Is trending ammonia levels necessary in managing hepatic encephalopathy?

Routine Ammonia Level Trending is Not Recommended in Hepatic Encephalopathy Management

Routine measurement and trending of ammonia levels is not recommended in the management of hepatic encephalopathy (HE). 1, 2

Rationale Against Routine Ammonia Testing

The 2024 American Association for the Study of Liver Diseases (AASLD) practice guidance explicitly states that routine ammonia level testing in patients with cirrhosis and altered mental status is not recommended 1. This recommendation is supported by several key factors:

• Ammonia levels are highly variable within patients and laboratories
• Elevated ammonia levels may occur in non-HE conditions
• Ammonia testing does not guide clinical management decisions 3
• There is no correlation between ammonia levels and lactulose dosing in clinical practice 3

Clinical Value of Ammonia Testing

While routine testing is discouraged, ammonia levels may have limited utility in specific scenarios:

• Negative predictive value: A low ammonia level in patients with coma or confusion should prompt investigation of etiologies other than HE 1, 2
• Proper collection technique is critical when ammonia measurement is deemed necessary:
  • Patient should be fasting
  • Avoid venous stasis during collection
  • Use EDTA-containing tube
  • Immediate placement on ice
  • Rapid transport to laboratory (within 60-90 minutes) 2

Diagnostic Approach to Hepatic Encephalopathy

HE diagnosis should be based on:

1. Clinical criteria: Using the West Haven criteria and Glasgow Coma Scale 1, 2

   • West Haven criteria for temporal disorientation (grades >2)
   • Glasgow Coma Scale for grades III-IV

2. Exclusion of other causes of altered mental status, particularly for:

   • First episode of altered mental status
   • Presentations with seizures or new focal neurological signs
   • Unsatisfactory response to therapy 1

3. Brain imaging considerations:

   • Not routinely warranted for presentations similar to prior HE episodes
   • Consider for first episode, seizures, focal signs, or poor response to therapy 1

Management Approach

Treatment decisions should be based on clinical presentation rather than ammonia levels:

1. Identify and address precipitating factors 1, 2:

   • Infections
   • GI bleeding
   • Electrolyte disorders
   • Acute kidney injury
   • Dehydration
   • Constipation
   • Medication issues (lactulose under/overuse, CNS depressants)

2. Empiric therapy 1, 4:

   • Lactulose (oral or rectal) as first-line therapy
   • Goal: Improvement in mental status while monitoring electrolytes
   • Consider polyethylene glycol as an alternative, especially with ileus
   • Rifaximin as an add-on therapy for prevention of recurrent episodes

Common Pitfalls to Avoid

• Overreliance on ammonia levels: Studies show that ammonia levels do not influence management decisions or improve outcomes 3, 5
• Technical errors in ammonia measurement: Improper collection and handling can lead to falsely elevated levels 2
• Neglecting clinical assessment: HE remains a clinical diagnosis that requires thorough evaluation of mental status and exclusion of other causes 1, 2
• Delaying treatment while waiting for ammonia results: Empiric therapy should be initiated based on clinical suspicion 1

Algorithm for HE Management Without Ammonia Trending

1. Assess mental status using West Haven criteria and Glasgow Coma Scale
2. Consider ICU admission for Grades 3 and 4 HE
3. Investigate and treat precipitating factors
4. Initiate empiric therapy with lactulose (oral or rectal)
5. Consider brain imaging only for first episodes, focal signs, or poor response
6. Monitor clinical response rather than ammonia levels

By following this evidence-based approach, clinicians can provide optimal care for patients with hepatic encephalopathy without unnecessary ammonia testing.