Influenza D Virus in Cattle, Ireland Flynn, Orla; Gallagher, Clare; Mooney, Jean ...
Emerging infectious diseases,
02/2018, Letnik:
24, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We detected influenza D virus in 18 nasal swab samples from cattle in Ireland that were clinically diagnosed with respiratory disease. Specimens were obtained from archived samples received for ...routine diagnosis during 2014-2016. Sequencing showed that viruses from Ireland clustered with virus sequences obtained in Europe within the D/swine/OK/1334/2011 clade.
Microdialysis enables the chemistry of the extracellular interstitial space to be monitored. Use of this technique in patients with acute brain injury has increased our understanding of the ...pathophysiology of several acute neurological disorders. In 2004, a consensus document on the clinical application of cerebral microdialysis was published. Since then, there have been significant advances in the clinical use of microdialysis in neurocritical care. The objective of this review is to report on the International Microdialysis Forum held in Cambridge, UK, in April 2014 and to produce a revised and updated consensus statement about its clinical use including technique, data interpretation, relationship with outcome, role in guiding therapy in neurocritical care and research applications.
Brain metabolism is thought to be maintained by neuronal-glial metabolic coupling. Glia take up glutamate from the synaptic cleft for conversion into glutamine, triggering glial glycolysis and ...lactate production. This lactate is shuttled into neurons and further metabolized. The origin and role of lactate in severe traumatic brain injury (TBI) remains controversial. Using a modified weight drop model of severe TBI and magnetic resonance (MR) spectroscopy with infusion of 13C-labeled glucose, lactate, and acetate, the present study investigated the possibility that neuronal-glial metabolism is uncoupled following severe TBI. Histopathology of the model showed severe brain injury with subarachnoid and hemorrhage together with glial cell activation and positive staining for Tau at 90 min post-trauma. High resolution MR spectroscopy of brain metabolites revealed significant labeling of lactate at C-3 and C-2 irrespective of the infused substrates. Increased 13C-labeled lactate in all study groups in the absence of ischemia implied activated astrocytic glycolysis and production of lactate with failure of neuronal uptake (i.e. a loss of glial sensing for glutamate). The early increase in extracellular lactate in severe TBI with the injured neurons rendered unable to pick it up probably contributes to a rapid progression toward irreversible injury and pan-necrosis. Hence, a method to detect and scavenge the excess extracellular lactate on site or early following severe TBI may be a potential primary therapeutic measure.
Background: In brain metabolism, neurons are fueled by lactate passed to them by glia in a metabolic coupling.
Results: Following brain trauma, lactate uptake into neurons from glia was impaired, producing a metabolic lactate storm.
Conclusion: Brain trauma results in neuronal-glial metabolic uncoupling, releasing free lactate.
Significance: Inhibition of lactate production or its removal may be an important therapeutic strategy for brain trauma.
To summarize randomized controlled trials on the effects of sedative agents on neurologic outcome, mortality, intracranial pressure, cerebral perfusion pressure, and adverse drug events in critically ...ill adults with severe traumatic brain injury.
PubMed, MEDLINE, EMBASE, the Cochrane Database, Google Scholar, two clinical trials registries, personal files, and reference lists of included articles.
Randomized controlled trials of propofol, ketamine, etomidate, and agents from the opioid, benzodiazepine, α-2 agonist, and antipsychotic drug classes for management of adult intensive care unit patients with severe traumatic brain injury.
In duplicate and independently, two investigators extracted data and evaluated methodologic quality and results.
Among 1,892 citations, 13 randomized controlled trials enrolling 380 patients met inclusion criteria. Long-term sedation (≥24 hrs) was addressed in six studies, whereas a bolus dose, short infusion, or doubling of plasma drug concentration was investigated in remaining trials. Most trials did not describe baseline traumatic brain injury prognostic factors or important cointerventions. Eight trials possibly or definitely concealed allocation and six were blinded. Insufficient data exist regarding the effects of sedative agents on neurologic outcome or mortality. Although their effects are likely transient, bolus doses of opioids may increase intracranial pressure and decrease cerebral perfusion pressure. In one study, a long-term infusion of propofol vs. morphine was associated with a reduced requirement for intracranial pressure-lowering cointerventions and a lower intracranial pressure on the third day. Trials of propofol vs. midazolam and ketamine vs. sufentanil found no difference between agents in intracranial pressure and cerebral perfusion pressure.
This systematic review found no convincing evidence that one sedative agent is more efficacious than another for improvement of patient-centered outcomes, intracranial pressure, or cerebral perfusion pressure in critically ill adults with severe traumatic brain injury. High bolus doses of opioids, however, have potentially deleterious effects on intracranial pressure and cerebral perfusion pressure. Adequately powered, high-quality, randomized controlled trials are urgently warranted.
Following traumatic brain injury, complex cerebral energy perturbations occur. Correlating with unfavourable outcome, high brain extracellular lactate/pyruvate ratio suggests hypoxic metabolism ...and/or mitochondrial dysfunction. We investigated whether focal administration of succinate, a tricarboxylic acid cycle intermediate interacting directly with the mitochondrial electron transport chain, could improve cerebral metabolism. Microdialysis perfused disodium 2,3-13C2 succinate (12 mmol/L) for 24 h into nine sedated traumatic brain injury patients' brains, with simultaneous microdialysate collection for ISCUS analysis of energy metabolism biomarkers (nine patients) and nuclear magnetic resonance of 13C-labelled metabolites (six patients). Metabolites 2,3-13C2 malate and 2,3-13C2 glutamine indicated tricarboxylic acid cycle metabolism, and 2,3-13C2 lactate suggested tricarboxylic acid cycle spinout of pyruvate (by malic enzyme or phosphoenolpyruvate carboxykinase and pyruvate kinase), then lactate dehydrogenase-mediated conversion to lactate. Versus baseline, succinate perfusion significantly decreased lactate/pyruvate ratio (p = 0.015), mean difference −12%, due to increased pyruvate concentration (+17%); lactate changed little (−3%); concentrations decreased for glutamate (−43%) (p = 0.018) and glucose (−15%) (p = 0.038). Lower lactate/pyruvate ratio suggests better redox status: cytosolic NADH recycled to NAD+ by mitochondrial shuttles (malate-aspartate and/or glycerol 3-phosphate), diminishing lactate dehydrogenase-mediated pyruvate-to-lactate conversion, and lowering glutamate. Glucose decrease suggests improved utilisation. Direct tricarboxylic acid cycle supplementation with 2,3-13C2 succinate improved human traumatic brain injury brain chemistry, indicated by biomarkers and 13C-labelling patterns in metabolites.
Metabolic abnormalities occur after traumatic brain injury (TBI). Glucose is conventionally regarded as the major energy substrate, although lactate can also be an energy source. We compared 3-
C ...lactate metabolism in TBI with "normal" control brain and muscle, measuring
C-glutamine enrichment to assess tricarboxylic acid (TCA) cycle metabolism. Microdialysis catheters in brains of nine patients with severe TBI, five non-TBI brain surgical patients, and five resting muscle (non-TBI) patients were perfused (24 h in brain, 8 h in muscle) with 8 mmol/L sodium 3-
C lactate. Microdialysate analysis employed ISCUS and nuclear magnetic resonance. In TBI, with 3-
C lactate perfusion, microdialysate glucose concentration increased nonsignificantly (mean +11.9%, p = 0.463), with significant increases (p = 0.028) for lactate (+174%), pyruvate (+35.8%), and lactate/pyruvate ratio (+101.8%). Microdialysate
C-glutamine fractional enrichments (median, interquartile range) were: for C4 5.1 (0-11.1) % in TBI and 5.7 (4.6-6.8) % in control brain, for C3 0 (0-5.0) % in TBI and 0 (0-0) % in control brain, and for C2 2.9 (0-5.7) % in TBI and 1.8 (0-3.4) % in control brain.
C-enrichments were not statistically different between TBI and control brain, showing both metabolize 3-
C lactate via TCA cycle, in contrast to muscle. Several patients with TBI exhibited
C-glutamine enrichment above the non-TBI control range, suggesting lactate oxidative metabolism as a TBI "emergency option."
Increased 'anaerobic' glucose metabolism is observed after traumatic brain injury (TBI) attributed to increased glycolysis. An alternative route is the pentose phosphate pathway (PPP), which ...generates putatively protective and reparative molecules. To compare pathways we employed microdialysis to perfuse 1,2-(13)C2 glucose into the brains of 15 TBI patients and macroscopically normal brain in six patients undergoing surgery for benign tumors, and to simultaneously collect products for nuclear magnetic resonance (NMR) analysis. (13)C enrichment for glycolytic 2,3-(13)C2 lactate was the median 5.4% (interquartile range (IQR) 4.6-7.5%) in TBI brain and 4.2% (2.4-4.4%) in 'normal' brain (P<0.01). The ratio of PPP-derived 3-(13)C lactate to glycolytic 2,3-(13)C2 lactate was median 4.9% (3.6-8.2%) in TBI brain and 6.7% (6.3-8.9%) in 'normal' brain. An inverse relationship was seen for PPP-glycolytic lactate ratio versus PbtO2 (r=-0.5, P=0.04) in TBI brain. Thus, glycolytic lactate production was significantly greater in TBI than 'normal' brain. Several TBI patients exhibited PPP-lactate elevation above the 'normal' range. There was proportionally greater PPP-derived lactate production with decreasing PbtO2. The study raises questions about the roles of the PPP and glycolysis after TBI, and whether they can be manipulated to achieve a better outcome. This study is the first direct comparison of glycolysis and PPP in human brain.
Background
Guidelines recommend maintaining cerebral perfusion pressure (CPP) between 60 and 70 mmHg in patients with severe traumatic brain injury (TBI), but acknowledge that optimal CPP may vary ...depending on cerebral blood flow autoregulation. Previous retrospective studies suggest that targeting CPP where the pressure reactivity index (PRx) is optimized (CPP
opt
) may be associated with improved recovery.
Methods
We performed a retrospective cohort study involving TBI patients who underwent PRx monitoring to assess issues of feasibility relevant to future interventional studies: (1) the proportion of time that CPP
opt
could be detected; (2) inter-observer variability in CPP
opt
determination; and (3) agreement between manual and automated CPP
opt
estimates. CPP
opt
was determined for consecutive 6-h epochs during the first week following TBI. Sixty PRx-CPP tracings were randomly selected and independently reviewed by six critical care professionals. We also assessed whether greater deviation between actual CPP and CPP
opt
(ΔCPP) was associated with poor outcomes using multivariable models.
Results
In 71 patients, CPP
opt
could be manually determined in 985 of 1173 (84%) epochs. Inter-observer agreement for detectability was moderate (kappa 0.46, 0.23–0.68). In cases where there was consensus that it could be determined, agreement for the specific CPP
opt
value was excellent (weighted kappa 0.96, 0.91–1.00). Automated CPP
opt
was within 5 mmHg of manually determined CPP
opt
in 93% of epochs. Lower PRx was predictive of better recovery, but there was no association between ΔCPP and outcome. Percentage time spent below CPP
opt
increased over time among patients with poor outcomes (
p
= 0.03). This effect was magnified in patients with impaired autoregulation (defined as PRx > 0.2;
p
= 0.003).
Conclusion
Prospective interventional clinical trials with regular determination of CPP
opt
and corresponding adjustment of CPP goals are feasible, but measures to maximize consistency in CPP
opt
determination are necessary. Although we could not confirm a clear association between ΔCPP and outcome, time spent below CPP
opt
may be particularly harmful, especially when autoregulation is impaired.
How to optimise glucose metabolism in the traumatised human brain remains unclear, including whether injured brain can metabolise additional glucose when supplied. We studied the effect of ...microdialysis-delivered 1,2-13C2 glucose at 4 and 8 mmol/L on brain extracellular chemistry using bedside ISCUSflex, and the fate of the 13C label in the 8 mmol/L group using high-resolution NMR of recovered microdialysates, in 20 patients. Compared with unsupplemented perfusion, 4 mmol/L glucose increased extracellular concentrations of pyruvate (17%, p = 0.04) and lactate (19%, p = 0.01), with a small increase in lactate/pyruvate ratio (5%, p = 0.007). Perfusion with 8 mmol/L glucose did not significantly influence extracellular chemistry measured with ISCUSflex, compared to unsupplemented perfusion. These extracellular chemistry changes appeared influenced by the underlying metabolic states of patients’ traumatised brains, and the presence of relative neuroglycopaenia. Despite abundant 13C glucose supplementation, NMR revealed only 16.7% 13C enrichment of recovered extracellular lactate; the majority being glycolytic in origin. Furthermore, no 13C enrichment of TCA cycle-derived extracellular glutamine was detected. These findings indicate that a large proportion of extracellular lactate does not originate from local glucose metabolism, and taken together with our earlier studies, suggest that extracellular lactate is an important transitional step in the brain’s production of glutamine.
A key pathophysiological process and therapeutic target in the critical early post-injury period of traumatic brain injury (TBI) is cell mitochondrial dysfunction; characterised by elevation of brain ...lactate/pyruvate (L/P) ratio in the absence of hypoxia. We previously showed that succinate can improve brain extracellular chemistry in acute TBI, but it was not clear if this translates to a change in downstream energy metabolism. We studied the effect of microdialysis-delivered succinate on brain energy state (phosphocreatine/ATP ratio (PCr/ATP)) with
P MRS at 3T, and tissue NADH/NAD
redox state using microdialysis (L/P ratio) in eight patients with acute major TBI (mean 7 days). Succinate perfusion was associated with increased extracellular pyruvate (+26%, p < 0.0001) and decreased L/P ratio (-13%, p < 0.0001) in patients overall (baseline-vs-supplementation over time), but no clear-cut change in
P MRS PCr/ATP existed in our cohort (p > 0.4, supplemented-voxel-vs-contralateral voxel). However, the percentage decrease in L/P ratio for each patient following succinate perfusion correlated significantly with their percentage increase in PCr/ATP ratio (Spearman's rank correlation, r = -0.86, p = 0.024). Our findings support the interpretation that L/P ratio is linked to brain energy state, and that succinate may support brain energy metabolism in select TBI patients suffering from mitochondrial dysfunction.
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