Temporarily remove protein:

1. Discontinue all protein-containing feeds for no more than 24 hours to minimize nitrogen load and decrease ammonia accumulation. Avoid prolonged protein restriction to prevent negative nitrogen balance and catabolism.

Provide adequate energy to prevent catabolism and promote anabolism:

1. Provide 100-125% of estimated energy needs through a combination of carbohydrate and fat to prevent catabolism and promote anabolism.

2. Provide intravenous (IV) dextrose at an appropriate glucose infusion rate (e.g., 10 mg/kg/min in neonates) to support energy needs.

3. Consider adding IV lipid emulsion (ILE) at a rate of 1-3 g/kg/day to meet energy needs.

4. Initiate enteral or oral feeds, alone or in combination with parenteral feeds, as soon as possible.

Considerations for dialysis:

1. Provide adequate non-protein energy via parenteral and/or enteral nutrition during and post-dialysis to prevent catabolism and rebound hyperammonemia.

2. During and/or post dialysis, consider providing protein to compensate for losses and prevent rebound hyperammonemia. Reintroduce protein incrementally, starting at 50-75% of target intake and increasing by 25-50% per day, as tolerated.

Recommendations to gradually reintroduce protein following acute hyperammonemia:

1. Reintroduce protein incrementally, starting at 25-50% of target intake and increasing by 25-50% per day, as tolerated.

2. When reintroducing protein via enteral or oral feeds, consider initially using EAA-based medical food alone or in combination with intact protein to minimize protein load and replenish plasma EAA concentrations, particularly for neonates with severe presentation and for individuals consuming EAA-based medical food at baseline.

3. In neonates, reintroduce protein using human milk, if available, with or without EAA-based medical food. See Recommendation 2.3 for additional information.

Administer alternative pathway therapy in conjunction with medical providers:

1. Start nitrogen scavengers and IV L-arginine hydrochloride (except in ARG) to facilitate ammonia removal. 

2. For CIT-I and ASA, transition from IV L-arginine hydrochloride (approximately 200-400 mg/kg) to oral/enteral L-arginine supplementation. See Recommendation 4.3 for oral maintenance dosing. 

3. For OTC and CPS, transition from IV L-arginine hydrochloride (approximately 100-250 mg/kg) to oral/enteral L-citrulline supplementation to support nitrogen excretion. See Recommendation 4.3 for oral maintenance dosing. 

Laboratory Monitoring during Hyperammonemia:

1. Monitor blood ammonia every 2-4 hours to assess treatment response and guide urgent clinical decisions.

2. During protein reintroduction, monitor blood ammonia every 3-12 hours to ensure metabolic stability and guide the safe advancement of protein intake. 

3. Monitor plasma amino acids regularly, up to once daily, and no sooner than 24 hours after changing dietary treatment.

4. Monitor blood glucose and electrolytes frequently, with glucose checks up to every hour if insulin is administered to prevent hypoglycemia. 

Consider providing an individualized home feeding plan for mild illness that includes:

1. Reduce protein intake by up to 50%, generally for 24-48 hours, based on clinical status.

2. Increase energy intake by at least 10-20% using non-protein sources to maintain energy balance and prevent catabolism.

3. Increase fluid intake by 10-20% to ensure adequate hydration.

4. Continue prescribed amino acid supplements and nitrogen scavengers.

5. Family Education: (1) Provide information on monitoring for clinical signs and symptoms of hyperammonemia, including when to contact the on-call metabolic specialist and when to seek emergency care. (2) Advise family to contact metabolic clinic when illness occurs and to seek medical assistance if unable to tolerate oral/enteral feeds and fluids. See Recommendation 5.1 for additional information on nutrition education.

Strategies to Prevent a Hyperammonemic Crisis:

1. Diet and Medication Adherence: Evaluate and support close adherence to prescribed nutrition therapy, supplemental amino acids, and nitrogen scavengers.

2. Prompt Infection Management: Prioritize and incorporate treatment of the underlying illness or infection into the overall management plan. Provide adequate energy and nitrogen scavenging support to prevent metabolic decompensation.

3. Avoid Catabolic Triggers: Minimize prolonged fasting, stress, and medications (e.g., corticosteroids, valproate) that may promote catabolism and increase blood ammonia.

4. Establish Individualized Care Plans: Provide families with a detailed sick-day management plan (see Recommendation 1.7). Provide individualized letter or card with emergency instructions tailored to the individual's specific metabolic needs for paramedics and emergency staff. Advise families to contact their metabolic specialist if the individual presents to a hospital or emergency department.