Cerebral Flow Velocity Research Articles

Artificial gravity: an effective countermeasure for microgravity-induced headward fluid shift?

Long-duration spaceflight is associated with pathophysiological changes in the intracranial compartment hypothetically linked to microgravity-induced headward fluid shift. This study aimed to determine whether daily artificial gravity (AG) sessions can mitigate these effects, supporting its application as a countermeasure to spaceflight. Twenty-four healthy adult volunteers (16 men) were exposed to 60 days of 6° head-down tilt bed rest (HDTBR) as a ground-based analog of chronic headward fluid shift. Subjects were divided equally into three groups: no AG (control), daily 30-min intermittent AG (iAG), and daily 30-min continuous (cAG). Internal carotid artery (ICA) stroke volume (ICASV), ICA resistive index (ICARI), ICA flow rate (ICAFR), aqueductal cerebral spinal fluid flow velocity (CSFV), and intracranial volumetrics were quantified at 3 T. MRI was performed at baseline, 14 and 52 days into HDTBR, and 3 days after HDTBR (recovery). A mixed model approach was used with intervention and time as the fixed effect factors and the subject as the random effect factor. Compared with baseline, HDTBR was characterized by expansion of lateral ventricular, white matter, gray matter, and brain + total intracranial cerebral spinal fluid volumes, increased CSFv, decreased ICASV, and decreased ICAFR by 52 days into HBTBR (All Ps < 0.05). ICARI was only increased 14 days into HDTBR (P < 0.05). Neither iAG nor cAG significantly affected measurements compared with HDTBR alone, indicating that 30 min of daily exposure was insufficient to mitigate the intracranial effects of headward fluid shift. Greater AG session exposure time, gravitational force, or both are suggested for future countermeasure research.NEW & NOTEWORTHY Brief exposure to continuous or intermittent artificial gravity via short-arm centrifugation was insufficient in mitigating the intracranial pathophysiological effects of the headward fluid shift simulated during head-down tilt bed rest (HDTBR). Our results suggest that greater centrifugation session duration, gravitational force, or both may be required to prevent the development of spaceflight-associated neuro-ocular syndrome and should be considered in future ground-based countermeasure studies.

Vascular Aging Entails Arterial Dilatation in Addition to Increased Arterial Stiffness

Introduction: The increase in arterial blood pressure occurring with aging is considered an important risk factor for end-organ damage in, among others, the brain. How exactly this risk emerges is largely unknown. Methods: We investigated the effect of aging on middle cerebral flow velocity (MCAFV) and noninvasive arterial blood pressure (NIBP) in 105 healthy volunteers aged 18 to 82 years. Both pulsatile signals were analyzed determining the first (Sys1) and second systolic peak (Sys2) and the diastolic flow velocity 560 ms after stroke onset (D560). Results: For NIBP, a linear increase was found with aging for Sys2 and D560 (0.72 and 0.14 mm Hg/year, respectively) but not for Sys1. For MCAFV, a linear decrease was found with aging for all variables, being more rapid for Sys1 than for Sys2 or D560 (−0.94, −0.41, and −0.54 cm/s/year, respectively). Both signals change from Sys1 dominant in young adults to increasingly Sys2 dominant in the elderly. Discussion: That MCAFV decreases with aging, whereas NIBP increases can best be explained by assuming arterial dilatation. Apart from the generally accepted increase in arterial stiffness, arterial dilatation may be an important additional factor in vascular aging: the loss of elastin allows arteries to dilate until restricted by arterial collagen. Conclusion: Normal values collected in this study support protocols for non-invasive monitoring that require a correction for age.

Clinical, radiological profile and prognostic role of transcranial color-coded duplex in cerebral venous thrombosis: a case-control study

BackgroundCerebral venous thrombosis is a rare type of stroke, occurring more among young individuals. The presentation is highly variable, and this can delay diagnosis and management, thereby affecting outcome. The aim is to study the clinical, radiological profile, risk factors for cerebral venous thrombosis (CVT) and the role of transcranial color-coded duplex (TCCD) in CVT prognosis among Egyptian patients.MethodsEighty CVT patients and 80 normal healthy individuals were included. Magnetic resonance imaging, magnetic resonance venography, and genetic thrombophilia tests were done for patients. Deep cerebral venous system was evaluated using B-mode transcranial color-coded duplex (TCCD) for both groups.ResultsShowed female predominance with gender specific risk factors being the most common etiology. The most common hereditary thrombophilia was homozygous factor V Leiden mutation and anti-thrombin III (AT III). Headache was the most common presentation. Forty-three patients had transverse sinus thrombosis. Regarding TCCD, there was an increase in mean blood flow velocities, peak flow velocities and end diastolic flow velocities in deep middle cerebral vein and basal veins in CVT group compared to control group. There was a positive correlation not reaching statistical significance between flow velocities in the deep venous system and modified Rankin Scale.ConclusionClinical presentation is extremely variable. In our population, homozygous factor V Leiden mutation and AT III deficiency were the most common. Increased deep cerebral venous system flow velocities using TCCD in patients with CVT reflect their venous hemodynamic state.

The effects of aneurysmal subarachnoid hemorrhage on cerebral vessel diameter and flow velocity

BackgroundTranscranial Doppler flow velocity is used to monitor for cerebral vasospasm following aneurysmal subarachnoid hemorrhage. Generally, blood flow velocities appear inversely related to the square of vessel diameter representing local fluid dynamics. However, studies of flow velocity-diameter relationships are few, and may identify vessels for which diameter changes are better correlated with Doppler velocity. We therefore studied a large retrospective cohort with concurrent transcranial Doppler velocities and angiographic vessel diameters. MethodsThis is a single-site, retrospective, cohort study of adult patients with aneurysmal subarachnoid hemorrhage, approved by the UT Southwestern Medical Center Institutional Review Board. Study inclusion required transcranial Doppler measurements within </= 24 hours of vessel imaging. Vessels assessed were: bilateral anterior, middle, posterior cerebral arteries; internal carotid siphons; vertebral arteries; and basilar artery. Flow velocity-diameter relationships were constructed and fitted with a simple inverse power function. A greater influence of local fluid dynamics is suggested as power factors approach two. Results98 patients were included. Velocity-diameter relationships are curvilinear, and well fit by a simple inverse power function. Middle cerebral arteries showed the highest power factors (>1.1, R2>0.9). Furthermore, velocity and diameter changed (P<0.033) consistent with the signature time course of cerebral vasospasm. ConclusionsThese results suggest that middle cerebral artery velocity-diameter relationships are most influenced by local fluid dynamics, which supports these vessels as preferred endpoints in Doppler detection of cerebral vasospasm. Other vessels showed less influence of local fluid dynamics, pointing to greater role of factors outside the local vessel segment in determining flow velocity.

Abstract Number ‐ 54: First Fully Automated Robotic Transcranial Doppler Optimization of Cerebral Blood Flow During Cardiac Revascularization Surgery

Introduction Current technologies including EEG and near infrared pulse oximetry for non‐invasive monitoring of cerebral blood flow during cardiac surgery have proven inadequate for perioperative stroke risk mitigation. Cerebral arterial flow velocity is an excellent indicator of cerebral blood flow making transcranial doppler ultrasound (TCD) an excellent alternative technology for operating room continuous cerebral monitoring. To date, TCD utilization in the operating room has been limited due to frequent movement‐related loss of signal requiring nearly continuous manual probe readjustment. The recent development of fully autonomous robotic TCD (aTCD) has overcome these technical limitations, opening the door for real‐time continuous noninvasive cerebral blood flow monitoring with simultaneous emboli detection. Methods A 47‐year‐old female patient was found to have preoperative complete occlusion of the proximal brachiocephalic artery producing a double cerebral steal phenomenon with retrograde flow in the right internal carotid and vertebral arteries into the subclavian. A preoperative aTCD study disclosed baseline markedly diminished blood flow in the right middle cerebral artery (MCA) fed exclusively by small‐diameter collaterals via the circle of Willis.Intraoperatively, robotic aTCD was used to continuously monitor blood flow in the bilateral MCAs and perform emboli detection. In response to movement‐related signal loss, the robotic aTCD autonomously adjusted the probe position to maintain continuous MCA insonation. Results Shortly after intubation, a small drop in mean arterial pressure led to a near‐total loss of cerebral perfusion to the entire right hemisphere. This perfusion decrease was detected by aTCD, triggering the anesthesiologist to rapidly correct blood pressure to ensure adequate cerebral perfusion as confirmed by the robotic system. The patient was then placed on bypass pump with deployment of a temporary Y‐graft from the pump to the subclavian artery distal to the vertebral branch point and to the aorta to temporarily reverse the double cerebral steal. Coronary bypass was then performed, throughout which cerebral flow velocities were monitored continuously with aTCD and maintained in the safe cerebral perfusion range by adjusting pump pressures. Following a three‐vessel coronary bypass graft, permanent brachiocephalic artery bypass grafts were placed from the proximal aorta to the right subclavian and the proximal common carotid artery.Postoperative aTCD disclosed correction of the previously diminished blood flow detected in the right MCA preoperatively. Brain MRI postoperatively confirmed the absence of acute stroke. Conclusions This case represents the first use of robotic aTCD for real time continuous cerebral blood flow monitoring and optimization during complex cardiac surgery. Our experience suggests that aTCD may improve patient outcomes, particularly during high‐risk cardiac surgical and interventional procedures. Further studies of this promising technology are now needed.

Volatile Sedation With Isoflurane in Neurocritical Care Patients After Poor-grade Aneurysmal Subarachnoid Hemorrhage

Volatile sedation after aneurysmal subarachnoid hemorrhage (aSAH) promises several advantages, but there are still concerns regarding intracranial hypertension due to vasodilatory effects. We prospectively analyzed cerebral parameters during the switch from intravenous to volatile sedation with isoflurane in patients with poor-grade (World Federation of Neurosurgical Societies grade 4-5) aSAH. Eleven patients were included in this prospective observational study. Between day 3 and 5 after admission, intravenous sedation was switched to isoflurane using the Sedaconda Anesthetic Conserving Device (Sedana Medical, Danderyd, Sweden). Intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygenation (PBrO2), cerebral mean flow velocities (MFVs; transcranial Doppler ultrasound) and regional cerebral oxygen saturation (rSO2, near-infrared spectroscopy monitoring), as well as cardiopulmonary parameters were assessed before and after the sedation switch (-12 to+12 hours). Additionally, perfusion computed tomography data during intravenous and volatile sedation were analyzed retrospectively for changes in cerebral blood flow. There were no significant changes in mean ICP, CPP, and PBrO2 after the sedation switch to isoflurane. Mean rSO2 showed a non-significant trend towards higher values, and mean MFV in the middle cerebral arteries increased significantly after the initiation of volatile sedation. Isoflurane sedation resulted in a significantly increased norepinephrine administration. Despite an increase in mean inspiratory pressure, we observed a significant increase in mean partial arterial pressure of carbon dioxide. Isoflurane sedation does not compromise ICP or cerebral oxygenation in poor-grade aSAH patients, but the significant depression of CPP could limit the use of volatiles in case of hemodynamic instability or high vasopressor demand.

Decreased Cerebral Flow Velocities from General Anesthesia are Not Associated with Cerebral Hyperperfusion Syndrome

Decreased Cerebral Flow Velocities from General Anesthesia are Not Associated with Cerebral Hyperperfusion Syndrome

Transcranial doppler as screening method for sickling crises in children with sickle cell anemia: a latin America cohort study

BackgroundSickle cell anemia (SCA) is the leading cause of childhood stroke. We aimed to evaluate whether altered cerebral flow velocities, as measured by transcranial Doppler (TCD), are associated with vaso-occlusive complications in addition to stroke in pediatric SCA patients.MethodsWe evaluated 37 children aged between 2 and 16 years with SCA who underwent screening for TCD between January 2012 and October 2018. Genotypic profiles and demographic data were collected, TCD examinations were performed during follow-up, and the presence of sickling crises was compared. Survival analyses were performed using simple frailty models, in which each predictor variable was analyzed separately in relation to the occurrence of a sickling crisis.ResultsThe variables related to sickle cell crises in the univariate analysis were peak systolic velocity (PSV) in the middle cerebral artery (MCA), hazard ratio (HR) 1.01 (1.00—1.02) p = 0.04; end-diastolic velocity (EDV) in the MCA, HR 1.02 (1.01—1.04) p = 0.01; time average mean maximum velocity (TAMMV) in the basilar artery (BA), HR 1.02 (1.00—1.04) p = 0.04; hemoglobin, HR 0.49 (0.38—0.65) p < 0.001; hematocrit, HR 0.78 (0.71—0.85) p < 0.001; leukocyte counts, HR 1.1 (1.05—1.15) p < 0.001; platelets counts, HR 0.997 (0.994—0.999) p = 0.02; and reticulocyte numbers, HR 1.14 (1.06—1.23) p < 0.001.ConclusionsOur results indicate PSV and EDV in the MCA and TAMMV in the BA as markers of risk for the occurrence of sickling crises in SCA.

Medición de las velocidades de flujo sanguíneo cerebral, desviación de la línea media y diámetro de la vaina del nervio óptico mediante ecografía en pacientes sometidos a craneotomía electiva: Estudio observacional prospectivo

BackgroundBrain ultrasound allows measuring the cerebral flow velocity, brain midline shift and optic nerve sheath diameter. Literature is scarce in determining the feasibility to perioperatively perform these measurements altogether and the cerebrovascular behavior in patients scheduled for elective craniotomy. MethodsWe assessed bilateral cerebral flow velocities, composite index, brain midline shift and optic nerve sheath diameter by cerebral ultrasound in patients scheduled for elective craniotomy before anesthetic induction, at extubation, and at 6 and 24 hours after.The aim was to assess the feasibility of brain ultrasound in patients for elective craniotomy and to describe the changes in cerebral flow velocities, brain midline shift and optic nerve sheath diameter from baseline values at different times in the postoperative period. ResultsSixteen patients were included, of these two were excluded from analysis due to an inadequate sonographic window. There were no changes throughout the study regarding cerebral flow velocity, brain midline shift nor optic nerve sheath diameter assessments. All parameters were maintained in the physiological range without significant variations during the procedure. No perioperative complications were detected. ConclusionsThe results of our study show the feasibility to perform a perioperative assessment of cerebral flow velocity, brain midline shift or optic nerve sheath diameter jointly and successfully to obtain additional information of baseline cerebral hemodynamics in patients scheduled for elective craniotomy and their postoperative changes during the first 24 hours. Future studies with lager samples are needed to address the efficacy of cerebral ultrasound as a monitoring tool.

Psoriasis and Cardiovascular Risk in Children: The Usefulness of Carotid Intima-Media Thickness.

Psoriasis is a skin disorder which mostly affects adults, beginning in childhood in almost one-third of patients. In adults it is associated with increased risk for cardiovascular diseases (CVD), while this association is still debated at younger age. Our aim was to evaluate the association between psoriasis and metabolic markers and cardiovascular findings in this age group. Twenty consecutive patients previously diagnosed with psoriasis (group A) were enrolled and compared with healthy non- psoriatic age- and sex-matched subjects (group B). The severity of the disease, CV risk factors, including anthropometric data with adiposity and its distribution, blood pressure (BP), laboratory metabolic tests, echocardiography and vascular ultrasound (transcranial echo-Doppler and carotid artery echo-Doppler with carotid intima-media thickness, cIMT) were performed for each subject. Personal history for CV risk, BP, anthropometric data were similar between the two groups, while familiar history for psoriasis was more frequent in group A (p < 0.02). C-IMT was significantly higher in group A compared to B (right, p = 0.001; left, p = 0.002). In addition, c-IMT was positively correlated with disease duration, triglycerides and triglycerides/glucose. Cerebral flow velocities, cardiac measurements, systo-diastolic function, ventricle geometry and mass were normal and comparable between the two groups, and did not correlate with CV risk factors. In childhood psoriasis c-IMT could represent a marker of pre-clinical cardiovascular involvement and contribute to start a personalized management, while cardiac findings seem to be normal in the early stage of disease. Longitudinal studies can clarify the progression of CV involvement in paediatric-onset psoriasis.

Cerebrovascular Effects of Lower Body Negative Pressure at 3T MRI: Implications for Long‐Duration Space Travel

Optic disc edema develops in most astronauts during long-duration spaceflight. It is hypothesized to result from weightlessness-induced venous congestion of the head and neck and is an unresolved health risk of space travel. Determine if short-term application of lower body negative pressure (LBNP) could reduce internal jugular vein (IJV) expansion associated with the supine posture without negatively impacting cerebral perfusion or causing IJV flow stasis. Prospective. Nine healthy volunteers (six women). 3T/cine two-dimensional phase-contrast gradient echo; pseudo-continuous arterial spin labeling single-shot gradient echo echo-planar. The study was performed with two sequential conditions in randomized order: supine posture and supine posture with 25 mmHg LBNP (LBNP25 ). LBNP was achieved by enclosing the lower extremities in a semi-airtight acrylic chamber connected to a vacuum. Heart rate, bulk cerebrovasculature flow, IJV cross-sectional area, fractional IJV outflow relative to arterial inflow, and cerebral perfusion were assessed in each condition. Paired t-tests were used to compare measurement means across conditions. Significance was defined as P < 0.05. LBNP25 significantly increased heart rate from 64 ± 9 to 71 ± 8 beats per minute and significantly decreased IJV cross-sectional area, IJV outflow fraction, cerebral arterial flow rate, and cerebral arterial stroke volume from 1.28 ± 0.64 to 0.56 ± 0.31 cm2 , 0.75 ± 0.20 to 0.66 ± 0.28, 780 ± 154 to 708 ± 137 mL/min and 12.2 ± 2.8 to 9.7 ± 1.7mL/cycle, respectively. During LBNP25 , there was no significant change in gray or white matter cerebral perfusion (P=0.26 and P=0.24 respectively) and IJV absolute mean peak flow velocity remained ≥4cm/sec in all subjects. Short-term application of LBNP25 reduced IJV expansion without decreasing cerebral perfusion or inducing IJV flow stasis. 1 TECHNICAL EFFICACY STAGE: 1.

Cerebral Hemodynamics and Carotid Atherosclerosis in Patients With Subcortical Ischemic Vascular Dementia.

A growing body of evidence indicates that atherosclerosis is correlated with cerebral small vessel disease and contributes to cognitive decline. This study aimed to explore the characteristics and contributions of intracranial hemodynamics and carotid atherosclerosis to cognitive dysfunction in subjects with subcortical ischemic vascular dementia (SIVD). Notably, 44 patients with SIVD, 30 patients with Alzheimer’s disease (AD), and 30 healthy controls (HCs) were recruited from our longitudinal MRI study for AD and SIVD (ChiCTR1900027943). The cerebral mean flow velocity (MFV) and pulsatility index (PI) of both anterior and posterior circulations, artery plaque, and lumen diameter in carotid arteries were investigated using transcranial Doppler and carotid ultrasound, respectively. Their correlations with cognitive function were analyzed in patients with dementia. Decreased MFV and increased PI were found in patients with SIVD and AD. Patients with SIVD showed lower MFV and higher PI in the bilateral posterior cerebral arteries compared to patients with AD. Increases in lumen diameter, number of arteries with plaque, and total carotid plaque score were found in patients with SIVD. The Mini-Mental State Examination score was positively correlated with the MFV and negatively correlated with the PI of most major cerebral arteries, while it was negatively correlated with the lumen diameter of the common carotid artery, number of arteries with plaque, and total carotid plaque score in patients with dementia. There were also correlations between these parameters of some arteries and memory and executive function. Our results provide additional evidence suggesting that the pathological changes in macrovascular structure and function are correlated with cognitive impairment in dementia patients with SIVD and to a lesser extent AD.

The Effect of Low-Dose Ketamine to Median Cerebral Artery's Mean Flow Velocity in Patients Underwent Noncerebral Surgery Under General Anesthesia

Abstract Background: Ketamine can provide sedation and analgesia in specific doses. Whereas most other anesthetic agents exert a suppressive effect on the cardiovascular system and can lower blood pressure, ketamine can have the opposite effect. Although it provides many benefits, the use of ketamine is still limited in patients who are at the risk of increased intracranial pressure, such as head injury and stroke. The present study aims to compare the mean flow velocity-medial cerebral artery's (MFV-MCA) in patients receiving propofol with patients receiving a low-dose combination of propofol and ketamine. Materials and Methods: This was an experimental study with a double-blind, randomized controlled trial design. A total of 58 ASA I-II patients who underwent surgery with general anesthesia technique were collected by the consecutive sampling technique. The sample was divided into two groups: Group A received a low dose of ketamine after the patient was induced with propofol and Group B received NaCl 0.9% after the patient was induced with propofol. We used transcranial Doppler to measure the MFV-MCA before, 5 min after, and 10 min after the administration of ketamine. Results: We found no statistical difference between the groups in terms of MFV-MCA values before ketamine administration (P = 0.908), 5 min after ketamine administration (P = 0.890), and 10 min after ketamine administration (P = 0.981). Conclusion: The administration of low-dose ketamin at 0.3 mg/kg after induction did not increase the MFV-MCA in patients who underwent general anesthesia using propofol.

HEMODIALYSIS REDUCES CEREBRAL BLOOD FLOW PULSATILITY AND SMALL VESSEL STIFFNESS

Objective: Cognitive decline is highly prevalent amongst end-stage renal disease (ESRD) patients and is accelerated upon initiation of hemodialysis (HD). ESRD increases aortic stiffness and blood flow pulsatility, which may damage small vessels of target organs such as the brain. In this pilot study, we aimed to evaluate the acute effect of HD on cerebral blood flow and regional arterial stiffness. Design and method: Before, every hour during, and after HD (T0-T4), we measured cerebral flow velocity (FV) using transcranial Doppler, blood pressure (BP) via digital finger cuff (Nexfin), cardiac activity using ECG, and aortic pulse wave velocity (PWV) with Mobile-O-Graph. FV pulsatility index (PI) and transit times between ECG peak and the foot of both FV and BP waveforms (cerebral dT; digital dT) were computed using in house MATLAB-based analysis. Changes during HD were evaluated with Generalized Estimating Equation models adjusting for multiple comparisons in SPSS 26.0. Results: In eight participants aged 63 ± 17 y. old (4 diabetics, 3 women), peak FV decreased from baseline at T1 and T2 (-11.2 cm/s, p = 0.007; -12.2 cm/s, p &lt; 0.001), PI decreased at T1 (0.81 to 0.77, p = 0.005), whilst minimum FV, mean BP and partial pressure of CO2 remained unchanged. Digital dT increased at T3 (0.19 to 0.22, p &lt; 0.001) and cerebral dT increased early in HD (T1: p = 0.036; T2: p = 0.048), whereas aortic PWV did not change. Conclusions: During hemodialysis, cerebral and digital transit times increased, suggesting decreased stiffness of small peripheral vessels, without significant changes in aortic stiffness. Reduced stiffness of cerebral arteries may partially explain decreased cerebral flow pulsatility during HD.

POS-603 HEMODIALYSIS INDUCES TRANSIENT REDUCTIONS IN CEREBRAL BLOOD FLOW PULSATILITY AND REGIONAL ARTERIAL STIFFNESS

Cognitive decline is highly prevalent amongst end-stage renal disease (ESRD) patients and is accelerated upon initiation of hemodialysis (HD). ESRD increases aortic stiffness and blood flow pulsatility, which may damage small vessels of target organs such as the brain. In this pilot study, we aimed to evaluate the acute effect of HD on cerebral blood flow and its relation to arterial stiffness. Before, every hour during, and after HD (T0-T4), we measured cerebral flow velocity (FV) using transcranial Doppler, blood pressure (BP) via digital finger cuff (Nexfin), cardiac activity using ECG, and aortic pulse wave velocity (PWV) with Mobile-O-Graph. FV pulsatility index (PI) and transit times between ECG peak and the foot of both FV and BP waveforms (cerebral dT; digital dT) were computed using in house MATLAB-based analysis. Changes during HD were evaluated with Generalized Estimating Equation models adjusting for multiple comparisons in SPSS 26.0. In eight participants aged 63 ± 17 y. old (4 diabetics, 3 women), mean FV was significantly decreased from baseline at T1 and T2 (mean FV: -9.75 cm/s, p=0,012; -10.1 cm/s, p=0.012), peak FV was significantly decreased from baseline at T2 (-12.2 cm/s, p=0.031), PI decreased at T1 (0.81 to 0.77, p=0.005), whilst minimum FV, mean BP and partial pressure of CO2 remained unchanged. Digital dT increased at T3 (0.19 ± 0.01 to 0.22 ± 0.02, p<0.001) and cerebral dT increased throughout HD (T1-T4, p<0.005), whereas aortic PWV did not change. During hemodialysis, cerebral and digital transit times increased, suggesting decreased stiffness of small peripheral vessels, without significant changes in aortic stiffness. Reduced stiffness of cerebral arteries may partially explain decreased cerebral flow pulsatility.

Increased Ipsilateral Posterior Cerebral Artery P2-Segment Flow Velocity Predicts Hemodynamic Impairment.

Increased Transcranial Doppler flow velocity in the ipsilateral P2-segment of the posterior cerebral artery (PCA-P2: cm/second) is associated with recurrent cerebrovascular events in patients with unilateral internal carotid artery occlusion. However, its predictive value and correlation with hemodynamic impairment in an overall stroke patient cohort remains to be determined. Transcranial doppler PCA-P2 flow velocity was measured in 88 patients with symptomatic unilateral steno-occlusive disease who also underwent blood oxygenation-level dependent cerebrovascular reactivity imaging (blood oxygenation-level dependent [BOLD]-cerebrovascular reactivity [CVR]). A multivariate linear regression was used to evaluate the independent correlation between the ipsilateral PCA-P2 flow velocity measurements and hemispheric BOLD-CVR. Follow-up BOLD-CVR imaging data, available in 25 patients, were used to evaluate the temporal evolution of the BOLD-CVR and PCA-P2 flow velocity association using a mixed-effect model. Furthermore, a transcranial doppler cutoff for hemodynamic failure stage 2 was determined. The ipsilateral systolic PCA-P2 flow velocity strongly correlated with hemispheric BOLD-CVR (R=0.79; R2=0.61), which remained unchanged when evaluating the follow-up data. Using a PCA-P2 systolic flow velocity cutoff value of 85 cm/second, patients with BOLD-CVR based hemodynamic failure stage 2 were diagnosed with an area under the curve of 95. In patients with symptomatic unilateral steno-occlusive disease, increased ipsilateral transcranial doppler PCA-P2 systolic flow velocity independently correlates with BOLD-CVR based hemodynamic failure. A cutoff value of 85 cm/second appears to indicate hemodynamic failure stage 2, but this finding needs to be validated in an independent patient cohort.

Effects of different ventilation on cerebral oxygen saturation and cerebral blood flow before and after modified ultrafiltration in infants during ventricular septal defect repair.

To analyse the changes of different ventilation on regional cerebral oxygen saturation and cerebral blood flow in infants during ventricular septal defect repair. Ninety-two infants younger than 1 year were enrolled in the study. End-expiratory tidal pressure of carbon dioxide was maintained at 40-45 and 35-39mmHg in relative low and high ventilation groups. Regional cerebral oxygen saturation and flow velocity of the middle cerebral artery were recorded after anaesthesia (T0), cut pericardium (T1), separation from cardiopulmonary bypass (T2), the end of modified ultrafiltration, (T3) and at the end of operation (T4). The relative low ventilation group exhibited a significantly high regional cerebral oxygen saturation at each time point except for T2 (T0:77 ± 4, T1:76 ± 5, T3:76 ± 8, T4:76 ± 8, respectively, p < 0.001). Flow velocity of the middle cerebral artery in the relative low ventilation group was higher compared to the relative high ventilation group at each time point except for T2 (T0:53 ± 14, T1:54 ± 15, T3:53 ± 17, T4:52 ± 16, respectively, p < 0.001). Between the two groups, T2 showed the lowest middle cerebral artery flow velocity (relative low ventilation: 39 ± 15, relative high ventilation: 39 ± 11, p < 0.001). The infants' regional cerebral oxygen saturation and middle cerebral artery flow velocity performed better in the range of 40-45mmHg end-expiratory tidal pressure of carbon dioxide during CHD surgery. Modified ultrafiltration increased cerebral oxygen saturation. It was important to regulate ventilation in order to balance cerebral oxygen in infants.

Cerebrovascular Consequences of Elevated Intracranial Pressure After Traumatic Brain Injury.

We compared various descriptors of cerebral hemodynamics in 517 patients with traumatic brain injury (TBI) who had, on average, elevated (>23mmHg) or normal (<15mmHg) intracranial pressure (ICP). In a subsample of 193 of those patients, transcranial Doppler ultrasound (TCD) recordings were made. Arterial blood pressure (ABP), cerebral blood flow velocity (CBFV), cerebral autoregulation indices based on TCD (the mean flow index (Mx; the coefficient of correlation between the the cerebral perfusion pressure CPP and flow velocity) and the autoregulation index (ARI)), and the pressure reactivity index (PRx) were compared between groups. We also analyzed the TCD-based cerebral blood flow (CBF) index (diastolic CBFV/mean CBFV), the spectral pulsatility index (sPI), and the critical closing pressure (CrCP). Finally, we also looked at brain tissue oxygenation (cerebral oxygen partial tension (PbtO2)) in 109 patients. The mean cerebral perfusion pressure (CPP) was lower in the group with elevated ICP (p<0.01), despite a higher mean arterial pressure (MAP) (p<0.005) and worse autoregulation (as assessed with the Mx, ARI, and PRx indices), greater CrCP, a lower CBF index, and a higher sPI (all with p values of <0.001). Neither the mean CBFV nor PbtO2 reached significant differences between groups. Mortality in the group with elevated ICP was almost three times greater than that in the group with normal ICP (45% versus 17%). Elevated ICP affects cerebral autoregulation. When autoregulation is not working properly, the brain is exposed to ischemic insults whenever CPP falls.

Imaging Predictors of Vasospasm and Delayed Cerebral Ischaemia After Subarachnoid Haemorrhage

Acute spontaneous subarachnoid haemorrhage (SAH) is a severe disease, frequently complicated by vasospasm and delayed cerebral ischaemia (DCI), which have a negative impact on prognosis. Imaging studies are essential in the diagnosis of SAH. In this article, we review the available imaging techniques for prediction, monitoring and diagnosis of these complications of SAH. Non-contrast computed tomography (CT) and transcranial Doppler (TCD) have been so far the mainly used techniques to evaluate SAH patients during the acute stage of disease and to screen for vasospasm and DCI. However, there have been new developments of brain imaging techniques, with the introduction of automated methods to quantify blood volume and cerebral flow velocities, and the use of perfusion studies that could contribute to predict or diagnose such complications. Magnetic resonance (MR) imaging studies are proving useful to evaluate early brain injury and to diagnose DCI. Newer angiography suites have sophisticated post-processing tools that quantify cerebral haemodynamics in SAH and may provide important clues for the diagnosis of vasospasm. Imaging studies are part of the standard management of patients with acute SAH. Blood quantification on CT and the evaluation of cerebral flow velocities on TCD are known to predict and monitor the occurrence of vasospasm. DCI has increasingly been recognized as the most clinically relevant complication of SAH but also the most difficult to predict. MR imaging is the most sensitive tool to diagnose DCI. Future developments in imaging are needed to predict this important complication and help to improve the prognosis of patients with SAH.

Transcranial Doppler Sonography for Detecting Stenosis or Occlusion of Intracranial Arteries in People with Acute Ischemic Stroke in Neurocritical Care Unit.

Introduction: A Transcranial Doppler (TCD) is an inexpensive noninvasive ultrasonography technique that helps provide a rapid real time measure of blood flow from the basal intracerebral vessels, which may be used for the diagnosis and follow-up of cerebrovascular disease. By placing the ultrasound probe on the scalp; it utilizes low frequency soundwaves to record cerebral blood flow velocity, and its change in multiple conditions. Technology offers several diagnostic tests available in the evaluation and treatment of cerebrovascular diseases (CVD). Transcranial ultrasonography may represent a valuable tool for patients with CVD in neurocritical care unit. However due to geographic, financial or patient tolerance of procedures, physicians may be limited to the tools they can utilize. Method: Diagnostic accuracy of transcranial ultrasonography in acute stroke was subjected to systematic review. This study will set to demonstrate that the Transcranial Doppler (TCD) ultrasound is a viable piece of technology, which overcomes barriers mentioned in both the diagnosis and treatment of CVD. Cerebral flow peak systolic velocity (CBFVs), mean flow velocity (CBFVm), and the end diastolic velocity CBFVd) values are three components, which characterize the spectral waveform derived from TCD. These flow velocities provide valuable physiologic perspectives in various intracranial pathologies. We have demonstrated TCD to be highly predictive of evidence of vasospasm in patients with an aneurysmal subarachnoid hemorrhage with a 95% confidence interval. In patients with traumatic brain injury, TCD has been shown to be effective with a 95% confidence interval in the assessment of intracranial pressure and cerebral flow velocity. For strokes, TCD was shown to be effective with an overall sensitivity of 83% for the diagnosis, prognosis and treatment of ischemic strokes. Results: Due to its portability, affordability, and noninvasive application along with the high confidence intervals seen in our study, our data suggests the successful application of TCD in various pathologies in both diagnosis and monitoring of patients with various CVD.