A 22-year-old woman is evaluated in the intensive care unit for ongoing management of acetaminophen toxicity. She presented to the emergency department 4 hours after an intentional ingestion of an unknown quantity of acetaminophen, at which time her serum acetaminophen level was 180 µg/mL. She was promptly started on a standard 21-hour intravenous N-acetylcysteine (NAC) protocol. She is currently asymptomatic, denies nausea or abdominal pain, and is tolerating oral intake. She is currently at the 20th hour of the NAC infusion.
Laboratory results drawn 1 hour ago (at hour 19 of the infusion) show:
| Laboratory Test | Current Result | Admission Result |
|---|---|---|
| Acetaminophen | < 10 µg/mL | 180 µg/mL |
| Aspartate aminotransferase (AST) | 850 U/L | 45 U/L |
| Alanine aminotransferase (ALT) | 920 U/L | 50 U/L |
| Total bilirubin | 1.1 mg/dL | 0.8 mg/dL |
| INR | 1.1 | 1.0 |
| Creatinine | 0.8 mg/dL | 0.8 mg/dL |
Which of the following is the most appropriate next step in management?
- Continue intravenous N-acetylcysteine at the current maintenance rateAnswer
- BDiscontinue intravenous N-acetylcysteine and transition to oral N-acetylcysteine
- CDiscontinue intravenous N-acetylcysteine and recheck transaminases in 12 hours
- DConsult hepatology for urgent liver transplantation evaluation
- EAdminister fresh frozen plasma and continue intravenous N-acetylcysteine
Answer
Continue intravenous N-acetylcysteine at the current maintenance rate
The decision to discontinue N-acetylcysteine (NAC) therapy following the standard 21-hour intravenous protocol requires all of the following criteria to be met: the patient must be clinically asymptomatic, the serum acetaminophen concentration must be undetectable, the INR must be less than 1.5, and the serum transaminases (AST and ALT) must be normal or clearly trending downward. Although this patient's acetaminophen level is undetectable and her INR is normal, her transaminases have increased significantly since admission and have not yet demonstrated a downward trend. Therefore, the NAC infusion must be continued at the maintenance rate (6.25 mg/kg/hr) beyond the initial 21 hours. The infusion should be maintained, and laboratory values should be rechecked every 12 hours until the transaminases peak and begin to definitively decline.
Step-by-Step Solution
Key Concept
Evaluation of criteria for discontinuing N-acetylcysteine therapy in acetaminophen toxicity