Metabolic brain disease
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Metabolic brain disease · Dec 2004
ReviewCerebral blood flow in acute liver failure: a finding in search of a mechanism.
In the last few years, several abnormalities of cerebral blood flow (CBF), namely loss of cerebral autoregulation, altered reactivity to carbon dioxide, and development of cerebral hyperemia, have been described in patients as well as experimental models of acute liver failure (ALF) and/or hyperammonemia. The development of cerebral hyperemia seems particularly relevant to the pathogenesis of brain edema in ALF. ⋯ In the rat after portacaval anastomosis receiving an ammonia infusion, the signal resulting in cerebral hyperemia arises within the brain once maximal glutamine accumulation has occurred in astrocytes. Several mediators potentially involved in the development of cerebral hyperemia in ALF are examined in this review, but further work is needed to assess the role, if any, of each of them.
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The development of encephalopathy in patients with acute liver injury defines the occurrence of liver failure. The encephalopathy of acute liver failure is characterized by brain edema which manifests clinically as increased intracranial pressure. Despite the best available medical therapies a significant proportion of patients with acute liver failure die due to brain herniation. The present review explores the experimental and clinical data to define the role of hypothermia as a treatment modality for increased intracranial pressure in patients with acute liver failure.
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Metabolic brain disease · Dec 2002
Mild hypothermia in the prevention of brain edema in acute liver failure: mechanisms and clinical prospects.
Mild hypothermia (32 degrees C-35 degrees C) reduces intracranial pressure in patients with acute liver failure and may offer an effective adjunct therapy in the management of these patients. Studies in experimental animals suggest that this beneficial effect of hypothermia is the result of a decrease in blood-brain ammonia transfer resulting in improvement in brain energy metabolism and normalization of glutamatergic synaptic regulation. ⋯ Restoration of normal glutamatergic synaptic regulation by hypothermia may be the consequence of the removal of ammonia-induced decreases in expression of astrocytic glutamate transporters resulting in normal glutamate neurotransmitter inactivation in brain. Randomized controlled clinical trials of hypothermia are required to further evaluate its clinical impact.
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Metabolic brain disease · Dec 2002
ReviewHypothermia for the management of intracranial hypertension in acute liver failure.
Increased intracranial pressure in patients with acute liver failure (ALF) remains a major immediate cause of mortality. Several studies in animal models of ALF set the stage for the clinical application of moderate hypothermia in man. ⋯ Data from studies in patients undergoing liver transplantation for ALF suggest that increases in intracranial pressure can be prevented during the dissection and reperfusion phases of the operation if the patients are maintained hypothermic during surgery. The present review focuses upon the clinical aspects of using hypothermia as a treatment of increased intracranial pressure in patients with ALF.
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Metabolic brain disease · Jun 2001
Mild hypothermia prevents cerebral edema and CSF lactate accumulation in acute liver failure.
Evidence from both clinical and experimental studies demonstrates that mild hypothermia prevents encephalopathy and brain edema in acute liver failure (ALF). As part of a series of studies to elucidate the mechanism(s) involved in this protective effect, groups of rats with ALF resulting from hepatic devascularization were maintained at either 37 degrees C (normothermic) or 35 C (hypothermic), and neurological status was monitored in relation to cerebrospinal fluid (CSF) concentrations of ammonia and lactate. CSF was removed via implanted cisterna magna catheters. ⋯ Blood ammonia concentrations, on the other hand, were not affected by hypothermia in ALF rats. These findings suggest that brain edema and encephalopathy in ALF are the consequence of ammonia-induced impairment of brain energy metabolism and open the way for magnetic resonance spectroscopic monitoring of cerebral function in ALF. Mild hypothermia could be beneficial in the prevention of severe encephalopathy and brain edema in patients with ALF awaiting liver transplantation.