Treatment of Hyperammonemia

Immediate Stabilization

The American College of Physicians recommends immediately stopping all protein intake, securing the airway with intubation if neurological status is deteriorating, and initiating aggressive caloric support with IV dextrose and lipids while preparing for hemodialysis or continuous kidney replacement therapy (CKRT) if ammonia levels exceed 300-400 μmol/L or if the patient shows signs of encephalopathy 1, 2
Airway and hemodynamic management takes priority, with securing airway, breathing, and circulation, and intubating immediately if consciousness is declining or coma is present 3, 1
Establishing IV access for fluid and medication administration is crucial 3
Beginning high-rate infusion of dextrose-containing fluids to prevent catabolism is recommended 4, 3

Providing ≥100 kcal/kg/day through IV dextrose and lipids is essential 3, 1, 2
Maintaining glucose infusion rate of 8-10 mg/kg/min to prevent protein breakdown is necessary 3, 1, 2
Starting IV lipids at 0.5 g/kg/day, titrating up to 3 g/kg/day for additional calories is recommended 3, 1, 2
Protein restriction must not exceed 48 hours, and protein should be reintroduced gradually once ammonia decreases to 80-100 μmol/L to avoid catabolism 5, 1, 2

Administering nitrogen-scavenging agents when ammonia exceeds 150 μmol/L is recommended, with sodium benzoate and sodium phenylacetate being options 2
L-arginine hydrochloride dosing depends on the specific urea cycle disorder, with 200 mg/kg for ornithine transcarbamylase (OTC) and carbamoyl phosphate synthetase (CPS) deficiencies, and 600 mg/kg for argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) deficiencies 2
L-carnitine may be considered in organic acidemias, with a loading dose of 50 mg/kg over 90 minutes, then 100-300 mg/kg daily 1, 2

Initiating KRT immediately when ammonia levels exceed 300-400 μmol/L despite medical therapy, or when there is rapidly deteriorating neurological status or coma, is recommended 5, 1, 2
High-dose continuous venovenous hemodialysis (CVVHD) is first-line when available, with a blood flow rate of 30-50 mL/min and dialysis fluid flow rate/Qb ratio >1.5 2
Intermittent hemodialysis (HD) is the most effective for rapid ammonia reduction, achieving 95-96% ammonia filtration fraction, and reducing ammonia by 50% within 1-3 hours 1, 2
CKRT is preferred for hemodynamically unstable patients, with a success rate of 60% in pediatric studies 5, 1

Ammonia levels must be checked every 3-4 hours until normalized, with critical sampling technique to avoid false elevations 3, 1, 2
Collecting from free-flowing venous or arterial blood, using lithium heparin or EDTA tube, and transporting on ice and processing within 15 minutes is essential 5, 2, 3
Assessing neurological status regularly for signs of encephalopathy, monitoring electrolytes closely, especially during CKRT, and tracking blood glucose levels continuously is necessary 3, 2, 1

The duration of hyperammonemic coma is the most important prognostic factor, not the rate of ammonia clearance, with coma lasting >3 days predicting poor neurological outcome 2, 5
Peak ammonia levels, with levels >1,000 μmol/L associated with severe brain damage, are also a critical factor 5
Delayed recognition and treatment leads to irreversible neurological damage, including seizures, coma, and death, making prompt identification and treatment imperative 2, 5