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Pre‐term birth is associated with physiological sequelae that persist into adulthood. In particular, modulated ventilatory responsiveness to hypoxia and hypercapnia has been observed in this population. Whether pre‐term birth per se causes these effects remains unclear. Therefore, we aimed to assess pulmonary ventilation and blood gases under various environmental conditions, comparing 17 healthy prematurely born individuals (mean ± SD; gestational age, 28 ± 2 weeks; age, 21 ± 4 years; peak oxygen uptake, 48.1 ± 11.2 ml kg−1 min−1) with 16 well‐matched adults born at term (gestational age, 40 ± 1 weeks; age, 22 ± 2 years; peak oxygen uptake, 51.2 ± 7.7 ml kg−1 min−1). Participants were exposed to seven combinations of hypoxia/hypobaria (equivalent to ∼3375 m) and/or hypercapnia (3% CO2), at rest for 6 min. Pulmonary ventilation, pulse oxygen saturation and the arterial partial pressures of O2 and CO2 were similar in pre‐term and full‐term individuals under all conditions. Higher ventilation in hypoxia compared to normoxia was only observed at terrestrial altitude, despite an equivalent (normobaric) hypoxic stimulus administered at sea level (0.138 FiO2${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$). Assessment of oscillations in key variables revealed that combined hypoxic hypercapnia induced greater underlying fluctuations in ventilation in pre‐term individuals only. In general, higher pulse oxygen saturation fluctuations were observed with hypoxia, and lower fluctuations in end‐tidal CO2 with hypercapnia, despite similar ventilatory oscillations observed between conditions. These findings suggest that healthy prematurely born adults display similar overall ventilation to their term‐born counterparts under various environmental stressors, but that combined ventilatory stimuli could induce an irregular underlying ventilatory pattern. Moreover, barometric pressure may be an important factor when assessing ventilatory responsiveness to moderate hypoxic stimuli. Key points: Evidence exists for unique pulmonary and respiratory function under hypoxic conditions in adult survivors of pre‐term birth. Whether pre‐term birth per se causes these differences requires a comparison of conventionally healthy prematurely born adults with an appropriately matched sample of term‐born individuals.According to the present data, there is no difference between healthy pre‐term and well‐matched term‐born individuals in the magnitude of pulmonary ventilation or arterial blood gases during independent and combined hypobaria, hypoxia and hypercapnia.Terrestrial altitude (hypobaria) was necessary to induce differences in ventilation between normoxia and a hypoxic stimulus equivalent to ∼3375 m of altitude. Furthermore, peak power in pulse oxygen saturation was similar between hypobaric normoxia and normobaric hypoxia.The observed similarities between groups suggest that ventilatory regulation under various environmental stimuli is not impaired by pre‐term birth per se. Instead, an integrated combination of neonatal treatment strategies and cardiorespiratory fitness/disease status might underlie previously observed chemosensitivity impairments. [ABSTRACT FROM AUTHOR]

We have examined the importance of three long‐standing questions concerning chemoreceptor influences on cardiorespiratory function which are currently experiencing a resurgence of study among physiologists and clinical investigators. Firstly, while carotid chemoreceptors (CB) are required for hypoxic stimulation of breathing, use of an isolated, extracorporeally perfused CB preparation in unanaesthetized animals with maintained tonic input from the CB, reveals that extra‐CB hypoxaemia also provides dose‐dependent ventilatory stimulation sufficient to account for 40–50% of the total ventilatory response to steady‐state hypoxaemia. Extra‐CB hyperoxia also provides a dose‐ and time‐dependent hyperventilation. Extra‐CB sites of O2‐driven ventilatory stimulation identified to date include the medulla, kidney and spinal cord. Secondly, using the isolated or denervated CB preparation in awake animals and humans has demonstrated a hyperadditive effect of CB sensory input on central CO2 sensitivity, so that tonic CB activity accounts for as much as 35–40% of the normal, air‐breathing eupnoeic drive to breathe. Thirdly, we argue for a key role for CO2 chemoreception and the neural drive to breathe in the pathogenesis of upper airway obstruction during sleep (OSA), based on the following evidence: (1) removal of the wakefulness drive to breathe enhances the effects of transient CO2 changes on breathing instability; (2) oscillations in respiratory motor output precipitate pharyngeal obstruction in sleeping subjects with compliant, collapsible airways; and (3) in the majority of patients in a large OSA cohort, a reduced neural drive to breathe accompanied reductions in both airflow and pharyngeal airway muscle dilator activity, precipitating airway obstruction. [ABSTRACT FROM AUTHOR]

Deleterious Ca2+ accumulation is central to hypoxic cell death in the brain of most mammals. Conversely, hypoxia‐mediated increases in cytosolic Ca2+ are retarded in hypoxia‐tolerant naked mole‐rat brain. We hypothesized that naked mole‐rat brain mitochondria have an enhanced capacity to buffer exogenous Ca2+ and examined Ca2+ handling in naked mole‐rat cortical tissue. We report that naked mole‐rat brain mitochondria buffer >2‐fold more exogenous Ca2+ than mouse brain mitochondria, and that the half‐maximal inhibitory concentration (IC50) at which Ca2+ inhibits aerobic oxidative phosphorylation is >2‐fold higher in naked mole‐rat brain. The primary driving force of Ca2+ uptake is the mitochondrial membrane potential (Δψm), and the IC50 at which Ca2+ decreases Δψm is ∼4‐fold higher in naked mole‐rat than mouse brain. The ability of naked mole‐rat brain mitochondria to safely retain large volumes of Ca2+ may be due to ultrastructural differences that support the uptake and physical storage of Ca2+ in mitochondria. Specifically, and relative to mouse brain, naked mole‐rat brain mitochondria are larger and have higher crista density and increased physical interactions between adjacent mitochondrial membranes, all of which are associated with improved energetic homeostasis and Ca2+ management. We propose that excessive Ca2+ influx into naked mole‐rat brain is buffered by physical storage in large mitochondria, which would reduce deleterious Ca2+ overload and may thus contribute to the hypoxia and ischaemia‐tolerance of naked mole‐rat brain. Key points: Unregulated Ca2+ influx is a hallmark of hypoxic brain death; however, hypoxia‐mediated Ca2+ influx into naked mole‐rat brain is markedly reduced relative to mice.This is important because naked mole‐rat brain is robustly tolerant against in vitro hypoxia, and because Ca2+ is a key driver of hypoxic cell death in brain.We show that in hypoxic naked mole‐rat brain, oxidative capacity and mitochondrial membrane integrity are better preserved following exogenous Ca2+ stress.This is due to mitochondrial buffering of exogenous Ca2+ and is driven by a mitochondrial membrane potential‐dependant mechanism.The unique ultrastructure of naked mole‐rat brain mitochondria, as a large physical storage space, may support increased Ca2+ buffering and thus hypoxia‐tolerance. [ABSTRACT FROM AUTHOR]

The present investigation aimed to study the cardiovascular responses and the cerebral oxygenation (Cox) during exercise in acute hypoxia and with contemporary mental stress. Fifteen physically active, healthy males (age 29.0 ± 5.9 years) completed a cardiopulmonary test on a cycle ergometer to determine the workload at their gas exchange threshold (GET). On a separate day, participants performed two randomly assigned exercise tests pedaling for 6 min at a workload corresponding to 80% of the GET: (1) during normoxia (NORMO), and (2) during acute, normobaric hypoxia at 13.5% inspired oxygen (HYPO). During the last 3 min of the exercise, they also performed a mental task (MT). Hemodynamics were assessed with impedance cardiography, and peripheral arterial oxygen saturation and Cox were continuously measured by near-infrared spectroscopy. The main results were that both in NORMO and HYPO conditions, the MT caused a significant increase in the heart rate and ventricular filling rate. Moreover, MT significantly reduced (74.8 ± 5.5 vs. 62.0 ± 5.2 A.U.) Cox, while the reaction time (RT) increased (813.3 ± 110.2 vs. 868.2 ± 118.1 ms) during the HYPO test without affecting the correctness of the answers. We conclude that in young, healthy males, adding an MT during mild intensity exercise in both normoxia and acute moderate (normobaric) hypoxia induces a similar hemodynamic response. However, MT and exercise in HYPO cause a decrease in Cox and an impairment in RT. [ABSTRACT FROM AUTHOR]

Background: SafeBoosC-III is a pragmatic, multinational clinical trial evaluating cerebral oximetry-guided treatment for extremely preterm infants. In total, 1601 infants were randomised across 70 sites in Asia, Europe, and USA. To enhance data quality and patient care, a web-based training program was implemented for staff. We now report on the processes. Methods: All training modules consisted of initial learning material followed by a case-based quiz, with elaborate responses to correct as well as to wrong answers. Modules covered trial introduction, cerebral oximetry monitoring, treatment guidelines, cerebral ultrasound, and Good Clinical Practice. The introduction module was accessible in eight languages on an online platform, while language versions varied for other modules, due to different needs. Certification was earned upon module completion, relevant to the staff category. The training was not mandatory, but for motivational purposes, principal investigators continuously received local certification rate reports. Results: A total of 926 out of 2347 staff (39%) obtained certification. Amongst 295 staff who completed the evaluation, 83% rated the program as overall good and 94% found it relevant to clinical practice. Sites exhibited varying certification rates, with 10 at 0%, 43 between 0.1 and 79.9%, and 17 exceeding 80%. There was no correlation between the rate of certification in individual sites and how often the clinical management was changed due to cerebral hypoxia nor a correlation to site-specific estimates of the intervention effect. Conclusion: Despite language barriers and a low budget, our web-based training and certification program proved feasible. Only a minority of sites reached 80% certification of staff and an impact on the trial could not be detected. Trial registration: The SafeBoosC-III trial is registered at ClinicalTrials.gov NCT03770741. The first participant was randomised in June 2019 and recruitment was completed in December 2021. [ABSTRACT FROM AUTHOR]

Patients with acute brain injury are vulnerable to secondary deterioration, which may go undetected by traditional monitoring. However, multimodal neuromonitoring of brain tissue oxygen tension (PbtO2) and energy metabolism may be able to detect such episodes. We report a retrospective, observational study of 94 patients with aneurysmal subarachnoid haemorrhage (SAH) or traumatic brain injury (TBI) who underwent multimodal neuromonitoring during admission. We examined the co-occurrence of pathological neuromonitoring values: elevated intracranial pressure (ICP, > 20 mmHg), inadequate cerebral perfusion pressure (CPP, < 60 mmHg), brain hypoxia (PbtO2 < 20 mmHg), and metabolic crisis (lactate/pyruvate ratio > 40 and a glucose level < 0.2 mmol/L in cerebral microdialysate). Mixed effects linear regression demonstrated significant associations between abnormal ICP/CPP, cerebral hypoxia and metabolic crisis. However, brain hypoxia occurred in 40% and 31% of observations in patients with SAH and TBI, respectively, despite normal concurrent values of ICP. Similarly, metabolic crisis was observed in 8% and 16% of measurements for SAH and TBI, respectively, despite a normal ICP. The pattern was identical for CPP. In conclusion, although all neuromonitoring variables are interrelated, brain hypoxia and metabolic crisis are common despite an absence of abnormalities in conventional monitoring. Multimodal neuromonitoring may help identify such episodes and guide individualised treatment. [ABSTRACT FROM AUTHOR]

The human brain is highly dependent on oxygen, utilizing approximately 20% of the body's oxygen at rest. Oxygen deprivation to the brain can lead to loss of consciousness within seconds and death within minutes. Recent studies have identified regions of the brain with spontaneous episodic hypoxia, referred to as "hypoxic pockets". Hypoxia can also result from impaired blood flow due to conditions such as heart disease, blood clots, stroke, or hemorrhage, as well as from reduced oxygen intake or excessive oxygen consumption caused by factors like low ambient oxygen, pulmonary diseases, infections, inflammation, and cancer. Severe hypoxia in the brain can manifest symptoms similar to Parkinson's disease (PD), including cerebral edema, mood disturbances, and cognitive impairments. Additionally, the development of PD appears to be closely associated with hypoxia and hypoxic pathways. This review seeks to investigate the molecular interactions between hypoxia and PD, emphasizing the pathological role of hypoxic pathways in PD and exploring their potential as therapeutic targets. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disorder with a distinct sex bias. Age‐related vascular alterations, a hallmark of AD onset and progression, are consistently associated with sexual dimorphism. Here, we conducted an integrative meta‐analysis of 335,803 single‐nucleus transcriptomes and 667 bulk transcriptomes from the vascular system in AD and normal aging to address the underlying sex‐dependent vascular aging in AD. All vascular cell types in male AD patients exhibited an activated hypoxia response and downstream signaling pathways including angiogenesis. The female AD vasculature is characterized by increased antigen presentation and decreased angiogenesis. We further confirmed that these sex‐biased alterations in the cerebral vascular emerged and were primarily determined in the early stages of AD. Sex‐stratified analysis of normal vascular aging revealed that angiogenesis and various stress‐response genes were downregulated concurrently with female aging. Conversely, the hypoxia response increased steadily in males upon aging. An investigation of upstream driver transcription factors (TFs) revealed that altered communication between estrogen receptor alpha (ESR1) and hypoxia induced factors during menopause contributes to the inhibition of angiogenesis during normal female vascular aging. Additionally, inhibition of CREB1, a TF that targets estrogen, is also related to female AD. Overall, our study revealed a distinct cerebral vascular profile in females and males, and revealed novel targets for precision medicine therapy for AD. [ABSTRACT FROM AUTHOR]

Introduction: A well-known complication of veno-arterial extracorporeal membrane oxygenation (VA ECMO) is differential hypoxia, in which poorly-oxygenated blood ejected from the left ventricle mixes with and displaces well-oxygenated blood from the circuit, thereby causing cerebral hypoxia and ischemia. We sought to characterize the impact of patient size and anatomy on cerebral perfusion under a range of different VA ECMO flow conditions. Methods: We use one-dimensional (1D) flow simulations to investigate mixing zone location and cerebral perfusion across 10 different levels of VA ECMO support in eight semi-idealized patient geometries, for a total of 80 scenarios. Measured outcomes included mixing zone location and cerebral blood flow (CBF). Results: Depending on patient anatomy, we found that a VA ECMO support ranging between 67-97% of a patient's ideal cardiac output was needed to perfuse the brain. In some cases, VA ECMO flows exceeding 90% of the patient's ideal cardiac output are needed for adequate cerebral perfusion. Conclusions: Individual patient anatomy markedly affects mixing zone location and cerebral perfusion in VA ECMO. Future fluid simulations of VA ECMO physiology should incorporate varied patient sizes and geometries in order to best provide insights toward reducing neurologic injury and improved outcomes in this patient population. [ABSTRACT FROM AUTHOR]

This study aims to investigate the neuroprotective effects of cannabidiol (CBD) on neurodevelopmental impairments in rats subjected to neonatal hypoxia, specifically examining its potential to mitigate motor and sensory deficits without the confounding effects of ischemia. Neonatal Sprague-Dawley rats were allocated to one of four groups: Control, Control-CBD, Hypoxia, and Hypoxia-CBD. Hypoxia was induced on postnatal days 0 and 1. CBD (50 mg/kg) was administered orally for 14 days starting at postnatal day 0. Neurodevelopmental outcomes were assessed using the Neurodevelopmental Reflex Testing in Neonatal Rat Pups scale and the Revised Neurobehavioral Severity Scale for rodents. Statistical analyses were conducted using two-way and one-way ANOVA, with Tukey's post-hoc tests for group comparisons. Pup weights were recorded on specified postnatal days, with no significant differences observed across the groups (p = 0.1834). Significant neurological impairments due to hypoxia were noted in the Control group compared to the Hypoxia group, particularly in hindlimb grasping on postnatal day 3 (p = 0.0025), posture on postnatal day 12 (p = 0.0073), and in general balance and sound reflex on postnatal day 20 (p = 0.0016 and p = 0.0068, respectively). Additionally, a statistically significant improvement in posture was observed in the Hypoxia-CBD group compared to the Hypoxia group alone (p = 0.0024). Our findings indicate that CBD possesses neuroprotective properties that significantly counteract the neurodevelopmental impairments induced by neonatal hypoxia in rats. This study not only supports the therapeutic potential of CBD in managing conditions characterized by neurodevelopmental challenges due to hypoxia but also underscores the necessity for further investigation into the specific molecular mechanisms driving CBD's neuroprotective effects. Further research is essential to explore CBD's clinical applications and its potential role in treating human neurodevelopmental disorders. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To probe into the efficacy of Taoren Honghua decoction combined with rehabilitation training in the treatment of patients with ischemic stroke and its effects on growth differentiation factor-15 (GDF-15), silent information regulatory factor 1 (SIRT1) and matrix metalloproteinase-9 (MMP-9) levels. METHODS: A total of 84 patients with ischemic stroke admitted into Dingzhou People’s Hospital from Feb. 2022 to Jul. 2023 were extracted to be divided into the combined group and training group through the random number table method, with 42 cases in each group. The training group was given rehabilitation training on the basis of routine treatment, while the combined group was treated with Taoren Honghua decoction on the basis of the training group. The clinical efficacy, National Institutes of Health stroke scale (NIHSS) score, Modified Barthel Index (MBI), serum inflammatory factors [interleukin (IL) 1β, IL-6 and tumor necrosis factor α (TNF-α)], oxidative stress related indicators [superoxide dismutase (SOD), malondialdehyde (MDA)], and serum levels of GDF-15, MMP-9 and SIRT1 of two groups were observed. RESULTS: The total clinical effective rate of the combined group was 95. 24% (40/42), significantly higher than 78. 57% (33/42) of the training group, with statistically significant differences (P <0. 05). Compared with before treatment, the NIHSS score, IL-1β, IL-6, TNF-α, MDA, GDF-15 and MMP-9 levels in both groups decreased significantly after treatment, the MBI score, SOD and SIRT1 levels increased significantly, with statistically significant differences (P<0. 05). Compared with the training group, the NIHSS score, IL-1β, IL-6, TNF-α, MDA, GDF-15 and MMP-9 levels in the combined group decreased significantly after treatment, the MBI score, SOD and SIRT1 levels increased significantly, with statistically significant differences (P <0. 05). CONCLUSIONS: The clinical efficacy of Taoren Honghua decoction combined with rehabilitation training in the treatment of patients with ischemic stroke is significant, which can effectively improve the neurological function and cerebral hypoxia ischemia-reperfusion injury, reduce inflammation and stress response, and significantly increase the SIRT1 levels and reduce the GDF-15 and MMP-9 levels [ABSTRACT FROM AUTHOR]

Xiaoying Zhou, Wenting Su, Quanwei Bao, Yu Cui, Xiaoxu Li, Yidong Yang, Chengzhong Yang, Chengyuan Wang, Li Jiao, Dewei Chen, and Jian Huang. Nitric oxide ameliorates the effects of hypoxia in mice by regulating oxygen transport by hemoglobin. High Alt Med Biol. 25:174–185, 2024.—Hypoxia is a common pathological and physiological phenomenon in ischemia, cancer, and strenuous exercise. Nitric oxide (NO) acts as an endothelium-derived relaxing factor in hypoxic vasodilation and serves as an allosteric regulator of hemoglobin (Hb). However, the ultimate effects of NO on the hematological system in vivo remain unknown, especially in extreme environmental hypoxia. Whether NO regulation of the structure of Hb improves oxygen transport remains unclear. Hence, we examined whether NO altered the oxygen affinity of Hb (Hb-O2 affinity) to protect extremely hypoxic mice. Mice were exposed to severe hypoxia with various concentrations of NO, and the survival time, exercise capacity, and other physical indexes were recorded. The survival time was prolonged in the 5 ppm NO (6.09 ± 1.29 minutes) and 10 ppm NO (6.39 ± 1.58 minutes) groups compared with the 0 ppm group (4.98 ± 1.23 minutes). Hypoxia of the brain was relieved, and the exercise exhaustion time was prolonged when mice inhaled 20 ppm NO (24.70 ± 6.87 minutes vs. 20.23 ± 6.51 minutes). In addition, the differences in arterial oxygen saturation (SO2%) (49.64 ± 7.29% vs. 42.90 ± 4.30%) and arteriovenous SO2% difference (25.14 ± 8.95% vs. 18.10 ± 6.90%) obviously increased. In ex vivo experiments, the oxygen equilibrium curve (OEC) left shifted as P50 decreased from 43.77 ± 2.49 mmHg (0 ppm NO) to 40.97 ± 1.40 mmHg (100 ppm NO) and 38.36 ± 2.78 mmHg (200 ppm NO). Furthermore, the Bohr effect of Hb was enhanced by the introduction of 200 ppm NO (−0.72 ± 0.062 vs.−0.65 ± 0.051), possibly allowing Hb to more easily offload oxygen in tissue at lower pH. The crystal structure reveals a greater distance between Asp94β-His146β in nitrosyl -Hb(NO-Hb), NO-HbβCSO93, and S-NitrosoHb(SNO-Hb) compared to tense Hb(T-Hb, 3.7 Å, 4.3 Å, and 5.8 Å respectively, versus 3.5 Å for T-Hb). Moreover, hydrogen bonds were less likely to form, representing a key limitation of relaxed Hb (R-Hb). Upon NO interaction with Hb, hydrogen bonds and salt bridges were less favored, facilitating relaxation. We speculated that NO ameliorated the effects of hypoxia in mice by promoting erythrocyte oxygen loading in the lung and offloading in tissues. [ABSTRACT FROM AUTHOR]

Brain oxygen deprivation causes morphological damage involved in the formation of serious pathological conditions such as stroke and cerebral palsy. Therapeutic methods for post-hypoxia/anoxia injuries are limited and still have deficiencies in terms of safety and efficacy. Recently, clinical studies of stroke have reported the use of drugs containing riboflavin for post-injury clinical rehabilitation, however, the effects of vitamin B2 on exposure to cerebral oxygen deprivation are not completely elucidated. This review aimed to investigate the potential antioxidant, anti-inflammatory and neuroprotective effects of riboflavin in cerebral hypoxia/anoxia. After a systematic search, 21 articles were selected, 8 preclinical and 12 clinical studies, and 1 translational study. Most preclinical studies used B2 alone in models of hypoxia in rodents, with doses of 1–20 mg/kg (in vivo) and 0.5–5 µM (in vitro). Together, these works suggested greater regulation of lipid peroxidation and apoptosis and an increase in neurotrophins, locomotion, and cognition after treatment. In contrast, several human studies have administered riboflavin (5 mg) in combination with other Krebs cycle metabolites, except one study, which used only B2 (20 mg). A reduction in lactic acidosis and recovery of sensorimotor functions was observed in children after treatment with B2, while adults and the elderly showed a reduction in infarct volume and cognitive rehabilitation. Based on findings from preclinical and clinical studies, we conclude that the use of riboflavin alone or in combination acts beneficially in correcting the underlying brain damage caused by hypoxia/anoxia and its inflammatory, oxidative, and behavioral impairments. [ABSTRACT FROM AUTHOR]

Purpose: Glial fibrillary acidic protein (GFAP) and neuroglobin (NGB) are important biomarkers of cerebral hypoxia. For this reason, an attempt was made to assess their concentrations in various time intervals and their impact on the severity of neurological symptoms and functional prognosis of thrombolytic ischemic stroke patients. Patients and Methods: The study involved 94 patients reporting to the emergency department of the Collegium Medicum University Hospital in Bydgoszcz within < 4.5 hours of the onset of stroke symptoms. GFAP and neuroglobin levels were measured in plasma at indicated times using a commercial ELISA kit. Results: Based on the data gathered, statistically significant differences were found between the concentration of biomarkers in stroke patients and the control group. The concentrations of both biomarkers, GFAP and NGB, were elevated in patients after ischemic stroke and the changes in their concentrations in the subsequent stages of stroke may suggest their prognostic value strictly dependent on time. NGB was determined on the 7th day, and mRS - after a year (0.35). GFAP measured after 24 h and on day 7 could be a promising biomarker of functional outcome after one year (cut-off point ≤ 0.231 ng/mL, sensitivity 75.0%, specificity 61.2%, cut off point ≤ 0.235 ng/mL, sensitivity 75.0%, specificity 73.9%, respectively) and the severity of the patient's neurological condition. At GFAP concentrations above 0.25 ng/mL, measured within 24 hours, a sharp increase in mortality was observed in stroke patients. In the case of NGB, at the time of stroke occurrence (14 ng/mL) and after 24 hours (10– 60 ng/mL). Differences in the concentrations of these biomarkers have been demonstrated in different stroke subtypes. Conclusion: NGB and GFAP are important biomarkers of ischemic brain injury and may also participate in predicting neurological outcomes. [ABSTRACT FROM AUTHOR]

Caffeine is one of the most commonly used drugs in intensive care to stimulate the respiratory control mechanisms of very preterm infants. Respiratory instability, due to the degree of immaturity at birth, results in apnea of prematurity (AOP), hyperoxic, hypoxic, and intermittent hypoxic episodes. Oxidative stress cannot be avoided as a direct reaction and leads to neurological developmental deficits and even a higher prevalence of respiratory diseases in the further development of premature infants. Due to the proven antioxidant effect of caffeine in early use, largely protective effects on clinical outcomes can be observed. This is also impressively observed in experimental studies of caffeine application in oxidative stress-adapted rodent models of damage to the developing brain and lungs. However, caffeine shows undesirable effects outside these oxygen toxicity injury models. This review shows the effects of caffeine in hyperoxic, hypoxic/hypoxic-ischemic, and intermittent hypoxic rodent injury models, but also the negative effects on the rodent organism when caffeine is administered without exogenous oxidative stress. The narrative analysis of caffeine benefits in cerebral and pulmonary preterm infant models supports protective caffeine use but should be given critical consideration when considering caffeine treatment beyond the recommended corrected gestational age. [ABSTRACT FROM AUTHOR]

Chronic vascular encephalopathy (CVE) is a frequent cause of vascular mild cognitive impairment and dementia, which significantly worsens the quality of life, especially in the elderly population. CVE is a result of chronic cerebral hypoperfusion, characterized by prolonged limited blood flow to the brain. This causes insufficient oxygenation of the brain leading to hypoxia. The latter can trigger a series of events associated with the development of oxidative/reductive stresses and neuroinflammation. Addressing the gap in knowledge regarding oxidative and reductive stresses in the development of vascular disorders and neuroinflammation can give a start to new directions of research in the context of CVE. In this review, we consider the hypoxiainduced molecular challenges involved in the pathophysiology of CVE, focusing on oxidative stress and neuroinflammation, which are combined in a vicious cycle of neurodegeneration. We also briefly describe therapeutic approaches to the treatment of CVE and outline the prospects for the use of sulforaphane, an isothiocyanate common in cruciferous plants, and vitamin D to break the vicious cycle and alleviate the cognitive impairments characteristic of patients with CVE. [ABSTRACT FROM AUTHOR]

Recently, the role of high-concentration oxygen therapy in cerebral hemorrhage has been extensively discussed. This review describes the research progress in high-concentration oxygen therapy after cerebral hemorrhage. High-concentration oxygen therapy can be classified into two treatment methods: hyperbaric and normobaric high-concentration oxygen therapy. Several studies have reported that high-concentration oxygen therapy uses the pathological mechanisms of secondary ischemia and hypoxia after cerebral hemorrhage as an entry point to improve cerebral oxygenation, metabolic rate, cerebral edema, intracranial pressure, and oxidative stress. We also elucidate the mechanisms by which molecules such as Hypoxia-inducible factor 1-alpha (HIF-1α), vascular endothelial growth factor, and erythropoietin (EPO) may play a role in oxygen therapy. Although people are concerned about the toxicity of hyperoxia, combined with relevant literature, the evidence discussed in this article suggests that as long as the duration, concentration, pressure, and treatment interval of patients with cerebral hemorrhage are properly understood and oxygen is administered within the treatment window, it can be effective to avoid hyperoxic oxygen toxicity. Combined with the latest research, we believe that high-concentration oxygen therapy plays an important positive role in injuries and outcomes after cerebral hemorrhage, and we recommend expanding the use of normal-pressure high-concentration oxygen therapy for cerebral hemorrhage. [ABSTRACT FROM AUTHOR]

This article comprehensively reviews how cerebral hypoxia impacts the physiological state of neurons and dendritic spines through a series of molecular changes, and explores the causal relationship between these changes and neuronal functional impairment. As a severe pathological condition, cerebral hypoxia can significantly alter the morphology and function of neurons and dendritic spines. Specifically, dendritic spines, being the critical structures for neurons to receive information, undergo changes such as a reduction in number and morphological abnormalities under hypoxic conditions. These alterations further affect synaptic function, leading to neurotransmission disorders. This article delves into the roles of molecular pathways like MAPK, AMPA receptors, NMDA receptors, and BDNF in the hypoxia-induced changes in neurons and dendritic spines, and outlines current treatment strategies. Neurons are particularly sensitive to cerebral hypoxia, with their apical dendrites being vulnerable to damage, thereby affecting cognitive function. Additionally, astrocytes and microglia play an indispensable role in protecting neuronal and synaptic structures, regulating their normal functions, and contributing to the repair process following injury. These studies not only contribute to understanding the pathogenesis of related neurological diseases but also provide important insights for developing novel therapeutic strategies. Future research should further focus on the dynamic changes in neurons and dendritic spines under hypoxic conditions and their intrinsic connections with cognitive function. [ABSTRACT FROM AUTHOR]

Background: The Brain Oxygen Optimization in Severe Traumatic Brain Injury Phase II randomized controlled trial used a tier-based management protocol based on brain tissue oxygen (PbtO2) and intracranial pressure (ICP) monitoring to reduce brain tissue hypoxia after severe traumatic brain injury. We performed a secondary analysis to explore the relationship between brain tissue hypoxia, blood pressure (BP), and interventions to improve cerebral perfusion pressure (CPP). We hypothesized that BP management below the lower limit of autoregulation would lead to cerebral hypoperfusion and brain tissue hypoxia that could be improved with hemodynamic augmentation. Methods: Of the 119 patients enrolled in the Brain Oxygen Optimization in Severe Traumatic Brain Injury Phase II trial, 55 patients had simultaneous recordings of arterial BP, ICP, and PbtO2. Autoregulatory function was measured by interrogating changes in ICP and PbtO2 in response to fluctuations in CPP using time-correlation analysis. The resulting autoregulatory indices (pressure reactivity index and oxygen reactivity index) were used to identify the "optimal" CPP and limits of autoregulation for each patient. Autoregulatory function and percent time with CPP outside personalized limits of autoregulation were calculated before, during, and after all interventions directed to optimize CPP. Results: Individualized limits of autoregulation were computed in 55 patients (mean age 38 years, mean monitoring time 92 h). We identified 35 episodes of brain tissue hypoxia (PbtO2 < 20 mm Hg) treated with CPP augmentation. Following each intervention, mean CPP increased from 73 ± 14 mm Hg to 79 ± 17 mm Hg (p = 0.15), and mean PbtO2 improved from 18.4 ± 5.6 mm Hg to 21.9 ± 5.6 mm Hg (p = 0.01), whereas autoregulatory function trended toward improvement (oxygen reactivity index 0.42 vs. 0.37, p = 0.14; pressure reactivity index 0.25 vs. 0.21, p = 0.2). Although optimal CPP and limits remained relatively unchanged, there was a significant decrease in the percent time with CPP below the lower limit of autoregulation in the 60 min after compared with before an intervention (11% vs. 23%, p = 0.05). Conclusions: Our analysis suggests that brain tissue hypoxia is associated with cerebral hypoperfusion characterized by increased time with CPP below the lower limit of autoregulation. Interventions to increase CPP appear to improve autoregulation. Further studies are needed to validate the importance of autoregulation as a modifiable variable with the potential to improve outcomes. [ABSTRACT FROM AUTHOR]

The mechanisms by which megadose sodium ascorbate improves clinical status in experimental sepsis is unclear. We determined its effects on cerebral perfusion, oxygenation, and temperature, and plasma levels of inflammatory biomarkers, nitrates, nitrites, and ascorbate in ovine Gram-negative sepsis. Sepsis was induced by i.v. infusion of live Escherichia coli for 31 h in unanaesthetised Merino ewes instrumented with a combination sensor in the frontal cerebral cortex to measure tissue perfusion, oxygenation, and temperature. Fluid resuscitation at 23 h was followed by i.v. megadose sodium ascorbate (0.5 g kg−1 over 30 min+0.5 g kg−1 h−1 for 6.5 h) or vehicle (n =6 per group). Norepinephrine was titrated to restore mean arterial pressure (MAP) to 70–80 mm Hg. At 23 h of sepsis, MAP (mean [ sem ]: 85 [2] to 64 [2] mm Hg) and plasma ascorbate (27 [2] to 15 [1] μM) decreased (both P <0.001). Cerebral ischaemia (901 [58] to 396 [40] units), hypoxia (34 [1] to 19 [3] mm Hg), and hyperthermia (39.5 [0.1]°C to 40.8 [0.1]°C) (all P <0.001) developed, accompanied by malaise and lethargy. Sodium ascorbate restored cerebral perfusion (703 [121] units], oxygenation (30 [2] mm Hg), temperature (39.2 [0.1]°C) (all P Treatment <0.05), and the behavioural state to normal. Sodium ascorbate slightly reduced the sepsis-induced increase in interleukin-6, returned VEGF-A to normal (both P GroupxTime <0.01), and increased plasma ascorbate (20 000 [300] μM; P Group <0.001). The effects of sodium ascorbate were not reproduced by equimolar sodium bicarbonate. Megadose sodium ascorbate rapidly reversed sepsis-induced cerebral ischaemia, hypoxia, hyperthermia, and sickness behaviour. These effects were not reproduced by an equimolar sodium load. [ABSTRACT FROM AUTHOR]

Background: Sex differences in oxidative stress-associated cognitive decline are influenced by sex hormone levels. Notably, oxidative stress-associated neuronal cell death can be exacerbated through testosterone signaling via membrane androgen receptor AR45, which is complexed with G protein Gaq within plasma membrane-associated lipid rafts. The objective of this study was to elucidate the impact of sex on the expression of AR45 and Gaq in brain regions associated with cognitive function, specifically hippocampus subregions and entorhinal cortex. Additionally, we investigated whether chronic intermittent hypoxia (CIH), an oxidative stressor with sex-specific effects, would modulate AR45 and Gaq expression in these brain regions. Methods: Adult male and female Sprague-Dawley rats were exposed to CIH or normoxia (room air) during their sleep phase for 14 days. We quantified AR45 and Gaq protein expression in various cognition-associated brain regions [dorsal hippocampal CA1, CA3, dentate gyrus (DG), and entorhinal cortex (ETC)] via western blotting. For comparisons, AR45 and Gaq protein expression were also assessed in brain regions outside the hippocampal-ETC circuit [thalamus (TH) and striatum (STR)]. Results: The highest AR45 levels were expressed in the hippocampal CA1 and DG while the lowest expression was observed in the extrahippocampal STR. The highest Gaq levels were expressed in the hippocampal-associated ETC while the lowest expression was observed in the extrahippocampal TH. Females expressed higher levels of AR45 in the hippocampal DG compared to males, while no sex differences in Gaq expression were observed regardless of brain region assessed. Moreover, there was no effect of CIH on AR45 or Gaq expression in any of the brain regions examined. AR45 expression was positively correlated with Gaq expression in the CA1, DG, ETC, TH, and STR in a sex-dependent manner. Conclusion: Our findings reveal enrichment of AR45 and Gaq protein expression within the hippocampal-ETC circuit, which is vulnerable to oxidative stress and neurodegeneration during cognitive decline. Nonetheless, CIH does not modulate the expression of AR45 or Gaq. Importantly, there are sex differences in AR45 expression and its association with Gaq expression in various brain regions, which may underlie sex-specific differences in cognitive and motor functionassociated declines with aging. [ABSTRACT FROM AUTHOR]

Stroke is a leading cause of death worldwide, yet current therapeutic strategies remain limited. Among the neuropathological events underlying this disease are multiple cell death signaling cascades, including autophagy. Recent interest has focused on developing agents that target molecules involved in autophagy to modulate this process under pathological conditions. This study aimed to analyze the role of autophagy in cell death induced by an in vitro ischemia–reperfusion (IR) model and to determine whether nitrones, known for their neuroprotective and antioxidant effects, could modulate this process. We focused on key proteins involved in different phases of autophagy: HIF-1α, BNIP3, and BECN1 for induction and nucleation, LC3 for elongation, and p62 for degradation. Our findings confirmed that the IR model promotes autophagy, initially via HIF-1α activation. Additionally, the neuroprotective effect of three of the selected synthetic nitrones (quinolylnitrones QN6 and QN23, and homo-bis-nitrone HBN6) partially derives from their antiautophagic properties, demonstrated by a downregulation of the expression of molecular markers involved in various phases of autophagy. In contrast, the neuroprotective power of cholesteronitrone ChN2 seems to derive from its promoting effects on the initial phases of autophagy, which could potentially help inhibit other forms of cell death. These results underscore the importance of autophagy modulation in neuroprotection, highlighting the potential of inhibiting prodeath autophagy and promoting prosurvival autophagy as promising therapeutic approaches in treating ischemic stroke clinically. [ABSTRACT FROM AUTHOR]

Prolonged disorder of consciousness (DoC) is a rising challenge. Pediatric data on diagnosis and prognosis of prolonged DoC were too limited and heterogeneous, making it difficult to define the natural course and evaluate the prognosis. The present study explored the emergence from the Minimally Conscious State (eMCS) incidence at different months postinjury drawing the natural course, and detected the predictors of the incidence in children with prolonged DoC. A hospital-based prospective cohort study was conducted. Kaplan–Meier curves, as well as univariate and multivariate COX regression analysis, were performed. The study enrolled 383 pediatric DoC individuals, including 220 males (57.4%), with an average age of 3.9 (1.9–7.3) years. The median duration between onset and rehabilitation is 30.0 (21.0–46.0) days. At enrollment, the ratio of vegetative state/unresponsive wakefulness syndrome (VS/WUS) to MCS is 78.9%–21.1%. Traumatic brain injury and infection are the major etiologies (36.8% and 37.1%, respectively), followed by hypoxia cerebral injury (12.3%). For children with prolonged DoC, the cumulative incidence of eMCS at months 3, 6, 12, and 24 was 0.510, 0.652, 0.731, 0.784 VS 0.290, 0.418, 0.539, 0.603 in the traumatic VS non-traumatic subgroup, respectively. For children in a persistent vegetative state (PVS), the cumulative incidence of emergence at months in 3, 6, 12, 24, 36 and 48 was testified as 0.439, 0.591, 0.683, 0.724, 0.743 and 0.743 in the traumatic subgroup, and 0.204, 0.349, 0.469, 0.534, 0.589 and 0.620 in the non-traumatic subgroup. Participants who exhibit any of the following four demographical and/or clinical characteristics—namely, older than 4 years at onset, accepted rehabilitation within 28 days of onset, remained MCS at enrollment, or with etiology of traumatic brain injuries—had a significantly positive outcome of consciousness recovery (eMCS). Moreover, both prolongation of the central somatosensory conductive time (CCT) (level 2) and absence of N20 (level 3) independently predict a negative outcome. In children with prolonged DoC, we found that 12 months postinjury was critical to eMCS, and a preferred timepoint to define chronic vegetative state (VS). The characteristics including age, etiology, time before rehabilitation, consciousness state, and SEP results were useful predictors of conscious recovery. Trial registration Registered 06/11/2018, the registration number is chiCTR1800019330 (chictr.org.cn). Registered prospectively. [ABSTRACT FROM AUTHOR]

Background: Acute hypobaric hypoxia-induced brain injury has been a challenge in the health management of mountaineers; therefore, new neuroprotective agents are urgently required. Meldonium, a well-known cardioprotective drug, has been reported to have neuroprotective effects. However, the relevant mechanisms have not been elucidated. We hypothesized that meldonium may play a potentially novel role in hypobaric hypoxia cerebral injury. Methods: We initially evaluated the neuroprotection efficacy of meldonium against acute hypoxia in mice and primary hippocampal neurons. The potential molecular targets of meldonium were screened using drug-target binding Huprot™ microarray chip and mass spectrometry analyses after which they were validated with surface plasmon resonance (SPR), molecular docking, and pull-down assay. The functional effects of such binding were explored through gene knockdown and overexpression. Results: The study clearly shows that pretreatment with meldonium rapidly attenuates neuronal pathological damage, cerebral blood flow changes, and mitochondrial damage and its cascade response to oxidative stress injury, thereby improving survival rates in mice brain and primary hippocampal neurons, revealing the remarkable pharmacological efficacy of meldonium in acute high-altitude brain injury. On the one hand, we confirmed that meldonium directly interacts with phosphoglycerate kinase 1 (PGK1) to promote its activity, which improved glycolysis and pyruvate metabolism to promote ATP production. On the other hand, meldonium also ameliorates mitochondrial damage by PGK1 translocating to mitochondria under acute hypoxia to regulate the activity of TNF receptor-associated protein 1 (TRAP1) molecular chaperones. Conclusion: These results further explain the mechanism of meldonium as an energy optimizer and provide a strategy for preventing acute hypobaric hypoxia brain injury at high altitudes. [ABSTRACT FROM AUTHOR]

Purpose: Applied Behavior Analysis (ABA) tact-training was provided to an adult with post-stroke anomic aphasia, with the main purposes to improve naming of pictures, with a possible generalization to another different setting, through telehealth sessions. Method: The Multiple probe experimental design across behaviors was used. Two sets of stimuli were used (SET 1 and SET 2), including 60 laminated photos, belonging to three different categories for each set. Procedure included the baseline, the intervention phases (face-to-face and telehealth sessions), and the follow-up (1 month after the end of a tact training). Results: For both, SET 1 and SET 2, the mastery criterion (80% correct stimulus tacts, for three consecutive times, simultaneously for all categories) was achieved. No increased percentage of correct picture tacts was found for untrained items. At follow-up, the patient provided 70 to 100% correct responses. For both SET 1 and SET 2, telehealth did not modify the correct response trends. Conclusion: The results of our study seem to suggest that specific tact-training procedures might be successfully carried out in adult and elderly people with post-stroke aphasia. It also appears necessary to arrange protocols providing telehealth sessions, with benefits for both families and the health system. [ABSTRACT FROM AUTHOR]

Objective Hydroxychloroquine (HCQ) has immunomodulatory, antithrombotic, cardiovascular, antimicrobial, and antineoplastic effects. In this study, we aimed to investigate the antiapoptotic and immunomodulator effects of intraperitoneal HCQ on hypoxic–ischemic (HI) injury in newborn rats. Study Design Wistar albino rats, 7 to 10 days old, were randomly divided into three groups: hypoxic–ischemic encephalopathy (HIE) group, HIE treated with HCQ group, and Sham group. Left common carotid artery ligation and hypoxia model were performed in HIE and HCQ groups. The HCQ group was treated with 80 mg/kg intraperitoneal HCQ every 24 hours for 3 days, while Sham and HIE groups were given physiological saline. After 72 hours, rats were decapitated and brain tissues were stained with hematoxylin and eosin, TUNEL, and IL-1β for histopathological grading and neuronal cell injury. Results Neuronal apoptosis was statistically lower in all neuroanatomical areas in the HCQ group compared with the HIE group. IL-1β-stained areas were similar in both HCQ and HIE groups but significantly higher compared with the Sham group. Histopathological grading scores were found to be lower in the HCQ group on the left parietal cortex and hippocampus region. Conclusion In this study, we have shown for the first time that HCQ treatment decreased apoptosis in HI newborn rat model in both hemispheres. HCQ may be a promising adjuvant therapy in neonatal HIE. Key Points HCQ decreased neuronal apoptosis in the ischemic penumbra of the rat brain. HCQ attenuates hypoxia–ischemia-induced brain injury in neonatal rats. HCQ has no anti-inflammatory effect on HI injury. [ABSTRACT FROM AUTHOR]

The decision to intubate a patient with acute hypoxemic respiratory failure who is not in apparent respiratory distress is one of the most difficult clinical decisions faced by intensivists. A conservative approach exposes patients to the dangers of hypoxemia, while a liberal approach exposes them to the dangers of inserting an endotracheal tube and invasive mechanical ventilation. To assist intensivists in this decision, investigators have used various thresholds of peripheral or arterial oxygen saturation, partial pressure of oxygen, partial pressure of oxygen-to-fraction of inspired oxygen ratio, and arterial oxygen content. In this review we will discuss how each of these oxygenation indices provides inaccurate information about the volume of oxygen transported in the arterial blood (convective oxygen delivery) or the pressure gradient driving oxygen from the capillaries to the cells (diffusive oxygen delivery). The decision to intubate hypoxemic patients is further complicated by our nescience of the critical point below which global and cerebral oxygen supply become delivery-dependent in the individual patient. Accordingly, intubation requires a nuanced understanding of oxygenation indexes. In this review, we will also discuss our approach to intubation based on clinical observations and physiologic principles. Specifically, we consider intubation when hypoxemic patients, who are neither in apparent respiratory distress nor in shock, become cognitively impaired suggesting emergent cerebral hypoxia. When deciding to intubate, we also consider additional factors including estimates of cardiac function, peripheral perfusion, arterial oxygen content and its determinants. It is not possible, however, to pick an oxygenation breakpoint below which the benefits of mechanical ventilation decidedly outweigh its hazards. It is futile to imagine that decision making about instituting mechanical ventilation in an individual patient can be condensed into an algorithm with absolute numbers at each nodal point. In sum, an algorithm cannot replace the presence of a physician well skilled in the art of clinical evaluation who has a deep understanding of pathophysiologic principles. [ABSTRACT FROM AUTHOR]

Why you should read this article: • To recognise the importance of speaking up in emergency care settings to enhance patient safety • To be aware of the barriers that can prevent nurses from speaking up • To enhance your knowledge of structured assessment and communication frameworks that can support nurses to speak up. Nurses’ competence and confidence in raising concerns with senior clinicians is integral to patient safety and the quality of patient care. If nurses do not speak up when needed it can contribute to incidences of failure to rescue. There are many barriers to nurses speaking up in busy emergency departments and complex major trauma patient cases. Assessment and communication tools such as the SBAR (situation, background, assessment, recommendation) approach and communication techniques such as graded assertiveness can help to overcome some of these barriers. This article uses a case study to discuss how nurses can respectfully but efficiently escalate their concerns to the trauma team leader. It describes barriers to nurses speaking up and tools that can support nurses to speak up, with a focus on graded assertiveness. [ABSTRACT FROM AUTHOR]

Background: The effect of two lung ventilation (TLV) with carbon dioxide artificial pneumothorax on cerebral desaturation and postoperative neurocognitive changes in elderly patients undergoing elective minimally invasive esophagectomy (MIE) is unclear. Objectives: The first aim of this study was to compare the effect of TLV and one lung ventilation (OLV) on cerebral desaturation. The second aim was to assess changes in early postoperative cognitive outcomes of two ventilation methods. Methods: This prospective, randomized, controlled trial enrolled patients 65 and older scheduled for MIE. Patients were randomly assigned (1:1) to TLV group or OLV group. The primary outcome was the incidence of cerebral desaturation events (CDE). Secondary outcomes were the cumulative area under the curve of desaturation for decreases in regional cerebral oxygen saturation (rSO2) values below 20% relative to the baseline value (AUC.20) and the incidence of delayed neurocognitive recovery. Results: Fifty-six patients were recruited between November 2019 and August 2020. TLV group had a lower incidence of CDE than OLV group [3 (10.71%) vs. 13 (48.14%), P = 0.002]. TLV group had a lower AUC.20 [0 (0–35.86) % min vs. 0 (0–0) % min, P = 0.007], and the incidence of delayed neurocognitive recovery [2 (7.4%) vs. 11 (40.7%), P = 0.009] than OLV group. Predictors of delayed neurocognitive recovery on postoperative day 7 were age (OR 1.676, 95% CI 1.122 to 2.505, P = 0.006) and AUC.20 (OR 1.059, 95% CI 1.025 to 1.094, P < 0.001). Conclusion: Compared to OLV, TLV had a lower incidence of CDE and delayed neurocognitive recovery in elderly patients undergoing MIE. The method of TLV combined with carbon dioxide artificial pneumothorax may be an option for these elderly patients. Chinese Clinical Trial Registry (identifier: ChiCTR1900027454). [ABSTRACT FROM AUTHOR]

Dynamic cerebral autoregulation (dCA) is the mechanism that describes how the brain maintains cerebral blood flow approximately constant in response to short‐term changes in arterial blood pressure. This is known to be impaired in many different pathological conditions, including ischaemic and haemorrhagic stroke, dementia and traumatic brain injury. Many different approaches have thus been used both to analyse and to quantify this mechanism in a range of healthy and diseased subjects, including data‐driven models (in both the time and the frequency domain) and biophysical models. However, despite the substantial body of work on both biophysical models and data‐driven models of dCA, there remains little work that links the two together. One of the reasons for this is proposed to be the discrepancies between the time constants that govern dCA in models and in experimental data. In this study, the processes that govern dCA are examined and it is proposed that the application of biophysical models remains limited due to a lack of understanding about the physical processes that are being modelled, partly due to the specific model formulation that has been most widely used (the equivalent electrical circuit). Based on the analysis presented here, it is proposed that the two most important time constants are arterial transit time and feedback time constant. It is therefore time to revisit equivalent electrical circuit models of dCA and to develop a more physiologically realistic alternative, one that can more easily be related to experimental data. Key points: Dynamic cerebral autoregulation is governed by two time constants.The first time constant is the arterial transit time, rather than the traditional 'RC' time constant widely used in previous models.This arterial transit time is approximately 1 s in the brain.The second time constant is the feedback time constant, which is less accurately known, although it is somewhat larger than the arterial transit time.The equivalent electrical circuit model of dynamic cerebral autoregulation should be replaced with a more physiologically representative model. [ABSTRACT FROM AUTHOR]

Brain hypoxia is associated with a wide range of physiological and clinical conditions. Although oxygen is an essential constituent of maintaining brain functions, our understanding of how specific brain cell types globally respond and adapt to decreasing oxygen conditions is incomplete. In this study, we exposed mouse primary neurons, astrocytes, and microglia to normoxia and two hypoxic conditions and obtained genome-wide transcriptional profiles of the treated cells. Analysis of differentially expressed genes under conditions of reduced oxygen revealed a canonical hypoxic response shared among different brain cell types. In addition, we observed a higher sensitivity of neurons to oxygen decline, and dissected cell type-specific biological processes affected by hypoxia. Importantly, this study establishes novel gene modules associated with brain cells responding to oxygen deprivation and reveals a state of profound stress incurred by hypoxia. [ABSTRACT FROM AUTHOR]

Most currently available wearable devices to noninvasively detect hypoxia use the spatially resolved spectroscopy (SRS) method to calculate cerebral tissue oxygen saturation (StO2). This study applies the single source—detector separation (SSDS) algorithm to calculate StO2. Near-infrared spectroscopy (NIRS) data were collected from 26 healthy adult volunteers during a breath-holding task using a wearable NIRS device, which included two source—detector separations (SDSs). These data were used to derive oxyhemoglobin (HbO) change and StO2. In the group analysis, both HbO change and StO2 exhibited significant change during a breath-holding task. Specifically, they initially decreased to minimums at around 10 s and then steadily increased to maximums, which were significantly greater than baseline levels, at 25–30 s (p-HbO < 0.001 and p-StO2 < 0.05). However, at an individual level, the SRS method failed to detect changes in cerebral StO2 in response to a short breath-holding task. Furthermore, the SSDS algorithm is more robust than the SRS method in quantifying change in cerebral StO2 in response to a breath-holding task. In conclusion, these findings have demonstrated the potential use of the SSDS algorithm in developing a miniaturized wearable biosensor to monitor cerebral StO2 and detect cerebral hypoxia. [ABSTRACT FROM AUTHOR]

The pathophysiological underpinnings of critically disrupted brain connectomes resulting in coma are poorly understood. Inflammation is potentially an important but still undervalued factor. Here, we present a first-in-human prospective study using the 18-kDa translocator protein (TSPO) radioligand 18F-DPA714 for PET imaging to allow in vivo neuroimmune activation quantification in patients with coma (n = 17) following either anoxia or traumatic brain injuries in comparison with age- and sex-matched controls. Our findings yielded novel evidence of an early inflammatory component predominantly located within key cortical and subcortical brain structures that are putatively implicated in consciousness emergence and maintenance after severe brain injury (i.e. mesocircuit and frontoparietal networks). We observed that traumatic and anoxic patients with coma have distinct neuroimmune activation profiles, both in terms of intensity and spatial distribution. Finally, we demonstrated that both the total amount and specific distribution of PET-measurable neuroinflammation within the brain mesocircuit were associated with the patient's recovery potential. We suggest that our results can be developed for use both as a new neuroprognostication tool and as a promising biometric to guide future clinical trials targeting glial activity very early after severe brain injury. [ABSTRACT FROM AUTHOR]

Despite a rapid increase in pediatric mortality rate from prescription and illicit opioids, there is limited research on the dose‐dependent impact of opioids on respiratory depression in children, the leading cause of opioid‐associated death. In this article, we extend a previously developed translational model to cover pediatric populations by incorporating age‐dependent pharmacokinetic, pharmacodynamic, and physiological changes compared to adults. Our model reproduced previous perioperative clinical findings that adults and children have similar risk of respiratory depression at the same plasma fentanyl concentration when specific endpoints (minute ventilation, CO2 tension in the blood) were used. However, our model points to a potential caveat that, in a perioperative setting, routine use of mechanical ventilation and supplemental oxygen maintained the blood and tissue oxygen partial pressures in patients and prevented the use of oxygen‐related endpoints to evaluate the consequences of respiratory depression. In a community setting when such oxygenation procedures are not immediately available, our model suggests that the higher oxygen demand and reduced cerebrovascular reactivity could make children more susceptible to severe hypoxemia and brain hypoxia, even with the same plasma fentanyl concentration as adults. Our work indicates that when developing intervention strategies to protect children from opioid overdose in a community setting, these pediatric‐specific factors may need to be considered. [ABSTRACT FROM AUTHOR]

Choroid plexus (CP) can be seen as a watchtower of the central nervous system (CNS) that actively regulates CNS homeostasis. A growing body of literature suggests that CP alterations are involved in the pathogenesis of multiple sclerosis (MS) but the underlying mechanisms remain elusive. CPs are enlarged and inflamed in relapsing-remitting (RRMS) but also in clinically isolated syndrome (CIS) and radiologically isolated syndrome (RIS) stages, far beyond MS diagnosis. Increases in the choroid plexus/total intracranial volume (CP/TIV) ratio have been robustly associated with increased lesion load, higher translocator protein (TSPO) uptake in normal-appearing white matter (NAWM) and thalami, as well as with higher annual relapse rate and disability progression in highly active RRMS individuals, but not in progressive MS. The CP/TIV ratio has only slightly been correlated with magnetic resonance imaging (MRI) findings (cortical or whole brain atrophy) and clinical outcomes (EDSS score) in progressive MS. Therefore, we suggest that plexus volumetric assessments should be mainly applied to the early disease stages of MS, whereas it should be taken into consideration with caution in progressive MS. In this review, we attempt to clarify the pathological significance of the temporal CP volume (CPV) changes in MS and highlight the pitfalls and limitations of CP volumetric analysis. [ABSTRACT FROM AUTHOR]

Objective The objective of this article was to correlate hypotension and cerebral saturation from near-infrared spectroscopy (cNIRS) in neonates on dopamine. Study Design Retrospective review of neonates receiving dopamine between August 2018 and 2019 was performed. Hypotension thresholds included mean arterial pressure (MAP) of postmenstrual age (PMA) ± 5 and 30 mm Hg and gestational age (GA) ± 5 mm Hg. Time below threshold MAP was compared with time with cerebral hypoxia (cNIRS <55%). Results Hypotension occurred 6 to 33% of the time on dopamine in 59 cases. Hypotension did not correlate with abnormal cNIRS overall, within PMA subgroups or by outcomes. Hypotensive periods with MAP < GA had fewer corresponding percent time with abnormal cNIRS events (3.7 ± 1.3%) compared with MAP < PMA (11.9 ± 4.9%, p < 0.003) or 30 mm Hg thresholds (12.2 ± 4.7%, p < 0.0001). In most premature infants, mean cNIRS values during hypotension were still within normal range (57 ± 6%). Conclusion cNIRS may be a more clinically relevant measure than MAP for the assessment of neonatal hypotension. Key Points Hypotension occurred 6 to 33% of the time on dopamine in 59 cases. Hypotension did not correlate with abnormal cNIRS overall, within PMA subgroups or by outcomes. MAP We found no cNIRS difference between IVH grades, mortality, average Hct, lactates, or urine output. cNIRS may be a more clinically relevant measure than MAP for the assessment of neonatal hypotension. [ABSTRACT FROM AUTHOR]

An APGAR score of 0 at 10 minutes is usually associated with high mortality and poor outcomes for the neonate, including lifelong deficits, severe hypoxic brain injury, and even death. Additionally, neonatal exposure to substances such as methamphetamines plays a role in developmental delays and meeting neurobehavioral milestones. In this case of a baby with APGARS of 0 at 1, 5, and 10 minutes, as well as in utero exposure to methamphetamines and complicated delivery, the risk of early demise was high. The aggressive resuscitation at birth and continued care in the NICU resulted in significantly less damage than what was expected. It is important to note that despite multiple factors contributing to the prediction of poor outcomes, early and attentive care of the newborn can play a vital role in recovery and a fighting chance. [ABSTRACT FROM AUTHOR]

This report delineates the intricate diagnostic journey and therapeutic conundrum presented by a 61-year-old male who exhibited atypical neurological deterioration shortly after lumbar fusion surgery, manifesting clinical and radiological features suggestive of pseudohypoxic encephalopathy, an entity characterized by symptoms mimicking cerebral hypoxia in the absence of a discernible hypoxic insult. Following an initially unremarkable recovery from an elaborate spinal surgery, the patient's postoperative condition was confounded by a perplexing decline in consciousness, unresponsive to conventional therapeutic interventions and devoid of clear etiological indicators on standard neuroimaging. The subsequent diagnostic odyssey unraveled a cerebrospinal fluid leak as the putative reason, positing a nuanced clinical paradigm wherein the cerebrospinal fluid leak engendered a state mimicking pseudohypoxic brain swelling. This report underscores the clinical challenges and emphasizes the need for an astute diagnostic approach in postoperative patients with unexplained neurological symptoms advocating for a comprehensive evaluation to identify underlying cerebrospinal fluid leaks and mitigate potential morbidity. [ABSTRACT FROM AUTHOR]

Preterm infants can face lasting neurodevelopmental challenges due to hypoxia-induced injury of the cerebral white matter. In this issue of Neuron , Ren et al. 1 identify microvascular pericytes as unexpected targets for growth hormone signaling, which enhances angiogenesis and remyelination after hypoxic injury in the developing mouse brain. Preterm infants can face lasting neurodevelopmental challenges due to hypoxia-induced injury of the cerebral white matter. In this issue of Neuron , Ren et al. identify microvascular pericytes as unexpected targets for growth hormone signaling, which enhances angiogenesis and remyelination after hypoxic injury in the developing mouse brain. [ABSTRACT FROM AUTHOR]

Purpose. Glioblastoma is the most aggressive primary brain tumor, characterized by its distinctive intratumoral hypoxia. Sequential preoperative examinations using fluorine-18-fluoromisonidazole (18F-FMISO) and fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) could depict the degree of glucose metabolism with hypoxic condition. However, molecular mechanism of glucose metabolism under hypoxia in glioblastoma has been unclear. The aim of this study was to identify the key molecules of hypoxic glucose metabolism. Methods. Using surgically obtained specimens, gene expressions associated with glucose metabolism were analyzed in patients with glioblastoma (n = 33) who underwent preoperative 18F-FMISO and 18F-FDG PET to identify affected molecules according to hypoxic condition. Tumor in vivo metabolic activities were semiquantitatively evaluated by lesion-normal tissue ratio (LNR). Protein expression was confirmed by immunofluorescence staining. To evaluate prognostic value, relationship between gene expression and overall survival was explored in another independent nonoverlapping clinical cohort (n = 17) and validated by The Cancer Genome Atlas (TCGA) database (n = 167). Results. Among the genes involving glucose metabolic pathway, mRNA expression of glucose-6-phosphatase 3 (G6PC3) correlated with 18F-FDG LNR (P = 0.03). In addition, G6PC3 mRNA expression in 18F-FMISO high-accumulated glioblastomas was significantly higher than that in 18F-FMISO low-accumulated glioblastomas (P < 0.01). Protein expression of G6PC3 was consistent with mRNA expression, which was confirmed by immunofluorescence analysis. These findings indicated that the G6PC3 expression might be facilitated by hypoxic condition in glioblastomas. Next, we investigated the clinical relevance of G6PC3 in terms of prognosis. Among the glioblastoma patients who received gross total resection, mRNA expressions of G6PC3 in the patients with poor prognosis (less than 1-year survival) were significantly higher than that in the patients who survive more than 3 years. Moreover, high mRNA expression of G6PC3 was associated with poor overall survival in glioblastoma, as validated by TCGA database. Conclusion. G6PC3 was affluently expressed in glioblastoma tissues with coincidentally high 18F-FDG and 18F-FMISO accumulation. Further, it might work as a prognostic biomarker of glioblastoma. Therefore, G6PC3 is a potential key molecule of glucose metabolism under hypoxia in glioblastoma. [ABSTRACT FROM AUTHOR]

Introduction: Severe acute global cerebral hypoxia can lead to significant disability in humans. Although different animal models have been described to study hypoxia, there is no endogenous model that considers hypoxia and its effect on the brain as an independent factor. Thus, we developed a minimally invasive rat model, which is based on the non-depolarizing muscle blocking agent rocuronium in anesthetized animals. This drug causes respiratory insufficiency by paralysis of the striated muscles. Methods: In this study, 14 rats underwent 12 min of hypoxemia with an oxygen saturation of approximately 60% measured by pulse oximetry; thereafter, animals obtained sugammadex to antagonize rocuronium immediately. Results: Compared to controls (14 rats, anesthesia only), hypoxic animals demonstrated significant morphological alterations in the hippocampus (cell decrease in the CA 1 region) and the cerebellum (Purkinje cell decrease), as well as significant changes in hypoxia markers in blood (Hif2α, Il1β, Tgf1β, Tnfα, S100b, cspg2, neuron-specific enolase), hippocampus (Il1β, Tnfα, S100b, cspg2, NSE), and cerebellum (Hif1α, Tnfα, S100b, cspg2, NSE). Effects were more pronounced in females than in males. Discussion: Consequently, this model is suitable to induce hypoxemia with consecutive global cerebral hypoxia. As significant morphological and biochemical changes were proven, it can be used to investigate therapeutic and preventive drugs for global cerebral hypoxia. [ABSTRACT FROM AUTHOR]

This review advances an understanding of several dementias, based on four premises. One is that capillary hemorrhage is prominent in the pathogenesis of the dementias considered (dementia pugilistica, chronic traumatic encephalopathy, traumatic brain damage, Alzheimer's disease). The second premise is that hemorrhage introduces four neurotoxic factors into brain tissue: hypoxia of the tissue that has lost its blood supply, hemoglobin and its breakdown products, excitotoxic levels of glutamate, and opportunistic pathogens that can infect brain cells and induce a cytotoxic immune response. The third premise is that where organisms evolve molecules that are toxic to itself, like the neurotoxicity ascribed to hemoglobin, amyloid- (A), and glutamate, there must be some role for the molecule that gives the organism a selection advantage. The fourth is the known survival-advantage roles of hemoglobin (oxygen transport), of A (neurotrophic, synaptotrophic, detoxification of heme, protective against pathogens) and of glutamate (a major neurotransmitter). From these premises, we propose 1) that the brain has evolved a multi-factor response to intracerebral hemorrhage, which includes the expression of several protective molecules, including haptoglobin, hemopexin and A; and 2) that it is logical, given these premises, to posit that the four neurotoxic factors set out above, which are introduced into the brain by hemorrhage, drive the progression of the capillary-hemorrhage dementias. In this view, A expressed at the loci of neuronal death in these dementias functions not as a toxin but as a first responder, mitigating the toxicity of hemoglobin and the infection of the brain by opportunistic pathogens. [ABSTRACT FROM AUTHOR]

Background: Cardiac arrest (CA) is a sudden event that is often characterized by hypoxic-ischemic brain injury (HIBI), leading to significant mortality and long-term disability. Brain tissue oxygenation (PbtO2) is an invasive tool for monitoring brain oxygen tension, but it is not routinely used in patients with CA because of the invasiveness and the absence of high-quality data on its effect on outcome. We conducted a systematic review of experimental and clinical evidence to understand the role of PbtO2 in monitoring brain oxygenation in HIBI after CA and the effect of targeted PbtO2 therapy on outcomes. Methods: The search was conducted using four search engines (PubMed, Scopus, Embase, and Cochrane), using the Boolean operator to combine mesh terms such as PbtO2, CA, and HIBI. Results: Among 1,077 records, 22 studies were included (16 experimental studies and six clinical studies). In experimental studies, PbtO2 was mainly adopted to assess the impact of gas exchanges, drugs, or systemic maneuvers on brain oxygenation. In human studies, PbtO2 was rarely used to monitor the brain oxygen tension in patients with CA and HIBI. PbtO2 values had no clear association with patients' outcomes, but in the experimental studies, brain tissue hypoxia was associated with increased inflammation and neuronal damage. Conclusions: Further studies are needed to validate the effect and the threshold of PbtO2 associated with outcome in patients with CA, as well as to understand the physiological mechanisms influencing PbtO2 induced by gas exchanges, drug administration, and changes in body positioning after CA. [ABSTRACT FROM AUTHOR]

Exposure to hypoxic conditions can result in significant brain damage, such as that experienced during an ischemic stroke. Thus, finding ways to mitigate ischemia/hypoxia-induced brain tissue damage is a critical issue that needs addressing. HH-A, a derivative of honokiol, has demonstrated potent pharmacological activities and medicinal properties in treating brain ischemia/reperfusion injury. However, its effect on anti-hypoxic responses during stroke remains largely unexplored. In the present study, we subjected male Sprague-Dawley rats to 24 h of hypoxia (oxygen content at 11%) or to 7 d of permanent middle cerebral artery occlusion. We discovered that both 1 mg/kg (i.v.) and 40 mg/kg (i.g.) of HH-A elevated arterial oxygen saturation after 24 h of hypoxia and significantly reduced the infarct volume after 7 d of ischemia. Furthermore, fluorescence staining with hypoxyprobe-1 indicated that HH-A significantly mitigated the severity of hypoxia in brain tissue. Hematoxylin and eosin staining, along with neuronal nuclei immunofluorescent staining, further revealed that HH-A curbed the death of brain cells. To identify potential protein partners of HH-A, we used a molecular fishing approach based on surface plasmon resonance technology. A high binding affinity was detected between HH-A and the hemoglobin subunit beta, with an estimated binding free energy of -8.7 kcal/mol. These findings suggested that HH-A was capable of enhancing hypoxia tolerance and alleviating brain injury caused by ischemia. [ABSTRACT FROM AUTHOR]

Background: Cerebral ischemia–hypoxia leads to excitotoxicity‐mediated neuronal damage and cognitive dysfunction, especially in the elderly. Excessive intracellular [Cl−]i accumulation weakens γ‐aminobutyric acid (GABA) compensatory effects. Sub‐anesthetic dose of propofol protected the brain against ischemia–hypoxia, which was abolished by blocking Cl− efflux transporter K+/Cl− cotransporter 2 (KCC2). We aimed to determine whether low‐dose anesthetic combined with [Cl−]i regulators could restore the compensatory GABAergic system and improve cognitive function. Methods: Chronic cerebral hypoxia (CCH) model was established by bilateral carotid artery ligation in aged rats. Sub‐dose of anesthetics (propofol and sevoflurane) with or without KCC2 agonist N‐ethylmaleimide (NEM) or Na+/K+/Cl− cotransporter 1 (NKCC1) antagonist bumetanide (BTN) was administered systemically 30 days post‐surgery. Primary rat hippocampal neuronal cultures were subjected to hypoxic injury with or without drug treatment. Memory function, hippocampal neuronal survival, GABAergic system functioning, and brain‐derived neurotrophic factor (BDNF) expressions were evaluated. Results: Sub‐anesthetic dose of combined propofol (1.2 μg mL−1) and sevoflurane [0.7 MAC (minimum alveolar concentration)] did not aggravate the hypoxic brain injury in rats or cell damage in neuronal cultures. Adding either BTN or NEM protected against hypoxic injury, associated with improved cognitive function in vivo, less intracellular accumulation of [Cl−]i, reduced cell death, restored GABAergic compensation, and increased BDNF expression both in vivo and in vitro. Conclusion: Sub‐anesthetic dose of propofol and sevoflurane is a recommended anesthesia regimen in at‐risk patients. Restoration of [Cl−]i homeostasis and GABAergic could further reduce the brain damage caused by ischemia–hypoxia. [ABSTRACT FROM AUTHOR]

The levels and potential role of prolactin (PRL) in the brain under conditions of acute systemic hypoxia were examined, focusing on the accumulation of PRL in cerebrospinal fluid (CSF) and its effects on neuronal activity and injury. The amount of PRL in the brain was investigated using brain tissues from forensic autopsy cases. We counted the number of neurites that formed in human primary neurons (HNs) after the addition of PRL. Furthermore, HNs supplemented with PRL or triiodothyronine (T3) were exposed to hypoxic conditions, and the dead cells were counted. The results showed correlations between brain PRL and CSF PRL levels. Additionally, PRL accumulation in the brain was observed in cases of asphyxia. In vitro experimental findings indicated increased neurite formation in the HNs treated with PRL. Moreover, both PRL and T3 demonstrated neuroprotective effects against hypoxia-induced neuronal cell death, with PRL showing stronger neuroprotective potential than T3. These results suggest that PRL accumulates in the brain during hypoxia, potentially influences neuronal activity, and exhibits neuroprotective properties against hypoxia-induced neuronal injury. [ABSTRACT FROM AUTHOR]

Objectives: Literature on invasive neuromonitoring and bilateral decompressive craniectomies (BDC) in patients with refractory status epilepticus (RSE)-mediated hypoxic-ischemic brain injury (HIBI) is limited. Neuromonitoring can guide decision making and treatment escalation. Methods and results: We report a case of a 17  years-old male who was admitted to our hospital’s intensive care unit for RSE. HIBI was detected on neuroimaging on this patient’s second day of admission after he developed central diabetes insipidus (DI). Invasive neuromonitoring revealed raised intracranial pressure (ICP) and brain hypoxia as measured by reduced brain tissue oxygen tension (PbtO2). Treatments were escalated in a tiered fashion, including administration of hyperosmolar agents, analgesics, sedatives, and a neuromuscular blocking drug. Eventually, BDC was performed as a salvage therapy as a means of controlling refractory ICP crisis in the setting of diffuse cerebral edema (DCE) following HIBI. Discussion: SE-mediated HIBI can result in refractory ICP crisis. Neuromonitoring can help identify secondary brain injury (SBI), guide treatment strategies, including surgical interventions, and may lead to better outcomes. [ABSTRACT FROM AUTHOR]

Summary: Cardiac surgery requiring cardiopulmonary bypass is associated with postoperative acute kidney injury and neurocognitive disorders, including delirium. Intra‐operative inflammation and/or impaired tissue perfusion/oxygenation are thought to be contributors to these outcomes. It has been hypothesised that these problems may be ameliorated by the highly selective α2‐agonist, dexmedetomidine. We tested the effects of dexmedetomidine on renal and cerebral microcirculatory tissue perfusion, oxygenation and histology in a clinically relevant ovine model. Sixteen sheep were studied while conscious, after induction of anaesthesia and during 2 h of cardiopulmonary bypass. Eight sheep were allocated randomly to receive an intravenous infusion of dexmedetomidine (0.4–0.8 μg.kg‐1.h‐1) from induction of anaesthesia to the end of cardiopulmonary bypass, and eight to receive an equivalent volume of matched placebo (0.9% sodium chloride). Commencement of cardiopulmonary bypass decreased renal medullary tissue oxygenation in the placebo group (mean (95%CI) 5.96 (4.24–7.23) to 1.56 (0.84–2.09) kPa, p = 0.001), with similar hypoxic levels observed in the dexmedetomidine group (6.33 (5.33–7.07) to 1.51 (0.33–2.39) kPa, p = 0.002). While no differences in kidney function (i.e. reduced creatinine clearance) were evident, a greater incidence of histological renal tubular injury was observed in sheep receiving dexmedetomidine (7/8 sheep) compared with placebo (2/8 sheep), p = 0.041. Graded on a semi‐quantitative scale (0–3), median (IQR [range]) severity of histological renal tubular injury was higher in the dexmedetomidine group compared with placebo (1.5 (1–2 [0–3]) vs. 0 (0–0.3 [0–1]) respectively, p = 0.013). There was no difference in cerebral tissue microglial activation (neuroinflammation) between the groups. Dexmedetomidine did not reduce renal medullary hypoxia or cerebral neuroinflammation in sheep undergoing cardiopulmonary bypass. [ABSTRACT FROM AUTHOR]