In chronic ingestions, the treatment nomogram cannot be used. Laboratory testing for serum acetaminophen concentration and liver function should be obtained for any at-risk patient. Patients with evidence of liver injury (AST greater than two times normal or greater than 120 IUL or those with serum acetaminophen levels greater than 30 mcg/mL should have antidotal therapy initiated. (5,6)
Gastric decontamination with activated charcoal is recommended in all pediatric patients who present within four hours of acetaminophen ingestion. Contraindications include gastrointestinal obstruction or any altered mental status in which airway protection is a concern. Endotracheal intubation should not be performed solely for the purpose of giving activated charcoal. Activated charcoal has not been shown to reduce acetaminophen absorption when given greater than four hours after ingestion and is not recommended in this time frame. Activated charcoal is given as a single dose of 1 g/kg by mouth (maximum 50 g). (8,9)
Once the need for N-acetylcysteine antidotal therapy is determined, it should be given as soon as possible. When given within 8 hours of ingestion, the mortality rate approaches 0; however, NAC may be beneficial up to 24 hours after ingestion. NAC should be given intravenously (IV) if available; however, providers should be aware that IV NAC can cause severe anaphylactoid reactions. Preparations should be made for immediate interventions if anaphylaxis occurs, and patients should be monitored closely during the initial 30 minutes of the infusion. (6,10) Providers should also be aware that prothrombin time and INR can be artificially elevated by NAC, which can obscure signs of worsening liver function. (11)
A well-established protocol for IV NAC dosing involves a 21-hour administration procedure detailed below. Repeat acetaminophen levels, liver function tests, and INR should be repeated 9 hours into the protocol. (12,13)
Loading dose of 150 mg/kg IV (maximum 15,000 mg) in 200 mL dextrose 5% in water (D5W) infused over 60 minutes
First maintenance dose of 50 mg/kg IV (maximum 5,000 mg) in 500 ml D5W infused over 4 hours
Second maintenance dose of 100 mg/kg IV (maximum 10,000 mg) in 1000 mL D5W infused over 16 hours
Poor prognostic indicators for liver function include the King’s College Criteria. Patients with acidosis with pH < 7.3 or patients with the combination of prothrombin time > 100 seconds and creatinine > 3.3 mg/dL and hepatic encephalopathy grade III – IV (marked confusion or coma) are considered high risk for fulminant liver failure and should be transferred to a liver transplant center. (14)
Given that the patient had an elevated acetaminophen level greater than 30 mcg/mL with multiple ingestions over the last 48 hours, she was treated with N-acetylcysteine. Labs were rechecked at 19 hours after initiation of NAC. Liver function tests and INR were stable. Repeat acetaminophen level was < 10 mcg/mL. She was ultimately discharged after Psychiatric evaluation with a home safety plan and outpatient Psychiatry follow up.
Faculty Reviewer: Dr. Jane Preotle
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