Hemodialysis for acetaminophen detoxification

Massive acetaminophen ingestion with early metabolic acidosis and coma: treatment with IV NAC and continuous venovenous hemodiafiltration

CONTEXT

We report the extraction of acetaminophen by continuous venovenous hemodiafiltration (CVVHD) during treatment of an acute ingestion of 200 g with a peak recorded serum acetaminophen level of 1,614 mg/L (10,652 micromol/L).

CASE DETAILS

The patient presented with early onset of coma, metabolic acidosis, and hypotension in the absence of significant hepatic injury. In addition to N-acetylcysteine (NAC) therapy, CVVHD was performed to manage the acid-base disturbance. Flow rate, effluent volume, and serum and effluent drug concentrations were obtained at hourly intervals. During 16 h of CVVHD the acetaminophen level dropped from 1,212 to 247 mg/L.

DISCUSSION

The average clearance of acetaminophen by CVVHD was 2.53 L/h, with removal of 24 g of acetaminophen over 16 h. As NAC is effective in preventing hepatic injury after acute acetaminophen overdose, the role of dialysis or CVVHD is limited.

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)

Acetaminophen and its toxicity

Acetaminophen (APAP) is considered one of the safest of all minor analgesics, but when taken in large doses (greater than 10 g) toxicity occurs. Severely poisoned patients experience hepatic and/or renal failure. The major metabolic pathway of APAP is formation of glucuronide and sulfate conjugates. A minor pathway is formation of a reactive metabolite that conjugates with glutathione (GSH). When GSH is depleted, the reactive metabolite causes necrosis of hepatic and other tissues. Treatment of APAP toxicity involves supplying alternate sulfhydryl donors or inhibiting oxidative formation of the reactive metabolite. Estimation of plasma APAP levels is necessary for effective treatment.