Brain dysfunction in fulminant hepatic failure

Pathogenic functions of host microbiota

BACKGROUND

It is becoming evident that certain features of human microbiota, encoded by distinct autochthonous taxa, promote disease. As a result, borders between the so-called opportunistic pathogens, pathobionts, and commensals are increasingly blurred, and specific targets for manipulating microbiota to improve host health are becoming elusive.

RESULTS

In this study, we focus on the functions of host bacterial communities that have the potential to cause disease, proposing the term "pathogenic function (pathofunction)". The concept is presented via three distinct examples, namely, the formation of (i) trimethylamine, (ii) secondary bile acids, and (iii) hydrogen sulfide, which represent metabolites of the gut microbiota linked to the development of non-communicable diseases. Using publicly available metagenomic and metatranscriptomic data (n = 2975), we quantified those pathofunctions in health and disease and exposed the key players. Pathofunctions were ubiquitously present with increased abundances in patient groups. Overall, the three pathofunctions were detected at low mean concentrations (< 1% of total bacteria carried respective genes) and encompassed various taxa, including uncultured members.

CONCLUSIONS

We outline how this function-centric approach, where all members of a community exhibiting a particular pathofunction are redundant, can contribute to risk assessment and the development of precision treatment directing gut microbiota to increase host health.

Comparison of Porcine Hepatocytes with Human Hepatoma (C3A) Cells for Use in a Bioartificial Liver Support System

Cells from primary porcine hepatocytes (PPH) and the immortalized human hepatoma cell line C3A are both used in bioartificial liver support systems (BALSS). In this work the viability and metabolic capacity of PPH and C3A cells cultured in different media were compared. Also, because the cells come into direct or indirect contact with human blood components in BALSS, the effects of human complement on survival and functions of the cells was evaluated. For short-term culture, maintenance of PPH viability was essential for retention of P450IA1 activity ( r = 0.882, p < 0.01) and effective ammonia clearance ( r = −0.791, p < 0.01). When cell viability was below 60% P450IA1 activity could not be recorded and nitrogen elimination activity significantly diminished. In contrast to PPH, ammonia levels were markedly increased for C3A cells in all culture media tested ( p < 0.01). Ammonia increase correlated with C3A viability ( r = 0.896, p < 0.05). PPH metabolic function was superior to that of the C3A cell line when evaluated by P450IA1 activity, ammonia removal, and amino acid metabolism. When PPH were incubated in human plasma (HP) or human serum (HS) there was rapid and irreversible deterioration of viability occurring within 9 h. This toxic effect could be prevented by the inactivation of complement. When sodium citrate dissolved in dextrose was added to medium, there was considerable damage to both PPH and the C3A cell line. However, there was no demonstrable toxic effect when hepatic cells of either type were exposed to heparin. We conclude that PPH cultivated in complement-inactivated HP or HS are to be preferred to C3A for clinical application of BALSS, and that heparin should be preferred for anticoagulation in BALSS. © 1998 Elsevier Science Inc.

Hyperammonemia: What Urea-lly Need to Know: Case Report of Severe Noncirrhotic Hyperammonemic Encephalopathy and Review of the Literature

Purpose. A 66-year-old man who presented with coma was found to have isolated severe hyperammonemia and diagnosed with a late-onset urea-cycle disorder. He was treated successfully and had full recovery. Methods. We report a novel case of noncirrhotic hyperammonemia and review the literature on this topic. Selected literature for review included English-language articles concerning hyperammonemia using the search terms “hyperammonemic encephalopathy”, “non-cirrhotic encephalopathy”, “hepatic encephalopathy”, “urea-cycle disorders”, “ornithine transcarbamylase (OTC) deficiency”, and “fulminant hepatic failure”. Results. A unique case of isolated hyperammonemia diagnosed as late-onset OTC deficiency is presented. Existing evidence about hyperammonemia is organized to address pathophysiology, clinical presentation, diagnosis, and treatment. The case report is discussed in context of the reviewed literature. Conclusion. Late-onset OTC deficiency presenting with severe hyperammonemic encephalopathy and extensive imaging correlate can be fully reversible if recognized promptly and treated aggressively.

Cerebral pulsatility index by transcranial Doppler sonography predicts the prognosis of patients with fulminant hepatic failure

AIM

Cerebral hemodynamic derangement is well known in patients with fulminant hepatic failure. The advent of transcranial Doppler sonography (TCD) enabled noninvasive observation of cerebral hemodynamics. To evaluate its clinical usefulness, we examined longitudinal cerebral hemodynamic parameters in patients with fulminant hepatic failure and severe acute hepatitis.

METHODS

The six subjects were four patients with fulminant hepatic failure, one with severe acute hepatitis and one with severe acute exacerbation on chronic hepatitis. The pulsatility indices of the right middle cerebral artery were used as parameters of cerebral hemodynamics.

RESULTS

The pulsatility indices of the two patients with a deteriorating course had elevated to >1.00, whereas those of the two patients undergoing recovery were within normal limits, as well as of the patients with acute hepatitis or acute exacerbation on chronic hepatitis.

CONCLUSION

Cerebral pulsatility measured by TCD may be a real-time and useful tool to assess and monitor patients with fulminant hepatic failure.

Establishment of a non-human primate model of acute liver failure

AIM: To establish a non-human primate model of acute liver failure (ALF).

METHODS: Fifteen healthy cynomolgus monkeys (Macaca fascicularis) were randomly divided into three groups, which were administered with D-galactosamine via the jugular vein at doses of 0.45 (high-dose group), 0.3 (medium-dose group) and 0.15 g/kg (low-dose group), respectively, to induce ALF. At 0, 12, 24, 36, 48, 60, 72 and 96 h after administration, clinical and intracranial pressure (ICP) data were recorded, and blood samples were collected for measurement of alanine aminotransferase (ALT), prothrombin time (PT), total bilirubin (TBIL), and ammonia (NH3). Animal survival time was recorded to compare the survival rates among the three groups. Postmortem examination was performed in dead cynomolgus monkeys.

RESULTS: All animals were dead in the high- and medium-dose groups, and the mean survival time was 56.1 h ± 8.1 h and 109.8 h ± 11.2 h, respectively. Only one animal died at 98 h after treatment in the low-dose group. In the high- and medium-dose groups, serum levels of ALT, PT, TBIL and NH3, and ICP were significantly higher at all time points than at baseline (0 h) (all P < 0.05). All these parameters were normal at 60 h in the low-dose group. Inflammatory cell infiltration and hepatic cell necrosis were observed in dead cynomolgus monkeys.

CONCLUSION: A cynomolgus monkey model of AHF has been successfully established and can be used for future ALF research.

An experimental animal model of fulminant hepatic failure in pigs

The objective of this study was to develop an experimental animal model of fulminant hepatic failure to test the efficacy of the bioartificial liver system. The portal vein and the hepatic artery were clamped intermittently and then the hepatic artery was ligated (ligation group, n=5). Pigs whose hepatic arteries were not ligated after clamping were assigned to the non-ligation group (n=5). The biochemical changes in blood, histologic alterations of the liver and neurologic examination for pigs were checked up. All animals died within 17 hr in the ligation group. On the other hand, all animals survived more than 7 days in the non-ligation group. In the ligation group, the levels of ammonia, lactic acid and creatinine showed a progressively increasing pattern. Prothrombin time was also prolonged gradually. Cytoplasmic condensation and nuclear pyknosis of hepatocytes were detected histologically at autopsy. Neurologic findings such as decreased pain sensation, tachypnea and no light reflex of pupils were observed. The findings shown in the ligation group are similar to the clinical features of fulminant hepatic failure in human and this animal model is reproducible. Therefore, this can be a suitable animal model to evaluate the efficacy of the bioartificial liver system for treating fulminant hepatic failure.

Development of a percutaneous fiberoptic hepatic venous localization catheter

OBJECTIVE

To develop a liver-specific biosensor system/catheter assembly that can be used to localize and cannulate the hepatic venous system without the need for fluoroscopic imaging. This would permit the bedside placement of a hepatic venous catheter for monitoring purposes without radiographic guidance.

DESIGN

Experimental, in vitro.

STUDY SETTING

Experimental laboratory at a university center.

SUBJECT

This was a simulation study to evaluate the ability of a cardiovascular monitoring catheter mounted with a liver-specific biosensor to anatomically identify a side arm tributary. The experimental system used for this study mimics the hepatic vein draining into the inferior vena cava and allows its localization without the need for assisted imaging. The biosensor design and catheter/sensor assembly function were studied in this in vitro model.

INTERVENTIONS

A liver-specific biosensor was developed by housing a homogeneous affinity fluorescence assay system sensitive to galactose in a microdialysis hollow fiber receptacle. A polyvinyl chloride tube containing a side arm was constructed to mimic the confluence of a venous tributary (i.e., the hepatic vein) with a major vascular channel (i.e., the vena cava). In this simulation, the side arm was continuously perfused with a liver-sensitive analyte (galactose) and the main channel was perfused with galactose-free buffer. A cardiovascular catheter containing a fiberoptic waveguide mounted with a galactose-sensitive fluorescent probe was advanced along the main conduit to assess its ability to identify the location of the galactose side arm infusion site.

MEASUREMENTS AND MAIN RESULTS

The response of the fiberoptic sensor to different galactose concentrations was assessed and found to be almost linear over the concentration range of 0 to 2 mM, which encompasses the expected utilization range of this system. The variability in identifying the galactose infusion point (simulated hepatic vein) in a 15-cm conduit was 1.7 to 2.8 mm, or 1.1% to 1.9%.

CONCLUSIONS

The construction of a catheter/sensor system with the ability to provide accurate spatial/anatomical localization data for the hepatic venous system is feasible. This assembly will eliminate the need for ancillary imaging systems for catheter/sensor delivery to an individual organ system and potentially can be positioned at the bedside in a fashion similar to the pulmonary artery flotation catheter.

An improved model of galactosamine-induced fulminant hepatic failure in the pig

Fulminant hepatic failure is a serious condition with very high mortality. Development of new therapies designed to bridge the patient through the acute period of their disease has been hampered by the lack of a large animal model that closely reproduces the changes in humans. We have established an improved model of fulminant hepatic failure in the pig by administration of an aminosugar d-galactosamine hydrochloride. Galactosamine in a dose of 1.0 g/kg was dissolved in 5% dextrose in water (D5W) and given intravenously to seven young pigs weighing 8 to 15 kg. Seven control pigs received an equal volume of D5W alone. Two days prior to injection, a baseline ultrasound-guided liver biopsy was done in each pig under general anesthesia using isofluorane. Clinical data were recorded and blood for laboratory determinations was drawn at 0 h (baseline), 24 h, 48 h, and 72 h after infusion of galactosamine or D5W alone, under general anesthesia. Neurological data were recorded at the same intervals before inducing anesthesia. Galactosamine-treated animals showed 100% mortality. All of them died by 86 h after injection of galactosamine, with death resulting from fulminant hepatic failure characterized by marked increases in total bilirubin, liver enzymes, ammonia, and lactate; associated coagulopathy; hypoglycemia; and coma. Liver histology showed massive hepatocellular necrosis in all seven galactosamine-treated animals. This large and highly reproducible animal model appears promising for future evaluation of bioartificial liver support systems designed to treat fulminant hepatic failure in humans.

Outcome of children with cerebral edema caused by fulminant hepatic failure

Mortality is high in patients with fulminant hepatic failure (FHF). Neurologic complications of encephalopathy and cerebral edema are major contributors to mortality. Orthotopic liver transplantation has improved survival in these patients. However, the complexity of medical and surgical problems in this patient population, coupled with a severe shortage of organs, requires careful patient selection. The aim of this study was to describe the neurologic outcome of children with FHF who developed radiologically apparent cerebral edema. The hospital and outpatient records and radiologic studies of 20 children with FHF admitted to Children's Hospital of Pittsburgh from 1981-1995 who developed encephalopathy and computed tomographic evidence of cerebral edema were reviewed. Fourteen patients died (70%), three were left with severe neurologic deficits (15%), and three were left with moderate deficits (15%). Survival was correlated with a lesser degree of coma. Histopathologic examination of eight brains demonstrated cerebral edema and widespread ischemic neuronal necrosis in all eight. The presence of radiographic cerebral edema in children with FHF is an objective measure that indicates a very poor prognosis. Termination of care is a reasonable option. Comprehensive monitoring of cerebral function and intracranial pressure is required in children with FHF. Orthotopic liver transplantation should be performed in children with severe and worsening encephalopathy before the development of radiographically apparent cerebral edema.

The effects of ammonia and portal-systemic shunting on brain metabolism, neurotransmission and intracranial hypertension in hyperammonaemia-induced encephalopathy

BACKGROUND/AIMS

The pathogenetic factors contributing to encephalopathy in portacaval shunted rats with hyperammonaemia were studied.

METHODS

Hyperammonaemia was induced by ammonium-acetate infusions in portacaval shunted rats (2.8 mmol.kg bw-1.h-1; AI-portacaval shunted rats) and in sham-portacaval shunted rats (6.5 mmol.kg bw-1.h-1; AI-NORM rats). Severity of encephalopathy was quantified by clinical grading and EEG spectral analysis. Changes in brain metabolites were assessed by amino acid analysis of brain cortex homogenates, whereas changes in amino acids with neurotransmitter activity were assessed in cerebrospinal fluid; brain water content was measured by subtracting dry from wet brain weights and intracranial pressure was measured by a pressure transducer connected to a cisterna magna cannula.

RESULTS

Although similar increased blood and brain ammonia concentrations were obtained in both experimental groups, only AI-portacaval shunted rats developed encephalopathy, associated with a significant increase in intracranial pressure. Other significant differences were: higher concentrations of brain glutamine and aromatic amino acids, higher concentrations of cerebrospinal fluid glutamine, aromatic amino acids, glutamate and aspartate in AI-portacaval shunted rats than in AI-NORM rats.

CONCLUSIONS

These results indicate that hyperammonaemia alone dose not induce encephalopathy, whereas portal-systemic shunting adds an essential contribution to the pathogenesis of encephalopathy. It is hypothesised that the larger increase in brain glutamine in AI-portacaval shunted rats than in AI-NORM rats is responsible for increased brain concentrations of aromatic amino acids, for cell swelling and for extracellular release of glutamate and aspartate. This might promote encephalopathy. If cell swelling is not restricted, intracranial hypertension will develop.

Functional loss of cerebral blood flow autoregulation in patients with fulminant hepatic failure

In management of patients with fulminant hepatic failure, it is recommended that mean arterial pressure should be raised if cerebral perfusion pressure is lower than 50 mmHg, but the influence of such therapy on cerebral blood flow is unknown. We examined cerebral blood flow autoregulation in seven consecutive patients with fulminant hepatic failure during treatment of imminent insufficient cerebral perfusion pressure. Cerebral perfusion was evaluated by transcranial Doppler assessed mean flow velocity in the middle cerebral artery and by the arterio-venous difference for oxygen. Intracranial pressure was recorded by a subdural transducer and cerebral perfusion pressure calculated as the difference between mean arterial pressure and intracranial pressure. After 20 (range 10 to 43) min, mean arterial pressure was raised from 74 (43-80) to 94 (76-114) mmHg by i.v. noradrenaline, cerebral perfusion pressure increased from 49 (26-75) to 82 (50-108) mmHg (p < 0.01) as the intracranial pressure remained unchanged at 26 (3-35) mmHg. The mean flow veolocity increased from 68 (30-134) to 108 (48-168) cm s-1 and the arterio-venous difference for oxygen by 46 (10-82)% (p < 0.05). Both mean flow velocity (r = 0.63) and arterio-venous difference for oxygen (r = 0.71) were correlated to mean arterial pressure (p < 0.001), and a lower blood pressure limit of autoregulation could not be identified in any of the patients. These data suggest that the cerebral blood flow is not autoregulated in patients with fulminant hepatic failure and therefore cerebral blood flow should be "clamped" within the normal physiologic range by manipulation of arterial blood pressure in order to avoid cerebral hypoxia and/or hypertensive induced cerebral oedema.