Pressor Therapy in Acute Ischemic Stroke

Periprocedural therapeutics do not impair extracellular mitochondrial viability in transplantation

Mitochondrial transplantation is an emerging therapeutic approach for ischemia-reperfusion injury, offering the potential to restore cellular function through the engraftment of extracellular mitochondria. The successful clinical application of this strategy depends on the delivery of metabolically active mitochondria, yet the impact of circulating therapeutic agents on mitochondrial viability remains poorly understood. This study evaluates the effects of five clinically relevant agents commonly used during endovascular treatment of ischemic stroke-alteplase, cefazolin, lidocaine, phenylephrine, and heparinized saline-on extracellular mitochondria using an ex vivo model. Mitochondria were isolated from human skeletal muscle and mouse liver and exposed to these agents at clinically relevant and supra-physiological concentrations. Metabolic activity was assessed using a resazurin reduction assay as an indicator of mitochondrial viability. Even at concentrations up to 8-fold above clinical exposure, none of the agents significantly impaired mitochondrial function. These findings provide critical toxicological data demonstrating the compatibility of commonly used therapeutics with mitochondrial transplantation, supporting the development of safer and more optimized clinical protocols.

Intraoperative Blood Pressure Variability and Early Postoperative Stroke: A Case-Control Study

BACKGROUND

This study aims to assess the association of postoperative stroke with intraoperative hemodynamic variability and transfusion management.

METHODS

In this case-control study, adult patients (≥ 18 years) who had a stroke within 72 hours of a surgical procedure were matched to 2 control patients according to age, sex, and procedure type. Primary risk factors assessed were intraoperative fluid administration, blood product transfusion, vasopressor use, and measures of variability in systolic and diastolic blood pressure and heart rate: maximum, minimum, range, SD, and average real variability. The variables were analyzed with conditional logistic regression, which accounted for the 1:2 matched case-control study design.

RESULTS

Among 687 581 procedures, we identified 64 postoperative strokes (incidence, 9.3 [95% CI, 7.2-11.9] strokes per 100 000 procedures). These cases were matched with 128 controls. Stroke cases had higher Charlson cmorbidity index scores than did controls (P = .046). Blood pressure and heart rate variability measures were not associated with stroke. The risk of stroke was increased with red blood cell (RBC) transfusion (odds ratio [OR], 14.82; 95% CI, 3.40-64.66; P < .001), vasopressor use (OR, 3.91; 95% CI, 1.59-9.60; P = .003), and longer procedure duration (OR, 1.23/h; 95% CI, 1.01-1.51; P = .04). Multivariable analysis of procedure duration, RBC transfusion, and vasopressor use showed that only RBC transfusion was independently associated with an increased risk of stroke (OR, 10.10; 95% CI, 2.14-47.72; P = .004).

CONCLUSIONS

Blood pressure variability was not associated with an increased risk of postoperative stroke; however, RBC transfusion was an independent risk factor.

Relationship between mean blood pressure during hospitalization and clinical outcome after acute ischemic stroke

OBJECTIVE

The optimal blood pressure (BP) targets for acute ischemic stroke are unclear. We aimed to assess the relationship between Mean BP and clinical outcomes during hospitalization.

MATERIALS AND METHODS

We included 649 patients with Acute ischemic stroke (AIS) from December 2020 to July 2021. BP was measured daily, and mean blood pressure was calculated. Clinical events recorded within 90 days of randomization were: recurrent ischemic stroke, symptomatic intracranial hemorrhage, and death. The modified Rankin Scale (mRS) was used to measure primary outcomes 3 months after AIS. Logistic multiple regression analysis was performed by statistical software R.

RESULT

There is a nonlinear U-shaped relationship between SBP and poor outcomes. This means higher SBP and lower SBP will increase the incidence of poor outcomes. The optimal mean SBP during hospitalization was 135-150 mmHg, and patients with SBP < 135mmhg OR 2.4 [95% Cl, (1.16 ~ 4.97)], P = 0.018; and > 150mmhg OR 2.04 [95% Cl, 1.02 ~ 4.08], p = 0.045 had a higher probability of poor outcomes.

CONCLUSION

Our study shows that the optimal SBP of patients with AIS during hospitalization was 135-150 mmHg. The findings suggest that the relationship between mean SBP and 3-month functional outcome after AIS was U-shaped. Both higher SBP and lower SBP lead to poor prognosis in AIS patients.

Cerebral Collateral Circulation in the Era of Reperfusion Therapies for Acute Ischemic Stroke

Clinical outcomes of patients with acute ischemic stroke depend in part on the extent of their collateral circulation. A good collateral circulation has also been associated with greater benefit of intravenous thrombolysis and endovascular treatment. Treatment decisions for these reperfusion therapies are increasingly guided by a combination of clinical and imaging parameters, particularly in later time windows. Computed tomography and magnetic resonance imaging enable a rapid assessment of both the collateral extent and cerebral perfusion. Yet, the role of the collateral circulation in clinical decision-making is currently limited and may be underappreciated due to the use of rather coarse and rater-dependent grading methods. In this review, we discuss determinants of the collateral circulation in patients with acute ischemic stroke, report on commonly used and emerging neuroimaging techniques for assessing the collateral circulation, and discuss the therapeutic and prognostic implications of the collateral circulation in relation to reperfusion therapies for acute ischemic stroke.

Pressor therapy in acute ischaemic stroke: an updated systematic review

Background

Low blood pressure (BP) in acute ischaemic stroke (AIS) is associated with poor functional outcome, death, or severe disability. Increasing BP might benefit patients with post-stroke hypotension including those with potentially salvageable ischaemic penumbra. This updated systematic review considers the present evidence regarding the use of vasopressors in AIS.

Methods

We searched the Cochrane Database of Systematic Reviews, MEDLINE, EMBASE and trial databases using a structured search strategy. We examined reference lists of relevant publications for additional studies examining BP elevation in AIS.

Results

We included 27 studies involving 1886 patients. Nine studies assessed increasing BP during acute reperfusion therapy (intravenous thrombolysis, mechanical thrombectomy, intra-arterial thrombolysis or combined). Eighteen studies tested BP elevation alone. Phenylephrine was the most commonly used agent to increase BP (n = 16 studies), followed by norepinephrine (n = 6), epinephrine (n = 3) and dopamine (n = 2). Because of small patient numbers and study heterogeneity, a meta-analysis was not possible. Overall, BP elevation was feasible in patients with fluctuating or worsening neurological symptoms, large vessel occlusion with labile BP, sustained post-stroke hypotension and ineligible for intravenous thrombolysis or after acute reperfusion therapy. The effects on functional outcomes were largely unknown and close monitoring is advised if such intervention is undertaken.

Conclusion

Although theoretical arguments support increasing BP to improve cerebral blood flow and sustain the ischaemic penumbra in selected AIS patients, the data are limited and results largely inconclusive. Large, randomised controlled trials are needed to identify the optimal BP target, agent, duration of treatment and effects on clinical outcomes.

Successful Leptomeningeal Enhancement in a Patient with Tandem Occlusion of a Carotid and Middle Cerebral Artery Following Carotid Artery Stenting for Contralateral Carotid Artery Stenosis

Objective

Although the presence of leptomeningeal anastomosis is known as a predictor of favorable outcome in patients with acute large vessel occlusion, the efficacy of enhancing leptomeningeal collateral flow has rarely been demonstrated.

Case Presentation

A 73-year-old man previously diagnosed with asymptomatic bilateral carotid stenosis was admitted to our emergency department 2 hours after the onset of fluctuating symptoms, including aphasia, left conjugate deviation, and right hemiparesis. CT demonstrated no hemorrhagic lesion. Considering the history of the patient, emergent angiography was performed and demonstrated tandem occlusion of the left cervical internal carotid artery (ICA) with left common carotid injection, leptomeningeal flow compensating for distal territory of occluded segment of left middle cerebral artery (MCA) via the left anterior cerebral artery through severe cervical ICA stenosis with right common carotid injection, and the proximal segment of the left MCA through the posterior communicating artery and occlusion of the M2 segment with left vertebral injection. Given the results of angiography and fluctuating symptoms, hemodynamic insufficiency was considered the underlying stroke mechanism for this case. Although recanalization of tandem lesions was initially considered, the risk of distal clot migration was a concern, so the patient underwent right carotid artery stenting (CAS) to enhance leptomeningeal collateral flow. This resulted in immediate resolution of symptoms after right CAS.

Conclusion

Stenting for carotid artery stenosis contralateral to tandem occlusive lesion may offer an effective alternative when both Willisian and leptomeningeal collaterals are robust.

Management of neurophysiological monitoring changes during carotid endarterectomy exposure

BACKGROUND

Carotid endarterectomy (CEA) is a safe and effective operation in the management of carotid stenosis. Intraoperative neurophysiologic monitoring (IONM) changes during carotid clamping has been well studied, but there is scant evidence detailing IONM changes during carotid exposure.

OBJECTIVE

We analyzed our experience with IONM changes during CEA exposure to determine whether multimodal IONM changes during exposure predict outcomes and how best to manage this challenging clinical scenario.

METHODS

We reviewed all CEAs performed at our medical center between January 2015 and June 2020 and identified patients with multimodal IONM changes during exposure of the carotid artery. Our primary outcomes were perioperative stroke and functional outcomes. Functional outcomes were measured by modified Rankin scale (mRS), with good functional outcome defined at mRS scores 0-3. We also reviewed our intraoperative IONM change management strategies.

RESULTS

Five patients (4 males, 1 female) with an average age of 67 ± 12 years had intraoperative IONM changes during carotid exposure. Among these, three patients were discharged with good functional outcome, and four patients had a good functional outcome at last follow-up. Two patients had perioperative stroke, half of which resulted in significant disability. One patient was transferred to the neuroendovascular suite intraoperatively for evaluation for thromboembolism followed by angioplasty and stenting with distal protection.

CONCLUSION

Intraoperative IONM changes during carotid exposure predict outcomes in CEA. We propose that transition to the neuroendovascular suite following significant IONM changes during carotid exposure may be a useful strategy for management of this challenging clinical scenario. This approach provides the opportunity to evaluate and treat thromboembolism and still complete carotid revascularization when appropriate. This algorithm may be particularly useful in the era of dual trained vascular neurosurgeons.

European Stroke Organisation (ESO) guidelines on blood pressure management in acute ischaemic stroke and intracerebral haemorrhage

The optimal blood pressure (BP) management in acute ischaemic stroke (AIS) and acute intracerebral haemorrhage (ICH) remains controversial. These European Stroke Organisation (ESO) guidelines provide evidence-based recommendations to assist physicians in their clinical decisions regarding BP management in acute stroke.The guidelines were developed according to the ESO standard operating procedure and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. The working group identified relevant clinical questions, performed systematic reviews and meta-analyses of the literature, assessed the quality of the available evidence, and made specific recommendations. Expert consensus statements were provided where insufficient evidence was available to provide recommendations based on the GRADE approach. Despite several large randomised-controlled clinical trials, quality of evidence is generally low due to inconsistent results of the effect of blood pressure lowering in AIS. We recommend early and modest blood pressure control (avoiding blood pressure levels >180/105 mm Hg) in AIS patients undergoing reperfusion therapies. There is more high-quality randomised evidence for BP lowering in acute ICH, where intensive blood pressure lowering is recommended rapidly after hospital presentation with the intent to improve recovery by reducing haematoma expansion. These guidelines provide further recommendations on blood pressure thresholds and for specific patient subgroups. There is ongoing uncertainty regarding the most appropriate blood pressure management in AIS and ICH. Future randomised-controlled clinical trials are needed to inform decision making on thresholds, timing and strategy of blood pressure lowering in different acute stroke patient subgroups.

Time-dependent shift of the relationship between systolic blood pressure and clinical outcome in acute lacunar stroke

BACKGROUND AND AIMS

This study explores the relationship between systolic blood pressure during the acute period of stroke and poor functional outcome in patients with lacunar stroke, emphasizing a possible time-dependent nature of the relationship.

METHODS

Based on multicenter stroke registry data, patients with acute lacunar stroke were identified, and systolic blood pressure levels at eight time points (1, 2, 4, 8, 16, 24, 48, and 72 h) after stroke onset were extracted at the 15 participating centers in South Korea. Poor functional outcome was defined as a three-month modified Rankin Scale score of 2-6. Non-linear restricted cubic spline and linear models were used for assessing the relationship at each time point.

RESULTS

A total of 97,349 systolic blood pressure measurements of 3,042 patients were analyzed. At 1 h and 4 h after stroke onset, the relationship between systolic blood pressure and poor outcome showed a non-linear association. The nadir was 155 mmHg at 1 h and 124 mmHg at 4 h. After this time period, a higher systolic blood pressure was associated with a poorer outcome. This linear relationship weakened over time after 12 h (coefficient values of the adjusted linear models: 0.0081 at 8 h, 0.0105 at 12 h, 0.0102 at 24 h, 0.0082 at 48 h, 0.0054 at 72 h).

CONCLUSIONS

Based on our cohort of large number of lacunar stroke patients, our findings suggest that systolic blood pressure levels may follow a time-dependent course in relation to prediction of outcome at three months. The findings may be valuable for hypothesis generation in association with clinical trial development for blood pressure control in acute stroke patients.

Neurovascular physiology and neurocritical care

The neurological intensive care unit plays an integral role in the management of cerebrovascular disease in the acute and perioperative period. Understanding the use of intracranial pressure (ICP) monitoring and how to apply the appropriate intervention for ICP elevation to ensure adequate cerebral perfusion is the foundation of neurocritical care. Careful management of the interplay between cerebral and systemic physiology, particularly in disorders of cerebral autoregulation, is critical in preventing secondary brain injury. Finally, understanding the cerebral pathophysiology of the underlying injured brain in acute stroke, subarachnoid hemorrhage, and arterial stenosis can help to guide the optimal use of interventional endovascular procedures in these disease states.

Hemodynamics in acute stroke: Cerebral and cardiac complications

Hemodynamics is the study of blood flow, where parameters have been defined to quantify blood flow and the relationship with systemic circulatory changes. Understanding these perfusion parameters, the relationship between different blood flow variables and the implications for ischemic injury are outlined in the ensuing discussion. This chapter focuses on the hemodynamic changes that occur in ischemic stroke, and their contribution to ischemic stroke pathophysiology. We discuss the interaction between cardiovascular response and hemodynamic changes in stroke. Studying hemodynamic changes has a key role in stroke prevention, therapeutic implications and prognostic importance in acute ischemic stroke: preexisting hemodynamic and autoregulatory impairments predict the occurrence of stroke. Hemodynamic failure predisposes to the formation of thromboemboli and accelerates infarction due to impairing compensatory mechanisms. In ischemic stroke involving occlusion of a large vessel, persistent collateral circulation leads to preservation of ischemic penumbra and therefore justifying endovascular thrombectomy. Following thrombectomy, impaired autoregulation may lead to reperfusion injury and hemorrhage.

Relationship between blood pressure and outcome changes over time in acute ischemic stroke

OBJECTIVE

To evaluate whether the relationship between systolic blood pressure (SBP) and stroke outcome varies during the acute stage of ischemic stroke as a function of the elapsed time after stroke onset.

METHODS

Patients who were hospitalized due to ischemic stroke within 6 hours of onset were retrospectively analyzed. SBP data were collected at 8 time points (1, 2, 4, 8, 16, 24, 48, and 72 hours after onset). The primary functional outcome measure was a poor outcome, defined as a modified Rankin Scale score of >2 at 3 months after stroke. Linear and quadratic models were constructed at each time point to assess relationships between SBP and outcome.

RESULTS

Of the 2,546 patients, 728 (28.6%) had a poor outcome. SBP, as either a linear or quadratic term, had a significant effect on functional outcome, except at 4 hours after onset. For the initial 2 hours after onset, SBP had nonlinear U-shaped relationships with functional outcome, and patients with SBP of approximately 165 mm Hg were the least likely to have a poor outcome. Quadratic models exhibited a significantly better model fit. For 8-24 hours postonset, SBP exhibited linear relationships with functional outcome. For 48-72 hours postonset, SBP exhibited a J-shaped relationship with functional outcome, and the predicted probability of poor outcome was the lowest in patients with SBP of approximately 125 mm Hg. These relationships were relatively consistent across various sensitivity analyses.

CONCLUSION

This study revealed that the relationship between SBP and functional outcome may depend on elapsed time from stroke onset.

Capsular warning syndrome: clinical analysis and treatment

Background

Capsular warning syndrome (CWS) is a rare clinical syndrome, which is defined as a recurrent transient lacunar syndrome. The mechanism and clinical management of CWS remain unclear. The aim of the study was to discuss the clinical characteristics of CWS and evaluate the different outcome between rt-PA and no rt-PA therapy.

Methods

The present multicenter retrospective study involved three medical centers, and the clinical data were collected from patients with CWS between January 2013 and December 2018. The clinical characteristics of CWS were analyzed. Patients were divided into two groups: rt-PA and no rt-PA groups. The therapeutic effects and prognosis of these two groups were analyzed. A good prognosis was defined as 3-month modified Rankin Scale (mRS) ≤ 2.

Results

Our study included 72 patients, 27 patients were assigned to rt-PA group, 45 in no rt-PA group. Hypertension and dyslipidemia were the most common risk factors. The mean number of episodes before irreversible neurological impairment or the symptoms completely disappeared was five times (range: 3–11 times). A total of 58 (80.55%) patients had acute infarction lesions on the diffusion weighted imaging (DWI). The most common infarct location was the internal capsule (41,70.69%), followed by the thalamus and pons. The difference in therapeutic effects between the rt-PA, single and double antiplatelet groups was not statistically significant (P > 0.05). A good prognosis was observed in 61 (84.72%) patients after 3 months, in which 23 (23/27, 85.19%) patients were from the rt-PA group and 38 (38/45,84.44%) patients were from the no rt-PA group (P > 0.05). After 3 months of follow-up, two patients had recurrent ischemic stroke.

Conclusion

The most effective treatment of CWS remains unclear. Intravenous thrombolysis is safe for CWS patients. Regardless of the high frequency of infarction in CWS patients, more than 80% patients had a favorable functional prognosis.

Therapeutic-induced hypertension in patients with noncardioembolic acute stroke

OBJECTIVE

To evaluate the safety and efficacy of induced hypertension in patients with acute ischemic stroke.

METHODS

In this multicenter randomized clinical trial, patients with acute noncardioembolic ischemic stroke within 24 hours of onset who were ineligible for revascularization therapy and those with progressive stroke during hospitalization were randomly assigned (1:1) to the control and intervention groups. In the intervention group, phenylephrine was administered intravenously to increase systolic blood pressure (SBP) up to 200 mm Hg. The primary efficacy endpoint was early neurologic improvement (reduction in NIH Stroke Scale [NIHSS] score of ≥2 points during the first 7 days). The secondary efficacy endpoint was a modified Rankin Scale score of 0 to 2 at 90 days. Safety outcomes included symptomatic intracranial hemorrhage/edema, myocardial infarction, and death.

RESULTS

In the modified intention-to-treat analyses, 76 and 77 patients were included in the intervention and control groups, respectively. After adjustment for age and initial stroke severity, induced hypertension increased the occurrence of the primary (odds ratio 2.49, 95% confidence interval [CI] 1.25-4.96, p = 0.010) and secondary (odds ratio 2.97, 95% CI 1.32-6.68, p = 0.009) efficacy endpoints. Sixty-seven (88.2%) patients of the intervention group exhibited improvements in NIHSS scores of ≥2 points during induced hypertension (mean SBP 179·7 ± 19.1 mm Hg). Safety outcomes did not significantly differ between groups.

CONCLUSION

Among patients with noncardioembolic stroke who were ineligible for revascularization therapy and those with progressive stroke, phenylephrine-induced hypertension was safe and resulted in early neurologic improvement and long-term functional independence.

CLINICALTRIALSGOV IDENTIFIER

NCT01600235.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that for patients with acute ischemic stroke, therapeutic-induced hypertension increases the probability of early neurologic improvement.

Association of Blood Pressure During Thrombectomy for Acute Ischemic Stroke With Functional Outcome: A Systematic Review

Background and Purpose- Optimal blood pressure (BP) targets during mechanical thrombectomy (MT) for acute ischemic stroke (AIS) are unknown, and randomized controlled trials addressing this issue are lacking. We aimed to perform a systematic review of studies evaluating the influence of periprocedural BP on functional outcome after MT. Methods- Studies assessing periprocedural BP effect on functional outcome published after January 1st, 2012 were included in the systematic review. The PRISMA checklist and flow diagram were followed for the design and reporting of this work. Results- Nine studies were included, for a total of 1037 patients. The heterogeneity in findings with respect to BP monitoring and studied parameters precluded a meta-analysis. Mean arterial pressure was the most frequently reported parameter to describe BP variability during MT, and systolic BP was the main parameter used to define periprocedural BP targets. Five studies suggested an association between 3 types of BP drops as predictors of poor functional outcome at 3 months: >40% drop in mean arterial pressure compared with baseline (odds ratio=2.8; [1.09-7.19]; P=0.032), lowest mean arterial pressure before recanalization (odds ratio=1.28; [1.01-1.62] per 10 mm Hg drop below 100 mm Hg; P=0.04), and MAP drops (odds ratio=4.38; [1.53-12.6] for drops >10%). Four studies did not show an association between BP during MT and functional outcome, including 3 studies with strict periprocedural systolic BP targets (within a 140-180 mm Hg). Conclusions- BP drops during MT may be associated with a worse functional outcome. When strict systolic BP targets are achieved, no association between BP and functional outcome was also noted. Both conclusions require further evaluation in randomized studies.

The Importance of Combined Antithrombotic Treatment for Capsular Warning Syndrome

INTRODUCTION

Capsular warning syndrome (CWS) is characterized by recurrent conventional episodes of motor and/or sensory deficits without cortical symptoms. The purpose of this case series study was to evaluate the safety and appropriate treatment for CWS to prevent the development of complete stroke.

METHODS

We reviewed our hospital records and previous reports to find patients with neurologically fluctuating profiles, and excluded those with unknown details of initial treatment/final treatment of antiplatelet therapy or radiological findings.

RESULTS

We retrieved two cases of CWS from our hospital, which presented motor and/or sensory symptoms followed by complete resolution without complete ischemia. The recurring episodes in both were unable to be stabilized by single antiplatelet therapy but were successfully managed using two or more antiplatelet drugs. In 11 previously reported cases of CWS, the recurring episode was frequency stabilized with plural antiplatelet therapy.

CONCLUSION

Multiplicate antiplatelet therapy is important for treatment of CWS, and caution is needed regarding hemorrhagic complications.

Blood pressure control for acute severe ischemic and hemorrhagic stroke

PURPOSE OF REVIEW

Severe ischemic or hemorrhagic stroke is a devastating cerebrovascular disease often demanding critical care. Optimal management of blood pressure (BP) in the acute phase is controversial. The purpose of this review is to display insights from recent studies on BP control in both conditions.

RECENT FINDINGS

BP control in acute ischemic stroke has recently been investigated with regard to endovascular recanalizing therapies. Decreases from baseline BP and hypotension during the intervention have been found detrimental. Overall, a periinterventional SBP between 140 and 160 mmHg appeared favorable in several studies. In acute hemorrhagic stroke, the recently completed Antihypertensive Treatment of Acute Cerebral Hemorrhage II trial confirmed feasibility of early aggressive BP reduction but failed to demonstrate a reduction in hematoma growth or a clinical benefit.

SUMMARY

Recent findings do not support benefits of intensive BP lowering in both acute hemorrhagic and ischemic stroke, with the possible exception of the postinterventional phase after successful endovascular recanalization of large-vessel occlusions. Although optimal ranges of BP values remain to be defined, high BP should still be treated according to guidelines. As stroke patients requiring critical care are underrepresented in most studies on BP, caution in transferring these findings is warranted and prospective research in that patient population needed.

The cerebral collateral circulation: Relevance to pathophysiology and treatment of stroke

The brain's collateral circulation consists of arterial anastomotic channels capable of providing nutrient perfusion to brain regions whose normal sources of flow have become compromised, as occurs in acute ischemic stroke. Modern CT-based neuroimaging is capable of providing detailed information as to collateral extent and sufficiency and is complemented by magnetic resonance-based methods. In the present era of standard-of-care IV thrombolysis for acute ischemic stroke, and following the recent therapeutic successes of randomized clinical trials of acute endovascular intervention, the sufficiency of the collateral circulation has been convincingly established as a key factor influencing the likelihood of successful reperfusion and favorable clinical outcome. This article reviews the features of the brain's collateral circulation; methods for its evaluation in the acute clinical setting; the relevance of collateral circulation to prognosis in acute ischemic stroke; the specific insights into the collateral circulation learned from recent trials of endovascular intervention; and the major influence of genetic factors. Finally, we emphasize the need to develop therapeutic approaches to augment collateral perfusion as an adjunctive strategy to be employed along with, or prior to, thrombolysis and endovascular interventions, and we highlight the possible potential of inhaled nitric oxide, albumin, and other approaches. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Blood Pressure and Penumbral Sustenance in Stroke from Large Vessel Occlusion

The global burden of stroke remains high, and of the various subtypes of stroke, large vessel occlusions (LVOs) account for the largest proportion of stroke-related death and disability. Several randomized controlled trials in 2015 changed the landscape of stroke care worldwide, with endovascular thrombectomy (ET) now the standard of care for all eligible patients. With the proven success of this therapy, there is a renewed focus on penumbral sustenance. In this review, we describe the ischemic penumbra, collateral circulation, autoregulation, and imaging assessment of the penumbra. Blood pressure goals in acute stroke remain controversial, and we review the current data and suggest an approach for induced hypertension in the acute treatment of patients with LVOs. Finally, in addition to reperfusion and enhanced perfusion, efforts focused on developing therapeutic targets that afford neuroprotection and augment neural repair will gain increasing importance. ET has revolutionized stroke care, and future emphasis will be placed on promoting penumbral sustenance, which will increase patient eligibility for this highly effective therapy and reduce overall stroke-related death and disability.

Statistical analysis plan of the head position in acute ischemic stroke trial pilot (HEADPOST pilot)

Background The HEADPOST Pilot is a proof-of-concept, open, prospective, multicenter, international, cluster randomized, phase IIb controlled trial, with masked outcome assessment. The trial will test if lying flat head position initiated in patients within 12 h of onset of acute ischemic stroke involving the anterior circulation increases cerebral blood flow in the middle cerebral arteries, as measured by transcranial Doppler. The study will also assess the safety and feasibility of patients lying flat for ≥24 h. The trial was conducted in centers in three countries, with ability to perform early transcranial Doppler. A feature of this trial was that patients were randomized to a certain position according to the month of admission to hospital. Objective To outline in detail the predetermined statistical analysis plan for HEADPOST Pilot study. Methods All data collected by participating researchers will be reviewed and formally assessed. Information pertaining to the baseline characteristics of patients, their process of care, and the delivery of treatments will be classified, and for each item, appropriate descriptive statistical analyses are planned with comparisons made between randomized groups. For the outcomes, statistical comparisons to be made between groups are planned and described. Results This statistical analysis plan was developed for the analysis of the results of the HEADPOST Pilot study to be transparent, available, verifiable, and predetermined before data lock. Conclusions We have developed a statistical analysis plan for the HEADPOST Pilot study which is to be followed to avoid analysis bias arising from prior knowledge of the study findings. Trial registration The study is registered under HEADPOST-Pilot, ClinicalTrials.gov Identifier NCT01706094.

Expanding the concept of neuroprotection for acute ischemic stroke: The pivotal roles of reperfusion and the collateral circulation

This review surveys the efforts taken to achieve clinically efficacious protection of the ischemic brain and underscores the necessity of expanding our purview to include the essential role of cerebral perfusion and the collateral circulation. We consider the development of quantitative strategies to measure cerebral perfusion at the regional and local levels and the application of these methods to elucidate flow-related thresholds of ischemic viability and to characterize the ischemic penumbra. We stress that the modern concept of neuroprotection must consider perfusion, the necessary substrate upon which ischemic brain survival depends. We survey the major mechanistic approaches to neuroprotection and review clinical neuroprotection trials, focusing on those phase 3 multicenter clinical trials for acute ischemic stroke that have been completed or terminated. We review the evolution of thrombolytic therapies; consider the lessons learned from the initial, negative multicenter trials of endovascular therapy; and emphasize the highly successful positive trials that have finally established a clinical role for endovascular clot removal. As these studies point to the brain's collateral circulation as key to successful reperfusion, we next review the anatomy and pathophysiology of collateral perfusion as it relates to ischemic infarction, as well as the molecular and genetic influences on collateral development. We discuss the current MR and CT-based diagnostic methods for assessing the collateral circulation and the prognostic significance of collaterals in ischemic stroke, and we consider past and possible future therapeutic directions.

Blood pressure management in acute stroke

Blood pressure (BP) is elevated in 75% or more of patients with acute stroke and is associated with poor outcomes. Whether to modulate BP in acute stroke has long been debated. With the loss of normal cerebral autoregulation, theoretical concerns are twofold: high BP can lead to cerebral oedema, haematoma expansion or haemorrhagic transformation; and low BP can lead to increased cerebral infarction or perihaematomal ischaemia. Published evidence from multiple large, high-quality, randomised trials is increasing our understanding of this challenging area, such that BP lowering is recommended in acute intracerebral haemorrhage and is safe in ischaemic stroke. Here we review the evidence for BP modulation in acute stroke, discuss the issues raised and look to on-going and future research to identify patient subgroups who are most likely to benefit.

Safety of peripheral administration of phenylephrine in a neurologic intensive care unit: A pilot study

Integral to the management of the neurocritically injured patient are the prevention and treatment of hypotension, maintenance of cerebral perfusion pressure, and occasionally blood pressure augmentation. When adequate volume resuscitation fails to meet perfusion needs, vasopressors are often used to restore end-organ perfusion. This has historically necessitated central venous access given well-documented incidence of extravasation injuries associated with peripheral administration of vasopressors. In this pilot study, we report our 6-month experience with peripheral administration of low-concentration phenylephrine (40 μg/mL) in our neurocritical care unit. We were able to administer peripheral phenylephrine, up to a dose of 2 μg/(kg min), for an average of 14.29hours (1-54.3) in 20 patients with only 1 possible minor complication and no major complications. This was achieved by adding additional safety measures in our computerized physician order entry system and additional nurse-driven safety protocols. Thus, with careful monitoring and safety precautions, peripheral administration of phenylephrine at an optimized concentration appears to have an acceptable safety profile for use in the neurocritical care unit up to a mean infusion time of 14hours.

Intracranial pressure elevation reduces flow through collateral vessels and the penetrating arterioles they supply. A possible explanation for 'collateral failure' and infarct expansion after ischemic stroke

Recent human imaging studies indicate that reduced blood flow through pial collateral vessels ('collateral failure') is associated with late infarct expansion despite stable arterial occlusion. The cause for 'collateral failure' is unknown. We recently showed that intracranial pressure (ICP) rises dramatically but transiently 24 hours after even minor experimental stroke. We hypothesized that ICP elevation would reduce collateral blood flow. First, we investigated the regulation of flow through collateral vessels and the penetrating arterioles arising from them during stroke reperfusion. Wistar rats were subjected to intraluminal middle cerebral artery (MCA) occlusion (MCAo). Individual pial collateral and associated penetrating arteriole blood flow was quantified using fluorescent microspheres. Baseline bidirectional flow changed to MCA-directed flow and increased by >450% immediately after MCAo. Collateral diameter changed minimally. Second, we determined the effect of ICP elevation on collateral and watershed penetrating arteriole flow. Intracranial pressure was artificially raised in stepwise increments during MCAo. The ICP increase was strongly correlated with collateral and penetrating arteriole flow reductions. Changes in collateral flow post-stroke appear to be primarily driven by the pressure drop across the collateral vessel, not vessel diameter. The ICP elevation reduces cerebral perfusion pressure and collateral flow, and is the possible explanation for 'collateral failure' in stroke-in-progression.

Intracranial pressure elevation after ischemic stroke in rats: cerebral edema is not the only cause, and short-duration mild hypothermia is a highly effective preventive therapy

In both the human and animal literature, it has largely been assumed that edema is the primary cause of intracranial pressure (ICP) elevation after stroke and that more edema equates to higher ICP. We recently demonstrated a dramatic ICP elevation 24 hours after small ischemic strokes in rats, with minimal edema. This ICP elevation was completely prevented by short-duration moderate hypothermia soon after stroke. Here, our aims were to determine the importance of edema in ICP elevation after stroke and whether mild hypothermia could prevent the ICP rise. Experimental stroke was performed in rats. ICP was monitored and short-duration mild (35 °C) or moderate (32.5 °C) hypothermia, or normothermia (37 °C) was induced after stroke onset. Edema was measured in three studies, using wet-dry weight calculations, T2-weighted magnetic resonance imaging, or histology. ICP increased 24 hours after stroke onset in all normothermic animals. Short-duration mild or moderate hypothermia prevented this rise. No correlation was seen between ΔICP and edema or infarct volumes. Calculated rates of edema growth were orders of magnitude less than normal cerebrospinal fluid production rates. These data challenge current concepts and suggest that factors other than cerebral edema are the primary cause of the ICP elevation 24 hours after stroke onset.

Collaterals: Implications in cerebral ischemic diseases and therapeutic interventions

Despite the tremendous progress made in the treatment of cerebrovascular occlusive diseases, many patients suffering from ischemic brain injury still experience dismal outcomes. Although rehabilitation contributes to post-stroke functional recovery, there is no doubt that interventions that promote the restoration of blood supply are proven to minimize ischemic injury and improve recovery. In response to the acutely decreased blood perfusion during arterial occlusion, arteriogenesis, the compensation of blood flow through the collateral circulation during arterial obstructive diseases can act not only in a timely fashion but also much more efficiently compared to angiogenesis, the sprouting of new capillaries, and a mechanism occurring in a delayed fashion while increases the total resistance of the vascular bed of the affected territory. Interestingly, despite the vast differences between the two vascular remodeling mechanisms, some crucial growth factors and cytokines involved in angiogenesis are also required for arteriogenesis. Understanding the mechanisms underlying vascular remodeling after ischemic brain injury is a critical step towards the development of effective therapies for ischemic stroke. The present article will discuss our current views in vascular remodeling acutely after brain ischemia, namely arteriogenesis, and some relevant clinical therapies available on the horizon in augmenting collateral flow that hold promise in treating ischemic brain injury. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Multimodal imaging in acute ischemic stroke

OPINION STATEMENT

Recent years have seen the development of novel neuroimaging techniques whose roles in the management of acute stroke are sometimes confusing and controversial. This may be attributable in part to a focus on establishing simplified algorithms and terminology that omit consideration of the basic pathophysiology of cerebral ischemia and, consequently, of the full potential for optimizing patients' care based upon their individual imaging findings. This review begins by discussing cerebral hemodynamic physiology and of the effects of hemodynamic disturbances upon the brain. Particular attention will be paid to the hemodynamic measurements and markers of tissue injury that are provided by common clinical imaging techniques, with the goal of enabling greater confidence and flexibility in understanding the potential uses of these techniques in various clinical roles, which will be discussed in the remainder of the review.

Flow Augmentation in Acute Ischemic Stroke

There is an urgent need for additional therapeutic options for acute ischemic stroke considering the major pitfalls of the options available. Herein, we briefly review the role of cerebral blood flow, collaterals, vasoreactivity, and reperfusion injury in acute ischemic stroke. Then, we reviewed pharmacological and interventional measures such as volume expansion and induced hypertension, intra-aortic balloon counterpulsation, partial aortic occlusion, extracranial-intracranial carotid bypass surgery, sphenopalatine ganglion stimulation, and transcranial laser therapy with regard to their effects on flow augmentation and neuroprotection.

Effects of early blood pressure lowering on early and long-term outcomes after acute stroke: an updated meta-analysis

BACKGROUND

Hypertension is common after acute stroke onset. Previous studies showed controversial effects of early blood pressure (BP) lowering on stroke outcomes. The aim of this study is to assess the effects of early BP lowering on early and long-term outcomes after acute stroke.

METHODS

A meta-analysis was conducted with prospective randomized controlled trials assessing the effects of early BP lowering on early and long-term outcomes after acute stroke compared with placebo. Literature searching was performed in the databases from inception to December 2013. New evidence from recent trials were included. Outcomes were analyzed as early (within 30 days) and long-term (from 3 to 12 months) endpoints using summary estimates of relative risks (RR) and their 95% confidence intervals (CI) with the fixed-effect model or random-effect model.

RESULTS

Seventeen trials providing data from 13236 patients were included. Pooled results showed that early BP lowering after acute stroke onset was associated with more death within 30 days compared with placebo (RR: 1.34 and 95% CI: 1.02, 1.74, p = 0.03). However the results showed that early BP lowering had no evident effect on early neurological deterioration, early death within 7 days, long-term death, early and long-term dependency, early and long-term combination of death or dependency, long-term stroke recurrence, long-term myocardial infarction and long-term CVE.

CONCLUSIONS

The new results lend no support to early BP lowering after acute stroke. Early BP lowering may increase death within 30 days after acute stroke.

[Stroke care in the ICU: general supportive treatment. Experts' recommendations]

The French Society of Intensive Care (SRLF) requested medical experts to publish recommendations on the management of stroke in the ICU for adult and pediatric patients. The following article describes the underlying evidence used by the experts to elaborate recommendations for general supportive treatment. Such treatment is fundamental for victims of acute stroke to avoid neurological worsening. Oxygen delivery in a normoxic patient is useless. However, if saturation is below 92 %, oxygen supplementation is needed. Hyper- and hypoglycemia worsen the neurological prognosis. As no glycemic target is known, administration of insulin is required for glucose levels higher that 10 mmol/l. Body temperature above 37.5° is associated with poorer outcome. In the acute phase of stroke, high blood pressure should not be lowered except in life-threatening situations, and if so the lowering should be done cautiously. The current consensus is to lower blood pressure if the systolic pressure is above 220 mmHg or if the diastolic pressure is above 120 mmHg for ischemic stroke. For hemorrhagic stroke and after thrombolysis, treatment is needed if systolic pressure rises above 180 mmHg and if diastolic pressure is above 105 mmHg. Small doses of heparin decrease the risk of deep venous thrombosis and pulmonary embolism without increasing cerebral bleeding. There is no consensus on the treatment of epileptic crises after stroke and no dedicated treatment. Further studies are needed to define adequate blood pressure and glycemic target values in order to limit secondary worsening after an acute stroke as well as the appropriate modalities for the treatment of epilepsy.

Progressive lacunar stroke: review of mechanisms, prognostic features, and putative treatments

Lacunar stroke is generally considered to have a fair outcome. However 20-30% of patients with lacunar stroke worsen neurologically in hours or days after onset, reaching eventually an unexpectedly severe disability status. In the field of acute stroke, progressive lacunar stroke remains an important unresolved practice problem, because as yet no treatment does exist proven to prevent or halt progression. Pathophysiology of progression is yet incompletely understood. Hemodynamic factors, extension of thrombosis, excitotoxicity, and inflammation, have been proposed as possible mechanisms of progression. A few clinical studies also aimed at establishing presentation features that may help identifying patients at risk of deterioration. In this paper, we review hypothesized mechanisms of lacunar stroke progression and possible markers of early deterioration. Moreover, based on putative mechanisms and suggestions from reported evidence, we propose a few treatments that seem worthy to be tested by randomized clinical trials.

MR perfusion imaging in acute ischemic stroke

Magnetic resonance (MR) perfusion imaging offers the potential for measuring brain perfusion in acute stroke patients, at a time when treatment decisions based on these measurements may affect outcomes dramatically. Rapid advancements in both acute stroke therapy and perfusion imaging techniques have resulted in continuing redefinition of the role that perfusion imaging should play in patient management. This review discusses the basic pathophysiology of acute stroke, the utility of different kinds of perfusion images, and research on the continually evolving role of MR perfusion imaging in acute stroke care.

Ischemic stroke: emergencies and management

The past 40 years have seen the evolution of acute ischemic stroke management from unproven therapies du jour, such as steroids, heparin for stroke in evolution, and hypervolemic-hemodilution, to more of a scientific basis for our decision-making process. This evolution is directly related to the advancements in imaging of stroke. It is also related to carefully designed, controlled clinical trials of potential therapies, which have led to the recognition of the benefits of thrombolytic therapy in the acute setting but have also caused confusion and frustration over the lack of benefit for potential neuroprotective agents that once seemed promising.

Treatment of acute ischemic stroke: beyond thrombolysis and supportive care

The initial therapeutic approach to acute ischemic stroke consists of thrombolytic therapy and early initiation of supportive care, usually commenced prior to the determination of the underlying stroke etiology. Varying stroke mechanisms may call for specific, etiology-based treatment. The majority of strokes result from cardioembolism, large-vessel atherothromboembolism, and small-vessel occlusive disease. There are scant data to support the use of acute anticoagulation therapy over anti-platelet therapy in cardioembolic stroke and large-vessel atherosclerosis, although it may be reasonable in a certain subset of patients. However, augmentation of blood flow with early surgery, stenting, or induced hypertension, may play a role in patients with large artery stenosis. The less commonly identified stroke mechanisms may warrant special consideration in treatment. Controversy remains regarding the optimal anti-thrombotic treatment of arterial dissection. Reversible cerebral vasoconstriction syndrome may benefit from therapy with calcium channel blockers, high-dose steroids, or magnesium, although spontaneous recovery may occur. Inflammatory vasculopathies, such as isolated angiitis of the central nervous system and temporal arteritis, require prompt diagnosis as the mainstay of therapy is immunosuppression. Cerebral venous thrombosis is a rare cause of stroke, but one that needs early identification and treatment with anticoagulation. Rapid determination of stroke mechanism is essential for making these critical early treatment decisions.

Current status of blood pressure management after stroke

Stroke is a leading cause of mortality and long-term disability in the western world, accounting for 5% of the UK health budget. Consequently, it has been the major focus of recent healthcare advances. Physiological disturbances are common following an acute stroke, chiefly blood pressure (BP) abnormalities (high and 'relatively' low BP), which indicate adverse prognosis. While pilot studies suggest that early intervention to moderate both extremes of BP may improve outcomes, definitive evidence is awaited from ongoing research. Long-term elevated BP is the most prevalent risk factor for future stroke, with a comprehensive evidence base supporting BP reduction to reduce the risk of vascular events, including stroke. However, adherence to secondary preventive medications, including antihypertensive agents, remains poor. This article summarizes the current understanding of the role of BP in stroke, focusing on the management of BP for secondary prevention. Further emphasis is placed on identifying deficiencies in long-term management; barriers to improved application and potential interventions to overcome these barriers are summarized.

Hyperacute ischemic stroke management: reperfusion and evolving therapies

Management of acute ischemic stroke patients is organized around several priorities aimed at ensuring optimal patient outcomes, the first of which is reperfusion therapy, followed by determination of pathogenic mechanism by provision of a comprehensive workup to determine probable cause of the ischemic stroke or transient ischemic attack, for the purpose of providing appropriate prophylaxis for subsequent events. Provision of secondary prevention measures along with therapies that prevent complications associated with neurologic disability, and evaluation for the most appropriate level of rehabilitation services are the final priorities during acute hospitalization. This article provides an overview of reperfusion therapies and emerging hemodynamic treatments for hyperacute ischemic strokes. Gaps in the scientific evidence that are driving current blood flow augmentation research are identified.