Therapeutic hypothermia for acute liver failure. Crit Care Med. 2009;37:S258-S264. [PMID: 19535956 DOI: 10.1097/ccm.0b013e3181aa5fb8]

Recent insights into the pathogenesis of hepatic encephalopathy and treatments

Hepatic encephalopathy (HE) encompasses a spectrum of neuropsychiatric disorders related to liver failure. The development of HE can have a profound impact on mortality as well as quality of life for patients and carers. Ammonia is central in the disease process contributing to alteration in neurotransmission, oxidative stress, and cerebral edema and astrocyte swelling in acute liver failure. Inflammation in the presence of ammonia coactively worsens HE. Inflammation can result from hyperammonemic responses, endotoxemia, innate immune dysfunction or concurrent infection. This review summarizes the current processes implicated in the pathogenesis of HE, as well as current and potential treatments. Treatments currently focus on reducing inflammation and/or blood ammonia levels and provide varying degrees of success. Optimization of current treatments and initial testing of novel therapies will provide the basis of improvement of care in the near future.

Preventing cerebral oedema in acute liver failure: the case for quadruple-H therapy

Severe cerebral oedema is a life-threatening complication of acute liver failure. Hyperammonaemia and cerebral hyperaemia are major contributing factors. A multimodal approach, which incorporates hyperventilation, haemodiafiltration, hypernatraemia and hypothermia (quadruple-H therapy), may prevent or attenuate severe cerebral oedema. This approach is readily administered by critical care clinicians and is likely to be more effective than the use of single therapies. Targeting of PaCO2 in the mild hyperventilation range, as seen in acute liver failure patients before intubation, aims to minimise hyperaemic cerebral oedema. Haemodiafiltration aims to achieve the rapid control of elevated blood ammonia concentrations by its removal and to reduce production via the lowering of core temperature. The administration of concentrated saline increases serum tonicity and further reduces cerebral swelling. In addition, the pathologically increased cerebral blood-flow is further attenuated by therapeutic hypothermia. The combination of all four treatments in a multimodal approach may be a safe and effective means of attenuating or treating the cerebral oedema of acute liver failure and preventing death from neurological complications.

Neurologic manifestations of acute liver failure

Fulminant hepatic failure presents with a hepatic encephalopathy and may progress to coma and often brain death from cerebral edema. This natural progression in severe cases contributes to early mortality, but outcome can be good if liver transplantation is appropriately timed and increased intracranial pressure (ICP) is managed. Neurologists and neurosurgeons have become more involved in these very challenging patients and are often asked to rapidly identify patients who are at risk of cerebral edema, to carefully select the patient population who will benefit from invasive ICP monitoring, to judge the correct time to start monitoring, to participate in treatment of cerebral edema, and to manage complications such as intracranial hemorrhage or seizures. This chapter summarizes the current multidisciplinary approach to fulminant hepatic failure and how to best bridge patients to emergency liver transplantation.

Assessment of adverse events and predictors of neurological recovery after therapeutic hypothermia

BACKGROUND

Therapeutic hypothermia improves neurological recovery after witnessed cardiac arrest from ventricular fibrillation or tachycardia. Its application is expanding despite associated adverse events.

OBJECTIVE

To assess the occurrence of adverse events and predictors of good versus poor neurological recovery after therapeutic hypothermia.

METHODS

A single-center, retrospective review of medical records of 91 patients who received therapeutic hypothermia for ≥6 hours. Adverse events included laboratory abnormalities, shivering, acute kidney injury, or infection. Cerebral performance categories (CPC) scores delineated good (CPC of 1-3) or poor (CPC of 4 or 5) neurological outcomes. Groups were compared and parameters evaluated for effect on neurological recovery using backward logistic regression analysis.

RESULTS

Therapeutic hypothermia was used for several indications, and 42 patients (46.2%) had good neurological recovery. Demographic parameters were similar between groups. Common adverse events were hypoglycemia (98.9%), shivering (84.6%), bradycardia (58.2%), electrolyte abnormalities (26.4%-91.2%), acute kidney injury (52.8%), infection (48.4%), and coagulopathy (40.7%). Characteristics independently associated with neurological recovery included faster return of spontaneous circulation (ROSC), quicker initiation of cooling, and the occurrence of infections. Pulseless electrical activity, faster achievement of goal cooling temperature, seizure, and the administration of insulin or epinephrine were inversely related to neurological recovery.

CONCLUSIONS

Adverse events of therapeutic hypothermia were numerous and frequent, necessitating monitoring. Neurological recovery is primarily driven by the type of arrest, the rapidity of ROSC, the time needed to provide and achieve therapeutic hypothermia, the development of seizures or infection, and the use of insulin or epinephrine.

Selective head cooling for the treatment of neurologic complications of acute liver failure in a newborn with disseminated herpes infection

Background

Neurologic complications of pediatric acute liver failure (ALF) are a major determinant of outcome. Management of these complications, including increased intracranial pressure (ICP) is largely supportive. Although hypothermia is an effective treatment for perinatal asphyxia and is used to reduce ICP following traumatic brain injury, it has not been evaluated for neurologic complications of ALF in the newborn.

Methods

Case report.

Results

We present a case of neonatal herpes simplex virus (HSV)-associated ALF with profound neurologic impairment and increased ICP. The patient was treated with selective head cooling, and monitored with transcranial doppler (TCD) studies of cerebral blood flow velocity, and electroencephalograms (EEG). The duration of head cooling was influenced by absent diastolic flow on TCDs, which subsequently improved during hypothermia. Continuous EEGs captured subclinical seizures, which improved with antiepileptic medications. Her death was attributed to a massive pulmonary hemorrhage and a hypoxemic cardiac arrest secondary to significant coagulopathy.

Conclusion

This case demonstrates that selective head cooling may attenuate increased ICP in neonatal encephalopathy, and that TCDs may guide management in the absence of invasive monitoring.

Acute liver failure

Untreated acute liver failure (ALF) has a poor outcome and so rapid diagnosis and management is vital if the patient is to survive. ALF has such profound and widespread physiological consequences that whenever possible, patients with ALF should be managed in an intensive care unit. Management is to support the physiology and treat the underlying cause. Advice should be sought from a centre capable of performing liver transplantation. Should recovery seem unlikely, liver transplantation is a viable treatment option in some cases.

Fulminant viral hepatitis

Acute liver failure (ALF) is a condition wherein the previously healthy liver rapidly deteriorates, resulting in jaundice, encephalopathy, and coagulopathy. There are approximately 2000 cases per year of ALF in the United States. Viral causes (fulminant viral hepatitis [FVH]) are the predominant cause of ALF in developing countries. Given the ease of spread of viral hepatitis and the high morbidity and mortality associated with ALF, a systematic approach to the diagnosis and treatment of FVH is required. In this review, the authors describe the viral causes of ALF and review the intensive care unit management of patients with FVH.

Perioperative liver protection

PURPOSE OF REVIEW

This review presents important pathophysiological alterations associated with impaired liver function and discusses protective perioperative strategies and the various anaesthetic agents recommended.

RECENT FINDINGS

Perioperative liver impairment is a serious complication of anaesthesia and surgery. Unfortunately, clinicians are provided with only crude macrohaemodynamic monitoring devices to optimize their therapy. Technical improvements have revealed some complex mysteries of perioperative microcirculatory alterations and have disclosed a large heterogeneity between different vascular beds. The present review will critically discuss current clinical concepts of optimizing global haemodynamic variables and the often contrasting effects of vasoactive agents on the microcirculatory nutritional blood flow. Finally, promising protective experimental interventions of pharmacological or ischaemic preconditioning are presented and their often disillusioning transition into recent clinical trials is highlighted.

SUMMARY

Targeted perioperative liver protection still lacks adequate monitoring tools and is currently based on optimization of global haemodynamic variables. While there is currently no evidence suggesting a positive effect of ischaemic preconditioning, promising experimental results of pharmacological preconditioning and therapeutic hypothermia require further evaluation in larger randomized clinical trials.

Combined therapy for acute hepatic failure

Acute hepatic failure (AHF) is a devastating clinical syndrome characterized by rapid impairment of liver functions and development of encephalopathy, multiple organ failure, and in most cases cerebral edema. AHF has a high mortality rate. Although advances in drug treatment, artificial liver and liver transplantation have significantly improved the prognosis of AHF, there is still a lack of effective treatment for AHF because of its complicated etiopathogenesis, rapid progression and less clinical knowledge about managing the disease. There is an urgent need to develop effective treatments for AHF. This article aims to review recent advances in the treatment of AHF.

Management and prognosis of acute liver failure in children

Although the etiologies of pediatric acute liver failure (ALF) are diverse, ultimate pathophysiologic pathways and management challenges for these disorders, usually lethal in the pre-transplant era, are similar. This review considers particularly the mechanisms of, and monitoring for, intracranial hypertension and coagulopathy; summarizes detailed advice for management of the ALF-associated failures of multiple body systems; and reviews the variety of prognostic scores available to guide management and assist in choosing the patients most apt to benefit from liver transplantation and the optimal timing for such transplantation.

Shivering management during therapeutic temperature modulation: nurses' perspective

Therapeutic temperature modulation, which incorporates mild hypothermia and maintenance of normothermia, is being used to manage patients resuscitated after cardiac arrest. Methods of modulating temperature include intravenous infusion of cold fluids and surface or endovascular cooling. During this therapy, the shiver response is activated as a defense mechanism in response to an altered set-point temperature and causes metabolic and hemodynamic stress for patients. Recognition of shivering according to objective and subjective assessments is vital for early detection of the condition. Once shivering is detected, treatment is imperative to avoid deleterious effects. The Bedside Shivering Assessment Scale can be used to determine the efficacy of interventions intended to blunt thermoregulatory defenses and can provide continual evaluation of patients' responses to the interventions. Nurses' knowledge and understanding of the harmful effects of shivering are important to effect care and prevent injury associated with uncontrolled shivering.

Neurological complications of acute liver failure: pathophysiological basis of current management and emerging therapies

One of the major causes of mortality in patients with acute liver failure (ALF) is the development of hepatic encephalopathy (HE) which is associated with increased intracranial pressure (ICP). High ammonia levels, increased cerebral blood flow and increased inflammatory response have been identified as major contributors to the development of HE and the related brain swelling. The general principles of the management of patients with ALF are straightforward. They include identifying the insult causing hepatic injury, providing organ systems support to optimize the patient's physical condition, anticipation and prevention of development of complications. Increasing insights into the pathophysiological mechanisms of ALF are contributing to better therapies. For instance, the evident role of cerebral hyperemia in the pathogenesis of increased ICP has led to a re-evaluation of established therapies such as hyperventilation, N-acetylcysteine, thiopentone sodium and propofol. The role of systemic inflammatory response in the pathogenesis of increased ICP has also gained importance supporting the concept that antibiotics given prophylactically reduce the risk of developing sepsis during the course of illness. Moderate hypothermia has also been established as a therapy able to reduce ICP in patients with uncontrolled intracranial hypertension and to prevent increases in ICP during orthopic liver transplantation. Ornithine phenylacetate, a new drug in the treatment of liver failure, and liver replacement therapies are still being investigated both experimentally and clinically. Despite many advances in the understanding of the pathophysiological basis and the management of intracranial hypertension in ALF, more clinical trials should be conducted to determine the best therapeutic management for this difficult clinical event.

Neurological management of fulminant hepatic failure

Acute liver failure (ALF) is uncommon in the United States, but presents acutely and catastrophically, often with deadly consequences. Hepatic encephalopathy, cerebral edema, elevated intracranial pressure, and intracranial hemorrhage due to coagulopathy are common occurrences in patients with ALF. Appropriate management of multi-system organ failure and neurological complications are essential in bridging patients to transplant and ensuring satisfactory outcomes.

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.

A simple dummy liver assist device prolongs anhepatic survival in a porcine model of total hepatectomy by slight hypothermia

BACKGROUND

Advances in intensive care support such as therapeutic hypothermia or new liver assist devices have been the mainstay of treatment attempting to bridge the gap from acute liver failure to liver transplantation, but the efficacy of the available devices in reducing mortality has been questioned. To address this issue, the present animal study was aimed to analyze the pure clinical effects of a simple extracorporeal dummy device in an anhepatic porcine model of acute liver failure.

METHODS

Total hepatectomy was performed in ten female pigs followed by standardized intensive care support until death. Five animals (dummy group, n = 5) underwent additional cyclic connection to an extracorporeal dummy device which consisted of a plasma separation unit. The separated undetoxified plasma was completely returned to the pigs circulation without any plasma substitution or exchange in contrast to animals receiving intensive care support alone (control group, n = 5). All physiological parameters such as vital and ventilation parameters were monitored electronically; laboratory values and endotoxin levels were measured every 8 hours.

RESULTS

Survival of the dummy device group was 74 ± 6 hours in contrast to 53 ± 5 hours of the control group which was statistically significant (p < 0.05). Body temperature 24 hours after hepatectomy was significantly lower (36.5 ± 0.5°C vs. 38.2 ± 0.7°C) in the dummy device group. Significant lower values were measured for blood lactate (1.9 ± 0.2 vs. 2.5 ± 0.5 mM/L) from 16 hours, creatinine (1.5 ± 0.2 vs. 2.0 ± 0.3 mg/dL) from 40 hours and ammonia (273 ± 122 vs. 1345 ± 700 μg/dL) from 48 hours after hepatectomy until death. A significant rise of endotoxin levels indicated the onset of sepsis at time of death in 60% (3/5) of the dummy device group animals surviving beyond 60 hours from hepatectomy.

CONCLUSIONS

Episodes of slight hypothermia induced by cyclic connection to the extracorporeal dummy device produced a significant survival benefit of more than 20 hours through organ protection and hemodynamic stabilisation. Animal studies which focus on a survival benefit generated by liver assist devices should especially address the aspect of slight transient hypothermia by extracorporeal cooling.

Favorable long-term outcome following severe neonatal hyperammonemic coma in a patient with argininosuccinate synthetase deficiency

This chapter reports on the sequelae-free 8-year follow-up with normal growth, intellectual development, and schooling of a boy with argininosuccinate synthetase deficiency (citrullinemia type I) who was rescued from severe neonatal hyperammonemic coma at 8 days of life (peak ammonia level of 1,058 μmol/L). Important clinical management aspects were: rapidity of response to emergency therapeutic measures that included specific drug regimen, protein restriction, optimal caloric intake and hemodialysis, short coma duration (14 h), possible neuroprotective effect of mild systemic hypothermia during the acute episode, long-term metabolic control with strict compliance to standard of care therapeutic and dietary regimens, active prevention of subsequent hyperammonemic episodes, and early neurodevelopmental evaluations and interventions. We conclude that good long-term neurological outcome following rescue from neonatal hyperammonemic coma is rarely reported but attainable. Prospective registries and interventional studies regrouping clinical data from urea cycle disorders patients will assist clinicians in instituting the appropriate therapeutic measures to provide the best prospect of positive long-term outcome for these children.

Bridging Therapies and Liver Transplantation in Acute Liver Failure; 10 Years of MARS Experience from Finland

Acute liver failure is a life-threatening condition in the absence of liver transplantation option. The aetiology of liver failure is the most important factor determining the probability of native liver recovery and prognosis of the patient. Extracorporeal liver assist devices like MARS (Molecular Adsorbent Recirculating System) may buy time for native liver recovery or serve as bridging therapy to liver transplantation, with reduced risk of cerebral complications. MARS treatment may alleviate hepatic encephalopathy even in patients with a completely necrotic liver. Taking this into account, better prognostic markers than hepatic encephalopathy should be used to assess the need for liver transplantation in acute liver failure.

Therapeutic hypothermia: critical review of the molecular mechanisms of action

Therapeutic hypothermia (TH) is nowadays one of the most important methods of neuroprotection. The events that occur after an episode of ischemia are multiple and hypothermia can affect the various steps of this cascade. The mechanisms of action of TH are varied and the possible explanation for the benefits of this therapy is probably the multiple mechanisms of action blocking the cascade of ischemia on many levels. TH can affect many metabolic pathways, reactions of inflammation, apoptosis processes, and promote neuronal integrity. To know the mechanisms of action of TH will allow a better understanding about the indications for this therapy and the possibility of searching for other therapies when used in conjunction with hypothermia will provide a therapeutic synergistic effect.

Hepatobiliäre Funktionsstörungen und Leberversagen

Als »sepsisinduzierte Cholestase« bezeichnet man das Auftreten einer konjugierten Hyperbilirubinämie als Folge einer extrahepatischen bakteriellen Infektion ohne direkte Invasion der Leber durch Erreger.

Glutamine as a mediator of ammonia neurotoxicity: A critical appraisal

Ammonia is a major neurotoxin implicated in hepatic encephalopathy (HE). Here we discuss evidence that many aspects of ammonia toxicity in HE-affected brain are mediated by glutamine (Gln), synthesized in excess from ammonia and glutamate by glutamine synthetase (GS), an astrocytic enzyme. The degree to which Gln is increased in brains of patients with HE was found to positively correlate with the grade of HE. In animals with HE, a GS inhibitor, methionine sulfoximine (MSO), reversed a spectrum of manifestations of ammonia toxicity, including brain edema and increased intracranial pressure, even though MSO itself increased brain ammonia levels. MSO inhibited, while incubation with Gln reproduced the oxidative stress and cell swelling observed in ammonia-exposed cultured astrocytes. Recent studies have shown that astrocytes swell subsequent to Gln transport into mitochondria and its degradation back to ammonia, which then generates reactive oxygen species and the mitochondrial permeability transition. This sequence of events led to the formulation of the "Trojan Horse" hypothesis. Further verification of the role of Gln in the pathogenesis of HE will have to account for: (1) modification of the effects of Gln by interaction of astrocytes with other CNS cells; and (2) direct effects of Gln on these cells. Recent studies have demonstrated a "Trojan Horse"-like effect of Gln in microglia, as well as an interference by Gln with the activation of the NMDA/NO/cGMP pathway by ammonia as measured in whole brain, a process that likely also involves neurons.

Acute liver failure

Acute liver failure is a rare disorder with high mortality and resource cost. In the developing world, viral causes predominate, with hepatitis E infection recognised as a common cause in many countries. In the USA and much of western Europe, the incidence of virally induced disease has declined substantially in the past few years, with most cases now arising from drug-induced liver injury, often from paracetamol. However, a large proportion of cases are of unknown origin. Acute liver failure can be associated with rapidly progressive multiorgan failure and devastating complications; however, outcomes have been improved by use of emergency liver transplantation. An evidence base for practice is emerging for supportive care, and a better understanding of the pathophysiology of the disorder, especially in relation to hepatic encephalopathy, will probably soon lead to further improvements in survival rates.

Diagnosis and management of acute liver failure

PURPOSE OF REVIEW

Acute liver failure (ALF) is a devastating syndrome afflicting previously healthy individuals. Early recognition of the illness is crucial, as aggressive treatment may improve outcomes. Despite significant advances in care, however, the mortality remains high (30-100%). This brief review will focus on the causes and overall management of the complications of ALF.

RECENT FINDINGS

Our knowledge of the causes of ALF has expanded significantly in the last decade. The mechanism of hepatic encephalopathy and cerebral edema in this setting continues to be elucidated and is discussed here.

SUMMARY

Improved outcomes can be achieved with the early recognition and aggressive management of ALF.

Treatment of brain edema in acute liver failure

OPINION STATEMENT

Cerebral edema is very common in patients with acute liver failure and encephalopathy. In severe cases, it produces brain tissue shift and potentially fatal herniation. Brain swelling in acute liver failure is produced by a combination of cytotoxic (cellular) and vasogenic edema. Accumulation of ammonia and glutamine leads to disturbances in the regulation of cerebral osmolytes, increased free radical production and calcium-mediated mitochondrial injury, and alterations in glucose metabolism (inducing high levels of brain lactate), resulting in astrocyte swelling. Activation of inflammatory cytokines can cause increased blood-brain barrier permeability leading to vasogenic edema, although the relative contribution of vasogenic edema is probably minor compared with cellular swelling. Cerebral blood flow is disturbed and generally increased in patients with acute liver failure; persistent vasodilatation and loss of autoregulation may generate hyperemia, and the consequent augmentation in cerebral blood volume may exacerbate brain edema.Adequate management of intracranial hypertension demands continuous monitoring of intracranial pressure and cerebral perfusion pressure. Coagulation status should be assessed and bleeding diathesis should be treated prior to insertion of the intracranial pressure monitor. Standard treatment measures such as hyperventilation and osmotic agents (e.g., mannitol, hypertonic saline) remain useful first-line interventions. Although hypertonic saline may be preferred in patients with coexistent hyponatremia, the rate of correction of hyponatremia must be gradual to avoid the risk of osmotic demyelination. Barbiturate coma and intravenous indomethacin are available options in refractory cases. The most promising novel therapeutic alternative is the induction of moderate hypothermia (aiming for a core temperature of 32-34°C). However, the safety and efficacy of therapeutic hypothermia for brain swelling caused by liver failure still needs to be proven in randomized, controlled clinical trials. Management of intracranial pressure in patients with acute liver failure should be guided by well-defined treatment protocols.

Moderate hypothermia suppresses jugular venous superoxide anion radical, oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion rats

The aim of this study was to assess the effect of moderate hypothermia (MH) on generation of jugular venous superoxide radical (O2-.), oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion (FBI/R) rats. Twenty-one Wistar rats were allocated to a control group (n=7, 37 degrees C), a pre-MH group (n=7, 32 degrees C before ischemia), and a post-MH group (n=7, 32 degrees C after reperfusion). MH was induced before induction of ischemia in the pre-MH group and just after reperfusion in the post-MH group. Forebrain ischemia was induced by occlusion of bilateral common carotid arteries with hemorrhagic hypotension for 10 min, followed by reperfusion. O(2)(-)(.) in the jugular vein was measured from the produced current using a novel O2-. sensor. The O2-. current showed a gradual increase during forebrain ischemia in the control and post-MH groups but was attenuated in the pre-MH group. Following reperfusion, the current showed a marked increase in the control group but was strongly attenuated in the pre- and post-MH groups. Concentrations of malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule-1 (ICAM-1) in the brain and plasma 120 min after reperfusion in the pre- and post-MH groups were significantly lower than those in the control group, except for plasma HMGB1 in the post-MH group. In conclusion, MH suppressed O2-. measured in the jugular vein, oxidative stress, early inflammation, and endothelial injury in FBI/R rats.

Management of acute liver failure

Acute liver failure (ALF) is a syndrome of diverse etiology, in which patients without previously recognized liver disease sustain a liver injury that results in rapid loss of hepatic function. Depending on the etiology and severity of the insult, some patients undergo rapid hepatic regeneration and spontaneously recover. However, nearly 60% of patients with ALF in the US require and undergo orthotopic liver transplantation or die. Management decisions made by clinicians who initially assess individuals with ALF can drastically affect these patients' outcomes. Even with optimal early management, however, many patients with ALF develop a cascade of complications often presaged by the systemic inflammatory response syndrome, which involves failure of nearly every organ system. We highlight advances in the intensive care management of patients with ALF that have contributed to a marked improvement in their overall survival over the past 20 years. These advances include therapies that limit the extent of liver injury and maximize the likelihood of spontaneous recovery and approaches to enable prevention, recognition and early treatment of complications that lead to multi-organ-system failure, the most common cause of death. Finally, we summarize the role of orthotopic liver transplantation in salvage of the most severely affected patients.