Timing of stroke after cardiopulmonary bypass determines mortality

Endovascular Treatment of Acute Ischemic Stroke After Cardiac Interventions in the United States

Importance

Ischemic stroke is a serious complication of cardiac intervention, including surgery and percutaneous procedures. Endovascular thrombectomy (EVT) is an effective treatment for ischemic stroke and may be particularly important for cardiac intervention patients who often cannot receive intravenous thrombolysis.

Objective

To examine trends in EVT for ischemic stroke during hospitalization of patients with cardiac interventions vs those without in the United States.

Design, Setting, and Participants

This cohort study involved a retrospective analysis using data for 4888 US hospitals from the 2016-2020 National Inpatient Sample database. Participants included adults (age ≥18 years) with ischemic stroke (per codes from the International Statistical Classification of Diseases, Tenth Revision, Clinical Modification), who were organized into study groups of hospitalized patients with cardiac interventions vs without. Individuals were excluded from the study if they had either procedure prior to admission, EVT prior to cardiac intervention, EVT more than 3 days after admission or cardiac intervention, or endocarditis. Data were analyzed from April 2023 to October 2023.

Exposures

Cardiac intervention during admission.

Main Outcomes and Measures

The odds of undergoing EVT by cardiac intervention status were calculated using multivariable logistic regression. Adjustments were made for stroke severity in the subgroup of patients who had a National Institutes of Health Stroke Scale (NIHSS) score documented. As a secondary outcome, the odds of discharge home by EVT status after cardiac intervention were modeled.

Results

Among 634 407 hospitalizations, the mean (SD) age of the patients was 69.8 (14.1) years, 318 363 patients (50.2%) were male, and 316 044 (49.8%) were female. A total of 12 093 had a cardiac intervention. An NIHSS score was reported in 218 576 admissions, 216 035 (34.7%) without cardiac intervention and 2541 (21.0%) with cardiac intervention (P < .001). EVT was performed in 23 660 patients (3.8%) without cardiac intervention vs 194 (1.6%) of those with cardiac intervention (P < .001). After adjustment for potential confounders, EVT was less likely to be performed in stroke patients with cardiac intervention vs those without (adjusted odds ratio [aOR], 0.27; 95% CI, 0.23-0.31), which remained consistent after adjusting for NIHSS score (aOR, 0.28; 95% CI, 0.22-0.35). Among individuals with a cardiac intervention, receiving EVT was associated with a 2-fold higher chance of discharge home (aOR, 2.21; 95% CI, 1.14-4.29).

Conclusions and Relevance

In this study, patients hospitalized with ischemic stroke and cardiac intervention may be less than half as likely to receive EVT as those without cardiac intervention. Given the known benefit of EVT, there is a need to better understand the reasons for lower rates of EVT in this patient population.

Interpretable machine learning-based predictive modeling of patient outcomes following cardiac surgery

BACKGROUND

The clinical applicability of machine learning predictions of patient outcomes following cardiac surgery remains unclear. We applied machine learning to predict patient outcomes associated with high morbidity and mortality after cardiac surgery and identified the importance of variables to the derived model's performance.

METHODS

We applied machine learning to the Society of Thoracic Surgeons Adult Cardiac Surgery Database to predict postoperative hemorrhage requiring reoperation, venous thromboembolism (VTE), and stroke. We used permutation feature importance to identify variables important to model performance and a misclassification analysis to study the limitations of the model.

RESULTS

The study dataset included 662,772 subjects who underwent cardiac surgery between 2015 and 2017 and 240 variables. Hemorrhage requiring reoperation, VTE, and stroke occurred in 2.9%, 1.2%, and 2.0% of subjects, respectively. The model performed remarkably well at predicting all 3 complications (area under the receiver operating characteristic curve, 0.92-0.97). Preoperative and intraoperative variables were not important to model performance; instead, performance for the prediction of all 3 outcomes was driven primarily by several postoperative variables, including known risk factors for the complications, such as mechanical ventilation and new onset of postoperative arrhythmias. Many of the postoperative variables important to model performance also increased the risk of subject misclassification, indicating internal validity.

CONCLUSIONS

A machine learning model accurately and reliably predicts patient outcomes following cardiac surgery. Postoperative, as opposed to preoperative or intraoperative variables, are important to model performance. Interventions targeting this period, including minimizing the duration of mechanical ventilation and early treatment of new-onset postoperative arrhythmias, may help lower the risk of these complications.

Synapomorphic features of hepatic and pulmonary vasculatures include comparable purinergic signaling responses in host defense and modulation of inflammation

Hepatosplanchnic and pulmonary vasculatures constitute synapomorphic, highly comparable networks integrated with the external environment. Given functionality related to obligatory requirements of "feeding and breathing," these organs are subject to constant environmental challenges entailing infectious risk, antigenic and xenobiotic exposures. Host responses to these stimuli need to be both protective and tightly regulated. These functions are facilitated by dualistic, high-low pressure blood supply of the liver and lungs, as well as tolerogenic characteristics of resident immune cells and signaling pathways. Dysregulation in hepatosplanchnic and pulmonary blood flow, immune responses, and microbiome implicate common pathogenic mechanisms across these vascular networks. Hepatosplanchnic diseases, such as cirrhosis and portal hypertension, often impact lungs and perturb pulmonary circulation and oxygenation. The reverse situation is also noted with lung disease resulting in hepatic dysfunction. Others, and we, have described common features of dysregulated cell signaling during liver and lung inflammation involving extracellular purines (e.g., ATP, ADP), either generated exogenously or endogenously. These metabokines serve as danger signals, when released by bacteria or during cellular stress and cause proinflammatory and prothrombotic signals in the gut/liver-lung vasculature. Dampening of these danger signals and organ protection largely depends upon activities of vascular and immune cell-expressed ectonucleotidases (CD39 and CD73), which convert ATP and ADP into anti-inflammatory adenosine. However, in many inflammatory disorders involving gut, liver, and lung, these protective mechanisms are compromised, causing perpetuation of tissue injury. We propose that interventions that specifically target aberrant purinergic signaling might prevent and/or ameliorate inflammatory disorders of the gut/liver and lung axis.

Anticoagulation and amiodarone for new atrial fibrillation after coronary artery bypass grafting: Prescription patterns and 30-day outcomes in the United States and Canada

OBJECTIVE

We sought to elucidate national practice patterns regarding anticoagulation and antiarrhythmic medication use at discharge and examine short-term patient outcomes.

METHODS

In this retrospective cohort study, we analyzed the data of patients from the Society of Thoracic Surgeons Adult Cardiac Surgery Database from July 2011 to June 2018 who underwent first-time isolated coronary artery bypass graft surgery (CABG) and developed new post-CABG atrial fibrillation (AF) without significant complications. In total, 166,747 patients met study criteria. We examined 30-day outcomes.

RESULTS

In total, 166,747 patients were analyzed and divided into 4 groups based on discharge medications: amiodarone with or without anticoagulation, anticoagulation alone, and neither. Demographic characteristics were similar among the 4 groups. In total, 25.7% of patients were discharged on anticoagulation with an average CHA2DS2-VASc score of 3.2 ± 1.3. Anticoagulation use at discharge was not associated with lower 30-day stroke readmissions (adjusted odds ratio [AOR], 0.87; 95% confidence interval [CI], 0.65-1.16; P = .35). Adjusted 30-day readmissions for major bleeding were significantly more common in anticoagulated patients (AOR, 4.30; 95% CI, 3.69-5.03; P < .0001). Among those discharged off anticoagulation, there was no significant difference in adjusted 30-day stroke rates based on amiodarone use at discharge (AOR, 1.19; 95% CI, 0.85-1.66; P = .31).

CONCLUSIONS

Post-CABG anticoagulation for new AF is associated with increased bleeding and no difference in stroke at 30 days. Prospective randomized studies are needed to formalize safe and efficacious short- and long-term management strategies.

Cerebral microemboli in mini-sternotomy compared to mini- thoracotomy for aortic valve replacement: a cross sectional cohort study

Background

Recently adopted mini-thoracotomy approach for surgical aortic valve replacement has shown benefits such as reduced pain and shorter recovery, compared to more conventional mini-sternotomy access. However, whether limited exposure of the heart and ascending aorta resulting from an incision in the second intercostal space may lead to increased intraoperative cerebral embolization and more prominent postoperative neurologic decline, remains inconclusive. The aim of our study was to assess potential neurological complications after two different minimal invasive surgical techniques for aortic valve replacement by measuring cerebral microembolic signal during surgery and by follow-up cognitive evaluation.

Methods

Trans-cranial Doppler was used for microembolic signal detection during aortic valve replacement performed via mini-sternotomy and mini-thoracotomy. Patients were evaluated using Addenbrooke’s Cognitive Examination Revised Test before and 30 days after surgical procedure.

Results

A total of 60 patients were recruited in the study. In 52 patients, transcranial Doppler was feasible. Of those, 25 underwent mini-sternotomy and 27 had mini-thoracotomy. There were no differences between groups with respect to sex, NYHA class distribution, Euroscore II or aortic valve area. Patients in mini-sternotomy group were younger (60.8 ± 14.4 vs.72 ± 5.84, p = 0.003), heavier (85.2 ± 12.4 vs.72.5 ± 12.9, p = 0.002) and had higher body surface area (1.98 ± 0.167 vs. 1.83 ± 0.178, p = 0.006). Surgery duration was longer in mini-sternotomy group compared to mini-thoracotomy (158 ± 24 vs. 134 ± 30 min, p < 0.001, respectively). There were no differences between groups in microembolic load, length of ICU or total hospital stay. Total microembolic signals count was correlated with cardiopulmonary bypass duration (5.64, 95%CI 0.677–10.60, p = 0.027). Addenbrooke’s Cognitive Examination Revised Test score decreased equivalently in both groups (p = 0.630) (MS: 85.2 ± 9.6 vs. 82.9 ± 11.4, p = 0.012; MT: 85.2 ± 9.6 vs. 81.3 ± 8.8, p = 0.001).

Conclusion

There is no difference in microembolic load between the groups. Total intraoperative microembolic signals count was associated with cardiopulmonary bypass duration. Age, but not micorembolic signals load, was associated with postoperative neurologic decline.

Trial registry number

clinicaltrials.gov, NCT02697786 14.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-021-01509-8.

Factors associated with long-term survival in patients with stroke after coronary artery bypass grafting

Objective

Occurrence of a stroke within 30 days following coronary artery bypass grafting (CABG) is an uncommon, but often devastating, complication. This study aimed to identify factors associated with long-term survival (beyond 30 days) in patients with stroke after CABG.

Methods

De-identified patients’ records from the Veterans Affairs Surgical Quality Improvement Program database were used to identify risk factors and perioperative complications associated with survival for up to 20 years in patients with post-CABG stroke. The multivariable Cox proportional hazards model was used for analyzing survival.

Results

The median survival time for patients with stroke (n = 1422) was 6.7 years. The mortality rate for these patients was highest in the first year post-CABG and was significantly elevated compared with non-stroke patients. Survival rates at 1, 5, and 10 years for stroke versus non-stroke patients were 79% vs. 96%, 58% vs. 83%, and 36% vs. 63%, respectively. High preoperative serum creatinine levels, postoperative occurrence of renal failure, prolonged ventilation, coma, and reoperation for bleeding were important predictors of 1-year mortality of patients with post-CABG stroke.

Conclusions

Veterans with post-CABG stroke have a considerably higher risk for mortality during the first year compared with patients without stroke.

Significant aortic stenosis associated with poorer functional outcomes in patients with acute ischaemic stroke undergoing endovascular therapy

BACKGROUND AND AIM

Bi-directional feedback mechanisms exist between the heart and brain, which have been implicated in heart failure. We postulate that aortic stenosis may alter cerebral haemodynamics and influence functional outcomes after endovascular thrombectomy for acute ischaemic stroke. We compared clinical characteristics, echocardiographic profile and outcomes in patients with or without aortic stenosis that underwent endovascular thrombectomy for large vessel occlusion acute ischaemic stroke.

METHODS

Consecutive acute ischaemic stroke patients with anterior and posterior circulation large vessel occlusion (internal carotid artery, middle cerebral artery and basilar artery) who underwent endovascular thrombectomy were studied. Patients were divided into those with significant aortic stenosis (aortic valve area <1.5 cm2) and without. Univariate and multivariate analyses were employed to compare and determine predictors of functional outcomes measured by modified Rankin scale at three months.

RESULTS

We identified 26 (8.5%) patients with significant aortic stenosis. These patients were older (median age 76 (interquartile range 68-84) vs. 67 (interquartile range 56-75) years, p = 0.001), but similar in terms of medical comorbidities and echocardiographic profile. Rates of successful recanalisation (73.1% vs. 78.0%), symptomatic intracranial haemorrhage (7.7% and 7.9%) and mortality (11.5% vs. 12.6%) were similar. Significant aortic stenosis was independently associated with poorer functional outcome (modified Rankin scale >2) at three months (adjusted odds ratio 2.7, 95% confidence interval 1.1-7.5, p = 0.048), after adjusting for age, door-to-puncture times, stroke severity and rates of successful recanalisation.

CONCLUSION

In acute ischaemic stroke patients managed with endovascular thrombectomy, significant aortic stenosis is associated with poor functional outcome despite comparable recanalisation rates. Larger cohort studies are needed to explore this relationship further.

Early Versus Delayed Stroke After Cardiac Surgery: A Systematic Review and Meta-Analysis

Background Although it is traditionally regarded as a single entity, perioperative stroke comprises 2 separate phenomena (early/intraoperative and delayed/postoperative stroke). We aimed to systematically evaluate incidence, risk factors, and clinical outcome of early and delayed stroke after cardiac surgery. Methods and Results A systematic review ( MEDLINE , EMBASE , Cochrane Library) was performed to identify all articles reporting early (on awakening from anesthesia) and delayed (after normal awakening from anesthesia) stroke after cardiac surgery. End points were pooled event rates of stroke and operative mortality and incident rate of late mortality. Thirty-six articles were included (174 969 patients). The pooled event rate for early stroke was 0.98% (95% CI 0.79% to 1.23%) and was 0.93% for delayed stoke (95% CI 0.77% to 1.11%; P=0.68). The pooled event rate of operative mortality was 28.8% (95% CI 17.6% to 43.4%) for early and 17.9% (95% CI 14.0% to 22.7%) for delayed stroke, compared with 2.4% (95% CI 1.9% to 3.1%) for patients without stroke ( P<0.001 for early versus delayed, and for perioperative stroke, early stroke, and delayed stroke versus no stroke). At a mean follow-up of 8.25 years, the incident rate of late mortality was 11.7% (95% CI 7.5% to 18.3%) for early and 9.4% (95% CI 5.9% to 14.9%) for delayed stroke, compared with 3.4% (95% CI 2.4% to 4.8%) in patients with no stroke. Meta-regression demonstrated that off-pump was inversely associated with early stroke (β=-0.009, P=0.01), whereas previous stroke (β=0.02, P<0.001) was associated with delayed stroke. Conclusions Early and delayed stroke after cardiac surgery have different risk factors and impacts on operative mortality as well as on long-term survival.

Retrospective Analysis of Air Handling by Contemporary Oxygenators in the Setting of Cardiac Surgery

Purpose: Cardiac surgery with the use of extracorporeal circulation is associated with a significant risk for gaseous microemboli (GME) despite excellent surgical techniques and highest operative standards. GME are associated with postoperative neurocognitive dysfunction and negative clinical outcome. This study determines whether oxygenator design has influence on perioperative outcome after cardiac surgery.

Methods: Three different oxygenator models with integrated arterial filter (HiliteAF 7000, Fusion Affinity, and Synthesis) were retrospectively evaluated in 55 patients undergoing elective cardiac surgery with the use of extracorporeal circulation. The two-channel ultrasound bubble counter BCC200 was used to detect GME in real time.

Results: All three oxygenators differ in terms of structural specifications and have different rates of number and volume GME reduction. The Fusion Affinity had the lowest arterial GME volume (1.81 µL ± 0.23 µL), which was statistically significant compared to the Synthesis (3.37 µL ± 0.71 µL, p = 0.014). However, the Synthesis had lower absolute numbers at the venous GME count (31771 µL ± 6579 µL) versus the Fusion Affinity (49304 µL ± 8196 µL). However, with regard to clinical outcome after cardiac surgery (duration of invasive and non-invasive mechanical ventilation, incidence of delirium, stroke, acute renal failure, or new myocardial infarction), we found no differences between groups.

Conclusion: Despite significant differences in the design specifications, all oxygenators eliminated relevant GME volumes safely.

A model-based cost-effectiveness analysis of Patient Blood Management

BACKGROUND

Patient blood management (PBM) is a multidisciplinary concept focused on the management of anaemia, minimisation of iatrogenic blood loss and rational use of allogeneic blood products. The aims of this study were: (i) to analyse post-operative outcome in patients with liberal vs restrictive exposure to allogeneic blood products and (ii) to evaluate the cost-effectiveness of PBM in patients undergoing surgery.

MATERIALS AND METHODS

A systematic literature review and meta-analysis were performed to compare post-operative complications in predominantly non-transfused patients (restrictive transfusion group) and patients who received one to three units of red blood cells (liberal transfusion group). Outcome measures included sepsis with/without pneumonia, acute renal failure, acute myocardial infarction and acute stroke. In a second step, a health economic model was developed to calculate cost-effectiveness of PBM (PBM-arm vs control-arm) for simulated cohorts of 10,000 cardiac and non-cardiac surgical patients based on the results of the meta-analysis and costs.

RESULTS

Out of 478 search results, 22 studies were analysed in the meta-analysis. The pooled relative risk of any complication in the restrictive transfusion group was 0.43 for non-cardiac and 0.34 for cardiac surgical patients. In the simulation model, PBM was related to reduced complications (1,768 vs 1,245) and complication-related deaths (411 vs 304) compared to standard care. PBM-related costs of therapy exceeded costs of the control arm by € 150 per patient. However, total costs, including hospitalisation, were higher in the control-arm for both non-cardiac (€ 2,885.11) and cardiac surgery patients (€ 1,760.69). The incremental cost-effectiveness ratio including hospitalisation showed savings of € 30,458 (non-cardiac and cardiac surgery patients) for preventing one complication and € 128,023 (non-cardiac and cardiac surgery patients) for prevention of one complication-related death in the PBM-arm.

DISCUSSION

Our results indicate that PBM may be associated with fewer adverse clinical outcomes compared to control management and may, thereby, be cost-effective.

Perioperative stroke as a predictor of mortality and morbidity in patients undergoing CABG

Perioperative stroke is a devastating neurological complication of Coronary Artery Bypass Grafting surgery (CABG). It results in significantly increased rates of mortality and morbidity and presents a significant financial burden to our healthcare system. It has not, however, been studied in a large population based sample. We aim to investigate the role of perioperative stroke as an independent risk factor for in-hospital mortality and morbidity following CABG, and to review trends in the early outcomes of CABG from the years 1999 to 2011. We hypothesize that perioperative stroke is an independent risk factor for in-hospital mortality and morbidity following CABG. We analyzed data from the 1999-2011 Nationwide Inpatient Sample, identifying patients who underwent CABG using ICD-9 and CCS codes. We excluded patients below the age of 18 and above the age of 100, and patients undergoing concomitant heart and/or vascular procedures. Analysis on our sample of 668,627 patients yielded an overall rate of perioperative stroke, mortality, and morbidity of 1.87%, 2.13%, and 49.07%, respectively. Along with age, risk category, gender, and other postoperative outcomes, perioperative stroke was found to be a strong predictor of mortality and morbidity, leading to more than a 5-fold risk of death and morbidity. From our study, we conclude that perioperative stroke remains a serious adverse outcome of CABG and is an independent predictor of mortality and morbidity. While rates of stroke and mortality are decreasing, morbidity continues to trend upwards. This study emphasizes the importance of prevention and early intervention in patients at risk for perioperative stroke.

Sonolysis in Prevention of Brain Infarction During Cardiac Surgery (SONORESCUE): Randomized, Controlled Trial

Here, we examined whether intraoperative sonolysis can alter the risk of new ischemic lesions in the insonated brain artery territory during coronary artery bypass grafting (CABG) or valve surgery.Silent brain ischemic lesions could be detected in as many as two-thirds of patients after CABG or valve surgery.Patients indicated for CABG or valve surgery were allocated randomly to sonolysis (60 patients, 37 males; mean age, 65.3 years) of the right middle cerebral artery (MCA) during cardiac surgery and control group (60 patients, 37 males; mean age, 65.3 years). Neurologic examination, cognitive function tests, and brain magnetic resonance imaging (MRI) were conducted before intervention as well as 24 to 72 hours and 30 days after surgery.New ischemic lesions on control diffusion-weighted MRI in the insonated MCA territory ≥0.5 mL were significantly less frequent in the sonolysis group than in the control group (13.3% vs 26.7%, P = 0.109). The sonolysis group exhibited significantly reduced median volume of new brain ischemic lesions (P = 0.026). Stenosis of the internal carotid artery ≥50% and smoking were independent predictors of new brain ischemic lesions ≥0.5 mL (odds ratio = 5.685 [1.272-25.409], P = 0.023 and 4.698 [1.092-20.208], P = 0.038, respectively). Stroke or transient ischemic attack occurred only in 2 control patients (P = 0.496). No significant differences were found in scores for postintervention cognitive tests (P > 0.05).This study provides class-II evidence that sonolysis during CABG or valve surgery reduces the risk of larger, new ischemic lesions in the brain.www.clinicaltrials.gov (NCT01591018).

[Epidemiology of cerebral perioperative vascular accidents]

OBJECTIVES

Stroke is a well-described postoperative complication, after carotid and cardiac surgery. On the contrary, few studies are available concerning postoperative stroke in general non-cardiac non-carotid surgery. The high morbid-mortality of stroke justifies an extended analysis of recent literature.

ARTICLE TYPE

Systematic review.

DATA SOURCES

Firstly, Medline and Ovid databases using combination of stroke, cardiac surgery, carotid surgery, general non-cardiac non-carotid surgery as keywords; secondly, national and European epidemiologic databases; thirdly, expert and French health agency recommendations; lastly, reference book chapters.

RESULTS

In cardiac surgery, with an incidence varying from 1.2 to 10% according to procedure complexity, stroke occurs peroperatively in 50% of cases and during the first 48 postoperative hours for the others. The incidence of stroke after carotid surgery is 1 to 20% according to the technique used as well as operator skills. Postoperative stroke is a rare (0.15% as mean, extremes around 0.02 to 1%) complication in general surgery, it occurs generally after the 24-48th postoperative hours, exceptional peroperatively, and 40% of them occurring in the first postoperative week. It concerned mainly aged patient in high-risk surgeries (hip fracture, vascular surgery). Postoperative stroke was associated to an increase in perioperative mortality in comparison to non-postoperative stroke operated patients.

CONCLUSION

Postoperative stroke is a quality marker of the surgical teams' skill and has specific onset time and induces an increase of postoperative mortality.

Neuronal preconditioning by inhalational anesthetics: evidence for the role of plasmalemmal adenosine triphosphate-sensitive potassium channels

BACKGROUND

Ischemic preconditioning is an important intrinsic mechanism for neuroprotection. Preconditioning can also be achieved by exposure of neurons to K+ channel-opening drugs that act on adenosine triphosphate-sensitive K+ (K(ATP)) channels. However, these agents do not readily cross the blood-brain barrier. Inhalational anesthetics which easily partition into brain have been shown to precondition various tissues. Here, the authors explore the neuronal preconditioning effect of modern inhalational anesthetics and investigate their effects on K(ATP) channels.

METHODS

Neuronal-glial cocultures were exposed to inhalational anesthetics in a preconditioning paradigm, followed by oxygen-glucose deprivation. Increased cell survival due to preconditioning was quantified with the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide reduction test. Recombinant plasmalemmal K(ATP) channels of the main neuronal type (Kir6.2/SUR1) were expressed in HEK293 cells, and the effects of anesthetics were evaluated in whole cell patch clamp recordings.

RESULTS

Both sevoflurane and the noble gas xenon preconditioned neurons at clinically used concentrations. The effect of sevoflurane was independent of K(ATP) channel activation, whereas the effect of xenon required the opening of plasmalemmal K(ATP) channels. Recombinant K(ATP) channels were activated by xenon but inhibited by halogenated volatiles. Modulation of mitochondrial K-ATP channels did not affect the activity of K(ATP) channels, thus ruling out an indirect effect of volatiles via mitochondrial channels.

CONCLUSIONS

The preconditioning properties of halogenated volatiles cannot be explained by their effect on K(ATP) channels, whereas xenon preconditioning clearly involves the activation of these channels. Therefore, xenon might mimic the intrinsic mechanism of ischemic preconditioning most closely. This, together with its good safety profile, might suggest xenon as a viable neuroprotective agent in the clinical setting.