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PubMed1993

Transient hyperammonemia related to chemotherapy with continuous infusion of high-dose 5-fluorouracil.

Hyperammonemic encephalopathy has been reported in patients receiving chemotherapy (CT). It is characterized by abrupt alteration in mental status with markedly elevated plasma ammonium levels in the absence of obvious liver disease. This paper reports seven patients who developed transient hyperammonemia during chemotherapy. The regimens all included continuous infusion of high-dose 5-fluorouracil (5-FU). The onset of hyperammonemic encephalopathy was 1.5-4 days after the start of CT. Five cases had infection and six had prerenal azotemia at the time of hyperammonemia. After management, plasma ammonium levels all returned to the normal range within 2 days. Except for one persistent coma, status of consciousness cleared completely. The true mechanism of transient hyperammonemia is unclear. The excess production of ammonium due to metabolites of 5-FU added to precipitating factors such as infection, hypovolemia or constipation may be the explanation for transient hyperammonemia in our study.

Adult↗
PubMed1991

Guanidino compound metabolism in arginine-free diet induced hyperammonemia.

Guanidino compounds, intermediates of arginine metabolism, are altered in many pathological conditions especially those involving the urea cycle. Arginine and creatine play an important role in nitrogen metabolism whereas other guanidino compounds such as guanidinosuccinic acid and N-acetylarginine are toxins. Our objective was to investigate the relationship between guanidino compounds and hyperammonemia. Young and adult ferrets were fed a single meal of either an arginine-containing diet (ACD) or an arginine-free diet (AFD). Guanidino compounds were determined by HPLC in the plasma, liver, kidney and brain 3 h after feeding the specified diet. Only young ferrets fed AFD developed hyperammonemia. Plasma and kidney arginine was decreased whereas guanidinosuccinic acid was increased in young ferrets fed AFD. Hepatic creatine and kidney and brain guanidinoacetic acid were significantly decreased in this group. These results indicate that AFD-induced hyperammonemia produced decreased methylation activity in the liver and transamidination activity in kidney. Elevated guanidinosuccinate levels coupled with deficient hepatic creatine synthesis may play a role in the pathophysiology of hyperammonemia.

Ammonia↗
PubMedDate not supplied

Hyperammonemia during total parenteral nutrition in children.

Serial blood ammonia (NH3) determinations in 19 low birth weight (LBW) infants, 14 term neonates and 12 children receiving total parenteral nutrition (TPN) have shown that 73% of patients had one or more elevated NH3 values (greater than 150 micrograms/dl). The mean blood NH3 was 220 +/- 13 micrograms/dl in LBW infants, 180 +/- 9 micrograms/dl in 10 infants, and 140 +/- 7 micrograms/dl in children. All of these values are significantly higher than normal (p less than 0.001). There was no difference in incidence or mean blood ammonia concentration between patients receiving casein hydrolysate and those receiving a crystalline amino acid solution. Only four patients were symptomatic and several infants remained fully alert despite blood NH3 concentration in excess of 400 micrograms/dl. One infant who had sustained hyperammonemia was given another amino acid source (Travasol) containing 1.2 mmol/dl of arginine; blood NH3 promptly fell to the normal range. However, six of seven additional infants had hyperammonemia while receiving Travasol (mean = 184 micrograms/dl). Hyperammonemia is common during TPN in children, often is not recognized clinically, and occurs with equal frequency in infants and older children. The high levels observed in LBW infants may be due to hepatic immaturity. Blood NH3 concentration should be monitored frequently during TPN. Persistent hyperammonemia should be treated by decreasing protein content of the infusate. The role of supplemental arginine is unclear.

Adolescent↗
PubMed1992

Quinolinate in brain and cerebrospinal fluid in rat models of congenital hyperammonemia.

Children with inborn errors of urea synthesis who survive neonatal hyperammonemic coma commonly exhibit cognitive deficits and neurologic abnormalities. Yet, there is evidence that ammonia is not the only neurotoxin. Hyperammonemia appears to induce a number of neurochemical alterations. In rodent models of hyperammonemia, uptake of L-tryptophan into brain is increased. It has been reported that in an experimental rat model of hepatic encephalopathy, in the ammonium acetate-injected rat, and in patients with hepatic failure and inborn errors of ammonia metabolism, quinolinate, a tryptophan metabolite, is increased. Elevations in quinolinate are of particular concern, as quinolinate could excessively activate the N-methyl-D-aspartate subclass of excitatory amino acid receptors, thereby causing selective neuronal necrosis. We sought to identify an animal model that would replicate the increases in quinolinate that have been associated with hyperammonemia in humans. Levels of quinolinate were measured in hyperammonemic urease-infused rats and ammonium acetate-injected rats. In the urease-infused rat, brain tryptophan was doubled, and serotonin and its metabolite 5-hydroxyindoleacetic acid were significantly increased. Yet, despite the increase in tryptophan and evidence for increased metabolism of tryptophan to serotonin, there were no observed increases of quinolinate in brain, cerebrospinal fluid, or plasma. In the ammonium acetate-injected rat, significant increases of 5-hydroxyindoleacetic acid in cerebral cortex were also observed, but quinolinate did not change in cerebrospinal fluid or cerebral cortex. In summary, we were unable to demonstrate an increase of quinolinate in brain or cerebrospinal fluid in these rat models of hyperammonemia.

Acetates↗
PubMed1981

Valproic acid and secondary hyperammonemia.

An 11-year-old girl with complex seizures was started on valproic acid (VPA) in addition to clonazepam and ethosuximide. Shortly thereafter, she developed marked hyperammonemia that was worsened by a protein load. The hyperammonemia improved somewhat when protein was not given, and it resolved on discontinuation of the valproic acid. No associated changes in serum transaminases or bilirubin were observed. Isolated hyperammonemia may occur soon after VPA ingestion and appears to be a relatively infrequent, reversible side effect. The mechanism of hyperammonemia probably differs from other manifestations of hepatotoxicity, such as elevated transaminases or frank hepatic failure.

Ammonia↗
PubMed1984

Valproic acid-induced hyperammonemia in mentally retarded adults.

All individuals receiving valproic acid therapy in an institution for the mentally retarded were evaluated for hyperammonemia. Of these 19 adults, 6 had persistent and 5 others had intermittent hyperammonemia. The hyperammonemic patients were asymptomatic, except that 2 had occasional lethargy. Hyperammonemia was detected more often in younger adults and in those treated with multiple anticonvulsants, especially phenytoin. Valproate-induced hyperammonemia is probably the result of depletion of mitochondrial acetyl CoA and decreased production of N-acetylglutamate, the obligatory activator of the first enzyme of the urea cycle, carbamyl phosphate synthetase I. Anticonvulsant-mediated microsomal enzyme induction may also contribute.

Adolescent↗
PubMed1994

Unexpected encephalopathy in chronic renal failure: hyperammonemia complicating acute peritonitis.

A woman with mild chronic renal insufficiency was being treated with glucocorticoids for a presumed chronic inflammatory disease. She developed peritonitis arising from a pelvic abscess, which was drained without complications. Unexpectedly, she became obtunded, and eventually, the neurologic dysfunction was linked to hyperammonemia in spite of normal liver function tests. Hyperammonemia was only transiently controlled in spite of protein restriction, repeated hemodialysis, and the use of biochemical means to reduce ammonia. A recurrent pelvic abscess was drained, and hyperammonemia disappeared. A review of ammonia and nitrogen metabolism indicates that bypassing the liver with shunting of ammonia into the systemic circulation should be added to the causes of symptomatic hyperammonemia. Treatment requires the elimination of the bacteria.

Abscess↗
PubMed1997

Hepatic glutamine synthetase deficiency in fatal hyperammonemia after lung transplantation.

BACKGROUND: The cause of severe acquired hyperammonemia, an uncommon but often fatal complication of organ transplantation and chemotherapy for cancer, is obscure. OBJECTIVE: To test the hypothesis that liver glutamine synthetase deficiency may explain hyperammonemia in patients who have had organ transplantation or are receiving chemotherapy. DESIGN: Case report. PATIENTS: Two patients who had fatal hyperammonemia after orthotopic lung transplantation. MEASUREMENTS: Liver tissue was analyzed to determine the activities of two urea cycle enzymes and glutamine synthetase. Western blot assays for hepatic glutamine synthetase were performed to determine whether glutamine synthetase deficiency resulted from reduced enzyme levels. RESULTS: Activities of carbamoyl phosphate synthetase I and ornithine carbamoyltransferase in the liver were normal. The activity of hepatic glutamine synthetase was markedly reduced (in patient 1, 12% of the mean value in controls; in patient 2, 28% of the mean value in controls), and a concomitant reduction in the amount of glutamine synthetase protein was observed. CONCLUSION: Hyperammonemia after transplantation was associated with hepatic glutamine synthetase deficiency in two patients, but the causal relation between these two conditions must be further studied.

Ammonia↗
PubMedDate not supplied

[Hyperammonemia during hypothyroidism: an unusual biohumoral finding normalized by hormonal replacement treatment].

In this paper we describe 3 clinical cases of hypothyroidism causing myopathy and hyperammonemia. The patients, all females, aged 32 to 64 years, presented with hoarseness, fatigue, dyspepsia (case I), difficulty speaking secondary to the sensation of tongue swelling and hoarseness (case II), and progressive weight gain and difficulty speaking secondary to tongue swelling after delivery (case III). Laboratory tests showed a marked increase in creatine phosphokinase (up to 4090 U/L; normal values 24-176 U/L) of muscle origin, and an increase in transaminases and ammonia (124 to 150 micrograms/dL; normal values up to 75 micrograms/dL). Hypothyroidism was confirmed by TSH > 100 microIU/mL (normal values 0.3-5 microIU/mL). Treatment only with L-thyroxine determined the complete and persistent recovery of well-being and of biochemical abnormalities. The patients remained in good health after more than 2 years of follow-up. Our finding of hyperammonemia caused by the lack of thyroid hormones in 3 patients with hypothyroid myopathy appears to be of a certain interest as, to our knowledge, this phenomenon has not been previously described. In conclusion our hypothesis is that increased muscle production of ammonia secondary to the hypothyroid myopathy determined an increased ammonia load, resulting in hyperammonemia. Decreased liver ureagenesis induced by the lack of thyroid hormones also contributed to the hyperammonemia.

Adult↗
PubMed1975

Studies on the pathophysiology of encephalopathy in Reye's syndrome; Hyperammonemia in Reye's syndrome.

The initial acid-base status of eight survivors of Reye's syndrome was characterized by acute respiratory alkalosis (Pco2=32 mm Hg; Hco3-=22.0 mEq/liter) while that of eight children who died was associated with metabolic acidosis as well (HCO3-=10.0 mEg/liter). Arterial-internal jugular venous ammonia concentration differences on day 1 (299 mg/100 ml) and day 2 (90 mg/100 ml) reflected cerebral uptake of ammonia while those on days 3 and 4 (-43 and -55 mg/100 ml) demonstrated cerebral release. Arterial blood hyperammonemia can be detoxified safely in the brain as long as the levels do not exceed approximately 300mug/100 ml. Beyond that level lactic acidosis is observed, particularly in cerebral venous drainage. Arterial blood hyperammonemia was also related to the extent of alveolar hyperventilation. These findings are very similar to those seen in experimental hyperammonemia and support the concept that neurotoxicity in children with Reye's syndrome is at least partly due to impaired oxidative metabolism secondary to hyperammonemia.

Acid-Base Imbalance↗
PubMed1979

[Changes in cephalic and peripheral use of glucose and glutamine under the influence of hyperammonemia in rats].

Arterio-venous differences of glucose and glutamine were determined across the brain and across the hind limb in normal and ammonium salt infused rats, before and during an insulin tolerance test, in an attempt to study the effect of hyperammonemia on cephalic and muscular metabolism. The results demonstrate that 1) hyperammonemia reduces the hind limb uptake of glucose without affect the cephalic uptake of glucose which is lowered during hypoglycemia, 2) the reduction of the cephalic and muscular glutamine output induced by the hypoglycemia is masked in presence of an hyperammonemia. In conclusion, it may be assume that, at the concentration obtained in this study, hyperammonemia does not act directly in the pathogenesis of hepatic coma in which a decrease in cerebral glucose uptake described; on the other hand, ammonium plays an important role in the muscle metabolism.

Ammonia↗
PubMed1985

Arginine deficiency, hyperammonemia and Reye's syndrome in ferrets.

Young male ferrets developed hyperammonemia and encephalopathy shortly after eating a diet lacking in arginine. The dietary supplementation of arginine or intraperitoneal injection of ornithine prevented hyperammonemia and shortened the duration of encephalopathy. Therefore, young ferrets were assumed to be unable to meet their ornithine needs from sources other than arginine. Adult ferrets did not develop hyperammonemia and encephalopathy after eating arginine-free diet. Because young ferrets are also susceptible to human influenza infections, they were further tested as animal model of Reye's syndrome. Reye's syndrome is a serious childhood disorder that develops following influenza infections and is characterized in part by an encephalopathy, hyperammonemia and elevated serum transaminases. In young ferrets, concurrent administration of aspirin with human influenza inoculation and an arginine-free diet produced symptoms similar to those seen in humans with Reye's syndrome. The ferret model appears to be useful for studying the roles of various etiologic agents and their interactions in producing Reye's syndrome-like disorders. The ammonia metabolism in ferrets is reviewed and the ferret model for Reye's syndrome and its applications for the better understanding of this disorder in humans are discussed.

Ammonia↗
PubMed1986

[Hyperammonemia in valproate therapy in children and adolescents].

In order to evaluate significance and frequency of valproic acid (VPA)-induced hyperammonemia we measured venous serum ammonia, SGOT, G-GT, platelets and antiepileptic drug levels in three groups of subjects: 1.) 30 pediatric patients treated with VPA, alone or in combination 2.) 30 healthy age and sex matched subjects 3.) 30 pediatric unselected patients treated with various antiepileptic drugs except VPA. In the VPA group serum ammonia was significantly (p less than 0.01) higher than in controls and in the group 3. Patients on VPA-polytherapy had significantly higher serum ammonia values than patients on VPA-monotherapy (p less than 0.01). Hyperammonemia was found in 8 (27%) VPA-treated patients. A syndrome consisting of lethargy, stupor, hypotonia and increased seizure activity developed in 3 patients on VPA-therapy of whom two showed hyperammonemia. After discontinuing VPA this syndrome disappeared in all three cases. There was no direct correlation between VPA and ammonia levels. The etiology of hyperammonemia in VPA treated patients is not yet fully explained. It may be related to the fatal VPA induced hepatic failure reported in the literature. Some risk factors which may facilitate hepatic injury during VPA therapy (young age, co-medication, polytherapy, infectious disease, protein overload, low caloric intake) are discussed and some practical consequences are indicated.

Adolescent↗
PubMed1987

The hyperornithinemia, hyperammonemia, homocitrullinuria syndrome: an ornithine transport defect remediable with ornithine supplements.

The primary defect in patients presenting with a history of protein intolerance, mental retardation, and epilepsy of variable degree, with the unique triad of hyperornithinemia, hyperammonemia, and homocitrullinuria (the HHH syndrome) has been postulated to be a defect in translocation of ornithine into the mitochondria. In a 12-year-old boy with the HHH syndrome, the hyperammonemia observed following a protein load was prevented when the same load was given orally with a 1 mmol/kg of ornithine-HCl. At a dosage level of 0.5 to 1.0 mmol/kg/day of ornithine HCl, administered in 3 divided doses with meals, the patient's protein tolerance improved. As pretreatment hyperammonemia reverted to normal levels, the patient was able to cope with increased dietary protein and his growth accelerated. During the 2-year interval of the study, the ornithine HCl supplements were withdrawn on 2 occasions, and within a week the hyperammonemia recurred. Whereas cultured fibroblasts from the HHH patient were capable of oxidizing U-14C-glutamate to 14CO2 as rapidly as normal cells. 1-14C-ornithine or 5-14C-ornithine were oxidized at only 1/28 or 1/49 of the normal rate. Ultrastructural studies of the HHH cultured fibroblast mitochondria revealed distinctive alterations in size and shape; unusually long, branching, and "curling," HHH mitochondria also showed accelerated regressive changes.

Amino Acid Metabolism, Inborn Errors↗
PubMed1979

Hyperammonemia following ureterocolostomy in the rat.

Following ureterosigmoidostomy, encephalopathy with hyperammonemia may occur in the presence of cirrhosis, and the same complication was also observed in a few patients without liver damage. This suggests overloading of normal liver ureagenisis by an increased portal ammonia supply. To test this hypothesis and to try to produce an experimental model of chronic hyperammonemia without portal or hepatic damage, ureterocolostomies were performed in rats. These rats were compared with sham operated upon rats and with rats having chronic uremia induced by subtotal nephrectomy. Rats having a ureterocolostomy had chronic, but moderate, systemic hyperammonemia without any histologic hepatic damage and without gross behavioral modifications and slight uremia with only inconstant pyelonephretic lesions. In these rats, hyperammonemia results from hepatic overloading by the increased portal ammonia supply which is a consequence of both intestinal absorption of some urinary ammonia and increased intestinal ammoniagenesis induced by hydrolysis of urinary and circulating urea.

Ammonia↗
PubMed1984

Hyperammonemia in lysinuric protein intolerance.

Two brothers with hyperdibasicaminoaciduria and postprandial hyperammonemia showed characteristics of lysinuric protein intolerance. Intravenous alanine load produced hyperammonemia that was aborted by oral supplementation with arginine in one brother but not in the other, although both patients had almost the same intestinal malabsorption of arginine. This occurrence suggests that even a small amount of arginine, when absorbed into the blood, can normalize the affected ammonia metabolism of lysinuric protein intolerance. Two patients with cystinuria developed marked hyperammonemia when they received an intravenous alanine load after a 19-hour fast. As both patients displayed a reduced plasma concentration of arginine and ornithine at this time, the hyperammonemia was assumed to arise from the low plasma amino acid level. It seems likely that a decrease in plasma levels of urea cycle substrate causes a failure of the tissue urea cycle metabolism. Thus the impaired ammonia metabolism in lysinuric protein intolerance would be attributed to the low plasma arginine and ornithine levels.

Adolescent↗
PubMed1998

[Clinicopathological study of multiple myeloma associated with hyperammonemia].

Of 5 multiple myeloma patients with hyperammonemia, autopsy was performed in 4 patients, while amino acid metabolism was examined in 3 patients. As a result they were classified into the following 3 types; A, liver dysfunction and severe liver infiltration of myeloma cells. B, severe liver infiltration without liver dysfunction. C, Neither liver dysfunction nor severe liver infiltration. In one type A patient, isoleucine decreased. In two patients without liver dysfunction (one type C patient and another patient in whom autopsy was not performed) valine, leucine and isoleucine decreased, and tyrosine decreased slightly. The Fischer ratio decreased in these 2 patients, while it decreased slightly in a type A patient. Clinically, in 4 patients hyperammonemia was observed during periods of poor general condition and when refractory to chemotherapy. In an aggressive type case, consciousness disturbance was developed rapidly and multiple myeloma was diagnosed. In all patients, consciousness disturbance was noted. Hyperammonemia might have been caused by hepatic failure or systemic-portal shunt in patients with liver infiltration. In those without liver infiltration, it was suggested that hyperammonemia was caused by myeloma related humoral factors that influence amino acid metabolism.

Aged↗
PubMed2004

Large pulmonary arteriovenous malformation with hyperammonemia.

A 45-year-old female presented with generalized fatigue, unaccompanied by other symptoms. Investigation revealed severe anemia due to gastric bleeding, and hereditary hemorrhagic telangiectasia accompanied by a large pulmonary arteriovenous malformation (PAVM). Additionally, the presence of hepatic arteriovenous and portovenous shunts indicated hepatic involvement. In addition to hypoxemia due to right-to-left shunting in PAVM, hyperammonemia with normal hepatic function was detected. The large PAVM was successfully managed with surgical resection. Hyperammonemia, persisting despite the hemostasis of gastric bleeding, improved postoperatively in the absence of treatment directed at hepatic involvement. We believe that resection of large PAVM contributed to the improvement of hyperammonemia.

Arteriovenous Malformations↗