Changes In Mean Flow Velocity Research Articles

Effect of continuous 2MHz transcranial ultrasound as an adjunct to tenecteplase thrombolysis in acute anterior circulation ischemic stroke patients: an open labeled non-randomized clinical trial.

The treatment of acute ischemic stroke has improved in last few decades. While meta-analyses of several trials have established the safety and efficacy of Intravenous (IV) Tenecteplase thrombolysis, concomitant continuous transcranial doppler (TCD) ultrasound administration has not been assessed in any clinical trial. The aim of this study was to determine the effects of continuous 2MHz TCD ultrasound during IV Tenecteplase thrombolysis for Middle cerebral artery (MCA) stroke. A total of 19 patients were included, 13 received TCD ultrasound and 6 sham TCD with IV Tenecteplase. TCD spectrum and difference in Pre and post TCD parameters were measured. Asymptomatic hemorrhagic transformation of infarct wasseen in two patients. There was no mortality or clinical worsening in thesonothrombolysis group as against sham sonothrombolysis group. Median of peak systolic velocity wasincreased in both thesonothrombolysis (P = 0.0002) and sham sonothrombolysis group (P-value = 0.001). The difference in change in mean flow velocity between two groups, sonothrombolysis (11cm/sec)and sham sonothrombolysis (3.5cm/sec) were also significantly different (P = 0.014). This pilot work has established safety of continuous 30min TCD application along with IV Tenecteplase thrombolysis and it concludes thatconcomitant 2MHz TCD ultrasound administration significantly increased the MCA blood flow compared to chemothrombolysis alone.CTRI Registered Number: CTRI/2021/02/031418.

Transcranial Color-Coded Doppler Cerebral Hemodynamics Following Aerobic Exercise Training: Outcomes From a Pilot Randomized Clinical Trial.

An active lifestyle with regular exercise is thought to decrease or delay the onset of Alzheimer dementia through increasing blood flow to the brain. We examined the mean flow velocity (MFV) and pulsatility index (PI) in the middle cerebral arteries of individuals randomized into two groups-a Usual Physical Activity (UPA) group and an Enhanced Physical Activity (EPA) exercise intervention group-to determine if exercise training is related to changes in cerebral blood flow. We examined 23 participants, randomized into a UPA group (n=12) and an EPA group (n=11), with transcranial color-coded Doppler (TCCD) and cardiorespiratory fitness (VO2peak, mL/kg/min) testing at baseline and following a 26-week intervention. TCCD was used to measure MFV and PI. Participants in the EPA group completed supervised aerobic exercise training for 26 weeks. Kendall's tau b correlation was used to examine relationships between variables. The Wilcoxon Rank Sum tests were used to examine changes between the UPA and EPA groups. There was no significant change in MFV or PI in the UPA group or the EPA group (p-values >0.05) between baseline and 26 weeks; the change between the UPA and EPA groups was also not significant (p=0.603). There was no evidence of an association between change in VO2peak and change in MFV or PI (all p-values >0.05). Participants in the EPA group significantly increased their VO2peak compared to the UPA group (p=0.027). This study did not demonstrate evidence of a significant change in the MFV in the middle cerebral arteries or evidence of a significant change in the PI between UPA and EPA groups. Future studies should be performed in larger cohorts and should consider use of personalized exercise programs to maximize understanding of how cerebrovascular hemodynamics change in structure and function with exercise for adults at risk for Alzheimer dementia.

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

Background and PurposeDynamic 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.MethodsForty 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.ResultsThe 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).ConclusionThe 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.

Functional transcranial Doppler: Selection of methods for statistical analysis and representation of changes in flow velocity.

IntroductionTranscranial Doppler (TCD) is a method used to study cerebral hemodynamics. In the majority of TCD studies, regression analysis and analysis of variance are the most frequently applied statistical methods. However, due to the dynamic and interdependent nature of flow velocity, nonparametric tests may allow for better statistical analysis and representation of results.MethodThe sample comprised 30 healthy participants, aged 33.87 ± 7.48 years; with 33% (n = 10) females. During a visuo‐motor task, the mean flow velocity (MFV) in the middle cerebral artery (MCA) was measured using TCD. The MFV was converted to values relative to the resting state. The results obtained were analyzed using the general linear model (GLM) and the general additional model (GAM). The fit indices of both analysis methods were compared with each other.ResultsBoth MCAs showed a steady increase in MFV during the visuo‐motor task, smoothly returning to resting state values. During the first 20 seconds of the visuo‐motor task, the MFV increased by a factor of 1.06 ± 0.07 in the right‐MCA and by a factor of 1.08 ± 0.07 in the left‐MCA. GLM and GAM showed a statistically significant change in MFV (GLM:F(2, 3598) = 16.76, P < .001; GAM:F(2, 3598) = 21.63, P < .001); together with effects of hemispheric side and gender (GLM:F(4, 3596) = 7.83, P < .005; GAM:F(4, 3596) = 2.13, P = .001). Comparing the models using the χ2 test for goodness of fit yields a significant difference χ2 (9.9556) = 0.6836, P < .001.ConclusionsBoth the GLM and GAM yielded valid statistical models of MFV in the MCA in healthy subjects. However, the model using the GAM resulted in improved fit indices. The GAM's advantage becomes even clearer when the MFV curves are visualized; yielding a more realistic approach to brain hemodynamics, thus allowing for an improvement in the interpretation of the mathematical and statistical results. Our results demonstrate the utility of the GAM for the analysis and representation of hemodynamic parameters.

Use of Transcranial Doppler as a Biomarker of CAR T Cell-Related Neurotoxicity.

To examine the relationship between transcranial Doppler (TCD) mean flow velocity (MFV) and the severity and temporal onset of neurotoxicity after chimeric antigen receptor (CAR) T-cell therapy in patients with relapsed lymphoma. We identified a cohort of 165 patients with relapsed or refractory B-cell lymphoma who received CAR T-cell therapy. TCDs were performed at baseline, treatment day 5, and throughout hospitalization based on development of neurologic symptoms. We assessed the percent change in velocity from baseline in each of the 6 major supratentorial arteries and the relationship of these values to development and timing of neurotoxicity. Our cohort was 30% female with an average age of 60 years. Of patients with TCDs performed, 63% developed neurotoxicity, and 32% had severe neurotoxicity. The median time of neurotoxicity onset was day 7. Higher maximum percent change in MFV across all vessels was significantly associated with likelihood of developing neurotoxicity (p = 0.0002) and associated with severe neurotoxicity (p = 0.0421). We found that with increased percent change in MFV, the strength of correlation between day of TCD velocity change and day of neurotoxicity onset increased. There was no single vessel in which increase in MFV was associated with neurotoxicity. Our study demonstrates an association between increase in TCD MFV and the development of neurotoxicity, as well as timing of neurotoxicity onset. We believe that TCD ultrasound may be used as a bedside functional biomarker in CAR T-cell patients and may guide immunologic interventions to manage toxicity in this complex patient group.

Confounding of Cerebral Blood Flow Velocity by Blood Pressure During Breath Holding or Hyperventilation in Transient Ischemic Attack or Stroke.

Background and Purpose- Breath holding (BH) and hyperventilation are used to assess abnormal cerebrovascular reactivity, often in relation to severity of small vessel disease and risk of stroke with carotid stenosis, but responses may be confounded by blood pressure (BP) changes. We compared effects of BP and end-tidal carbon dioxide (etCO2) on middle cerebral artery mean flow velocity (MFV) in consecutive transient ischemic attack and minor stroke patients. Methods- In the population-based, prospective OXVASC (Oxford Vascular Study) phenotyped cohort, change in MFV on transcranial Doppler ultrasound (ΔMFV, DWL-DopplerBox), beat-to-beat BP (Finometer), and etCO2 was measured during 30 seconds of BH or hyperventilation. Two blinded reviewers independently assessed recording quality. Dependence of ΔMFV on ΔBP and ΔetCO2 was determined by general linear models, stratified by quartiles. Results- Four hundred eighty-eight of 602 (81%) patients with adequate bone windows had high-quality recordings, more often in younger participants (64.6 versus 68.7 years; P<0.01), whereas 426 had hyperventilation tests (70.7%). During BH, ΔMFV was correlated with a rise in mean blood pressure (MBP; r2=0.15, P<0.001) but not ΔCO2 (r2=0.002, P=0.32), except in patients with ΔMBP <10% (r2=0.13, P<0.001). In contrast during hyperventilation, the fall in MFV was similarly correlated with reduction in CO2 and reduction in MBP (ΔCO2: r2=0.13, P<0.001; ΔMBP: r2=0.12, P<0.001), with a slightly greater effect of ΔCO2 when ΔMBP was <10% (r2=0.15). Stratifying by quartile, MFV increased linearly during BH across quartiles of ΔMBP, with no increase with ΔetCO2. In contrast, during hyperventilation, MFV decreased linearly with ΔetCO2, independent of ΔMBP. Conclusions- In older patients with recent transient ischemic attack or minor stroke, cerebral blood flow responses to BH were confounded by BP changes but reflected etCO2 change during hyperventilation. Correct interpretation of cerebrovascular reactivity responses to etCO2, including in small vessel disease and carotid stenosis, requires concurrent BP measurement.

Investigation of ischemic and demyelinating lesions by cerebral vasoreactivity based on transcranial Doppler sonography: a comparative study.

PurposeVariations of cerebral blood flow in response to hypoxia and hyperoxia in different disease conditions can provide new insights into disease etiopathogenesis. This study aimed to determine the characteristics of cerebral vasoreactivity for ischemia and demyelination.Materials and methodsThis case–control study included: 28 patients with lacunar infarctions verified by history, physical examination, and MRI; 28 age- and sex-matched healthy controls; 28 patients with relapsing–remitting multiple sclerosis (MS), based on McDonald criteria; and 28 age- and sex-matched healthy controls for the MS group. Transcranial Doppler sonography was undertaken in all subjects to calculate the mean flow velocity (MFV) of the right middle cerebral artery (MCA) and, after a breath-holding (BH) maneuver, the breath-holding index (BHI) was determined.ResultsThere was no significant difference of BHI and changes of MFV of the MCA in MS patients compared to controls (1.02 ± 0.4 vs 1.02 ± 0.3, p = 0.993; and 16.8 ± 8.1 vs 11.3 ± 10.8, p = 0.057). BHI in patients with lacunar infarctions was significantly lower (0.8 ± 0.4 vs 1.2 ± 0.3, p < 0.001) compared to controls. The BHI (p = 0.040) and variations of MFV of MCA (p = 0.007) in MS patients were significantly higher than in patients with lacunar infarctions. The vasoreactivity of demyelinating lesions was higher than that of ischemic ones.ConclusionTherefore, cerebral vasoreactivity determined by transcranial Doppler could be utilized for differentiating demyelinating from ischemic lesions.

Cerebrovascular Hemodynamics on Transcranial Doppler Ultrasonography and Cognitive Decline in Mild Cognitive Impairment.

Vascular risk factors and neurovascular dysfunction may be closely related to cognitive impairment and dementia. In this study, we evaluated the association between hemodynamic markers and longitudinal cognitive changes in patients with mild cognitive impairment (MCI). Furthermore, we investigated whether hemodynamic markers could predict the risk of progression to Alzheimer's disease (AD) in patients with MCI. A total of 68 subjects with amnestic MCI were recruited. Using transcranial Doppler (TCD) ultrasonography, cerebrovascular reactivity was evaluated with a breath-holding test (breath holding index; BHI) in addition to the mean flow velocity (MFV) and pulsatility index (PI) of the middle cerebral artery. We followed subjects for 24 months and each subject underwent neuropsychological testing and TCD ultrasonography, annually. According to the follow-up neuropsychological studies and clinical interviews at 12 months, we divided the patients with MCI into two groups: patients with stable cognitive performance and patients who progressed to AD. Lower BHI and higher PI were observed in patients who progressed to AD. The changes of MMSE score over the first 12 months correlated with lower baseline MMSE score and changes of MFV and BHI. The changes of MMSE score over 24 months were closely related to higher baseline resistance index and PI values. Multivariate logistic regression showed that abnormal baseline BHI value could predict a conversion from MCI to AD. We confirmed there is a close association between hemodynamic changes represented by TCD markers and cognitive decline, supporting the clinical value of hemodynamic markers in predicting MCI patients who will progress toAD.

Comparison of changes in mean flow velocity in anterior cerebral artery before and during cognitive stimulation between non-stroke and post-stroke people

Transcranial Doppler (TCD) is a tool that has been used widely to measure cerebral blood flow and changes in the cerebral autoregulatory mechanism that can be observed during cognitive stimulation task as changes in mean flow velocity (MFV). This cross-sectional study was to compare the anterior cerebral arteries (ACA) MFV changes during cognitive stimulation using TCD in post-stroke and control group in Neurology Department Adam Malik General Hospital. From August to December 2016, all subject underwent TCD examination to assess baseline characteristic both side of ACA; then the patients were stimulated using Stroop Task. During stimulation, we measured changes in MFV that were correlated with cerebral autoregulation in total 13 pairs of post-stroke and control recruited. Paired t-test was used to evaluate the difference in baseline and during stimulation for each post stroke and control group while independent t-test was used to determine the MFV changes difference between both groups. There were significant differences for MFV changes in each artery for control [R- ACA (p=0.001), L-ACA (p=0.001)] and post-stroke [R-ACA (p=0.001), L-ACA (p=0.001)]. Meanwhile, there was no significant difference for MFV elevation for arteries compared between groups [R-ACA (p=0.374) and L-ACA (0.272)].

Abstract TMP87: Non-Invasive Respiratory Impedance Enhances Cerebral Perfusion in Acute Stroke Patients

Introduction: Optimization of cerebral blood flow is a cornerstone of clinical management in a number of neurologic diseases, most notably acute ischemic stroke. Intra-thoracic pressure influences cardiac output and has the potential to impact cerebral blood flow (CBF). We aimed to quantify cerebral hemodynamic changes in acute ischemic stroke patients during increased respiratory impedance using a non-invasive oral device. Methods: Cerebral perfusion was measured during low (6cm H 2 0) and high (12cm H 2 0) levels of respiratory impedance in 20 patients within 72 hours of acute ischemic stroke. Microvascular CBF was measured by optical diffuse correlation spectroscopy, and middle cerebral artery mean flow velocity (MFV) was assessed by transcranial Doppler ultrasound. Results: High level respiratory impedance resulted in a 10% increase in MFV. Low level respiratory impedance resulted in a smaller (4%) non-significant change in MFV. Changes in cortical CBF were non-significant (figure). MFV varied across all studied levels (baseline vs low vs high, p=0.0017) with a significant test of trend (p=0.001), but this was not seen with microvascular CBF (p=0.33). Heart rate, cardiac output, and end tidal CO 2 remained stable during all levels of respiratory impedance. There was a small increase in mean arterial blood pressure at the low and high level of respiratory impedance, 4% (p=0.013) and 6% (p=0.017) respectively. All patients completed the protocol in its entirety, and the respiratory impedance exercise was well tolerated. Conclusions: Manipulating intrathoracic pressure via non-invasive respiratory impedance was safe and produced a small but measurable increase in cerebral blood flow in acute stroke patients. Future studies are warranted to assess whether respiratory impedance is feasible during hyperacute stroke management, and to determine the effect of volume status on the hemodynamic response to respiratory impedance.

Abstract WP322: Inhaled Nitric Oxide Augments Cerebral Blood Flow in Healthy Subjects

Introduction: Optimizing cerebral blood flow (CBF) is a cornerstone of clinical management for a number of neurologic disease states, most notably acute ischemic stroke. Transdermal nitric oxide donors are being investigated for acute stroke, though the effect of inhaled nitric oxide (iNO) on CBF remains largely unknown. Here we aim to quantify the cerebral hemodynamic response to iNO in healthy volunteers. Methods: Cerebral perfusion was measured during three doses of iNO (5ppm, 10ppm, and 20ppm) using the iNOMAX system (Mallinckrodt Pharmaceuticals) in 20 healthy volunteers. Continuous measurements of microvascular CBF were made with diffuse correlation spectroscopy (DCS), while middle cerebral artery mean flow velocity (MFV) was measured with transcranial Doppler. Cardiopulmonary status and nitric oxide toxicity (i.e. NO 2 ) were continuously monitored for safety. Results: Overall, iNO was safe and well tolerated. All subjects completed the protocol in its entirety. All 3 doses of iNO resulted in a small but statistically significant increase in microvascular CBF as compared to baseline (figure). No significant changes in MFV were identified (figure). During administration of iNO, there was no detrimental effect on blood pressure, nor was there any significant accumulation of toxic metabolites. Conclusions: iNO was safe and produced a small but significant increase in microvascular CBF in healthy volunteers. Future studies are warranted to determine the optimal dose of iNO and to explore the effect in acute ischemic stroke patients.

FV 3 Functional transcranial Doppler (fTCD) during cold-induced pain in the oral cavity and ice cream headache

Background An increase of mean flow velocity (MFV) in cerebral arteries can be monitored during processing of visual information ( [Aaslid, 1987] , [Rihs et al., 1999] ), while speaking ( Cupini et al., 1996 ), memory tasks ( Vollmer-Haase et al., 1998 ) and movements of one hand ( Orlandi and Murri, 1996 ) by functional transcranial Doppler (fTCD). The processing of sensitive information ( Duschek et al., 2012 ) or pain ( Mages et al., 2016 ) also leads to an increase in blood flow. Drinking ice-cold water can cause pain in the oral cavity and an ice cream headache ( Mages et al., 2016 ). In this study, it should be investigated whether the oral pain or the headache cause measurable changes of the MFV in the middle cerebral artery (MCA). Methods The MFV in both MCA were measured simultaneously during the drinking of 200 ml of lukewarm (22 °C) and 200 ml of ice-cold (0 °C) water in 77 young, healthy volunteers (see Fig. 1 ). After the experiments the occurrence of cold-induced pain in the oral cavity and ice cream headache was documented. Results See Table 1 . Discussion Drinking of liquid leads to a slight increase in the MFV in the ACM (lukewarm water: 2.8%, ice cold water 3.3%). The occurrence of ice cream headache is associated with a MFV increase of about 5% (difference group III with I). The MFV changes during cold-induced pain in the oral cavity are not significant and small (difference group IV and III 1.3%, group II and I 1.5%). Significant increases of MFV in subjects with cold-induced pain in the oral cavity and concomitant ice cream headache were observed. If the diameter of the MCA was constant, it can be concluded that the increase in MFV upon cold ingestion corresponds to an increase in cerebral blood flow.

Integrative Physiology of Brain Perfusion During Extreme Chemoreflex Manoeuvers

Both cerebral perfusion pressure (CPP) and vascular conductance (CVC) contribute to blood flow. Yet, rarely are these factors considered in cerebrovascular reactivity studies, in favour of the change in mean flow velocity (MFV) for a given dilatory stimulus such as carbon dioxide, an approach that can ignore the potential contributions of CPP. We tested the hypothesis that both CVC and CPP facilitate the increase cerebral perfusion during progressive chemoreflex stress. In healthy free divers (n=7; 1 female; age range = 22 to 34 years) middle cerebral artery MFV (transcranial Doppler ultrasound; Multigon), mean arterial pressure (MAP; Finometer), central venous pressure (CVP; dependent antecubital vein), end tidal CO2 (ETCO2; ADInstruments), and hemoglobin saturation (HbSat, pulse oximetry) were measured while CPP (MAP‐CVP) and CVC (MFV/CPP) were calculated. These indices were obtained at baseline, during a 2‐min preparatory phase of rebreathing to establish early effects on CVC and CPP, and then during i) extended rebreathe (RB), ii) apnea at total lung capacity (TLC), or iii) apnea at functional residual capacity (FRC); each stress assigned randomly and continued to volitional tolerance. ETCO2 increased 12–18 mmHg in all conditions (Effect of Time, P&lt;0.001; no Condition effect). The 59% HbSat level attained during RB was lower than FRC (78%) or TLC (80%) (Condition x Time interaction P&lt;0.001). MFV was similar at baseline (TLC, 52±11; FRC, 49±8; RB, 51±11 cm/s) and increased similarly (Time effect, P&lt;0.001) in TLC (111±17 cm/s), FRC (106±18 cm/s) and RB (108±11 cm/s; No Condition effect). CVC increased similarly in each condition (TLC, 49±11; FRC, 57±31; RB, 61±23%; Effect of Time P&lt;0.001; No Condition effect). Also, CPP increased similarly in each condition (TLC, 46±16%; FRC, 42±14%; RB, 36±16%; Time effect P&lt;0.001). The CVC response typically plateaued following the preparatory 2‐min rebreathe phase of each protocol whereas the majority of the CPP response occurred during the Apnea and extended rebreathe phases. Therefore, the determinants of the linear increase in MFV across the preparatory rebreathe phase, and the subsequent RB, TLC, or FRC condition phases, switched from a largely CVC mechanism at lower levels of stress, to increased CPP during the extended Apnea or RB manoeuvres, regardless of differences in HbSat.Support or Funding InformationNSERC discovery grant # 217916‐2013 awarded to J.K.S.

Oral Administration of Cilostazol Increases Ocular Blood Flow in Patients with Diabetic Retinopathy

PurposeTo investigate the effect of cilostazol on ocular hemodynamics and to determine whether the administration of cilostazol increases the ocular blood flow in patients with diabetic retinopathy.MethodsThis prospective observational study investigated the effect of orally administered cilostazol on diabetic retinopathy. Before and after administration for 1 week, pulsatile ocular blood flow (POBF) and retrobulbar hemodynamics were measured using a POBF analyzer and transcranial Doppler imaging, respectively. Visual acuity, intraocular pressure, and blood pressure were also evaluated before and after treatment.ResultsTwenty-five eyes of 25 patients were included in this study. POBF increased significantly (16.8 ± 4.6 µL/sec vs. 19.6 ± 6.2 µL/sec, p < 0.001) after administration of cilostazol, while no significant change was identified in visual acuity, intraocular pressure, and blood pressure. Mean flow velocity in the ophthalmic artery as measured with transcranial Doppler imaging also increased significantly after medication (23.5 ± 5.6 cm/sec vs. 26.0 ± 6.9 cm/sec, p = 0.001). The change in POBF directly correlated with the change in mean flow velocity (r = 0.419, p = 0.007).ConclusionsCilostazol was effective in increasing ocular blood flow in patients with diabetic retinopathy, possibly by modulating retrobulbar circulation.

Abstract WP350: Pumping Against Gravity - Cardiac Function Affects Fluctuations in Cerebral Blood Flow Caused by Head Position Change in Acute Ischemic Stroke

Introduction: Acute ischemic stroke (AIS) patients often have the head-of-bed (HOB) elevated to 30 0 while in the Emergency Department (ED). Flat HOB positioning has been shown to impact cerebral flow. Whether this holds true in undifferentiated, ED stroke patients is unknown. Hypothesis: We tested the hypothesis that 0 0 HOB positioning improves middle cerebral artery (MCA) mean flow velocity (MFV) in AIS compared to 30 0 . We secondarily tested the hypothesis that lower cardiac output (CO) is associated with greater fluctuation of MFV. Methods: This was a quasi-experimental study with repeat measurements of MCA MFV at 30 0 and 0 0 HOB position. Patients &gt; 18 years presenting to the ED within 12 hours of symptom onset and a NIHSS ≥ 4 were eligible. After applying non-invasive monitoring of mean arterial pressure (MAP) and CO, an investigator used transcranial Doppler to obtain bilateral MCA MFV at 30 0 and 0 0 HOB position. If a signal was unobtainable on the ischemic side, the contralateral MFV was used for analysis. The primary analysis comprised all subjects with confirmed stroke on subsequent imaging and included student t-test for continuous measures. Secondary analysis used multiple linear regression to test if baseline NIHSS, age, MAP and CO were associated with changes in MFV. Results: There were 38 subjects enrolled, of whom 32 had confirmed AIS and were included in analysis. The mean age was 66 (±15) years and NIHSS 7 (±6). Stroke location was mixed (50% lacunar, 25% posterior and 25% anterior circulation). Averaged across all subjects, the MFV did not significantly increase when changing the HOB position from a 30 0 to 0 0 (+0.7 cm/s, 95% CI -1.6 to 3.1). Nevertheless, 16% (95% CI 5-33%) of subjects had a ≥ 20% increase and 47% (95% CI 29-65%) had any increase in MFV at 0 0 compared to 30 0 HOB. Adjusting for age, NIHSS and MAP, lower CO was associated with greater change in MFV (+2 cm/s [95% CI 0.2-3.7 cm/s] for every 1 L/min lower cardiac output, p=0.03). Conclusions: In conclusion, in a mixed sample of ED AIS patients, lower HOB position does not significantly impact cerebral flow on average, yet a considerable proportion of individuals may benefit from lower HOB position. Low cardiac output may identify those that benefit most.

Parameters of Hemodynamic Instability Measured by Transcranial Doppler in Patients Undergoing Carotid Endarterectomy and Carotid Angioplasty-Stent: Comparison Between Groups

Background: Carotid atheromatosis causes 15-20% of ischemic stroke. Interventional treatment is sometimes limited by the risk of reperfusion, stroke and other complications. A better knowledge of hemodynamic changes along the procedures could help to establish the treatment in each patient. We aimed to gain insight into this employing transcranial Doppler (TCD) monitoring and determine conditions with a higher risk of complications. Methods: We prospectively recruited 53 patients with ≥ 70% cervical carotid stenosis or occlusion who underwent carotid angioplasty-stenting (CAS) (28 patients) or carotid endarterectomy (CEA) (25 patients). We performed TCD monitoring during the whole procedures. Results: Frequency of reperfusion syndrome (RS) was similar in both procedures, but other complications were more common (P < 0.001) in CEA. At baseline, hemodynamic reserve (HR) was correlated with asymmetry between mean flow velocity (MV) of middle cerebral arteries (MCAs) (r = -0.582; P = 0.003) and delayed systolic peak (r = -0.44; P = 0.02). Over 100% increase in MV after recanalization was associated with lower HR, but not to the RS. A more marked change in MV was associated with CAS procedure (P = 0.081), lack of orthodromic flow in ophthalmic artery (P = 0.013) and ≥ 95% carotid stenosis. Conclusions: Baseline asymmetry between MCA MVs and subsequent increase in the latter is related to parameters of hemodynamic instability, such as critical stenosis, endovascular procedure and loss of orthodromic flow in the OF. However, MV alone is not a good predictor of RS, despite of baseline MVs asymmetry related to impaired HR and peak systolic delay. RS is equally frequent in CEA and CAS techniques, while other complications are more common in the former. J Neurol Res. 2015;5(4-5):233-245 doi: http://dx.doi.org/10.14740/jnr351w

Head Position and Cerebral Blood Flow Velocity in Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

Background: Patients with acute ischemic stroke (AIS) have impaired vasomotor reactivity, especially in the affected cerebral hemisphere, such that they may depend directly on systemic blood pressure to maintain perfusion to vulnerable ‘at risk' penumbral tissue. As the sitting up position may affect cerebral perfusion by decreasing cerebral blood flow (CBF) in salvageable tissue, positioning AIS patients with their head in a lying flat position could increase CBF through collateral circulation or gravitational force. We wished to quantify the effect of different head positions on mean flow velocity (MFV) by transcranial Doppler ultrasonography (TCD) in AIS patients to assess the potential for benefit (or harm) of head positioning in a clinical trial. Methods: We performed a systematic review and meta-analysis of observational studies with TCD to evaluate differences in cerebral MFV between the lying flat and sitting up head positions in AIS. For each study and each comparison, we obtained the mean value of changes in MFV and its variance. Results: A total of 303 studies were identified, but 298 were excluded for varying reasons; 4 papers met the inclusion criteria and 57 patients were included in the meta-analysis for calculation of the overall mean difference in MFV. We found a significant increase in MFV from a bed angle of 30 to 15° (4.6 cm/s, 95% confidence interval, CI, 2.9-6.2, p < 0.001) and from 30 to 0° (8.3 cm/s, 95% CI 5.3-11.3, p < 0.001) in the affected hemisphere but not on the normal side in AIS patients. Conclusions: In AIS patients, MFV increased significantly in the side affected by the stroke but not in the unaffected side when they were positioned in a lying flat head position at 0 or 15° compared to an upright head position at 30°. The clinical significance of these findings is now undergoing further randomized evaluation in the international multicenter Head Position in Acute Stroke Trial (HeadPoST).

Middle cerebral artery mean flow velocity changes to non‐pharmacologically induced hypertension and hypotension in humans (1184.6)

Asymmetrical responses of cerebral blood flow in response to elevating vs. falling blood pressure has been reported using cyclic inflation and deflation of thigh cuffs in head injury patients and pharmacologically in healthy volunteers. Whether this phenomenon exists with non‐pharmacologically induced hypertension and hypotension is unknown. In this study, we examined the relative changes in cerebrovascular conductance index (CVCi), defined as percent changes in middle cerebral artery mean flow velocity / percent changes in mean arterial pressure, during transient hypertension vs. hypotension in 10 healthy male volunteers {age [median (range)]: 24 (22‐35 yrs), body weight [mean±SD: 72±12 kg]; maximal oxygen uptake: 55±5 ml/kg/min}. Transient hypertension and hypotension were induced via squat‐stand manoeuvres executed at 0.025, 0.05 and 0.1 Hz. The CVCi responses to hypertension (squat) compared to hypotension (stand) were attenuated at 0.05 Hz (0.57±0.38 vs. 1.84±0.56 %/%) and 0.1 Hz [0.83±0.41 vs. 1.59±0.57 %/%; all p&lt;0.01), but not at 0.025 Hz [0.86±0.30 vs. 1.12±0.31 %/%; p=0.1). These results suggest that the human cerebrovascular function is better adapted to combat non‐pharmacologically and physiologically relevant transient hypertension than transient hypotension.Grant Funding Source: Supported by a research contract from the Ministère de l’Éducation, du Loisir et du Sport (Québec)

Relative Changes in Transcranial Doppler Velocities Are Inferior to Absolute Thresholds in Prediction of Symptomatic Vasospasm after Subarachnoid Hemorrhage

The absolute transcranial Doppler (TCD) velocity threshold has been validated as a screening tool for vasospasm after subarchnoid hemorrhage (SAH). We assessed whether relative changes in velocity were superior to absolute TCD thresholds in the detection of symptomatic vasospasm. We reviewed consecutive patients with aneurysmal SAH who underwent serial TCD monitoring and survived at least 7days. We recorded initial flow velocity (IFV) and maximal flow velocity (MFV) of the middle cerebral artery (MCA) serially up to 14 days from admission. We calculated relative flow velocity changes (MFV/IFV) and maximum change in mean flow velocity (FVmean) over any consecutive 2 days in addition to standard absolute measures of Lindegaard ratio (LR) and FVmean. We calculated receiver operating characteristic curve and area under curve (AUC) values, sensitivity, specificity, and positive predictive and negative predictive values for these parameters, optimal cutpoints, and various combinations. Forty-eight of 211 patients (23%) developed symptomatic MCA vasospasm. AUC values for various TCD parameters were 0.80 for MCA MFV >175 cm/s, 0.71 for LR >6, 0.64 for MFV/IFV >2, and 0.64 for >70% change in MFV over 2 days. The best characteristics were observed for the combination of MFV >175 cm/s and/or maximal LR >6 (AUC 0.81). Our data suggest that absolute thresholds of TCD FVmean provide the most accurate prediction of symptomatic MCA vasospasm after SAH. Other thresholds, including relative change from baseline and day-to-day changes, are inferior to established absolute thresholds.

Impaired cerebral autoregulation in patients with shy-drager syndrome

It is still debated whether cerebral autoregulation is preserved in patients presenting Shy-Drager syndrome (SD). In order to evaluate cerebral autoregulation in this disease the authors studied 5 patients with SD and 5 healthy control subjects by means of transcranial Doppler. Changes in mean flow velocity (MV) in the middle cerebral artery (MCA), as well as changes of the systemic mean arterial blood pressure (MBP) were measured at the same time during a tilt-table test. When the patients were tilted from the rest to the orthostatic position, MCA MV showed a rapid and significant decrease in all SD patients (−52.8%); the MCA MV values remained low during 10 minutes at 90°; control patients did not show similar changes (−6.9%), (P=0.0003). Although MBP values showed a considerable decrease during the test in SD patients (−31.0%), these changes never went below the cerebral autoregulation threshold. The authors’ data are suggestive of an impairment of cerebral autoregulation in SD patients.