Cerebral Artery Blood Flow Research Articles

The effect of blood pressure and cardiac output on the quality of the surgical field and middle cerebral artery blood flow during endoscopic sinus surgery.

A clear surgical field is critical during endoscopic sinus surgery (ESS). Hypotensive anesthesia and cardiac output (CO) may optimize the surgical field; however, evidence of their effect on bleeding and cerebral blood flow is conflicting. The aim of this study was to evaluate the effect of blood pressure (BP) and CO on intraoperative bleeding and middle cerebral artery blood flow velocity (Vmca ) during ESS. This was a prospective randomized controlled trial. Patients undergoing ESS for chronic rhinosinusitis at a tertiary institution in 2013 were randomized to receive BP manipulation using target-controlled noradrenaline infusion during surgery to either their left or right sinuses. The contralateral side in each patient served as control. Bleeding was scored using a 0 to 10 point bleeding assessment scale (BAS, 0-10) and Vmca was measured using transcranial Doppler ultrasonography every 10 minutes or when surgically opportune, and time-matched with BP and CO. Data was analyzed using Bland-Altman methods. A total of 105 time points were collected across a mean arterial pressure (MAP) range of 32 to 118 mmHg. Significant correlations were demonstrated between MAP and Vmca (r = 0.7, p < 0.0001), MAP and BAS (r = 0.50, p < 0.0001), CO and Vmca (r = 0.57, p < 0.0001), and CO and BAS (r = 0.42, p < 0.0001). The best surgical fields were seen at 40 to 59 mmHg MAP. However, MAP below 60 mmHg produced >50% reduction in Vmca in more than 10% of time points. Balancing surgical visibility with organ perfusion remains a challenge. The results of this study show that moderate hypotension significantly improves the surgical field; however reducing BP below 60 mmHg may risk cerebral hypoperfusion.

Abstract 159: Posterior Communicating Artery Flow Diversion in Middle Cerebral Artery Stroke: Angiographic Evidence from IMS III

Background: Only 20% of adults have a “fetal” posterior communicating artery (PCOMM) with carotid flow to the posterior cerebral artery. Dynamic pressure changes at the circle of Willis due to proximal artery occlusion may restore such collateral blood flow patterns. We investigated the findings and implications of PCOMM blood flow in middle cerebral artery (MCA) stroke at angiography in IMS III. Methods: The angiography core lab prospectively evaluated PCOMM blood flow and collateral circulation in proximal MCA or M1 occlusion. Proximal or distal M1 occlusion was noted with PCOMM flow scored (0-2) on ipsilateral carotid injections before and after endovascular therapy, correlating PCOMM status with ASITN/SIR leptomeningeal collateral grade, TICI reperfusion and subsequent clinical outcomes. Results: 122 patients with M1 occlusion at angiography (60 proximal, 62 distal) had peri-procedural evaluation of PCOMM status and associated collateral grade. Ipsilateral carotid injections revealed PCOMM flow diversion in 87/122 (71%) prior to revascularization, including 41/60 (68%) in proximal M1 and 46/62 (74%) in distal M1 (p=0.61) occlusions. After treatment, PCOMM patency was noted in 86/122 (71%), with 40/60 (67%) in proximal M1 and 46/62 (74%) in distal M1 (p=0.48) occlusions. Decrease in PCOMM score after therapy was noted in 11/122 (9%); 9/11 (82%) had mTICI 2B-3 reperfusion compared to 48/111 (43%) mTICI 2B-3 reperfusion in those with PCOMM unchanged (p=0.03). PCOMM flow (n=85) was associated with worse ASITN/SIR collaterals (median 2, IQR 2-3) than those without (n=29; median 3, IQR 2-3), p=0.09. PCOMM patency before treatment had 90-day mRS median of 4 (2-6) versus 3 (1-4), p=0.37. Conclusions: PCOMM flow diversion is common in MCA stroke, revealing an inverse correlation with leptomeningeal collaterals and dynamic changes following reperfusion.

Abstract WMP15: Hyperperfusion on Arterial Spin Labeling: Objective Decision Support Using Pattern Recognition

Background: Hyperperfusion detected on arterial spin labeling (ASL) images acquired after stroke onset has been shown to correlate with subsequent hemorrhagic transformation (HT). Presence of hyperperfusion is typically detected by visual review of arterial spin labeling cerebral blood flow (CBF). Such a review is subjective as it is challenged by inter-reader variability, noise, and lack of standard threshold. We present in this study a quantitative hyperperfusion detection model that can provide an objective decision support for the interpretation of ASL CBF maps and rapidly delineate hyperperfusion regions. Methods: ASL Cerebral blood flow (CBF) maps of acute stroke patients presenting with an occlusion in the MCA territory were coregistered to a standardized atlas space. To achieve reliable detection of ASL hyperperfusion, we formalize the problem as a nonlinear classification that relates regional voxel intensity values to the corresponding binary label (normal or hyperperfused). Our method takes into account the healthy contralateral hemisphere and its CBF intensity values during the determination of hyperperfusion of a voxel. Each input feature vector combines the regional intensity values at the voxel of interest, its contralateral matched region, and the distribution of the difference between them. Each input vector is associated to a label corresponding to the presence of hyperperfusion that was manually established by consensus between experts. The predicted hyperperfusion regions were compared to a groundtruth that manually established by two researchers. Results: A total of 361 ASL scans were collected from 221 patients (age=72±17 years; 45% males). Hyperperfusion was detected in 76 patients that were subsequently used in our analysis. An AUC of 83±5% was reached after a leave-one-out cross-validation, which corresponds to the accuracy in detecting hyperperfusion compared to manual delineation of hyperperfusion on ASL CBF maps. Conclusion: Pattern recognition based on a nonlinear regression can provide an accurate and objective measure of hyperperfusion on ASL CBF images and could therefore improve the detection of hemorrhagic transformation in acute stroke patients.

Assessment of cranial blood flow in cervical spondylosis patients

Background: The effect of rotation of head movement on cerebral artery blood flow in normal subjects has been widely studied. Many factors effect blood flow through the vertebral artery such as rotation of head, variably sized arteries, atheroma, tortuous vertebral arteries, carotid sinus compression etc. Objective: To determine the effect of head and neck movement on the cranial blood flow in cervical spodylosis patients with reticulopathy. Material and methods: Fifty participants (23 male, 27female) with informed consent (20-70 years) participated in this study. Subjects with severe hypertension, cardiovascular, liver, kidney or other life threatening diseases were excluded. The changes in the Anterior, Middle, and Posterior cerebral arteries blood flow between the neutral (face to front) and rotated head positions (flexion and extension) was measured with Trans-cranial Doppler Method in healthy and Cervical Spondylosis with reticulopathy patients. Results: No significant differences in the afferent cerebral blood flow of the neutral and of the changed head positions in cervical spondylosis patient was found. In Cervical Spodylosis patients with reticulopathy, the mean values of cerebral blood flow were insignificantly different as compared to neutral position, however according to the data collected till now, the lowest blood inflow level was recorded during extension of the head. Flow changes were less than 10% considered to be normal. Conclusion: The flow changes in the afferent cerebral arteries of healthy subjects were insignificant. When a person has cervical spondylosis with reticulopathy, flexion and extension of head may diminish blood flow through the vertebral artery in its course through the cervical spine. Further studies and data are required to establish association. Keywords: Cervical spondylosis, Cranial blood flow, TCD

対側浅側頭動脈からの側副血行を有する総頸動脈閉塞に対するバイパス術前後の血行動態の評価に浅側頭動脈超音波検査が有用であった一例

A 77-year-old man with a history of radiation therapy for pharyngeal cancer and consequent asymptomatic left common carotid artery (CCA) occlusion showed asymptomatic ischemic stroke and left transient monocular blindness, and he was admitted to our hospital. He was found to have an indication for bypass surgery because of a remarkable reduction in cerebral blood flow in the ipsilateral middle cerebral artery (MCA) territory. Carotid ultrasonography revealed retrograde blood flow of the ipsilateral external carotid artery (ECA) and a U-turn phenomenon to the internal carotid artery (ICA). Cerebral angiography demonstrated spontaneous bonnet bypass flow from the right superficial temporal artery (STA) to the left STA, but the blood flow via the bypass was not enough to supply the left MCA. Bypass surgery to anastomose the bonnet bypass to the left MCA was performed, and postsurgical cerebral blood flow to the ipsilateral MCA territory improved. On STA duplex ultrasonography (STDU), the pulsatility index value of the contralateral STA changed from an ECA pattern before surgery to an ICA pattern after. Moreover, postsurgical mean flow velocity of the bonnet bypass to the left MCA was relatively higher than the presurgical retrograde mean flow velocity of the left STA. These ultrasonographic findings correlated with those on single photon emission computed tomography (SPECT) and cerebral angiography. As demonstrated in the present case, ultrasonography including STDU is useful in the evaluation of cerebral hemodynamics before and after cerebral artery bypass surgery and in the usual STA-MCA anastomosis.

Effects of a Dietary Beetroot Juice Treatment on Systemic and Cerebral Haemodynamics- A Pilot Study.

Beetroot Juice (BJ) contains dietary nitrates that increase the blood Nitric Oxide (NO) level, decrease Blood Pressure (BP), increase athletic performance and improve cognitive functions but the mechanism remains unclear. Ultrasonographic measurement of middle cerebral artery blood flow velocity with computation of Cerebral Augmentation Index (CAIx) is a measure of the reflected flow signal, modulated by changes in cerebrovascular resistance and compliance. This pilot study tests the hypothesis that ingestion of an amount of BJ sufficient to raise the blood NO level two-to three-fold, decreases Transcranial Doppler (TCD) measured CAIx. Ten healthy young-adult African-American women were studied at two levels of submaximal exercise, 40% and 80% of their predetermined peak oxygen consumptions. The subjects ingested nitrate-free orange juice (OJ, control) and an isocaloric BJ beverage (1.5 mg/mL nitrate, 220 Cal), on different days, 1-2 weeks apart. The BJ treatment increased blood NO and decreased systolic BP at rest and at the two levels of exercise. The BJ treatment decreased CAIx only at the two levels of exercise (from 79 ± 2% to 62 ± 2% and from 80 ± 2% to 60 ± 3%, p<0.05). Exercise increased TCD-measured resistance and pulsatility indices (RIx, PIx) without changing AIx. The BJ treatment had no effect on RIx and PIx. These findings suggest that decreased CAIx associated with aerobic exercise reflects the change in cerebral haemodynamics resulting from dietary nitrate supplementation. Future studies should determine whether the BJ-induced decrement in CAIx is correlated with an improvement in brain function.

Effect of Single Intravitreal Bevacizumab on Ophthalmic and Middle Cerebral Arterial Blood Flow in Retinopathy of Prematurity

Purpose: To evaluate the effect of a single intravitreal bevacizumab (IVB) injection on blood flow parameters in the ophthalmic artery (OA) and middle cerebral artery (MCA) in infants with retinopathy of prematurity (ROP). Materials and Methods: This prospective and interventional study included 15 infants with ROP who were treated with IVB. Peak systolic velocity (PSV), end-diastolic velocity, mean velocity (MV) and resistivity index were measured using pulse wave Doppler ultrasonography (Philips En Visor C, Amsterdam, The Netherlands) in the OA and MCA, before IVB injection and 1 day, 1 week and 1 month after IVB injection. Results: Measurements of PSV-OA, MV-OA and PSV-MCA showed significant changes after IVB treatment (p = 0.01, p = 0.02, p = 0.02, respectively). The PSV-OA measurements at 1 week and 1 month were significantly lower than the baseline PSV-OA measurement (p = 0.03 and p = 0.01, respectively). The MV-OA measurement was significantly lower at 1 month following IVB as compared to the baseline MV-OA measurement (p = 0.03). The PSV-MCA showed a significant decline 1 day after IVB injection (p = 0.03). Conclusions: The study demonstrated that IVB causes significant alterations in blood flow parameters in the OA and MCA predicted by Doppler ultrasonography in infants with ROP.

Cerebrovascular, cardiovascular and strength responses to acute ammonia inhalation.

Ammonia is used as a stimulant in strength based sports to increase arousal and offset fatigue however little is known about its physiological and performance effects. The purpose of this study was twofold (1) establish the physiological response to acute ammonia inhalation (2) determine whether the timing of the physiological response corresponds with a performance enhancement, if any. Fifteen healthy males completed two trials. Trial one investigated the beat-to-beat middle cerebral artery blood flow velocity (MCAv), heart rate (HR) and mean arterial pressure (MAP) response to ammonia inhalation. During trial two, participants performed a maximal single mid-thigh pull (MTP) at various time points following ammonia inhalation in a randomised order: MTPs were conducted immediately, 15, 30 and 60s following ammonia inhalation. A MTP with no ammonia inhalation served as the control. During this trial maximal MTP force, rate of force development (RFD) and electromyography (EMG) activity were recorded. MCAvmean increased and peaked on average by 6cms(-1) (P<0.001), 9.4±5.5s following ammonia inhalation. Similarly, HR was increased by 6±11 beats per minute 15s following ammonia inhalation (P<0.001). MAP remained unchanged following inhalation (P=0.51). The use and timing of ammonia inhalation had no effect on maximal force, RFD or EMG (all P>0.2) compared to control. MCAv was elevated despite no increase in MAP occurring; this is indicative of a cerebrovascular vasodilation. Despite the marked cerebrovascular and cardiovascular response to ammonia inhalation no ergogenic effect was observed during the MTP, irrespective of the timing of administration.

Automatic labeling of cerebral arteries in magnetic resonance angiography.

In order to introduce 4D flow magnetic resonance imaging (MRI) as a standard clinical instrument for studying the cerebrovascular system, new and faster postprocessing tools are necessary. The objective of this study was to construct and evaluate a method for automatic identification of individual cerebral arteries in a 4D flow MRI angiogram. Forty-six elderly individuals were investigated with 4D flow MRI. Fourteen main cerebral arteries were manually labeled and used to create a probabilistic atlas. An automatic atlas-based artery identification method (AAIM) was developed based on vascular-branch extraction and the atlas was used for identification. The method was evaluated by comparing automatic with manual identification in 4D flow MRI angiograms from 67 additional elderly individuals. Overall accuracy was 93%, and internal carotid artery and middle cerebral artery labeling was 100% accurate. Smaller and more distal arteries had lower accuracy; for posterior communicating arteries and vertebral arteries, accuracy was 70 and 89%, respectively. The AAIM enabled fast and fully automatic labeling of the main cerebral arteries. AAIM functionality provides the basis for creating an automatic and powerful method to analyze arterial cerebral blood flow in clinical routine.

Clinical features and endovascular treatment of anterior temporal artery aneurysms

Objective To investigate the clinical features, mechanism and endovascular treatment of anterior temporal artery aneurysm of the posterior cerebral artery. Methods The clinical data of 6 patients with anterior temporal artery aneurysm treated with endovascular treatment at the Cerebral Vascular Interventional Treatment Center, Henan Provincial People's Hospital, Zhengzhou University from January 2010 to December 2014 were analyzed retrospectively. All 6 patients were accompanied by ipsilateral middle cerebral artery or internal carotid artery occlusion. The diameter of aneurysm was 2.5 to 5.0 mm, 2 of them had subarachnoid hemorrhage, 1 did not have any symptom, and 3 were accompanied by anterior circulation cerebral ischemic symptom.Six patients were treated by endovascular management, 4 cases of unruptured aneurysms were treated by coil embolization and retain its parent artery; 2 case of subarachnoid hemorrhage aneurysm and it's parent artery were embolized by coil or Glubran 2. Aneurysm embolization density, parent artery blood flow and posterior cerebral artery blood flow were observed by postoperative DSA imaging.Patients were followed up for 3 months to 1 year. Results The immediate angiography after procedure showed that 4 patients with unruptured aneurysm were embolized densely. The parent arteries of 2 cases were patent, 1 had blood flow retardation, and 1 thrombosis caused parent artery occlusion. No new infarction foci were found after procedure. Four patients were followed up by telephone, and they did not have relevant clinical symptoms. Three patients were followed up with imaging. Their aneurysms were embolized densely without recurrence. The parent artery was patent in 1 case. The blood flow of parent artery was slightly slow in 1 case and 1 had arterial occlusion at 3 months. One patient with subarachnoid hemorrhage died of pulmonary complications after procedure, and the remaining 5 patients recovered well during the follow-up. Conclusions Anterior temporal artery aneurysm is a special type of posterior cerebral artery aneurysm. The causes of aneurysm are significantly correlated with hemodynamics. It is easy to confuse it with posterior cerebral artery trunk aneurysm and superior cerebellar artery aneurysm. Endovascular treatment is its safe and effective therapeutic approach. Key words: Intracranial aneurysm; Anterior temporal artery; Endovascular treatment

“Float first and kick for your life”: Psychophysiological basis for safety behaviour on accidental short-term cold water immersion

IntroductionAccidental cold-water immersion (CWI) evokes the life threatening cold shock response (CSR) which increases the risk of drowning. Consequently, the safety behaviour selected is critical in determining survival; the present advice is to ‘float first’ and remain stationary (i.e. rest). We examined whether leg only exercise (i.e., treading water; ‘CWI-Kick’) immediately on CWI could reduce the symptoms of the CSR, offset the reduction in cerebral blood flow that is known to occur and reduce the CSR's symptoms of breathlessness. We also examined whether perceptual responses instinctive to accidental CWI were exacerbated by this alternative behaviour. We contrasted CWI-Kick to a ‘CWI-Rest’ condition and a thermoneutral control (35°C); ‘TN-Rest’. MethodSeventeen participants were tested (9 males, 8 females). All immersions were standardised; water temperature in cold conditions (i.e., 12°C) was matched ±/0.5°C within participant. Middle cerebral artery blood flow velocity (MCAv) and cardiorespiratory responses were measured along with thermal perception (sensation and comfort) and dyspnoea. Data were analysed using repeated measures ANOVA (alpha level of 0.05). ResultsMCAv was significantly reduced in CWI-Rest (−6 (9)%; 1st minute of immersion) but was offset by leg only exercise immediately on cold water entry; CWI-Kick MCAv was never different to TN-Rest (−3 (16)% cf. 5 (4)%). All CWI cardiorespiratory and perceptual responses were different to TN-Rest but were not exacerbated by leg only exercise. DiscussionTreading water may aid survival by offsetting the reduction in brain blood flow velocity without changing the instinctive behavioural response (i.e. perceptions). “Float first — and kick for your life” would be a suitable amendment to the water safety advice.

Complex Alterations of Intracranial 4-Dimensional Hemodynamics in Vein of Galen Aneurysmal Malformations During Staged Endovascular Embolization.

Vein of Galen aneurysmal malformations (VGAMs) are rare congenital cerebral arteriovenous shunts often treated by staged endovascular embolization early in life. Treatment-induced changes in intracranial hemodynamics and their impact on the clinical management of VGAM patients remain unclear. To evaluate hemodynamic alterations in the cerebral arterial and venous network in pediatric patients with VGAMs during staged embolizations. Serial 4-dimensional flow magnetic resonance imaging (21 scans) was performed in 6 VGAM patients (3 female; mean age, 2.1 ± 4.0 years) undergoing staged embolization. Time-integrated pathlines were used to visualize 3-dimensional blood flow changes in intracranial arterial and venous systems. Total cerebral arterial inflow (flow in bilateral internal carotid arteries plus basilar artery), arteriovenous shunt flow, and blood flow in other major cerebral arteries (middle cerebral artery; posterior cerebral artery) were quantified for all patients. Intracranial 3-dimensional blood flow visualization demonstrated marked reduction of arteriovenous shunting and distinct hemodynamic alterations after embolization. From baseline to endpoint embolization, total cerebral arterial inflow dropped by 40.2% (from 22.70 ± 6.54 mL/s to 13.57 ± 4.87 mL/s), corresponding to arteriovenous shunt flow reduction of 73.5% (from 9.69 ± 6.16 mL/s to 2.57 ± 3.79 mL/s). In addition, the ipsilateral posterior cerebral artery/middle cerebral artery flow ratio decreased by 86.9% (from 4.20 ± 6.28 to 0.55 ± 0.23). Hemodynamic alterations in VGAMs after embolization can be visualized and quantified using 4-dimensional flow magnetic resonance imaging. Cerebral arterial inflow and arteriovenous shunt flow reduction and complex flow redistribution after embolization illustrate the potential of 4-dimensional flow magnetic resonance imaging to better evaluate the efficacy of interventions and monitor treatment effects.

Mild dehydration modifies the cerebrovascular response to the cold pressor test.

The cold pressor test (CPT) is widely used in clinical practice and physiological research. It is characterized by a robust autonomic response, with associated increases in heart rate (HR), mean arterial pressure (MAP) and mean middle cerebral artery blood flow velocity (MCAv(mean)). Hydration status is not commonly reported when conducting this test, yet blood viscosity alone can modulate MCAv(mean), potentially modifying the MCAv(mean) response to the CPT. We investigated the effect of mild dehydration on the physiological response to the CPT in 10 healthy men (mean ± SD: age 28 ± 5 years; body mass 83 ± 5 kg). All participants completed two CPTs, cold water (0°C) immersion of both feet for 90 s, with the order of the euhydration and dehydration trials counterbalanced. Beat-to-beat MCAv, MAP, HR and breath-by-breath partial pressure of end-tidal CO2 (P(ET,CO2)) were measured continuously. Participants' pain perception was measured 1 min into the CPT using a visual analog scale (no pain = 0; maximal pain = 10). Dehydration significantly elevated plasma osmolality and urine specific gravity and reduced body mass (all P < 0.01). The MAP and HR responses were not different between treatments (both P > 0.05). After 90 s of immersion, the change in MCAv(mean) from baseline was less in the dehydration compared with the euhydration trial (change 0 ± 5 versus 7 ± 7 cm s(-1), P = 0.01), as was P(ET,CO2) (change -3 ± 2 versus 0 ± 3 mmHg, P = 0.02). Dehydration was associated with greater relative pain sensation during the CPT (7.0 ± 1.3 vs 5.8 ± 1.8, P = 0.02). Our results demonstrate that mild dehydration can modify the cerebrovascular response to the CPT, with dehydration increasing perceived pain, lowering P ET ,CO2 and, ultimately, blunting the MCAv(mean) response.

Orthostatic cerebral blood flow and symptoms in patients with familial dysautonomia

Patients with familial dysautonomia (FD) have afferent baroreflex failure and often experience extremely low blood pressure when upright, but rarely complain of symptoms of hypoperfusion. This suggests that patients either fail to recognize cerebral ischemia or have a better than normal cerebrovascular auto-regulatory capacity. Our aim was to examine the relationship between blood pressure, cerebral blood flow, and orthostatic symptoms in FD patients. We measured continuous blood pressure, RR intervals, end-tidal carbon dioxide and middle cerebral artery blood flow velocity (transcranial Doppler) supine, sitting, and standing in eleven patients with FD (age 27 ± 2 years, 5 males) and seven age-matched controls. Subjects were asked to report the presence or absence of symptoms at one-minute intervals. In patients with FD, systolic blood pressure fell significantly from 137 ± 8 mmHg to 105 ± 9 mmHg after 3 minutes of standing (p < 0.006, range 55 to 149 mmHg). Despite the fall in blood pressure none of the patients reported symptoms of orthostatic hypotension. Changes in cerebral blood flow were minimal (mean Δ-6 ± 3%), and not statistically different to controls (Δ-3 ± 2%, p = 0.39), which maintained their blood pressure well on standing. The results show that patients with FD have an excellent auto-regulatory capacity and maintain cerebral blood flow within the normal range despite severe hypotension. This study highlights the usefulness of cerebral blood flow recordings to understand the relationship between symptoms and blood pressure in patients with abnormal baroreflex function.

Dynamic Cerebral Autoregulation after Cardiopulmonary Bypass.

Background Cerebral hemodynamic disturbances in the peri- or postoperative period may contribute to postoperative cognitive dysfunction (POCD) in patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB). We therefore examined dynamic cerebral autoregulation (dCA) post-CPB and changes in neurocognitive function in patients that had undergone CABG. Materials and Methods We assessed dCA by transfer function analysis of spontaneous oscillations between arterial blood pressure and middle cerebral artery blood flow velocity measured by transcranial Doppler ultrasound in eight patients 6 hours after the cessation of CPB; 10 healthy volunteers served as controls. Neurocognitive function was assessed by four specific tests 1 day prior to and 3 days after CPB. Results Even though patients exhibited systemic inflammation and anemic hypoxemia, dCA was similar to healthy volunteers (gain: 1.24 [0.94-1.49] vs. 1.22 [1.06-1.34] cm mm Hg-1 s-1, p = 0.97; phase: 0.33 [0.15-0.56] vs. 0.69 [0.50-0.77] rad, p = 0.09). Neurocognitive testing showed a perioperative decline in the Letter Digit Coding Score (p = 0.04), while weaker dCA was associated with a lower Stroop Color Word Test (rho = - 0.90; p = 0.01). Discussion and Conclusion We found no changes in dCA 6 hours after CPB. However, based on the data at hand, it cannot be ruled out that changes in dCA predispose to POCD, which calls for larger studies that assess the potential impact of dCA in the early postoperative period on POCD.

Effect of acute nitrate supplementation on neurovascular coupling and cognitive performance in hypoxia.

The matching of oxygen supply to neural demand (i.e., neurovascular coupling (NVC)) is an important determinant of cognitive performance. The impact of hypoxia on NVC remains poorly characterized. NVC is partially modulated by nitric oxide (NO), which may initially decrease in hypoxia. This study investigated the effect of acute NO-donor (nitrate) supplementation on NVC and cognitive function in hypoxia. Twenty healthy men participated in this randomized, double-blind, crossover design study. Following normoxic cognitive/NVC testing, participants consumed either nitrate (NIT) or a NIT-depleted placebo (PLA). Participants then underwent 120 min of hypoxia (11.6% ± 0.1% O2) and all cognitive/NVC testing was repeated. NVC was assessed as change in middle cerebral artery (MCA) blood flow during a cognitive task (incongruent Stroop) using transcranial Doppler. Additional computerized cognitive testing was conducted separately to assess memory, executive function, attention, sensorimotor, and social cognition domains. Salivary nitrite significantly increased following supplementation in hypoxia for NIT (+2.6 ± 1.0 arbitrary units (AU)) compared with PLA (+0.2 ± 0.3 AU; p < 0.05). Memory performance (-6 ± 13 correct) significantly decreased (p < 0.05) in hypoxia while all other cognitive domains were unchanged in hypoxia for both PLA and NIT conditions (p > 0.05). MCA flow increased during Stroop similarly in normoxia (PLA +5 ± 6 cm·s(-1), NIT +7 ± 7 cm·s(-1)) and hypoxia (PLA +5 ± 9 cm·s(-1), NIT +6 ± 7 cm·s(-1)) (p < 0.05) and this increase was not altered by PLA or NIT (p > 0.05). In conclusion, acute hypoxia resulted in significant reductions in memory concomitant with preservation of executive function, attention, and sensorimotor function. Hypoxia had no effect on NVC. Acute NIT supplementation had no effect on NVC or cognitive performance in hypoxia.

IMPACT OF DIABETES ON CAROTID ARTERY REVASCULARIZATION: A SYSTEMATIC REVIEW AND META-ANALYSIS

s S53 r1⁄40.83, p<0.001 and CA: r1⁄40.46, p1⁄40.03), whereas IMT was directly associated with RI in SA only (SA: r1⁄40.81, p<0.001 vs. CA: r1⁄4-0.07, p1⁄40.76). Multivariate linear regression model revealed significant interaction between ethnic group and IMT when predicting PI (b1⁄4 0.92 (95%CI: 0.24, 1.60), p1⁄40.009; adjusted r1⁄4 0.451). CONCLUSION: Markedly stronger relationships between structural changes of central arteries and pulsatile blood flow in cerebral arteries were observed in SA older adults. Increasing evidence of an association between IMT and pulsatile cerebral hemodynamics might be related to stroke risk. The majority of existing evidence comes from predominantly CA cohorts, however, limiting the generalizability to at-risk ethnic populations. Our findings merit further prospective investigation into the association of IMT and cerebrovascular hemodynamic properties in disease risk among SA. Such measurements could allow for early detection of disease processes and further aid in understanding the increased risk of cardioand cerebrovascular diseases in the SA population. Canadian Institutes of Health Research 107 PLAQUE ECHODENSITY AND TEXTURAL FEATURES ARE ASSOCIATED WITH CAROTID PLAQUE INSTABILITY RJ Doonan, J Gorgui, JP Veinot, C Lai, E Kyriacou, MM Corriveau, OK Steinmetz, KS Mackenzie, DI Obrand, SS Daskalopoulou

Ratio between carotid artery stiffness and cerebral blood flow - a new ultrasound index for ischemic leukoaraiosis

Ratio between carotid artery stiffness and cerebral blood flow - a new ultrasound index for ischemic leukoaraiosis

Are fetuses that fail to achieve their growth potential at increased risk of intrapartum compromise?

The true growth potential of a fetus is difficult to predict but recently a new definition, independent of fetal weight, using cerebroplacental (cerebro-umbilical) ratio (CPR) < 0.6765 multiples of the median (MoM), was reported. We applied this definition to a cohort of low-risk pregnancies recruited prospectively to determine if fetuses with CPR < 0.6765 are at increased risk of developing signs of intrapartum fetal compromise. Recruitment to this prospective observational study took place between March 2011 and March 2014. All women with low-risk singleton pregnancies at term were eligible. Women with known or suspected placental dysfunction were excluded, as were women with fetuses with an estimated fetal weight < 10(th) centile. All participants underwent ultrasound examination prior to active labor (≤ 4 cm cervical dilatation), during which fetal biometry as well as umbilical artery and fetal middle cerebral artery blood flow were assessed. Following delivery, intrapartum and neonatal outcomes were compared between fetuses that had a CPR < 0.6765 MoM and those that had a CPR ≥ 0.6765 MoM. In total, 775 women were recruited. Fetuses with CPR < 0.6765 MoM were significantly more likely to require Cesarean delivery because of presumed fetal compromise (P < 0.001). These fetuses were also at increased risk of compromise at any time during labor and were less likely to be delivered vaginally, spontaneously or otherwise, than were those with CPR ≥ 0.6765 MoM. CPR < 0.6765 MoM gave a positive predictive value (PPV) for Cesarean delivery because of presumed fetal compromise of 36.7% and a negative predictive value of 88.7%, with a sensitivity of 18% and a specificity of 95.4%. Fetuses that failed to achieve their growth potential (defined as CPR < 0.6765 MoM) were at increased risk of intrapartum compromise and were less likely to be delivered vaginally. However, a low negative predictive value was observed for fetal compromise and further studies are required to support the translation of this technique into clinical practice.

Non-Linear Characterisation of Cerebral Pressure-Flow Dynamics in Humans.

Cerebral metabolism is critically dependent on the regulation of cerebral blood flow (CBF), so it would be expected that vascular mechanisms that play a critical role in CBF regulation would be tightly conserved across individuals. However, the relationships between blood pressure (BP) and cerebral blood velocity fluctuations exhibit inter-individual variations consistent with heterogeneity in the integrity of CBF regulating systems. Here we sought to determine the nature and consistency of dynamic cerebral autoregulation (dCA) during the application of oscillatory lower body negative pressure (OLBNP). In 18 volunteers we recorded BP and middle cerebral artery blood flow velocity (MCAv) and examined the relationships between BP and MCAv fluctuations during 0.03, 0.05 and 0.07Hz OLBNP. dCA was characterised using project pursuit regression (PPR) and locally weighted scatterplot smoother (LOWESS) plots. Additionally, we proposed a piecewise regression method to statistically determine the presence of a dCA curve, which was defined as the presence of a restricted autoregulatory plateau shouldered by pressure-passive regions. Results show that LOWESS has similar explanatory power to that of PPR. However, we observed heterogeneous patterns of dynamic BP-MCAv relations with few individuals demonstrating clear evidence of a dCA central plateau. Thus, although BP explains a significant proportion of variance, dCA does not manifest as any single characteristic BP-MCAv function.