Hyperammonemia
| Hyperammonemia | |
|---|---|
| Other names | Hyperammonaemia |
 | |
| Ammonia | |
| Specialty | Endocrinology  |
Hyperammonemia is a
metabolic disturbance characterised by an excess of ammonia in the blood. It is a dangerous condition that may lead to brain injury and death
. It may be primary or secondary.
Ammonia is a substance that contains
enzymes acting in sequence. It is greatly exacerbated by common zinc deficiency, which raises ammonia levels further.[1]
Signs and symptoms
Complication
Hyperammonemia is one of the metabolic derangements that contribute to hepatic encephalopathy, which can cause swelling of astrocytes and stimulation of NMDA receptors in the brain.
Diagnosis
Types
Primary vs. secondary
- Primary hyperammonemia is caused by several X-linked fashion.[2]
- Secondary hyperammonemia is caused by inborn errors of intermediary hepatic cirrhosis with liver failure.[2]
Acquired vs. congenital
- Acquired hyperammonemia is usually caused by diseases that result in either acute liver failure, such as overwhelming hepatitis B or exposure to hepatotoxins, or cirrhosis of the liver with chronic liver failure. Chronic hepatitis B, chronic hepatitis C, and excessive alcohol consumption are common causes of cirrhosis. The physiologic consequences of cirrhosis include shunting of blood from the liver to the inferior vena cava, resulting in decreased filtration of blood and removal of nitrogen-containing toxins by the liver, and then hyperammonemia. This type of hyperammonemia can be treated with antibiotics to kill the bacteria that initially produce the ammonia, though this does not work as well as the removal of protein from the colon prior to its digestion to ammonia, achieved by lactulose administration for frequent (3-4 per day) bowel movements.
- Medication-induced hyperammonemia can occur with valproic acid overdose, and is due to a deficiency in carnitine. Its treatment is carnitine replacement.
- Urinary tract infection caused by urease-producing organisms (Proteus, Pseudomonas aeruginosa, Klebsiella, Morganella morganii, and Corynebacterium) can also lead to hyperammonemia.[3] But there are case reports where hyperammonemia was caused by urease negative organisms.[4] Urease producers form ammonia and carbon dioxide from urea. Ammonia then enters the systemic circulation (most venous supply of the bladder bypasses portal circulation) and enters the blood–brain barrier causing encephalopathy.[3]
- Severe dehydration and small intestinal bacterial overgrowth can also lead to acquired hyperammonemia.[citation needed]
- Glycine toxicity causes hyperammonemia, which manifests as CNS symptoms and nausea. Transient blindness can also occur.[5]
- Congenital hyperammonemia is usually due to genetic defects in one of the enzymes of the urea cycle, such as ornithine transcarbamylase deficiency, which leads to lower production of urea from ammonia.
Specific types
The following list includes such examples:
- Online Mendelian Inheritance in Man (OMIM): 311250 - hyperammonemia due to ornithine transcarbamylase deficiency
- Online Mendelian Inheritance in Man (OMIM): 606762 - hyperinsulinism-hyperammonemia syndrome (glutamate dehydrogenase 1)
- hyperornithinemia-hyperammonemia-homocitrullinuria syndrome
- Online Mendelian Inheritance in Man (OMIM): 237310 - hyperammonemia due to N-Acetylglutamate synthase deficiency
- Online Mendelian Inheritance in Man (OMIM): 237300 - hyperammonemia due to carbamoyl phosphate synthetase I deficiency (carbamoyl phosphate synthetase I)
- hyperlysinuriawith hyperammonemia (genetics unknown)
- Methylmalonic acidemia
- Isovaleric acidemia
- Propionic acidemia
- Carnitine palmitoyltransferase II deficiency
- Transient hyperammonemia of the newborn, specifically in the preterm
Treatment
Treatment centers on limiting intake of ammonia and increasing its excretion.
Phenylbutyrate, which is the product of phenylacetate, conjugates with glutamine to form phenylacetylglutamine, which is excreted by the kidneys. Similarly, sodium benzoate reduces ammonia content in the blood by conjugating with glycine to form hippuric acid, which is rapidly excreted by the kidneys.[7] A preparation containing sodium phenylacetate and sodium benzoate is available under the trade name Ammonul
.
Acidification of the intestinal lumen using lactulose can decrease ammonia levels by protonating ammonia and trapping it in the stool. This is a treatment for hepatic encephalopathy.[8]
Treatment of severe hyperammonemia (serum ammonia levels greater than 1000
μmol/L) should begin with hemodialysis if it is otherwise medically appropriate and tolerated.[5]
Urea cycle defect like Ornithine transcarbamoylase (OTC) deficiency. Multidisciplinary team (MDT) collaboration is required to optimize this advanced treatment. Simulation training might be the best training and teaching strategy to ensure MDT successful therapy.[9]
See also
- Arginase deficiency
- Citrullinemia
- N-acetylglutamate synthetase deficiency
- Ornithine translocase deficiency
- Carbamoyl phosphate synthetase I deficiency
- Orotic aciduria
References
- S2CID 1141979.
- ^ PMID 30522498.
- ^ a b Nepal SP, Unoki T, Inoue T, Nakasato T, Naoe M, Ogawa Y, Omizu M, Kato R, Sugishita H, Oshinomi K, Morita J, Maeda Y, Shichijo T. A case of hyperammonemia in a patient with urinary tract infection and urinary retention. Urol Sci [serial online] 2020 [cited 2021 Apr 3];31:82-4. Available from: https://www.e-urol-sci.com/text.asp?2020/31/2/82/283250
- ^ Kenzaka T, Kato K, Kitao A, et al. Hyperammonemia in Urinary Tract Infections. PLoS One. 2015;10(8):e0136220. Published 2015 Aug 20. doi:10.1371/journal.pone.0136220
- ^ ISBN 9781416042525
- ^ Chawla, Jasvinder (12 September 2022). "Hyperammonemia". Medscape. Retrieved 18 March 2024.
- ^ "Ammonul (Sodium Phenylacetate and Sodium Benzoate Injection) clinical pharmacology - prescription drugs and medications at RxList". Archived from the original on 2008-06-16. Retrieved 2008-06-26.
- PMID 37820287.
- ^ Elbaba, Mostafa. "IPE Simulation Enhances the Quality of Care in Neonatal Hyperammonemia". Cureus Journal of Medical Science.