Emergency Medicine · Year 3 · from Emergency Medicine

Case 1: Acetaminophen Overdose - The Silent Killer

Patient Demographics

  • Age: 19 years
  • Sex: Female
  • Occupation: College freshman

Chief Complaint

"I took a bunch of Tylenol last night and my roommate made me come in."

History of Present Illness

A 19-year-old female presents 14 hours after intentional ingestion of "a whole bottle" of extra-strength acetaminophen (500mg tablets, approximately 50 tablets = 25 grams). She reports taking them after a breakup with her boyfriend. Initially felt fine, developed nausea and vomiting 6 hours post-ingestion. Currently asymptomatic except for mild RUQ discomfort. She did not seek care earlier because she "felt okay."

Initial Assessment

ESI Level: 2 - Potentially toxic ingestion requiring emergent intervention

First Impression:

  • Appearance: Alert, anxious, tearful
  • Work of breathing: Normal
  • Circulation: Normal color

Vital Signs:

  • Heart rate: 88 bpm
  • Blood pressure: 118/72 mmHg
  • Respiratory rate: 16 breaths/min
  • SpO2: 99% on room air
  • Temperature: 37.0C
  • GCS: 15

Primary Survey

Airway: Patent Breathing: Normal respiratory effort Circulation: Normal pulses, well-perfused Disability: Alert and oriented, GCS 15 Exposure: No abnormalities

Key Point: Acetaminophen Toxicity Stages

StageTime Post-IngestionSymptoms
I0-24 hoursAsymptomatic or mild GI symptoms
II24-72 hoursRUQ pain, elevated LFTs, possible AKI
III72-96 hoursHepatic failure, coagulopathy, encephalopathy
IV4 days-2 weeksRecovery or death

This patient is in Stage I-II transition - deceptively well-appearing

Secondary Survey

SAMPLE History:

  • Symptoms: Mild nausea, RUQ discomfort
  • Allergies: None
  • Medications: Oral contraceptives
  • PMH: Depression (not currently in treatment)
  • Last Meal: Nothing since ingestion
  • Events: Intentional ingestion after emotional stressor

Ingestion Details:

  • Substance: Acetaminophen 500mg tablets
  • Amount: ~50 tablets (25 grams; ~400 mg/kg for 60kg patient)
  • Time: 14 hours ago
  • Co-ingestants: Denies alcohol or other medications
  • Vomiting: Yes, 2 episodes about 6 hours post-ingestion

Diagnostic Testing

Point-of-Care:

  • Glucose: 92 mg/dL
  • Urine pregnancy: Negative

Labs:

  • Acetaminophen level: 180 mcg/mL at 14 hours (TOXIC - above treatment line)
  • AST: 1,842 IU/L (markedly elevated)
  • ALT: 2,156 IU/L (markedly elevated)
  • INR: 1.8
  • Total bilirubin: 2.1
  • BUN/Cr: 18/0.9
  • Lipase: Normal
  • Salicylate level: Undetectable
  • Ethanol: Negative
  • Urine drug screen: Negative

Rumack-Matthew Nomogram:

  • Plot acetaminophen level against time
  • At 14 hours, 180 mcg/mL is well above treatment line
  • N-acetylcysteine (NAC) indicated

Diagnosis

Acute acetaminophen toxicity with early hepatotoxicity

Management

N-Acetylcysteine (NAC) Protocol:

IV Protocol (21-hour):

  • Loading: 150 mg/kg in 200mL D5W over 1 hour
  • Dose 2: 50 mg/kg in 500mL D5W over 4 hours
  • Dose 3: 100 mg/kg in 1000mL D5W over 16 hours

Monitoring:

  • Serial acetaminophen levels (should decline)
  • Serial LFTs every 6-12 hours
  • INR monitoring
  • Renal function

Additional Treatment:

  • IV fluids for hydration
  • Antiemetics for nausea (NAC can cause nausea)
  • Electrolyte repletion as needed

Psychiatry Consultation:

  • Mandatory for intentional overdose
  • 1:1 observation until cleared
  • Safety planning

Clinical Course

Labs at 24 hours:

  • Acetaminophen: 28 mcg/mL (declining)
  • AST: 3,456 IU/L (peak expected 48-72 hours)
  • ALT: 4,122 IU/L
  • INR: 2.4
  • Creatinine: 1.0

Labs at 48 hours:

  • Acetaminophen: <10 mcg/mL
  • AST: 2,100 IU/L (improving)
  • ALT: 2,850 IU/L (improving)
  • INR: 1.6 (improving)

Decision: Continue NAC until:

  • Acetaminophen undetectable AND
  • INR <2.0 AND
  • AST/ALT declining AND
  • Patient clinically improved

Disposition

  • Medical admission with 1:1 observation
  • NAC continued for 48 hours total
  • LFTs improving, INR normalizing
  • Psychiatry evaluation: Patient engaged, safety plan established
  • Discharged to psychiatric facility on day 4 for further stabilization

Teaching Points

  1. Acetaminophen is deceptively dangerous: Patients may appear well in Stage I while developing fatal hepatotoxicity
  2. Know the toxic dose: >150 mg/kg is potentially toxic; >300 mg/kg severe
  3. Time matters: NAC most effective within 8 hours; still beneficial up to 24+ hours
  4. Don't rely on symptoms: Early acetaminophen toxicity is asymptomatic
  5. Rumack-Matthew nomogram: Only valid for single acute ingestions 4-24 hours post-ingestion
  6. Extended NAC: Continue until patient improving, not based on fixed protocol duration
  7. Always consider co-ingestion: Check salicylate level, ethanol, and urine drug screen
  8. Psychiatric evaluation mandatory: All intentional overdoses require mental health assessment

Clinical Image

Image Description: The Rumack-Matthew nomogram showing acetaminophen plasma concentration plotted against hours post-ingestion. The treatment line indicates when N-acetylcysteine therapy is indicated based on acetaminophen level and time.

Attribution: Image adapted from Wikimedia Commons, Rumack-Matthew Nomogram. Public domain. Source: https://commons.wikimedia.org/wiki/File:Rumack-Matthew_nomogram.svg

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