Paracetamol hepatotoxicity: how to prevent

Cerebral hemodynamic and metabolic changes in fulminant hepatic failure

ABSTRACT Intracranial hypertension and brain swelling are a major cause of morbidity and mortality of patients suffering from fulminant hepatic failure (FHF). The pathogenesis of these complications has been investigated in man, in experimental models and in isolated cell systems. Currently, the mechanism underlying cerebral edema and intracranial hypertension in the presence of FHF is multi-factorial in etiology and only partially understood. The aim of this paper is to review the pathophysiology of cerebral hemodynamic and metabolism changes in FHF in order to improve understanding of intracranial dynamics complication in FHF.

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.

Update: the clinical importance of acetaminophen hepatotoxicity in non-alcoholic and alcoholic subjects

Acetaminophen (paracetamol) is one of the most commonly used over-the-counter medications. Taken in doses greater than 150 mg/kg/day (>10 g), it usually causes acute liver failure. The authors review mainly the management of acetaminophen toxicity in both users and nonusers of alcohol. Chronic alcoholics are a special subgroup, who risk serious toxicity when taking acetaminophen, even in therapeutic doses. The acetaminophen-alcohol interaction is complex, because acute and chronic ethanol have opposite effects. This review also considers physiological and clinical changes, as well as the diagnosis and treatment of acetaminophen poisoning.

Improvements in the packaging of drugs and chemicals may reduce the likelihood of severe intentional poisonings in adults

Because of the inconvenience and longer time required to punch out the tablets, strip packaging may reduce the number of tablets that can be readily swallowed by adults with self-poisonings. In fact, hospital-based studies of paracetamol poisoning in the U.K. and Hong Kong have shown that blister packs were associated with fewer tablets being ingested and large overdoses were mostly from loose preparations. In Australia, following the change in packaging for carbamazepine from bottles of tablets to blister packs, a marked decrease in the reported number of tablets ingested by patients was seen. Reducing the maximum number of tablets that can be available in individual preparations or prescriptions may also reduce the likelihood of severe poisonings. In France, but not in the UK, the content of each pack of paracetamol has been legally limited to 8 g. This was thought to be one reason why severe liver damage and deaths after paracetamol poisonings are less common in France than in the UK. Medicated oils containing methyl salicylate pose the threat of rapid-onset, severe salicylate poisoning if swallowed. To reduce the amount of methyl salicylate that can be readily swallowed, the methyl salicylate content and the size of the bottle and its opening should be restricted. In adults with Dettol poisoning, serious complications such as pulmonary aspiration are more likely if a large amount is ingested. Similarly, the risk may be reduced by restricting the size of bottle and its opening.