When to check ethanol and acetaminophen levels in a patient with new onset seizures and headaches?

Ethanol and Acetaminophen Levels in New Onset Seizures and Headaches

In patients presenting with new onset seizures and headaches, both ethanol and acetaminophen levels should be checked routinely as part of the initial laboratory evaluation, especially when the etiology is unclear or substance ingestion is suspected. 1

Rationale for Testing

Ethanol Testing

• Ethanol-related seizures are common in emergency settings:
  • Seizures can occur during acute intoxication or withdrawal
  • In one study, 58% of patients with suspected alcohol withdrawal seizures had abnormal CT findings, with 6% showing clinically significant lesions 1
  • Even in patients with normal neurological examinations and no signs of head trauma, management changed in a significant number of cases due to abnormal findings

Acetaminophen Testing

• Acetaminophen overdose is a leading cause of acute liver failure
• Testing is essential because:
  • History of ingestion is often inaccurate or unknown
  • Patients may not disclose ingestion
  • Very high aminotransferases (>3,500 IU/L) strongly correlate with acetaminophen poisoning 1
  • Early treatment with N-acetylcysteine (NAC) significantly improves outcomes

Clinical Algorithm for Testing

When to Check Both Levels:

1. All patients with new-onset seizures when:

   • Etiology is unclear
   • Patient has altered mental status
   • History is limited or unreliable
   • There's any suspicion of substance ingestion

2. Specific indications for ethanol level:

   • History of alcohol use
   • Clinical signs of intoxication or withdrawal
   • Unexplained metabolic acidosis or osmolar gap
   • Seizures with no prior seizure history 1, 2

3. Specific indications for acetaminophen level:

   • Any suspicion of overdose (intentional or unintentional)
   • Unexplained elevated liver enzymes
   • Headache in conjunction with seizures (may be NAC-related or acetaminophen toxicity) 3
   • Even if history is negative, as acetaminophen is the leading cause of ALF 1

Timing Considerations

• Acetaminophen levels: Obtain at least 4 hours post-ingestion for accurate assessment 4

  • Earlier levels may be misleading and not represent peak concentration
  • If time of ingestion is unknown, obtain level immediately and start NAC while awaiting results

• Ethanol levels: Obtain as soon as possible

  • Levels decline at approximately 15-20 mg/dL/hour in non-tolerant individuals
  • Withdrawal seizures typically occur 24-48 hours after last drink

Additional Testing to Consider

In patients with new-onset seizures and headaches, also consider:

1. Basic metabolic panel:

   • Glucose (hypoglycemia can cause seizures) 5
   • Sodium (hyponatremia can cause seizures) 1

2. Toxicology screen:

   • Consider in first-time seizure patients, though routine use has limited evidence 1
   • Particularly important when cocaine or stimulant use is suspected

3. Head CT scan:

   • Indicated in new-onset seizures, especially with headache
   • 22% of patients with first-time seizure and normal neurologic examination had abnormal CT findings 1

Management Implications

• Positive acetaminophen level:

  • Use Rumack-Matthew nomogram to determine need for NAC treatment
  • Start NAC immediately if level is above "possible toxicity" line or if >8 hours since ingestion 4
  • NAC dosing: 150 mg/kg loading dose, followed by 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours 1

• Positive ethanol level:

  • Monitor for withdrawal symptoms
  • Consider benzodiazepines for seizure prophylaxis if withdrawal is suspected
  • Evaluate for other alcohol-related complications

Common Pitfalls to Avoid

1. Relying solely on patient history for acetaminophen ingestion - histories are often inaccurate 4

2. Waiting for symptoms of hepatotoxicity before checking acetaminophen levels - early treatment is critical

3. Attributing seizures to alcohol withdrawal without checking for other causes - even alcoholics can have other etiologies for seizures

4. Missing acetaminophen toxicity in patients with seizures - headache can be both a symptom of toxicity and a side effect of NAC treatment 3

5. Failing to check glucose in patients with seizures - hypoglycemia is a readily treatable cause 5

By systematically evaluating for both ethanol and acetaminophen in patients with new-onset seizures and headaches, clinicians can identify treatable causes and prevent serious complications.