Recommendations for the Diagnosis and Therapeutic Management of Hyperammonaemia in Paediatric and Adult Patients

Critical care management of acute liver failure

The management of acute liver failure (ALF) in modern hepatology intensive care units (ICU) has improved patient outcomes. Critical care management of hepatic encephalopathy, cerebral edema, fluid and electrolytes; prevention of infections and organ support are central to improved outcomes of ALF. In particular, the pathogenesis of encephalopathy is multifactorial, with ammonia, elevated intra-cranial pressure and systemic inflammation playing a central role. Although ALF remains associated with high mortality, the availability of supportive care, including organ failure support such as plasma exchange, timely mechanical ventilation or continuous renal replacement therapy, either conservatively manages patients with ALF or offers bridging therapy until liver transplantation. Thus, appropriate critical care management has improved the likelihood of patient recovery in ALF. ICU care interventions such as monitoring of cerebral edema, fluid status assessment and interventions for sepsis prevention, nutritional support and management of electrolytes can salvage a substantial proportion of patients. In this review, we discuss the key aspects of critical care management of ALF.

Acceptability of plasma ammonia results when samples are not transported and processed under ideal conditions

BACKGROUND

It is recommended that samples for plasma ammonia analysis are kept chilled and processed promptly as in vitro metabolism causes falsely elevated results. Rejection of unsuitable samples can cause delayed diagnosis and treatment of hyperammonaemia with potentially serious clinical consequences. The Metabolic Biochemistry Network (MetBioNet) hyperammonaemia guideline recommends analysis of samples not collected under ideal conditions and reporting with appropriate comments. An audit found that some laboratories did not follow this guidance. An investigation was performed into whether storage at controlled room temperature and delayed sample processing affected interpretation of plasma ammonia results.

METHODS

Eleven healthy volunteers provided informed consent. Blood was taken from each into 14 paediatric EDTA blood sample tubes, one placed immediately on ice, the others in a rack at room temperature. The chilled and baseline room temperature samples were centrifuged and plasma analysed by the Roche Ammonia (NH3L2) method. Samples stored at room temperature were analysed at 10-min intervals up to 2 h.

RESULTS

Baseline room temperature ammonia was higher than in the chilled sample (19 ± 6.6 µmol/L [mean ± standard deviation] and 18 ± 6.6 µmol/L, respectively). Ammonia increased further by 0.09 ± 0.02 µmol/L per minute to 30 ± 8.4 µmol/L at 2 h. No result was above the reference range (50 µmol/L). No healthy subject with normal baseline ammonia would have been erroneously identified as having hyperammonaemia.

CONCLUSIONS

Results support MetBioNet guidance that laboratories accept blood samples for ammonia analysis which are not processed under ideal conditions.

Two pregnancies of an ornithine carbamoyltransferase deficiency disease carrier and review of the literature

BACKGROUND

the underlying cause of the deficiency of ornithine carbamoyltransferase (OTCD) is a gene mutation on the X chromosome. In females, the phenotype is highly variable, ranging from asymptomatic to neurologic compromise secondary to hyperammonemia and it can be prompted by numerous triggers, including pregnancy.

OBJECTIVE

the objective of this article is to report a case of two pregnancies of an OTCD-carrier, and to review the literature describing OTCD and pregnancy, parturition and postpartum.

METHODS

an extensive search in PubMed in December 2021 was conducted using different search terms. After screening all abstracts, 23 papers that corresponded to our inclusion criteria were identified.

RESULTS

the article focuses on the management of OTCD during pregnancy, parturition, and the postpartum period in terms of clinical presentation, ammonia levels and treatment.

CONCLUSIONS

females with OTCD can certainly plan a pregnancy, but they need a careful management during delivery and particularly during the immediate postpartum period. If possible, a multidisciplinary team of physicians, dietitians, obstetrician-gynecologist, neonatologists, pharmacists, etc. with expertise in this field should participate in the care of women with OTCD and their children during this period and in their adult life.

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.

Behind Protein Synthesis: Amino Acids-Metabokine Regulators of Both Systemic and Cellular Metabolism

Recent scientific research suggests that amino acids (AA) are not only the "building bricks" of protein synthesis but may also be considered "metabokines" [...].

Drug-induced hyperammonaemia

Hyperammonaemia (HA) as a consequence of numerous primary or secondary causes, gives rise to clinical manifestations due to its toxic effects on the brain. The neurological consequences broadly reflect the ammonia level, duration and age, with paediatric patients being more susceptible. Drug-induced HA may arise due to either decreased ammonia elimination or increased production. This is associated most frequently with use of valproate and presents a dilemma between ongoing therapeutic need, toxicity and the possibility of an alternative cause. As there is no specific test for drug-induced HA, prompt discussion with a metabolic physician is recommended, as the neurotoxic effects are time-dependent. Specific guidelines for managing drug-induced HA have yet to be published and hence the treatment approach outlined in this review reflects that outlined in relevant urea cycle disorder guidelines.

[Neonate-onset ornithine transcarbamylase deficiency]

The male neonate in this case study was admitted to the hospital at 15 hours of age due to respiratory distress for 15 hours and poor response for 3 hours after resuscitation from asphyxia. The neonate was highly unresponsive, with central respiratory failure and seizures. Serum ammonia was elevated (>1 000 μmol/L). Blood tandem mass spectrometry revealed a significant decrease in citrulline. Rapid familial whole genome sequencing revealed OTC gene mutations inherited from the mother. Continuous hemodialysis filtration and other treatments were given. Neurological assessment was performed by cranial magnetic resonance imaging and electroencephalogram. The neonate was diagnosed with ornithine transcarbamylase deficiency combined with brain injury. He died at 6 days of age after withdrawing care. This article focuses on the differential diagnosis of neonatal hyperammonemia and introduces the multidisciplinary management of inborn error of metabolism.

Ammonia and nutritional therapy in the critically ill: when to worry, when to test and how to treat?

PURPOSE OF REVIEW

Hyperammonaemia is almost always develops in patients with severe liver failure and this remains the commonest cause of elevated ammonia concentrations in the ICU. Nonhepatic hyperammonaemia in ICU presents diagnostic and management challenges for treating clinicians. Nutritional and metabolic factors play an important role in the cause and management of these complex disorders.

RECENT FINDINGS

Nonhepatic hyperammonaemia causes such as drugs, infection and inborn errors of metabolism may be unfamiliar to clinicians and risk being overlooked. Although cirrhotic patients may tolerate marked elevations in ammonia, other causes of acute severe hyperammonaemia may result in fatal cerebral oedema. Any coma of unclear cause should prompt urgent measurement of ammonia and severe elevations warrant immediate protective measures as well as treatments such as renal replacement therapy to avoid life-threatening neurological injury.

SUMMARY

The current review explores important clinical considerations, the approach to testing and key treatment principles that may prevent progressive neurological damage and improve outcomes for patients with hyperammonaemia, especially from nonhepatic causes.

Maternal-fetal outcomes of pregnancies in women treated at an inborn errors of metabolism unit

INTRODUCTION

Intermediate Inborn Errors of Metabolism (IEM) are a group of inherited diseases that include phenylketonuria (PKU), tyrosinemia II (TSII), organic acidaemias and ornithine transcarbamylase deficiency (OTCD), among others. They are increasingly more common in adults due to improved management. This has allowed more affected women to consider having children with good prospects. However, pregnancy may worsen metabolic control and/or increase maternal-fetal complications. The objective is to analyse the characteristics and outcomes of pregnancies of our patients with IEM.

METHODS

Retrospective descriptive study. Pregnancies of women with IEM attended to at the adult IEM referral unit of the Hospital Universitario Virgen del Rocío were included. The qualitative variables were described as n(%) and the quantitative as P50 (P25-P75).

RESULTS

24 pregnancies were recorded: 12 newborns were healthy, 1 inherited their mother's disease, 2 had maternal phenylketonuria syndrome, 1 was stillborn (gestational week 31 + 5), 5 were spontaneous abortions and 3 were voluntarily terminated. The gestations were divided into metabolically controlled and uncontrolled.

CONCLUSIONS

Pregnancy planning and multidisciplinary management through to postpartum is essential to ensure maternal and fetal health. The basis of treatment in PKU and TSII is a strict protein-limited diet. Events that increase protein catabolism in organic acidaemias and DOTC should be avoided. Further investigation of pregnancy outcomes in women with IEM is needed.