Hyperammonemia in the ICU

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.

Ammonia in liver diseases: A glimpse into the controversies and consensus

Ammonia is a byproduct of the metabolism of nitrogen-containing micro and macromolecules. The key source of bodily ammonia in humans is the small intestine, from diet, luminal bacterial activity, and deamination of glutamine in enterocytes. It is disposed of from the system, mainly in the liver, through the urea cycle. Physiologically, ammonia plays a minor role in acid-base homeostasis. It is the critical molecule implicated in the pathogenesis of hepatic encephalopathy. Liver disease is the most common cause of hyperammonemia, while others include urea cycle defects, infections, and drugs. The diagnostic utility of ammonia in liver diseases has met with increasing skepticism but holds good in urea cycle defects. Additionally, the accuracy of ammonia assay depends on a myriad of patient and technical factors, making the test unreliable if not performed meticulously. Most scientific societies currently fall short of recommending ammonia for diagnostic purposes in chronic liver disease. Despite this fact, ammonia continues to be one of the most frequently requested assays in patients with suspected hepatic encephalopathy, contributing to significant non-productive health expenditure. However, ammonia level does have a prognostic role in liver diseases, especially in acute liver failure. Ammonia-lowering strategies are the cornerstone of the management of hepatic encephalopathy. These strategies include medications that attenuate ammoniagenesis and ammonia scavengers. This review examines the role of ammonia in hepatic encephalopathy, its diagnostic and prognostic implications in liver diseases, challenges associated with ammonia assay, and current therapeutic strategies for ammonia-lowering in clinical practice.

Hyperosmolarity in children with hyperammonemia: a risk of brain herniation at the start of renal replacement therapy

Purpose

Renal replacement therapy (RRT) is used in hyperammonemia to reduce the concentration of ammonia in the blood. In the case of plasma hyperosmolarity, RRT can also rapidly decrease plasma osmolarity, which may increase cerebral edema in these patients and favor the occurrence of brain herniation.

Methods

We conducted a retrospective clinical study in a tertiary care university-affiliated hospital. All patients admitted in a Pediatric Intensive Care Unit (PICU), less than 18 years old with ammonemia >150 µmol/L and who underwent RRT between January 2015 and June 2023 were included. We collected data on plasma osmolarity levels, osmolar gap and blood ammonia levels before and during RRT.

Results

Eleven patients were included (10 with acute liver failure and 1 with a urea cycle disorders). Their mean age was 36.2 months. Before RRT, the median highest measured osmolarity was 320 (305-324) mOsm/L, whereas the median calculated osmolarity was 303 (293-314) mOsm/L, corresponding to an osmolar gap of 14 mOsm/L. Ammonia blood level over 400 µmol/L are significantly associated with higher plasma osmolarity (P-Value <0.001). In one case, a patient had a brain herniation episode after a quick osmolar drop. This episode was reversed by the administration of hyperosmolar agents and the temporary suspension of RRT.

Conclusion

This study highlights the hyperosmolarity and high osmolar gap that occur in children with hyperammonemia. A careful monitoring and control of plasma osmolarity evolution may alert clinician on the risk of occurrence of neurological complication such as brain herniation.

A late-onset hyperammonemia syndrome caused by Ureaplasma parvum infection after kidney transplantation

Hyperammonemia syndrome has a high mortality rate in the immunosuppressed population due to its association with mental status changes. Recently studies have shown that Ureaplasma organisms' infection can lead to hyperammonemia in post-transplant patients. Symptoms typically occur within 30 days postoperatively. However, the late-onset hyperammonemia caused by Ureaplasma parvum infection after kidney transplantation has never been reported. In this case study, a 64-year-old Chinese male presented with symptoms such as nausea, vomiting, trouble sleeping, and deteriorating mental status 81 days after kidney transplantation. His plasma ammonia level was significantly elevated, and there was no evidence of liver synthetic dysfunction. Although common methods for ammonia clearance, such as haemodialysis and oral lactulose were initiated, his serum ammonia levels remained high. Metagenomic sequencing of serum determined Ureaplasma parvum infection. Levofloxacin and minocycline were administered respectively, which resulted in a decrease in ammonia levels, but normalization was not achieved. The computed tomographic scan revealed the presence of cerebral edema. Unfortunately, the patient eventually became brain dead with multiple organ failure. This case highlights that Ureaplasma parvum can cause late-onset hyperammonemia in kidney transplant patients. Once the mental status changes are identified, immediate empiric treatments should be initiated without waiting for a confirmed diagnosis of Ureaplasma spp. infection.

Prognostic value of serum ammonia in critical patients with non-hepatic disease: A prospective, observational, multicenter study

Background and Objectives

Non-hepatic hyperammonemia can damage the central nervous system (CNS), and possible prognostic factors are lacking. This study aimed to investigate the prognostic and risk factors for patients admitted to the intensive care unit (ICU).

Materials and Methods

This prospective, observational, multicenter study was conducted between November and December 2019 at 11 ICUs in the Chinese Heilongjiang province. Changes in blood ammonia level during and after ICU admission were continuously monitored and expressed as the high level (H-), mean level (M-), and initial level (I-) of ammonia. The risk factors of poor prognosis were investigated by conducting univariate and multivariate logistic regression analyses. Receiver operating characteristic (ROC) curve analysis was conducted to compare the predictive ability of Acute Physiologic Assessment and Chronic Health Evaluation II (APACHE-II) score, lactic acid, total bilirubin (TBil), and M-ammonia.

Results

A total of 1060 patients were included in this study, of which 707 (67%) had a favorable prognosis and 353 (33%) had a poor prognosis. As shown by univariate models, a poor prognosis was associated with elevated serum levels of lactic acid, TBil, and ammonia (P < 0.05) and pathologic scores from three assessments: APACHE-II, Glasgow Coma Scale (GCS), and Sequential Organ Failure Assessment (SOFA). Multivariate analysis revealed that circulating mean ammonia levels in ICU patients were independently associated with a poor prognosis (odds ratio [OR] = 1.73, 95% confidence interval [CI]: 1.07-2.80, P = 0.02). However, the APACHE-II score (area under the curve [AUC]: 0.714, sensitivity: 0.86, specificity: 0.68, P < 0.001) remained the most predictive factor for patient prognosis by ROC analysis.

Conclusion

Elevated serum levels of ammonia in the blood were independently prognostic for ICU patients without liver disease.

Treatment of Hyperammonemia Syndrome in Lung Transplant Recipients

Hyperammonemia syndrome is a complication that has been reported to occur in 1-4% of lung transplant patients with mortality rates as high as 60-80%, making detection and management crucial components of post-transplant care. Patients are treated with a multimodal strategy that may include renal replacement therapy, bowel decontamination, supplementation of urea cycle intermediates, nitrogen scavengers, antibiotics against Mollicutes, protein restriction, and restriction of parenteral nutrition. In this review we provide a framework of pharmacologic mechanisms, medication doses, adverse effects, and available evidence for commonly used treatments to consider when initiating therapy. In the absence of evidence for individual strategies and conclusive knowledge of the causes of hyperammonemia syndrome, clinicians should continue to design multimodal regimens based on suspected etiologies, institutional drug availability, patient ability to tolerate enteral medications and nutrition, and availability of intravenous access.

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.

Hyperammonemia Syndrome After Lung Transplantation: A Double-Hit Fatal Syndrome. A Case Report

Hyperammonemia after lung transplantation is a rare but potentially fatal condition. A 59-year-old male patient affected by pulmonary fibrosis underwent an uncomplicated bilateral lung transplant. Fourteen days after the procedure, the patient developed severe encephalopathy caused by elevated serum ammonia levels. Ureaplasma parvum and Mycoplasma hominis were found on bronchial aspirate and urinary samples as well as on pharyngeal and rectal swabs. Despite the initiation of multimodal therapy, brain damage due to hyperosmolarity was so extensive to evolve into brain death. The autopsy revealed glutamine synthetase hypo-expression in the hepatic tissue. The pathophysiology of hyperammonemia syndrome in lung transplant recipients remains unclear. Previous studies have described the presence of disorders of glutamine synthetase, while others considered the infection with urea-splitting microorganisms as a cause of hyperammonemia syndrome. Our report describes the case of a patient who developed hyperammonemia after a lung transplant in which both the aforementioned etiologies were documented. A high level of clinical suspicion for hyperammonemia syndrome should be maintained in lung transplant recipients. Timely recognition and treatment are critical to prevent the potentially dreadful evolution of this severe complication.

Recurrent Non-cirrhotic Hyperammonemic Encephalopathy Due to Complicated Urinary Tract Infection: A Case Report

Hyperammonemic encephalopathy (HE) can be broadly defined as an alteration in the level of consciousness due to elevated blood ammonia level. While hepatic cirrhosis is the most common cause of HE, non-hepatic causes like drugs, infections, and porto-systemic shunts can also lead to the presentation. In this case, we highlight an unusual occurrence of recurrent non-cirrhotic HE from obstructive urinary tract infection (UTI) with urea-splitting micro-organisms in an elderly male patient. The patient exhibited altered mentation, and elevated ammonia levels with normal hepatic function at presentation. Urine culture revealed Proteus mirabilis resistant to extended spectrum beta-lactamases (ESBL). Successful management of obstructive UTI was achieved through Foley's catheterization and intravenous (IV) antibiotics, resulting in the resolution of HE. This outcome further supports the significance of UTI as a potential cause of hyperammonemia. Thus, UTI as one of the non-hepatic causes of hyperammonemia should always be explored among elderly patients presenting with altered mentation.

Hyperammonaemia syndrome in disseminated Ureaplasma parvum infection

Hyperammonaemia syndrome secondary to Ureaplasma spp. infection is well documented in the post-lung transplant population. We report a case of a man in his fifties with hyperammonaemia syndrome secondary to disseminated Ureaplasma parvum infection. This occurred in the context of immunosuppression for chronic graft versus host disease and six years following an allogeneic stem cell transplant for diffuse large B-cell lymphoma. Following treatment of U. parvum septic arthritis with ciprofloxacin and doxycycline, the patient experienced a full neurological recovery, and continues on suppressive doxycycline therapy with no recurrence of symptoms to date.

Status Epilepticus in Post-Transplantation Hyperammonemia Involves Careful Metabolic Management

Hyperammonemia is a condition that may result after solid organ transplantation, particularly lung transplantation. However, it is very uncommon for this presentation to occur more than 30 days post-transplantation. Hyperammonemia and the resulting encephalopathy typically manifest with altered sensorium, a clinical situation which is not often included in the differential diagnosis of presumed nonconvulsive status epilepticus (NCSE). Seizures are common among this subset of patients with hyperammonemia and may be refractory to traditional treatments. Evidence of elevated intracranial pressure by invasive monitoring and neuroimaging findings of diffuse cerebral edema are commonly reported. Here we examine the therapeutic importance of identifying the specific cause of hyperammonemic encephalopathy, a condition which may result in status epilepticus and ultimately cerebral edema or even brain death.

Proton magnetic resonance spectroscopy assessment of neonatal brain metabolism during cardiopulmonary bypass surgery

Here, we report on the development and performance of a robust 3-T single-voxel proton magnetic resonance spectroscopy (¹ H MRS) experimental protocol and data analysis pipeline for quantifying brain metabolism during cardiopulmonary bypass (CPB) surgery in a neonatal porcine model, with the overall goal of elucidating primary mechanisms of brain injury associated with these procedures. The specific aims were to assess which metabolic processes can be reliably interrogated by ¹ H MRS on a 3-T clinical scanner and to provide an initial assessment of brain metabolism during deep hypothermia cardiac arrest (DHCA) surgery and recovery. Fourteen neonatal pigs underwent CPB surgery while placed in a 3-T MRI scanner for 18, 28, and 37°C DHCA studies under hyperglycemic, euglycemic, and hypoglycemic conditions. Total imaging times, including baseline measurements, circulatory arrest (CA), and recovery averaged 3 h/animal, during which 30-40 single-voxel ¹ H MRS spectra (sLASER pulse sequence, TR/TE = 2000/30 ms, 64 or 128 averages) were acquired from a 2.2-cc right midbrain voxel. ¹ H MRS at 3 T was able to reliably quantify (1) anaerobic metabolism via depletion of brain glucose and the associated build-up of lactate during CA, (2) phosphocreatine (PCr) to creatine (Cr) conversion during CA and subsequent recovery upon reperfusion, (3) a robust increase in the glutamine-to-glutamate (Gln/Glu) ratio during the post-CA recovery period, and (4) a broadening of the water peak during CA. In vivo ¹ H MRS at 3 T can reliably quantify subtle metabolic brain changes previously deemed challenging to interrogate, including brain glucose concentrations even under hypoglycemic conditions, ATP usage via the conversion of PCr to Cr, and differential changes in Glu and Gln. Observed metabolic changes during CPB surgery of a neonatal porcine model provide new insights into possible mechanisms for prevention of neuronal injury.

Ornithine Transcarbamylase Deficiency Presenting as Acute Encephalopathy After Strabismus Surgery

Acute encephalopathy with an unclear etiology is a common presentation to the hospital. We describe the case of a 50-year-old male who presented with a one-day history of slurred speech, nausea, insomnia, and altered mental status. His surgical history was notable for a strabismus surgery two days ago. He presented with elevated ammonia levels that continued to increase. Metabolic studies were suggestive of hyperammonemia secondary to ornithine transcarbamylase (OTC) deficiency triggered due to fasting prior to the strabismus surgery. OTC gene sequencing confirmed the diagnosis of OTC deficiency. We summarize the current case reports in the literature and review the treatment options for OTC deficiency. Our case occurred after a low-risk outpatient strabismus surgery and is a good example of maintaining a broad differential and revising the suspected diagnosis constantly.

Drug-associated hyperammonaemia: a Bayesian analysis of the WHO Pharmacovigilance Database

Background

Hyperammonaemia is frequent in Intensive Care Unit patients. Some drugs have been described as associated with this condition, but there are no large-scale studies investigating this topic and most descriptions only consist of case-reports.

Methods

We performed a disproportionality analysis using VigiBase, the World Health Organization Pharmacovigilance Database, using the information component (IC). The IC compares observed and expected values to find associations between drugs and hyperammonaemia using disproportionate Bayesian reporting. An IC_0.25 (lower end of the IC 95% credibility interval) > 0 is considered statistically significant. The main demographic and clinical features, confounding factors, and severity of cases have been recorded.

Results

We identified 71 drugs with a disproportionate reporting in 2924 cases of hyperammonaemia. Most of the suspected drugs could be categorised into 4 main therapeutic classes: oncologic drugs, anti-epileptic drugs, immunosuppressants and psychiatric drugs. The drugs most frequently involved were valproic acid, fluorouracil, topiramate, oxaliplatin and asparaginase. In addition to these molecules known to be responsible for hyperammonaemia, our study reported 60 drugs not previously identified as responsible for hyperammonaemia. These include recently marketed molecules including anti-epileptics such as cannabidiol, immunosuppressants such as basiliximab, and anti-angiogenics agents such as tyrosine kinase inhibitors (sunitinib, sorafenib, regorafenib, lenvatinib) and monoclonal antibodies (bevacizumab, ramucirumab). The severity of cases varies depending on the drug class involved and high mortality rates are present when hyperammonaemia occurs in patients receiving immunosuppressant and oncologic drugs.

Conclusions

This study constitutes the first large-scale study on drug-associated hyperammonaemia. This description may prove useful for clinicians in patients’ care as well as for trial design.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01026-4.

Epidemiology, Clinical Presentation and Treatment of Non-Hepatic Hyperammonemia in ICU COVID-19 Patients

(1) Background: Although COVID-19 is largely a respiratory disease, it is actually a systemic disease that has a wide range of effects that are not yet fully known. The aim of this study was to determine the incidence, predictors and outcome of non-hepatic hyperammonemia (NHH) in COVID-19 in intensive care unit (ICU); (2) Methods: This is a 3-month prospective observational study in a third-level COVID-19 hospital. The authors collected demographic, clinical, severity score and outcome data. Logistic regression analyses were performed to identify predictors of NHH; (3) Results: 156 COVID-19 patients were admitted to the ICU. The incidence of NHH was 12.2% (19 patients). The univariate analysis showed that invasive mechanical ventilation had a 6.6-fold higher risk (OR 6.66, 95% CI 0.86–51.6, p = 0.039) for NHH, while in the multiple regression analysis, there was a 7-fold higher risk for NHH—but it was not statistically significant (OR 7.1, 95% CI 0.90–56.4, p = 0.062). Demographics, clinical characteristics and mortality in the ICU at 28 days did not show a significant association with NHH. (4) Conclusions: The incidence of NHH in ICU COVID-19 patients was not low. NHH did not appear to significantly increase mortality, and all patients with non-hepatic hyperammonemia were successfully treated without further complications. However, the pathogenesis of NHH in ICU patients with COVID-19 remains a topic to be explored with further research.

Undifferentiated non-hepatic hyperammonemia in the ICU: Diagnosis and management

Hyperammonemia occurs frequently in the critically ill but is largely confined to patients with hepatic dysfunction or failure. Non-hepatic hyperammonemia (NHHA) is far less common but can be a harbinger of life-threatening diagnoses that warrant timely identification and, sometimes, empiric therapy to prevent seizures, status epilepticus, cerebral edema, coma and death; in children, permanent cognitive impairment can result. Subsets of patients are at particular risk for developing NHHA, including the organ transplant recipient. Unique etiologies include rare infections, such as with Ureaplasma species, and unmasked inborn errors of metabolism, like urea cycle disorders, must be considered in the critically ill. Early recognition and empiric therapy, including directed therapies towards these rare etiologies, is crucial to prevent catastrophic demise. We review the etiologies of NHHA and highlight the first presentation of it associated with a concurrent Ureaplasma urealyticum and Mycoplasma hominis infection in a previously healthy individual with polytrauma. Based on this clinical review, a diagnostic and treatment algorithm to identify and manage NHHA is proposed.

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.

Hyperammonemia during treatment with valproate in critically ill patients

INTRODUCTION

Hyperammonemia (HA) is a potential side-effect of valproate (VPA) treatment, which has been described during long-term administration. The aim of this study was to evaluate the incidence, the impact and the risk factors of HA in critically ill patients.

METHODS

We reviewed the data of all adult patients treated in our mixed 35-bed Department of Intensive Care over a 12-year period (2004-2015) who: a) were treated with VPA for more than 72 h and b) had at least one measurement of ammonium and VPA levels during the ICU stay; patients with Child-Pugh C liver cirrhosis were excluded. HA was defined as ammonium levels above 60 μg/dl.

RESULTS

Of a total of 2640 patients treated with VPA, 319 patients met the inclusion criteria (median age 64 years; male gender 55%); 78% of them were admitted for neurological reasons and ICU mortality was 30%. Median ammonium levels were 88 [63-118] µg/dl. HA was found in 245 (77%) patients. For those patients with HA, median time from start of VPA therapy to HA was 3 [2-5] days. In a multivariable analysis, high VPA serum levels, mechanical ventilation and sepsis were independently associated with HA during VPA therapy. In 98/243 (40%) of HA patients, VPA was interrupted; VPA interruption was more frequent in patients with ammonium levels > 100 μg/dl than others (p = 0.001). HA was not an independent predictor of ICU mortality or poor neurological outcome.

CONCLUSIONS

In this study, HA was a common finding during treatment with VPA in acutely ill patients. VPA levels, sepsis and mechanical ventilation were risk factors for HA. Hyperammonemia did not influence patients' outcome.

Unexplained Fatal Hyperammonemia in a Patient With New Diagnosis of Acute Monoblastic Leukemia

Idiopathic hyperammonemia is a serious condition that can arise after induction of chemotherapy and is characterized by plasma ammonia levels greater than two times the normal upper limit but within the context of normal liver function. While this dangerous complication usually appears several weeks after the start of chemotherapy, we report a fatal case of idiopathic hyperammonemia that was detected only nine days after induction chemotherapy in a 22-year-old man with no liver pathology or other risks for hyperammonemia. The patient’s initial emergent presentation was altered mental status. Laboratory workup showed acute monoblastic leukemia and radiological investigation showed cerebral hemorrhagic foci secondary to leukostasis. He received leukoreduction apheresis and he was started on induction chemotherapy with daunorubicin and cytarabine. On the ninth day of induction chemotherapy, it was noted that he developed worsening neurological findings. Investigations showed significant elevation in ammonia level and associated cerebral edema. Although hyperammonemia was mitigated, the patient’s cerebral status worsened and he died 15 days after initial presentation. This case shows that critical hyperammonemia can occur quickly after chemotherapy induction and that strategies for preventing a rise in plasma ammonia are necessary.

Evaluation of levocarnitine, lactulose, and combination therapy for the treatment of valproic acid-induced hyperammonemia in critically ill patients

INTRODUCTION

Critically ill patients treated with valproic acid are at risk for hyperammonemic encephalopathy. Both levocarnitine and lactulose, either alone or in combination, have been used for the treatment of hyperammonemia associated with valproic acid, however they have not been directly compared in the literature. The aim of this study was to compare the effect of levocarnitine, lactulose, and combination therapy for the treatment of valproic acid-induced hyperammonemia in critically ill patients.

METHODS

This was a retrospective, system-wide, cohort study of critically ill patients who received valproic acid and levocarnitine, lactulose, or combination therapy from January 1, 2012 to October 31, 2019. The primary outcome of the study was the change in ammonia level from baseline to the lowest point within the first 48 h of treatment. Secondary outcomes included the change in ammonia levels within the first 7 days, the incidence of a clinically significant reduction, ICU length of stay, hospital length of stay, and hospital mortality.

RESULTS

A total of 371 charts were reviewed and 114 patients (levocarnitine [n = 15], lactulose [n = 72], and combination [n = 27]) were included. No difference in the primary outcome was observed (levocarnitine [11umol/L] vs. lactulose [20 umol/L] vs. combination [23 umol/L], p = 0.605). The incidence of a clinically significant reduction in ammonia levels at 48 h did not differ between groups, nor did mortality.

CONCLUSION

In critically ill patients with valproic acid-induced hyperammonemia, there was no significant difference in the reduction in ammonia levels in the first 48 h of treatment between levocarnitine, lactulose, and combination therapy.

Impact of non-hepatic hyperammonemia on mortality in intensive care unit patients: a retrospective cohort study

BACKGROUND/AIMS

The effect of hyperammonemia on the mortality in patients with liver cirrhosis is well documented. However, little is known about the impact of hyperammonemia on mortality among intensive care unit patients without hepatic disease. We aimed to investigate factors associated with non-hepatic hyperammonemia among intensive care unit patients and to evaluate the factors related to the 7- and 90-day mortality.

METHODS

Between February 2016 and February 2020, 948 patients without hepatic disease who had 972 episodes of admission to the intensive care unit were retrospectively enrolled and classified as hyperammonemia grades 0 (≤ 80 µg/dL; 585 [60.2%]), 1 (≤ 160 µg/dL; 291 [29.9%]), 2 (≤ 240 µg/dL; 55 [5.7%]), and 3 (> 240 µg/dL; 41 [4.2%]). Factors associated with hyperammonemia and the 7- and 90-day mortality were evaluated by multivariate logistic regression analysis and Cox regression analysis, respectively. Kaplan-Meier survival curves for the 7- and 90-day mortality were constructed.

RESULTS

The independent risk factors for hyperammonemia were male sex (odds ratio, 1.517), age (0.984/year), acute brain failure (2.467), acute kidney injury (1.437), prothrombin time-international normalized ratio (2.272/unit), and albumin (0.694/g/dL). The 90-day mortality rate in the entire cohort was 24.3% and gradually increased with increasing hyperammonemia grade at admission (17.9%, 28.2%, 43.6%, and 61.0% in patients with grades 0, 1, 2, and 3, respectively). Additionally, non-hepatic hyperammonemia was an independent predictor of the 90- day mortality in intensive care unit patients.

CONCLUSION

Non-hepatic hyperammonemia is common (39.8%) and associated with the 90-day mortality among intensive care unit patients.

A Brief History of Hepatic Encephalopathy

Content available: Author Audio Recording.

Nonhepatic hyperammonemic encephalopathy complications following bariatric surgery: a case report and review of the literature

Background

Hyperammonemic encephalopathy, a rare but fatal condition, is increasingly being reported as a possible complication of bariatric surgery. Here, we present a case of hyperammonemic encephalopathy, focusing on the clinical presentation, diagnostic measures, and our treatment methods, which resulted in a rare favorable outcome, emphasizing the unique role of renal replacement treatment. We also provide a detailed discussion of the mechanism through which hyperammonemia occurs secondarily to bariatric surgery.

Case presentation

A 44-year-old Moroccan Jew woman with a history of obesity presented in the hospital with urea cycle disorder that manifested after bariatric surgery. A rapid diagnostic process, together with conservative treatment with lactulose, nutritional supplementation, dietary protein restriction, and ammonia scavengers did not result in adequate improvement. Therefore, hemofiltration was performed, which yielded a favorable outcome.

Conclusions

The case findings indicate an association between hyperammonemic encephalopathy and bariatric surgery, and support early treatment with ammonia scavengers, as currently accepted. Nevertheless, if rapid improvement is not seen, it is advisable to consider hemodialysis or hemofiltration as early invasive strategies.

Lethal hyperammonemia in a CAR-T cell recipient due to Ureaplasma pneumonia: a case report of a unique severe complication

We report the first incidence of Ureaplasma infection causing lethal hyperammonemia in a chimeric receptor antigen T cell (CAR-T) recipient. A 53-year-old woman, after receiving CAR-T therapy, suffered sepsis and encephalopathy. She was found to have hyperammonemia up to 643 µmol/L. Imaging revealed lung consolidations and bronchoalveolar lavage PCR was positive for U. parvum. Workup excluded liver failure and metabolic abnormalities. Antibiotics, lactulose, dextrose, arginine, levocarnitine, sodium phenylbutyrate and dialysis were used. Despite these, the patient suffered persistent elevations in ammonia, status epilepticus and cerebral oedema. Early recognition of this rare infection in susceptible populations is needed. CAR-T patients are at risk due to their immunocompromised state and may have amplified harm due to the impact of CAR-T therapy on astrocytes. An early aggressive multimodality approach is needed given the high mortality rates. These include antimicrobials, possibly with double coverage for Ureaplasma. Additionally, concurrent ammonia-suppressing and ammonia-eliminating treatments are necessary.

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.

Rapid Rescue From Hyperammonemic Coma After Valproic Acid Poisoning: Dual Therapy With Continuous Renal Replacement Therapy and L-Carnitine Supplementation

Valproic acid is a commonly prescribed drug used in various conditions including seizures, bipolar disorder, mood disorder, and migraine headaches. Confusion and lethargy among patients on valproic acid need urgent attention as it can cause increased levels of ammonia, which can lead to the development of cerebral edema and even cerebral herniation in severe cases. Here, we describe a case of hyperammonemic coma induced by valproic acid toxicity. The condition was rapidly resolved using dual therapy involving extracorporeal removal and levocarnitine.

Use of Lactulose to Treat Hyperammonemia in ICU Patients Without Chronic Liver Disease or Significant Hepatocellular Injury

OBJECTIVES

To review ICU patients with elevated ammonia without a clear hepatic etiology, to compare outcomes between those who received lactulose and those who did not.

DESIGN

Retrospective observational study.

SETTING

Medical, surgical, and subspecialty intensive care units at Wake Forest Baptist Medical Center, Winston-Salem, North Carolina between December 2012 and August 2016.

PATIENTS

Adults with ammonia levels above 50 μmol/L, excluding those with known chronic liver disease, inborn error of metabolism, active use of valproic acid, total bilirubin ≥ 2 μmol/L, or alanine aminotransferase ≥ 100 units/L.

INTERVENTIONS

Comparison in ICU length of stay (LOS), hospital LOS, in-hospital mortality, and mortality at 30 and 90 days.

MEASUREMENTS AND MAIN RESULTS

Criteria for inclusion were met in 103 cases. Mean ammonia level was 75 μmol/L, with undetermined etiology in the majority of subjects. Lactulose was given in 48 cases (46.6%), with a median of 9.5 doses given. There were no significant differences in outcomes between the lactulose and non-lactulose groups. Among subjects with multiple data points, lactulose did not have a dose-dependent effect on ammonia level, and was not associated with faster ammonia normalization compared to non-lactulose. When analyzed separately, patients with moderate hyperammonemia (60-99 μmol/L) who received lactulose had longer hospital and ICU length of stay compared to non-lactulose (417.8 hours vs. 208.4 hours, P = 0.003, and 229.2 hours vs. 104.7 hours, P = 0.025; respectively), though confounders were present.

CONCLUSIONS

Routine use of lactulose to treat mild to moderate hyperammonemia in this patient population was not associated with improved outcomes.

Hyperammonemia syndrome associated with Ureaplasma spp. Infections in immunocompromised patients and transplant recipients: A systematic review and meta-analysis

BACKGROUND

Hyperammonemia syndrome (HS) is reported to occur in patients with Ureaplasma spp. infections. We performed a systematic review and meta-analysis of studies reporting HS in patients with Ureaplasma spp. infection.

METHODS

We searched several databases (CINAHL, OVID, ProQuest, and Scopus) from inception to January 2021. We described case reports and series, and performed a meta-analysis for all cohort studies. The pooled risk ratio (RR) for the association between HS and Ureaplasma spp. infections was derived using a random-effects model.

RESULTS

The systematic review yielded 18 studies. HS was reported in 53 patients with Ureaplasma spp. infections. The most common clinical manifestations were neurologic. Meta-analysis showed a higher incidence of HS (41.67%) and peak ammonia concentration among Ureaplasma spp.-infected lung transplant recipients compared with Ureaplasma spp.-negative recipients (2.84%). The risk of HS was significantly increased in Ureaplasma spp.-infected recipients compared with Ureaplasma spp.-negative recipients (RR: 14.64; CI: 2.85-75.24). Mortality from Ureaplasma-associated HS was 27.27% compared with 5.24% in those with HS from other causes.

CONCLUSIONS

The risk of developing HS is higher among Ureaplasma-infected patients compared with uninfected patients. Lung transplant recipients appear to be disproportionally affected, and HS should be suspected in those who present with neurologic symptoms.

Hyperammonemia after Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy: A Report of Three Cases with Unusual Presentation

Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) is a treatment modality for peritoneal surface malignancies. A variety of metabolic derangements have been reported in the perioperative period in these patients, most of which are a result of the complex interaction of peritoneal denudation, chemotherapy bath, and fluid imbalance. We report three cases of hyperammonemia-related neurological dysfunction seen in HIPEC patients. To the best of our knowledge, this is the first report of this presentation. Timely recognition of this condition needs a high degree of suspicion, and unless aggressively treated, is likely to be associated with poor outcome. How to cite this article: Sharma V, Solanki SL, Saklani AP. Hyperammonemia after Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy: A Report of Three Cases with Unusual Presentation. Indian J Crit Care Med 2021;25(5):590-593.

Management of late onset urea cycle disorders-a remaining challenge for the intensivist?

Background

Hyperammonemia caused by a disorder of the urea cycle is a rare cause of metabolic encephalopathy that may be underdiagnosed by the adult intensivists because of its rarity. Urea cycle disorders are autosomal recessive diseases except for ornithine transcarbamylase deficiency (OTCD) that is X-linked. Optimal treatment is crucial to improve prognosis.

Main body

We systematically reviewed cases reported in the literature on hyperammonemia in adulthood. We used the US National Library of Medicine Pubmed search engine since 2009. The two main causes are ornithine transcarbamylase deficiency followed by type II citrullinemia. Diagnosis by the intensivist remains very challenging therefore delaying treatment and putting patients at risk of fatal cerebral edema. Treatment consists in adapted nutrition, scavenging agents and dialysis. As adults are more susceptible to hyperammonemia, emergent hemodialysis is mandatory before referral to a reference center if ammonia levels are above 200 µmol/l as the risk of cerebral edema is then above 55%. Definitive therapy in urea cycle abnormalities is liver transplantation.

Conclusion

Awareness of urea cycle disorders in adults intensive care units can optimize early management and accordingly dramatically improve prognosis. By preventing hyperammonemia to induce brain edema and herniation leading to death.

Glucagon Receptor Inhibition Reduces Hyperammonemia and Lethality in Male Mice with Urea Cycle Disorder

The liver plays a critical role in maintaining ammonia homeostasis. Urea cycle defects, liver injury, or failure and glutamine synthetase (GS) deficiency result in hyperammonemia, serious clinical conditions, and lethality. In this study we used a mouse model with a defect in the urea cycle enzyme ornithine transcarbamylase (Otcspf-ash) to test the hypothesis that glucagon receptor inhibition using a monoclonal blocking antibody will reduce the hyperammonemia and associated lethality induced by a high-protein diet, which exacerbates disease. We found reduced expression of glutaminase, which degrades glutamine and increased expression of GS in livers of Otcspf-ash mice treated with the glucagon receptor blocking antibody. The gene expression changes favor ammonia consumption and were accompanied by increased circulating glutamine levels and diminished hyperammonemia. Otcspf-ash mice treated with the glucagon receptor-blocking antibody gained lean and body mass and had increased survival. These data suggest that glucagon receptor inhibition using a monoclonal antibody could reduce the risk for hyperammonemia and other clinical manifestations of patients suffering from defects in the urea cycle, liver injury, or failure and GS deficiency.

Increasing serum ammonia level is a risk factor for the prognosis of critically ill patients: A multicenter retrospective cohort study

PURPOSE

To assess the association between serum ammonia level upon admission during the initial intensive care unit (ICU) stay and mortality.

MATERIALS AND METHODS

This retrospective cohort study included 2703 adult patients in eICU Collaborative Research Database. The ICU mortality within ammonia deciles were assessed. Logistic regression analyses were performed to analyze the relationship between ammonia and mortality.

RESULTS

We defined three ammonia categories: <47, 47-111, and ≥111 μg/dL, corresponding to low, intermediate, and high ICU mortality. Increased ammonia was significantly associated with increased ICU mortality (per 10 μg/dL increase: odds ratio, 1.070 [95% confidence intervals, 1.05-1.09]; intermediate vs. low: 1.90 [1.41-2.56]; high vs. low: 4.38 [2.99-6.41]) and in-hospital mortality (1.06 [1.04-1.08]; 1.45 [1.13-1.87]; 3.41 [2.43-4.79]). Adding ammonia to the Acute Physiology and Chronic Health Evaluation (APACHE) IV score improved the area under the curve from 0.826 to 0.839 (P < 0.001) and from 0.806 to 0.813 (P = 0.001) for ICU and in-hospital mortality, respectively. Interaction and subgroup analyses demonstrated consistent results in patients with different APACHE IV scores, with or without hepatic diseases.

CONCLUSIONS

Elevated serum ammonia level in critically ill patients upon admission was an early risk factor for higher ICU and in-hospital mortality.

Relationship between the incidence of non-hepatic hyperammonemia and the prognosis of patients in the intensive care unit

BACKGROUND

Ammonia is a normal constituent of body fluids and is found mainly through the formation of urea in the liver. Blood levels of ammonia must remain low as even slightly elevated concentrations (hyperammonemia) are toxic to the central nervous system.

AIM

To examine the relationship between the incidence of non-hepatic hype-rammonemia (NHH) and the prognosis of patients who were admitted to the intensive care unit (ICU).

METHODS

This is a prospective, observational and single-center study. A total of 364 patients who were admitted to the ICU from November 2019 to February 2020 were initially enrolled. Changes in the levels of blood ammonia at the time of ICU admission and after ICU admission were continuously monitored. In addition, factors influencing the prognosis of NHH patients were analyzed.

RESULTS

A total of 204 patients who met the inclusion criteria were enrolled in this study, including 155 NHH patients and 44 severe-NHH patients. The incidence of NHH and severe-NHH was 75.98% and 21.57%, respectively. Patients with severe-NHH exhibited longer length of ICU stay and higher Acute Physiologic Assessment and Chronic Health Evaluation and Sequential Organ Failure Assessment scores compared to those with mild-NHH and non-NHH. Glasgow Coma Scale scores of patients with severe-NHH were than those of non-NHH patients. In addition, the mean and initial levels of ammonia in the blood might be helpful in predicting the prognosis of NHH.

CONCLUSION

High blood ammonia level is frequent among NHH patients admitted to the ICU, which is related to the clinical characteristics of patients. Furthermore, the level of blood ammonia may be helpful for prognosis prediction.

Hyperammonemia Post Lung Transplantation: A Review

Hyperammonemia is the pathological accumulation of ammonia in the blood, which can occur in many different clinical settings. Most commonly in adults, hyperammonemia occurs secondary to hepatic dysfunction; however, it is also known to be associated with other pathologies, surgeries, and medications. Although less common, hyperammonemia has been described as a rare, but consistent complication of solid organ transplantation. Lung transplantation is increasingly recognized as a unique risk factor for the development of this condition, which can pose grave health risks-including long-term neurological sequelae and even death. Recent clinical findings have suggested that patients receiving lung transplantations may experience postoperative hyperammonemia at rates as high as 4.1%. A wide array of etiologies has been attributed to this condition. A growing number of case studies and investigations suggest disseminated opportunistic infection with Ureaplasma or Mycoplasma species may drive this metabolic disturbance in lung transplant recipients. Regardless of the etiology, hyperammonemia presents a severe clinical problem with reported mortality rates as high as 75%. Typical treatment regimens are multimodal and focus on 3 main avenues of management: (1) the reduction of impact on the brain through the use of neuroprotective medications and decreasing cerebral edema, (2) augmentation of mechanisms for the elimination of ammonia from the blood via hemodialysis, and (3) the diminishment of processes producing predominantly using antibiotics. The aim of this review is to detail the pathophysiology of hyperammonemia in the setting of orthotopic lung transplantation and discuss methods of identifying and managing patients with this condition.

Prognostic Role of Ammonia in Critical Care Patients Without Known Hepatic Disease

Background and Aims: Hyperammonemia usually develops because of hepatic disease, but it may occur in patients with non-hepatic hyperammonemia (NHH). But, studies on the prognosis and possible risk factors of this disorder are lacking. The aim of this study was to find possible prognostic and risk factors for NHH in critically ill patients.

Methods: Data were extracted from MIMIC III Database. Survival was analyzed by the Kaplan-Meier method. Univariate and multivariate analyses were performed to identify prognostic factors.

Results: Valproic acid, carbamazepine, corticosteroids, recent orthopedic surgery, epilepsy, disorders of urea cycle metabolism, and obesity were found to be risk factors for NHH. Patients in the hyperammonemia group had a higher 30 day mortality than those in the non-hyperammonemia group. After final regression analysis, ammonia was found to be independent predictors of mortality.

Conclusion: Ammonia was an independent prognostic predictor of 30 day mortality for critical care patients without liver disease.

Delayed Cerebral Abnormalities in Acute Hyperammonemic Encephalopathy

Acute hyperammonemic encephalopathy (AHE) is a rare but life-threatening condition. We present a case of an 81-year-old woman with cirrhotic AHE who presented with prolonged disorientation. Her magnetic resonance (MR) images were normal on the third hospital day, which showed bilateral abnormalities in the insular and cingulate cortices on day 13. The imaging abnormalities were slightly improved but remained on day 24. The imaging abnormalities seemed correlated with her persistent disorientation. AHE can present as delayed cerebral abnormalities, and follow-up imaging tests are useful in detecting such conditions. Further reports are needed to investigate the correlation between imaging abnormalities and clinical outcomes in patients with AHE.

Non-Lactulose Medication Therapies for the Management of Hepatic Encephalopathy: A Literature Review

OBJECTIVE

The most appropriate medication regimen to mitigate the consequences hepatic encephalopathy remains inconclusive. This review seeks to serve as a reference for clinicians to help guide therapy decisions with regard to hepatic encephalopathy.

METHODS

A comprehensive literature review between August 2018 and April 2019 was accomplished with the assistance of a medical librarian. Sources of literature review include PubMed, MEDLINE, SCOPUS, ProQuest Central, CINAHL, and ProQuest Dissertations. The authors selected randomized clinical and double-blind cross-over trials evaluating probiotics, zinc, polyethylene glycol, rifaximin, and flumazenil. Sixteen clinical trials are discussed in this review. Pertinent safety, efficacy, and statistical and clinical outcomes are summarized by the authors.

CONCLUSIONS

The most appropriate regimen to mitigate the consequences of hepatic encephalopathy remains elusive; however, the agents discussed within this review offer alternative options for patients unresponsive to or intolerant of traditional lactulose therapy. This review seeks to serve as a repository for relevant clinical trials, and as a reference for clinicians to help guide therapy decisions.

Disturbance of consciousness due to hyperammonemia and lactic acidosis during mFOLFOX6 regimen: Case report

INTRODUCTION

FOLFOX therapy is the main chemotherapy regimen for colorectal cancer. Peripheral neuropathy, hematotoxicity, and digestive symptoms are known to be the most frequent adverse events. Hyperammonemia and lactic acidosis rarely occur simultaneously during treatment with FOLFOX therapy; the number of case reports is limited worldwide. We report a case of disturbance of consciousness, considered to be caused by hyperammonemia and lactic acidosis that occurred during treatment with mFOLFOX6 therapy that was administered as postoperative adjuvant treatment for rectal cancer.

PATIENT CONCERNS

This case was of a 71-year-old man who had been receiving oral treatment for chronic kidney disease and diabetes mellitus. Laparoscopic low anterior resection and artificial anal construction surgery were performed for stage III rectal cancer. As adjuvant postoperative therapy, mFOLFOX6 therapy was started but was followed by a disturbance of consciousness.

DIAGNOSES

Results of the blood tests revealed notable hyperammonemia (ammonia level, 1,163 μg/dl) and lactic acidosis (pH 7.207; lactate, 17.56 mmol/L); however, imaging diagnosis did not reveal intracranial lesions that could cause disturbance of consciousness.

INTERVENTIONS

For hyperammonemia, branched-chain amino acid agents and Ringers solution supplementation were administered. For acidosis, 7% sodium hydrogen carbonate was administered as treatment.

OUTCOMES

The disturbance of consciousness improved within 12 hours of initiating the treatment, and the patient was discharged with no sequelae on 7th day after hospitalization.

CONCLUSION

In patients with chronic kidney disease, FOLFOX regimen may confer risks of hyperammonemia and lactic acidosis.

Ureaplasma parvum causes hyperammonemia presenting as refractory status epilepticus after kidney transplant

PURPOSE

Alert intensivists about the diagnostic pitfalls arising from hyperammonemia due to Ureaplasma infections in post-transplant patients.

MATERIALS AND METHODS

Clinical observation of one patient.

CASE REPORT

A 65-year-old female with a medical history of semi-recent kidney transplant was admitted to the Intensive Care Unit for refractory status epilepticus. There were no lesions on brain imaging. Bacterial cultures and viral PCR of cerebrospinal fluid were negative. The first blood ammonia level measured on day 2 was 13 times the normal level, but biological liver tests were normal. The persistence of elevated ammonia levels led to the initiation of symptomatic ammonia lowering-treatments and continuous renal replacement therapy, which led to its decrease without normalization. An Ureaplasma spp infection was then diagnosed. Levofloxacin and doxycyline were administered resulting in normalization of ammonia levels within 48 h. However repeat MRI showed diffuse cortical cytotoxic edema and the patient remained in a minimally conscious state. She eventually died 4 months later from a recurrent infection.

CONCLUSION

Ureaplasma infection must be suspected in cases of neurological symptoms associated with hyperammonemia without liver failure, following an organ transplant. Only urgent treatment could improve the prognosis and prevent severe neurological damage or death.

Characteristics and outcomes of critically ill patients with severe hyperammonemia

PURPOSE

To determine the etiology and outcomes of critically ill patients with severe hyperammonemia.

MATERIALS AND METHODS

Retrospective observational study of adults (18 years or older) admitted to a MICU from 2007 to 2016 who had a serum ammonia level >180 μmol/L (3 times the upper limit of normal).

RESULTS

The 78 patients (45 male, 32 female) had a median age of 52 (interquartile range [IQR] 46-58) years. Hyperammonemia occurred most often with acute-on-chronic liver failure (ACLF) (49 %) or decompensated cirrhosis (27 %) and less often as a consequence of prior gastric bypass (9%), acute hepatic failure (6%), or valproic acid (3%). Median serum ammonia level was 201 μmol/L (IQR 126-265, range 18-736) on admission, with peak value of 245 μmol/L (IQR 205-336, range 185-842). Fifty (64%) patients died during the hospitalization. Cerebral edema was documented in 8 (10%) patients, only one of whom survived. Six of the 8 patients with cerebral edema had hyperammonemia related to ACLF, giving an incidence of 14% in this subset of patients. Neither mortality nor cerebral edema was associated with peak ammonia level.

CONCLUSIONS

Critically ill patients with severe hyperammonemia have a high mortality rate and are at risk of developing cerebral edema.

Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision

In 2012, we published guidelines summarizing and evaluating late 2011 evidence for diagnosis and therapy of urea cycle disorders (UCDs). With 1:35 000 estimated incidence, UCDs cause hyperammonemia of neonatal (~50%) or late onset that can lead to intellectual disability or death, even while effective therapies do exist. In the 7 years that have elapsed since the first guideline was published, abundant novel information has accumulated, experience on newborn screening for some UCDs has widened, a novel hyperammonemia-causing genetic disorder has been reported, glycerol phenylbutyrate has been introduced as a treatment, and novel promising therapeutic avenues (including gene therapy) have been opened. Several factors including the impact of the first edition of these guidelines (frequently read and quoted) may have increased awareness among health professionals and patient families. However, under-recognition and delayed diagnosis of UCDs still appear widespread. It was therefore necessary to revise the original guidelines to ensure an up-to-date frame of reference for professionals and patients as well as for awareness campaigns. This was accomplished by keeping the original spirit of providing a trans-European consensus based on robust evidence (scored with GRADE methodology), involving professionals on UCDs from nine countries in preparing this consensus. We believe this revised guideline, which has been reviewed by several societies that are involved in the management of UCDs, will have a positive impact on the outcomes of patients by establishing common standards, and spreading and harmonizing good practices. It may also promote the identification of knowledge voids to be filled by future research.