What is the treatment for hyperammonemia?

Treatment of Hyperammonemia with Ammonia Level of 198

For a patient with an ammonia level of 198 μmol/L, immediate initiation of both medical therapy with lactulose and nitrogen-scavenging agents is strongly recommended, with preparation for continuous kidney replacement therapy (CKRT) if rapid clinical deterioration occurs. 1

Initial Medical Management

1. Stabilize the patient:

   • Ensure adequate circulation, airway, and breathing
   • Monitor vital signs and blood glucose levels
   • Establish intravenous access
   • Consider intubation if neurological status is deteriorating
   • Start rehydration with dextrose-containing fluids 2

2. First-line pharmacological therapy:

   • Lactulose: Start immediately at 25-30 mL orally every 1-2 hours until bowel movements occur, then adjust to maintain 2-3 soft bowel movements daily
     • Lactulose reduces blood ammonia levels by 25-50%, which typically parallels improvement in mental status 3
   • Temporary protein restriction: Stop protein intake initially to reduce ammonia production 1
   • Intravenous glucose and lipids: Administer to prevent catabolism 2

3. Second-line pharmacological therapy:

   • Rifaximin: 550 mg orally twice daily
     • Particularly effective when used in combination with lactulose 4
   • Nitrogen-scavenging agents: For ammonia levels >150 μmol/L
     • Sodium benzoate and sodium phenylacetate provide alternative routes for nitrogen excretion 2, 1

Monitoring and Escalation of Care

1. Monitor plasma ammonia levels every 3 hours 2

2. Perform frequent neurological assessments for signs of encephalopathy:

   • Lethargy
   • Confusion
   • Asterixis
   • Deteriorating mental status 1

3. Indications for escalation to CKRT:

   • Ammonia level >400 μmol/L refractory to medical management
   • Rapidly deteriorating neurological status despite medical therapy
   • Development of coma or cerebral edema 1

Special Considerations

1. Reintroduce protein within 48 hours after ammonia levels decrease to 80-100 μmol/L to avoid catabolism 2

2. Poor prognostic factors to monitor for:

   • Hyperammonemic coma lasting >3 days
   • Increased intracranial pressure
   • Ammonia levels >1,000 μmol/L 2

3. Common pitfalls to avoid:

   • Relying solely on ammonia levels without clinical correlation
   • Inadequate monitoring of ammonia levels
   • Underestimating rebound hyperammonemia
   • Overuse of lactulose leading to dehydration and electrolyte abnormalities 1
   • Delayed initiation of therapy, as duration of hyperammonemic coma is the most important prognostic factor 1

4. Proper blood sampling technique for accurate ammonia measurement:

   • Use EDTA or lithium heparin tube
   • Transport on ice to laboratory
   • Process within 15 minutes of collection 2, 1

Long-term Management

Once ammonia levels have normalized:

1. Transition to oral therapy with maintenance doses of lactulose
2. Consider oral sodium phenylbutyrate for chronic management
3. Implement dietary management with appropriate protein restrictions
4. Identify and treat the underlying cause of hyperammonemia 1

The key to successful management of hyperammonemia is prompt recognition and immediate treatment, as delays can lead to irreversible brain damage and poor neurological outcomes. The level of 198 μmol/L indicates significant hyperammonemia requiring aggressive medical management with close monitoring and preparation for dialysis if clinical deterioration occurs.