Medical therapy of brain edema in fulminant hepatic failure

Neuroglia in hepatic encephalopathy

Neuroglia contribute to the pathophysiology of hepatic encephalopathy (HE) either beneficially or detrimentally. Pathogenesis of HE is linked to damage triggered by blood-derived toxins, with ammonia being the main causative factor. Neuroglial cells, especially astrocytes and microglia, respond to HE-associated systemic and central signals and undergo complex and variable changes in their metabolism, morphology, and function, which include ion and water dyshomeostasis in conjunction with neurotransmission imbalance and neuroinflammation. HE-induced alterations of astrocytes are defined as astrocytopathy, with aberrant astrocytes resulting in either gain or loss of functions. In the chronic HE, the presence of Alzheimer type II cells is a histologic hallmark, with asthenic astrocytes emerging as a newcomer. In acute HE, rapid swelling of astrocytes is a primary cause of cerebral edema and mortality. This chapter reviews the dominant role of astrocytes in the pathogenesis of HE resulting from acute and chronic liver failure, mainly in experimental models. The focus is on the loss of homeostatic function bearing upon the functioning of the glymphatic system, aberrant neurotransmission as a consequence of astrocyte-neuron miscommunication, and the concordant neuroinflammatory response of astrocytes and microglia. The chapter concludes with a delineation of concepts for future research.

Clinical and Neurologic Outcomes in Acetaminophen-Induced Acute Liver Failure: A 21-Year Multicenter Cohort Study

BACKGROUND & AIMS

Acetaminophen (APAP)-induced acute liver failure (ALF) is a rare disease associated with high mortality rates. This study aimed to evaluate changes in interventions, psychosocial profile, and clinical outcomes over a 21-year period using data from the ALF Study Group registry.

METHODS

A retrospective review of this prospective, multicenter cohort study of all APAP-ALF patients enrolled during the study period (1998-2018) was completed. Primary outcomes evaluated were the 21-day transplant-free survival (TFS) and neurologic complications. Covariates evaluated included enrollment cohort (early, 1998-2007; recent, 2008-2018), intentionality, psychiatric comorbidity, and use of organ support including continuous renal replacement therapy (CRRT).

RESULTS

Of 1190 APAP-ALF patients, recent cohort patients (n = 608) had significantly improved TFS (recent, 69.8% vs early, 61.7%; P = .005). Recent cohort patients were more likely to receive CRRT (22.2% vs 7.6%; P < .001), and less likely to develop intracranial hypertension (29.9% vs 51.5%; P < .001) or die by day 21 from cerebral edema (4.5% vs 11.6%; P < .001). Grouped by TFS status (non-TFS, n = 365 vs TFS, n = 704), there were no differences in psychiatric comorbidity (51.5% vs 55.0%; P = .28) or intentionality (intentional, 39.7% vs 41.6%; P = .58). On multivariable logistic regression adjusting for vasopressor support, development of grade 3/4 hepatic encephalopathy, King's College criteria, and MELD score, the use of CRRT (odds ratio, 1.62; P = .023) was associated with significantly increased TFS (c-statistic, 0.86). In a second model adjusting for the same covariates, recent enrollment was associated significantly with TFS (odds ratio, 1.42; P = .034; c-statistic, 0.86).

CONCLUSIONS

TFS in APAP-ALF has improved in recent years and rates of intracranial hypertension/cerebral edema have decreased, possibly related to increased CRRT use.

Acute liver failure: A review for emergency physicians

INTRODUCTION

Acute liver failure (ALF) remains a high-risk clinical presentation, and many patients require emergency department (ED) management for complications and stabilization.

OBJECTIVE

This narrative review provides an evidence-based summary of the current data for the emergency medicine evaluation and management of ALF.

DISCUSSION

While ALF remains a rare clinical presentation, surveillance data suggest an overall incidence between 1 and 6 cases per million people every year, accounting for 6% of liver-related deaths and 7% of orthotopic liver transplants (OLT) in the U.S. The definition of ALF includes neurologic dysfunction, an international normalized ratio ≥ 1.5, no prior evidence of liver disease, and a disease course of ≤26 weeks, and can be further divided into hyperacute, acute, and subacute presentations. There are many underlying etiologies, including acetaminophen toxicity, drug induced liver injury, and hepatitis. Emergency physicians will be faced with several complications, including encephalopathy, coagulopathy, infectious processes, renal injury, and hemodynamic instability. Critical patients should be evaluated in the resuscitation bay, and consultation with the transplant team for appropriate patients improves patient outcomes. This review provides several guiding principles for management of acute complications. Using a pathophysiological-guided approach to the management of ALF associated complications is essential to optimizing patient care.

CONCLUSIONS

ALF remains a rare clinical presentation, but has significant morbidity and mortality. Physicians must rapidly diagnose these patients while evaluating for other diseases and complications. Early consultation with a transplantation center is imperative, as is identifying the underlying etiology and initiating symptomatic care.

Pathogenesis of hepatic encephalopathy: role of ammonia and systemic inflammation

The syndrome we refer to as Hepatic Encephalopathy (HE) was first characterized by a team of Nobel Prize winning physiologists led by Pavlov and Nencki at the Imperial Institute of Experimental Medicine in Russia in the 1890's. This focused upon the key observation that performing a portocaval shunt, which bypassed nitrogen-rich blood away from the liver, induced elevated blood and brain ammonia concentrations in association with profound neurobehavioral changes. There exists however a spectrum of metabolic encephalopathies attributable to a variety (or even absence) of liver hepatocellular dysfunctions and it is this spectrum rather than a single disease entity that has come to be defined as HE. Differences in the underlying pathophysiology, treatment responses and outcomes can therefore be highly variable between acute and chronic HE. The term also fails to articulate quite how systemic the syndrome of HE can be and how it can be influenced by the gastrointestinal, renal, nervous, or immune systems without any change in background liver function. The pathogenesis of HE therefore encapsulates a complex network of interdependent organ systems which as yet remain poorly characterized. There is nonetheless a growing recognition that there is a complex but influential synergistic relationship between ammonia, inflammation (sterile and non-sterile) and oxidative stress in the pathogenesis HE which develops in an environment of functional immunoparesis in patients with liver dysfunction. Therapeutic strategies are thus moving further away from the traditional specialty of hepatology and more towards novel immune and inflammatory targets which will be discussed in this review.

Pathophysiology of cerebral oedema in acute liver failure

Cerebral oedema is a devastating consequence of acute liver failure (ALF) and may be associated with the development of intracranial hypertension and death. In ALF, some patients may develop cerebral oedema and increased intracranial pressure but progression to life-threatening intracranial hypertension is less frequent than previously described, complicating less than one third of cases who have proceeded to coma since the advent of improved clinical care. The rapid onset of encephalopathy may be dramatic with the development of asterixis, delirium, seizures and coma. Cytotoxic and vasogenic oedema mechanisms have been implicated with a preponderance of experimental data favouring a cytotoxic mechanism. Astrocyte swelling is the most consistent neuropathological finding in humans with ALF and ammonia plays a definitive role in the development of cytotoxic brain oedema. The mechanism(s) by which ammonia induces astrocyte swelling remains unclear but glutamine accumulation within astrocytes has led to the osmolyte hypothesis. Current evidence also supports an alternate ‘Trojan horse’ hypothesis, with glutamine as a carrier of ammonia into mitochondria, where its accumulation results in oxidative stress, energy failure and ultimately astrocyte swelling. Although a complete breakdown of the blood-brain barrier is not evident in human ALF, increased permeation to water and other small molecules such as ammonia has been demonstrated resulting from subtle alterations in the protein composition of paracellular tight junctions. At present, there is no fully efficacious therapy for cerebral oedema other than liver transplantation and this reflects our incomplete knowledge of the precise mechanisms underlying this process which remain largely unknown.

Lessons from look-back in acute liver failure? A single centre experience of 3300 patients

BACKGROUND & AIMS

Acute liver failure (ALF) is a rapidly progressive critical illness with high mortality. Complex intensive care unit (ICU) protocols and emergency liver transplantation (ELT) are now often available, but rarity and severity of illness have limited its study and evidence-base for care. We reviewed patients treated over a 35-year period at a specialist high-volume ICU, quantifying changes in disease aetiology, severity and evolution of ICU support and ELT use and outcome.

METHODS

Review of adult patients admitted during the period 1973-2008, with acute liver dysfunction and coagulopathy with overt hepatic encephalopathy (ALF) and those without (acute liver injury; ALI).

RESULTS

3305 patients fulfilled inclusion criteria, 2095 with ALF. Overall hospital survival increased from 30% in 1973-78 to 76% in 2004-08; in ALF from 17% to 62% (both p<0.0001). In ALF patients treated without ELT, survival rose from 17% to 48% (p<0.0001); in those undergoing ELT (n=387) from 56% in 1984-88 to 86% in 2004-08 (p<0.01). Coincident with drug sales-restriction, paracetamol-related admissions fell significantly. Viral admissions fell from 56% to 17% of non-paracetamol cases (p<0.0001). Admission markers of liver injury severity fell significantly and the proportion of patients with intracranial hypertension (ICH) fell from 76% in 1984-88 to 20% in 2004-08 (p<0.0001). In those with ICH, mortality fell from 95% to 55% (p<0.0001).

CONCLUSIONS

The nature and outcome of ALF have transformed over 35 years, with major improvements in survival and a fall in prevalence of cerebral oedema and ICH, likely consequent upon earlier illness recognition, improved ICU care, and use of ELT.

Profiling the impact of medium formulation on morphology and functionality of primary hepatocytes in vitro

The characterization of fully-defined in vitro hepatic culture systems requires testing of functional and morphological variables to obtain the optimal trophic support, particularly for cell therapeutics including bioartificial liver systems (BALs). Using serum-free fully-defined culture medium formulations, we measured synthetic, detoxification and metabolic variables of primary porcine hepatocytes (PPHs)--integrated these datasets using a defined scoring system and correlated this hepatocyte biological activity index (HBAI) with morphological parameters. Hepatic-specific functions exceeded those of both primary human hepatocytes (PHHs) and HepaRG cells, whilst retaining biotransformation potential and in vivo-like ultrastructural morphology, suggesting PPHs as a potential surrogate for PHHs in various biotech applications. The HBAI permits assessment of global functional capacity allowing the rational choice of optimal trophic support for a defined operational task (including BALs, hepatocellular transplantation, and cytochrome P450 (CYP450) drug metabolism studies), mitigates risk associated with sub-optimal culture systems, and reduces time and cost of research and therapeutic applications.

Pravastatin for thioacetamide-induced hepatic failure and encephalopathy

BACKGROUND

Nitric oxide (NO) inhibition aggravates hepatic damage and encephalopathy and increases mortality in rats with thioacetamide (TAA)-induced acute liver failure. Statins enhance NO production but whether they influence the above parameters are unknown.

MATERIAL AND METHODS

Male Sprague-Dawley rats were used. In the first series, TAA (350 mg/kg per day, i.p. for 3 days) was administered to induce acute liver failure. Control rats received saline. Rats received distilled water or pravastatin (20 mg/kg per day, p.o.) from 2 days before to 3 days after TAA or saline injection. In the second series, liver cirrhosis was induced by common bile duct ligation (BDL). Sham-operated rats served as controls. Rats received distilled water or pravastatin for 5 or 14 days until the 42nd day after operation. On the last day of treatment, survival, motor activities, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, ammonia and brain histology were evaluated.

RESULTS

Thioacetamide and BDL rats showed higher ALT, AST, bilirubin and ammonia levels and lower motor activity counts compared with their corresponding control groups. In TAA rats, pravastatin elicited higher total and ambulatory motor activity counts and lower AST and total bilirubin levels. Survival was improved, whereas brain H&E staining was not significantly different in TAA rats with or without pravastatin treatment. In BDL groups, rats with or without pravastatin treatment were not different in motor activity counts and liver biochemistry.

CONCLUSIONS

Pravastatin ameliorates hepatic encephalopathy and liver biochemistry and improves survival in rats with acute liver failure, but not in those with cirrhosis.

Thioacetamide-induced fulminant hepatic failure induces cerebral mitochondrial dysfunction by altering the electron transport chain complexes

Fulminant hepatic failure (FHF) is an acute form of hepatic encephalopathy resulting from severe inflammatory or necrotic liver damage without any previously established liver damage. This develops as a complication due to viral infections, and drug abuse. FHF also occurs in acute disorders like Reye's syndrome. Although the exact mechanisms in the etiology of FHF are not understood, elevated levels of brain ammonia have been consistently reported. Such increased ammonia levels are suggested to alter neurotransmission signals and impair cerebral energy metabolism due to mitochondrial dysfunctions. In the present study we have examined the role of cerebral electron transport chain complexes, including complex I, II, III IV, and pyruvate dehydrogenase in the non-synaptic mitochondria isolated from the cortex of the thioacetamide-induced FHF rats. Further, we have examined if the structure of mitochondria is altered. The results of the current study demonstrated a decrease in the activity of the complex I by 31 and 48% at 18 and 24 h respectively after the thioacetamide injection. Similarly, the activity of electron transport chain complex III was inhibited by 35 and 52% respectively, at 18 and 24 h, respectively. The complex II and complex IV, on the other hand, revealed unaltered activity. Further the activity of pyruvate dehydrogenase at 18 and 24 h after the induction of FHF was inhibited by 29 and 43%, respectively. Our results also suggest mitochondrial swelling in FHF induced rats. The inhibition of the respiratory complexes III and I and pyruvate dehydrogenase might lead to the increased production of free radical resulting in oxidative stress and cerebral energy disturbances thereby leading to mitochondrial swelling and further contributing to the pathogenesis of FHF.

Simvastatin for rats with thioacetamide-induced liver failure and encephalopathy

BACKGROUND AND AIM

Nitric oxide (NO) inhibition aggravates hepatic damage and encephalopathy and increases mortality in rats with thioacetamide (TAA)-induced acute liver failure. Statins enhance NO synthase expression beyond their lipid-lowering capability, but the impact on encephalopathy remains unexplored. The aim of this study was to assess the effects of simvastatin on rats with TAA-induced acute liver damage and hepatic encephalopathy.

METHODS

Sprague-Dawley rats received TAA (350 mg/kg/day) or normal saline (NS) by intraperitoneal injection for 3 consecutive days. Two days before injections, each group was divided into three subgroups, taking (i) distilled water; (ii) simvastatin (20 mg/kg/day); or (iii) simvastatin plus N(G)-nitro-l-arginine methyl ester (L-NAME, 25 mg/kg/day) by oral gavage for 5 days. On the fifth day, severity of encephalopathy was assessed and plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin and ammonia were measured.

RESULTS

The TAA subgroups showed higher ALT, AST, bilirubin and ammonia levels and lower motor activity counts as compared with the NS subgroups. Among the TAA-treated subgroups, rats with simvastatin treatment exerted higher motor activity counts and survival rate (P = 0.043), and a trend of lower ALT, AST, bilirubin and ammonia levels than those receiving saline. All rats that underwent simvastatin plus L-NAME treatment died during or after TAA injections.

CONCLUSIONS

Simvastatin improved encephalopathy and survival in TAA-administered rats. The beneficial effect was offset by L-NAME, suggesting the role of NO in liver damage and encephalopathy.

Acute and chronic liver insufficiency

The term “liver insufficiency” denotes a break down in the functions of the liver. The syndrome of functional liver failure covers a wide spectrum of clinical, biochemical and neurophysiological changes. In principle, liver insufficiency can occur without previous liver damage as well as with already existing liver disease. It is characterized by a deterioration in the synthesizing, regulatory and detoxifying function of the liver. This final stage of liver disease terminates in hepatic coma.

Therapy of intracranial hypertension in patients with fulminant hepatic failure

Severe intracranial hypertension (IH) in the setting of fulminant hepatic failure (FHF) carries a high mortality and is a challenging disease for the critical care provider. Despite considerable improvements in the understanding of the pathophysiology of cerebral edema during liver failure, therapeutic maneuvers that are currently available to treat this disease are limited. Orthotopic liver transplantation is currently the only definitive therapeutic strategy that improves outcomes in patients with FHF. However, many patients die prior to the availability of donor organs, often because of cerebral herniation. Currently, two important theories prevail in the understanding of the pathophysiology of IH during FHF. Ammonia and glutamine causes cytotoxic cerebral injury while cerebral vasodilation caused by loss of autoregulation increases intracranial pressure (ICP) and predisposes to herniation. Although ammonia-reducing strategies are limited in humans, modulation of cerebral blood flow seems promising, at least during the early stages of hepatic encephalopathy. ICP monitoring, transcranial Doppler, and jugular venous oximetry offer valuable information regarding intracranial dynamics. Induced hypothermia, hypertonic saline, propofol sedation, and indomethacin are some of the newer therapies that have been shown to improve survival in patients with severe IH. In this article, we review the pathophysiology of IH in patients with FHF and outline various therapeutic strategies currently available in managing these patients in the critical care setting.

Acute Liver Failure

Acute liver failure (ALF) is an uncommon medical emergency whose rapid progression and high mortality demand early diagnosis and expert management, including immediate transfer of any potential case to facilities for intensive care and orthotopic liver transplantation (OLT). All patients with ALF must be screened aggressively for acetaminophen toxicity (history, serum levels, "hyperacute" presentation with renal failure), for other drugs, and viral hepatitis; rare causes of ALF should also be considered. After an acetaminophen overdose, N-acetylcysteine must be given as early as possible, preferably in the emergency room, but any patient with ALF should promptly receive N-acetylcysteine if there is suspicion of acetaminophen toxicity irrespective of the time of ingestion. Supportive care for all patients with ALF includes adequate enteral nutrition, aggressive screening and treatment of infection, prophylactic broad-spectrum antibiotics, and antifungal agents. Sedation with propofol is given for severe agitation or mechanical ventilation. With advanced coma grades, intensive care is needed with hemodynamic monitoring, ventilatory support, continuous renal replacement for renal failure, and intracranial pressure monitoring. Intracranial hypertension is treated with mannitol and/or acute short-term hyperventilation, but if the patient is refractory to treatment, mild-moderate hypothermia is achieved by a cooling blanket that is continued throughout OLT. Barbiturate coma is only used in refractory cases as the last treatment modality. Seizures are aggressively treated with phenytoin, with additional diazepam as needed. Candidacy and activation for OLT should be completed as early as possible in the course of ALF, especially in "hyperacute" cases such as acetaminophen toxicity. The final decision to proceed with OLT is made when a donor organ becomes available. King's College Hospital criteria for OLT are still the best prognostic assessment for fatal outcome in ALF, but the criteria fail to identify some patients who will die.

Prophylactic phenytoin does not improve cerebral edema or survival in acute liver failure--a controlled clinical trial

BACKGROUND/AIMS

Seizure activity in patients with acute liver failure (ALF) may increase cerebral oxygen requirements and worsen cerebral edema. Recently, prophylactic phenytoin has been recommended to suppress sub-clinical seizure activity evident on electroencephalographic monitoring. To determine the clinical utility of prophylactic phenytoin therapy in patients with ALF.

METHODS

Forty two patients with ALF were randomized. Twenty two patients were given prophylactic phenytoin and 22 patients acted as controls. The baseline clinical and biochemical features were similar in the two groups and patients with > or =2 poor prognostic variables were equally represented.

RESULTS

Sixteen patients in the phenytoin group, and 15 in the control group developed cerebral edema (P=0.38). Mechanical ventilation was required in 10 and 12 patients in the phenytoin and control groups, respectively, (P=0.77). Seizures occurred in 5 (22.7%) control patients and 5 (25%) phenytoin treated patients (P=0.86). Fourteen (70%) patients randomized to phenytoin and 15 (68.2%) control patients died (P=0.89).

CONCLUSIONS

Seizure was common in patients with ALF. Prophylactic use of phenytoin did not prevent cerebral edema, seizures or need for mechanical ventilation, and did not improve survival.

[Acute liver failure]

Acute liver failure is characterized by a dynamic clinical course associated with high mortality. The main prognostic determinant is the development of extrahepatic complications. Close monitoring is mandatory, and prophylactic measures to avoid complications should be initiated. In case of complications, early and aggressive treatment is indicated. To date, artificial liver support devices are still in the experimental phase. Liver transplantation should be considered in patients with predictors of a poor spontaneous prognosis. Therefore, a transplant center should be contacted in every case of acute liver failure.

Cerebral oxygenation determined by near-infrared spectrophotometry in patients with fulminant hepatic failure

BACKGROUND/AIMS

In severe cases of acute liver failure (ALF), cerebral hyperperfusion may result in high intracranial pressure and brain damage. The aim of this study was to determine if near-infrared spectrophotometry (NIRS) could detect a raise in cerebral blood flow and oxygenation induced by noradrenaline (NA) infusion.

METHODS

In seven ALF patients (five females and two males; median age 49 years (range 20-70)) changes in cerebral concentration of oxy-(deltaHbO(2)) and total-haemoglobin (deltaHbT) were compared to the jugular bulb saturation (SvjO(2)) and cerebral blood flow velocity (Vmean) during NA infusion.

RESULTS

Mean arterial pressure increased from 68 (64-86) to 103 (87-118) mmHg and the cerebral perfusion pressure from 61 (53-79) to 95 (74-110) mmHg (P<0.05), while the intracranial pressure (7 (6-15) mmHg) was not significantly changed. In six patients cerebral deltaHbO(2) and deltaHbT increased 2.7 (0.3-9.6) and 2.0 (0.3-14.8) micromol l(-1), respectively, but cerebral oxygenation decreased in one patient. SvjO(2) increased from 68 (55-76) to 74 (64-78) % (P<0.05) concomitant with an increase in Vmean from 47 (34-65) to 68 (50-86) cm s(-1) (P<0.05). deltaHbO(2) covariated with changes in SvjO(2) during NA in all but one patient.

CONCLUSIONS

In ALF patients, a change in cerebral perfusion was detected by NIRS. The combination of NIRS and transcranial Doppler sonography may be valuable non-invasive techniques to detect cerebral hyperperfusion before intracranial hypertension becomes manifest.

Suppression of ammonia-induced swelling by aspartate but not by ornithine in primary cultures of rat astrocytes

Cerebral edema with a rise in intracranial pressure is the hallmark of fulminant hepatic failure (FHF) and acute hyperammonemic (HA) states and is characterized by a poor survival rate. Astrocytes are the cells in brain which are swollen in these conditions. Several hypotheses have been proposed to explain the mechanism of cerebral edema in FHF and treatment strategies have evolved based on these putative mechanisms. Treatment with a mixture of ornithine and aspartate has been proven to be clinically beneficial as it reduces edema and improves the neurological status. It has been suggested that these two amino acids generate the glutamate required for the synthesis of glutamine and that they also enhance urea synthesis in surviving hepatocytes in FHF and HA. Presently, we report that of these two amino acids, only aspartate is effective in suppressing ammonia-induced swelling in primary cultures of astrocytes, while ornithine is ineffective. These results are discussed in relation to the metabolism of aspartate and ornithine in astrocytes, with an emphasis on glutamine synthesis and the malate-aspartate shuttle (MAS). We propose that the ability of aspartate to generate glutamate in the cytosol for glutamine synthesis and oxaloacetate in mitochondria to support the citric acid cycle play a role in its ability to reduce ammonia-induced swelling in astrocytes.

Nitric oxide in hepatic encephalopathy and hyperammonemia

Chronic alcoholism, viral hepatitis or hepatotoxic drug overdose result in liver dysfunction which may lead to a neuropsychiatric disorder termed hepatic encephalopathy (HE). Although, the exact molecular mechanisms underlying the pathophysiology of HE are not known, excitatory/inhibitory neurotransmitter imbalance leading to dysfunction of the glutamate-nitric oxide (NO) system is thought to play a major role. Activation of the NMDA subtype of glutamate receptors leads to increase in intracellular calcium, which initiates several calcium-dependent processes including NO formation. NO is a gaseous, highly reactive, freely diffusible molecule with a short half-life. Recent studies demonstrate increased expression of the neuronal isoform of NO synthase (NOS) and the uptake of L-arginine (the obligate precursor of NO) in both chronic and acute HE. Hyperammonemia associated with liver dysfunction results in increased NO, which may lead to learning and memory impairments and cerebral edema commonly seen, particularly in acute hyperammonemia.

Prolonged unilateral vasodilatation and brain edema in fulminant hepatic failure, associated with symptomatic seizure

We report prolonged unilateral vasodilatation and hemispheric brain edema in a 49-year-old man with fulminant hepatic failure (FHF). The patient presented with a tonic-clonic seizure caused by a hypertensive subcortical hemorrhage in the left parietal lobe. Serial computed tomography (CT) scans showed progressive darkening of the ipsilateral hemisphere, suggesting hemispheric cerebral infarction, but the patient did not show clinical signs of deterioration. Brain magnetic resonance angiography showed dilation of the large arteries of the left hemisphere. Evaluation of cerebral blood flow 7 days postictus with single photon emission CT revealed marked ipsilateral hyperperfusion. The darkening of the hemisphere was brain edema elicited by hyperperfusion. Brain edema was reversible, disappearing 14 days postictus. Hemispheric brain edema was caused by unilateral cerebral vasodilatation and resultant hyperperfusion. Although brain edema is a major complication in FHF patients and cerebral hyperperfusion is responsible for edema formation, CT findings of these patients almost invariably show a bilateral lesion. Unilateral vasodilatation and subsequent hemispheric hyperperfusion may be due to overproduction of vasodilators, already abundant in the brains of patients with severe hepatic failure, by seizure activity.

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.

Diagnosis and treatment of hepatic encephalopathy

Hepatic encephalopathy arises from the combination of hepatocellular dysfunction and portal-systemic shunting. Encephalopathy is more prominent in advanced stages of liver cirrhosis and signals the presence of fulminant hepatic failure in patients with acute liver injury. As important as the extent of shunting is the presence of large spontaneous collaterals. Ammonia continues to be a leading toxin influencing brain function. Endogenous benzodiazepines and cytokines may contribute to one of ammonia's key effects in the brain: astrocyte swelling. The diagnosis of hepatic encephalopathy is a diagnosis of exclusion; the search for a precipitating factor should be started immediately in all cases of encephalopathy. The treatment of hepatic encephalopathy has three aims: decrease the nitrogenous load from the gut, improve the extra-intestinal elimination of ammonia and counteract central abnormalities of neurotransmission. The mainstay of treatment is directed at the colon. Newer approaches targeting the brain, such as flumazenil, have become available.