Anesthetic Neuroprotection in Experimental Stroke in Rodents: A Systematic Review and Meta-analysis

Chronic hypertension and perfusion deficits conjointly affect disease outcome after tPA treatment in a rodent model of thromboembolic stroke

Futile recanalization hampers prognoses for ischemic stroke patients despite successful recanalization therapy. Allegedly, hypertension and reperfusion deficits contribute, but a better understanding is needed of how they interact and mediate disease outcome. We reassessed data from spontaneously hypertensive and normotensive Wistar-Kyoto rats (male, n = 6-7/group) that were subjected to two-hour embolic middle cerebral artery occlusion and thrombolysis in preclinical trials. Serial MRI allowed lesion monitoring and parcellation of regions-of-interest that represented infarcted (core) or recovered (perilesional) tissue. Imaging markers of hemodynamics and blood-brain barrier (BBB) status were related to tissue fate and neurological outcome. Despite comparable ischemic severity during occlusion between groups, hypertensive rats temporarily developed larger lesions after recanalization, with permanently aggravated vasogenic edema and BBB permeability. One day post-stroke, cerebral blood flow (CBF) was variably restored, but blood transit times were consistently prolonged in hypertensives. Compared to the core, perilesional CBF was normo-to-hyperperfused in both groups, yet this pattern reversed after seven days. Volumes of hypo- and hyperperfusion developed irrespective of strain, differentially associating with final infarct volume and behavioral outcome. Incomplete reperfusion and cerebral injury after thrombolysis were augmented in hypertensive rats. One day after thrombolysis, fractional volumes of hypoperfusion associated with worsened outcomes, while fractional volumes of hyperperfusion appeared beneficial or benign.

The Role of Desflurane in the Functional Outcomes Among Spinal Cord Injury Patients Undergoing Upper Extremity Nerve Transfer Procedures

Background and objective While several experimental studies have demonstrated the neuroprotective role of volatile anesthetics after spinal cord injury (SCI), the impact of volatile anesthetics on improving neurologic outcomes in spinal cord-injured patients is not known. Hence, this study aimed to examine the impact of volatile anesthetics on functional outcomes of chronic cervical SCI patients undergoing peripheral nerve transfer procedures. Methods We conducted a retrospective analysis involving adult patients with cervical SCI and upper extremity paralysis undergoing nerve transfer procedures between September 1, 2015, and January 31, 2019. The principal outcome measured was the motor strength of the reinnervated muscle targets assessed per the Medical Research Council (MRC) scale graded from 0 to 5. Secondary outcomes included Disabilities of Arm, Shoulder, and Hand (DASH); Sollerman Hand Function Test (SHFT); and Michigan Hand Questionnaire (MHQ) scores. Univariate analysis and logistic regression were performed to examine the association between the volatile anesthetics (sevoflurane, desflurane) used during the nerve transfer surgery with the improvement in muscle strength examined up to 48 months postoperatively. Results A total of 13 tetraplegic patients with a mean age of 39.2 ± 15.9 years were included in this study. We found that the desflurane group (n=22 muscles) had greater median motor strength than the sevoflurane group (n=60 muscles) towards the final follow-up when the desflurane group had median motor strength of 3 [interquartile range (IQR): 1-4] and sevoflurane group had a median motor strength of 1 (IQR: 0-2.25); p=0.014. However, there was no statistically significant difference between the two groups in the DASH, SHFT, and MHQ scores. Logistic regression analysis showed that type of nerve transfer and preop AIS (ASIA Impairment Scale) grade were significantly associated with higher odds of improvement of motor power by at least 2 grades. Conclusions Our preliminary data show an association between desflurane use and improved motor strength in SCI patients undergoing peripheral nerve transfers. The data suggest that volatile anesthetic conditioning-induced protection observed in preclinical studies may also exist in SCI patients. This will need to be validated in a larger sample size. Examining the therapeutic window, and identifying the molecular mechanisms underlying volatile anesthetic conditioning-induced protection are warranted to aid future translational studies.

Modeling of Cerebral Ischemic Stroke in Conscious Rats via Arterial Air Embolization

The etiological factor of cerebral ischemia in the vast majority of cases is vascular embolism. In the present study we investigated embolism caused by atmospheric air bubbles injected into the internal carotid artery of conscious rats. Immediately after embolism modeling, behavioral abnormalities were observed in the animals, and after 24 h, foci of brain damage were detected. The death of animals was observed within 5 days after embolism. The proposed experimental model of cerebral ischemia in conscious rats is more relevant and better corresponds to real conditions than the model on narcotized animals and allows to perform physiological tests immediately after modeling.

Isoflurane conditioning improves functional outcomes after peripheral nerve injury in a sciatic cut repair murine model

Introduction

Anesthetic conditioning has been shown to provide neuroprotection in several neurological disorders. Whether anesthetic conditioning provides protection against peripheral nerve injuries remains unknown. The aim of our current study is to investigate the impact of isoflurane conditioning on the functional outcomes after peripheral nerve injury (PNI) in a rodent sciatic nerve injury model.

Methods

Adult male Lewis rats underwent sciatic nerve cut and repair and exposed to none (Group 1, sham), single isoflurane exposure (Group 2), three-time isoflurane exposure (Group 3), and six-time isoflurane exposure (Group 4). Isoflurane conditioning was established by administration of 2% isoflurane for 1 hour, beginning 1-hour post sciatic nerve cut and repair. Groups 3 and 4 were exposed to isoflurane for 1 hour, 3 and 6 consecutive days respectively. Functional outcomes assessed included compound muscle action potential (CMAP), evoked muscle force (tetanic and specific tetanic force), wet muscle mass, and axonal counting.

Results

We observed an increase in axons, myelin width and a decrease in G-ratio in the isoflurane conditioning groups (3- and 6-days). This correlated with a significant improvement in tetanic and specific tetanic forces, observed in both groups 3 and 4.

Discussion

Isoflurane conditioning (3- and 6-day groups) resulted in improvement in functional outcomes at 12 weeks post peripheral nerve injury and repair in a murine model. Future experiments should be focused on identifying the therapeutic window of isoflurane conditioning and exploring the underlying molecular mechanisms responsible for isoflurane conditioning induced neuroprotection in PNI.

Neuroendovascular Rescue 2025: Trends in Stroke Endovascular Therapy

Neuroendovascular rescue of patients with acute ischemic stroke caused by a large arterial occlusion has evolved throughout the first quarter of the present century, and continues to do so. Starting with the intra-arterial instillation of thrombolytic agents via microcatheters to dissolve occluding thromboembolic material, the current status is one that includes a variety of different techniques such as direct aspiration of thrombus, removal by stent retriever, adjuvant techniques such as balloon angioplasty, stenting, and tactical intra-arterial instillation of thrombolytic agents in smaller branches to treat no-reflow phenomenon. The results have been consistently shown to benefit these patients, irrespective of whether they had already received intravenous tissue-type plasminogen activator or not. Improved imaging methods of patient selection and tactically optimized periprocedural care measures complement this dimension of the practice of neurointervention.

Type of anesthesia for endovascular therapy in acute ischemic stroke: A literature review and meta-analysis

BACKGROUND

Endovascular thrombectomy (EVT) has been proven as the standard treatment for acute ischemic stroke (AIS) patients due to large vessel occlusion (LVO). However, the ideal anesthetic strategy during EVT still remains unclear. Therefore, this systematic review and meta-analysis aimed to determine the optimal anesthetic modality for patients with AIS undergoing EVT based on current randomized controlled trials (RCTs).

METHODS

The databases Medline (via PubMed), EMBASE, Web of Science, and the Cochrane Library were searched for RCTs comparing general anesthesia (GA) and conscious sedation (CS) in AIS patients undergoing EVT. The primary outcome was a favorable functional outcome at 90 days postintervention. Data analysis was conducted using the Review Manager software (RevMan V.5.3).

RESULTS

Eight RCTs involving 1199 patients were included. There was no significant difference between GA and CS group in the rate of functional independence (risk ratio (RR) = 1.10, 95% confidence interval (CI) = 0.96 to 1.25; p = 0.17; I2 = 30%). Compared with the CS group, the GA group attained a higher successful recanalization rate (RR = 1.14, 95% CI = 1.08 to 1.20; p < 0.00001; I2 = 17%). In addition, patients in the GA were associated with a higher rate of hypotension (RR = 1.87, 95% CI = 1.44 to 2.41; p < 0.00001; I2 = 66%) and a higher incidence of pneumonia (RR = 1.38, 95% CI = 1.05 to 1.8; p = 0.02; I2 = 37%).

CONCLUSION

For AIS patients receiving EVT, the choice of anesthetic modality did not influence the 3-month neurological outcome while GA is superior to CS in terms of successful reperfusion rate. Moreover, the patients in the GA group were at a higher risk of developing hypotension and pneumonia. Further studies are required to provide more sufficient evidence.

Stroke and Translational Research - Review of Experimental Models with a Focus on Awake Ischaemic Induction and Anaesthesia

Animal models are an indispensable tool in the study of ischaemic stroke with hundreds of drugs emerging from the preclinical pipeline. However, all of these drugs have failed to translate into successful treatments in the clinic. This has brought into focus the need to enhance preclinical studies to improve translation. The confounding effects of anaesthesia on preclinical stroke modelling has been raised as an important consideration. Various volatile and injectable anaesthetics are used in preclinical models during stroke induction and for outcome measurements such as imaging or electrophysiology. However, anaesthetics modulate several pathways essential in the pathophysiology of stroke in a dose and drug dependent manner. Most notably, anaesthesia has significant modulatory effects on cerebral blood flow, metabolism, spreading depolarizations, and neurovascular coupling. To minimise anaesthetic complications and improve translational relevance, awake stroke induction has been attempted in limited models. This review outlines anaesthetic strategies employed in preclinical ischaemic rodent models and their reported cerebral effects. Stroke related complications are also addressed with a focus on infarct volume, neurological deficits, and thrombolysis efficacy. We also summarise routinely used focal ischaemic stroke rodent models and discuss the attempts to induce some of these models in awake rodents.

Acute Ischemic Stroke in the Clinic and the Laboratory: Targets for Translational Research

Ischemic stroke research has enabled significant advancements in diagnosis, treatment, and management of this debilitating disease, yet challenges remain standing in the way of better patient prognoses. In this narrative review, a fictional case illustrates challenges and uncertainties that medical professionals still face - penumbra identification, lack of neuroprotective agents, side-effects of tissue plasminogen activator, dearth of molecular biomarkers, incomplete microvascular reperfusion or no-reflow, post-recanalization hyperperfusion, blood pressure management and procedural anesthetic effects. The current state of the field is broadly reviewed per topic, with the aim to introduce a broad audience (scientist and clinician alike) to recent successes in translational stroke research and pending scientific queries that are tractable for preclinical assessment. Opportunities for co-operation between clinical and experimental stroke experts are highlighted to increase the size and frequency of strides the field makes to improve our understanding of this disease and ways of treating it.

Isoflurane preconditioning induced genomic changes in mouse cortex

Background

Altered patterns of genetic expression induced by isoflurane preconditioning in mouse brain have not yet been investigated. The aim of our pilot study is to examine the temporal sequence of changes in the transcriptome of mouse brain cortex produced by isoflurane preconditioning.

Methods

Twelve-wk-old wild-type (C57BL/6J) male mice were randomly assigned for the experiments. Mice were exposed to isoflurane 2% in air for 1 h and brains were harvested at the following time points-immediately (0 h), and at 6, 12, 24, 36, 48, and 72 h after isoflurane exposure. A separate cohort of mice were exposed to three doses of isoflurane on days 1, 2, and 3 and brains were harvested after the third exposure. The NanoString mouse neuropathology panel was used to analyse isoflurane-induced gene expression in the cortex. The neuropathology panel included 760 genes covering pathways involved in neurodegeneration and other nervous system diseases, and 10 internal reference genes for data normalisation.

Results

Genes involving several pathways were upregulated and downregulated by isoflurane preconditioning. Interestingly, a biphasic response was noted, meaning, an early expression of genes (until 6 h), followed by a transient pause (until 24 h), and a second wave of genomic response beginning at 36 h of isoflurane exposure was noted.

Conclusions

Isoflurane preconditioning induces significant alterations in the genes involved in neurodegeneration and other nervous system disorders in a temporal sequence. These data could aid in the identification of molecular mechanisms behind isoflurane preconditioning-induced neuroprotection in various central nervous system diseases.

Propofol anesthesia improves stroke outcomes over isoflurane anesthesia-a longitudinal multiparametric MRI study in a rodent model of transient middle cerebral artery occlusion

General anesthesia is routinely used in endovascular thrombectomy procedures, for which volatile gas and/or intravenous propofol are recommended. Emerging evidence suggests propofol may have superior effects on disability and/or mortality rates, but a mode-of-action underlying these class-specific effects remains unknown. Here, a moderate isoflurane or propofol dosage on experimental stroke outcomes was retrospectively compared using serial multiparametric MRI and behavioral testing. Adult male rats (N = 26) were subjected to 90-min filament-induced transient middle cerebral artery occlusion. Diffusion-, T2- and perfusion-weighted MRI was performed during occlusion, 0.5 h after recanalization, and four days into the subacute phase. Sequels of ischemic damage-blood-brain barrier integrity, cerebrovascular reactivity and sensorimotor functioning-were assessed after four days. While size and severity of ischemia was comparable between groups during occlusion, isoflurane anesthesia was associated with larger lesion sizes and worsened sensorimotor functioning at follow-up. MRI markers indicated that cytotoxic edema persisted locally in the isoflurane group early after recanalization, coinciding with burgeoning vasogenic edema. At follow-up, sequels of ischemia were further aggravated in the post-ischemic lesion, manifesting as increased blood-brain barrier leakage, cerebrovascular paralysis and cerebral hyperperfusion. These findings shed new light on how isoflurane, and possibly similar volatile agents, associate with persisting injurious processes after recanalization that contribute to suboptimal treatment outcome.

Implications of Post-recanalization Perfusion Deficit After Acute Ischemic Stroke: a Scoping Review of Clinical and Preclinical Imaging Studies

The goal of reperfusion therapy for acute ischemic stroke (AIS) is to restore cerebral blood flow through recanalization of the occluded vessel. Unfortunately, successful recanalization does not always result in favorable clinical outcome. Post-recanalization perfusion deficits (PRPDs), constituted by cerebral hypo- or hyperperfusion, may contribute to lagging patient recovery rates, but its clinical significance remains unclear. This scoping review provides an overview of clinical and preclinical findings on post-ischemic reperfusion, aiming to elucidate the pattern and consequences of PRPD from a translational perspective. The MEDLINE database was searched for quantitative clinical and preclinical studies of AIS reporting PRPD based on cerebral circulation parameters acquired by translational tomographic imaging methods. PRPD and stroke outcome were mapped on a charting table, creating an overview of PRPD after AIS. Twenty-two clinical and twenty-two preclinical studies were included. Post-recanalization hypoperfusion is rarely reported in clinical studies (4/22) but unequivocally associated with detrimental outcome. Post-recanalization hyperperfusion is more commonly reported (18/22 clinical studies) and may be associated with positive or negative outcome. PRPD has been replicated in animal studies, offering mechanistic insights into causes and consequences of PRPD and allowing delineation of possible courses of PRPD. Complex relationships exist between PRPD and stroke outcome. Diversity in methods and lack of standardized definitions in reperfusion studies complicate the characterization of reperfusion patterns. Recommendations are made to advance the understanding of PRPD mechanisms and to further disentangle the relation between PRPD and disease outcome.

Brain Tissue Oxygen Dynamics Under Localised Hypoxia in the Awake State and the Physical Neuroprotective Effects of General Anaesthesia

Brain health directly depends on maintaining a level of tissue oxygen that is high enough to avoid global hypoxia and local brain ischaemia. It is well documented that general anaesthesia has an anti-hypoxic neuroprotective effect. Previous studies of this effect primarily assessed the biochemical actions of anaesthetics. Physical actions were not well studied because the quantification of oxygen dynamics has only recently been described. Based on known oxygen, blood, and neuronal measurements, under various anaesthesia protocols and in the awake state, we mathematically analysed physical anaesthesia effects on oxygen distribution for localised hypoxia. From this, we built a universal equation of oxygen dynamics which can be applied to both animal and human subjects in awake and anaesthetised states, under normoxia, hyperoxia, and hypoxia. Using this equation, we determined that a proper anaesthesia protocol can protect up to 167 mm3 of local hypoxic cortical brain tissue via oxygen diffusion from healthy neighbouring areas.

The Effect of Anesthetic Agent and Mean Arterial Pressure on Functional Outcome After General Anesthesia for Endovascular Thrombectomy

BACKGROUND

The optimal general anesthetic (GA) technique for stroke patients undergoing endovascular thrombectomy (ET) is unclear. We compared favorable outcomes and mortality in patients receiving propofol or volatile GA during ET and assessed associations between mean arterial pressure (MAP) and outcome.

METHODS

Ninety-three patients with anterior circulation stroke who received propofol or volatile GA during ET between February 2015 and February 2018 were included in this retrospective study. Ninety-day modified Rankin scores were compared and mortality was adjusted for intravenous thrombolysis and diabetes. We performed ordinal logistic regression analyses containing MAP time/exposure thresholds.

RESULTS

There was no difference in the rate of favorable outcome (modified Rankin scores 0-2) in the volatile and propofol groups (48.8% vs. 55.8%, respectively; P =0.5). Ninety-day mortality was lower in patients receiving propofol (11.5%) than in those receiving volatile GA (29.3%) (odds ratio, 0.32; 95% confidence interval, 0.11 to 0.94; P =0.03); this mortality benefit was greater in patients that did not receive intravenous thrombolysis before ET (odds ratio for survival, 6; 95% confidence interval, 1.13 to 31.74). There was no difference in MAP between groups and a (nonsignificant) trend towards the benefit of MAP <90 mm Hg but not <70 mm Hg.

CONCLUSIONS

Favorable outcome rates were similar in stroke patients receiving propofol or volatile GA during ET. Propofol was associated with lower mortality, an effect magnified in patients that did not receive intravenous thrombolysis. MAP time/exposure thresholds were associated with outcome but independent of the anesthetic agent. Our data suggest that a difference in outcome related to an anesthetic agent may exist; this hypothesis needs to be tested in a prospective study.

Propofol-Based Anesthesia Maintenance and/or Volatile Anesthetics during Intracranial Aneurysm Repair: A Comparative Analysis of Neurological Outcomes

BACKGROUND

Volatile and intravenous anesthetics have substantial effects on physiological functions, notably influencing neurological function and susceptibility to injury. Despite the importance of the anesthetic approach, data on its relative risks or benefits during surgical clipping or endovascular treatments for unruptured intracranial aneurysms (UIAs) remains scant. We investigated whether using volatile anesthetics alone or in combination with propofol infusion yields superior neurological outcomes following UIA obliteration.

METHODS

We retrospectively reviewed 1001 patients who underwent open or endovascular treatment for UIA, of whom 596 had short- and long-term neurological outcome data (modified Rankin Scale) recorded. Multivariable ordinal regression analysis was performed to examine the association between the anesthetic approach and outcomes.

RESULTS

Of 1001 patients, 765 received volatile anesthetics alone, while 236 received propofol infusion and volatile anesthetics (combined anesthetic group). Short-term neurological outcome data were available for 619 patients and long-term data for 596. No significant correlation was found between the anesthetic approach and neurologic outcomes, irrespective of the type of procedure (open craniotomy or endovascular treatment). The combined anesthetic group had a higher rate of ICU admission (p < 0.001) and longer ICU and hospital length of stay (LOS, p < 0.001). Similarly, a subgroup analysis revealed longer ICU and hospital LOS (p < 0.0001 and p < 0.001, respectively) in patients who underwent endovascular UIA obliteration under a combined anesthetic approach (n = 678).

CONCLUSIONS

The addition of propofol to volatile anesthetics during UIA obliteration does not provide short- or long-term benefits to neurologic outcomes. Compared to volatile anesthetics alone, the combination of propofol and volatile anesthetics may be associated with an increased rate of ICU admission, as well as longer ICU and hospital LOS.

The effect of estrogen therapy on cerebral metabolism in diabetic female rats

The impact of estrogen on brain function, especially in individuals with diabetes, remains uncertain. This study aims to compare cerebral glucose metabolism levels in intact rats, ovariectomized (OVX) rats, and 17β-estradiol (E2)-treated OVX diabetic female rats. Sixteen rats were administered a single intraperitoneal injection of 70 mg/kg streptozotocin (STZ) to induce diabetes (intact, n = 6; OVX, n = 6; OVX+E2-treated, n = 4). Additionally, 18 rats received an equivalent solvent dose via intraperitoneal injection (intact, n = 6; OVX, n = 6; OVX+E2-treated, n = 6). After 4 weeks of STZ or solvent administration, positron emission tomography scans with 18F-fluorodeoxyglucose (18F-FDG) injection were employed to assess cerebral glucose metabolism. The diabetic rats exhibited substantial reductions in 18F-FDG uptake across all brain regions (all P < 0.01), in contrast to the control rats. Moreover, intact and OVX + E2-treated diabetic female rats displayed more pronounced decreases in cerebral glucose metabolism in the amygdala and hippocampus compared to OVX diabetic female rats (P < 0.05). These findings suggest that diabetes creates an environment wherein estrogen exacerbates neuropathology and intensifies neuronal activity.

Distinctions between the Koizumi and Zea Longa methods for middle cerebral artery occlusion (MCAO) model: a systematic review and meta-analysis of rodent data

Ischemic stroke in rodents is usually induced by intraluminal middle cerebral artery occlusion (MCAO) via the common carotid artery plugging filament invented by Koizumi et al. (MCAO-KM), or the external carotid artery plugging filament created by Zea Longa et al. (MCAO-LG). A systematic review of the distinctions between them is currently lacking. Here, we performed a meta-analysis in terms of model establishment, cerebral blood flow (CBF), and cerebral ischemia-reperfusion injury (CIRI) between them, Weighted Mean Differences and Standardized Mean Difference were used to analyze the combined effects, Cochrane's Q test and the I2 statistic were applied to determine heterogeneity, sensitivity analysis and subgroup analysis were performed to explore the source of heterogeneity. Literature mining suggests that MCAO-KM brings shorter operation time (p = 0.007), higher probability of plugging filament (p < 0.001) and molding establishment (p = 0.006), lower possibility of subarachnoid hemorrhage (p = 0.02), larger infarct volume (p = 0.003), severer brain edema (p = 0.002), and neurological deficits (p = 0.03). Nevertheless, MCAO-LG shows a more adequate CBF after ischemia-reperfusion (p < 0.001), a higher model survival rate (p = 0.02), and a greater infarct rate (p = 0.007). In conclusion, the MCAO-KM method is simple to operate with a high modeling success rate, and is suitable for the study of brain edema under long-term hypoperfusion, while the MCAO-LG method is highly challenging for novices, and is suitable for the study of CIRI caused by complete ischemia-reperfusion. These findings are expected to benefit the selection of intraluminal filament MCAO models before undertaking ischemic stroke preclinical effectiveness trials.

General Anesthesia Compared With Non-GA in Endovascular Thrombectomy for Ischemic Stroke: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND AND OBJECTIVES

Endovascular thrombectomy (EVT) for large vessel occlusion ischemic stroke is either performed under general anesthesia (GA) or with non-GA techniques such as conscious sedation or local anesthesia alone. Previous small meta-analyses have demonstrated superior recanalization rates and improved functional recovery with GA when compared with non-GA techniques. The publication of further randomized controlled trials (RCTs) could provide updated guidance when choosing between GA and non-GA techniques.

METHODS

A systematic search for trials in which stroke EVT patients were randomized to GA or non-GA was performed in Medline, Embase, and the Cochrane Central Register of Controlled Trials. A systematic review and meta-analysis using a random-effects model was performed.

RESULTS

Seven RCTs were included in the systematic review and meta-analysis. These trials included a total of 980 participants (GA, N = 487; non-GA, N = 493). GA improves recanalization by 9.0% (GA 84.6% vs non-GA 75.6%; odds ratio [OR] 1.75, 95% CI 1.26-2.42, p = 0.0009), and the proportion of patients with functional recovery improves by 8.4% (GA 44.6% vs non-GA 36.2%; OR 1.43, 95% CI 1.04-1.98, p = 0.03). There was no difference in hemorrhagic complications or 3-month mortality.

DISCUSSION

In patients with ischemic stroke treated with EVT, GA is associated with higher recanalization rates and improved functional recovery at 3 months compared with non-GA techniques. Conversion to GA and subsequent intention-to-treat analysis will underestimate the true therapeutic benefit. GA is established as effective in improving recanalization rates in EVT (7 Class 1 studies) with a high Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) certainty rating. GA is established as effective in improving functional recovery at 3 months in EVT (5 Class 1 studies) with a moderate GRADE certainty rating. Stroke services need to develop pathways to incorporate GA as the first choice for most EVT procedures in acute ischemic stroke with a level A recommendation for recanalization and level B recommendation for functional recovery.

Inhalational versus Intravenous General Anesthesia for mechanical thrombectomy for stroke: A single centre retrospective study

BACKGROUND

When general anesthesia is used for endovascular thrombectomy (EVT) for acute ischemic stroke (AIS), the choice of anesthetic agents for maintenance remains inconclusive. The different effects of intravenous anesthetic and volatiles agents on cerebral hemodynamics are known and may explain differences in outcomes of patients with cerebral pathologies exposed to the different anesthetic modalities. In this single institutional retrospective study, we assessed the impact of total intravenous (TIVA) and inhalational anesthesia on outcomes after EVT.

METHODS

We conducted a retrospective analysis of all patients ≥ 18 years who underwent EVT for AIS of the anterior or posterior circulation under general anesthesia. Baseline patient characteristics, anesthetic agents, intra operative hemodynamics, stroke characteristics, time intervals and clinical outcome data were collected and analyzed.

RESULTS

The study cohort consisted of 191 patients. After excluding 76 patients who were lost to follow up at 90 days, 51 patients received inhalational anesthesia and 64 patients who received TIVA were analyzed. The clinical characteristics between the groups were comparable. Multivariate logistic regression analysis of outcome measures for TIVA versus inhalational anesthesia showed significantly increased odds of good functional outcome (mRS 0-2) at 90 days (adjusted odds ratio, 3.24; 95% CI, 1.25-8.36; p = 0.015) and a non-significant trend towards decreased mortality (adjusted odds ratio, 0.73; CI, 0.15-3.6; p = 0.70).

CONCLUSION

Patients who had TIVA for mechanical thrombectomy had significantly increased odds of good functional outcome at 90 days and a non-significant trend towards decrease in mortality. These findings warrant further investigation with large randomized, prospective trials.

A retrospect and outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy

Studies on the neuroprotective effects of anesthetics were carried out more than half a century ago. Subsequently, many cell and animal experiments attempted to verify the findings. However, in clinical trials, the neuroprotective effects of anesthetics were not observed. These contradictory results suggest a mismatch between basic research and clinical trials. The Stroke Therapy Academic Industry Roundtable X (STAIR) proposed that the emergence of endovascular thrombectomy (EVT) would provide a proper platform to verify the neuroprotective effects of anesthetics because the haemodynamics of patients undergoing EVT is very close to the ischaemia–reperfusion model in basic research. With the widespread use of EVT, it is necessary for us to re-examine the neuroprotective effects of anesthetics to guide the use of anesthetics during EVT because the choice of anesthesia is still based on team experience without definite guidelines. In this paper, we describe the research status of anesthesia in EVT and summarize the neuroprotective mechanisms of some anesthetics. Then, we focus on the contradictory results between clinical trials and basic research and discuss the causes. Finally, we provide an outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy.

Assessment of key characteristics, methodology, and effect size measures used in meta-analysis of human-health-related animal studies

Since the early 1990s the number of systematic reviews (SR) of animal studies has steadily increased. There is, however, little guidance on when and how to conduct a meta-analysis of human-health-related animal studies. To gain insight about the methods that are currently used we created an overview of the key characteristics of published meta-analyses of animal studies, with a focus on the choice of effect size measures. An additional goal was to learn about the rationale behind the meta-analysis methods used by the review authors. We show that important details of the meta-analyses are not fully described, only a fraction of all human-health-related meta-analyses provided rationales for their decision to use specific effect size measures. In addition, our data may suggest that authors make post-hoc decisions to switch to another effect size measure during the course of their meta-analysis, and possibly search for significant effects. Based on analyses in this paper we recommend that review teams: 1) publish a review protocol before starting the conduct of a SR, prespecifying all methodological details (providing special attention to the planned meta-analysis including the effect size measure and the rational behind choosing a specific effect size, prespecifying subgroups and restricting the number of subgroup analyses), 2) always use the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) checklist to report your SR of animal studies, and 3) use the random effects model (REM) in human-health-related meta-analysis of animal studies, unless the assumptions for using the fixed effect model (FEM) are all met.

Neuroprotection by the noble gases argon and xenon as treatments for acquired brain injury: a preclinical systematic review and meta-analysis

BACKGROUND

The noble gases argon and xenon are potential novel neuroprotective treatments for acquired brain injuries. Xenon has already undergone early-stage clinical trials in the treatment of ischaemic brain injuries, with mixed results. Argon has yet to progress to clinical trials as a treatment for brain injury. Here, we aim to synthesise the results of preclinical studies evaluating argon and xenon as neuroprotective therapies for brain injuries.

METHODS

After a systematic review of the MEDLINE and Embase databases, we carried out a pairwise and stratified meta-analysis. Heterogeneity was examined by subgroup analysis, funnel plot asymmetry, and Egger's regression.

RESULTS

A total of 32 studies were identified, 14 for argon and 18 for xenon, involving measurements from 1384 animals, including murine, rat, and porcine models. Brain injury models included ischaemic brain injury after cardiac arrest (CA), neurological injury after cardiopulmonary bypass (CPB), traumatic brain injury (TBI), and ischaemic stroke. Both argon and xenon had significant (P<0.001), positive neuroprotective effect sizes. The overall effect size for argon (CA, TBI, stroke) was 18.1% (95% confidence interval [CI], 8.1-28.1%), and for xenon (CA, TBI, stroke) was 34.1% (95% CI, 24.7-43.6%). Including the CPB model, only present for xenon, the xenon effect size (CPB, CA, TBI, stroke) was 27.4% (95% CI, 11.5-43.3%). Xenon, both with and without the CPB model, was significantly (P<0.001) more protective than argon.

CONCLUSIONS

These findings provide evidence to support the use of xenon and argon as neuroprotective treatments for acquired brain injuries. Current evidence suggests that xenon is more efficacious than argon overall.

A Narrative Review on Translational Research in Acute Brain Injury

There has been a constant endeavor to reduce the mortality and morbidity associated with acute brain injury. The associated complex mechanisms involving biomechanics, markers, and neuroprotective drugs/measures have been extensively studied in preclinical studies with an ultimate aim to improve the patients' outcomes. Despite such efforts, only few have been successfully translated into clinical practice. In this review, we shall be discussing the major hurdles in the translation of preclinical results into clinical practice. The need is to choose an appropriate animal model, keeping in mind the species, age, and gender of the animal, choosing suitable outcome measures, ensuring quality of animal trials, and carrying out systematic review and meta-analysis of experimental studies before proceeding to human trials. The interdisciplinary collaboration between the preclinical and clinical scientists will help to design better, meaningful trials which might help a long way in successful translation. Although challenging at this stage, the advent of translational precision medicine will help the integration of mechanism-centric translational medicine and patient-centric precision medicine.

Protective Effects of Remimazolam on Cerebral Ischemia/Reperfusion Injury in Rats by Inhibiting of NLRP3 Inflammasome-Dependent Pyroptosis

INTRODUCTION

Remimazolam is a novel benzodiazepine γ-aminobutyric acid A (GABAa) receptor agonist used for sedation and the induction as well as maintenance of general anesthesia. Previous research proved that anesthetic agents acting on GABAa receptor, such as thiopentone, propofol and midazolam, have protective actions for cerebral ischemia/reperfusion (I/R) injury. We here probed into remimazolam for its protective effect and potential mechanism of action against cerebral I/R injury.

MATERIAL AND METHODS

A rat model of middle cerebral artery occlusion (MCAO) with focal transient cerebral I/R injury was established and was given tail vein injection of gradient remimazolam (5, 10, 20 mg/kg) after 2 h of ischemia. Following 24 h of reperfusion, neurological function, brain infarct volume, morphology of cerebral cortical neurons, and expressions of corticocerebral NLRP3, ASC, caspase-1, GSDMD, IL-1β and IL-18 were evaluated.

RESULTS

The results showed that remimazolam could effectively improve the neurological dysfunction, reduce the infarct volume and alleviate the damage of cortical neurons after I/R injury. Notably, the expression of NLRP3 inflammasome pathway was down-regulated, suggesting that remimazolam exerted protective actions on I/R injury by suppressing pyroptosis with decreased expression and release of inflammatory factors, and the involvement of the NLRP3 inflammasome pathway might be the core during that process. Overall, our results indicate that NLRP3 inflammation is a promising target.

CONCLUSION

Based on this mechanism, remimazolam may be one of the ideal anesthetic drugs for patients with ischemic stroke.

Effect and Mechanisms of Quercetin for Experimental Focal Cerebral Ischemia: A Systematic Review and Meta-Analysis

Quercetin, a naturally occurring flavonoid, is mainly extracted from tea, onions, and apples. It has the underlying neuroprotective effect on experimental ischemic stroke. A systematic review and meta-analysis were used to assess quercetin’s efficacy and possible mechanisms in treating focal cerebral ischemia. Compared with the control group, twelve studies reported a remarkable function of quercetin in improving the neurological function score (NFS) ( $P<0.05$ ), and twelve studies reported a significant effect on reducing infarct volume ( $P<0.05$ ). Moreover, two and three studies showed that quercetin could alleviate blood-brain barrier (BBB) permeability and brain water content, respectively. The mechanisms of quercetin against focal cerebral ischemia are diverse, involving antioxidation, antiapoptotic, anti-inflammation, and calcium overload reduction. On the whole, the present study suggested that quercetin can exert a protective effect on experimental ischemic stroke. Although the effect size may be overestimated because of the quality of studies and possible publication bias, these results indicated that quercetin might be a promising neuroprotective agent for human ischemic stroke. This study is registered with PROSPERO, number CRD 42021275656.

Effect of Thiopental on Ischemic Stroke in Rat Brain in Spontaneously Hypertensive Rats

Motivation and Problem Statement. Thiopental is an anesthetic drug related to the condition of controlling the area of neurological contexts. This study is related to the analysis of effectiveness for the condition of thiopental application on spontaneously hypertensive rats. Methodology. We have evaluated the thiopental induction as the anesthetic agent. The hypertensive rats were selected to administer thiopental in the form of anesthesia. The selection and application of hypertensive strokes are related to the derivation of an inducible model to assess the efficacy for analyzing the ischemic stroke parameters which relate to the human body. We used middle cerebral artery occlusion (MCAO) models related to spontaneous hypertension with the area of examining the complications in ischemic stroke. Results and Conclusion. The study focused on the experimental analysis based on the selection of spontaneously hypertensive rats associated with the incidence of ischemic stroke. Application of thiopental has reported the weak functionality and mechanism on the relaxation of neuronal activity in the case of rat brain. The considered population of the spontaneously hypertensive rats is evaluated based on the condition of effectiveness as well as the duration of the medication effects within the rat brain. Involvement of thiopental in the case of ischemic stroke has provided the area of risk development for high rate of death incidences after occurrence of acute ischemic stroke. A complication in the area of defining neuroprotective actions provides difficulty in drawing an appropriate conclusion of the study.

Neuroprotection by Transcranial Direct Current Stimulation in Rodent Models of Focal Ischemic Stroke: A Meta-Analysis

Infarct size is associated with stroke severity in clinical studies, so reducing it has become an important target and research hotspot in the treatment of ischemic stroke. Some preclinical studies have shown transcranial direct current stimulation (tDCS) reduced infarct size and improved neurological deficit, but others have not found beneficial effects. Besides, the optimal pattern of tDCS for ischemic stroke remains largely unknown. To shed light on the current circumstance and future research directions, the systematic review evaluated the effect of different tDCS paradigms in reducing infarct size and improving neurological deficit in rodent models of ischemic stroke and assessed the methodological quality of current literature. We searched the MEDLINE (via PubMed), EMBASE, Web of Science, and Scopus from their inception to August 18, 2021, to identify studies evaluating the effects of tDCS in rodent models of ischemic stroke. Eight studies were included, of which seven studies were included in the meta-analysis. The results showed cathodal tDCS, rather than anodal tDCS, reduced infarct size mainly measured by tetrazolium chloride and magnetic resonance imaging (standardized mean difference: -1.13; 95% CI: -1.72, -0.53; p = 0.0002) and improved neurological deficit assessed by a modified neurological severity score (standardized mean difference: -2.10; 95% CI: -3.78, -0.42; p = 0.01) in an early stage of focal ischemic stroke in rodent models. Subgroup analyses showed effects of cathodal tDCS on infarct size were not varied by ischemia duration (ischemia for 1, 1.5, and 2 h or permanent ischemia) and anesthesia (involving isoflurane and ketamine). The overall quality of studies included was low, thus the results must be interpreted cautiously. Published studies suggest that cathodal tDCS may be a promising avenue to explore for augmenting rehabilitation from focal ischemic stroke. Considering the methodological limitations, it is unreliable to blindly extrapolate the animal data to the clinical practice. Future research is needed to investigate the mechanism of tDCS in a randomized and blinded fashion in clinically relevant stroke models, such as elderly animals, female animals, and animals with comorbidities, to find an optimal treatment protocol.

Longitudinal cortex-wide monitoring of cerebral hemodynamics and oxygen metabolism in awake mice using multi-parametric photoacoustic microscopy

Multi-parametric photoacoustic microscopy (PAM) has emerged as a promising new technique for high-resolution quantification of hemodynamics and oxygen metabolism in the mouse brain. In this work, we have extended the scope of multi-parametric PAM to longitudinal, cortex-wide, awake-brain imaging with the use of a long-lifetime (24 weeks), wide-field (5 × 7 mm²), light-weight (2 g), dual-transparency (i.e., light and ultrasound) cranial window. Cerebrovascular responses to the window installation were examined in vivo, showing a complete recovery in 18 days. In the 22-week monitoring after the recovery, no dura thickening, skull regrowth, or changes in cerebrovascular structure and function were observed. The promise of this technique was demonstrated by monitoring vascular and metabolic responses of the awake mouse brain to ischemic stroke throughout the acute, subacute, and chronic stages. Side-by-side comparison of the responses in the ipsilateral (injury) and contralateral (control) cortices shows that despite an early recovery of cerebral blood flow and an increase in microvessel density, a long-lasting deficit in cerebral oxygen metabolism was observed throughout the chronic stage in the injured cortex, part of which proceeded to infarction. This longitudinal, functional-metabolic imaging technique opens new opportunities to study the chronic progression and therapeutic responses of neurovascular diseases.

Is General Anesthesia for Endovascular Thrombectomy Helpful or Harmful?

Endovascular thrombectomy (EVT) has significantly improved outcomes for patients with acute ischemic stroke due to large vessel occlusion. However, despite advances, more than half of patients remain functionally dependent 3 months after their initial stroke. Anesthetic strategy may influence both the technical success of the procedure and overall outcomes. Conventionally, general anesthesia (GA) has been widely used for neuroendovascular procedures, particularly for the distal intracranial circulation, because the complete absence of movement has been considered imperative for procedural success and to minimize complications. In contrast, in patients with acute stroke undergoing EVT, the optimal anesthetic strategy is controversial. Nonrandomized studies suggest GA negatively affects outcomes while the more recent anesthesia-specific RCTs report improved or unchanged outcomes in patients managed with versus without GA, although these findings cannot be generalized to other EVT capable centers due to a number of limitations. Potential explanations for these contrasting results will be addressed in this review including the effect of different anesthetic strategies on cerebral and systemic hemodynamics, revascularization times, and periprocedural complications.

General anesthesia during endovascular therapy for acute ischemic stroke: benefits beyond better reperfusion?

BACKGROUND

Endovascular therapy (EVT) is standard of care for stroke caused by large vessel occlusion. Whether EVT should be performed under general anesthesia (GA) or conscious sedation (CS) is controversial. While a meta-analysis of randomized trials showed better outcome for EVT under GA, observational studies suggested the opposite. A proposed advantage of GA is better reperfusion achieved via more successful handling of the immobile patient. The aim of this study was to investigate if the good outcome seen in patients treated under GA was mediated by better reperfusion.

METHODS

The meta-analysis included 368 individual patients from three randomized controlled trials, of whom 185 patients were randomized to CS. A mediator analysis was performed to examine if the better outcome in the GA arm was driven by higher reperfusion rate.

RESULTS

The total effect showed a risk difference (RD) of 0.15 (95% CI 0.04 to 0.25), associating GA with a beneficial outcome. The direct effect of GA constituted a large portion, with an RD of 0.12 (95% CI 0.01 to 0.22), while only a small portion was mediated through the degree of reperfusion, with an RD of 0.03 (95% CI 0.02 to 0.04).

CONCLUSION

The better outcome after EVT in the GA arm was mainly a direct effect-that is, an effect that was not explained by better reperfusion. We also found a better outcome in the GA arm when reperfusion was not achieved. Whether this is an effect of the stable condition and blood pressure under GA or a neuroprotective effect will need to be investigated in future research.

Morphine pretreatment protects against cerebral ischemic injury via a cPKCγ-mediated anti-apoptosis pathway

It has been reported that morphine pretreatment (MP) can exert neuroprotective effects, and that protein kinase C (PKC) participates in the initiation and development of ischemic/hypoxic preconditioning in the brain. However, it remains unknown whether PKC is involved in MP-induced neuroprotection. The aim of the present study, which included in vivo and in vitro experiments, was to determine whether the conventional γ isoform of PKC (cPKCγ) was involved in the protective effects of MP against cerebral ischemic injury. The present study included an in vivo experiment using a mouse model of middle cerebral artery occlusion and an in vitro experiment using neuroblastoma N2a cells with oxygen-glucose deprivation (OGD). Furthermore, a cPKCγ antagonist, Go6983, was used to determine the involvement of cPKCγ in the protective effects of MP against cerebral ischemic injury. In the in vivo experiment, neurological deficits, ischemic infarct volume, neural cell damage, apoptosis and caspase-3 activation were evaluated. In the in vitro experiment, flow cytometry was used to determine the activation of caspase-3 in N2a cells with OGD. It was found that MP protected against cerebral ischemic injury. However, intracerebroventricular injection of the cPKCγ antagonist before MP attenuated the neuroprotective effect of MP and increased the activation of cleaved caspase-3. These findings suggested that MP may provide protection against cerebral ischemic injury via a cPKCγ-mediated anti-apoptosis pathway.

Effect of uric acid in animal models of ischemic stroke: A systematic review and meta-analysis

Addition of uric acid (UA) to thrombolytic therapy, although safe, showed limited efficacy in improving patients' stroke outcome, despite alleged neuroprotective effects of UA in preclinical research. This systematic review assessed the effects of UA on brain structural and functional outcomes in animal models of ischemic stroke. We searched Medline, Embase and Web of Science to identify 16 and 14 eligible rodent studies for qualitative and quantitative synthesis, respectively. Range of evidence met 10 of a possible 13 STAIR criteria. Median (Q1, Q3) quality score was 7.5 (6, 10) on the CAMARADES 15-item checklist. For each outcome, we used standardised mean difference (SMD) as effect size and random-effects modelling. Meta-analysis showed that UA significantly reduced infarct size (SMD: -1.18; 95% CI [-1.47, -0.88]; p < 0.001), blood-brain barrier (BBB) impairment/oedema (SMD: -0.72; 95% CI [-0.97, -0.48]; p < 0.001) and neurofunctional deficit (SMD: -0.98; 95% CI [-1.32, -0.63]; p < 0.001). Overall, there was low to moderate between-study heterogeneity and sizeable publication bias. In conclusion, published rodent data suggest that UA improves outcome following ischemic stroke by reducing infarct size, improving BBB integrity and ameliorating neurofunctional condition. Specific recommendations are given for further high-quality preclinical research required to better inform clinical research.

Intravenous versus Volatile Anesthetic Effects on Postoperative Cognition in Elderly Patients Undergoing Laparoscopic Abdominal Surgery

BACKGROUND

Delayed neurocognitive recovery after surgery is associated with poor outcome. Most surgeries require general anesthesia, of which sevoflurane and propofol are the most commonly used inhalational and intravenous anesthetics. The authors tested the primary hypothesis that patients with laparoscopic abdominal surgery under propofol-based anesthesia have a lower incidence of delayed neurocognitive recovery than patients under sevoflurane-based anesthesia. A second hypothesis is that there were blood biomarkers for predicting delayed neurocognitive recovery to occur.

METHODS

A randomized, double-blind, parallel, controlled study was performed at four hospitals in China. Elderly patients (60 yr and older) undergoing laparoscopic abdominal surgery that was likely longer than 2 h were randomized to a propofol- or sevoflurane-based regimen to maintain general anesthesia. A minimum of 221 patients was planned for each group to detect a one-third decrease in delayed neurocognitive recovery incidence in propofol group compared with sevoflurane group. The primary outcome was delayed neurocognitive recovery incidence 5 to 7 days after surgery.

RESULTS

A total of 544 patients were enrolled, with 272 patients in each group. Of these patients, 226 in the propofol group and 221 in the sevoflurane group completed the needed neuropsychological tests for diagnosing delayed neurocognitive recovery, and 46 (20.8%) in the sevoflurane group and 38 (16.8%) in the propofol group met the criteria for delayed neurocognitive recovery (odds ratio, 0.77; 95% CI, 0.48 to 1.24; P = 0.279). A high blood interleukin-6 concentration at 1 h after skin incision was associated with an increased likelihood of delayed neurocognitive recovery (odds ratio, 1.04; 95% CI, 1.01 to 1.07; P = 0.007). Adverse event incidences were similar in both groups.

CONCLUSIONS

Anesthetic choice between propofol and sevoflurane did not appear to affect the incidence of delayed neurocognitive recovery 5 to 7 days after laparoscopic abdominal surgery. A high blood interleukin-6 concentration after surgical incision may be an independent risk factor for delayed neurocognitive recovery.

EDITOR’S PERSPECTIVE

Effects of Volatile Anesthetics on Postoperative Ischemic Stroke Incidence

Background

Preclinical studies suggest that volatile anesthetics decrease infarct volume and improve the outcome of ischemic stroke. This study aims to determine their effect during noncardiac surgery on postoperative ischemic stroke incidence.

Methods and Results

This was a retrospective cohort study of surgical patients undergoing general anesthesia at 2 tertiary care centers in Boston, MA, between October 2005 and September 2017. Exclusion criteria comprised brain death, age <18 years, cardiac surgery, and missing covariate data. The exposure was defined as median age‐adjusted minimum alveolar concentration of all intraoperative measurements of desflurane, sevoflurane, and isoflurane. The primary outcome was postoperative ischemic stroke within 30 days. Among 314 932 patients, 1957 (0.6%) experienced the primary outcome. Higher doses of volatile anesthetics had a protective effect on postoperative ischemic stroke incidence (adjusted odds ratio per 1 minimum alveolar concentration increase 0.49, 95% CI, 0.40–0.59, P<0.001). In Cox proportional hazards regression, the effect was observed for 17 postoperative days (postoperative day 1: hazard ratio (HR), 0.56; 95% CI, 0.48–0.65; versus day 17: HR, 0.85; 95% CI, 0.74–0.99). Volatile anesthetics were also associated with lower stroke severity: Every 1‐unit increase in minimum alveolar concentration was associated with a 0.006‐unit decrease in the National Institutes of Health Stroke Scale (95% CI, −0.01 to −0.002, P=0.002). The effects were robust throughout various sensitivity analyses including adjustment for anesthesia providers as random effect.

Conclusions

Among patients undergoing noncardiac surgery, volatile anesthetics showed a dose‐dependent protective effect on the incidence and severity of early postoperative ischemic stroke.

Neuroprotection by Remote Ischemic Conditioning in Rodent Models of Focal Ischemia: a Systematic Review and Meta-Analysis

Remote ischemic conditioning (RIC) is a promising neuroprotective therapy for ischemic stroke. Preclinical studies investigating RIC have shown RIC reduced infarct volume, but clinical trials have been equivocal. Therefore, the efficacy of RIC in reducing infarct volume and quality of current literature needs to be evaluated to identify knowledge gaps to support future clinical trials. We performed a systematic review and meta-analysis of preclinical literature involving RIC in rodent models of focal ischemia. This review was registered with PROSPERO (CRD42019145441). Eligibility criteria included rat or mice models of focal ischemia that received RIC to a limb either before, during, or after stroke. MEDLINE and Embase databases were searched from 1946 to August 2019. Risk of bias was assessed using the SYRCLE risk of bias tool along with construct validity. Seventy-two studies were included in the systematic review. RIC was shown to reduce infarct volume (SMD - 2.19; CI - 2.48 to - 1.91) when compared to stroke-only controls and no adverse events were reported with regard to RIC. Remote ischemic conditioning was shown to be most efficacious in males (SMD - 2.26; CI - 2.58 to - 1.94) and when delivered poststroke (SMD - 1.34; CI - 1.95 to - 0.73). A high risk of bias was present; thus, measures of efficacy may be exaggerated. A limitation is the poor methodological reporting of many studies, resulting in unclear construct validity. We identified several important, but under investigated topics including the efficacy of RIC in different stroke models, varied infarct sizes and location, and potential sex differences.

Brief inhalation of sevoflurane can reduce glial scar formation after hypoxic-ischemic brain injury in neonatal rats

Previous studies have demonstrated that sevoflurane postconditioning can provide neuroprotection after hypoxic-ischemic injury and improve learning and memory function in developing rodent brains. The classical Rice-Vannucci model was used to induce hypoxic-ischemic injury, and newborn (postnatal day 7) rats were treated with 2.4% sevoflurane for 30 minutes after hypoxic-ischemic injury. Our results showed that sevoflurane postconditioning significantly improved the learning and memory function of rats, decreased astrogliosis and glial scar formation, increased numbers of dendritic spines, and protected the histomorphology of the hippocampus. Mechanistically, sevoflurane postconditioning decreased expression of von Hippel-Lindau of hypoxia-inducible factor-1α and increased expression of DJ-1. Injection of 1.52 μg of the hypoxia-inducible factor-1α inhibitor YC-1 (Lificiguat) into the left lateral ventricle 30 minutes before hypoxic-ischemic injury reversed the neuroprotection induced by sevoflurane. This finding suggests that sevoflurane can effectively alleviate astrogliosis in the hippocampus and reduce learning and memory impairments caused by glial scar formation after hypoxic-ischemic injury. The underlying mechanism may be related to upregulated DJ-1 expression, reduced ubiquitination of hypoxia-inducible factor-1α, and stabilized hypoxia-inducible factor-1α expression. This study was approved by the Laboratory Animal Care Committee of China Medical University, China (approval No. 2016PS337K) on November 9, 2016.

General Anesthesia Versus Conscious Sedation in Endovascular Thrombectomy for Stroke: A Meta-analysis of 4 Randomized Controlled Trials

BACKGROUND

In ischemic stroke patients, studies have suggested that clinical outcomes following endovascular thrombectomy are worse after general anesthesia (GA) compared with conscious sedation (CS). Most data are from observational trials, which are prone to measure and unmeasure confounding. We performed a systematic review and meta-analysis of thrombectomy trials where patients were randomized to GA or CS, and compared efficacy and safety outcomes.

METHODS

The Medline, Embase, and Cochrane databases were searched for randomized controlled trials comparing GA to CS in endovascular thrombectomy. Efficacy outcomes included successful recanalization (Thrombolysis in Cerebral Infarction score of 2b to 3), and good functional outcome, defined as a modified Rankin Scale score of 0 to 2 at 3 months. Safety outcomes included intracerebral hemorrhage and 3-month mortality.

RESULTS

Four studies were identified and included in the random effects meta-analysis. Patients treated with GA achieved a higher proportion of successful recanalization (odds ratio [OR]: 2.14, 95% confidence interval [CI]: 1.26-3.62; P=0.005) and good functional outcome (OR: 1.71, 95% CI: 1.13-2.59; P=0.01). For every 7.9 patients receiving GA, one more achieved good functional outcome compared with those receiving CS. There were no significant differences in intracerebral hemorrhage (OR: 0.61, 95% CI: 0.20-1.85; P=0.38) or 3-month mortality (OR: 0.62, 95% CI: 0.33-1.17; P=0.14) between GA and CS patients.

CONCLUSIONS

In centers with high quality, specialized neuroanesthesia care, GA treated thrombectomy patients had superior recanalization rates and better functional outcome at 3 months than patients receiving CS.

Intravenous Propofol Versus Volatile Anesthetics For Stroke Endovascular Thrombectomy

BACKGROUND

The choice of anesthetic technique for ischemic stroke patients undergoing endovascular thrombectomy is controversial. Intravenous propofol and volatile inhalational general anesthetic agents have differing effects on cerebral hemodynamics, which may affect ischemic brain tissue and clinical outcome. We compared outcomes in patients undergoing endovascular thrombectomy with general anesthesia who were treated with propofol or volatile agents.

METHODS

Consecutive endovascular thrombectomy patients treated using general anesthesia were identified from our prospective database. Baseline patient characteristics, anesthetic agent, and clinical outcomes were recorded. Functional independence at 3 months was defined as a modified Rankin Scale of 0 to 2.

RESULTS

There were 313 patients (182 [58.1%] men; mean±SD age, 64.7±15.9 y; 257 [82%] anterior circulation), of whom 254 (81%) received volatile inhalational (desflurane or sevoflurane), and 59 (19%) received intravenous propofol general anesthesia. Patients with propofol anesthesia had more ischemic heart disease, higher baseline National Institutes of Health Stroke Scale scores, more basilar artery occlusion, and were less likely to be treated with intravenous thrombolysis. Multivariable logistic regression analysis showed that propofol anesthesia was associated with improved functional independence at 3 months (odds ratio=2.65; 95% confidence interval, 1.14-6.22; P=0.03) and a nonsignificant trend toward reduced 3-month mortality (odds ratio=0.37; 95% CI, 0.12-1.10; P=0.07).

CONCLUSION

In stroke patients undergoing endovascular thrombectomy treated using general anesthesia, there may be a differential effect between intravenous propofol and volatile inhalational agents. These results should be considered hypothesis-generating and be tested in future randomized controlled trials.

Animal models of cerebral ischemia: A review

Stroke seriously threatens human health because of its characteristics of high morbidity, disability, recurrence, and mortality, thus representing a heavy financial and mental burden to affected families and society. Many preclinical effective drugs end in clinical-translation failure. Animal models are an important approach for studying diseases and drug effects, and play a central role in biomedical research. Some details about animal models of cerebral ischemia have not been published, such as left-/right-sided lesions or permanent cerebral ischemia/cerebral ischemia-reperfusion. In this review, ischemia in the left- and right-hemisphere in patients with clinical stroke and preclinical studies were compared for the first time, as were the mechanisms of permanent cerebral ischemia and cerebral ischemia-reperfusion in different phases of the disease. The results showed that stroke in the left hemisphere was more common in clinical patients, and that most patients with stroke failed to achieve successful recanalization. Significant differences were detected between permanent cerebral ischemia and cerebral ischemia-reperfusion models in the early, subacute, and recovery phases. Therefore, it is recommended that, with the exception of the determined experimental purpose or drug mechanism, left-sided permanent cerebral ischemia animal models should be prioritized, as they would be more in line with the clinical scenario and would promote clinical translation. In addition, other details regarding the preoperative management, surgical procedures, and postoperative care of these animals are provided, to help establish a precise, effective, and reproducible model of cerebral ischemia model and establish a reference for researchers in this field.

Ischemic stroke and mitochondria: mechanisms and targets

Stroke is one of the main causes of mortality and disability in most countries of the world. The only way of managing patients with ischemic stroke is the use of intravenous tissue plasminogen activator and endovascular thrombectomy. However, very few patients receive these treatments as the therapeutic time window is narrow after an ischemic stroke. The paucity of stroke management approaches can only be addressed by identifying new possible therapeutic targets. Mitochondria have been a rare target in the clinical management of stroke. Previous studies have only investigated the bioenergetics and apoptotic roles of this organelle; however, the mitochondrion is now considered as a key organelle that participates in many cellular and molecular functions. This review discusses the mitochondrial mechanisms in cerebral ischemia such as its role in reactive oxygen species (ROS) generation, apoptosis, and electron transport chain dysfunction. Understanding the mechanisms of mitochondria in neural cell death during ischemic stroke might help to design new therapeutic targets for ischemic stroke as well as other neurological diseases.

The collagenase model of intracerebral hemorrhage in awake, freely moving animals: The effects of isoflurane

Intracerebral hemorrhage (ICH) is a devastating stroke often modelled in rats. Isoflurane anesthetic, commonly used in preclinical research, affects general physiology (e.g., blood pressure) and electrophysiology (e.g., burst suppression) in many ways. These physiological changes may detract from the clinical relevance of the model. Here, we revised the standard collagenase model to produce an ICH in rats without anesthetic. Guide cannulas were implanted stereotaxically under anesthetic. After 3 days of recovery, collagenase was infused through an internal cannula into the striatum of animals randomly assigned to the non-anesthetized or isoflurane group. We assessed whether isoflurane affected hematoma volume, core temperature, movement activity, pain, blood pressure, and seizure activity. With a small ICH, there was a hematoma volume increased from 8.6 (±3.3, 95% confidence interval) µL in anesthetized rats to 13.2 (±3.1) µL in non-anesthetized rats (P = 0.008), but with a larger ICH, hematoma volumes were similar. Isoflurane decreased temperature by 1.3 °C (±0.16 °C, P < 0.001) for 2 h and caused a 35.1 (±1.7) mmHg group difference in blood pressure (P < 0.007) for 12 m. Blood glucose increased twofold after isoflurane procedures (P < 0.001). Pain, as assessed with the rat grimace scale, did not differ between groups. Seizure incidence rate (62.5%) in non-anesthetized ICH rats was similar to historic amounts (61.3%). In conclusion, isoflurane appears to have some significant and injury size-dependent effects on the collagenase model. Thus, when anesthetic effects are a known concern, the use of the standardized cannula infusion approach is scientifically and ethically acceptable.

The influence of anesthetics on substantia nigra tyrosine hydroxylase expression and tau phosphorylation in the hypoxic-ischemic near-term lamb

BackgroundGeneral anesthetics could protect key neurotransmitter systems, such as the dopaminergic system, from hypoxic-ischemic encephalopathy (HIE) by limiting excessive glutamatergic neurotransmission. However, anesthetics may adversely affect inflammation and tau phosphorylation.MethodsA near-term sheep model of HIE by umbilical cord occlusion (UCO) under anesthesia was used. The effect of propofol and isoflurane on the dopaminergic neurotransmitter phenotype in the substantia nigra (SN) was studied using tyrosine hydroxylase immunohistochemistry. The overall microglial response and tau phosphorylation were also measured in the SN, surrounding the midbrain gray matter structures and the hippocampal white matter.ResultsThe isoflurane-treated UCO group had fewer tyrosine hydroxylase-expressing neurons in the SN at 8 h after the insult than the propofol-treated UCO or sham-operated groups (P<0.05). The microglial response was unchanged in the SN region. In the thalamus and the hippocampal stratum moleculare layer, the propofol-treated UCO group had a lower microglial response than the corresponding sham-operated group. Both UCO and the use of anesthetics additively increased tau phosphorylation in the SN region, thalamus, and hippocampus.ConclusionThe choice of anesthetics is important for an emergency C-section. Propofol could potentially protect the dopaminergic neurotransmitter phenotype within the SN at the cost of a widespread increase in tau phosphorylation.

General anesthetics protects against cardiac arrest-induced brain injury by inhibiting calcium wave propagation in zebrafish

Cardiac arrest is a leading cause of death and disability worldwide. Although many victims are initially resuscitated, they often suffer from serious brain injury, even leading to a “persistent vegetative state”. Therefore, it is need to explore therapies which restore and protect brain function after cardiac arrest. In the present study, using Tg (HuC:GCaMP5) zebrafish as a model, we found the zebrafish brain generated a burst of Ca²⁺ wave after cardiac arrest by in vivo time-lapse confocal imaging. The Ca²⁺ wave was firstly initiated at hindbrain and then sequentially propagated to midbrain and telencephalon, the neuron displayed Ca²⁺ overload after Ca²⁺ wave propagation. Consistent with this, our study further demonstrated neuronal apoptosis was increased in cardiac arrest zebrafish by TUNEL staining. The cardiac arrest-induced Ca²⁺ wave propagation can be prevented by general anesthetics such as midazolam or ketamine pretreatment. Moreover, midazolam or ketamine pretreatment dramatically decreased the neuronal apoptosis and improved the survival rate in CA zebrafish. Taken together, these findings provide the first in vivo evidence that general anesthetics pretreatment protects against cardiac arrest-induced brain injury by inhibiting calcium wave propagation in zebrafish.