What is the treatment for a patient with hyperammonemia?

Treatment for Hyperammonemia (Ammonia Level of 155)

For a patient with hyperammonemia (ammonia level of 155 μmol/L), immediate initiation of Continuous Kidney Replacement Therapy (CKRT) is recommended as the primary treatment due to the high ammonia level and risk of neurological deterioration. 1

Initial Management

Dialysis Therapy

• For ammonia level >150 μmol/L with risk of neurological deterioration:
  • Initiate CKRT as first-line treatment 1
  • Target clearance rates ≥2,500 ml/1.73 m²/h for high-dose CKRT
  • If patient is hemodynamically stable, intermittent hemodialysis can be used as an alternative for rapid ammonia clearance (can decrease blood ammonia by 75% within 3-4 hours) 1

Pharmacological Interventions

• Administer nitrogen-scavenging agents:

  • Sodium benzoate: 250 mg/kg for body weight <20 kg or 5.5 g/m² for body weight >20 kg (maximum 12 g daily)
  • Sodium phenylacetate: Same dosing as sodium benzoate 1
  • Continue these agents during dialysis to prevent rebound hyperammonemia

• Lactulose therapy:

  • Oral or rectal administration reduces blood ammonia levels by 25-50% 2, 3
  • Clinical response observed in approximately 75% of patients
  • Mechanism: Acidifies colonic contents, trapping ammonia as ammonium ions and preventing absorption 2

Monitoring and Assessment

• Measure ammonia levels at 24 hours and 5-7 days 1
• Assess neurological status using Glasgow Coma Scale
• Monitor for complications of dialysis:
  • Electrolyte imbalances
  • Hemodynamic instability
  • Rebound hyperammonemia

Supportive Care

• Nutritional management:

  • Temporarily withdraw protein during acute phase
  • Reintroduce protein within 48 hours after ammonia levels decrease to 80-100 μmol/L
  • Provide adequate calories (≥100 kcal/kg daily) as intravenous glucose and lipids 1

• Maintain hemodynamic stability:

  • Ensure adequate volume replacement
  • Use vasopressors if needed (dopamine, epinephrine, norepinephrine)
  • Correct electrolyte abnormalities, particularly glucose, potassium, magnesium, and phosphate 1

Treatment Duration and Discontinuation

• Continue treatment until clinical improvement is observed:
  • Improved mental status
  • Resolution of neurological symptoms
  • Adequate reduction in ammonia levels
  • Hemodynamic stability 1

Important Considerations

• Pitfalls to avoid:

  1. Delaying treatment initiation - immediate action is critical to prevent neurological damage
  2. Inadequate monitoring for rebound hyperammonemia after intermittent hemodialysis
  3. Failure to continue nitrogen-scavenging agents during dialysis
  4. Improper blood sampling technique for ammonia measurement (use EDTA or lithium heparin tube, transport on ice, process within 15 minutes) 1

• Prognostic factors:

  • Duration of hyperammonemic coma (>3 days is poor prognosis)
  • Plasma ammonia levels (>1,000 μmol/L indicates poor prognosis)
  • Increased intracranial pressure 1

While ammonia levels are crucial for diagnosis and treatment decisions, it's worth noting that some research suggests they don't always guide clinical management in hepatic encephalopathy specifically 4. However, with an ammonia level of 155 μmol/L, which exceeds the critical threshold of 150 μmol/L, CKRT initiation is clearly indicated according to current guidelines 1.