Early changes in coagulation following a paracetamol overdose and a controlled trial of fresh frozen plasma therapy

Paracetamol (acetaminophen) poisoning

Paracetamol poisoning caused by intentional overdose remains a common cause of morbidity. In this article the mechanism of toxicity and the clinical effects and treatment of poisoning, including specific antidotal therapy, are reviewed. Areas for further research directed at reducing morbidity and mortality from paracetamol poisoning are considered.

Fulminant hepatic failure

FHF is an uncommon but devastating condition affecting otherwise healthy persons which causes significant morbidity and mortality. The etiologic factor is most commonly viral infection, with drugs and metabolic disorders being relatively less common causes. Hopefully, newer diagnostic techniques such as PCR will increase our understanding of the causes and pathogenesis of this disorder. Medical management at the present time must focus on anticipating, preventing, and rapidly identifying and treating complications that may affect every major organ system. Encouraging research continues on the clinical application of hepatotrophic drugs and artificial liver support systems, both as potentially definitive therapies and as maintenance for patients awaiting transplantation. Consultation with physicians at a transplant center should be sought early in the course of the patient's hospitalization when OLT is being considered. Liver transplantation has dramatically changed the outlook for patients with FHF, with current survival rates in the 55% to 75% range. The continuing challenge for the transplant team is to allocate available donor organs to those patients who would not otherwise survive, but also to provide OLT in a timely fashion to ensure the best chance of post-transplantation recovery. Newer techniques such as heterotopic liver transplantation, reduced-size organ transplantation, and the utilization of living related donors may further improve the survival of these patients.

Intensive liver care and management of acute hepatic failure

In describing acute liver failure, the term fulminant hepatic failure (FHF) is used to denote patients with the most rapid progression, normally defined as the onset of encephalopathy within eight weeks of the onset of symptoms. For patients with a slower onset of encephalopathy, ranging from eight weeks to six months after the onset of symptoms, late-onset hepatic failure is the term used to reflect the overlap in clinical features with some patients with FHF. The importance of accurately determining the type of acute liver failure results from increasing evidence of an inverse relationship between the tempo of disease progression and the chances of recovery. Prognosis is also dependent on the underlying etiology. Principles of management are as follows: (1) an accurate recognition of the tempo of the hepatic failure--fulminant, late onset, acute on chronic--and the establishment of a likely etiology; (2) early detection and treatment of complications, particularly metabolic acidosis (early), renal failure, cerebral edema, and infection (late); (3) optimization of conditions for regeneration by maintenance of a near normal metabolic milieu (with removal of toxins by various methods of artificial liver support if necessary); and (4) early consideration of an orthotopic liver transplant for those patients in the poor prognosis group. Variations in the natural history and clinical features of acute liver failure (ALF) have led to a number of different classifications and subgroupings. Knowledge of these is important in relation to the assessment of prognosis and is even more important now that transplantation is a therapeutic option.(ABSTRACT TRUNCATED AT 250 WORDS)

Fulminant hepatic failure

Most cases of fulminant hepatic failure (FHF) are related to viral hepatitis or to drugs and toxins. With improvement in supportive intensive care, the overall survival has increased, but specific forms of temporary hepatic support pending hepatic regeneration have been disappointing. With the widespread availability of orthotopic liver transplantation, this has become a viable option for those patients with FHF who are unlikely to survive with conservative treatment, although patient selection and timing of transplantation still presents a clinical dilemma.

Non-narcotic analgesics. Problems of overdosage

The first cases of fulminant hepatic failure due to paracetamol poisoning were reported in 1966, and in the United Kingdom this condition is now responsible for more cases of acute hepatic failure than any other cause. Adults account for the majority of serious and fatal cases of paracetamol poisoning and it is extremely rare for young children to ingest sufficient paracetamol to cause more than minimal liver damage. A single measurement of the plasma paracetamol concentration is an accurate predictor of liver damage provided that it is taken not earlier than 4 hours after ingestion of the overdose. Peak disturbance of liver function occurs 2 to 4 days after the overdose, often accompanied by mild jaundice, after which recovery is usually rapid and complete. In a few patients, fulminant hepatic failure, manifested by increasing jaundice and encephalopathy, may develop by the third to fifth day. Acute renal failure may complicate paracetamol poisoning, often in the context of severe liver damage. Renal failure, which is often non-oliguric, typically becomes apparent 24 to 72 hours after overdosage. The treatment of paracetamol intoxication should include gastric lavage, which has been shown to be of value for up to 6 hours after ingestion of a paracetamol overdose. Further general treatment may include parenteral fluid replacement and a prophylactic infusion of dextrose (5-10%) in patients at risk of hepatic failure. Specific protective agents in those patients at risk of paracetamol-induced liver damage include N-acetylcysteine and methionine which are most effective if given within 8 to 10 hours of ingestion of the overdose. Hepatic and renal failure should be managed conventionally. In recent years in the United Kingdom there has been a gradual decline in the number of hospital admissions and the number of deaths from aspirin poisoning. Salicylates in overdose directly stimulate the respiratory centre and so cause a respiratory alkalosis. Metabolic acidosis occurs in severe poisoning because of impairment of the oxidative metabolism of energy substrates. At very high salicylate concentrations respiratory depression may occur, possibly associated with neuroglycopenia, adding respiratory acidosis to the worsening metabolic acidosis. In addition to a mixed acid-base disturbance, hypokalaemia and hypoglycaemia may be present. Nausea and vomiting increase the fluid deficit. If dehydration is sufficiently severe, decreasing cardiac output may hasten development of lactic acidosis and acute renal failure.(ABSTRACT TRUNCATED AT 400 WORDS)

Toxicologically relevant disturbances of haemostasis

The normal haemostatic process depends on the normal function of and regular interaction between the vascular wall, the plasmatic coagulation system and the blood platelets. The consequences of interference of chemical compounds with haemostasis are bleeding tendency and bleeding, thrombophilia and thrombosis or disseminated intravascular coagulation. Examples will illustrate that chemicals interfering with haemostasis have different mechanisms and sites of action.

Quantitative liver function and morphology after paracetamol administration to rats

The functional status of the liver after paracetamol administration to rats was dissociated with regard to cytosolic and microsomal functions. The cytosolic function, measured as galactose elimination capacity, was unchanged even after high doses of paracetamol. The microsomal function, measured as the prothrombin time, was reversibly decreased to a minimum 12 h after paracetamol administration and showed dose dependence. The structural changes of the liver cells were centrilobular necroses and dilatation of the endoplasmic reticulum. They were most marked 36 h after paracetamol and were not correlated to the functional impairment. We conclude that during acute paracetamol induced liver damage to rats different functions of the liver are unequally influenced and that the structural changes occur later than the functional ones. The paracetamol intoxicated rat is a promising model for further investigation of dissociation of subcellular functions during acute liver damage.

Paracetamol

Paracetamol is an analgesic and antipyretic agent which was first marketed for use as a drug in the U.K. in 1956. It has since become popular with the medical profession and the general public as an alternative to aspirin.