What is the workup for a 2-year-old with acute acetaminophen (Tylenol) ingestion?

Workup for Acute Acetaminophen Ingestion in a 2-Year-Old

For a 2-year-old with acute acetaminophen ingestion, obtain a serum acetaminophen level at 4 hours post-ingestion or as soon as possible thereafter, and refer to the emergency department if the ingested dose is unknown or ≥200 mg/kg. 1

Initial Assessment

• Determine the time of ingestion, amount ingested, formulation (immediate or extended-release), and whether it was a single or multiple ingestion 1
• Assess for any signs of acetaminophen toxicity including vomiting, right upper quadrant abdominal tenderness, or mental status changes 1
• Calculate the mg/kg dose based on the child's weight and the estimated amount ingested 1
• Document any co-ingestants that might have been taken simultaneously 1

Triage Decision

• For children under 6 years of age:

  • Refer to emergency department if the estimated ingestion is ≥200 mg/kg or unknown 1
  • Can be observed at home if the dose ingested is <200 mg/kg 1

• For repeated supratherapeutic ingestions in children under 6 years:

  • Refer to emergency department immediately if they have ingested:
    • ≥200 mg/kg over a single 24-hour period, or
    • ≥150 mg/kg per 24-hour period for the preceding 48 hours, or
    • ≥100 mg/kg per 24-hour period for the preceding 72 hours or longer 1

Laboratory Testing

• Obtain serum acetaminophen concentration at 4 hours post-ingestion or as soon as possible thereafter 1
• Plot the level on the Rumack-Matthew nomogram to determine risk for hepatotoxicity 2
• Obtain baseline liver function tests (AST, ALT), renal function tests (BUN, creatinine), and coagulation studies (PT/INR) 3
• Consider obtaining a complete blood count and electrolytes 3

Treatment Considerations

• If the patient presents within 1-2 hours of ingestion, consider activated charcoal if local protocols support its use 1

• Administer N-acetylcysteine (NAC) if:

  • The acetaminophen level plots above the treatment line on the Rumack-Matthew nomogram 2, 4
  • The time of ingestion is unknown and there is clinical evidence of acetaminophen toxicity 4
  • The acetaminophen concentration cannot be obtained within 8 hours of ingestion 4

• NAC dosing for pediatric patients:

  • Total dosage is 300 mg/kg given intravenously as 3 separate doses over 21 hours 4
  • Loading dose: 150 mg/kg
  • Followed by 50 mg/kg over 4 hours
  • Then 100 mg/kg over 16 hours 4

Special Considerations

• For extended-release formulations, consider obtaining a second acetaminophen level 4-6 hours after the first to ensure the peak concentration has been captured 1
• If the initial contact with healthcare occurs more than 36 hours after ingestion and the patient appears well, further evaluation for acetaminophen toxicity may not be necessary 1
• None of the pediatric patients receiving intravenous NAC in clinical studies developed hepatotoxicity, while some not receiving NAC did develop liver injury 4

Monitoring

• For patients receiving NAC, monitor for hypersensitivity reactions including hypotension, wheezing, shortness of breath, and bronchospasm 4
• For patients with elevated acetaminophen levels, monitor liver function tests every 12-24 hours until improving 3
• Continue NAC treatment if there is evidence of hepatotoxicity (elevated transaminases) even after the initial 21-hour course 4

Common Pitfalls to Avoid

• Delaying NAC administration while waiting for acetaminophen levels if presentation is >8 hours post-ingestion 4
• Failing to recognize that the Rumack-Matthew nomogram only applies to single acute ingestions with a known time of ingestion 2
• Not considering that repeated supratherapeutic ingestions require different management approaches than single acute overdoses 3
• Underestimating the potential for severe hepatotoxicity in pediatric patients with significant acetaminophen ingestion 5