Unusual causes of hyperammonemia in the ED

Hyperammonaemia: review of the pathophysiology, aetiology and investigation

Acute hyperammonaemia is a medical emergency as it can progress to cerebral oedema, seizures, coma and death. Hepatic encephalopathy secondary to cirrhotic disease or portosystemic shunting are relatively well-known causes, but non-cirrhotic aetiologies of acute hyperammonaemia are less well-known, especially in the emergency department. However, an elevated ammonia is not required to make the diagnosis of hepatic encephalopathy. Although measurement of plasma ammonia is recommended for patients with acute, unexplained, altered mental status, as early identification allows early effective management which may prevent irreversible brain damage, there is currently reduced awareness among physicians of the non-cirrhotic aetiologies of acute hyperammonaemia. Furthermore, measurement of ammonia in patients with cirrhosis has been shown to have low sensitivity and specificity, and not to have altered management in the majority of cases; thus, measurement of ammonia is currently not recommended in guidelines for management of hepatic encephalopathy. We sought to describe the pathophysiology of hyperammonaemia and review the non-cirrhotic causes. This was achieved by review of MEDLINE, PubMed and Web of Science databases to include published English literature within the last 20 years. We also present a framework for investigating the acute non-cirrhotic causes of hyperammonaemia to assist both chemical pathologists and clinicians managing these often challenging cases.

Hyperammonemia of unknown cause in a young postpartum woman: a case report

Background

Hyperammonemia is a medical condition described as increased or elevated serum ammonia levels. High serum levels of ammonia can cause neurotoxicity. Sudden onset severe hyperammonemia may cause severe encephalopathy with brain damage. It can result in cerebral edema, emesis, seizures, hypotonia, and death. We report a young postpartum woman who had a sudden rise in serum ammonia levels after vaginal delivery.

Case presentation

A 24-year-old, married, postpartum Pakistani woman was admitted to the intensive care unit through the emergency department, with complaints of fever, severe abdominal pain with distension, and altered levels of consciousness. The patient had a medical history of spontaneous vaginal delivery 2 weeks before this hospital admission, after which she gradually developed the above symptoms. However, the patient’s past medical history was unremarkable with no hepatic disease, but her investigations revealed a progressive rise in serum ammonia levels. In the intensive care unit, she developed generalized tonic–clonic seizures. This was followed by a coma, tonsillar herniation, and death.

Conclusion

Postpartum hyperammonemia is a rare entity. It is a critical illness and must be evaluated for underlying metabolic disorders. Early diagnosis and treatment may result in better outcomes and reduced mortality among postpartum women with hyperammonemia.

Chemotherapy in a Breast Cancer Patient Heterozygous Carrier of Ornithine Transcarbamylase Deficiency

Urea cycle disorders (UCDs) are an unusual genetic condition that may lead to hyperammonemia in catabolic situations such as surgery, infections or chemotherapy administration. Without specific treatment, it causes life-threatening encephalopathy. We present the case of a young woman, heterozygous carrier of ornithine transcarbamylase deficiency (OTCD) with breast cancer, who was treated with surgery, chemotherapy, radiotherapy and hormone therapy while following a protocol to minimize the risk of metabolic decompensation due to her condition.

Transient splenial lesion due to non-cirrhotic hyperammonaemia in dengue fever

Transient splenial lesion(TSL) is seen in a variety of conditions and is detectable only on MRI of the brain. Dengue fever (DF) is a common viral infection encountered in the tropics. The affected patients may face neurological complications like encephalopathy and intracranial haemorrhage, or even ischaemic stroke. Non-cirrhotic hyperammonaemia is a rare scenario; and its occurrence in DF is unknown. The patient being described had DF and developed dysarthria. His MRI brain showed splenial hyperintensity. Further evaluation revealed non-cirrhotic hyperammonaemia. To the best of our knowledge, TSL due to non-cirrhotic hyperammonaemia in DF is an unreported scenario.

Hyperammonemic encephalopathy in a patient receiving fluorouracil/oxaliplatin chemotherapy

Hyperammonemia is a rare adverse effect of 5‐fluorouracil (5‐FU) therapy, but can be very serious, even fatal. Physicians must be aware that hyperammonemic encephalopathy sometimes develops as an adverse event after 5‐FU therapy.

Recurrent Hyperammonaemic Encephalopathy in a Patient with Urinary Tract Infection and Urinary Retention

Acute hyperammonaemia is a medical emergency. Most cases are resulted from severely impaired liver function but some cases of non-hepatic causes do occur. In patients with unexplained altered conscious state, immediate measurement of plasma ammonia level is a simple but important step in early diagnosis of hyperammonaemia and prompt reduction of ammonia level to minimise permanent brain damage. We reported a case of recurrent hyperammonaemia and cerebral dysfunction due to urinary tract infection with urinary retention in a patient without underlying liver disease.

Valproic Acid—Induced Hyperammonemia in a Patient With Schizoaffective Disorder

Valproic acid is used in psychiatry as a mood stabilizer and can be very effective in reducing symptoms of agitation. Valproic acid may cause hyperammonemia through carnitine deficiency created by its inhibition of mitochondrial enzymes in the urea cycle. Clinical presentation of hyperammonemia usually involves lethargy and somnolence, which may also be noted with therapeutic serum concentration during valproic acid therapy. The diagnosis of hyperammonemia is often overlooked due to a clinical presentation that may include normal liver enzyme tests and serum valproate levels that are within the therapeutic range. Treatment modalities may include discontinuation of valproic acid therapy, lactulose, naloxone, and hemodialysis. Carnitine supplementation, for both prevention and acute treatment of hyperammonemia, has been anecdotally reported and may be considered. This article illustrates a case of an adult male with schizoaffective disorder who was treated with valproic acid and subsequently developed hyperammonemia, despite therapeutic valproic acid serum levels and normal liver enzyme tests. Possible causes of hyperammonemia and current treatment options will be described, as well as suggestions for monitoring for this adverse event in the clinical setting.

Carnitine and/or Acetylcarnitine Deficiency as a Cause of Higher Levels of Ammonia

Blood carnitine and/or acetylcarnitine deficiencies are postulated in the literature as possible causes of higher ammonia levels. The aim of this study was to investigate if the use of valproic acid, the age of the patients, or certain central nervous system pathologies can cause carnitine and/or acetylcarnitine deficiency leading to increased ammonia levels. Three groups of patients were studied: (A) epileptic under phenytoin monotherapy (n = 31); (B) with bipolar disorder under valproic acid treatment (n = 28); (C) elderly (n = 41). Plasma valproic acid and blood carnitine and acyl carnitine profiles were determined using a validated HPLC and LC-MS/MS method, respectively. Blood ammonia concentration was determined using an enzymatic automated assay. Higher ammonia levels were encountered in patients under valproic acid treatment and in the elderly. This may be due to the lower carnitine and/or acetylcarnitine found in these patients. Patients with controlled seizures had normal carnitine and acetylcarnitine levels. Further studies are necessary in order to conclude if the uncontrolled bipolar disorder could be the cause of higher carnitine and/or acetylcarnitine levels.

Noncirrhotic hyperammonemia causing relapsing altered mental status

Hyperammonemia is a recognized cause of encephalopathy. However, it is commonly seen in patients with liver disease. The clinical entity of noncirrhotic hyperammonemia is now being increasingly recognized. We report a man who presented to our hospital with relapsing altered mental status later diagnosed as noncirrhotic hyperammonemia.

Severe hyperammonaemia in adults not explained by liver disease

Ammonia is produced continuously in the body. It crosses the blood-brain barrier readily and at increased concentration it is toxic to the brain. A highly integrated system protects against this: ammonia produced during metabolism is detoxified temporarily by incorporation into the non-toxic amino acid glutamine. This is transported safely in the circulation to the small intestine, where ammonia is released, carried directly to the liver in the portal blood, converted to non-toxic urea and finally excreted in urine. As a result, plasma concentrations of ammonia in the systemic circulation are normally very low (<40 μmol/L). Hyperammonaemia develops if the urea cycle cannot control the ammonia load. This occurs when the load is excessive, portal blood from the intestines bypasses the liver and/or the urea cycle functions poorly. By far, the commonest cause is liver damage. This review focuses on other causes in adults. Because they are much less common, the diagnosis may be missed or delayed, with disastrous consequences. There is effective treatment for most of them, but it must be instituted promptly to avoid fatality or long-term neurological damage. Of particular concern are unsuspected inherited defects of the urea cycle and fatty acid oxidation presenting with catastrophic illness in previously normal individuals. Early identification of the problem is the challenge.

Transient hyperammonemia in seizures: a prospective study

PURPOSE

To investigate the incidence and duration of transient hyperammonemia in seizures and to verify the significant confounders related to transient hyperammonemia in seizures.

METHODS

One hundred twenty-one noncirrhotic adult patients with seizures admitted to the emergency department were enrolled in the study. Laboratory examination was performed, including plasma ammonia level assessment. In addition, the basic parameters, underlying systemic diseases, and seizure-related conditions were assessed. The patients were classified into a group with hyperammonemia on arrival and a group without, in order to compare seizure-related adverse events that occurred during a 9-month period.

KEY FINDINGS

The incidence of hyperammonemia in patients with seizures was 67.77%. Plasma ammonia levels in patients with generalized tonic-clonic (GTC) seizures were significantly higher than those in patients in the non-GTC seizure group (median 174.5 vs. 47 μg/dl; proportion 76.5% vs. 21.1%; p < 0.001). Median plasma ammonia levels decreased spontaneously from 250 to 54 μg/dl (p < 0.00001) in an average interval of 466.79 min. GTC seizures (p < 0.0001), male gender (p < 0.0001), bicarbonate (p < 0.0001), diabetes (p = 0.0139), and alcohol-related seizures (p = 0.0002) were significant factors associated with hyperammonemia on arrival. No significant differences related to admission rates or mortalities were found between the two groups.

SIGNIFICANCE

The presence of transient hyperammonemia in patients with seizures is significantly related to GTC seizures, male gender, bicarbonate, diabetes, and alcohol-related seizures. The appropriate period to study ammonia levels following a seizure event is within 8 h. Because these phenomena are self-limited, ammonia-lowering management are not necessary. Hyperammonemia on arrival is not necessarily related to adverse outcomes.

Adult nonhepatic hyperammonemia: a case report and differential diagnosis

This article presents a case report of nonhepatic hyperammonemia, i.e., elevated serum ammonia secondary to a nonhepatic etiology. It then discusses the importance of broadening one's differential diagnosis to include such nonhepatic causes of elevated ammonia levels, and provides a short review of rarer causes of hyperammonemia in the adult population. Treating the underlying condition is the best way to prevent recurrence of hyperammonemia. However, symptomatic treatment should not be delayed while investigating the underlying source.

Reversing Hyperammonemia in Neuroendocrine Tumors

Ammonia is a neurotoxin that is normally cleared by the intact liver and if not, hyperammonemia results in hepatic encephalopathy. Hyperammonemia may be owing to primary or secondary causes. Early diagnosis is important to prevent permanent brain damage. Advanced malignancy involving the liver is associated with hyperammonemia as a result of abnormality of the portal venous system or massive hepatic tumor burdon. Neuroendocrine tumors are an example of a malignant process that frequently involves the liver but despite this, may still have a relatively good prognosis, and are often characterized by chronic manageable symptoms and slow progression. Hyperammonemia in neuroendocrine tumor would represent a potentially reversible but ongoing process associated with an indolent malignancy. We present 2 cases that are examples of this diagnosis and discuss the diagnostic and management issues that may arise.

Central and peripheral nervous system toxicity of common chemotherapeutic agents

Central and peripheral nervous system toxicity are frequent complications of most chemotherapy regimens, often leading to reduction of dosages or cessation of the responsible drugs. However, sometimes the afflicted toxicity may not be reversible, especially if it is not recognized early, further compromising the quality of life of the cancer patients. The most common chemotherapeutic agents that might cause CNS toxicity manifested as encephalopathy of various severities include methotrexate, vincristine, ifosfamide, cyclosporine, fludarabine, cytarabine, 5-fluorouracil, cisplatin and the interferons (alpha > beta). Involvement of the peripheral nervous system manifested as distal peripheral neuropathy results after therapy with cisplatin, vincristine, taxanes, suramin and thalidomide. Although several compounds have been proposed as neuroprotective agents, few have been shown to be active against the chemotherapy induced neurotoxicity.

Hyperammonemic encephalopathy in a patient with primary hepatic neuroendocrine carcinoma

A 53-year-old male patient was admitted to our hospital with abdominal pain in the right upper quadrant. There was no change in laboratory investigations other than a slight increase in serum levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), and gamma glutamyl transferase (GGT). Computed tomography (CT) of the abdomen showed multiple hepatic nodular lesions in the liver. Tru-cut biopsy of the lesions was reported as well-differentiated neuroendocrine carcinoma. The patient received sandostatin treatment. After a few days, the patient was hospitalized in the intensive care unit with disturbance of consciousness and clinical features suggestive of encephalopathy. Serum ammonia level was found highly elevated. After the treatment with L-ornithine-L-aspartate, a remarkable improvement in the level of patient's sensorium occurred as well as a reduction in serum ammonia level within a few days. Transarterial chemoembolization (TACE) was performed one week later. The patient's condition began to worsen along with increase in serum ammonia level and he died because of hyperammonemic encephalopathy. There are case reports of hyperammonemia with some malignancies such as multiple myeloma, plasma cell leukemia, and leiomyosarcoma, or in some patients who have received chemotherapy. This case may suggest an association between hyperammonemia and neuroendocrine tumors.

Valproate-induced hyperammonemic encephalopathy

Valproate-induced hyperammonemic encephalopathy is an unusual but serious complication that can occur in people with normal liver-associated enzyme levels, and despite normal therapeutic doses and serum levels of valproate. Here, we describe an adolescent girl suffering from absence seizures, who complained of progressive dizziness and general malaise several days after restarting valproate. She developed vomiting and decreased consciousness after 3 weeks of valproate use. She had a serum ammonia level five times higher than the upper normal limit, normal liver-associated enzymes, and a supra-therapeutic valproate level. Electroencephalography (EEG) showed continuous generalized slowing. Tandem mass spectrometry analysis revealed carnitine deficiency. Her consciousness improved after emergent hemodialysis. Her ammonia level and EEG also became normal. Possible mechanisms, risk factors and treatments of valproate-induced hyperammonemic encephalopathy are described. Physicians should consider this possibility when consciousness disturbance occurs in patients treated with valproate.

Hemodialysis for hyperammonemia associated with ornithine transcarbamylase deficiency

Acute hyperammonemia is a medical emergency requiring rapid recognition and treatment to prevent devastating neurologic sequelae. Its varying etiologies include primary hepatic failure, drug toxicity, infection, and inherited disorders of metabolism. Ornithine transcarbamylase (OTC) deficiency is the most common inherited urea cycle disorder and can result in hyperammonemic encephalopathy and coma, often presenting in the newborn or early childhood. Partial deficiencies of the enzyme can present later in adulthood with protean neuropsychiatric signs and symptoms. Early recognition and management of metabolic encephalopathy is crucial to avoid neurologic damage, and may require hemodialysis for rapid removal of ammonia, with adjunctive medications and dietary modifications to decrease endogenous nitrogen production and activate alternate pathways of nitrogen excretion. We present the case of an adult patient with partial OTC deficiency who presented with encephalopathy, coma, and seizures, accompanied by hyperammonemia and treated acutely with hemodialysis.

An unusual case of hyperammonemia in a 83-year-old woman

Hyperammonemia, with confusion and lethargy, developed in a 83-year-old woman during a urinary tract infection by Morganella morganii, a urea-splitting Gram-negative bacillus. In this patient, it is thought to have resulted from the production of excessive amounts of ammonia due to bacterial urease and its subsequent reabsorption into systemic circulation. The patient was treated with specific antibiotic therapy, with resolution of the urinary tract infection, progressive reduction in ammonia blood levels, and a parallel improvement in her consciousness and cognitive status.