Dynamic cerebral autoregulation is transiently impaired for one week after large-vessel acute ischemic stroke

Perioperative care of patients with recent stroke undergoing nonemergent, nonneurological, noncardiac, nonvascular surgery: a systematic review and meta-analysis

PURPOSE OF REVIEW

To systematically review and perform a meta-analysis of published literature regarding postoperative stroke and mortality in patients with a history of stroke and to provide a framework for preoperative, intraoperative, and postoperative care in an elective setting.

RECENT FINDINGS

Patients with nonneurological, noncardiac, and nonvascular surgery within three months after stroke have a 153-fold risk, those within 6 months have a 50-fold risk, and those within 12 months have a 20-fold risk of postoperative stroke. There is a 12-fold risk of in-hospital mortality within three months and a three-to-four-fold risk of mortality for more than 12 months after stroke. The risk of stroke and mortality continues to persist years after stroke. Recurrent stroke is common in patients in whom anticoagulation/antiplatelet therapy is discontinued. Stroke and time elapsed after stroke should be included in the preoperative assessment questionnaire, and a stroke-specific risk assessment should be performed before surgical planning is pursued.

SUMMARY

In patients with a history of a recent stroke, anesthesiology, surgery, and neurology experts should create a shared mental model in which the patient/surrogate decision-maker is informed about the risks and benefits of the proposed surgical procedure; secondary-stroke-prevention medications are reviewed; plans are made for interruptions and resumption; and intraoperative care is individualized to reduce the likelihood of postoperative stroke or death.

Lower dynamic cerebral autoregulation following acute bout of low-volume high-intensity interval exercise in chronic stroke compared to healthy adults

Fluctuating arterial blood pressure during high-intensity interval exercise (HIIE) may challenge dynamic cerebral autoregulation (dCA), specifically after stroke after an injury to the cerebrovasculature. We hypothesized that dCA would be attenuated at rest and during a sit-to-stand transition immediately after and 30 min after HIIE in individuals poststroke compared with age- and sex-matched control subjects (CON). HIIE switched every minute between 70% and 10% estimated maximal watts for 10 min. Mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) were recorded. dCA was quantified during spontaneous fluctuations in MAP and MCAv via transfer function analysis. For sit-to-stand, time delay before an increase in cerebrovascular conductance index (CVCi = MCAv/MAP), rate of regulation, and % change in MCAv and MAP were measured. Twenty-two individuals poststroke (age 60 ± 12 yr, 31 ± 16 mo) and twenty-four CON (age 60 ± 13 yr) completed the study. Very low frequency (VLF) gain (P = 0.02, η2 = 0.18) and normalized gain (P = 0.01, η2 = 0.43) had a group × time interaction, with CON improving after HIIE whereas individuals poststroke did not. Individuals poststroke had lower VLF phase (P = 0.03, η2 = 0.22) after HIIE compared with CON. We found no differences in the sit-to-stand measurement of dCA. Our study showed lower dCA during spontaneous fluctuations in MCAv and MAP following HIIE in individuals poststroke compared with CON, whereas the sit-to-stand response was maintained.NEW & NOTEWORTHY This study provides novel insights into poststroke dynamic cerebral autoregulation (dCA) following an acute bout of high-intensity interval exercise (HIIE). In people after stroke, dCA appears attenuated during spontaneous fluctuations in mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) following HIIE. However, the dCA response during a single sit-to-stand transition after HIIE showed no significant difference from controls. These findings suggest that HIIE may temporarily challenge dCA after exercise in individuals with stroke.

The impact of collateral therapeutics on stroke hemodynamics in normotensive and hypertensive rats: a step toward translation

Introduction

Stroke interventions that increase collateral flow have the potential to salvage penumbral tissue and increase the number of patients eligible for reperfusion therapy. We compared the efficacy of two different collateral therapeutics during transient middle cerebral artery occlusion (tMCAO) in normotensive and hypertensive rats.

Methods

The change in collateral and core perfusion was measured using dual laser Doppler in response to either a pressor agent (phenylephrine, 10 mg/kg iv or vehicle) or a collateral vasodilator (TM5441, 5 mg/kg iv or vehicle) given 30 min into tMCAO in male Wistar and spontaneously hypertensive rats (SHRs).

Results

Pressor therapy increased collateral flow in the Wistar rats but was ineffective in the SHRs. The increase in collateral flow in the Wistar rats was associated with impaired cerebral blood flow autoregulation (CBFAR) that was intact in the SHRs. TM5441 caused a decrease in collateral perfusion in the Wistar rats and a modest increase in the SHRs. The pressor therapy reduced early infarction in both groups but increased edema in the SHRs, whereas TM5441 did not have any beneficial effects in either group.

Conclusions

Thus, the pressor therapy was superior to a collateral vasodilator in increasing collateral flow and improving outcomes in the Wistar rats, likely due to pial collaterals that were pressure passive; the lack of CBF response in the SHRs to pressor therapy was likely due to intact CBFAR that limited perfusion. While TM5441 modestly increased CBF in the SHRs but not in the Wistar rats, it did not have a beneficial effect on stroke outcomes. These results suggest that collateral therapies may need to be selected for certain comorbidities.

Hemodynamic predictors of early neurological deterioration and clinical outcome after endovascular treatment in large artery occlusion

Objective

Half of the patients with acute large artery occlusion (LAO) have poor outcomes after endovascular treatment (EVT). Early complications such as cerebral edema and symptomatic intracranial hemorrhage (sICH) can lead to early neurological deterioration (END), which correlates with hemodynamics. This study aimed to identify the hemodynamic predictors of END and outcomes in LAO patients after EVT.

Methods

A total of 76 patients with anterior circulation LAO who underwent EVT and received transcranial Doppler (TCD) monitoring were included. Bilateral middle cerebral artery (MCA) blood flow velocities (BFVs) were measured repeatedly within 1 week. Mean flow velocities (MFV) and MFV index (ipsilateral MFV/contralateral MFV) were calculated. The primary outcome was the incidence of END within 72 h. The secondary outcome was the functional outcome at 90 days-a good outcome was defined as a modified Rankin scale (mRS) score of 0-2, while a poor outcome was defined as an mRS score of 3-6.

Results

A total of 13 patients (17.1 %) experienced END within 72 h, including 5 (38.5 %) with cerebral edema, 5 (38.5 %) with sICH, and 3 (23.0 %) with infarct progression. Multivariable logistic regression analysis showed that a higher 24 h MFV index was independently associated with END (aOR 10.5; 95 % CI 2.28-48.30, p = 0.003) and a poor 90-day outcome (aOR 5.10; 95 % CI 1.38-18.78, p = 0.014). The area under the receiver operating characteristic (ROC) curve (AUC) of the 24 h MFV index for predicting END was 0.807 (95 % CI 0.700-0.915, p = 0.0005), the sensitivity was 84.6 %, and the specificity was 66.7 %. At the 1-week TCD follow-up, patients who had poor 90-day outcomes showed significantly higher 1-week iMFV [73.5 (58.4-99.0) vs. 57.7 (45.3-76.3), p = 0.004] and MFV index [1.24 (0.98-1.57) vs.1.0 (0.87-1.15) p = 0.007]. A persistent high MFV index (PHMI) was independently associated with a poor outcome (aOR 7.77, 95 % CI 1.81-33.3, p = 0.006).

Conclusion

TCD monitoring within 24 h after EVT in LAO patients can help predict END, while dynamic follow-up within 1 week is valuable in predicting clinical outcomes.

Blood pressure-cerebral oxygen coupling model: A new approach for stroke risk prediction

Stroke is a major cause of death and disability worldwide, but predicting its risk remains challenging. This study aimed to evaluate the cerebral blood flow autoregulation function of subjects with different stroke risk levels and predict their stroke risk. The coupling strength between cerebral oxygen and blood pressure signals was calculated by wavelet analysis and dynamic Bayesian inference and used as a quantitative index of cerebral blood flow autoregulation. A stroke prediction model based on the extreme random tree was constructed using the coupling strength and other data as input features. The results showed that the coupling strength was significantly higher in the high-risk group than the other groups. Moreover, the prediction model achieved an average accuracy of 0.80 across the three groups. The coupling strength of cerebral oxygen and blood pressure can be used as an objective index to predict stroke risk, which has implications for stroke prevention and intervention.

Sequential carotid Doppler study in acute stroke and its clinical correlation: A prospective study

Objectives

Resistive index (RI) and pulsatility index (PI) assessed on carotid Doppler assess the hemodynamic status of cranial vasculature. They are related to the severity of stroke and help determine the overall outcome. This study was done to compare the hospital stay and stroke severity with RI and PI of both internal carotid arteries.

Materials and Methods

Patients >18 years of age presenting within 48 h of anterior circulation stroke (either ischemic or hemorrhagic) were included. They were divided into two groups based on their length of stay (LOS). They were assessed clinically on days 1, 3, and 5, and underwent a carotid Doppler study on the same days. The Doppler parameters were correlated with the LOS and stroke severity for possible associations.

Results

One hundred and one patients were included. Forty-seven patients had a favorable outcome based on LOS. In this group, significant decrease in RI and PI scores was seen from days 1 to 3. In patients with unfavorable outcome, there was a significant increase in PI on days 1-3 and days 1-5. The National Institutes of Health Stroke Scale decreased significantly from days 1 to 5 in favorable group.

Conclusion

For those with an unfavorable outcome and prolonged LOS, PI continues to increase suggesting a failure of autoregulation. Carotid Doppler can be a simple bedside tool to predict outcome in patients with acute stroke.

Association between time-dependent changes in cerebrovascular autoregulation after cardiac arrest and outcomes: A prospective cohort study

This prospective observational single-center cohort study aimed to determine an association between cerebrovascular autoregulation (CVAR) and outcomes in hypoxic-ischemic brain injury post-cardiac arrest (CA), and assessed 100 consecutive post-CA patients in Japan between June 2017 and May 2020 who experienced a return of spontaneous circulation. Continuous monitoring was performed for 96 h to determine CVAR presence. A moving Pearson correlation coefficient was calculated from the mean arterial pressure and cerebral regional oxygen saturation. The association between CVAR and outcomes was evaluated using the Cox proportional hazard model; non-CVAR time percent was the time-dependent, age-adjusted covariate. The non-linear effect of target temperature management (TTM) was assessed using a restricted cubic spline. Of the 100 participants, CVAR was detected using the cerebral performance category (CPC) in all patients with a good neurological outcome (CPC 1-2) and in 65 patients (88%) with a poor outcome (CPC 3-5). Survival probability decreased significantly with increasing non-CVAR time percent. The TTM versus the non-TTM group had a significantly lower probability of a poor neurological outcome at 6 months with a non-CVAR time of 18%-37% (p < 0.05). Longer non-CVAR time may be associated with significantly increased mortality in hypoxic-ischemic brain injury post-CA.

Age and sex affect the association of systolic blood pressure with clinical outcomes in thrombolysed stroke patient: a secondary analysis of the INTRECIS study

Background and purpose

Blood pressure is associated with outcomes in acute ischemic stroke (AIS) patients receiving intravenous alteplase. The study aimed to explore the effect of sex and age on their association.

Methods

Based on a prospective cohort, we retrospectively enrolled consecutive AIS patients who received intravenous alteplase and had complete blood pressure data, including baseline systolic blood pressure (SBP 01), SBP at 1 h (SBP 02), and SBP at 24 h (SBP 03) after alteplase. Maximum SBP (SBP max), minimum SBP (SBP min), and mean SBP (SBP mean) were calculated. Poor outcome was defined as having a modified Rankin Scale (mRS) score of 2-6 at 90 days. We explored the effect of age and sex on the association of different SBP indicators with the 3-month outcomes.

Results

A total of 1,593 eligible patients were included in the present study. All SBP indicators were found to be higher in patients with poor vs. good outcomes. Multivariate logistic regression analysis showed that all SBP indicators except baseline SBP were associated with poor outcomes with good prediction powers (AUC, 0.762-0.766). More SBP indicators (SBP 02, SBP 03, SBP min, and SBP mean) were associated with poor outcomes in women vs. men, while all SBP indicators after alteplase were associated with poor outcomes in patients aged ≥ 60 years, but none was seen in patients aged < 60 years. Furthermore, all SBP indicators after alteplase were associated with poor outcomes in women aged ≥ 60 years, while only SBP 03 in men aged < 60 years.

Conclusion

Among Chinese stroke patients treated with intravenous alteplase, SBP after alteplase was associated with clinical outcomes, which were affected by age and sex.

Challenges of anaesthetising a child with Bow Hunter's syndrome and dilated cardiomyopathy for occipitocervical fusion

Paediatric Bow Hunter's syndrome (BHS), or rotational vertebral artery syndrome, is a rare cause of posterior circulation insufficiency in children. It results from mechanical obstruction of the vertebral artery by the transverse process of cervical vertebrae resulting in vertebrobasilar insufficiency during the neck rotation to the sides. Paediatric dilated cardiomyopathy (DCM) is a rare myocardial disease that presents with ventricular dilatation and cardiac dysfunction. This case report describes the successful anaesthetic management of an boy with BHS due to atlantoaxial dislocation and DCM. The child was anaesthetised by keeping the following anaesthetic goals in mind such as maintenance of the heart rate, rhythm, preload, afterload and contractility close to the baseline for both DCM and BHS. Haemodynamic management with optimal fluids, inotrope and a vasopressor and titrating its volume and doses using multimodal haemodynamic monitoring while keeping both cardio and neuroprotective strategies, and the multimodal analgesia techniques helped the child for faster recovery.

Precision Medicine in Neurocritical Care for Cerebrovascular Disease Cases

Scientific advances have informed many aspects of acute stroke care but have also highlighted the complexity and heterogeneity of cerebrovascular diseases. While practice guidelines are essential in supporting the clinical decision-making process, they may not capture the nuances of individual cases. Personalized stroke care in ICU has traditionally relied on integrating clinical examinations, neuroimaging studies, and physiologic monitoring to develop a treatment plan tailored to the individual patient. However, to realize the potential of precision medicine in stroke, we need advances and evidence in several critical areas, including data capture, clinical phenotyping, serum biomarker development, neuromonitoring, and physiology-based treatment targets. Mathematical tools are being developed to analyze the multitude of data and provide clinicians with real-time information and personalized treatment targets for the critical care management of patients with cerebrovascular diseases. This review summarizes research advances in these areas and outlines principles for translating precision medicine into clinical practice.

Good outcome associated with blood-brain barrier disruption and lower blood pressure after endovascular therapy

OBJECTIVES

To evaluate the association between post-endovascular thrombectomy (EVT) blood-brain barrier (BBB) disruption on MRI or CT and average systolic blood pressure (SBP) with favorable 90-day functional outcome. Observational studies have found elevated SBP associated with worse outcomes post-EVT, while recent randomized trials found no difference in targeted BP reduction. There may be a subgroup of patients who benefit from targeted BP reduction post-EVT.

METHODS

This is a single-center study of 1) anterior large vessel occlusion stroke patients treated with EVT from 2015 to 2021, 2) achieved mTICI grade 2b or 3. Hyperintense acute reperfusion marker (HARM), hemorrhagic transformation (HT), and midline shift at 3 h post-EVT and 24 h imaging were assessed independently by multiple raters. Binary logistic regression models were used to determine the association of post-EVT SBP with outcomes. BBB disruption was defined as HT or HARM on 3h post-EVT imaging.

RESULTS

Of 103 patients, those with SBP 100-129 versus SBP 130-160 found no significant difference in favorable 90-day outcome (64% vs. 46%, OR 2.11, 95% CI 0.78-5.76, p=0.143). However, among 71 patients with BBB disruption, a significant difference in favorable outcome of 64% in SBP 100-129 vs. 39% in SBP 130-160 group (OR 5.93, 95% CI 1.50-23.45, p=0.011) was found. There was no difference in symptomatic ICH, 90-day mortality, midline shift (≥5 mm), and hemicraniectomy, between BP or BBB groups.

CONCLUSIONS

BBB disruption on 3h post-EVT imaging and lower SBP was associated with favorable outcome. This imaging finding may guide targeted BP therapy and suggests need for a randomized control trial.

Temporal profiles of systolic blood pressure variability and neurologic outcomes after endovascular thrombectomy

Introduction

Observational studies have found an increased risk of hemorrhagic transformation and worse functional outcomes in patients with higher systolic blood pressure variability (BPV). However, the time-varying behavior of BPV after endovascular thrombectomy (EVT) and its effects on functional outcome have not been well characterized.

Patients and methods

We analyzed data from an international cohort of patients with large-vessel occlusion stroke who underwent EVT at 11 centers across North America, Europe, and Asia. Repeated time-stamped blood pressure data were recorded for the first 72 h after thrombectomy. Parameters of BPV were calculated in 12-h epochs using five established methodologies. Systolic BPV trajectories were generated using group-based trajectory modeling, which separates heterogeneous longitudinal data into groups with similar patterns.

Results

Of the 2041 patients (age 69 ± 14, 51.4% male, NIHSS 15 ± 7, mean number of BP measurements 50 ± 28) included in our analysis, 1293 (63.4%) had a poor 90-day outcome (mRS ⩾ 3) or a poor discharge outcome (mRS ⩾ 3). We identified three distinct SBP trajectories: low (25%), moderate (64%), and high (11%). Compared to patients with low BPV, those in the highest trajectory group had a significantly greater risk of a poor functional outcome after adjusting for relevant confounders (OR 2.2; 95% CI 1.2-3.9; p = 0.008). In addition, patients with poor outcomes had significantly higher systolic BPV during the epochs that define the first 24 h after EVT (p < 0.001).

Discussion and conclusions

Acute ischemic stroke patients demonstrate three unique systolic BPV trajectories that differ in their association with functional outcome. Further research is needed to rapidly identify individuals with high-risk BPV trajectories and to develop treatment strategies for targeting high BPV.

Association Between Cerebral Autoregulation and Long-Term Outcome in Patients With Acute Ischemic Stroke

BACKGROUND

Dynamic cerebral autoregulation (CA) is known to be impaired in patients with acute ischemic stroke (AIS), but whether or not dynamic CA can predict long-term outcomes is unclear.

MATERIALS AND METHODS

This prospective study included 103 patients with AIS between September 2017 and April 2019. We measured the middle cerebral artery blood flow velocity and blood pressure within 7 days of AIS onset using a transcranial Doppler and Finometer, respectively. We conducted transfer function analysis to calculate dynamic CA indices (phase and gain), with lower phase and higher gain parameters reflecting less efficient CA. We followed up all patients after 3 and 12 months. Patients with 12-month modified Rankin Scale scores of <2 and ≥2 were defined as having favorable and unfavorable outcomes, respectively. We then analyzed the predictors of unfavorable outcomes after 3 and 12 months using logistic regression.

RESULTS

The ipsilesional phase parameter was significantly lower in patients with unfavorable outcomes than in those with favorable outcomes. Multiple logistic regression analysis revealed that the ipsilesional phase parameter and the National Institutes of Health Stroke Scale score were nonmodifiable predictors of short-term and long-term outcomes. Moreover, in receiver operating characteristic analysis, the area under the curve of the ipsilesional phase parameter was 0.646 (95% confidence interval: 0.513-0.779, P =0.044). Notably, the optimal cut-off value was 20.33 degrees (sensitivity: 63%, specificity: 70%).

CONCLUSION

Dynamic CA is an independent predictor of outcomes at 3 and 12 months in patients with AIS.

The utility of therapeutic hypothermia on cerebral autoregulation

Cerebral autoregulation (CA) dysfunction is a strong predictor of clinical outcome in patients with acute brain injury (ABI). CA dysfunction is a potential pathologic defect that may lead to secondary injury and worse functional outcomes. Early therapeutic hypothermia (TH) in patients with ABI is controversial. Many factors, including patient selection, timing, treatment depth, duration, and rewarming strategy, impact its clinical efficacy. Therefore, optimizing the benefit of TH is an important issue. This paper reviews the state of current research on the impact of TH on CA function, which may provide the basis and direction for CA-oriented target temperature management.

Intraoperative Cerebral Hemodynamic Monitoring during Carotid Endarterectomy via Diffuse Correlation Spectroscopy and Near-Infrared Spectroscopy

Objective: This pilot study aims to show the feasibility of noninvasive and real-time cerebral hemodynamic monitoring during carotid endarterectomy (CEA) via diffuse correlation spectroscopy (DCS) and near-infrared spectroscopy (NIRS). Methods: Cerebral blood flow index (CBFi) was measured unilaterally in seven patients and bilaterally in seventeen patients via DCS. In fourteen patients, hemoglobin oxygenation changes were measured bilaterally and simultaneously via NIRS. Cerebral autoregulation (CAR) and cerebrovascular resistance (CVR) were estimated using CBFi and arterial blood pressure data. Further, compensatory responses to the ipsilateral hemisphere were investigated at different contralateral stenosis levels. Results: Clamping of carotid arteries caused a sharp increase of CVR (~70%) and a marked decrease of ipsilateral CBFi (57%). From the initial drop, we observed partial recovery in CBFi, an increase of blood volume, and a reduction in CVR in the ipsilateral hemisphere. There were no significant changes in compensatory responses between different contralateral stenosis levels as CAR was intact in both hemispheres throughout the CEA phase. A comparison between hemispheric CBFi showed lower ipsilateral levels during the CEA and post-CEA phases (p < 0.001, 0.03). Conclusion: DCS alone or combined with NIRS is a useful monitoring technique for real-time assessment of cerebral hemodynamic changes and allows individualized strategies to improve cerebral perfusion during CEA by identifying different hemodynamic metrics.

Cerebral Circulation Time After Thrombectomy: A Potential Predictor of Outcome After Recanalization in Acute Stroke

Background

Despite successful recanalization, up to half of patients with acute ischemic stroke caused by large‐vessel occlusion treated with endovascular treatment (EVT) do not recover to functional independence. We aim to evaluate the role of cerebral circulation time (CCT) as outcome predictor after EVT.

Methods and Results

We retrospectively enrolled consecutive patients with acute ischemic stroke–large‐vessel occlusion undergoing EVT. Three categories of CCT based on digital subtraction angiography were studied: CCT of the stroke side, CCT of the healthy side), and change of CCT of the stroke side versus CCT of the healthy side. Dramatic clinical recovery was defined as a 24‐hour National Institutes of Health Stroke Scale score ≤2 or ≥8 points drop. A modified Rankin Scale score ≤2 at 3 months was considered a favorable outcome. Logistic regression analysis was performed to evaluate the prediction of CCT on prognosis. One hundred patients were enrolled, of which 38 (38.0%) experienced a dramatic clinical recovery and 43 (43.0%) achieved a favorable outcome. Logistic regression analysis found that shorter change of CCT of the stroke side versus CCT of the healthy side and CCT of the stroke side were independent positive prognostic factors for dramatic clinical recovery (odds ratio [OR], 0.189; P=0.033; OR, 0.581; P=0.035) and favorable outcomes (OR, 0.142; P=0.020; OR, 0.581; P=0.046) after adjustment for potential confounders. A model including the change of CCT of the stroke side versus CCT of the healthy side also had significantly higher area under the curve values compared with the baseline model in patients with dramatic clinical recovery (0.780 versus 0.742) or favorable outcome (0.759 versus 0.713).

Conclusions

To our knowledge, this is the first report that CCT based on digital subtraction angiography data exhibits an independent predictive performance for clinical outcome in patients with acute ischemic stroke–large‐vessel occlusion after EVT. Given that this readily available CCT can provide alternative perfusion information during EVT, a prospective, multicenter trial is warranted.

Cerebral Augmentation Effect Induced by External Counterpulsation Is Not Related to Impaired Dynamic Cerebral Autoregulation in Ischemic Stroke

Background and Purpose

Dynamic cerebral autoregulation is impaired after ischemic stroke. External counterpulsation (ECP) augments the cerebral blood flow of patients with ischemic stroke by elevation of blood pressure (BP). We aimed to investigate if cerebral augmentation effects during ECP were associated with impaired dynamic cerebral autoregulation in patients after acute ischemic stroke.

Methods

Forty patients with unilateral ischemic stroke and large artery atherosclerosis in the anterior circulation territory within 7 days from symptom onset and eighteen healthy controls were recruited. We monitored changes in mean flow velocity over both middle cerebral arteries (MCA) by transcranial Doppler (TCD) before, during, and immediately after ECP. Cerebral augmentation index was MCA mean flow velocity increase in percentage during ECP compared with baseline to evaluate the augmentation effects of ECP. Spontaneous arterial BP and cerebral blood flow velocity in both bilateral MCAs were recorded using a servo-controlled plethysmograph and TCD, respectively. Transfer function analysis was used to derive the autoregulatory parameters, including phase difference (PD), and gain.

Results

The cerebral augmentation index in patients with stroke was significantly higher on both the ipsilateral and contralateral sides than that in controls, while the PD in patients with stroke was significantly lower on both sides than those in controls (all P < 0.05). The cerebral augmentation index did not correlate with PD and gain on either the ipsilateral or contralateral side of patients with stroke or in controls (all P > 0.05). The cerebral augmentation index of patients with stroke was significantly related to mean BP change on the ipsilateral side (R² = 0.108, P = 0.038).

Conclusion

The degree of ECP-induced cerebral augmentation effects as measured by the cerebral augmentation index did not correlate with the magnitude of impaired dynamic cerebral autoregulation.

Impact of Cerebral Autoregulation Monitoring in Cerebrovascular Disease: A Systematic Review

Cerebral autoregulation (CA) prevents brain injury by maintaining a relatively constant cerebral blood flow despite fluctuations in cerebral perfusion pressure. This process is disrupted consequent to various neurologic pathologic processes, which may result in worsening neurologic outcomes. Herein, we aim to highlight evidence describing CA changes and the impact of CA monitoring in patients with cerebrovascular disease, including ischemic stroke, intracerebral hemorrhage (ICH), and aneurysmal subarachnoid hemorrhage (aSAH). The study was preformed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. English language publications were identified through a systematic literature conducted in Ovid Medline, PubMed, and Embase databases. The search spanned the dates of each database's inception through January 2021. We selected case-control studies, cohort observational studies, and randomized clinical trials for adult patients (≥ 18 years) who were monitored with continuous metrics using transcranial Doppler, near-infrared spectroscopy, and intracranial pressure monitors. Of 2799 records screened, 48 studies met the inclusion criteria. There were 23 studies on ischemic stroke, 18 studies on aSAH, 5 studies on ICH, and 2 studies on systemic hypertension. CA impairment was reported after ischemic stroke but generally improved after tissue plasminogen activator administration and successful mechanical thrombectomy. Persistent impairment in CA was associated with hemorrhagic transformation, malignant cerebral edema, and need for hemicraniectomy. Studies that investigated large ICHs described bilateral CA impairment up to 12 days from the ictus, especially in the presence of small vessel disease. In aSAH, impairment of CA was associated with angiographic vasospasm, delayed cerebral ischemia, and poor functional outcomes at 6 months. This systematic review highlights the available evidence for CA disruption during cerebrovascular diseases and its possible association with long-term neurological outcome. CA may be disrupted even before acute stroke in patients with untreated chronic hypertension. Monitoring CA may help in establishing individualized management targets in patients with cerebrovascular disease.

Optimized mouse model of embolic MCAO: From cerebral blood flow to neurological outcomes

The embolic middle cerebral artery occlusion (eMCAO) model mimics ischemic stroke due to large vessel occlusion in humans and is amenable to thrombolytic therapy with rtPA. However, two major obstacles, the difficulty of the eMCAO surgery and unpredictable occurrence of clot autolysis, had impeded its application in mice. In this study, we modified catheters to produce suitable fibrin-rich embolus and optimized the eMCAO model using cerebral blood flow (CBF) monitored by both laser Doppler flowmetry (LDF) and 2D laser speckle contrast imaging (LSCI) to confirm occlusion of MCA. The results showed that longer embolus resulted in higher mortality. There was a compensatory increase in MCA territory perfusion after eMCAO associated with decreased infarct volume; however, this was only partly dependent on recanalization as clot autolysis was only observed in ∼30% of mice. Cortical CBF monitoring with LSCI showed that the size of peri-core area at 3 h displayed the best correlation with infarct volume that is attributed to compensatory collateral blood flow. The peri-core area best predicted functional outcome after eMCAO. In summary, we developed a reliable eMCAO mouse model that better mimics embolic ischemic stroke in humans, which will increase the potential for successful translation of stroke neuroprotective therapies.

Review of studies on dynamic cerebral autoregulation in the acute phase of stroke and the relationship with clinical outcome

Acute stroke is associated with high morbidity and mortality. In the last decades, new therapies have been investigated with the aim of improving clinical outcomes in the acute phase post stroke onset. However, despite such advances, a large number of patients do not demonstrate improvement, furthermore, some unfortunately deteriorate. Thus, there is a need for additional treatments targeted to the individual patient. A potential therapeutic target is interventions to optimize cerebral perfusion guided by cerebral hemodynamic parameters such as dynamic cerebral autoregulation (dCA). This narrative led to the development of the INFOMATAS (Identifying New targets FOr Management And Therapy in Acute Stroke) project, designed to foster interventions directed towards understanding and improving hemodynamic aspects of the cerebral circulation in acute cerebrovascular disease states. This comprehensive review aims to summarize relevant studies on assessing dCA in patients suffering acute ischemic stroke, intracerebral haemorrhage, and subarachnoid haemorrhage. The review will provide to the reader the most consistent findings, the inconsistent findings which still need to be explored further and discuss the main limitations of these studies. This will allow for the creation of a research agenda for the use of bedside dCA information for prognostication and targeted perfusion interventions.

Hemorrhagic Transformation After Ischemic Stroke: Mechanisms and Management

Symptomatic hemorrhagic transformation (HT) is one of the complications most likely to lead to death in patients with acute ischemic stroke. HT after acute ischemic stroke is diagnosed when certain areas of cerebral infarction appear as cerebral hemorrhage on radiological images. Its mechanisms are usually explained by disruption of the blood-brain barrier and reperfusion injury that causes leakage of peripheral blood cells. In ischemic infarction, HT may be a natural progression of acute ischemic stroke and can be facilitated or enhanced by reperfusion therapy. Therefore, to balance risks and benefits, HT occurrence in acute stroke settings is an important factor to be considered by physicians to determine whether recanalization therapy should be performed. This review aims to illustrate the pathophysiological mechanisms of HT, outline most HT-related factors after reperfusion therapy, and describe prevention strategies for the occurrence and enlargement of HT, such as blood pressure control. Finally, we propose a promising therapeutic approach based on biological research studies that would help clinicians treat such catastrophic complications.

Regulation of cerebral blood flow in humans: physiology and clinical implications of autoregulation

Brain function critically depends on a close matching between metabolic demands, appropriate delivery of oxygen and nutrients, and removal of cellular waste. This matching requires continuous regulation of cerebral blood flow (CBF), which can be categorized into four broad topics: 1) autoregulation, which describes the response of the cerebrovasculature to changes in perfusion pressure; 2) vascular reactivity to vasoactive stimuli [including carbon dioxide (CO2)]; 3) neurovascular coupling (NVC), i.e., the CBF response to local changes in neural activity (often standardized cognitive stimuli in humans); and 4) endothelium-dependent responses. This review focuses primarily on autoregulation and its clinical implications. To place autoregulation in a more precise context, and to better understand integrated approaches in the cerebral circulation, we also briefly address reactivity to CO2 and NVC. In addition to our focus on effects of perfusion pressure (or blood pressure), we describe the impact of select stimuli on regulation of CBF (i.e., arterial blood gases, cerebral metabolism, neural mechanisms, and specific vascular cells), the interrelationships between these stimuli, and implications for regulation of CBF at the level of large arteries and the microcirculation. We review clinical implications of autoregulation in aging, hypertension, stroke, mild cognitive impairment, anesthesia, and dementias. Finally, we discuss autoregulation in the context of common daily physiological challenges, including changes in posture (e.g., orthostatic hypotension, syncope) and physical activity.

Blood Pressure Management After Endovascular Thrombectomy

Endovascular thrombectomy (EVT) has changed the landscape of acute stroke therapy and has become the standard of care for selected patients presenting with anterior circulation large-vessel occlusion (LVO) stroke. Despite successful reperfusion, many patients with LVO stroke do not regain functional independence. Particularly, patients presenting with extremes of blood pressure (BP) or hemodynamic variability are found to have a worse clinical recovery, suggesting blood pressure optimization as a potential neuroprotective strategy. Current guidelines acknowledge the lack of randomized trials to evaluate the optimal hemodynamic management during the immediate post-stroke period. Following reperfusion, lower blood pressure targets may be warranted to prevent reperfusion injury and promote penumbral recovery, but adequate BP targets adjusted to individual patient factors such as degree of reperfusion, infarct size, and overall hemodynamic status remain undefined. This narrative review outlines the physiological mechanisms of BP control after EVT and summarizes key observational studies and clinical trials evaluating post-EVT BP targets. It also discusses novel treatment strategies and areas of future research that could aid in the determination of the optimal post-EVT blood pressure.

Delayed Cerebral Ischemia after Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) is the most feared complication of aneurysmal subarachnoid hemorrhage (aSAH). It increases the mortality and morbidity associated with aSAH. Previously, large cerebral artery vasospasm was thought to be the sole major contributing factor associated with increased risk of DCI. Recent literature has challenged this concept. We conducted a literature search using PUBMED as the prime source of articles discussing various other factors which may contribute to the development of DCI both in the presence or absence of large cerebral artery vasospasm. These factors include microvascular spasm, micro-thrombosis, cerebrovascular dysregulation, and cortical spreading depolarization. These factors collectively result in inflammation of brain parenchyma, which is thought to precipitate early brain injury and DCI. We conclude that diagnostic modalities need to be refined in order to diagnose DCI more efficiently in its early phase, and newer interventions need to be developed to prevent and treat this condition. These newer interventions are currently being studied in experimental models. However, their effectiveness on patients with aSAH is yet to be determined.

Brain Function Changes Induced by Intermittent Sequential Pneumatic Compression in Patients With Stroke as Assessed by Functional Near-Infrared Spectroscopy

OBJECTIVE

Intermittent sequential pneumatic compression (ISPC) can effectively promote cerebral perfusion and collateral blood supply in patients with stroke. However, the effects of ISPC on cerebral oscillations are still unclear.

METHODS

The tissue concentration of oxyhemoglobin and deoxyhemoglobin oscillations were measured by functional near-infrared spectroscopy under resting and ISPC conditions in 27 right-handed adult patients with stroke. Five characteristic frequency signals (I, 0.6-2 Hz; II, 0.145-0.6 Hz; III, 0.052-0.145 Hz; IV, 0.021-0.052 Hz; and V, 0.0095-0.021 Hz) were identified using the wavelet method. The wavelet amplitude (WA) and laterality index (LI) were calculated to describe the frequency-specific cortical activities.

RESULTS

The ISPC state of patients with ischemic stroke showed significantly increased WA values of the ipsilesional motor cortex (MC) in the frequency intervals III (F37 = 8.017), IV (F37 = 6.347), and V (F37 = 5.538). There was no significant difference in the WA values in the ISPC state compared with the resting state in patients with hemorrhagic stroke. Also, the LI values of the prefrontal cortex and MC in patients decreased more obviously in the ISPC state than in the resting state despite no significant difference.

CONCLUSION

The significantly increased WA values in the frequency intervals III, IV, and V in the MC of patients with ischemic stroke might be related to cortical activity in the MC in addition to increased cerebral perfusion. The decreased LI values in the prefrontal cortex and MC indicated that the ISPC may have had a positive effect on the functional rehabilitation of these regions.

IMPACT

This study provides a method for assessing the effects of ISPC on cerebral oscillations, and the results benefit the optimization of ISPC parameters in personalized treatment for the functional recovery of patients with stroke.

Blood-brain barrier disruption in atrial fibrillation: a potential contributor to the increased risk of dementia and worsening of stroke outcomes?

Atrial fibrillation (AF) has become one of the most significant health problems worldwide, warranting urgent answers to currently pending questions on the effects of AF on brain function. Recent evidence has emerged to show an association between AF and an increased risk of developing dementia and worsening of stroke outcomes. A healthy brain is protected by the blood–brain barrier (BBB), which is formed by the endothelial cells that line cerebral capillaries. These endothelial cells are continuously exposed to shear stress (the frictional force generated by blood flow), which affects endothelial cell structure and function. Flow disturbances as experienced during AF can disrupt the BBB and leave the brain vulnerable to damage. Investigating the plausible mechanisms in detail, linking AF to cerebrovascular damage is difficult in humans, leading to paucity of available clinical data. Here, we discuss the available evidence for BBB disruption during AF due to altered cerebral blood flow, and how this may contribute to an increased risk of dementia and worsening of stroke outcomes.

Cerebral Autoregulation in Ischemic Stroke: From Pathophysiology to Clinical Concepts

Ischemic stroke (IS) is one of the most impacting diseases in the world. In the last decades, new therapies have been introduced to improve outcomes after IS, most of them aiming for recanalization of the occluded vessel. However, despite this advance, there are still a large number of patients that remain disabled. One interesting possible therapeutic approach would be interventions guided by cerebral hemodynamic parameters such as dynamic cerebral autoregulation (dCA). Supportive hemodynamic therapies aiming to optimize perfusion in the ischemic area could protect the brain and may even extend the therapeutic window for reperfusion therapies. However, the knowledge of how to implement these therapies in the complex pathophysiology of brain ischemia is challenging and still not fully understood. This comprehensive review will focus on the state of the art in this promising area with emphasis on the following aspects: (1) pathophysiology of CA in the ischemic process; (2) methodology used to evaluate CA in IS; (3) CA studies in IS patients; (4) potential non-reperfusion therapies for IS patients based on the CA concept; and (5) the impact of common IS-associated comorbidities and phenotype on CA status. The review also points to the gaps existing in the current research to be further explored in future trials.

Blood pressure variability and outcomes after mechanical thrombectomy based on the recanalization and collateral status

BACKGROUND

Blood pressure (BP), recanalization status, and collateral circulation are important factors for cerebral autoregulation after stroke. We aimed to investigate the association of various BP variability (BPV) parameters with clinical outcomes after mechanical thrombectomy (MT) according to recanalization and collateral status.

METHODS

We included 502 consecutive patients who underwent MT due to anterior circulation large vessel occlusion stroke at three comprehensive stroke centers. BPV parameters were standard deviation (SD), maximum/minimum BP, coefficient of variation (CV) and successive variation (SV). The clinical outcomes included 90-day functional outcome assessed by modified Rankin Scale score and symptomatic intracranial hemorrhage (sICH).

RESULTS

Among the included patients, 219 (43.6%) achieved good functional outcomes and 59 (11.8%) developed sICH. After adjusting for confounders, higher systolic BP (SBP) variability [CV (odds ratio (OR), 1.089, p = 0.035), SV (OR, 1.082, p = 0.004). and SD (OR, 1.074, p = 0.027)] was associated with a lower likelihood of a favorable outcome. In addition, higher SBP [CV (OR, 1.156, p = 0.001) and SD (OR, 1.118, p = 0.001)] were significantly associated with increased odds of sICH. Moreover, the relationship between BPV and the outcomes depended on recanalization status. However, regardless of collateral status, a higher BPV after MT was associated with worse outcomes.

CONCLUSIONS

Higher SBP SD and CV during the first 24 h after MT was a powerful predictor of worse clinical outcomes, regardless of the collateral status. However, the effects of BPV on outcomes were more substantial among patients with successful reperfusion.

Time-evolving coupling functions for evaluating the interaction between cerebral oxyhemoglobin and arterial blood pressure with hypertension

PURPOSES

This study aimed to investigate the network coupling between arterial blood pressure (ABP) and changes in cerebral oxyhemoglobin concentration (Δ [O₂ Hb]/Δ [HHb]) oscillations based on dynamical Bayesian inference in hypertensive subjects.

METHODS

Two groups of subjects, consisting of 30 healthy (Group Control, 55.1 ± 10.6 y), and 32 hypertensive individuals (Group AH, 58.9 ± 8.7 y), participated in this study. A functional near-infrared spectroscopy system was used to measure the Δ [O₂ Hb] and Δ [HHb] signals in the bilateral prefrontal cortex (LPFC/RPFC), motor cortex (LMC/RMC), and occipital lobe (LOL/ROL) during the resting state (12 min). Based on continuous wavelet analysis and coupling functions, the directed coupling strength (CS) between ABP and cerebral hemoglobin was identified and analyzed in three frequency intervals (I: 0.6-2 Hz, II: 0.145-0.6 Hz, III: 0.01-0.08 Hz). The Pearson correlations between the CS and blood pressure parameters were calculated in the hypertension group.

RESULTS

In interval I, Group AH exhibited a significantly higher CS for the coupling from ABP to Δ [O₂ Hb] than Group Control in LMC, RMC, LOL, and ROL. In interval III, the CS from ABP to Δ [O₂ Hb] in LPFC, RPFC, LMC, RMC, LOL, and ROL was significantly higher in Group AH than in Group Control. For the patients with hypertension, diastolic blood pressure was negatively and pulse pressure was positively related to the CS from ABP to Δ [O₂ Hb] oscillations in interval III.

CONCLUSIONS

The higher CS from ABP to Δ [O₂ Hb] in interval I indicated that the components of cardiac activity in cerebral hemoglobin oscillations were more directly responsive to the changes in systematic ABP in patients with hypertension than in healthy subjects. Meanwhile, the higher CS from ABP to Δ [O₂ Hb] in interval III indicated that the cerebral hemoglobin oscillations were susceptible to changes in blood pressure in hypertensive subjects. The results may serve as evidence of impairment in cerebral autoregulation after hypertension. The Pearson correlation results showed that diastolic blood pressure and pulse pressure might be regarded as predictors of cerebral autoregulation function in patients with hypertension, and may be useful for hypertension stratification. This study provides novel insights into the interaction mechanism between ABP and cerebral hemodynamics and could help in the development of new assessment techniques for cerebral vascular disease.

Management of Elevated Blood Pressure After Stroke Thrombectomy for Anterior Circulation

Thrombectomy is superior to intravenous thrombolysis for patients with large vessel occlusion in acute ischemic stroke, but nearly half of the patients still experience poor functional outcomes. Elevated blood pressure (BP) is widely observed in acute ischemic stroke, and BP may be one of the modifiable parameters that can potentially influence the outcomes; however, only observational studies exist to support current guidelines, and the recommended range for BP after thrombectomy is too wide to meet the clinical requirement. Randomized controlled trials are therefore needed to better understand the relationship between BP and outcomes after thrombectomy. In this review, we introduce the current management of BP after thrombectomy and several aspects of postthrombectomy BP management that should be resolved in future clinical trials.

Blood Pressure Management Before, During, and After Endovascular Thrombectomy for Acute Ischemic Stroke

There is an absence of specific evidence or guideline recommendations on blood pressure management for large vessel occlusion stroke patients. Until randomized data are available, the periprocedural blood pressure management of patients undergoing endovascular thrombectomy can be viewed in two phases relative to the achievement of recanalization. In the hyperacute phase, prior to recanalization, hypotension should be avoided to maintain adequate penumbral perfusion. The American Heart Association guidelines should be followed for the upper end of prethrombectomy blood pressure: ≤185/110 mm Hg, unless post-tissue plasminogen activator administration when the goal is <180/105 mm Hg. After successful recanalization (thrombolysis in cerebral infarction [TICI]: 2b-3), we recommend a target of a maximum systolic blood pressure of < 160 mm Hg, while the persistently occluded patients (TICI < 2b) may require more permissive goals up to <180/105 mm Hg. Future research should focus on generating randomized data on optimal blood pressure management both before and after endovascular thrombectomy, to optimize patient outcomes for these divergent clinical scenarios.

Optimal Hemodynamic Parameters for Brain-injured Patients in the Clinical Setting: A Narrative Review of the Evidence

Defining optimal hemodynamic targets for brain-injured patients is a challenging undertaking. The physiological interference observed in various intracranial pathologies can have varying effects on cerebral physiology at different time points. This narrative review provides an overview of cerebral autoregulatory physiology and common misconceptions, and examines the physiological considerations and clinical evidence for determining optimal hemodynamic parameters in acutely brain-injured patients with relevance to modern neuroanesthesia and neurocritical care practice.

Impact of the Perioperative Blood Pressure on Clinical Outcome after Thrombectomy in Acute Basilar Artery Occlusion

AIM

Optimal blood pressure (BP) management in vertebrobasilar circulation stroke patients undergoing thrombectomy remains undetermined. We aimed to evaluate the impact of perioperative BP on clinical outcome after MT in acute basilar artery occlusion (BAO) patients.

METHODS

We retrospectively analyzed all consecutive patients hospitalized with acute basilar artery occlusion administered endovascular treatment within 24 h from January 2012 to July 2018 in Beijing Tiantan Hospital. BP was measured at regular intervals during the first 24 h after stroke onset, during and after thrombectomy. The clinical outcomes assessed at 3-month follow up were functional independence (mRS score of 0-2) and mortality (mRS score of 6).

RESULTS

Of the 187 treated patients, 157 were male; patient ages were 60±10 years. The median NIHSS on admission was 22. Totally in 179 patients had complete BP level assessment. In these individuals, univariate analysis revealed significant associations of postoperative Max SBP and Max MAP with mortality (all P < 0.05). Multivariate regression analysis also demonstrated that postoperative Max SBP (OR=0.964, 95% CI 0.941 to 0.987, P < 0.003) and Max MAP (OR=0.942, 95% CI 0.907 to 0.979, P < 0.002) were independent predictors of mortality.

CONCLUSIONS

In acute BAO patients administered thrombectomy, Max SBP between 120 and 160 mmHg may be associated with better outcome, with a trend of reduced risk of mortality.

Outcome predictors of intravenous thrombolytic therapy in acute ischemic stroke patients: an Egyptian center experiences

Background

Intravenous thrombolytic therapy remains the guideline-recommended treatment to improve outcomes after acute ischemic stroke. However, the functional outcome among patients with acute ischemic stroke after receiving intravenous thrombolytic therapy is influenced by huge variety of factors, and this was the aim of our study to evaluate the outcome predictors of intravenous thrombolytic therapy in a sample of Egyptian patients with acute ischemic stroke.

Methods

We enrolled 183 acute ischemic stroke patients who were treated with intravenous recombinant tissue plasminogen activator (IV rtPA) according to the last updated guidelines of American Heart Association and American Stroke Association (AHA/ASA) from February 2018 to February 2020; however, only 150 patients of them completed our study plan till the end. Data of study variables were collected, analyzed statistically and correlated with the functional outcome 3 months after receiving IV rtPA using the modified Rankin Scale (mRS).

Results

Good functional outcome was seen in 98 (65.3%) patients and poor functional outcome was seen in 52 (34.7%) patients. Multivariate analysis of the study variables was done to detect the significant independent predictors of the functional outcome. Atrial fibrillation (AF) (P value < 0.001*OR 6.28* (95% C.I)), hypertension (P value 0.001*OR 3.65*(95% C.I)), diabetes mellitus (DM) (P value 0.009*OR 2.805*(95% C.I)), increased National Institute of Health Stroke Scale (NIHSS) score 24 h after receiving IV rtPA (P value 0.003* OR 8.039* (95% C.I)), increased pulsatility index (PI) value in cerebral vessels at the same side of stroke lesion (P value 0.038* OR 42.48*(95% C.I)) were the significant independent predictors of poor functional outcome. On the other hand decreased NIHSS score 24 h after receiving IV rtPA (P value 0.003* OR 0.124*(95% C.I)), Normal value of PI in cerebral vessels at the same side of stroke lesion (P value 0.038* OR 42.48*(95% C.I)) were the significant independent predictors of good functional outcome.

Conclusion

Intravenous thrombolytic therapy improves the functional outcome of acute ischemic stroke patients. Also, AF, hypertension, DM, NIHSS 24 h after receiving IV rtPA and PI could be used as independent predictors of the functional outcome.

Dynamic Cerebral Autoregulation in Embolic Stroke of Undetermined Source

BACKGROUND AND PURPOSE

Dynamic cerebral autoregulation (dCA) in acute ischemic stroke is probably compromised. Although the characteristics of dCA in different types of stroke have been largely investigated, dCA in embolic stroke of undetermined source (ESUS) remains poorly understood. In this group, we aimed to elucidate the characteristics of dCA and their relevance to clinical outcomes.

METHODS

The study enrolled 77 ESUS patients and 50 controls. Bilateral cerebral blood flow velocities (CBFV) of middle cerebral arteries and arterial blood pressure were simultaneously recorded using a transcranial Doppler combined with a servo-controlled finger plethysmograph. Transfer function analysis was used to obtain dCA parameters including phase, gain, coherence at very low frequency (VLF) and low frequency (LF), and the rate of recovery (RoRc) of CBFV. A multivariable logistic regression model was established to explore the relationship between dCA and clinical outcomes.

RESULTS

Gain at VLF and LF, phase at LF, and RoRc of CBFV in bilateral hemispheres of the ESUS group were consistently worse than those of the control group (all P < 0.001). Bilateral RoRc of CBFV was significantly higher in patients with favorable outcomes than in those with unfavorable outcomes (stroke hemisphere: P < 0.001; non-stroke hemisphere, P = 0.029). Rate of recovery of CBFV in stroke hemisphere >13.3%/s was an independent predictor of favorable clinical outcomes (adjusted odds ratio = 30.95, 95% CI: 5.33-179.81, P < 0.001).

CONCLUSIONS

Dynamic cerebral autoregulation was relatively impaired in both stroke and non-stroke hemispheres in ESUS patients, and functioning dCA after ESUS may indicate favorable clinical outcomes.

The effect of head positioning on cerebral hemodynamics: Experiences in mild ischemic stroke

BACKGROUND AND PURPOSE

It is generally agreed that optimal head positioning is an important consideration in acute stroke management regime. However, there is limited literature investigating the effect of head positioning changes on cerebrovascular physiology in acute ischemic stroke (AIS). We aim to assess cerebral autoregulation (CA) and associated hemodynamic responses during gradual head positioning (GHP) changes, between AIS and controls.

METHODS

Cerebral blood flow velocity (CBFV, transcranial Doppler), blood pressure (BP, Finometer) and end-tidal CO₂ (capnography) were recorded between lying flat (0°) and sitting up (30°) head position, in 16 controls (8 women, mean age 57 ± 16 yrs) and 15 AIS patients (7 women, 69 ± 8 yrs). AIS patients carried out three visits at 13.3 ± 6.9 h, 4.8 ± 3.2 days and 93.9 ± 11.5 days from symptom onset, respectively.

RESULTS

AIS patients were significantly hypertensive (p = 0.005), hypocapnic (p < 0.001), and had lower CBFV (p = 0.02) compared to controls, in both head positions. When comparing 5-min FLAT to SIT head position, reductions in BP (both AIS and controls, p < 0.001) and CBFV (controls only: dominant hemisphere p = 0.001 and non-dominant hemisphere p = 0.05) were demonstrated. Of note, a reduction in autoregulation index was observed in AIS, after 5-min SIT head positioning, at all 3 visits (p = 0.018).

CONCLUSION

Key hemodynamic changes were demonstrated when the head position changes from 5-min FLAT to SIT head position (GHP) in mildly affected stroke patients. Importantly, these were associated with non-significant changes in CBFV but reduced measures of CA following AIS, which may be relevant in determining the optimal head position and the ideal timing of mobilisation. Clinical Trial Registration - URL: http://www.clinicaltrials.gov. Unique Identifier: NCT02932540.

Cerebral hemodynamics in stroke thrombolysis (CHiST) study

Despite careful patient selection, successful recanalization in intravenous thrombolysis is only achieved in approximately 50% of cases. Understanding changes in cerebral autoregulation during and following successful recanalization in acute ischemic stroke patients who receive intravenous thrombolysis, may inform the management of common physiological perturbations, including blood pressure, in turn reducing the risk of reperfusion injury. Cerebral blood velocity (Transcranial Doppler), blood pressure (Finometer) and end-tidal carbon dioxide (capnography) were continuously recorded in 11 acute ischemic stroke patients who received intravenous thrombolysis (5 female, mean ± SD age 68±12 years) over 4-time points, during and at the following time intervals after intravenous thrombolysis: 23.9±2.6 hrs, 18.1±7.0 days and 89.6±4.2 days. Reductions in blood pressure (p = 0.04) were observed during intravenous thrombolysis. Reductions in heart rate (p<0.005) and critical closing pressure [Affected hemisphere (p = 0.02) and non-affected hemisphere (p<0.005)] were observed post intravenous thrombolysis. End-tidal CO2 increased during the sub-acute and chronic stages (p = 0.028). Reduction in affected hemisphere phase at low frequency was observed during intravenous thrombolysis (p = 0.021) and at subsequent visits (p = 0.048). No changes were observed in cerebral blood velocity, coherence, gain and Autoregulation Index during the follow-up period. Intravenous thrombolysis in acute ischemic stroke patients induced changes in affected hemisphere phase and other key hemodynamic parameters, but not Autoregulation Index. Further investigation of cerebral autoregulation is warranted in a larger acute ischemic stroke cohort to inform its potential role in individualized management plans.

Dynamic Cerebral Autoregulation Post Endovascular Thrombectomy in Acute Ischemic Stroke

The development of the endovascular thrombectomy (EVT) technique has revolutionized acute stroke management for patients with large vessel occlusions (LVOs). The impact of successful recanalization using an EVT on autoregulatory profiles is unknown. A more complete understanding of cerebral autoregulation in the context of EVT may assist with post-procedure hemodynamic optimization to prevent complications. We examined cerebral autoregulation in 107 patients with an LVO in the anterior circulation (proximal middle cerebral artery (M1/2) and internal cerebral artery (ICA) terminus) who had been treated using an EVT. Dynamic cerebral autoregulation was assessed at multiple time points, ranging from less than 24 h to 5 days following last seen well (LSW) time, using transcranial Doppler ultrasound recordings and transfer function analysis. Complete (Thrombolysis in Cerebral Infarction (TICI) 3) recanalization was associated with a more favorable autoregulation profile compared with TICI 2b or poorer recanalization (p < 0.05), which is an effect that was present after accounting for differences in the infarct volumes. Less effective autoregulation in the first 24 h following the LSW time was associated with increased rates of parenchymal hematoma types 1 and 2 hemorrhagic transformations (PH1–PH2). These data suggest that patients with incomplete recanalization and poor autoregulation (especially within the first 24 h post-LSW time) may warrant closer blood pressure monitoring and control in the first few days post ictus.

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.

The Effects of Gradual Change in Head Positioning on the Relationship between Systemic and Cerebral Haemodynamic Parameters in Healthy Controls and Acute Ischaemic Stroke Patients

(1) Background: Larger blood pressure variability (BPv) in the first 3 h post-stroke onset increases pathophysiological effects such as infarct size, and leads to greater risk of disability, comorbidities and mortality at 90 days. However, there is limited information on the relationship between systemic and cerebral haemodynamic and variability parameters. (2) Objectives: This study determined the effect of a gradual change in head position (GHP) on cerebral blood flow velocity variability (CBFVv) and mean arterial blood pressure variability (MABPv), in healthy controls and acute ischaemic stroke (AIS) patients. Methods: CBFVv and MABPv were expressed as standard deviation (SD) and coefficient of variation. A total of 16 healthy controls (mean age 57 ± 16 years) were assessed over two visits, 12 ± 8 days apart, and 15 AIS patients (mean age 69 ± 8.5 years) were assessed over three visits (V1: 13.3 ± 6.9 h, V2: 4.9 ± 3.2 days and V3: 93.9 ± 11.5 days post-stroke). (3) Results: In response to GHP, MABPv does not initially increase, but over time MABPv showed a significant increase in response to GHP in AIS (visits 2 and 3) and controls (visit 2). Additionally, in response to GHP in AIS, CBFVv increased in the affected hemisphere. Lastly, in AIS, a significant correlation between CBFVv and MABPv, assessed by SD, was seen in the unaffected hemisphere, whereas this relationship was not demonstrated in the affected hemisphere. (4) Conclusions: To our knowledge, this is the first study to analyse the relationship between CBFVv and MABPv. Shedding light on the effect of head position on the relationship between cerebral blood flow and blood pressure is important to improve our understanding of the underlying effects of cerebral autoregulation impairment. This early mechanistic study provides evidence supporting supine head positioning in healthy controls and stroke patients, through demonstration of a reduction of MABPv and increase in CBFVv.

Hemodynamics and Hemorrhagic Transformation After Endovascular Therapy for Ischemic Stroke

Hemorrhagic transformation remains a potentially catastrophic complication of reperfusion therapies for the treatment of large-vessel occlusion ischemic stroke. Observational studies have found an increased risk of hemorrhagic transformation in patients with elevated blood pressure as well as a high degree of blood pressure variability, suggesting a link between hemodynamics and hemorrhagic transformation. Current society-endorsed guidelines recommend maintaining blood pressure below a fixed threshold of 180/105 mmHg regardless of thrombolytic or endovascular intervention. However, given the high recanalization rates with mechanical thrombectomy, it is unclear if the same hemodynamic goals from the pre-thrombectomy era apply. Also, individual patient factors such as the degree of reperfusion, infarct size, and collateral status likely need to be considered. In this review, we will discuss current evidence linking hemodynamics to hemorrhagic transformation after mechanical thrombectomy. In addition, we will review the clinical relevance of cerebral autoregulation in stroke, highlighting recent studies that have harnessed autoregulatory physiology to define and trend individualized limits of autoregulation. This review will go on to emphasize the translatability of this approach to stroke management. Finally, we will discuss novel statistical approaches like trajectory analysis to post-thrombectomy hemodynamics.

Cerebral autoregulation and response to intravenous thrombolysis for acute ischemic stroke

We hypothesized that knowledge of cerebral autoregulation (CA) status during recanalization therapies could guide further studies aimed at neuroprotection targeting penumbral tissue, especially in patients that do not respond to therapy. Thus, we assessed CA status of patients with acute ischemic stroke (AIS) during intravenous r-tPA therapy and associated CA with response to therapy. AIS patients eligible for intravenous r-tPA therapy were recruited. Cerebral blood flow velocities (transcranial Doppler) from middle cerebral artery and blood pressure (Finometer) were recorded to calculate the autoregulation index (ARI, as surrogate for CA). National Institute of Health Stroke Score was assessed and used to define responders to therapy (improvement of ≥ 4 points on NIHSS measured 24–48 h after therapy). CA was considered impaired if ARI < 4. In 38 patients studied, compared to responders, non-responders had significantly lower ARI values (affected hemisphere: 5.0 vs. 3.6; unaffected hemisphere: 5.4 vs. 4.4, p = 0.03) and more likely to have impaired CA (32% vs. 62%, p = 0.02) during thrombolysis. In conclusion, CA during thrombolysis was impaired in patients who did not respond to therapy. This variable should be investigated as a predictor of the response to therapy and to subsequent neurological outcome.

Early blood pressure management for endovascular therapy in acute ischemic stroke: A review of the literature

The perioperative optimal blood pressure targets during mechanical thrombectomy for acute ischemic stroke are uncertain, and randomized controlled trials addressing this issue are lacking. There is still no consensus on the optimal target for perioperative blood pressure in acute ischemic stroke patients with large vessel occlusion. In addition, there are many confounding factors that can influence the outcome including the patient's clinical history and stroke characteristics. We review the factors that have an impact on perioperative blood pressure change and discuss the influence of perioperative blood pressure on functional outcome after mechanical thrombectomy. In conclusion, we suggest that blood pressure should be carefully and flexibly managed perioperatively in patient-received mechanical thrombectomy. Blood pressure changes during mechanical thrombectomy were independently correlated with poor prognosis, and blood pressure should be maintained in a normal range perioperatively. Postoperative blood pressure control is associated with recanalization status in which successful recanalization requires normal range blood pressure (systolic blood pressure 120-140 mmHg), while non-recanalization requires higher blood pressure (systolic blood pressure 160-180 mmHg). The preoperative blood pressure targets for mechanical thrombectomy should be tailored based on the patient's clinical history (systolic blood pressure ≤185 mmHg). Blood pressure should be carefully and flexibly managed intraoperatively (systolic blood pressure 140-180 mmHg) in patient-received endovascular therapy.

Cerebral macro- and microcirculatory blood flow dynamics in successfully treated chronic hypertensive patients with and without white mater lesions

The mechanisms of high blood pressure (HBP) -related brain pathology progression remain relatively unclear. We investigated whether lowering BP in chronic HBP patients normalizes cerebral perfusion dynamics at resistance vessel and capillary levels. Sixty-seven patients with HBP and 49 age- and sex-matched healthy controls underwent simultaneous recordings of middle cerebral artery blood flow velocity (CBFV), BP, and end-tidal CO₂ concentration. Thirty-four controls and 28 patients underwent additional near-infrared spectroscopy recordings (oxygenated [O₂Hb] and deoxygenated [HHb] hemoglobin). Degree of microcirculatory white matter lesions was graded by Fazekas scale. Dynamic cerebral autoregulation (dCA) was assessed by transfer function analysis. BP was successfully lowered (patients = 89 ± 15 mm Hg, controls = 87 ± 17), but cerebrovascular resistance was higher in BP patients (p < 0.05). BP-CBFV phase was lower in very low frequency (VLF) (left/right: 48 ± 20°/44 ± 17; controls: 61 ± 20/60 ± 21; p < 0.001) and low frequency (LF) (34 ± 14/35 ± 14; controls: 48 ± 20/44 ± 17; p < 0.05) ranges. Gain was higher in VLF range (in %/ mm Hg 0.56 ± 0.44/0.59 ± 0.49; controls: 0.32 ± 0.29/0.34 ± 0.32; p ≤ 0.005). BP-CBFV phase and gain did not differ across Fazekas groups. Across all patients, the capillary phases and gains (CBFV-[O2Hb], CBFV-[HHb]) were comparable to controls. Successfully treated chronic HBP results in normal brain capillary hemodynamics while the resistance vessel state is disturbed (phase decrease, gain increase).

Stroke in Pregnancy: A Focused Update

Ischemic stroke (IS) and hemorrhagic stroke (HS) can be devastating complications during pregnancy and the puerperium that are thought to occur in approximately 30 in 100,000 pregnancies. In high-risk groups, such as women with preeclampsia, the incidence of both stroke subtypes, combined, is up to 6-fold higher than in pregnant women without these disorders. IS or HS may present in young women with atypical symptoms including headache, seizure, extremity weakness, dizziness, nausea, behavioral changes, and visual symptoms. Obstetric anesthesiologists who recognize these signs and symptoms of pregnancy-related stroke are well positioned to facilitate timely care. Acute stroke of any type is an emergency that should prompt immediate coordination of care between obstetric anesthesiologists, stroke neurologists, high-risk obstetricians, nurses, and neonatologists. Historically, guidelines have not addressed the unique situation of maternal stroke, and pregnant women have been excluded from the large stroke trials. More recently, several publications and professional societies have highlighted that pregnant women suspected of having IS or HS should be evaluated for the same therapies as nonpregnant women. Vaginal delivery is generally preferred unless there are obstetric indications for cesarean delivery. Neuraxial analgesia and anesthesia are frequently safer than general anesthesia for cesarean delivery in the patient with a recent stroke. Potential exceptions include therapeutic anticoagulation or intracranial hypertension with risk of herniation. General anesthesia may be appropriate when cesarean delivery will be combined with intracranial neurosurgery.

Pathophysiological and clinical considerations in the perioperative care of patients with a previous ischaemic stroke: a multidisciplinary narrative review

With an ageing population and increasing incidence of cerebrovascular disease, an increasing number of patients presenting for routine and emergency surgery have a prior history of stroke. This presents a challenge for pre-, intra-, and postoperative management as the neurological risk is considerably higher. Evidence is lacking around anaesthetic practice for patients with vascular neurological vulnerability. Through understanding the pathophysiological changes that occur after stroke, insight into the susceptibilities of the cerebral vasculature to intrinsic and extrinsic factors can be developed. Increasing understanding of post-stroke systemic and cerebral haemodynamics has provided improved outcomes from stroke and more robust secondary prevention, although this knowledge has yet to be applied to our delivery of anaesthesia in those with prior stroke. This review describes the key pathophysiological and clinical considerations that inform clinicians providing perioperative care for patients with a prior diagnosis of stroke.

Single mean arterial blood pressure drops during stroke thrombectomy under general anaesthesia are associated with poor outcome

Background

We examined the influence of periprocedural blood pressure (BP), especially critical BP drops, on 3-month functional outcome in stroke patients undergoing mechanical thrombectomy (MT) under general anaesthesia (GA).

Methods

We screened all patients with anterior circulation large vessel occlusion receiving MT under GA at our centre from January 2011 to June 2016 and selected those who had continuous invasive periinterventional BP monitoring. Clinical and radiological data were prospectively collected as part of an ongoing cohort study, monitoring data were extracted from electronic anaesthesia records. We used uni- and multivariable regression to investigate the association of BP values with unfavourable outcome, defined as modified Rankin Scale scores 3–6 3 months post-stroke.

Results

115 patients were included in this study (mean age 65.3 ± 13.0 years, 55.7% male). Periinterventional systolic, diastolic, and mean arterial BP (MAP) values averaged across MT had no effect on outcome. However, single BP drops were related to unfavourable outcome, with absolute MAP drops showing the highest association compared to both systolic and relative BP drops (with reference to pre-interventional values). The BP value with the strongest association with unfavourable outcome was identified as an MAP ever < 60 mmHg (p = 0.01) with a pronounced effect in patients with poor collaterals. An MAP < 60 mmHg remained independently associated with poor functional outcome in multivariable analysis (p < 0.01).

Conclusions

For patients undergoing MT under GA, single MAP drops < 60 mmHg are independently related to unfavourable 3-month outcome. Therefore, every effort should be made to prevent periinterventional hypotensive episodes, especially below this threshold.

Electronic supplementary material

The online version of this article (10.1007/s00415-020-09701-x) contains supplementary material, which is available to authorized users.

Changes on Dynamic Cerebral Autoregulation Are Associated with Delayed Cerebral Ischemia in Patients with Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Early identification of vasospasm prior to symptom onset would allow prevention of delayed cerebral ischemia (DCI) in aneurysmal subarachnoid hemorrhage (aSAH). Dynamic cerebral autoregulation (DCA) is a noninvasive means of assessing cerebral blood flow regulation by determining independence of low-frequency temporal oscillations of systemic blood pressure (BP) and cerebral blood flow velocities (CBFV).

METHODS

Eight SAH patients underwent prospectively a median of 7 DCA assessments consisting of continuous measurements of BCFV and BP. Transfer function analysis was applied to calculate average phase shift (PS) in low (0.07-0.2 Hz) frequency range for each hemisphere as continuous measure of DCA. Lower PS indicated poorer regulatory response. DCI was defined as a 2-point decrease in Glasgow Coma Score and/or infarction on CT.

RESULTS

Three subjects developed symptomatic vasospasm with median time-to-DCI of 9 days. DCI was significantly associated with lower PS over the entire recording period (Wald = 4.28; p = 0.039). Additionally, there was a significant change in PS over different recording periods after adjusting for DCI (Wald = 15.66; p = 0.001); particularly, a significantly lower mean PS day 3-5 after bleed (14.22 vs 27.51; p = 0.05).

CONCLUSIONS

DCA might be useful for early detection of symptomatic vasospasm. A larger cohort study of SAH patients is currently underway.

Anesthetic Management of Emergency Endovascular Thrombectomy for Acute Ischemic Stroke, Part 1: Patient Characteristics, Determinants of Effectiveness, and Effect of Blood Pressure on Outcome

In the United States, stroke ranks fifth among all causes of death and is the leading cause of serious long-term disability. The 2018 American Heart Association stroke care guidelines consider endovascular thrombectomy to be the standard of care for patients who have acute ischemic stroke in the anterior circulation when arterial puncture can be made within 6 hours of symptom onset or within 6-24 hours of symptom onset when specific eligibility criteria are satisfied. The aim of this 2-part review is to provide practical perspective on the clinical literature regarding anesthesia care of patients treated with endovascular thrombectomy. Part 1 (this article) reviews the development of endovascular thrombectomy and the determinants of endovascular thrombectomy effectiveness irrespective of method of anesthesia. The first aim of part 1 is to explain why rapid workflow and maintenance of blood pressure are necessary to help support the ischemic brain until, as a result of endovascular thrombectomy, reperfusion is accomplished. The second aim of part 1, understanding the nonanesthesia factors determining endovascular thrombectomy effectiveness, is necessary to identify numerous biases present in observational reports regarding anesthesia for endovascular thrombectomy. With this background, in part 2 (the companion to this article), the observational literature is briefly summarized, largely to identify its weaknesses, but also to develop hypotheses derived from it that have been recently tested in 3 randomized clinical trials of sedation versus general anesthesia for endovascular thrombectomy. In part 2, these 3 trials are reviewed both from a functional outcomes perspective (meta-analysis) and a methodological perspective, providing specifics regarding anesthesia and hemodynamic management. Part 2 concludes with a pragmatic approach to anesthesia decision making (sedation versus general anesthesia) and acute phase anesthesia management of patients treated with endovascular thrombectomy.