Hyperammonemia encephalopathy: an important cause of neurological deterioration following chemotherapy

Efficacy and adverse events of L-Asparaginase administration as a first-line treatment for feline large-cell gastrointestinal lymphoma

L-Asparaginase (L-Asp) is often used to induce remission in feline large-cell gastrointestinal lymphoma (LCGIL). However, no study has evaluated the efficacy and adverse events following the initial use of this drug as a first-line treatment in feline LCGIL. We retrospectively reviewed medical records of cats with LCGIL treated with L-Asp to induce remission. This study included 43 cats. The response rate (RR) after the first administration of L-Asp was 37.2% (Complete remission: 7.0%, partial remission: 30.2%). RR was significantly higher in cases with primary gastric lesions (64.3%) than in those with primary intestinal lesions (24.1%) (P=0.018), and it was also higher in cases without anemia (57.1%) than those with anemia (15.0%) (P=0.009). The most common adverse event was hyperammonemia, which occurred in 10 of 12 cases where we could compare plasma ammonia concentrations before and after the first dose of L-Asp. Plasma phosphate concentrations were also significantly increased (P<0.001) within 24 hr after the first dose. Decreased appetite, vomiting, and diarrhea were also observed in five, three, and seven cases, respectively, and Grade 3 or higher gastrointestinal signs were observed as adverse events in three cases. The median overall survival of all cats was 150 days (range, 5-1,065 days), and the median progression-free survival was 104 days (range, 2-978 days). In conclusion, L-Asp was effective to induce remission, and severe adverse events were uncommon in feline LCGIL.

Hyperammonemic encephalopathy after tyrosine kinase inhibitors: A literature review and a case example

OBJECTIVE

To review the evidence of uncommon but fatal adverse event of hyperammonemic encephalopathy by tyrosine kinase inhibitors (TKI) and the possible mechanisms underlying this condition and to describe the case of a patient that developed drug-induced hyperammonemic encephalopathy related to TKI.

DATA SOURCES

Literature search of different databases was performed for studies published from 1 January 1992 to 7 May 2023. The search terms utilized were hyperammonemic encephalopathy, TKI, apatinib, pazopanib, sunitinib, imatinib, sorafenib, regorafenib, trametinib, urea cycle regulation, sorafenib, carbamoyl-phosphate synthetase 1, ornithine transcarbamylase, argininosuccinate synthetase, argininosuccinate lyase, arginase 1, Mitogen activated protein kinases (MAPK) pathway and mTOR pathway, were used individually search or combined.

DATA SUMMARY

Thirty-seven articles were included. The articles primarily focused in hyperammonemic encephalopathy case reports, management of hyperammonemic encephalopathy, urea cycle regulation, autophagy, mTOR and MAPK pathways, and TKI.

CONCLUSION

Eighteen cases of hyperammonemic encephalopathy were reported in the literature from various multitargeted TKI. The mechanism of this event is not well-understood but some authors have hypothesized vascular causes since some of TKI are antiangiogenic, however our literature review shows a possible relationship between the urea cycle and the molecular inhibition exerted by TKI. More preclinical evidence is required to unveil the biochemical mechanisms responsible involved in this process and clinical studies are necessary to shed light on the prevalence, risk factors, management and prevention of this adverse event. It is important to monitor neurological symptoms and to measure ammonia levels when manifestations are detected.

Hepatic veno-occlusive disease complicated with extreme hyperammonaemia (920 µmol/L) treated with defibrotide, lactulose, rifampin and haemodialysis

Hepatic veno-occlusive disease (VOD)/sinusoidal obstructive syndrome (SOS) is a severe complication that can occur following haematopoietic stem cell transplant (HSCT) with high-intensity conditioning chemotherapy regimens. Severe VOD/SOS, often characterised by multiorgan failure, is associated with a high mortality rate. This case report details the complex clinical course of a male patient in his mid-20s, recently diagnosed with B cell acute lymphoblastic leukaemia, who underwent allogeneic HSCT. Based on the 2023 European Society for Blood and Marrow Transplantation (EBMT) criteria, the patient developed very severe VOD/SOS, prompting immediate treatment with defibrotide. Unexpectedly, he developed profound hyperammonaemia exceeding 900 µmol/L, leading to encephalopathy and cerebral oedema. Despite aggressive interventions including defibrotide, lactulose, rifampin and haemodialysis, the patient passed away due to cerebral oedema and pulseless electrical activity arrest. We theorise the hyperammonaemia is disproportionate to his hepatic dysfunction and is possibly secondary to an acquired defect of the urea synthesis consistent with idiopathic hyperammonaemia, a rare complication in patients receiving intense conditioning chemotherapy.

Sunitinib-induced hyperammonemic encephalopathy in metastatic gastrointestinal stromal tumors: A case report

BACKGROUND

Sunitinib, a multi-targeted tyrosine kinase inhibitor (TKI), has been approved for the salvage treatment of gastrointestinal stromal tumors (GIST). Hyperammonemic encephalopathy is a rare but severe complication of sunitinib use. Here, we present the case of a 66-year-old male with metastatic GIST without underlying liver cirrhosis who developed sunitinib-induced hyperammonemic encephalopathy.

CASE SUMMARY

A 66-year-old male with metastatic GIST was admitted because of reduced consciousness. Imatinib was administered as the first-line systemic therapy. He experienced repeated episodes of peritonitis due to tumor perforation, and surgery was performed. Progressive disease was confirmed based on increased liver metastasis, and sunitinib was initiated as a salvage treatment. However, 23 d after the third course of sunitinib, he presented to the emergency room with an episode of altered consciousness and behavioral changes. Based on the patient clinical history and examination findings, sunitinib-induced encephalopathy was suspected. Sunitinib was discontinued, and the patient was treated for hyperammonemia. The patient had a normal level of consciousness four days later, and the serum ammonia level gradually decreased. No further neurological symptoms were reported in subsequent follow-ups.

CONCLUSION

TKI-induced hyperammonemic encephalopathy is potentially life-threatening. Patients receiving TKIs experiencing adverse reactions should undergo systemic evaluation and prompt treatment.

Nonhepatic hyperammonemic encephalopathy following bariatric surgery: A systematic review

BACKGROUND

Nonhepatic Hyperammonemic encephalopathy (NHAE) following Bariatric Surgery (BS), mainly Roux-en-Y Gastric Bypass (RYGB) and Biliopancreatic Diversion (BPD) is a potentially devastating condition if not diagnosed and managed promptly.

METHODS

A literature review was performed using PRISMA guidelines. Eighteen studies and 3 conference abstracts with a total of 33 patients were included in this review.

RESULTS

Majority (28 patients, 84.8 %) had RYGB. Seven patients (21.2 %) had associated metabolic disorders. 60 % of patients presented with neurological symptoms or signs such as confusion, cognitive and/or psychomotor changes, and decreased reflexes. Two patients presented with status epilepticus. In 30 of the 33 patients an elevated serum ammonia levels was reported (90.9 %). The overall mortality was 39.3 %.

CONCLUSION

NHAE is a rare condition following bariatric surgery (in particular bypass procedures), carrying a high mortality rate. The signs and symptoms are predominantly neurological and may be mistaken for Wernicke's encephalopathy or other more common neurological conditions. Serum ammonia levels should be checked in those who present with these symptoms and signs. Prompt treatment might be life saving in patients with NHAE.

A Case of Non-cirrhotic Hyperammonemic Encephalopathy in a Patient With Metastatic Gastrointestinal Stromal Tumor

Acute toxic encephalopathy (ATE) is a widely recognized medical emergency with an expansive differential. One particular known etiology for ATE is elevated ammonia, a powerful neurotoxin that often presents with clinical findings of confusion, disorientation, tremors, and in severe cases, coma and death. Hyperammonemia is most commonly associated with liver disease and presents as hepatic encephalopathy in the setting of decompensated cirrhosis; however, in rare cases, a patient may suffer from non-cirrhotic hyperammonemic encephalopathy. We describe the case of a 61-year-old male with metastatic gastrointestinal stromal tumor who was diagnosed with non-cirrhotic hyperammonemic encephalopathy, and briefly explore the literature describing its mechanisms.

Idiopathic hyperammonemic encephalopathy secondary to gemcitabine-cisplatin treatment

Idiopathic hyperammonemic encephalopathy is a rare complication of chemotherapy, which has previously mainly been associated with L-asparaginase, cytarabine and 5-FU. We present a case following treatment with gemcitabine-cisplatin in a patient with cholangiocarcinoma. The etiology of chemotherapy-induced idiopathic hyperammonemic encephalopathy remains unclear and existing theories differ per chemotherapeutic agent. Physicians treating patients with gemcitabine-cisplatin should be aware of the possibility of this complication, especially because it is treatable when recognized early.

Role of inflammation and oxidative stress in chemotherapy-induced neurotoxicity

Chemotherapeutic agents may adversely affect the nervous system, including the neural precursor cells as well as the white matter. Although the mechanisms are not completely understood, several hypotheses connecting inflammation and oxidative stress with neurotoxicity are now emerging. The proposed mechanisms differ depending on the class of drug. For example, toxicity due to cisplatin occurs due to activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), which alters hippocampal long-term potentiation. Free radical injury is also involved in the cisplatin-mediated neurotoxicity as dysregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) has been seen which protects against the free radical injury by regulating glutathione S-transferases and hemeoxygenase-1 (HO-1). Thus, correcting the imbalance between NF-κB and Nrf2/HO-1 pathways may alleviate cisplatin-induced neurotoxicity. With newer agents like bortezomib, peripheral neuropathy occurs due to up-regulation of TNF-α and IL-6 in the sensory neurons. Superoxide dismutase dysregulation is also involved in bortezomib-induced neuropathy. This article reviews the available literature on inflammation and oxidative stress in neurotoxicity caused by various classes of chemotherapeutic agents. It covers the conventional medicines like platinum compounds, vinca alkaloids, and methotrexate, as well as the newer therapeutic agents like immunomodulators and immune checkpoint inhibitors. A better understanding of the pathophysiology will lead to further advancement in strategies for management of chemotherapy-induced neurotoxicity.

Case Report: Hyperammonemic Encephalopathy Linked to Ureaplasma spp. and/or Mycoplasma hominis Systemic Infection in Patients Treated for Leukemia, an Emergency Not to Be Missed

Background

Hyperammonemic encephalopathy caused by Ureaplasma spp. and Mycoplasma hominis infection has been reported in immunocompromised patients undergoing lung transplant, but data are scarce in patients with hematological malignancies.

Case Presentation

We describe the cases of 3 female patients aged 11–16 years old, developing initially mild neurologic symptoms, rapidly evolving to coma and associated with very high ammonia levels, while undergoing intensive treatment for acute leukemia (chemotherapy: 2 and hematopoietic stem cell transplant: 1). Brain imaging displayed cerebral edema and/or microbleeding. Electroencephalograms showed diffuse slowing patterns. One patient had moderate renal failure. Extensive liver and metabolic functions were all normal. Ureaplasma spp. and M. hominis were detected by PCR and specific culture in two patients, resulting in prompt initiation of combined antibiotics therapy by fluoroquinolones and macrolides. For these 2 patients, the improvement of the neurological status and ammonia levels were observed within 96 h, without any long-term sequelae. M. hominis was detected post-mortem in vagina, using 16S rRNA PCR for the third patient who died of cerebral edema.

Conclusion

Hyperammonemic encephalopathy linked to Ureaplasma spp. and M. hominis is a rare complication encountered in immunocompromised patients treated for acute leukemia, which can lead to death if unrecognized. Combining our experience with the few published cases (n=4), we observed a strong trend among female patients and very high levels of ammonia, consistently uncontrolled by classical measures (ammonia-scavenging agents and/or continuous kidney replacement therapy). The reversibility of the encephalopathy without sequelae is possible with prompt diagnosis and adequate combined specific antibiotherapy. Any neurological symptoms in an immunocompromised host should lead to the measurement of ammonia levels. If increased, and in the absence of an obvious cause, it should prompt to perform a search for Ureaplasma spp. and M. hominis by PCR as well as an immediate empirical initiation of combined specific antibiotherapy.

Hyperammonaemic Encephalopathy Caused by Adult-Onset Ornithine Transcarbamylase Deficiency

Hyperammonaemic encephalopathy in adults is a rare condition in the absence of liver disease and is associated with a high mortality and risk of permanent neurological deficits. Seldomly, the condition is caused by an inborn error of metabolism in the urea cycle, triggered by an exogenic factor such as gastrointestinal haemorrhage, gastric bypass surgery, starvation, seizures, vigorous exercise, burn injuries, or drugs hampering the elimination of ammonia. Here, we present a fatal case of an unrecognized genetic ornithine transcarbamylase deficiency (OTCD) presenting with a subacute progressive encephalopathy. We review the current literature and discuss the differential diagnosis and treatment options. As swift diagnosis and initiation of treatment is vital, awareness of hyperammonaemic encephalopathy and its possible causes can help improve the prognosis of this condition.

Transient Hyperammonemic Encephalopathy in a Child with Relapsed Acute Lymphoblastic Leukemia and Severe Tumor Lysis Syndrome

Idiopathic hyperammonemia (IHA) is a severe condition, which has been reported in intensive chemotherapy and bone marrow transplantation. This case elucidates the diagnostic dilemma in children undergoing initiation of chemotherapy and developing severe disorders of qualitative and quantitative consciousness in the presence of hyperammonemia (HA) and lactic acidosis. The role of mitoxantrone as a causative agent for IHA in children is elusive. Children undergoing chemotherapy are often in a poor general condition, and the clinical presentation of HA is heterogeneous. This case should be a reminder for clinicians to check for HA in children with tumor lysis syndrome and acute neurological deterioration.

SOFAMONIA: Comparison of the original SOFA score with the proposed new score including serum ammonia

Introduction:

Hyperammonemia can represent organic dysfunction of the brain, kidney, or liver. Evaluation of serum ammonia concentrations as a parameter for organ dysfunction may be justified.

Objective:

To evaluate the performance of serum ammonia as an additional or substitute variable for organ systems in the Sequential Organ Failure Assessment (SOFA) score.

Methods:

A prospective cohort study including 173 patients admitted to the intensive care unit between March 2015 and February 2016. SOFAMONIA scores were defined as follows: SOFAMONIA1 (Glasgow coma scale replaced by serum ammonia), SOFAMONIA2 (serum bilirubin replaced by serum ammonia), SOFAMONIA3 (renal system score replaced by serum ammonia), and SOFAMONIA4 (addition of serum ammonia to the original SOFA as the seventh variable, changing the maximum score from 24 to 28).

Results:

The original SOFA presented an area under the curve–receiver operating characteristic of 0.697 to predict hospital mortality. There was a positive correlation between SOFA and SOFAMONIA scores. SOFAMONIA1 presented a cut-off point of 5 for area under the curve 0.684 (0.610–0.753, 95% confidence interval), SOFAMONIA2 presented a cut-off point of 9 for area under the curve 0.701 (0.626–0.768, 95% confidence interval), SOFAMONIA3 presented a cut-off point of 8 for area under the curve 0.674 (0.598–0.743, 95% confidence interval), and SOFAMONIA4 presented a cut-off point of 8 for area under the curve 0.702 (0.628–0.769, 95% confidence interval).

Conclusions:

The addition of ammonia as the seventh parameter of the SOFA score showed the best performance to predict hospital mortality. The addition of ammonia as a representative of metabolic dysfunction may be useful in the follow-up of critically ill patients.

Russian Consensus “Hyperammonemia in Adults” (Version 2021)

Justification Given the large number of reports on the peculiarities of liver lesions during the Sars-Cov-2 infection [1], a team of experts who participated in the 23rd Congress of the Scientific Society of Gastroenterologists of Russia and 15 National Congress of Therapists of November 19, 2020 decided to make additions to the Russian Consensus of “Hyperammonemia in Adults” published early 2020 [2, 3].

A retrospective study of adult patients with noncirrhotic hyperammonemia

Adult-onset noncirrhotic hyperammonemia (NCH) is poorly understood and has a high morbidity and mortality. To elucidate the etiology and management of NCH, we performed a retrospective analysis of 23 adults (median age 51) with NCH treated between 2014 and 2020 at two academic medical centers. Hyperammonemia was diagnosed in all cases during the evaluation of altered mental status, with 22% presenting with seizures. Peak ammonia levels were >200 μmol/L in 70% of cases. Defects in ammonia metabolism were assessed using urea cycle biochemical testing, germline genetic testing, and testing for urease-producing infectious agents. Ammonia metabolism defects in these cases appear attributable to four major sources: (a) infection with urease-producing organism (n = 5); (b) previously undiagnosed inborn errors of metabolism (IEMs) (n = 4); (c) clinical exposures causing acquired urea cycle dysfunction (n = 6); and (d) unexplained acquired urea cycle dysfunction (uaUCD) (n = 8), as evidenced by biochemical signatures of urea cycle dysfunction without a genetic or clinical exposure. Severe protein malnutrition appeared to be a reversible risk factor for uaUCD. Overall, 13% of our cohort died prior to resolution of hyperammonemia, 26% died after hyperammonemia resolution, 57% survived after having reversible neurological changes, and 4% survived with irreversible neurological changes. Renal replacement therapy for ammonia clearance was often utilized for patients with an ammonia level above 250 μmol/L and patients were frequently empirically treated with antibiotics targeting urea-splitting organisms. Our study demonstrates that acquired urea cycle dysfunction, IEMs and urease-producing infections are major sources of adult-onset NCH and highlights successful management strategies for adult-onset NCH.

Hyperammonemic encephalopathy during XELOX regimen. Is it capecitabine or oxaliplatin responsible?

Hyperammonemic encephalopathy represents a rare adverse effect of several chemotherapeutic agents, occurring in about 0.7% of patients treated with fluoropyrimidines, and it is independent from dihydropyrimidine dehydrogenase deficiency. Instead, its physiopathology is linked to the inhibition of Krebs cycle by fluoroacetate, leading to decreased ATP production, and to the inhibition of the urea cycle. Oxaliplatin seems to induce hyperammonemic encephalopathy in a similar way, acting on mitochondria. Here, we report the intriguing case of acute hyperammonemic encephalopathy in a 65-year-old patient with preserved liver function, who was treated with oxaliplatin and capecitabine for a metastatic, G1, atypical lung carcinoid. We reviewed the literature and found very few reports of oxaliplatin or capecitabine-induced hyperammonemic encephalopathy. Out of five cases of capecitabine-related hyperammonemic encephalopathy analyzed (four plus our case), median time to hyperammonemic encephalopathy onset was 6 days, with median serum ammonia levels of 213 μmol/L. Oxaliplatin-related hyperammonemic encephalopathy analyzed cases were three (two plus ours), with a median time to hyperammonemic encephalopathy of 11 days and median serum ammonia levels of 167 μmol/L. Identified predisposing factors for chemotherapy-induced hyperammonemia, such as dehydration, liver and renal impairment, infections, and sarcopenia were absent in our case. We hypothesize that the combination of a platinum-derivative and a fluoropyrimidine multiplies the risk of hyperammonemic encephalopathy, even in the absence of predisposing factors nor impaired liver function. We therefore suggest to always consider the risk of hyperammonemia when starting fluoropyrimidines-based chemotherapy, especially combined with platinum-derivatives, and to timely investigate neurologic symptoms monitoring ammonia serum levels.

Survival and Neurologic Recovery After Prompt Diagnosis and Aggressive Management of Severe Idiopathic Hyperammonemic Encephalopathy in a Patient with Acute Myeloid Leukemia

A case of a 19-year-old female with low-risk acute myeloid leukemia is presented who was diagnosed with idiopathic hyperammonemic encephalopathy following the development of abrupt neurologic decline, respiratory alkalosis, and elevated plasma ammonia levels of unknown etiology. Delayed symptom recognition of this exceedingly rare condition contributes to the often fatal outcomes of idiopathic hyperammonemic encephalopathy. As illustrated by this case, prompt diagnosis and utilization of a variety of ammonia-modulating treatment modalities can result in remarkable clinical recovery. This case provides guidance to clinicians in counseling families about the possibility of neurologic recovery in similar clinical scenarios.

Fatal Idiopathic Hyperammonemia after Induction Chemotherapy for Acute Myeloid Leukemia

Idiopathic hyperammonemia is a rare but potentially fatal complication occurring in patients with acute leukemia or bone marrow transplantation. The role of some specific anticancer drugs may be discussed, but the etiology of hyperammonemia is often multifactorial. We report the case of a 40-year-old woman who developed fatal idiopathic hyperammonemia two weeks after induction chemotherapy with idarubicin-aracytine for acute myeloid leukemia. Despite intensive care management and extrarenal epuration, the patient was declared brain dead two days after hyperammonemia onset.

Noncirrhotic hyperammonemia: A factor behind dementia to alter mental status

Healthcare givers were recommended to check serum ammonia level for elderly patients with acute-on-chronic alteration of mental status. Early initiation of antihyperammonemia therapy may benefit improvement of alteration of mental status. Baseline mental status becomes necessary for diagnose the acute alteration of mental status and monitor the therapeutic process.

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.

Hyperammonemia after capecitabine associated with occult impairment of the urea cycle

Background

Cancer patients receiving chemotherapy often complain of “chemobrain” or cognitive impairment, but mechanisms remain elusive.

Methods

A patient with gastric cancer developed delirium and hyperammonemia after chemotherapy with the 5‐fluorouracil pro‐drug capecitabine. Exome sequencing facilitated a search for mutations among 43 genes associated with hyperammonemia and affecting the urea cycle directly or indirectly.

Results

The patient's urea cycle was impaired by capecitabine‐induced liver steatosis, and portosystemic shunting of gut ammonia into the systemic circulation. The patient was also heterozygous for amino acid substitution mutations previously reported to create dysfunctional proteins in 2 genes, ORNT2 (ornithine transporter‐2 for the urea cycle), and ETFA (electron transport flavoprotein alpha for fatty acid oxidation). The mutations explained the patient's abnormal plasma amino acid profile and exaggerated response to allopurinol challenge. Global population variations among the 43 hyperammonemia genes were assessed for inactivating mutations, and for amino acid substitutions predicted to be deleterious by complementary algorithms, SIFT and PolyPhen‐2. One or 2 deleterious mutations occur among the 43 genes in 13.9% and 1% of individuals, respectively.

Conclusions

Capecitabine and 5‐fluorouracil inhibit pyrimidine biosynthesis, decreasing ammonia utilization. These drugs can induce hyperammonemia in susceptible individuals. The risk factors of hyperammonemia, gene mutations and liver dysfunction, are not rare. Diagnosis will trigger appropriate treatment and ameliorate brain toxicity.

Features of Adult Hyperammonemia Not Due to Liver Failure in the ICU

OBJECTIVES

To evaluate the epidemiology of hyperammonemia unrelated to liver failure in the critical care setting.

DESIGN

Retrospective case series.

SETTING

Critically ill patients admitted to ICUs at Mayo Clinic, Rochester, MN (medical ICU, two mixed medical-surgical ICUs, coronary care unit, or the cardiosurgical ICU) between July 1, 2004, and October 31, 2015.

PATIENTS

Adult critically ill patients with hyperammonemia not related to acute or chronic liver failure. We excluded patients with diagnosis of moderate or severe liver disease, hyperbilirubinemia, and patients who denied the use of their medical records.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 3,908 ICU patients with hyperammonemia, 167 (4.5%) had no evidence of acute or chronic liver failure. One-hundred one patients (60.5%) were male with median age of 65.7 years (interquartile range, 50-74.5 yr) and median serum ammonia level of 68 µg/dL (interquartile range, 58-87 µg/dL). Acute encephalopathy was present in 119 patients (71%). Predisposing conditions included malnutrition 27 (16%), gastric bypass six (3.6%), total parenteral nutrition four (2.4%); exposure to valproic acid 17 (10%); status epilepticus 11 (6.6%), high tumour burden 19 (11.3%), and renal failure 82 (49.1%). Urea cycle defects were diagnosed in seven patients (4.1%). Hospital mortality was high (30%), and median ammonia level was higher among the nonsurvivors (74 vs 67 µg/dL; p = 0.05). Deaths were more likely in hyperammonemic patients who were older (p = 0.016), had greater illness severity (higher Acute Physiology and Chronic Health Evaluation III score, p < 0.01), malignancy (p < 0.01), and solid organ transplantation (p = 0.04), whereas seizure disorder was more common in survivors (p = 0.02). After adjustment, serum ammonia level was not associated with increased mortality.

CONCLUSIONS

Hyperammonemia occurs in a substantial minority of critically ill patients without liver failure. These patients have a poor prognosis, although ammonia level per se is not independently associated with mortality. Serum ammonia should be measured when risk factors are present, such as nutritional deficiencies and protein refeeding, treatment with valproic acid, high tumour burden, and known or suspected urea cycle abnormalities.

A model of blood-ammonia homeostasis based on a quantitative analysis of nitrogen metabolism in the multiple organs involved in the production, catabolism, and excretion of ammonia in humans

Increased blood ammonia (NH₃) is an important causative factor in hepatic encephalopathy, and clinical treatment of hepatic encephalopathy is focused on lowering NH₃. Ammonia is a central element in intraorgan nitrogen (N) transport, and modeling the factors that determine blood-NH₃ concentration is complicated by the need to account for a variety of reactions carried out in multiple organs. This review presents a detailed quantitative analysis of the major factors determining blood-NH₃ homeostasis – the N metabolism of urea, NH₃, and amino acids by the liver, gastrointestinal system, muscle, kidney, and brain – with the ultimate goal of creating a model that allows for prediction of blood-NH₃ concentration. Although enormous amounts of NH₃ are produced during normal liver amino-acid metabolism, this NH₃ is completely captured by the urea cycle and does not contribute to blood NH₃. While some systemic NH₃ derives from renal and muscle metabolism, the primary site of blood-NH₃ production is the gastrointestinal tract, as evidenced by portal vein-NH₃ concentrations that are about three times that of systemic blood. Three mechanisms, in order of quantitative importance, release NH₃ in the gut: 1) hydrolysis of urea by bacterial urease, 2) bacterial protein deamination, and 3) intestinal mucosal glutamine metabolism. Although the colon is conventionally assumed to be the major site of gut-NH₃ production, evidence is reviewed that indicates that the stomach (via Helicobacter pylori metabolism) and small intestine and may be of greater importance. In healthy subjects, most of this gut NH₃ is removed by the liver before reaching the systemic circulation. Using a quantitative model, loss of this “first-pass metabolism” due to portal collateral circulation can account for the hyperammonemia observed in chronic liver disease, and there is usually no need to implicate hepatocyte malfunction. In contrast, in acute hepatic necrosis, hyperammonemia results from damaged hepatocytes. Although muscle-NH₃ uptake is normally negligible, it can become important in severe hyperammonemia. The NH₃-lowering actions of intestinal antibiotics (rifaximin) and lactulose are discussed in detail, with particular emphasis on the seeming lack of importance of the frequently emphasized acidifying action of lactulose in the colon.

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.

Unexpected side effect in mCRC: A care-compliant case report of regorafenib-induced hyperammonemic encephalopathy

RATIONALE

Regorafenib represents a treatment option in heavily pretreated patients affected by metastatic colorectal cancer (mCRC). Its safety profile is typical of small-molecule tyrosine-kinase inhibitors (TKIs) and most adverse events are manageable.

PATIENT CONCERNS

A 56 years-old Caucasian man affected by mCRC with normal hepatic reserve was treated with regorafenib as second-line treatment. After only 2 days of therapy, the patient presented to the emergency department due to impairment of both spatial and temporal orientation and motor function with bradylalia.

INTERVENTIONS

Serum ammonia level was 191 mmol/L, liver function tests and complete blood count were normal. Regorafenib was withheld and branched chain amino acids and lactulose were administered.

OUTCOMES

Serum ammonia level returned within the normal range, but when regorafenib was restarted at a lower dose level, a new episode of acute confusion arised.

MAIN LESSON

Discontinuation of regorafenib after confirmation of hyperammonemia is strongly recommended; reintroduction of the therapy at lower doses after resolution of symptoms related to hyperammonemic encephalopathy has to be discouraged.

A Rare Case of Sunitinib-Induced Hyperammonemic Encephalopathy and Hypothyroidism in Metastatic Renal Cell Carcinoma

Sunitinib has become a standard treatment agent for metastatic renal cell carcinoma (RCC) for several years. However, various adverse events have been reported. We present a rare adverse effect of hyperammonemic encephalopathy induced by sunitinib. A 66-year-old woman with metastatic RCC referred to the emergency department with confusion that developed 14 days after the initiation of 50 mg/d of sunitinib. Her serum ammonia and thyroid-stimulating hormone levels were markedly elevated (146 μg/dL and 27.27 μIU/mL, respectively). Sunitinib was discontinued, and an enema with lactulose and L-thyroxine were administered. Her mental status and neurologic symptoms were normalized 7 days after the treatment. Serum ammonia level decreased to 61 μg/dL and thyroid stimulating hormone level decreased 22.34 μIU/mL. The incidence of sunitinib-induced hyperammonemia is rarely reported. The relationship between sunitinib and the development of hyperammonemia is not well understood, and the mechanism is unclear. Sunitinib-induced hyperammonemia is very rare, and to the best of our knowledge, this is fourth case hyperammonemia and first case hyperammonemic encephalopathy with hypothyroidism as an adverse effect. Therefore, it is important for clinicians to be aware of hyperammonemia that can occur in several days after the initiation of sunitinib treatment in metastatic RCC.

Albumin/asparaginase capsules prepared by ultrasound to retain ammonia

Asparaginase reduces the levels of asparagine in blood, which is an essential amino acid for the proliferation of lymphoblastic malign cells. Asparaginase converts asparagine into aspartic acid and ammonia. The accumulation of ammonia in the bloodstream leads to hyperammonemia, described as one of the most significant side effects of asparaginase therapy. Therefore, there is a need for asparaginase formulations with the potential to reduce hyperammonemia. We incorporated 2 % of therapeutic enzyme in albumin-based capsules. The presence of asparaginase in the interface of bovine serum albumin (BSA) capsules showed the ability to hydrolyze the asparagine and retain the forming ammonia at the surface of the capsules. The incorporation of Poloxamer 407 in the capsule formulation further increased the ratio aspartic acid/ammonia from 1.92 to 2.46 (and 1.10 from the free enzyme), decreasing the levels of free ammonia. This capacity to retain ammonia can be due to electrostatic interactions and retention of ammonia at the surface of the capsules. The developed BSA/asparaginase capsules did not cause significant cytotoxic effect on mouse leukemic macrophage cell line RAW 264.7. The new BSA/asparaginase capsules could potentially be used in the treatment of acute lymphoblastic leukemia preventing hyperammonemia associated with acute lymphoblastic leukemia (ALL) treatment with asparaginase.

Efficacy of N-carbamoyl-L-glutamic acid for the treatment of inherited metabolic disorders

INTRODUCTION

N-carbamoyl-L-glutamic acid (NCG) is a synthetic analogue of N-acetyl glutamate (NAG) that works effectively as a cofactor for carbamoyl phosphate synthase 1 and enhances ureagenesis by activating the urea cycle. NCG (brand name, Carbaglu) was recently approved by the United States Food and Drug Administration (US FDA) for the management of NAGS deficiency and by the European Medicines Agency (EMA) for the treatment of NAGS deficiency as well as for the treatment of hyperammonenia in propionic, methylmalonic and isovaleric acidemias in Europe.

AREAS COVERED

The history, mechanism of action, and efficacy of this new drug are described. Moreover, clinical utility of NCG in a variety of inborn errors of metabolism with secondary NAGS deficiency is discussed.

EXPERT COMMENTARY

NCG has favorable pharmacological features including better bioavailability compared to NAG. The clinical use of NCG has proven to be so effective as to make dietary protein restriction unnecessary for patients with NAGS deficiency. It has been also demonstrated to be effective for hyperammonemia secondary to other types of inborn errors of metabolism. NCG may have additional therapeutic potential in conditions such as hepatic hyperammonemic encephalopathy secondary to chemotherapies or other liver pathology.

Drug-induced hepatotoxicity in cancer patients - implication for treatment

INTRODUCTION

All anticancer drugs can cause idiosyncratic liver injury. Therefore, hepatoprotective agents assume particular importance to preserve liver function. Hepatic injury represents 10% of cases of acute hepatitis in adults; drug-related damage is still misjudged because of relative clinical underestimation and difficult differential diagnosis. Chemotherapeutic agents can produce liver toxicity through different pathways, resulting in different categories of liver injuries, but these drugs are not homogeneously hepatotoxic. Frequently, anticancer-induced hepatotoxicity is idiosyncratic and influenced by multiple factors.

AREAS COVERED

The aim of this paper is to perform a review of the literature regarding anticancer-induced liver toxicity. We described hepatotoxicity mechanisms of principal anticancer agents and respective dose reductions. Furthermore, we reviewed studies on hepatoprotectors and their optimal use. Tiopronin, magnesium isoglycyrrhizinate and S-Adenosylmethionine (AdoMet) demonstrated, in some small studies, a potential hepatoprotective activity.

EXPERT OPINION

Actually, in the literature only small experiences are reported. Even though hepatoprotective agents seem to be useful in the oncologic setting, the lack of well-designed prospective Phase III randomized controlled trials is a major limit in the introduction of hepatoprotectors in cancer patients and these kind of studies are warranted to support their use and to give further recommendations for the clinical practice.

Fatal Nonhepatic Hyperammonemia in ICU Setting: A Rare but Serious Complication following Bariatric Surgery

Bariatric surgery is well established in reducing weight and improving the obesity-associated morbidity and mortality. Hyperammonemic encephalopathy following bariatric surgery is rare but highly fatal if not diagnosed in time and managed aggressively. Both macro- and micronutrients deficiencies play a role. A 42-year-old Hispanic female with a history of Roux-en-Y Gastric Bypass Procedure was brought to ED for progressive altered mental status. Physical exam was remarkable for drowsiness with Glasgow Coma Scale 11, ascites, and bilateral pedal edema. Labs showed elevated ammonia, low hemoglobin, low serum prealbumin, albumin, HDL, and positive toxicology. She remained obtunded despite the treatment with Narcan and flumazenil and the serum ammonia level fluctuated despite standard treatment with lactulose and rifaximin. Laboratory investigations helped to elucidate the etiology of the hyperammonemia most likely secondary to unmasking the functional deficiency of the urea cycle enzymes. Hyperammonemia in the context of normal liver function tests becomes diagnostically challenging for physicians. Severe hyperammonemia is highly fatal. Early diagnosis and aggressive treatment can alter the prognosis favorably.

First data on the biological variation and quality specifications for plasma ammonia concentrations in healthy subjects

Background:

Most of the factors causing preanalytical and analytical variation in ammonia measurement have been identified. Biological variation data for ammonia is still lacking. We therefore estimated the components of biological variation (within-subject=CV

Methods:

Blood samples from 20 healthy subjects were collected in K2EDTA tubes daily over a period of 4 consecutive days from each subject. Each plasma sample was split into two aliquots; one was immediately analyzed as the samples were collected and the other was stored –80 °C until testing at the end of the collection period and analyzed at once in one analytical run. All samples were analyzed in duplicate. Estimations were calculated according to Fraser and Harris methods.

Results:

CV

Conclusions:

The present study for the first time described the components of biological variation for ammonia in healthy individuals. These data regarding biological variation of ammonia could be useful for a better evaluation of ammonia test results in clinical interpretation and for determining quality specifications based on biological variation.

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.

Idiopathic Hyperammonemia That Developed During Initial Treatment With Steroid in a Patient With Newly Diagnosed Leukemia

Idiopathic hyperammonemia (IHA) has been described as a complication of intensive chemotherapy for the treatment of hematologic malignancy but has subsequently been found in patients undergoing bone marrow transplantation and in those with solid tumors treated with 5-fluorouracil. Although IHA is a rare complication, it is sometimes associated with high mortality in hematologic malignancies. Here we report the case of a 15-year-old boy in whom hyperammonemia developed during the initial treatment with prednisolone for newly diagnosed acute lymphoblastic leukemia and who survived after early detection and oral lactulose therapy. To the best of our knowledge, this is the first report of IHA that was not induced by intensive chemotherapy, stem cell transplantation, or asparaginase therapy in a patient with newly diagnosed leukemia, but developed during an initial treatment with a steroid. Early detection of IHA by measuring the plasma ammonia level in patients with neurological symptoms may improve the outcome.

Idiopathic hyperammonemia after hematopoietic stem cell transplantation: A case report

IHA is characterized by a sudden increase in plasma ammonia levels in the absence of any identifiable causes, which mostly results in intractable coma and high mortality. It has been reported in some patients after receiving intensive chemotherapy for hematological malignancy or HSCT. We describe a case of a patient with FA that developed acute idiopathic hyperammonemia after the preparative regimen for HSCT.

Fatal hyperammonemia and carbamoyl phosphate synthetase 1 (CPS1) deficiency following high-dose chemotherapy and autologous hematopoietic stem cell transplantation

Fatal hyperammonemia secondary to chemotherapy for hematological malignancies or following bone marrow transplantation has been described in few patients so far. In these, the pathogenesis of hyperammonemia remained unclear and was suggested to be multifactorial. We observed severe hyperammonemia (maximum 475 μmol/L) in a 2-year-old male patient, who underwent high-dose chemotherapy with carboplatin, etoposide and melphalan, and autologous hematopoietic stem cell transplantation for a neuroblastoma stage IV. Despite intensive care treatment, hyperammonemia persisted and the patient died due to cerebral edema. The biochemical profile with elevations of ammonia and glutamine (maximum 1757 μmol/L) suggested urea cycle dysfunction. In liver homogenates, enzymatic activity and protein expression of the urea cycle enzyme carbamoyl phosphate synthetase 1 (CPS1) were virtually absent. However, no mutation was found in CPS1 cDNA from liver and CPS1 mRNA expression was only slightly decreased. We therefore hypothesized that the acute onset of hyperammonemia was due to an acquired, chemotherapy-induced (posttranscriptional) CPS1 deficiency. This was further supported by in vitro experiments in HepG2 cells treated with carboplatin and etoposide showing a dose-dependent decrease in CPS1 protein expression. Due to severe hyperlactatemia, we analysed oxidative phosphorylation complexes in liver tissue and found reduced activities of complexes I and V, which suggested a more general mitochondrial dysfunction. This study adds to the understanding of chemotherapy-induced hyperammonemia as drug-induced CPS1 deficiency is suggested. Moreover, we highlight the need for urgent diagnostic and therapeutic strategies addressing a possible secondary urea cycle failure in future patients with hyperammonemia during chemotherapy and stem cell transplantation.