Hyperammonemia in the Adult Critical Care Setting

  • K. Dams
  • W. Meersseman
  • A. Wilmer
Conference paper


Ammonia is produced from the breakdown of proteins, aminoacids, purines, and pyrimidines. About half of the ammonia arising from the intestine is synthesized by bacteria, the remainder coming from dietary protein and glutamine. Ammonia is a highly toxic compound, particularly to the brain. When blood concentrations of ammonia are sufficiently elevated, respiratory alkalosis, cerebral edema, altered mental status, seizures, coma and death can ensue. The liver normally converts ammonia to urea in the Krebs-Henseleit cycle (urea cycle). Urea is a non-toxic compound excretable in the urine.


Valproic Acid Hepatic Encephalopathy Ammonia Level Urea Cycle Urea Cycle Disorder 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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  1. 1.
    Jalan R, Hayes PC (1997) Hepatic encephalopathy and ascites. Lancet 350:1309–1315PubMedCrossRefGoogle Scholar
  2. 2.
    Showcross D, Jalan R (2005) Dispelling myths in the treatment of hepatic encephalopathy. Lancet 365:431–433Google Scholar
  3. 3.
    Hawkes N, Thomas G, Jurewicz A, et al (2001) Non-hepatic hyperammonemia: an important, potentially reversible cause of encephalopathy. Postgrad Med J 77:717–722PubMedCrossRefGoogle Scholar
  4. 4.
    Brusilow SW (2002) Hyperammonemic encephalopathy. Medicine 81:240–249PubMedCrossRefGoogle Scholar
  5. 5.
    Brachmann C, Braissant O, Villard AM, Boulat O, Henry H (2004) Ammonia toxicity to the brain and creatine. Mol Gen Metab 81:S52–S57CrossRefGoogle Scholar
  6. 6.
    Wraith YE (1989) Diagnosis and management of inborn errors of metabolism. Arch Dis Child 64:1410–1415PubMedCrossRefGoogle Scholar
  7. 7.
    Brusilow SW, Valle DL, Batshaw M (1979) New pathways of nitrogen excretion in inborn errors of urea synthesis. Lancet 1979 2:452–454PubMedCrossRefGoogle Scholar
  8. 8.
    Summar ML, Barr F, Dawling S, Smith W, et al (2005) Unmasked adult-onset urea cycle disorders in the critical care setting. Crit Care Clin 21:S1–S8PubMedCrossRefGoogle Scholar
  9. 9.
    Wadzinki J, Franks R, Roane D, Bayard M (2007) Valproate-associated hyperammonemic encephalopathy. J Am Board Fam Med 20:499–502CrossRefGoogle Scholar
  10. 10.
    Segura-Bruna N, Rodriguez-Campello A, Puente V, Roquer J (2006) Valproate-induced hyperammonemic encephalopathy. Acta Neurol Scan 114:1–7CrossRefGoogle Scholar
  11. 11.
    Albersen M, Joniau S, Van Poppel H, Cuyle PJ, Knockaert DC, Meersseman W (2007) Ureasplitting urinary tract infection contributing to hyperammonemic encephalopathy. Nat Clin Pract Urol 4:455–458PubMedCrossRefGoogle Scholar
  12. 12.
    De Jonghe B, Janier V, Abderrahim N, Hillion D, Lacherade JC, Outin H (2002) Urinary tract infection and coma. Lancet 360: 996PubMedCrossRefGoogle Scholar
  13. 13.
    Mas A (2006) Hepatic encephalopathy: from pathophysiology to treatment. Digestion 73(suppl 1):86–93PubMedCrossRefGoogle Scholar
  14. 14.
    Ferenci P, Lockwood A, Mullen K, Tarter R, Weissenborn K, Blei AT and the Members of the Working Party (2002) Hepatic encephalopathy — Definition, nomenclature, diagnosis, and quantification: Final report of the working party at the 11th world congresses of gastroenterology, Vienna, 1998. Hepatology 35:716–721PubMedCrossRefGoogle Scholar
  15. 15.
    Barsotti RJ (2001) Measurement of ammonia in blood. J Pediatr 138:S11–S20PubMedCrossRefGoogle Scholar
  16. 16.
    da Fonseca-Wollheim F (1990) Preanalytical increase of ammonia in blood specimens from healthy subjects. Clin Chem 36:1483–1487PubMedGoogle Scholar
  17. 17.
    Steiner RD, Cederbauw SD (2001) Laboratory evaluation of urea cycle disorders. J Pediatr 138:S21–S29PubMedCrossRefGoogle Scholar
  18. 18.
    Mas A (2006) Hepatic encephalopathy: from pathophysiology to treatment. Digestion 73(suppl 1):86–93PubMedCrossRefGoogle Scholar
  19. 19.
    Wright G, Jalan R (2007) Management of hepatic encephalopathy in patients with cirrhosis. Best Pract Res Clin Gastroenterol 21:95–110PubMedCrossRefGoogle Scholar
  20. 20.
    Riordan SM, Williams R (1997) Treatment of hepatic encephalopathy. N Engl J Med 337: 473–479PubMedCrossRefGoogle Scholar
  21. 21.
    Als-Nielsen B, Gluud LL, Gluud C (2004) Nonabsorbable disaccharides for hepatic encephalopathy. Cochrane Database Syst Rev CD 003044Google Scholar
  22. 22.
    Kircheis G, Wettstein M, Dahl S, Hüssinger D (2002) Clinical efficacy of L-Ornithine-L-Aspartate in the management of hepatic encephalopathy. Metab Brain Dis 17:453–462PubMedCrossRefGoogle Scholar
  23. 23.
    Marchesini G, Fabbri A, Bianchi G, Brizi M, Zoli M (1996) Zinc supplementation and amino acid-nitrogen metabolism in patients with advanced cirrhosis. Hepatology 23:1084–1092PubMedCrossRefGoogle Scholar
  24. 24.
    Laleman W, Wilmer A, Evenepoel P, Verslype C, Fevery J, Nevens F (2006) Review article: non-biological liver support in liver failure. Aliment Pharmacol Ther 23:351–363Google Scholar
  25. 25.
    Enns GM, Berry SA, Berry GT, Rhead WJ, Brusilow SW, Hamosh A (2007) Survival after treatment with phenylacetate and benzoate for urea-cycle disorders. N Engl J Med 356: 2282–2292PubMedCrossRefGoogle Scholar
  26. 26.
    Lheureux PER, Penaloz A, Zahir S, Gris M (2005) Science review: carnitine in the treatment of valproic acid-induced toxicity —what is the evidence? Crit Care 9:431–440PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science + Business Media Inc. 2008

Authors and Affiliations

  • K. Dams
    • 1
  • W. Meersseman
    • 1
  • A. Wilmer
    • 1
  1. 1.Medical Intensive Care UnitUniversity HospitalLeuvenBelgium

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