eMedicine Specialties > Neurology > Neurotoxicology

Hyperammonemia: Follow-up

Author: Elena Crisan, MD, Consulting Staff, Department of Neurology, Edwards Hines Veterans Affairs Hospital
Coauthor(s): Jasvinder Chawla, MBBS, MD, MBA, Chief of Neurology, Hines Veterans Affairs Hospital; Associate Professor and Director, Neurology Residency Training Program, Loyola University Medical Center
Contributor Information and Disclosures

Updated: Aug 20, 2009

Follow-up

Further Inpatient Care

Patients usually can go back to their dietary regimen and oral medications in 3-4 days. They should be admitted to an intensive care unit initially, and their neurologic status should be monitored carefully.

Further Outpatient Care

Outpatient care involves monitoring growth and development of the child that would indicate the adequacy of treatment. Additionally, periodic fasting levels of the following should be determined:

  • Plasma ammonium
  • Plasma glutamine (should be maintained at <1000 µmol/L)
  • Arginine
  • Total protein

Inpatient & Outpatient Medications

  • Sodium phenylbutyrate: Patients with CPS, OTC, or AS deficiency should receive sodium phenylbutyrate at a dose of 450-600 mg/kg/day.
  • Citrulline: Neonates with CPS or OTC deficiency should receive 0.17 g/kg/day of citrulline as a source of arginine.
  • Arginine: Patients with AS or AL deficiency should receive 400-700 mg/kg/day of arginine.

Transfer

Patients should be transferred to a facility having a neonatal or pediatric intensive care unit.

Deterrence/Prevention

  • Parents should be educated to take the symptoms of hyperammonemia (ie, lethargy, vomiting, changes in behavior) very seriously. They should contact their physician immediately at the onset of these symptoms. Following dietary recommendations and compliance with medications decreases the frequency of hyperammonemic episodes.
  • Antenatal diagnosis of urea cycle disorders can be made using several laboratory techniques. Families should be informed about the availability of these tests if they have had an affected infant or if the mother is a carrier of OTC mutation.

Complications

  • Cerebral edema
  • Cortical blindness

Prognosis

  • In a recent study of patients with urea cycle defects in Japan, the 5-year survival rate was 22% for the neonatal-onset group and 41% for the late-onset group. Among the survivors of the neonatal-onset group, 90% had moderately severe to severe neurologic deficits, whereas 28% of the survivors of the late-onset group had similar problems.
  • In another study, a group of 21 patients with neonatal hyperammonemia was monitored over long term. Duration of coma was the only reliable sign influencing the short-term outcome. Among the 13 survivors, only 3 had a normal/borderline outcome as far as neurocognitive development was concerned.

Patient Education

See Deterrence/Prevention.

Miscellaneous

Medicolegal Pitfalls

  • Plasma ammonium must be checked in a neonate who is in distress or develops seizures.
  • Symptoms of lethargy, vomiting, or altered behavior in a patient with a hyperammonemic disorder should be presumed to be secondary to the underlying disorder until proven otherwise.
 
Acknowledgments

The authors and editors of eMedicine gratefully acknowledge the contributions of previous author Kazi Imran Majeed, MD to the development and writing of this article.



More on Hyperammonemia

Overview: Hyperammonemia
Differential Diagnoses & Workup: Hyperammonemia
Treatment & Medication: Hyperammonemia
Follow-up: Hyperammonemia
References
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Further Reading

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Keywords

hyperammonemia, urea cycle disorders, urea cycle enzyme deficiencies, hepatic encephalopathies, Reye syndrome, toxic encephalopathies, metabolic disorders, ornithine transcarbamoylase deficiency, OTC deficiency, N -acetylglutamate synthetase deficiency, NAGS deficiency, carbamoyl phosphate synthetase I deficiency, carbamyl phosphate synthetase I deficiency, CPS I deficiency, argininosuccinic acid synthetase deficiency, AS deficiency, argininosuccinic lyase deficiency, AL deficiency, arginase deficiency, isovaleric acidemia, propionic acidemia, methylmalonic acidemia, glutaric acidemia type II, multiple carboxylase deficiency, beta-ketothiolase deficiency, congenital lactic acidosis, pyruvate dehydrogenase deficiency, pyruvate carboxylase deficiency, mitochondrial disorders, acyl CoA dehydrogenase deficiency, systemic carnitine deficiency, hyperammonemia-hyperornithinemia-homocitrullinuria, HHH

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Contributor Information and Disclosures

Author

Elena Crisan, MD, Consulting Staff, Department of Neurology, Edwards Hines Veterans Affairs Hospital
Elena Crisan, MD is a member of the following medical societies: American Academy of Neurology
Disclosure: Nothing to disclose.

Coauthor(s)

Jasvinder Chawla, MBBS, MD, MBA, Chief of Neurology, Hines Veterans Affairs Hospital; Associate Professor and Director, Neurology Residency Training Program, Loyola University Medical Center
Jasvinder Chawla, MBBS, MD, MBA is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American Clinical Neurophysiology Society, and American Medical Association
Disclosure: Nothing to disclose.

Medical Editor

J Stephen Huff, MD, Associate Professor, Emergency Medicine and Neurology, Department of Emergency Medicine, University of Virginia Health Sciences Center
J Stephen Huff, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Neurology, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Richard J Caselli, MD, Professor, Department of Neurology, Mayo Medical School, Rochester, MN; Chair, Department of Neurology, Mayo Clinic of Scottsdale
Richard J Caselli, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American Medical Association, American Neurological Association, and Sigma Xi
Disclosure: Nothing to disclose.

CME Editor

Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital
Matthew J Baker, MD is a member of the following medical societies: American Academy of Neurology
Disclosure: Nothing to disclose.

Chief Editor

Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Y Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.

 
 
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