Isoflurane preconditioning protects astrocytes from oxygen and glucose deprivation independent of innate cell sex

Evaluation of severe traumatic brain injury referrals to the National Tertiary Neurosurgical Centre in the Republic of Ireland

BACKGROUND

Transfer of all severe TBI patients to a neurosurgical unit (NSU) has been advocated irrespective of levels of complexity and prognostic factors. Previous publications have suggested that only 50% of severe TBI patients in Ireland were managed in NSUs.

AIMS

This study aims to audit severe TBI referrals to the National Neurosurgical Centre, to evaluate reasons for nonacceptance, assess for differences in the transferred and not transferred cohorts and to analyse observed and expected mortality rates.

METHODS

Data on all patients with TBI referred in 2021 were prospectively collected using an electronic referral system. Patients with severe TBI (GCS ≤ 8 and AIS ≥ 3) were included and dichotomised into transferred and not transferred cohorts.

RESULTS

Of 118 patients referred with severe TBI, 45 patients (38.1%) were transferred to the neurosurgical centre. Patients in the transferred cohort were significantly younger (p < 0.001), had a higher GCS score (p < 0.001) and a lower proportion of bilaterally unreactive pupils (p < 0.001) compared to the not transferred cohort. 93% (68/73) of those not transferred were either >65 years old, or had bilaterally unreactive pupils, or both. Based on the IMPACT model, the observed to expected mortality ratios in the transferred and not transferred cohorts were 0.65 (95% CI 0.25-1.05) and 0.88 (95% CI 0.65-1.11) respectively.

CONCLUSION

The observed mortality rate for severe TBI in Ireland was similar to or better than expected mortality rates when adjusted for important prognostic factors. 93% of severe TBI patients not transferred to a neurosurgical centre were either elderly or had bilaterally unreactive pupils or both. These patients have an extremely poor prognosis and recommendation for transfer cannot be made based on current available evidence.

Sex differences in recovery of motor function in a rhesus monkey model of cortical injury

BACKGROUND

Stroke disproportionately affects men and women, with women over 65 years experiencing increased severity of impairment and higher mortality rates than men. Human studies have explored risk factors that contribute to these differences, but additional research is needed to investigate how sex differences affect functional recovery and hence the severity of impairment. In the present study, we used our rhesus monkey model of cortical injury and fine motor impairment to compare sex differences in the rate and degree of motor recovery following this injury.

METHODS

Aged male and female rhesus monkeys were trained on a task of fine motor function of the hand before undergoing surgery to produce a cortical lesion limited to the hand area representation of the primary motor cortex. Post-operative testing began two weeks after the surgery and continued for 12 weeks. All trials were video recorded and latency to retrieve a reward was quantitatively measured to assess the trajectory of post-operative response latency and grasp pattern compared to pre-operative levels.

RESULTS

Postmortem analysis showed no differences in lesion volume between male and female monkeys. However, female monkeys returned to their pre-operative latency and grasp patterns significantly faster than males.

CONCLUSIONS

These findings demonstrate the need for additional studies to further investigate the role of estrogens and other sex hormones that may differentially affect recovery outcomes in the primate brain.

Comparing the Outcomes of Early and Late Tracheostomy in Severe Traumatic Brain Injury Patient

Background

Patients with severe traumatic brain injury (TBI) were expected to have poor Glasgow Coma Scale (GCS) recovery and prolonged intubation. Therefore, an early tracheostomy procedure was indicated for all severe TBI. In view of growing concern regarding the safety and outcome of early tracheostomy on these patients, it was deemed valid and needed to be addressed.

Methods

This study was conducted to compare the outcomes of early and late tracheostomies in severe TBI. Only severe TBI patients who were admitted to the Neurosurgery High Dependency Unit (NHDU), Hospital Sultanah Aminah (HSA), Johor Bahru, Johor, Malaysia and who had underwent a tracheostomy were recruited. Three main outcomes noted: duration on ventilation, length of NHDU stay and rate of ventilator associated pneumonia (VAP).

Results

Out of 155 patients, 72 (46.5%) were in early tracheostomy group (ETG) and 83 (53.5%) were in late tracheostomy group (LTG). The majority of the participants, 95 (61.3%) were ethnic Malays. The mean duration on ventilator use was 2.65 days (1.57) for ETG and 5.63 days (2.35) for LTG. While, mean NHDU stay was 4.75 days (1.98) for ETG and 9.77 days (2.70) for LTG. Upon independent t-test, early duration of tracheostomies had shown significant outcome in reducing length of NHDU stay, (P < 0.001) and had shortening participants’ time on mechanical ventilator (P < 0.001). Then, based on forward multiple logistic regression test, there were significant association between comorbid (P = 0.003) and tracheostomy (P = 0.020) towards presence of VAP when adjusted for other variables.

Conclusion

In this study it was found that early tracheostomy was significant in shortening the duration on ventilator, reducing the length of NHDU stay and reducing the rate of VAP.

Primary versus early secondary referral to a specialized neurotrauma center in patients with moderate/severe traumatic brain injury: a CENTER TBI study

Background

Prehospital care for patients with traumatic brain injury (TBI) varies with some emergency medical systems recommending direct transport of patients with moderate to severe TBI to hospitals with specialist neurotrauma care (SNCs). The aim of this study is to assess variation in levels of early secondary referral within European SNCs and to compare the outcomes of directly admitted and secondarily transferred patients.

Methods

Patients with moderate and severe TBI (Glasgow Coma Scale < 13) from the prospective European CENTER-TBI study were included in this study. All participating hospitals were specialist neuroscience centers. First, adjusted between-country differences were analysed using random effects logistic regression where early secondary referral was the dependent variable, and a random intercept for country was included. Second, the adjusted effect of early secondary referral on survival to hospital discharge and functional outcome [6 months Glasgow Outcome Scale Extended (GOSE)] was estimated using logistic and ordinal mixed effects models, respectively.

Results

A total of 1347 moderate/severe TBI patients from 53 SNCs in 18 European countries were included. Of these 1347 patients, 195 (14.5%) were admitted after early secondary referral. Secondarily referred moderate/severe TBI patients presented more often with a CT abnormality: mass lesion (52% vs. 34%), midline shift (54% vs. 36%) and acute subdural hematoma (77% vs. 65%). After adjusting for case-mix, there was a large European variation in early secondary referral, with a median OR of 1.69 between countries. Early secondary referral was not associated with functional outcome (adjusted OR 1.07, 95% CI 0.78–1.69), nor with survival at discharge (1.05, 0.58–1.90).

Conclusions

Across Europe, substantial practice variation exists in the proportion of secondarily referred TBI patients at SNCs that is not explained by case mix. Within SNCs early secondary referral does not seem to impact functional outcome and survival after stabilisation in a non-specialised hospital. Future research should identify which patients with TBI truly benefit from direct transportation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13049-021-00930-1.

The protective effect of trilobatin against isoflurane-induced neurotoxicity in mouse hippocampal neuronal HT22 cells involves the Nrf2/ARE pathway

Long-term exposure to isoflurane may induce long-term developmental neurotoxicity and cognitive impairments in the neonatal brains. Trilobatin, a leaf extract from the Chinese traditional sweet tea Lithocarpus polystachyus Rehd, possesses various biological properties including anti-inflammatory and anti-oxidant properties. Our study aimed to explore the neuroprotective effect of trilobatin on isoflurane-induced neurotoxicity in mouse hippocampal neuronal HT22 cells. The effects of trilobatin on cell viability, LDH release, apoptosis, and caspase-3/7 activity in isoflurane-induced HT22 cells were explored by CCK-8, LDH release assay, flow cytometry analysis, and caspase-3/7 activity assay, respectively. Oxidative stress was evaluated by measuring the levels of reactive oxygen species (ROS) and malonyldialdehyde (MDA) and activities of superoxide dismutase (SOD) and catalase (CAT). The expression of nuclear erythroid-2 related factor 2 (Nrf2), nuclear Nrf2, heme oxygenase-1 (HO-1), and NAD(P)H: quinone oxidoreductase 1 (NQO1) was determined by western blot and qRT-PCR. Results suggested that exposure to isoflurane significantly reduced cell viability and increased LDH release, apoptotic rate and caspase-3/7 activity in HT22 cells, which were abolished by trilobatin. Trilobatin reversed isoflurane-induced increase of ROS and MDA levels and reduction of SOD and CAT activities in HT22 cells. Additionally, trilobatin promoted the nuclear translocation of Nrf2 as well as the mRNA and protein expression of HO-1 and NQO1 in HT22 cells exposed to isoflurane. Nrf2 knockdown attenuated the effects of trilobatin on isoflurane-induced viability reduction, LDH release, apoptosis, and oxidative stress in HT22 cells. Overall, trilobatin protected HT22 cells against isoflurane-induced neurotoxicity via activating the Nrf2/antioxidant response element (ARE) pathway.

Neuroprotection of miR-214 against isoflurane-induced neurotoxicity involves the PTEN/PI3K/Akt pathway in human neuroblastoma cell line SH-SY5Y

Isoflurane, one of the commonly used inhalation anesthetics worldwide in clinical practice, may generate substantial risks of neurotoxicity in the developing brains. The present study aimed to illustrate the effects and underlying mechanisms of miR-214 on isoflurane-induced neurotoxicity in human neuroblastoma cell line SH-SY5Y. SH-SY5Y cells were transfected with miR-214 or miR-con alone or in combination with pcDNA empty vector or pcDNA-PTEN in the presence of 3% isoflurane and incubated for 48 h. Cell viability, lactate dehydrogenase (LDH) release, apoptosis, and caspase-3/7 activity were evaluated using CCK-8, LDH release assay, flow cytometry analysis, and caspase-3/7 activity assay, respectively. The superoxide dismutase (SOD), glutathione (GSH), and malondialdehyde (MDA) activities were measured using commercial kits. miR-214 expression and alterations of the phosphatase and tensin homolog (PTEN)/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway were detected by qRT-PCR and Western blot, respectively. The interaction between miR-214 and PTEN was explored by luciferase reporter assay. We found that isoflurane exposure induced neurotoxicity in SH-SY5Y cells, as evidenced by the reduced cell viability, increased LDH release, apoptotic rate, caspase-3/7 activity, and oxidative stress levels. Moreover, isoflurane exposure decreased the expression of miR-214 and affected the PTEN/PI3K/Akt pathway in SH-SY5Y cells. miR-214 overexpression significantly suppressed isoflurane-induced viability reduction, LDH release, apoptosis and oxidative stress, as well as inactivation of the PI3K/Akt pathway in SH-SY5Y cells. Interestingly, PTEN was identified as a target of miR-214. Moreover, PTEN upregulation blocked the effects of miR-214 on isoflurane-induced neurotoxicity in SH-SY5Y cells. In conclusion, miR-214 protected against isoflurane-induced neurotoxicity in SH-SY5Y cells via regulation of PI3K/Akt pathway by targeting PTEN, contributing to better understanding the underlying mechanisms of anesthetics-induce neurotoxicity.

Teleneurosurgery: Outcome of Mild Head Injury Patients Managed in Non-Neurosurgical Centre in the State of Johor

Background

With teleneurosurgery, more patients with head injury are managed in the primary hospital under the care of general surgical unit. Growing concerns regarding the safety and outcome of these patients are valid and need to be addressed.

Method

This study is to evaluate the outcome of patients with mild head injury which were managed in non-neurosurgical centres with the help of teleneurosurgery. The study recruits samples from five primary hospitals utilising teleneurosurgery for neurosurgical consultations in managing mild head injury cases in Johor state. Two main outcomes were noted; favourable and unfavourable, with a follow up review of the Glasgow Outcome Scale (GOS) at 3 and 6 months.

Results

Total of 359 samples were recruited with a total of 11 (3.06%) patients have an unfavourable. no significant difference in GOS at 3 and 6 months for patient in the unfavourable group (P = 0.368).

Conclusion

In this study we have found no significant factors affecting the outcome of mild head injury patients managed in non-neurosurgical centres in Johor state using the help of teleneurosurgery.

The Effect of MPP+ on the Viability of Primary Cortical Astrocytes Isolated from Female and Male Wistar Rats of Different Ages

Although age is known to be the main risk for developing chronic and neurodegenerative diseases, those illnesses have a different prevalence depending on the sex. It has been questioned whether genetic and hormonal differences are preserved in primary cultures from individuals of different genders. Therefore, here we studied the susceptibility of astrocytes, obtained from female and male Wistar rats of different ages (newborn, 9 and 24 months-old), to the well-known toxin MPP+ after 2 weeks in vitro, at different concentrations and exposure times. Our results showed that there are no variances due to gender, but that there are important differences associated to age in terms of the viability against this toxin.

Ischemic stroke across sexes: What is the status quo?

Stroke prevalence is expected to increase in the next decades due to the aging of the Western population. Ischemic stroke (IS) shows an age- and sex-dependent distribution in which men represent the most affected population within 65 years of age, being passed by post-menopausal women in older age groups. Furthermore, a sexual dimorphism concerning risk factors, presentation and treatment of IS has been widely recognized. In order to address these phenomena, a number of issue have been raised involving both socio-economical and biological factors. The latter can be either dependent on sex hormones or due to intrinsic factors. Although women have poorer outcomes and are more likely to die after a cerebrovascular event, they are still underrepresented in clinical trials and this is mirrored by the lack of sex-tailored therapies. A greater effort is needed in the future to ensure improved treatment and quality of life to both sexes.

Ischemic stroke across sexes: what is the status quo?

Stroke prevalence is expected to increase in the next decades due to the aging of the Western population. Ischemic stroke (IS) shows an age- and sex-dependent distribution in which men represent the most affected population within 65 years of age, being passed by post-menopausal women in older age groups. Furthermore, a sexual dimorphism concerning risk factors, presentation and treatment of IS has been widely recognized. In order to address these phenomena, a number of issue have been raised involving both socio-economical and biological factors. The latter can be either dependent on sex hormones or due to intrinsic factors. Although women have poorer outcomes and are more likely to die after a cerebrovascular event, they are still underrepresented in clinical trials and this is mirrored by the lack of sex-tailored therapies. A greater effort is needed in the future to ensure improved treatment and quality of life to both sexes.

Prehospital and Intrahospital Temporal Intervals in Patients Requiring Emergent Trauma Craniotomy. A 6-Year Observational Study in a Level 1 Trauma Center

OBJECTIVE

According to level 2 evidence, earlier evacuation of acute subdural or epidural hematomas necessitating surgery is associated with better outcome. Hence, guidelines recommend performing these procedures immediately. Literature on the extent and causes of prehospital and intrahospital intervals in patients with trauma requiring emergent craniotomies is almost completely lacking. Studies delineating and refining the interval before thrombolytic agent administration in ischemic stroke have dramatically reduced the door-to-needle time. A similar exercise for trauma-to-decompression time might result in comparable reductions. We aim to map intervals in emergent trauma craniotomies in our level 1 trauma center, screen for associated factors, and propose possible ways to reduce these intervals.

METHODS

We analyzed patients who were primarily referred (1R; n = 45) and secondarily referred (after computed tomography imaging in a community hospital [2R; n = 22]) to our emergency department (ED) and underwent emergent trauma craniotomies between 2010 and 2016.

RESULTS

Median prehospital interval (between emergency call and arrival at the ED) was 42 minutes for 1R patients. Median intrahospital interval (between initial ED arrival and skin incision [SI]) was 140 minutes and 268 minutes for 1R and 2R patients, respectively. In 1R patients, ED-SI interval was positively correlated with Glasgow Coma Scale score (ρ=.49; P < 0.001), but not with age, time of ED arrival, or extended Glasgow Outcome Scale score at 6 months. Based on outlier analysis, we propose prehospital and intrahospital measures to improve performance.

CONCLUSIONS

This is the first report on emergency call-SI interval in emergent trauma craniotomy, with a median of 174 minutes and >297 minutes for 1R and 2R patients, respectively, in our center.

Establishment of mouse neuron and microglial cell co-cultured models and its action mechanism

OBJECTIVE

The objective of this study is to establish a co-culture model of mouse neurons and microglial cells, and to analyze the mechanism of action of oxygen glucose deprivation (OGD) and transient oxygen glucose deprivation (tOGD) preconditioning cell models.

RESULTS

Mouse primary neurons and BV2 microglial cells were successfully cultured, and the OGD and tOGD models were also established. In the co-culture of mouse primary neurons and microglial cells, the cell number of tOGD mouse neurons and microglial cells was larger than the OGD cell number, observed by a microscope. CCK-8 assay result showed that at 1h after treatment, the OD value in the control group is lower compared to all the other three groups (P < 0.05). The treatment group exhibited the highest OD value among the four groups. The results observed at 5h were consistent with the results at 1 h. Flow cytometry results showed that at 1h after treatment the apoptosis percentages is higher in the control group compared to other three groups (P < 0.05).

MATERIALS AND METHODS

Mouse brain tissues were collected and primary neurons cells were cultured. In the meantime mouse BV2 microglia cells were cultured. Two types of cells were co-cultured, and OGD and tOGD cell models were established. There were four groups in the experiment: control group (OGD), treatment group (tOGD+OGD), placebo group (tOGD+OGD+saline) and minocycline intervention group (tOGD+OGD+minocycline). CCK-8 kit was used to detect cell viability and flow cytometry was used to detect apoptosis.

CONCLUSIONS

In this study, mouse primary neurons and microglial cells were co-cultured. The OGD and tOGD models were established successfully. tOGD was able to effectively protect neurons and microglial cells from damage, and inhibit the apoptosis caused by oxygen glucose deprivation.

Astrocytes Surviving Severe Stress Can Still Protect Neighboring Neurons from Proteotoxic Injury

Astrocytes are one of the major cell types to combat cellular stress and protect neighboring neurons from injury. In order to fulfill this important role, astrocytes must sense and respond to toxic stimuli, perhaps including stimuli that are severely stressful and kill some of the astrocytes. The present study demonstrates that primary astrocytes that managed to survive severe proteotoxic stress were protected against subsequent challenges. These findings suggest that the phenomenon of preconditioning or tolerance can be extended from mild to severe stress for this cell type. Astrocytic stress adaptation lasted at least 96 h, the longest interval tested. Heat shock protein 70 (Hsp70) was raised in stressed astrocytes, but inhibition of neither Hsp70 nor Hsp32 activity abolished their resistance against a second proteotoxic challenge. Only inhibition of glutathione synthesis abolished astrocytic stress adaptation, consistent with our previous report. Primary neurons were plated upon previously stressed astrocytes, and the cocultures were then exposed to another proteotoxic challenge. Severely stressed astrocytes were still able to protect neighboring neurons against this injury, and the protection was unexpectedly independent of glutathione synthesis. Stressed astrocytes were even able to protect neurons after simultaneous application of proteasome and Hsp70 inhibitors, which otherwise elicited synergistic, severe loss of neurons when applied together. Astrocyte-induced neuroprotection against proteotoxicity was not elicited with astrocyte-conditioned media, suggesting that physical cell-to-cell contacts may be essential. These findings suggest that astrocytes may adapt to severe stress so that they can continue to protect neighboring cell types from profound injury.

Top 10 TARN research publications

The last 25 years have seen Trauma Audit and Research Network's (TARN) research agenda develop into a significant portfolio of over 100 publications, including a number of international collaborations. Holding the largest trauma registry in Europe, TARN continues to provide researchers with the ability to pursue their interests in both epidemiological and clinical topics relating to traumatic injury. This edition of the Emergency Medicine Journal provides an opportunity to celebrate some of these papers with a ‘Top 10’, which have been voted by members of the TARN Research Committee on the basis of their impact.

An evaluation of the clinical and cost-effectiveness of alternative care locations for critically ill adult patients with acute traumatic brain injury

BACKGROUND

For critically ill adult patients with acute traumatic brain injury (TBI), we assessed the clinical and cost-effectiveness of: (a) Management in dedicated neurocritical care units versus combined neuro/general critical care units within neuroscience centres. (b) 'Early' transfer to a neuroscience centre versus 'no or late' transfer for those who present at a non-neuroscience centre.

METHODS

The Risk Adjustment In Neurocritical care (RAIN) Study included prospective admissions following acute TBI to 67 UK adult critical care units during 2009-11. Data were collected on baseline case-mix, mortality, resource use, and at six months, Glasgow Outcome Scale Extended (GOSE), and quality of life (QOL) (EuroQol 5D-3L). We report incremental effectiveness, costs and cost per Quality-Adjusted Life Year (QALY) of the alternative care locations, adjusting for baseline differences with validated risk prediction models. We tested the robustness of results in sensitivity analyses.

FINDINGS

Dedicated neurocritical care unit patients (N = 1324) had similar six-month mortality, higher QOL (mean gain 0.048, 95% CI -0.002 to 0.099) and increased average costs compared with those managed in combined neuro/general units (N = 1341), with a lifetime cost per QALY gained of £14,000. 'Early' transfer to a neuroscience centre (N = 584) was associated with lower mortality (odds ratio 0.52, 0.34-0.80), higher QOL for survivors (mean gain 0.13, 0.032-0.225), but positive incremental costs (£15,001, £11,123 to £18,880) compared with 'late or no transfer' (N = 263). The lifetime cost per QALY gained for 'early' transfer was £11,000.

CONCLUSIONS

For critically ill adult patients with acute TBI, within neuroscience centres management in dedicated neurocritical care units versus combined neuro/general units led to improved QoL and higher costs, on average, but these differences were not statistically significant. This study finds that 'early' transfer to a neuroscience centre is associated with reduced mortality, improvement in QOL and is cost-effective.

Induction of DJ-1 protects neuronal cells from isoflurane induced neurotoxicity

Oxidative stress, mitochondrial dysfunction and neuronal apoptosis are thought to be major contributors of Isoflurane toxicity. However, the underlying mechanisms remain largely to be determined. DJ-1, a protein that is involved in the response to various kinds of stress, has shown its neuroprotective effects. Whether DJ-1 has a neuroprotective effect against isoflurane-induced neurotoxocity is still unknown. In this study, we found that expression of DJ-1 is elevated in response to isoflurane treatment in human SH-SY5Y neuroblastoma cells. In order to clarify whether DJ-1 plays a potential role in isoflurane neurotoxicity or as a compensatory response for survival, we investigated the effects of DJ-1 silencing in isoflurane neurotoxicity. Our findings indicate that knockdown of DJ-1 promotes isoflurane-induced oxidative stress and mitochondrial dysfunction. Importantly, DJ-1 silencing was found to exacerbate isoflurane- induced apoptosis through modulation of mitochondria-dependent apoptosis pathways, thereby suggesting that induction of DJ-1 in response to isoflurane might act as a compensatory response for cell survival.

Save the patient a trip. Outcome difference between conservatively treated patients with traumatic brain injury in a nonspecialized intensive care unit vs a specialized neurosurgical intensive care unit in the Sultanate of Oman

Traumatic brain injury (TBI) continues to be the main cause of death among trauma patients. Accurate diagnosis and timely surgical interventions are critical steps in reducing the mortality from this disease. For patients who have no surgically reversible head injury pathology, the decision to transfer to a dedicated neurosurgical unit is usually controversial.

OBJECTIVE

To compare the outcome of patients with severe TBI treated conservatively in a specialized neurosurgical intensive care unit (ICU) and those treated conservatively at a general ICU in the Sultanate of Oman.

DESIGN

Retrospective cohort study.

METHODS

This is a retrospective study of patients with severe TBI admitted to Khoula Hospital ICU (specialized neurosurgical ICU) and Nizwa Hospital ICU (general ICU) in Oman in 2013. Surgically treated patients were excluded. Data extracted included demographics, injury details, interventions, and outcomes. The outcome variables included mortality, length of stay, length of ICU days, and ventilated days.

RESULTS

There were 100 patients with severe TBI treated conservatively at Khoula Hospital compared with 74 patients at Nizwa Hospital. Basic demographics were similar between the 2 groups. No significant difference was found in mortality, length of stay, ICU days, and ventilation days.

CONCLUSION

There is no difference in outcome between patients with TBI treated conservatively in a specialized neurosurgical ICU and those treated in a general nonspecialized ICU in Oman in 2013. Therefore, unless neurosurgical intervention is warranted or expected, patients with TBI may be managed in a general ICU, saving the risk and expense of a transfer to a specialized neurosurgical ICU.

Satisfaction of patients' next of kin in a 'Hub & Spoke' ICU network

This study aimed to gauge the opinions of patients' next of kin regarding transfer of patients from the specialist 'Hub' intensive care unit, to 'Spoke' intensive care units near home. We included 213 consecutive patients with severe trauma or severe acute neurological conditions admitted to the Hub intensive care unit over a 21-month period, who were repatriated to Spoke intensive care units for ongoing intensive care. One year after admission to the Hub intensive care unit, two thirds of patients' next of kin said they would have preferred patients to have been treated only in the Hub intensive care unit, and not repatriated. They perceived Hub intensive care unit care to be important, and would have preferred that their relatives be hospitalised there until intensive treatment was completed. The next of kin's preference was associated with severe acute neurological conditions (p ≤ 0.0001). Although centralised Hub & Spoke intensive care unit networks are appropriate to ensure specialised care, repatriation to local hospitals may not be appropriate for patients with severe neurological conditions.

Isoflurane reduces the ischemia reperfusion injury surge: a longitudinal study with MRI

BACKGROUND

Recent studies show neuroprotective benefits of isoflurane (ISO) administered during cerebral ischemia. However, the available studies evaluated cerebral injury only at a single time point following the intervention and thus the longitudinal effect of ISO on ischemic tissues remains to be investigated.

OBJECTIVE

The objective of the present study was to investigate the longitudinal effect of ISO treatment in counteracting the deleterious effect of ischemia by evoking the transcription factor, hypoxia inducible factor-1 (HIF-1), and vascular endothelial growth factor (VEGF).

METHODS

Focal cerebral ischemia was induced in 70 rats by filament medial cerebral artery occlusion (MCAo) method. MCAo rats were randomly assigned to control (90 min ischemia) and MCAo+ISO (90 min ischemia+2% ISO) groups. Infarct volume, edema, intracerebral hemorrhage (ICH), and regional cerebral blood flow (rCBF) were measured in eight in vivo sequential MR imaging sessions for 3 weeks. Western blot analysis and immunofluorescence were used to determine the expression level of HIF-1α (the regulatable subunit of HIF-1) and VEGF proteins.

RESULTS

ISO inhalation during ischemia significantly decreased the surge of infarct volume, edema, ICH, and reduced the mortality rate (p<0.01). ISO transiently altered the rCBF, significantly enhanced the expression of HIF-1α and VEGF, and decreased the immune cell infiltration. Locomotor dysfunction was ameliorated at a significantly faster pace, and the benefit was seen to persist up to three weeks.

CONCLUSION

Treatment with ISO during ischemia limits the deadly surge in the dynamics of ischemia reperfusion injury with no observed long-term inverse effect.

Biological sex and mechanisms of ischemic brain injury

Cerebrovascular disease is a leading cause of death-from-disease and of disability worldwide, affecting some 15 million people. The incidence of stroke or "brain attack" is unlikely to recede for a decade at minimum by most predictions, despite large public health initiatives in stroke prevention. It has been well established that stroke is also one of the most strikingly sex-specific diseases in its epidemiology, and in some cases, in patient outcomes. For example, women sustain lower rates of ischemic stroke relative to men, even beyond their menopausal years. In contrast, outcomes are worse in women in many clinical studies. The biological basis for this sexual dimorphism is a compelling story, and both hormone-dependent and hormone-independent factors are involved, the latter of which is the subject of this brief review. Understanding the molecular and cell-based mechanisms underlying sex differences in ischemic brain injury is an important step toward personalized medicine and effective therapeutic interventions in patients of both sexes.

Isoflurane protects against injury caused by deprivation of oxygen and glucose in microglia through regulation of the Toll-like receptor 4 pathway

Oxygen and glucose deprivation (OGD) are the most important factors related to tissue damage resulting from stroke. Microglial cells have been found to be very vulnerable to ischemia and OGD. It has been reported that isoflurane exposure can protect the mammalian brain from insults such as ischemic stroke; however, the effects of isoflurane on OGD-induced injury in microglia are as yet unknown. In this study, we investigated the effects of isoflurane on OGD-induced injury in microglia. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) revealed that OGD did indeed induce cell death in microglia. However, isoflurane preconditioning attenuated OGD-induced cell death. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay demonstrated that isoflurane treatment alleviated OGD-induced apoptosis. Toll-like receptor 4 (TLR4) plays a considerable role in the induction of innate immune and inflammatory responses. Our results indicate that isoflurane preconditioning inhibits the upregulation of TLR4 as well as the activation of its downstream molecules, such as c-Jun N-terminal kinase (JNK) and nuclear factor kappa B (NF-κB), in BV-2 microglia exposed to OGD. Importantly, we also found that isoflurane pretreatment significantly reduces the production of proinflammatory factors such as tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), IL-β, and nitric oxide (NO). The results indicate that TLR4 and its downstream NF-κB-dependent signaling pathway contribute to the neuroprotection of microglia exposed to OGD/reoxygenation by administration of isoflurane.

Evidence for the use of isoflurane as a replacement for chloral hydrate anesthesia in experimental stroke: an ethical issue

Since an ethical issue has been raised regarding the use of the well-known anesthetic agent chloral hydrate, owing to its mutagenic and carcinogenic effects in animals, attention of neuroscientists has turned to finding out an alternative agent able to meet not only potency, safety, and analgesic efficacy, but also reduced neuroprotective effect for stroke research. The aim of this study was to compare the potential of chloral hydrate and isoflurane for both modulating the action of the experimental neuroprotectant MK801 and exerting analgesia. After middle cerebral artery occlusion in rats, no difference was observed in 24 h survival rate, success of ischemia, or infarct volume reduction between both anesthetics. However, isoflurane exerted a more pronounced analgesic effect than chloral hydrate as evidenced by formalin test 3 hours after anesthesia onset, thus encouraging the use of isoflurane in experimental stroke models.

The effectiveness of specialist neuroscience care in severe traumatic brain injury: a systematic review

BACKGROUND

UK trauma services are currently undergoing reconfiguration, but the optimum management pathway for head-injured patients is uncertain. We therefore performed a systematic review to assess the effects of routine inter-hospital transfer and specialist neuroscience care on mortality and disability in patients with non-surgical severe traumatic brain injury injured nearest to a non-specialist acute hospital.

METHODS

A protocol was registered with PROSPERO (CRD42012002021) and review methodology followed Cochrane Collaboration recommendations. A peer reviewed search strategy was implemented in an exhaustive range of information sources, including all major bibliographic databases, between 1973 and July 2013. Selection of eligible studies, extraction of relevant data and bias assessment were then performed by two independent reviewers. In the absence of homogeneous effect estimates at low risk of bias a narrative synthesis was pre-specified.

RESULTS

Four cohort studies, including a total of 4688 patients, were identified as potentially eligible after screening and bias assessment. Confounding by indication, arising from selective transfer of less severely injured patients, was the main limitation of included studies, with overall risk of bias rated as high for both mortality and disability effect estimates. Adjusted odds ratios for mortality favoured secondary transfer, ranging from 1.92 (95% CI 1.25-2.95) to 2.09 (95% CI 1.59-2.74). No convincing association was observed between non-specialist care and unfavourable outcome with a conditional odds ratio of 1.13 (95% CI 0.36-3.6).

CONCLUSIONS

There is limited evidence supporting a strategy of secondary transfer of severe non-surgical traumatic brain injury patients to specialist neuroscience centres. Randomised controlled trials powered to detect clinically plausible treatment effects should be considered to definitively investigate effectiveness.

Do prolonged primary transport times for traumatic brain injury patients result in deteriorating physiology? A cohort study

BACKGROUND

Recent interest has focused on reorganizing emergency medical services (EMS) for traumatic brain injury (TBI) patients, with bypass of nonspecialist hospitals and direct transportation to distant neuroscience centers. Although this could expedite neurosurgery and neurocritical care, deteriorating physiology could be deleterious.

METHODS

We performed a multicenter cohort study examining adult patients with significant TBI enrolled in the English National Trauma Registry. The distributions and correlation of first recorded prehospital and emergency department (ED) vital signs were compared, and the effect of time on changes in vital signs was examined in bivariate and multivariate analyses.

RESULTS

A total of 7149 eligible patients were studied. No clinically significant differences were apparent between distributions of prehospital and ED vital signs. Moderate linear correlation was observed for field and ED pulse rate (r(2) = 0.34) and GCS values (Spearman's rho = 0.76), with weak correlation apparent for systolic blood pressure (r(2) = 0.28) and respiratory rate (r(2) = 0.28). Eight percent of cases' vital signs deteriorated in the prehospital interval; however, odds of deterioration in vital sign status did not vary significantly with duration of EMS interval.

CONCLUSION

The similarity between prehospital and ED vital signs, and lack of association between EMS interval and physiological deterioration, may support a strategy of direct transportation of TBI cases to specialist centers. Further research is necessary to identify patients at risk from deterioration during bypass and to investigate effects on mortality.

The accuracy of alternative triage rules for identification of significant traumatic brain injury: a diagnostic cohort study

INTRODUCTION

Traumatic brain injury (TBI) is a leading cause of death and disability in young adults. Reorganisation of trauma services with direct triage of suspected head injury patients to trauma centres may improve outcomes following TBI. This study aimed to determine the sensitivity of principal English triage tools for identifying significant TBI.

METHODS

We performed a diagnostic cohort study using data prospectively collated from the Trauma Audit and Research Network database between 2005 and 2011. Adult head injury patients were retrospectively classified according to London Ambulance Service (LAS) and Head Injury Transportation Straight to Neurosurgery study (HITS-NS) triage criteria. Sensitivity and specificity were then calculated against a reference standard of significant TBI, comprising head region abbreviated injury score (AIS) ≥3 or neurosurgical operation.

RESULTS

6559 patients were included in complete case analyses. The LAS and HITS-NS triage tools demonstrated sensitivities of 44.5% (95% CI 43.2 to 45.9) and 32.6% (95% CI 31.4 to 33.9), respectively, for identifying significant TBI patients. False negative significant TBI cases were relatively older, more likely to be female, more frequently secondary to low-level falls, and were less likely to have very severe AIS five or six head injuries, p<0.01.

CONCLUSIONS

A considerable proportion of significant head injury patients may not be triaged directly to trauma centres. Investment is therefore necessary to improve the accuracy of existing triage rules and maintain expertise in TBI diagnosis and management in non-specialist emergency departments.

Adaptation and sensitization to proteotoxic stress

Although severe stress can elicit toxicity, mild stress often elicits adaptations. Here we review the literature on stress-induced adaptations versus stress sensitization in models of neurodegenerative diseases. We also describe our recent findings that chronic proteotoxic stress can elicit adaptations if the dose is low but that high-dose proteotoxic stress sensitizes cells to subsequent challenges. In these experiments, long-term, low-dose proteasome inhibition elicited protection in a superoxide dismutase-dependent manner. In contrast, acute, high-dose proteotoxic stress sensitized cells to subsequent proteotoxic challenges by eliciting catastrophic loss of glutathione. However, even in the latter model of synergistic toxicity, several defensive proteins were upregulated by severe proteotoxicity. This led us to wonder whether high-dose proteotoxic stress can elicit protection against subsequent challenges in astrocytes, a cell type well known for their resilience. In support of this new hypothesis, we found that the astrocytes that survived severe proteotoxicity became harder to kill. The adaptive mechanism was glutathione dependent. If these findings can be generalized to the human brain, similar endogenous adaptations may help explain why neurodegenerative diseases are so delayed in appearance and so slow to progress. In contrast, sensitization to severe stress may explain why defenses eventually collapse in vulnerable neurons.

Decompressive craniectomy: past, present and future

Decompressive craniectomy (DC)--a surgical procedure that involves removal of part of the skull to accommodate brain swelling--has been used for many years in the management of patients with brain oedema and/or intracranial hypertension, but its place in contemporary practice remains controversial. Results from a recent trial showed that early (neuroprotective) DC was not superior to medical management in patients with diffuse traumatic brain injury. An ongoing trial is investigating the clinical and cost effectiveness of secondary DC as a last-tier therapy for post-traumatic refractory intracranial hypertension. With regard to ischaemic stroke (malignant middle cerebral artery infarction), a recent Cochrane review concluded that DC improves survival compared with medical management, but that a higher proportion of DC survivors experience moderately severe or severe disability. Although many patients have a good outcome, the issue of DC-related disability raises important ethical issues. As DC and subsequent cranioplasty are associated with a number of complications, indiscriminate use of this surgery is not appropriate. Here, we review the evidence and present considerations regarding surgical technique, ethics and cost-effectiveness of DC. Prospective clinical trials and cohort studies are essential to enable optimization of patient care and outcomes.

Astrocyte plasticity revealed by adaptations to severe proteotoxic stress

Neurodegeneration is characterized by an accumulation of misfolded proteins in neurons. It is less well appreciated that glia often also accumulate misfolded proteins. However, glia are highly plastic and may adapt to stress readily. Endogenous adaptations to stress can be measured by challenging stressed cells with a second hit and then measuring viability. For example, subtoxic stress can elicit preconditioning or tolerance against second hits. However, it is not known if severe stress that kills half the population can elicit endogenous adaptations in the remaining survivors. Glia, with their resilient nature, offer an ideal model in which to test this new hypothesis. The present study is the first demonstration that astrocytes surviving one LC50 hit of the proteasome inhibitor MG132 were protected against a second MG132 hit. ATP loss in response to the second hit was also prevented. MG132 caused compensatory rises in stress-sensitive heat shock proteins. However, stressed astrocytes exhibited an even greater rise in ubiquitin-conjugated proteins upon the second hit, illustrating the severity of the proteotoxicity and verifying the continued impact of MG132. Despite this stress, MG132-pretreated astrocytes were completely prevented from losing glutathione with the second hit. Furthermore, inhibiting glutathione synthesis rendered astrocytes sensitive to the second hit, unmasking the cumulative impact of two hits by removal of an endogenous adaptation. These findings suggest that stressed astrocytes become progressively harder to kill by virtue of antioxidant defenses. Such plasticity may permit astrocytes under severe stress to better support neurons and help explain the protracted nature of neurodegeneration.

Effective management of severe traumatic brain injury in a district hospital

The authors investigated how effectively adults with severe traumatic brain injury (TBI) can be managed in a district general hospital intensive care unit offering intracranial pressure monitoring (ICPM) receiving advice from a neurosurgical unit. A single-centre case series with retrospective review of prospectively collected information was undertaken of 44 consecutive patients presenting over seven years from January 2003 to January 2010 with severe traumatic brain injury to a single district general hospital intensive care unit serving a population of 500,000 adults. A prospectively entered clinical database was used to obtain information including patient demographics, Glasgow Coma Score (GCS) on admission, ICPM insertion, ICPM-related complications, inpatient mortality and neurosurgical advice. Case notes were used to ratify information and obtain neurorehabilitation clinic functional outcome scores. Forty-four patients were identified (40 male, age range 16-77 years). Mortality in intensive care was 30%. Twenty-eight patients received frontal twist drill ICPM following neurosurgical advice. ICPM had 2 (7%) device malfunctions but no other complications. Twelve additional patients were transferred to tertiary centres. Patients (23 of 31) who survived ICU stay (74%) were referred to neurorehabilitation. Mean clinic follow-up was 14 months. All patients had a Glasgow Outcome Score (GOS) of 3 or 4 at initial clinic assessment. Twenty-two improved to GOS to 4 or 5 at clinic discharge. One patient died prior to clinic discharge. Carefully selected patients with severe TBI can be managed safely and effectively in a district general hospital offering ICPM insertion if transfer to a neurosurgical centre is not possible. Neurosurgical advice regarding patient selection and on-going management is fundamental to provide a good service. Protocol driven therapies provide a useful systematic approach to doctors who do not deal with severe TBI on a routine basis.

Isoflurane does not cause neuroapoptosis but reduces astroglial processes in young adult mice

BACKGROUND

Isoflurane, a volatile anesthetic widely used clinically, has been implicated to be both neuroprotective and neurotoxic. The claim about isoflurane causing neural apoptosis remains controversial. In this study, we investigated the effects of isoflurane exposures on apoptotic and anti-apoptotic signals, cell proliferation and neurogenesis, and astroglial processes in young adult mouse brains.

METHODS

Sixty 6-week-old mice were randomly assigned to four anesthetic concentration groups (0 as control and 0.6%, 1.3%, and 2%) with four recovery times (2 h and 1, 6, and 14 d) after 2-h isoflurane exposure. Immunohistochemistry measurements of activated caspase-3 and Bcl-xl for apoptotic and anti-apoptotic signals, respectively, glial fibrillary acidic protein (GFAP) and vimentin for reactive astrocytosis, doublecortin (Dcx) for neurogenesis, and BrdU for cell proliferation were performed.

RESULTS

Contrary to the previous conclusion derived from studies with neonatal rodents, we found no evidence of isoflurane-induced apoptosis in the adult mouse brain. Neurogenesis in the subgranule zone of the dentate gyrus was not affected by isoflurane. However, there is a tendency of reduced cell proliferation after 2% isoflurane exposure. VIM and GFAP staining showed that isoflurane exposure caused a delayed reduction of astroglial processes in the hippocampus and dentate gyrus.

CONCLUSION

Two-hour exposure to isoflurane did not cause neuroapoptosis in adult brains. The delayed reduction in astroglial processes after isoflurane exposure may explain why some volatile anesthetics can confer neuroprotection after experimental stroke because reduced glial scarring facilitates better long-term neuronal recoveries.

Isoflurane preconditioning protects neurons from male and female mice against oxygen and glucose deprivation and is modulated by estradiol only in neurons from female mice

The volatile anesthetic, isoflurane, can protect the brain if administered before an insult such as an ischemic stroke. However, this protective "preconditioning" response to isoflurane is specific to males, with females showing an increase in brain damage following isoflurane preconditioning and subsequent focal cerebral ischemia. Innate cell sex is emerging as an important player in neuronal cell death, but its role in the sexually dimorphic response to isoflurane preconditioning has not been investigated. We used an in vitro model of isoflurane preconditioning and ischemia (oxygen and glucose deprivation, OGD) to test the hypotheses that innate cell sex dictates the response to isoflurane preconditioning and that 17β-estradiol attenuates any protective effect from isoflurane preconditioning in neurons via nuclear estrogen receptors. Sex-segregated neuron cultures derived from postnatal day 0-1 mice were exposed to either 0% or 3% isoflurane preconditioning for 1 h. In separate experiments, 17β-estradiol and the non-selective estrogen receptor antagonist ICI 182,780 were added 24 h before preconditioning and then removed at the end of the preconditioning period. Twenty-three hours after preconditioning, all cultures underwent 2 h of OGD. Twenty-four hours following OGD, cell viability was quantified using calcein-AM fluorescence. We observed that isoflurane preconditioning increased cell survival following subsequent OGD regardless of innate cell sex, but that the presence of 17β-estradiol before and during isoflurane preconditioning attenuated this protection only in female neurons independent of nuclear estrogen receptors. We also found that independent of preconditioning treatment, female neurons were less sensitive to OGD compared with male neurons and that transient treatment with 17β-estradiol protected both male and female neurons from subsequent OGD. More studies are needed to determine how cell type, cell sex, and sex steroids like 17β-estradiol may impact on anesthetic preconditioning and subsequent ischemic outcomes in the brain.