Reye's syndrome and aspirin: a review

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.

Orthodontics in patients with significant medical co-morbidities

A wide variety of patients with medical co-morbidities may present to general orthodontic practice. It is important for the treating clinician to have a general understanding of key medical conditions that may impact upon the treatment and management options. This clinical supplement provides a treatment-focused summative update for the orthodontist regarding significant medical co-morbidities, their general prevalence and an exploration of potential impacts upon orthodontic treatment. This review also discusses the significance of key medications and provides suggestions for the safe provision of orthodontic treatment.

Acute hepatitis and acute liver failure: Pathologic diagnosis and differential diagnosis

Acute hepatitis and acute liver failure are severe medical conditions that require early clinical intervention. Histopathologic findings on a liver biopsy or a liver explant may help identify the underlying etiology or provide an important direction for further clinical, laboratory and radiographical investigation. This review is divided into two main portions. The first portion concentrates on various etiologies and discusses unique histologic features that can be associated with specific etiologies. The second portion describes the general morphologic features based on which the diagnosis of acute hepatitis and acute liver failure are made. Histopathologic distinction between collapse and cirrhosis and limitations of histopathologic assessment for underlying etiologies are addressed in this portion. Another focus of this review is non-necrotic acute liver failure, which typically features diffuse microvesicular steatosis secondary to various etiologies causing mitochondrial dysfunction. Molecular testing serves an increasingly important role in the diagnosis and management of this group of disorders.

Ammonia metabolism and hyperammonemic disorders

Human adults produce around 1000 mmol of ammonia daily. Some is reutilized in biosynthesis. The remainder is waste and neurotoxic. Eventually most is excreted in urine as urea, together with ammonia used as a buffer. In extrahepatic tissues, ammonia is incorporated into nontoxic glutamine and released into blood. Large amounts are metabolized by the kidneys and small intestine. In the intestine, this yields ammonia, which is sequestered in portal blood and transported to the liver for ureagenesis, and citrulline, which is converted to arginine by the kidneys. The amazing developments in NMR imaging and spectroscopy and molecular biology have confirmed concepts derived from early studies in animals and cell cultures. The processes involved are exquisitely tuned. When they are faulty, ammonia accumulates. Severe acute hyperammonemia causes a rapidly progressive, often fatal, encephalopathy with brain edema. Chronic milder hyperammonemia causes a neuropsychiatric illness. Survivors of severe neonatal hyperammonemia have structural brain damage. Proposed explanations for brain edema are an increase in astrocyte osmolality, generally attributed to glutamine accumulation, and cytotoxic oxidative/nitrosative damage. However, ammonia neurotoxicity is multifactorial, with disturbances also in neurotransmitters, energy production, anaplerosis, cerebral blood flow, potassium, and sodium. Around 90% of hyperammonemic patients have liver disease. Inherited defects are rare. They are being recognized increasingly in adults. Deficiencies of urea cycle enzymes, citrin, and pyruvate carboxylase demonstrate the roles of isolated pathways in ammonia metabolism. Phenylbutyrate is used routinely to treat inherited urea cycle disorders, and its use for hepatic encephalopathy is under investigation.

Electron attachment to antipyretics: possible implications of their metabolic pathways

The empty-level structures and formation of negative ion states via resonance attachment of low-energy (0-15 eV) electrons into vacant molecular orbitals in a series of non-steroidal anti-inflammatory drugs (NSAIDs), namely aspirin, paracetamol, phenacetin, and ibuprofen, were investigated in vacuo by electron transmission and dissociative electron attachment (DEA) spectroscopies, with the aim to model the behavior of these antipyretic agents under reductive conditions in vivo. The experimental findings are interpreted with the support of density functional theory calculations. The negative and neutral fragments formed by DEA in the gas phase display similarities with the main metabolites of these commonly used NSAIDs generated in vivo by the action of cytochrome P450 enzymes, as well as with several known active agents. It is concluded that xenobiotic molecules which possess pronounced electron-accepting properties could in principle follow metabolic pathways which parallel the gas-phase dissociative decay channels observed in the DEA spectra at incident electron energies below 1 eV. Unwanted side effects as, e.g., hepatoxicity or carcinogenicity produced by the NSAIDs under study in human organism are discussed within the "free radical model" framework, reported earlier to describe the toxic action of the well-known model toxicant carbon tetrachloride.

Medicine use from birth to age two years: the 2004 Pelotas (Brazil) Birth Cohort study

OBJECTIVE

To describe medicine use by children at three, 12 and 24 months of age.

METHODS

Cross-sectional study using data from the 2004 Pelotas Birth Cohort (Southern Brazil), including: 3,985 children at three months, 3,907 children at 12 months, and 3,868 children at 24 months of age. The outcome investigated was use of medicine in the 15 days preceding the interview. Information on independent variables (medicine used, who indicated it, how it was obtained, periodicity of use, and therapeutic group) were collected using a standardized questionnaire administered during a home interview with the child's parents.

RESULTS

Prevalence of medicine use at three, 12, and 24 months was 65.0% (95% CI: 63.5;66.5), 64.4% (95% CI: 62.9;65.9), and 54.7% (95% CI: 53.1;56.2), respectively. As age increased, there was a reduction in the total number of medicines used and an increase in self-medicine, which reached 34% at 24 months. Furthermore, frequency of sporadic medicine use increased, while that of continuous use decreased. Medicine was purchased mainly using private resources, with roughly 10% of drugs being purchased through the Brazilian National Health Care System. The profile of medicine types used also changed with age. The type of medicine most frequently used were dermatological products (36%) at three months; respiratory system drugs (24%) at 12 months; and analgesics (26%) at 24 months of age. Compared to three months, medicine use at 24 months was characterized by decreased use of digestive tract and metabolism drugs, drugs for the sensory organs, cardiovascular system drugs, and dermatological products, and an increase in systemic anti-infectious drugs, medicine for the skeletomuscular and respiratory systems, analgesics, insecticides, and repellents.

CONCLUSIONS

Medicine use in this cohort was high and indicates the need for prioritizing rational use of medicine in early life.

Prognostic factors in influenza-associated encephalopathy

BACKGROUND

Recently, reports of influenza-associated encephalopathy have increased worldwide. Given the high mortality and morbidity rates attributable to this severe neurologic complication of influenza, we conducted a nationwide study in Japan to identify the prognostic factors.

METHODS

We retrospectively evaluated 442 cases of influenza-associated encephalopathy that were reported to the Collaborative Study Group on Influenza-Associated Encephalopathy, which was organized by the Japanese Ministry of Health, Labor, and Welfare in collaboration with hospitals, clinics, and local pediatric practices in Japan between 1998 and 2002. The outcome for each patient was classified as either survival or death. Predictors of death were identified using logistic regression analysis.

RESULTS

Four major prognostic factors for death were found to be significant by multivariate analysis (P < 0.05) in the 184 patients for whom we had complete data: elevation of aspartate aminotransferase, hyperglycemia, the presence of hematuria or proteinuria, and use of diclofenac sodium.

CONCLUSIONS

We identified patients who had factors associated with a poor prognosis, and these findings might be clinically useful for the management of this illness.

Drug metabolite profiling and elucidation of drug-induced hepatotoxicity

Drug metabolism studies, together with pathologic and histologic evaluation, provide critical data sets to help understand mechanisms underlying drug-related hepatotoxicity. A common practice is to trace morphologic changes resulting from liver injury back to perturbation of biochemical processes and to identify drug metabolites that affect those processes as possible culprits. This strategy can be illustrated in efforts of elucidating the cause of acetaminophen-, troglitazone- and valproic acid-induced hepatic necrosis, microvesicular steatosis and cholestasis with the aid of information from qualitative and quantitative analysis of metabolites. From a pharmaceutical research perspective, metabolite profiling represents an important function because a structure-activity relationship is essential to rational drug design. In addition, drugs are known to induce idiosyncratic hepatotoxicity, which usually escapes the detection by preclinical safety assessment and clinical trials. This issue is addressed, at present, by eliminating those molecules that are prone to metabolic bioactivation, based on the concept that formation of electrophilic metabolites triggers covalent protein modification and subsequent organ toxicity. Although pragmatic, such an approach has its limitations as a linear correlation does not exist between toxicity and the extent of bioactivation. It may be possible in the future that the advance of proteomics, metabonomics and genomics would pave the way leading to personalized medication in which beneficial effect of a drug is maximized, whereas toxicity risk is minimized.

Aspirin and Reye syndrome: a review of the evidence

Reye syndrome is an extremely rare but severe and often fatal disease. Death occurs in about 30-40% of cases from brainstem dysfunction. The disease typically is preceded by a viral infection with an intermediate disease-free interval of 3-5 days. The biochemical explanation for Reye-like symptoms is a generalized disturbance in mitochondrial metabolism, eventually resulting in metabolic failure in the liver and other tissues. The etiology of 'classical' Reye syndrome is unknown. Hypothetically, the syndrome may result from an unusual response to the preceding viral infection, which is determined by host genetic factors but can be modified by a variety of exogenous agents. Thus, several infections and diseases might present clinically with Reye-like symptoms. Exogenous agents involve a number of toxins, drugs (including aspirin [acetylsalicylic acid]), and other chemicals. The 'rise and fall' in the incidence of Reye syndrome is still poorly understood and unexplained. With a few exceptions, there were probably no new Reye-like diseases reported during the last 10 years that could not be explained by an inherited disorder of metabolism or a misdiagnosis. This may reflect scientific progress in the better understanding of cellular and molecular dysfunctions as disease-determining factors. Alternatively, the immune response to and the virulence of a virus might have changed by alteration of its genetic code. The suggestion of a defined cause-effect relationship between aspirin intake and Reye syndrome in children is not supported by sufficient facts. Clearly, no drug treatment is without side effects. Thus, a balanced view of whether treatment with a certain drug is justified in terms of the benefit/risk ratio is always necessary. Aspirin is no exception.

Inhibition of mitochondrial beta-oxidation as a mechanism of hepatotoxicity

Severe and prolonged impairment of mitochondrial beta-oxidation leads to microvesicular steatosis, and, in severe forms, to liver failure, coma and death. Impairment of mitochondrial beta-oxidation may be either genetic or acquired, and different causes may add their effects to inhibit beta-oxidation severely and trigger the syndrome. Drugs and some endogenous compounds can sequester coenzyme A and/or inhibit mitochondrial beta-oxidation enzymes (aspirin, valproic acid, tetracyclines, several 2-arylpropionate anti-inflammatory drugs, amineptine and tianeptine); they may inhibit both mitochondrial beta-oxidation and oxidative phosphorylation (endogenous bile acids, amiodarone, perhexiline and diethylaminoethoxyhexestrol), or they may impair mitochondrial DNA transcription (interferon-alpha), or decrease mitochondrial DNA replication (dideoxynucleoside analogues), while other compounds (ethanol, female sex hormones) act through a combination of different mechanisms. Any investigational molecule should be screened for such effects.

Reye syndrome or side-effects of anti-emetics?

By analysing two patients initially diagnosed as Reye syndrome evidence is given that in some patients considered as having Reye syndrome, the syndrome is an escalation of symptoms due to viral disease and to unrecognized drug-induced encephalopathy, mainly by anti-emetics. A detailed drug history, considering all medication--not exclusively aspirin--taken during the full course of the illness is essential to differentiate between Reye syndrome and drug-induced symptoms. In addition, a critical analysis is presented of the four main case-control surveys that have lead to the proposal that salicylates are primary causative agents of Reye syndrome. In these surveys, medications given during the prodromal illness were adequately recorded, but other drugs given after the onset of vomiting have been overlooked or deliberately excluded. New epidemiological studies are needed, recording all drugs given to the patients throughout the full course of their illness until the moment of admission, in order to elucidate the mystery of Reye syndrome.

Interrelationships of liver and brain with special reference to Reye syndrome

Reye syndrome is an acute non-inflammatory encephalopathy that can be precipitated by toxic, infective, metabolic or hypoxic upsets. The biochemical changes point to mitochondrial dysfunction and this is substantiated by structural changes in mitochondria on electron microscopy. The toxic metabolites that accumulate are similar to those incriminated in hepatic encephalopathy and other metabolic diseases. These metabolites exert their deleterious effects by direct neuronal damage, neurotransmitter blockade, vascular damage, cerebral oedema, hypoxic ischaemic damage, demyelination, retardation of brain growth and neuronal storage. Brain capillary endothelial cells are very rich in mitochondria and mitochondrial disorders can effect the central nervous system primarily, and not just as a consequence of systemic metabolic upset.

Aspirin and Reye's syndrome--do parents know?

Amid growing concern over the association between aspirin and Reye's syndrome, the Aspirin Foundation has recently mounted a publicity campaign advising against the use of aspirin in children. Of 50 parents questioned at a children's ward of a district general hospital, 46 (92%) had heard of the publicity, 38 via the television. The number of parents who would give aspirin to their child had dropped significantly from 45 before the campaign to five after it (P<0.001); only one parent chose to ignore the advice. The media, particularly television, is again shown to be a potent means of publicity. Despite the very high response to the advice about aspirin none of the parents mentioned Reye's syndrome as the reason.