Biochemical correlates of illness and recovery in Reye's syndrome

Safety and Efficacy of Tranexamic Acid in Aneurysmal Subarachnoid Hemorrhage: A Meta-Analysis of Randomized Controlled Trials

Background

In recent decades, tranexamic acid (TXA) antifibrinolytic therapy before aneurysm clipping or embolization has been widely reported, but its safety and efficacy remain controversial. This meta-analysis evaluated the efficacy and safety of TXA therapy in aneurysmal subarachnoid hemorrhage (aSAH) patients, aiming to improve the evidence-based medical knowledge of treatment options for such patients.

Methods

Pubmed, Web of Science, and Cochrane Library databases were searched up to 1 March 2021 for randomized controlled trials (RCTs). We extracted safety and efficacy outcomes and performed a meta-analysis using the Review Manager software. We performed two group analyses of TXA duration and daily dose.

Results

Ten RCT studies, enrolling a total of 2,810 participants (1,410 with and 1,400 without TXA therapy), matched the selection criteria. In the TXA duration group: TXA did not reduce overall mortality during the follow-up period [RR 1.00 (95% CI 0.81–1.22)]. The overall rebleeding rate in the TXA group was 0.53 times that of the control group, which was statistically significant [RR 0.53 (95% CI 0.39–0.71)]. However, an RR of 0.43 was not statistically significant in the subgroup analysis of short-term therapy [RR 0.43 (95% CI 0.13–1.39)]. The overall incidence of hydrocephalus was significantly higher in the TXA group than in the control group [RR 1.13 (95% CI 1.02–1.24)]. However, the trend was not statistically significant in the subgroup analysis [short-term: RR 1.10 (95% CI 0.99–1.23); long-term: RR 1.22 (95% CI 0.99–1.50)]. Treatment with TXA did not cause significant delayed cerebral ischemia [RR 1.18 (95% CI 0.89–1.56)], and its subgroup analysis showed an opposite and insignificant effect [short-term: RR 0.99 (95% CI 0.79–1.25); long-term: RR 1.38 (95% CI 0.86–2.21)]. Results in the daily dose group were consistent with those in the TXA duration group.

Conclusions

Tranexamic acid does not reduce overall mortality in patients with aSAH, nor does it increase the incidence of delayed cerebral ischemia. Tranexamic acid in treating aSAH can reduce the incidence of rebleeding. However, there is no statisticalsignificance in the ultra-early short-term and low daily dose TXA therapy, which may be due to the lack of relevant studies, and more RCT experiments are needed for further study.

Systematic Review Registration:

https://www.crd.york.ac.uk/PROSPERO/display_record.asp? PROSPERO, identifier: 244079.

Transfusion strategies in bleeding critically ill adults: a clinical practice guideline from the European Society of Intensive Care Medicine

Purpose

To develop evidence-based clinical practice recommendations regarding transfusion practices and transfusion in bleeding critically ill adults.

Methods

A taskforce involving 15 international experts and 2 methodologists used the GRADE approach to guideline development. The taskforce addressed three main topics: transfusion support in massively and non-massively bleeding critically ill patients (transfusion ratios, blood products, and point of care testing) and the use of tranexamic acid. The panel developed and answered structured guideline questions using population, intervention, comparison, and outcomes (PICO) format.

Results

The taskforce generated 26 clinical practice recommendations (2 strong recommendations, 13 conditional recommendations, 11 no recommendation), and identified 10 PICOs with insufficient evidence to make a recommendation.

Conclusions

This clinical practice guideline provides evidence-based recommendations for the management of massively and non-massively bleeding critically ill adult patients and identifies areas where further research is needed.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00134-021-06531-x.

Tranexamic acid in non-traumatic intracranial bleeding: a systematic review and meta-analysis

Non-traumatic intracranial bleeding (NTIB), comprising subarachnoid hemorrhage (SAH) and intra-cranial bleeding (ICH) is a significant public health concern. Tranexamic acid (TXA) is a promising treatment with benefits yet to be fully demonstrated. We conducted a systematic review and meta-analysis on the impact of TXA on mortality in NTIB. We searched the PubMed, Cochrane Library, Google Scholar and ScienceDirect databases for studies reporting mortality data following the use of TXA in NTIB for comparisons with a control group. We computed random-effect meta-analysis on estimates of risk and sensitivity analyses. We computed meta-regression to examine the putative effects of the severity of NTIB, sociodemographic data (age, sex), and publication date. Among potentially 10,008 articles, we included 15 studies representing a total of 4883 patients: 2455 receiving TXA and 2428 controls; 1110 died (23%) during the follow-up. The meta-analysis demonstrated a potential of 22% decrease in mortality for patients treated by TXA (RR = 0.78, 95%CI 0.58-0.98, p = 0.002). Meta-regression did not demonstrate any influence of the severity of NTIB, age, sex, length of treatment or date of publication. Sensitivity analyses confirmed benefits of TXA on mortality. TXA appears to be a therapeutic option to reduce non-traumatic intracranial bleeding mortality, particularly in patients with SAH.

Mitochondrial dysfunction in fatty acid oxidation disorders: insights from human and animal studies

Patients affected by FAOD commonly present with hepatopathy, cardiomyopathy, skeletal myopathy and encephalopathy. Human and animal evidences indicate that mitochondrial functions are disrupted by fatty acids and derivatives accumulating in these disorders, suggesting that lipotoxicity may contribute to their pathogenesis.

Mitochondrial fatty acid oxidation (FAO) plays a pivotal role in maintaining body energy homoeostasis mainly during catabolic states. Oxidation of fatty acids requires approximately 25 proteins. Inherited defects of FAO have been identified in the majority of these proteins and constitute an important group of inborn errors of metabolism. Affected patients usually present with severe hepatopathy, cardiomyopathy and skeletal myopathy, whereas some patients may suffer acute and/or progressive encephalopathy whose pathogenesis is poorly known. In recent years growing evidence has emerged indicating that energy deficiency/disruption of mitochondrial homoeostasis is involved in the pathophysiology of some fatty acid oxidation defects (FAOD), although the exact underlying mechanisms are not yet established. Characteristic fatty acids and carnitine derivatives are found at high concentrations in these patients and more markedly during episodes of metabolic decompensation that are associated with worsening of clinical symptoms. Therefore, it is conceivable that these compounds may be toxic. We will briefly summarize the current knowledge obtained from patients and genetic mouse models with these disorders indicating that disruption of mitochondrial energy, redox and calcium homoeostasis is involved in the pathophysiology of the tissue damage in the more common FAOD, including medium-chain acyl-CoA dehydrogenase (MCAD), long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and very long-chain acyl-CoA dehydrogenase (VLCAD) deficiencies. We will also provide evidence that the fatty acids and derivatives that accumulate in these diseases disrupt mitochondrial homoeostasis. The elucidation of the toxic mechanisms of these compounds may offer new perspectives for potential novel adjuvant therapeutic strategies in selected disorders of this group.

Antifibrinolytic therapy in the management of aneurismal subarachnoid hemorrhage revisited. A meta-analysis

BACKGROUND

To reassess the use of antifibrinolytics (AF) in the management of aneurysmal subarachnoid hemorrhage (SAH) in the setting of present-day treatment strategies.

METHOD

The authors conducted a systematic review of the literature and a meta-analysis. They reviewed the PubMed database and conducted a manual review of article bibliographies.

RESULTS

Using a pre-specified search strategy, 17 relevant studies involving a total of 2,872 patients with SAH at baseline, from which data of 1,380 patients having received AF, were included in a meta-analysis. Pooled odds ratios of the impact of AF on functional outcomes, rebleeding, and cerebral infarction were calculated. Short-term use of AF (72 h or less) associated with medical prevention of ischemic deficit seems to yield better results on functional outcome than long-term use of AF, especially if not associated with a medical prevention of ischemic deficit. The risk of cerebral infarction is not increased by the short-term use of AF and the risk of rebleeding is decreased independently of the length of AF use.

CONCLUSIONS

The use of AF should be reconsidered in the setting of modern-era treatment strategies, as the short-term use associated with medical prevention of ischemic deficit decreases the rate of rebleeding and does not increase the risk of cerebral infarction, thus potentially yielding better protection against poor functional outcome.

Tranexamic acid: a review of its use in surgery and other indications

Tranexamic acid is a synthetic derivative of the amino acid lysine that exerts its antifibrinolytic effect through the reversible blockade of lysine binding sites on plasminogen molecules. Intravenously administered tranexamic acid (most commonly 10 mg/kg followed by infusion of 1 mg/kg/hour) caused reductions relative to placebo of 29 to 54% in postoperative blood losses in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB), with statistically significant reductions in transfusion requirements in some studies. Tranexamic acid had similar efficacy to aprotinin 2 x 10(6) kallikrein inhibitory units (KIU) and was superior to dipyridamole in the reduction of postoperative blood losses. Transfusion requirements were reduced significantly by 43% with tranexamic acid and by 60% with aprotinin in 1 study. Meta-analysis of 60 trials showed tranexamic acid and aprotinin, unlike epsilon-aminocaproic acid (EACA) and desmopressin, to reduce significantly the number of patients requiring allogeneic blood transfusions after cardiac surgery with CPB. Tranexamic acid was associated with reductions relative to placebo in mortality of 5 to 54% in patients with upper gastrointestinal bleeding. Meta-analysis indicated a reduction of 40%. Reductions of 34 to 57.9% versus placebo or control in mean menstrual blood loss occurred during tranexamic acid therapy in women with menorrhagia; the drug has also been used to good effect in placental bleeding, postpartum haemorrhage and conisation of the cervix. Tranexamic acid significantly reduced mean blood losses after oral surgery in patients with haemophilia and was effective as a mouthwash in dental patients receiving oral anticoagulants. Reductions in blood loss were also obtained with the use of the drug in patients undergoing orthotopic liver transplantation or transurethral prostatic surgery, and rates of rebleeding were reduced in patients with traumatic hyphaema. Clinical benefit has also been reported with tranexamic acid in patients with hereditary angioneurotic oedema. Tranexamic acid is well tolerated; nausea and diarrhoea are the most common adverse events. Increased risk of thrombosis with the drug has not been demonstrated in clinical trials.

CONCLUSIONS

Tranexamic acid is useful in a wide range of haemorrhagic conditions. The drug reduces postoperative blood losses and transfusion requirements in a number of types of surgery, with potential cost and tolerability advantages over aprotinin, and appears to reduce rates of mortality and urgent surgery in patients with upper gastrointestinal haemorrhage. Tranexamic acid reduces menstrual blood loss and is a possible alternative to surgery in menorrhagia, and has been used successfully to control bleeding in pregnancy.

Aspirin induces short-chain free fatty acid accumulation in rats

Aspirin is used for the prophylaxis of infarction. A low dose of aspirin is effective for the prophylaxis of myocardial infarction, whereas a higher dose is necessary for that of stroke. Salicylic acid, the in vivo metabolite of aspirin, inhibits the beta-oxidation of short-chain fatty acids. Accordingly, drinking water containing 400, 800, or 1200 mg/l aspirin was given to each of eight rats for 30 days to determine the serum short-chain fatty acid levels. Analysis of variance and a post-hoc Fisher's protected least significant differences test revealed significantly increased levels (P < 0.05) of monocarboxylic acids, n-hexanoate, n-octanoate, n-decanoate, n-dodecanoate, and dicarboxylic acids, adipate (C6,) and suberate (C8): 78.7 +/- 36.2, 61.1 +/- 30.6, 215 +/- 151, 47.5 +/- 24.0, 3.64 +/- 2.09 and 1.71 +/- 1.45 micromol/l in the 800 mg/l aspirin group compared to 23.8 +/- 12.3, 20.1 +/- 9.0, 24.3 +/- 12.1, 6.3 +/- 5.6, 0.56 +/- 0.50 and 0.44 +/- 0.25 micromol/l in the control group, respectively. These levels were also increased in the 400 or 1200 mg/l aspirin groups but less so. These findings may help us to understand the aspirin toxicity in Reye's syndrome.

The influenza B virus mouse model of Reye's syndrome: clinical, virologic and morphologic studies of the encephalopathy

The influenza B virus mouse model of Reye's syndrome was studied to learn more about the encephalopathy in Reye's syndrome. One to 3 days after intravenous influenza B/Lee virus, Balb/c mice became lethargic, seized and lapsed into a fatal coma. Wide-spread cerebral edema without inflammation developed 1-3 days after virus inoculation. Swollen astrocytic foot processes containing increased glial fibrillary acidic protein were located around capillaries. Viral particles were not seen by electron microscopy and complete viral replication did not occur. Immunohistochemical studies demonstrated influenza B viral antigen within many endothelial cells but not within other brain cells. Qualitative (Evans blue dye) and quantitative (percent brain water and technetium -99 pertechnetate) studies of the blood-brain barrier demonstrated abnormalities. This model reproduced many clinical, virologic and pathologic features of the Reye's syndrome encephalopathy. In addition, a non-permissive viral infection of brain endothelial cells occurred which may be important in the pathogenesis of the mouse encephalopathy and may participate in the encephalopathy of Reye's syndrome.

Benefits and risks of antifibrinolytic therapy in the management of ruptured intracranial aneurysms. A double-blind placebo-controlled study

One hundred patients with a verified subarachnoid haemorrhage were studied in a double blind, placebo-controlled trial at a single centre to determine the value and relative risks of tranexamic acid (TXA) in the management of ruptured intracranial aneurysms. The incidence of recurrent haemorrhage between active and placebo groups was identical (12%) and the mortality from recurrent haemorrhage was 7% and 5%, respectively. The overall incidence of cerebral infarction before surgery, at discharge and at 6 months follow-up was greater in the TXA group (27%) than in the control group (11%). Post-operative cerebral ischaemia was significantly more frequent in the active, 18 of 29 as compared to 6 of 32 patients, in the placebo group. In a fifth of the patients in whom cerebral blood flow was estimated there was a significant reduction of cerebral blood flow (CBF) on the side of the ruptured aneurysm in the TXA treated group. It is suggested that this may be the cause of the increased incidence of cerebral ischaemia in this group. There was no significant difference in the incidence of cerebral vasospasm, hydrocephalus, visual disturbances and gastrointestinal disturbances. More fatalities were encountered from ischaemia and recurrent haemorrhage in the TXA group but these differences did not reach statistical significance at the 5% level. Given that disability was due to either vasospasm or recurrent haemorrhage than a patient under TXA treatment was significantly more likely to have disability due to vasospasm (p less than 0.04); the reverse was true for the placebo patient (p less than 0.05).

Animal model of margosa oil ingestion with Reye-like syndrome. Pathogenesis of microvesicular fatty liver

The aetiology and pathogenesis of Reye's syndrome (RS) are incompletely understood. A number of environmental toxins and biological agents, including viruses, have been postulated to cause RS, either acting alone or synergistically. Most investigations have suggested that the primary insult is in the liver mitochondria, leading to a complex biochemical catastrophe, with death from encephalopathy. Margosa oil (MO), a long-chain fatty acid compound, has been shown to cause a Reye-like syndrome with death from hepatoencephalopathy, in children in Malaysia and India. The present time-course study performed in MO-administered mice showed the development of hepatic lesions with many features of RS. MO acts rapidly, within 30 min, on the nuclei of hepatocytes inducing mitoses and binucleated cells. This is followed by mitochondrial injury, with swelling, rarefaction of matrix, loss of dense bodies, pleomorphism, and loss of ribosomes starting at 60 min. There is loss of liver glycogen, and proliferation and hypertrophy of the endoplasmic reticulum (ER), followed by the presence of lipid droplets in the hyaloplasm, and globules within dilated cisterns of the ER. Additional fatty acids from lipolysis of body adipocytes, and fat globules from intestinal MO ingestion further aggravate the liver fatty change. There is evidence of fat globule ingestion by endocytosis into hepatocytes at the level of the sinusoids. The development of microvesicular liver steatosis and glycogen depletion due to involvement of liver cell organelles occur rapidly as in RS.

On octanoic acid-induced hyperventilation--implications for hepatic encephalopathy and Reye's syndrome

Medium chain fatty acid sodium octanoate was infused into rabbits as a 0.2 M solution over 4 h resulting in blood and brain octanoate levels of 200-800 mumol/l. The infused animals developed marked hyperventilation leading to a mild respiratory alkalosis. Additionally, octanoate infusion brought about hyperammonemia and hyperlactate acidemia. Another group of rabbits also infused with octanoate but pretreated with indomethacin (10 mg/kg b.wt.) developed neither hyperventilation nor hyperammonemia. Therefore, the conclusion made was that octanoate causes the above mentioned disorders through stimulation of prostaglandin synthesis and especially the PGE2 synthesis. Patients with hepatic encephalopathy and Reye's syndrome have elevated levels of plasma octanoate. The present study suggests that octanoate might be the cause for both the hyperventilation and hyperammonemia observed in patients with hepatic encephalopathy and Reye's syndrome.

Biochemical relationships between Reye's and Reye's-like metabolic and toxicological syndromes

Reye's syndrome is a hepatic encephalopathy with fatty infiltration of the liver and is due to mitochondrial dysfunction. Knowledge of the mechanisms causing Reye's syndrome has been gained from the study of Reye's syndrome-like diseases, including inborn errors of mitochondrial energy production, viral disease and toxicological injury. Entry of fatty acids into mitochondria or beta-oxidation itself may be impaired. Toxins such as hypoglycin, pentanoate, valproate, salicylate, and their metabolites inhibit beta-oxidation pathways and can produce Reye's syndrome-like presentations. Biochemical manifestations of the diverse causes of Reye's syndrome-like disorders are similar and include: hypoglycaemia due to impaired gluconeogenesis, accumulation of fatty acids, fatty acyl CoAs, and acyl carnitines with depletion of free CoA and carnitine. Accumulated products may further injure mitochondria and exacerbate impaired beta-oxidation, uncouple oxidative phosphorylation or increase mitochondrial permeability. Mitochondrial swelling and steatosis of hepatic cells are the histological result. With the advances of biochemical techniques for the study of organic acid excretion patterns, serum fatty acid patterns and identification of enzymatic deficiencies in cells from patients with Reye's syndrome-like presentations, it is clear that Reye's syndrome is, in part, a collection of various inborn errors and toxicological states. Circumstances such as viral disease, prolonged fasting and drugs may precipitate clinical expression of these deficiencies as Reye's syndrome. As work progresses, further causes of Reye's syndrome will be identified.

2,4-Dichlorophenoxyacetic acid intoxication increases its accumulation within the brain

Exposure to the phenoxyacetic acid herbicides has been shown to produce neurotoxicity. Therefore, adult mice (pregnant) and rabbits were used to examine the accumulation and regional distribution of 2,4-dichlorophenoxyacetic acid (2,4-D) within the brain following intraperitoneal injection of a low dose (0.2-0.4 mg/kg) of [14C]2,4-D. Controls, i.e. animals not previously exposed to 2,4-D, were compared to animals acutely pretreated with higher doses (40-160 mg/kg) of unlabeled 2,4-D. Both autoradiography and direct tissue analysis showed that in control animals brain levels were much lower than plasma in both adult (approximately 4%) and fetus (approximately 8%). In both species, small variations were seen between the brain regions, with brainstem and cerebellum somewhat higher than other regions. Pretreatment with unlabeled 2,4-D caused a 5- to 10-fold increase in accumulation of [14C]2,4-D in both mice and rabbits. On the other hand, 2-deoxyglucose entry into the brain was not altered by 2,4-D pretreatment. Thus, there was no generalized increase in blood-brain barrier permeability. Instead, increased 2,4-D accumulation appeared to be caused by its decreased elimination from the brain. Pretreatment with 40 mg/kg led to a CSF 2,4-D concentration of 10 microM, a concentration sufficient to inhibit choroid plexus transport of [14C]2,4-D by nearly 50% in vitro. These results suggest that exposure to organic anions like 2,4-D may lead to the retention of potentially toxic anions within the CNS via competitive inhibition of the organic anion transport system which normally reduces their brain and CSF concentrations to very low levels.

Inhibition of metabolic processes by coenzyme-A-sequestering aromatic acids. Prevention by para-chloro- and para-nitrobenzoic acids

Octanoate, salicylate, valproic acid, p-octyl-, p-nitro-, and p-chlorobenzoic acids were effective inhibitors of benzoic acid activation to benzoyl-CoA by mitochondrial extracts. p-Aminobenzoic acid was much less effective. Of these compounds, only salicylate and p-nitrobenzoic acid were not activated to their respective CoA esters. Salicylate, p-chloro- and p-nitrobenzoic acids effectively prevented inhibition of glucose synthesis and alpha-keto[1-14C]isovalerate oxidation by valproic acid, p-octyl-, and p-aminobenzoic acids, p-Octyl- and p-aminobenzoic acids greatly depleted hepatocyte free CoA and acetyl-CoA contents and increased the content of acid-insoluble and acid-soluble CoA esters respectively. p-Chloro- and p-nitrobenzoic acids prevented the sequestration of CoA as p-octylbenzoyl-CoA or p-aminobenzoyl-CoA in hepatocytes incubated with these compounds. p-Chlorobenzoic acid not only prevented but also reversed the inhibition of gluconeogenesis in hepatocytes incubated with p-octylbenzoic acid. These results suggest that p-chloro- or p-nitrobenzoic acids might be effectively used to reverse some of the hepatotoxic effects of the CoA esters of valproic acid or naturally-occurring organic acids, such as those which accumulate in Reye's Syndrome or organic acidemias.

Advances in the application of biochemical tests to diseases of the liver and biliary tract: their role in diagnosis, prognosis, and the elucidation of pathogenetic mechanisms

Despite the biochemical complexity of the liver, few laboratory tests provide discriminatory diagnostic information in patients with hepatobiliary disease. Recent efforts have concentrated upon tests which assess the function of the liver, the severity of the disease state, and underlying pathological processes. Bile Acids: The emergence of facile technology and widespread application has brought the realization that these assays are not as sensitive in detecting liver disease as previously believed, although the cholate/chenate ratio may be useful in distinguishing cholestasis from chronic liver disease. The presence of unusual bile acids in serum or urine may be helpful in some cases. Drug Metabolism: A number of tests provide good evidence about liver function, hepatic blood flow and portal shunting, but the aminopyrine breath tests is the most useful, giving prognostic information in acetaminophen overdose and alcoholic liver disease. The antipyrine half-life identifies surgical cases at risk from poor hepatic function. Proteins and Immunochemical Tests: Interest has developed in plasma proteins such as prealbumin and retinol-binding protein to monitor hepatic protein synthetic function. Secretory IgA is more elevated in biliary tract disease, unlike the native protein which is increased principally in cirrhosis. Type III procollagen can be measured in serum, and correlates with the activity of collagen synthesis and the degree of fibrosis in biopsy samples. Reye's Syndrome: Biochemical tests play an essential role in diagnosis of this recently discovered disease. These will be presented and discussed.

[Encephalitis and hepatitis after varicella. Relations with Reye's syndrome]

We report the case of a 32 year old man who present two weeks after a typical varicella an alteration of consciousness with pleocytosis in the cerebrospinal fluid and abnormalities of EEG and CT Scan. An hepatic dysfunction with cytolysis and a high level of transaminases and ammonia was noted. About this case the author precise the encephalitic complication of varicella, and the different liver abnormalities, such as Reye's syndrome, hepatitis with parcellar necrosis, or hepatitis with hyperammonemia but without cytolysis or necrosis, as in our own.

Reye syndrome

Reye syndrome has emerged as the quintessential example of an acute metabolic encephalopathy with an annual incidence ranging from 0.3 to 6.0 cases per 100,000 children. The general management has become standardized, and the mortality has declined to approximately 10 per cent. The role of aspirin in the etiopathogenesis remains controversial.

Early biochemical and EEG correlates of the ketogenic diet in children with atypical absence epilepsy

Early changes in blood chemistry and the electroencephalogram were monitored during the first three hours after initiating the medium chain triglyceride (MCT) diet in nine children with intractable atypical absence seizures. Serum glucose, insulin, triglycerides, cholesterol, free fatty acids, ketone bodies concentrations, and venous pH were assayed before and at timed intervals after MCT oil was administered orally. The concentration of serum ketones rose progressively over three hours, beta-hydroxybutyrate proportionately higher than acetoacetate. A statistically significant decrease in the group mean number of epileptiform discharges occurred following MCT therapy. Seizure frequency decreased by more than 50 percent in two-thirds of the children during the 10 week treatment period.

Effect of octanoate injection on rat blood-brain barrier

Serum concentrations of short and medium chain fatty acids, including octanoate, are elevated in hepatic encephalopathy and Reye syndrome. Injection of octanoate into animals produces features reminiscent of Reye syndrome, but the mechanisms are unknown. To evaluate the effect of octanoate on blood-brain barrier permeability, three techniques were used. Entry of horseradish peroxidase and trypan blue into brain was not observed after octanoate injection. Brain uptake of tryptamine, tyrosine and methionine was increased significantly by octanoate, while uptake of insulin was unchanged. This study suggests that octanoate may produce central nervous system alterations by facilitating entry of certain low molecular weight compounds into brain. This may represent one mechanism for the development of encephalopathy in liver disease and Reye syndrome.

Morphologic grading of hepatic mitochondrial alteration in Reye's syndrome: potential prognostic implication

Mitochondrial alterations are known to be constantly associated with Reye's syndrome. Fifty-eight liver specimens from 50 patients who fulfilled the clinical and pathologic criteria were examined by electron microscopy. The degree of mitochondrial injury was graded I, II, and III according to the severity of the alteration of mitochondrial matrix. The results correlated well with clinical parameters--specifically initial clinical stage, peak clinical stage, and clinical outcome. Electron microscopic examination of hepatic mitochondria is therefore potentially useful in evaluating Reye's syndrome patients.

A proposed therapy for the encephalopathies of Reye's syndrome and hepatic encephalopathy

On the basis of information known about the pathogenesis of Reye's Syndrome and Hepatic Encephalopathy, and the effect of specific pharmacologic agents at the benzodiazepine receptor it is hypothesized that benzodiazepine receptor antagonists and contragonists will be of therapeutic value in those disorders.

Substrates of energy metabolism of the pituitary and pineal glands

The capability of the neurohypophysis, the adenohypophysis, and the pineal gland to oxidize nonesterified fatty acids and glucose as energy sources was studied in vivo. Fed and 48-h-starved rats had catheters placed in their femoral vessels. After they became conscious, an intravenous injection of one of the following was given: [1-14C]acetate, [1-14C]octanoate, [1-14C]-palmitate, or [2-14C]glucose. After 5 min the rats were sacrificed. These metabolites produce [14C]acetyl-CoA within the mitochondria when they are oxidized as metabolic fuels. On passage through the Krebs cycle a considerable portion of the 14C is trapped in large amino acid pools closely associated with the Krebs cycle; the appearance of 14C in these amino acids was taken as evidence of oxidation. As expected, brain structures behind the blood-brain barrier (cerebral cortex and caudate) showed considerable labeling of Krebs cycle-associated amino acids in both nutritional states when [2-14C]glucose was the substrate. Surprisingly, however, no label was detected in amino acids of the neurohypophysis or the pineal gland in starved rats and very little in fed rats. On the other hand, 14C from acetate and palmitate was extensively incorporated into amino acids of the pineal gland and the neurohypophysis, while little 14C labeling was found in the cerebral cortex and the caudate. Octanoate, which passes the blood-brain barrier readily, labeled amino acids of all tissues. The experiments demonstrated conclusively that the neural structures studied, which have no blood-brain barrier, do not rely heavily upon glucose as a fuel for oxidative energy metabolism, in contrast to the rest of the brain. The results also showed that nonesterified fatty acids may supply at least some of their energy requirements.

Effect of increasing carbon chain length on organic acid transport by the choroid plexus: a potential factor in Reye's syndrome

Transport of the anionic herbicide 2,4-dichlorophenoxyacetic acid by choroid plexus is inhibited significantly by several short and medium chain acids. For both monocarboxylic and dicarboxylic homologs, inhibition clearly increases with chain length. It appears that organic acid compounds of longer chain length, higher brain uptake index, and highest inhibition of choroid plexus transport would be the ones producing the most significant increases in intracranial pressure in metabolic encephalopathy such as Reye's syndrome.

Ruptured intracranial aneurysms: has the incidence of early rebleeding been over-estimated?

Of 110 consecutive patients with ruptured intracranial aneurysms, 49 underwent delayed neurological deterioration, involving 57 episodes in all. During the first three weeks after the presenting haemorrhage less than a third of these episodes were due to confirmed rebleeding. Rebleeding episodes were found to have a "flat" distribution in time during this period, but episodes of non-haemorrhagic deterioration "peaked" between days 4-12. This peak coincides with the peak for rebleeding which was described in earlier studies on aneurysms, and it is suggested that confusion between non-haemorrhagic deterioration and rebleeding may have led to a significant over-estimate of the incidence of early rebleeding with important implications for the optimum timing of surgical intervention.

Effect of chain length of short-chain fatty acids on their effect on intracranial pressure in rabbits

The short-chain fatty acids propionic, butyric, valeric, isovaleric and octanoic produced elevations in intracranial pressure during intravenous infusion in rabbits. Serum concentrations of these compounds are elevated in patients with Reye's syndrome, and may contribute to the intracranial pressure elevations found in these patients.

Neuropathology, pathogenesis, and neuropsychiatric sequelae of Reye syndrome

A clinico-pathologic correlation can be established for those survivors of Reye syndrome in the higher clinical stages who have sustained irreversible and often major neuropsychiatric deficits. The neuropathologic substrate for the clinical manifestations of mental retardation, recurrent seizures, movement disorders, sensori-motor deficits, psychobiologic maladjustment, and mediocre performance in school and on formal psychometric tests consists of multifocal infarction and astrocytosis in cerebral cortex, diencephalon, basal ganglia, and brainstem. While the mortality rate of Reye syndrome in acute stages is still significantly high (25% in our 20 cases, 52% in the tabulated cases in the higher clinical grades), the occurrence of permanent psychomotor deficits is an equally tragic socioeconomic and medical problem. Of our 15 survivors, 3 have suffered major and 1 has sustained minor brain damage. From a review of the literature, over one-third of survivors are consigned to cerebral malfunction, hence their potential for full enjoyment of life and their intellectual, emotional, and economic contributions to their families and society are sadly curtailed.

Comparative clinical trial of epsilon amino-caproic acid and tranexamic acid in the prevention of early recurrence of subarachnoid haemorrhage

A comparative controlled clinical trial of epsilon aminocaproic acid (EACA), 36 g/day and tranexamic acid (TEA), 6 g/day, was undertaken to assess their effectiveness in reducing early recurrence of subarachnoid haemorrhage (SAH). Of 90 patients treated with EACA recurrent haemorrhage was seen in 8% of these patients and 7% of the patients developed delayed ischaemic deficit. The total pre-operative mortality in EACA-group was 11%. Of 61 patients treated with TEA, 10% had recurrent haemorrhage and delayed ischaemic deficit occurred in 5% of the patients. The total pre-operative mortality in TEA-group was 11%. No difference was found between the effectiveness and side-effects of these drugs.

Anti-fibrinolytic treatment in the pre-operative management of subarachnoid haemorrhage caused by ruptured intracranial aneurysm

One hundred consecutive patients treated with epsilon aminocaproic acid 24 grams daily prior to surgery for ruptured intracranial aneurysms have been compared with the previous 100 patients managed similarly but without anti-fibrinolytic drugs. No other alterations in management were made and the two series are closely comparable in all other respects. Fewer episodes of recurrent haemorrhage and deaths from this cause occurred in the treated patients, but more cases of cerebral ischaemia occurred. Neither difference is statistically significant and overall more deaths occurred in the patients treated with antifibrinolytic drugs. The value of this method of treatment in the management of aneurysmal subarachnoid haemorrhage is questioned.

Treatment of Reye syndrome

Although the underlying cause of Reye syndrome is not understood, an effective approach to treatment is based on reversing the known metabolic and pathological abnormalities. A multifaceted therapeutic approach aimed at correcting metabolic derangements and combating intracranial hypertension can result in complete recovery from severe cases of Reye syndrome.