. In acute liver failure liver, liver support devices are more realistically being used as a 'bridge' to liver transplantation rather than to transplant-free survival. In acute-on-chronic liver failure the clinical objective of attaining clinical stability with treatment appears more achievable. The so-called bioartificial liver device, based on porcine hepatocytes, is the most extensively evaluated biological device. A sizeable clinical trial failed to demonstrate efficacy, but secondary analyses suggest it would be unwise to assume futility had been established with this device. Molecular adsorbent recirculating system leads the way in the non-biological category in terms of the number of patients treated, but data from large clinical trials are not yet available. One of the strongest conclusions of this review is that the amount of high-quality data available on liver support devices dramatically understates the effort and money that have been expended in their assessment. It is very clear that randomized controlled trials are mandatory to establish clinical efficacy, but it is less clear how the ideal trial should be constructed.

Hyperlactatemia in patients with non-acetaminophen-related acute liver failure

AIM: To characterize hyperlactatemia in patients with non-acetaminophen acute liver failure (ALF) in an attempt to clarify the mechanisms implicated and the role as a prognosis factor.

METHODS: In the setting of liver transplantation, 63 consecutive patients with non-acetaminophen acute liver failure were studied in relation to tissue oxygenation, hemodynamic and metabolic parameters. Before and after transplantation, the number of infected patients and outcome were registered.

RESULTS: Acute ALF showed higher levels of lactate than subacute ALF (5.4 ± 1 mmol/L versus 2.2 ± 0.6 mmol/L, P = 0.01). Oxygenation parameters were within the normal range. Lactate levels showed good correlation with respiratory quotient (r = 0.759, P < 0.005), mean glucose administration (r = 0.664, P = 0.01) and encephalopathy (r = 0.698, P = 0.02), but not with splanchnic arteriovenous difference in PCO2, pH and the presence of infection (P = 0.1). Portal vein lactate was higher (P < 0.05) than arterial and mixed venous lactate, suggesting its production of hyperlactatemia in the intestine and spleen. The presence of infection was an independent predictor of survival.

CONCLUSION: Hyperlactatemia is not a prognosis factor due to byproduct of the overall acceleration in glycolysis.

Review article: non-biological liver support in liver failure

Liver failure, whether acute or acute-on-chronic, remains an important cause of morbidity and mortality. The lack of liver detoxification, metabolic and regulatory functions of the liver leads to life-threatening complications, such as renal failure, altered immune response, hepatic coma and systemic haemodynamic dysfunction, eventually culminating in multiorgan failure. Current medical therapy involves the management of the precipitating event and treatment of complications until the liver eventually recovers, leaving us with no other treatment options than transplantation if these attempts fail. However, the shortage in cadaveric organs and other transplant-related problems, have prompted the need for alternative methods to provide liver support. As liver failure is often potentially reversible, considerable effort has been invested in the development of liver support systems. Currently, most of the experience is available for non-biological support systems. They represent the focus of this review, which aims to define the goals of liver support, to describe the design of the different existing devices and to analyse the available data to determine their current status in the management of patients with liver failure.

Evolution of intrahepatic carbon, nitrogen, and energy metabolism in a D-galactosamine-induced rat liver failure model

A clearer picture of the hepatic metabolic pathways affected by fulminant hepatic failure (FHF) would help develop nutritional support and nonsurgical therapies for FHF. We characterized the evolution of hepatic metabolism in a rat model of FHF using an isolated perfused liver system together with a mass-balance model of intermediary metabolism. Principal component analysis (PCA) was used to identify potential new sensitive markers for FHF. To induce FHF, rats were given two D-galactosamine injections under fasting conditions. Controls were fasted only. Livers were harvested 1, 4, 8, and 12 h later and perfused with Eagle minimal essential medium supplemented with amino acids and bovine serum albumin, and equilibrated with 95% O2/5% CO2. At the 1 h time point, lactate release increased concomitant with a decrease in gluconeogenesis, TCA cycle and mitochondrial electron transport fluxes. At 4 h, amino acid metabolism and urea cycle fluxes were significantly depressed. By 8 h, gluconeogenesis had switched to glycolysis. By 12 h, amino acid metabolism was broadly inhibited, and there was a net release of many amino acids. Mass-balance analysis shows that the main source of ATP production in the FHF liver gradually changed from mitochondrial oxidative phosphorylation to glycolysis. PCA suggests that a linear combination of glucose, lactate, and glutamine concentrations in arterial plasma is a sensitive marker for FHF. We conclude that D-galactosamine causes early mitochondrial dysfunction while glycolytic ATP synthesis remains functional. Markers that are indirectly linked to these pathways may be used to evaluate the progression of FHF.

Splanchnic metabolism in acute liver failure and sepsis

PURPOSE OF REVIEW

A number of papers have suggested that the splanchnic circulation and oxidative metabolism are compromised in critical illness. This review discusses this hypothesis and outlines the recent advances in the understanding of splanchnic metabolism with special focus on acute liver failure and hyperdynamic sepsis.

RECENT FINDINGS

Splanchnic blood flow, oxygen delivery, and consumption are increased in both acute liver failure and sepsis. The capability of the liver to extract oxygen, even under extreme conditions, renders the liver less prone to hypoxia. A common feature of acute liver failure and sepsis is a hypermetabolic state with enhanced glycolysis and production of lactate and pyruvate. Human studies on other features of intermediary metabolism are sparse, but there are indications that several intermediary processes are severely compromised in patients with acute liver failure, whereas these processes are maintained in sepsis.

SUMMARY

There is increasing evidence that both acute liver failure and sepsis are accompanied by a hypermetabolic state in the hepatosplanchnic area, characterized by enhanced glycolysis and hyperlactatemia. This should not be rigorously interpreted as an indication of hypoxia. In fact, clinically important splanchnic hypoxia may be a relatively uncommon phenomenon in such patients.

Systemic hemodynamic effects of treatment with the molecular adsorbents recirculating system in patients with hyperacute liver failure: a prospective controlled trial

The aim of the study is to evaluate the effect of a single treatment with the molecular adsorbents recirculating system (MARS) on systemic hemodynamics and oxygen consumption (VO(2)) in patients with hyperacute liver failure (HALF). In a controlled design, eight patients with HALF were assigned to a 6-hour MARS treatment, and five patients, to a control group that was mechanically cooled to match the MARS group. Systemic hemodynamic variables were determined hourly during the study period. In the MARS group, systemic vascular resistance index increased by 46% from 1,215 +/- 437 to 1,778 +/- 710 dynes x s x cm(-5) x m(-2) (P <.0001), which significantly exceeded a 6% increase in the control group. Mean arterial pressure increased from 69 +/- 5 to 83 +/- 11 mm Hg in the MARS group (P <.0001) and was unchanged in the control group. Cardiac index decreased by 20% from 4.6 +/- 1.8 to 3.7 +/- 1.1 L/min x m(-2) (P =.0007) in the MARS group and by 7% in the control group. Heart rate decreased from 105 +/- 21 to 85 +/- 15 beats/min in the MARS group (P <.0001) and was unchanged in the control group. In the MARS group, oxygen delivery decreased from 621 +/- 198 to 486 +/- 141 mL/min x m(-2) (P <.05), and VO2, from 142 +/- 31 to 112 +/-21 mL/min x m(-2) (P <.05). Arterial lactate and pH levels were unchanged. In conclusion, systemic hemodynamic values tend to normalize, whereas systemic VO(2) decreases during MARS treatment in patients with HALF. These effects cannot be explained by the degree of cooling associated with MARS.

Highly urgent liver transplantation: possible impact of donor-recipient ABO matching on the outcome after transplantation

BACKGROUND

Survival after liver transplantation for fulminant hepatic failure has been reported to be less favorable than survival for patients with chronic liver diseases.

METHODS

We have studied all patients (n=229) undergoing highly urgent liver transplantation from 1990 to 2001 in the Nordic countries. The impact of patient and donor characteristics, with emphasis on donor-recipient ABO matching (identical, compatible, incompatible), has been studied.

RESULTS

One-year and 3-year patient survival rates were 73% and 70% for the total period and 86% and 78% for the last 4-year period. Patients receiving an ABO-compatible liver allograft had significantly lower patient survival rates than those receiving an ABO-identical donor organ (1-year patient survival rates 66% of vs. 79%, P=0.03). Graft survival rates varied less (1-year graft survival rates of 64% vs. 74%, P=0.09). Patients receiving an ABO-incompatible liver allograft had patient survival rates of 70% at 1 year and 60% at 3 years but low graft survival rates (40% and 30% at 1 and 3 years). In a multiple regression analysis, significant independent predictors of poor patient survival were early year of transplantation, ABO-compatible donor, high donor age, and waiting time more than 3 days and less than 9 days.

CONCLUSION

Survival after highly urgent liver transplantation has improved and is comparable to that observed in patients receiving a liver allograft because of chronic liver disease. Patients receiving an ABO-identical donor organ had significantly higher patient survival rates compared with those receiving an ABO-compatible donor liver.

Brain edema in liver failure: basic physiologic principles and management

In patients with severe liver failure, brain edema is a frequent and serious complication that may result in high intracranial pressure and brain damage. This short article focuses on basic physiologic principles that determine water flux across the blood-brain barrier. Using the Starling equation, it is evident that both the osmotic and hydrostatic pressure gradients are imbalanced across the blood-brain barrier in patients with acute liver failure. This combination will tend to favor cerebral capillary water influx to the brain. In contrast, the disequilibration of the Starling forces seems to be less pronounced in patients with cirrhosis because the regulation of cerebral blood flow is preserved and the arterial ammonia concentration is lower compared with that of patients with acute liver failure. Treatments that are known to reverse high intracranial pressure tend to decrease the osmotic pressure gradients across the blood-brain barrier. Recent studies indicate that interventions that restrict cerebral blood flow, such as hyperventilation, hypothermia, and indomethacin, are also efficient in preventing edema and high intracranial pressure, probably by decreasing the transcapillary hydrostatic pressure gradient. In our opinion, it is important to recall that rational fluid therapy, adequate ventilation, and temperature control are of direct importance to controlling cerebral capillary water flux in patients with acute liver failure. These simple interventions should be secured before more advanced experimental technologies are instituted to treat these patients.

Fulminant hepatic failure: outcome after listing for highly urgent liver transplantation-12 years experience in the nordic countries

Fulminant hepatic failure is a common indication for liver transplantation. Outcomes of patients listed for a highly urgent liver transplantation have been studied, with special emphasis on etiology of the liver disease, clinical condition, and ABO blood type. Data have been collected from the Nordic Liver Transplantation Registry. All Nordic patients listed for a highly urgent primary liver transplantation during a 12-year period have been included. Of the 315 patients listed for a highly urgent liver transplantation, 229 (73%) received a first liver allograft, 50 patients (16%) died without transplantation, and 36 patients (11%) were permanently withdrawn and survived. In 43% of the patients, no definite etiology of the liver failure could be established. Paracetamol intoxication was the most frequent specific indication for listing. Patients with blood type A had no significant shorter waiting time (3.8 v 6.6 days; P =.1) but a higher rate of transplantation (82% v 66%, P =.006) as compared with blood type O patients. In a multivariate analysis, paracetamol intoxication remained the single independent predictor of an outcome without transplantation. In conclusion, a high transplantation rate was observed among patients listed for a highly urgent liver transplantation because of fulminant hepatic failure. Blood type O patients had a lower chance of receiving a liver allograft. Patients with paracetamol intoxication had both a higher mortality without transplantation and a higher withdrawal rate attributable to improved condition.

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.

Decreased splanchnic oxygen uptake and increased systemic oxygen uptake in cirrhosis are normalized after liver transplantation

The aim of this study is to (1) characterize the impact of orthotopic liver transplantation (OLT) on splanchnic and systemic oxygen uptake (VO(2)) in patients with liver cirrhosis, and (2) investigate possible influencing factors, as well as metabolic consequences, of reduced splanchnic VO(2) in patients with cirrhosis. Therefore, we measured systemic VO(2) (indirect calorimetry), portal pressure (hepatic venous pressure gradient), hepatic blood flow (HBF; primed continuous infusion of indocyanine green), and hepatic turnover (arteriohepatic venous concentration differences multiplied by HBF) of oxygen, glucose, free fatty acids (FFAs), and aromatic amino acids (AAAs) in 52 patients with advanced cirrhosis and 16 patients with a clinically stable long-term course after OLT. Systemic VO(2) was significantly increased in patients with cirrhosis (261 +/- 7 mL/min) and normalized after OLT (216 +/- 8 mL/min; P < .001). Arterial and hepatic venous oxygen saturation and splanchnic oxygen extraction (in percent) were not different between patients with cirrhosis and after OLT. Splanchnic VO(2) was decreased in patients with cirrhosis (41 +/- 3 mL/min, representing 16% +/- 1% of systemic VO(2)) and normalized after OLT (69 +/- 6 mL/min; P < .001, representing 32% +/- 3% of systemic VO(2); P < .001). In patients with cirrhosis, a decrease in HBF was associated with decreased splanchnic VO(2) (r = 0.74; P < .001). Conversely, decreased splanchnic VO(2) reflected a decrease in hepatic glucose production (r = 0.34; P = .01) and hepatic extraction of FFAs (r = 0.40; P < .01) and AAAs (r = 0.30; P < .05). These results show that (1) splanchnic and systemic VO(2) normalize after OLT, indicating correction of hepatic and extrahepatic metabolic derangements; (2) in cirrhosis, HBF becomes limiting for hepatic oxygen supply; and (3) impaired splanchnic VO(2) reflects a decrease in metabolic liver function.

Liver and intestinal lactate metabolism in patients with acute hepatic failure undergoing liver transplantation

OBJECTIVE

To determine the relative contribution of the gastrointestinal tract and the liver in lactate metabolism in patients with acute liver failure (ALF) and the effect of liver transplantation on this. We hypothesized that the liver and gut are net producers of lactate in ALF and that this is reversed after liver transplantation.

SETTING

A university-affiliated specialist liver transplant operating theater.

SUBJECTS

Eleven patients with ALF undergoing liver transplantation.

MEASUREMENTS AND INTERVENTIONS

After ethical approval, 11 patients with ALF listed for orthotopic hepatic transplantation were studied. Whole blood was analyzed for lactate concentration from radial artery (RA) catheter, portal vein (PV), and hepatic vein (HV) during the dissection phase and was repeated postreperfusion of the liver graft. Gradients across the gut and the liver were calculated to see if there was net production or consumption.

RESULTS

HV lactate was significantly higher than arterial (p =.028) in patients with ALF before liver transplantation, suggesting splanchnic production of lactate. Total splanchnic lactate gradient (HV-RA) is positive in ALF. Both the gut (PV-RA) and the liver (HV-PV) were net producers of lactate. After liver transplantation, hepatic venous lactate falls below arterial levels but not significantly. The gradient across the gut (PV-RA) remained positive, but the transhepatic gradient (HV-PV) became significantly negative, showing consumption by the graft (p =.021). The magnitude of lactate consumption after transplantation correlated positively with portal venous lactate concentration (p =.029) and inversely with graft cold ischemic time (p =.007).

CONCLUSION

The liver is a net producer of lactate in patients with ALF and an elevated whole blood lactate. After liver transplantation, the graft becomes a consumer of lactate as shown by the negative lactate gradient. The degree of consumption is dependent on portal venous lactate concentration and cold ischemic time.

N-acetylcysteine increases cerebral perfusion pressure in pigs with fulminant hepatic failure

OBJECTIVE

Intravenous administration of N-acetylcysteine beyond 15 hrs reduces mortality rates in patients suffering from paracetamol-induced fulminant hepatic failure, although the mechanism of the therapeutic benefit remains unclear. We hypothesized increased survival to be caused by improved hemodynamic performance. The main objective for the study was to explore the effect of N-acetylcysteine on hemodynamics, oxygen transport, and regional blood flow in pigs with fulminant hepatic failure.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Surgical research laboratory in a university hospital.

SUBJECTS

Female Norwegian Landrace pigs.

INTERVENTIONS

Fulminant hepatic failure was induced by a total liver devascularization procedure. Five hours later, the pigs were allocated to N-acetylcysteine treatment (150 mg.kg-1 in 100 mL of 0.9% saline over 15 mins, followed by 50 mg.kg-1 in 500 mL of 0.9% saline over a period of 4 hrs) or placebo.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure stabilized in the N-acetylcysteine group and increased slightly during the last 2 hrs (pGT =.009). Thus, mean arterial pressure was significantly higher compared with placebo after 3 hrs (p =.01). Cerebral perfusion pressure was significantly higher during the last 2 hrs in the N-acetylcysteine group (pGT =.033). Common carotid artery flow also increased and was maintained at a higher level compared with placebo (pG =.027). Systemic vascular resistance index initially decreased but then gradually increased (pGT <.001). Cardiac index increased after 15 mins of N-acetylcysteine infusion, causing a significant interaction (pGT =.038), but did not differ after 3 hrs. No significant differences in hindleg and mesentery hemodynamics were found. A short-lived increase in oxygen delivery caused by a temporary increase in cardiac index was observed but without any corresponding increase in oxygen consumption.

CONCLUSIONS

Intravenous N-acetylcysteine infusion increases cerebral perfusion pressure in pigs with fulminant hepatic failure. Earlier reported effects on oxygen transport and uptake could not be confirmed.

Laboratory assessment of hepatic hemodynamics

Although the study of hepatic circulation is complicated by the dual blood supply and complex anatomy of the liver, many distinct methods are available to facilitate its study. Before embarking on an investigation of hepatic hemodynamics, the investigator must be familiar with the available methods and their applications. All methods have their own attributes and limitations. No one method is superior to the others, but, depending on the aspect of hepatic hemodynamics to be investigated, a particular methodology may yield distinct advantages.

Effects of high-volume plasmapheresis on ammonia, urea, and amino acids in patients with acute liver failure

OBJECTIVE

In acute liver failure (ALF), urea production is severely impaired, and detoxification of ammonia by glutamine synthesis plays an important protective role. The aim of this study was to examine the effects of therapeutic high-volume plasmapheresis (HVP) on arterial concentrations and splanchnic exchange rates of ammonia, urea, and amino acids-in particular, glutamine.

METHODS

A quantity of 8 L of plasma was exchanged over the course of 7 h in 11 patients with ALF after development of hepatic encephalopathy grade III-IV. Splanchnic exchange rates of ammonia, urea, and amino acids were measured by use of liver vein catheterization.

RESULTS

HVP removed ammonia and glutamine at a rate of 1 micromol/min and 27 micromol/min, respectively. Arterial ammonia decreased from 160 +/- 65 to 114 +/- 50 micromol/L (p < 0.001). In contrast, arterial glutamine was only minimally changed from 1791 +/- 1655 to 1764 +/- 1875 micromol/L (NS). This implied that the rate of systemic glutamine synthesis was increased by 27 micromol/min. Splanchnic exchange rates (before vs after HVP) were as follows: for ammonia, -93 +/- 101 versus -70 +/- 80 micromol/min (NS); urea-nitrogen, 0.08 +/- 1.64 versus -0.31 +/- 0.45 mmol/min (NS); alanine, -73 +/- 151 versus 12 +/- 83 micromol/min (p < 0.05); and glutamine: 132 +/- 246 versus 186 +/- 285 micromol/min (NS), with negative values denoting release.

CONCLUSIONS

Arterial ammonia decreased during HVP in patients with ALF. The data suggest that this effect of HVP could be explained by increased hepatic urea synthesis and possibly by increased glutamine synthesis in muscle tissue.

Splanchnic metabolism of fuel substrates in acute liver failure

BACKGROUND/AIMS

This study aimed to characterize the exchange of fuel substrates in the splanchnic circulation in acute liver failure.

METHODS

Liver vein catheterization was used in 22 patients with acute liver failure after development of hepatic encephalopathy grade III-IV Healthy controls, patients with cirrhosis and patients with acute on chronic liver disease were also studied.

RESULTS

In acute liver failure there was splanchnic removal of glucose (0.21+/-0.44 mmol/min), release of lactate (0.34+/-0.37 mmol/min), pyruvate (0.08+/-0.06 mmol/min) and ketone bodies (0.04+/-0.02 mmol/min), while extraction of amino acids and free fatty acids was insignificant. In the acute liver failure group, a normal hepatic venous oxygen saturation (0.69+/-0.12) and normal pyruvate/lactate ratio suggested absence of hypoxia even though the acetoacetate/beta-hydroxybutyrate ratio was decreased. Only in the acute liver failure group did the measured splanchnic oxygen content difference exceed what could be accounted for even by hypothesizing complete oxidation of all extracted blood-borne fuel substrates; oxidation of endogenous substrates may be quantitatively important in this condition.

CONCLUSION

Acute liver failure was associated with a state of accelerated glycolysis in the splanchnic region, leading to release of lactate in the absence of splanchnic hypoxia.

Splanchnic and leg exchange of amino acids and ammonia in acute liver failure

BACKGROUND & AIMS

In patients with acute liver failure, hyperammonemia is associated with cerebral herniation. We examined the splanchnic and leg exchange of amino acids, urea, and ammonia in such patients.

METHODS

Bedside liver vein catheterization was used in 22 patients after development of hepatic encephalopathy grades III-IV. Femoral venous blood was sampled in 7 of these patients.

RESULTS

Arterial amino acid concentration (8.1 +/- 4.1 mmol/L) was increased 4-fold above normal. Glutamine (2.4 +/- 1.8 mmol/L) and alanine (0.57 +/- 0.35 mmol/L) were by far the predominant amino acids exchanged in the splanchnic and leg circulation. In the splanchnic circulation, there was a net uptake of glutamine (241 +/- 353 micromol/min) and ammonia and alanine were released in an almost 1:1 stoichiometry (r(2) = 0.47; P < 0.001). In the leg, ammonia and alanine were removed and glutamine released. The leg ammonia concentration difference was correlated to that of glutamine (r(2) = 0.80; P = 0.008) and alanine (r(2) = 0.67; P = 0.03).

CONCLUSIONS

Splanchnic metabolism of glutamine in combination with decreased hepatic function was responsible for the splanchnic release of ammonia and alanine. These processes were reversed in skeletal muscle. Stimulation of skeletal muscle metabolism of ammonia could be a important target for future treatment of patients with acute liver failure.

Acute liver failure

Worldwide, viral infection is responsible for the majority of cases of acute liver failure, and the presence of co-existing chronic viral hepatitis may increase its severity. The newly described hepatotrophic viruses, hepatitis G virus and transfusion-transmitted virus, are unlikely to be major aetiological agents. In the USA and western Europe drug-induced hepatotoxicity is the most common cause, and most frequently results from acetaminophen. Hepatotoxicity caused by Ecstasy is increasingly important, particularly in young adults. Hepatic encephalopathy and cerebral oedema remain important and life-threatening complications, and their pathogenesis is not completely understood. The effects of the cerebral metabolism of the high levels of ammonia that circulate in hepatic failure appear to be important. Induced hypothermia is a promising modality of treatment for refractory cerebral oedema, but the only form of treatment known to improve survival is emergency liver transplantation. Living donor and auxiliary liver transplantation are likely to improve survival rates further and reduce the number of patients requiring long-term post-transplant immunosuppression.

Cerebral perfusion, cardiac output, and arterial pressure in patients with fulminant hepatic failure

OBJECTIVE

To evaluate whether changes in cardiac output influence cerebral perfusion directly. In fulminant hepatic failure, the circulation is characterized by wide variations in cardiac output and cerebral blood flow (CBF).

DESIGN

A retrospective, interindividual analysis of CBF and cardiac output (part 1) and a prospective evaluation of cerebral perfusion, cardiac output, and arterial pressure during norepinephrine infusion (part 2).

SETTING

A four-bed specialist liver failure unit.

PATIENTS AND INTERVENTIONS

Twenty patients with fulminant hepatic failure (median age, 43 yrs; range, 17-54; 13 women) maintained on mechanical ventilation (Paco2, 33 torr [4.40 kPa]; range, 26-36 torr [3.47-4.80 kPa) after development of hepatic encephalopathy, stages 3 to 4, had mean arterial pressure (MAP) and cardiac output determined by radial and pulmonary artery catheters. Cerebral perfusion was measured by the 133Xenon clearance technique (n = 8) and by transcranial Doppler sonography, which was used to measure mean flow velocity (Vmean). CBF and Vmean in patients with high cardiac output (>9 L/min) were compared with those with normal or low cardiac output. In the second part of the study, cerebral autoregulation was evaluated by concomitant measurement of Vmean, cardiac output, and MAP during norepinephrine infusion in nine patients.

MEASUREMENTS AND MAIN RESULTS

Median cardiac output was 8.5 L/min (range, 3.2-17.3), CBF was 33 mL/100 g/min (12-77 g/min), and Vmean was 45 cm/sec (22-65 cm/sec). In patients with elevated cardiac output, MAP, Vmean, and CBF were similar compared with patients with normal cardiac output. Neither CBF nor Vmean correlated to cardiac output. During norepinephrine infusion, Vmean increased from 49 cm/sec (34-69 cm/sec) to 63 cm/sec (58-90 cm/sec; p < .05), as MAP increased from 75 mm Hg (54-105 mm Hg) to 97 mm Hg (90-128 mm Hg). On average, cardiac output remained unchanged at 5.7 L/min (range, 3.2-17.3), as it increased in five patients and decreased in four patients. The change in Vmean was related to MAP (r2 = .76; p < .01) but not to cardiac output (r2 = .01).

CONCLUSION

This study shows that CBF correlates to arterial pressure rather than to cardiac output in patients with fulminant hepatic failure. The presence of pressure-passive cerebral circulation stresses the importance of strict cardiovascular control in securing continuous and sufficient cerebral oxygenation and in avoiding the development of cerebral hyperemia and cerebral edema.

Plasma phospholipid fatty acid pattern in severe liver disease

BACKGROUND/AIMS

In acute liver failure the liver has to regenerate, which may increase the consumption of essential fatty acids. Nutritional support consists mainly of infusion of glucose. It is therefore possible that essential fatty acid deficiency may develop in such patients.

METHODS

Plasma phospholipid composition was studied in healthy controls (n=11), in patients with acute liver failure, (n=10), in patients with stable cirrhosis (n=7), and in patients with acute on chronic liver disease with hepatic encephalopathy (n=6). The influence of 2 days of fat-free diet followed by infusion of glucose was studied in five healthy controls.

RESULTS

The ratio between the sums of nonessential/ essential fatty acids, (n-7+n-9)/(n-3+n-6), was higher in patients with acute liver failure (0.73+/-0.17) compared to healthy controls (0.35+/-0.06, p<0.001). The ratio was also higher in patients with acute on chronic liver disease (1.11+/-0.39) compared to patients with cirrhosis (0.61+/-0.18, p<0.01). These differences were mainly due to low levels of linoleic acid and high levels of oleic acid in the patients with acute liver failure and acute on chronic liver disease. Two days of fat-free diet followed by infusion of glucose did not change this ratio (0.40+/-0.04 vs. 0.47+/-0.05, NS) in healthy controls. The essential fatty acid deficiency indicator eicosatrienoic acid was detectable in 2 out of 11 controls, in 5/10 with acute liver failure, in 7/7 with cirrhosis, and in 6/7 with acute on chronic liver disease.

CONCLUSION

Acute severe deterioration of liver function was associated with changes in the fatty acid composition of plasma phospholipids suggestive of essential fatty acid deficiency.

Interpretation of simultaneous measurements of hepatic extraction fractions of indocyanine green and sorbitol: evidence of hepatic shunts and capillarization?

Sorbitol and indocyanine green (ICG) have high hepatic extraction fractions (E(sorb) and E(ICG)) in normal subjects. A curved relationship has been observed between E(sorb) and E(ICG) in liver disease. According to one interpretation, the decrease of E(sorb) is a result of intrahepatic shunting and 1 - E(sorb) is the fraction of shunted flow (the shunt hypothesis). Under the further assumption that capillarization of functioning sinusoids prevents hepatic uptake of plasma protein-bound ICG and allows uptake of water-soluble sorbitol, the difference E(sorb) - E(ICG) has been suggested as a measure of capillarization. We propose an alternative hypothesis: that the sinusoidal permeability-surface area products for sorbitol and ICG are reduced in proportion by liver disease (proportional reduction hypothesis). Based on the sinusoidal perfusion model, predictions were produced from both hypotheses for the relation between E(sorb) and E(ICG) and the additional effects of capillarization were described. By use of liver vein catheterization, E(sorb) and E(ICG) were simultaneously measured during continuous infusions in 53 human subjects with varying degrees of liver disease. The data were in better agreement with the predictions of the proportional reduction hypothesis than with the shunt hypothesis. Even though both intrahepatic portosystemic shunts and sinusoidal capillarization are known to occur in cirrhosis and also may have influenced our data, they appeared to be of minor importance from a kinetic point of view. These findings favor the proportional reduction hypothesis and do not support the use of systemic nonrenal clearance of sorbitol as a measure of "functional liver blood flow."

Cerebral herniation in patients with acute liver failure is correlated with arterial ammonia concentration

Cerebral edema leading to cerebral herniation (CH) is a common cause of death in acute liver failure (ALF). Animal studies have related ammonia with this complication. During liver failure, hepatic ammonia removal can be expected to determine the arterial ammonia level. In patients with ALF, we examined the hypotheses that high arterial ammonia is related to later death by CH, and that impaired removal in the hepatic circulation is related to high arterial ammonia. Twenty-two patients with ALF were studied retrospectively. In addition, prospective studies with liver vein catheterization were performed after development of hepatic encephalopathy (HE) in 22 patients with ALF and 9 with acute on chronic liver disease (AOCLD). Cerebral arterial-venous ammonia difference was studied in 13 patients with ALF. In all patients with ALF (n = 44), those who developed CH (n = 14) had higher arterial plasma ammonia than the non-CH (n = 30) patients (230 +/- 58 vs. 118 +/- 48 micromol/L; P <. 001). In contrast, galactose elimination capacity, bilirubin, creatinine, and prothrombin time were not different (NS). Cerebral arterial-venous differences increased with increasing arterial ammonia (P <.001). Arterial plasma ammonia was lower than hepatic venous in ALF (148 +/- 73 vs. 203 +/- 108 micromol/L; P <.001). In contrast, arterial plasma ammonia was higher than hepatic venous in patients with AOCLD (91 +/- 26 vs. 66 +/- 18 micromol/L; P <.05). Net ammonia release from the hepatic-splanchnic region was 6.5 +/- 6. 4 mmol/h in ALF, and arterial ammonia increased with increasing release. In contrast, there was a net hepatic-splanchnic removal of ammonia (2.8 +/- 3.3 mmol/h) in patients with AOCLD. We interpret these data that in ALF in humans, vast amounts of ammonia escape hepatic metabolism, leading to high arterial ammonia concentrations, which in turn is associated with increased cerebral ammonia uptake and CH.