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Table 4 Levels of hyperammonemia and suggested actions in symptomatic patients Grade of recommendation, C-D

From: Suggested guidelines for the diagnosis and management of urea cycle disorders

Ammonia level (μmol/L) Action in undiagnosed patient Action in known UCD patient Comments
Above upper limit of normal ▪ Stop protein intake ▪ Stop protein intake ▪ Stop protein for 24 h (maximum 48 h)
  ▪ Give IV glucose at an appropriate dosage to prevent catabolism (10mg/kg/min in a neonate) ± insulina ▪ Give IV glucose at an appropriate dosage to prevent catabolism (10mg/kg/min in a neonate) ± insulina ▪ Avoid exchange transfusions as they cause catabolism
  ▪ Monitor blood ammonia levels every 3 h ▪ Monitor blood ammonia levels every 3 h ▪ Hyperglycemia can be extremely dangerous (hyperosmolarity)
In addition    
if >100 and <250 (in neonates, >150 and <250) ▪ Start drug treatment with IV L-arginine and nitrogen scavengers (see Table5) ▪ Continue drug treatment with L-arginine (plus continue or add L-citrulline for NAGSD, CPS1D or OTCD) and sodium benzoate ± sodium phenylbutyrate/ phenylacetateb (see Table5), increase dose or give IV ▪ If major hyperglycemia occurs with high lactate (>3mmol/L) reduce glucose infusion rate rather than increase insulin
  ▪ Start carbamylglutamate, carnitine, vitamin B12, biotin (see Table5 and its legend) ▪ Consider nasogastric carbohydrate and lipid emulsions unless the child is vomiting (enables higher energy intake) ▪ Avoid hypotonic solutions
In addition    
if 250 to 500 ▪ As above ▪ As above, but all drugs per IV ▪ Add sodium and potassium according to the electrolyte results
  ▪ Prepare hemo(dia)filtration if significant encephalopathy and/or early high blood ammonia level or very early onset of disease (day 1 or 2) ▪ Prepare hemo(dia)filtration if significant encephalopathy and/or early high blood ammonia level or very early onset of disease (day 1 or 2) ▪ Take into account the sodium intake if sodium benzoate or sodium PBA are used c
  ▪ Begin hemo(dia)filtration if no rapid drop of ammonia within 3–6 h ▪ Begin hemo(dia)filtration if no rapid drop of ammonia within 3–6 h ▪ L-arginine not to be given in ARG1D
In addition    
if 500 to 1000 ▪ As above ▪ As above ▪ Some concerns of sodium benzoate use in organic acidemias
  ▪ Start hemo(dia)filtration immediately ▪ Start hemo(dia)filtration as fast as possible ▪ Avoid repetitive drug boluses
In addition    
if >1000 ▪ Evaluate whether to continue specific treatment or to start palliative care ▪ Evaluate whether to aim at curative treatment or at palliative care ▪ Monitor phosphate levels and supplement early specially with hemodialysis
  1. a Monitor blood glucose after 30 min and subsequently every hour, because some neonates are very sensitive to insulin.
  2. b If available, an IV equimolar solution of sodium benzoate and sodium phenylacetate can be used: 250mg/kg as bolus IV/90-120 min, then 250mg/kg as continuous IV infusion over 24h.
  3. c Sodium content in 1 gram of sodium benzoate or sodium phenylbutyrate, 7 mmol and 5.4 mmol, respectively.