Middle Cerebral Artery Velocity Research Articles

Whole blood viscosity and cerebral blood flow velocities in obese hypertensive or obese normotensive adolescents.

Obesity affects all major organ systems and leads to increased morbidity and mortality. Whole blood viscosity is an important independent regulator of cerebral blood flow. The aim of the present study was to evaluate the effect of whole blood viscosity on cerebral artery blood flow velocities using transcranial Doppler ultrasound in pediatric patients with obesity compared to healthy controls and analyze the effect of whole blood viscosity and blood pressure status to the cerebral artery blood flow velocities. Sixty patients with obesity diagnosed according to their body mass index (BMI) percentiles aged 13-18 years old were prospectively enrolled. They were grouped as hypertensive or normotensive according to their ambulatory blood pressure monitoring. Whole blood viscosity and middle cerebral artery velocities by transcranial Doppler ultrasound were studied and compared to 20 healthy same aged controls. Whole blood viscosity values in hypertensive (0.0619±0.0077 poise) and normotensive (0.0607±0.0071 poise) groups were higher than controls (0.0616±0.0064 poise), with no significance. Middle cerebral artery blood flow velocities were higher in the obese hypertensive (73.9±15.0 cm/s) and obese normotensive groups (75.2±13.5 cm/s) than controls (66.4±11.5 cm/s), but with no statistical significance. Physiological changes in blood viscosity and changes in blood pressure did not seem to have any direct effect on cerebral blood flow velocities, the reason might be that the cerebral circulation is capable of adaptively modulating itself to changes to maintain a uniform cerebral blood flow.

Relationship between Aortic Compliance and Impact of Cerebral Blood Flow Fluctuation to Dynamic Orthostatic Challenge in Endurance Athletes.

Aorta effectively buffers cardiac pulsatile fluctuation generated from the left ventricular (LV) which could be a mechanical force to high blood flow and low-resistance end-organs such as the brain. A dynamic orthostatic challenge may evoke substantial cardiac pulsatile fluctuation via the transient increases in venous return and stroke volume (SV). Particularly, this response may be greater in endurance-trained athletes (ET) who exhibit LV eccentric remodeling. The aim of this study was to determine the contribution of aortic compliance to the response of cerebral blood flow fluctuation to dynamic orthostatic challenge in ET and age-matched sedentary (SED) young healthy men. ET (n = 10) and SED (n = 10) underwent lower body negative pressure (LBNP) (−30 mmHg for 4 min) stimulation and release the pressure that initiates a rapid regain of limited venous return and consequent increase in SV. The recovery responses of central and middle cerebral arterial (MCA) hemodynamics from the release of LBNP (~15 s) were evaluated. SV (via Modeflow method) and pulsatile and systolic MCA (via transcranial Doppler) normalized by mean MCA velocity (MCAv) significantly increased after the cessation of LBNP in both groups. ET exhibited the higher ratio of SV to aortic pulse pressure (SV/AoPP), an index of aortic compliance, at the baseline compared with SED (P < 0.01). Following the LBNP release, SV was significantly increased in SED by 14 ± 7% (mean ± SD) and more in ET by 30 ± 15%; nevertheless, normalized pulsatile, systolic, and diastolic MCAv remained constant in both groups. These results might be attributed to the concomitant with the increase in aortic compliance assessed by SV/AoPP. Importantly, the increase in SV/AoPP following the LBNP release was greater in ET than in SED (P < 0.01), and significantly correlated with the baseline SV/AoPP (r = 0.636, P < 0.01). These results suggest that the aortic compliance in the endurance athletes is able to accommodate the additional SV and buffer the potential increase in pulsatility at end-organs such as the brain.

Anesthetic Considerations for Carotid Endarterectomy: A Postgraduate Educational Review.

Carotid endarterectomy (CEA) has shown a significant benefit in preventing ipsilateral stroke when it is compared to conservative management. Surgical morbidity and mortality must be kept to a minimum to achieve this benefit. Neurological status of the CEA patients can be monitored easily during regional anesthesia depending on the awake testing (neurocognitive assessment) method of the CEA patients. In addition, specific parameters can help us to monitor and to predict the neurological status of the CEA patients during the procedures such as regional cerebral oxygen saturation (rSO2) and middle cerebral artery velocity (MCAv) changes. We conducted a computerized literature search involving humans, published in English until December 2017, and indexed through Medical Databases; MEDLINE/PubMed, EMBASE, and Web of Science. We reviewed articles performed for prospective and other types of studies related to CEA procedures and techniques which can predict patient's status during the procedure. Searching relevant articles and discussing the results to allow meaningful rate comparison, and to conclude a result view which benefits the CEA patients and the medical staff during the CEA procedures. In total, studies observed cerebral rSO2 and MCAv have significant value during CEA procedures. Patients with neurological symptoms during the procedures showed changes of cerebral rSO2 and MCAv more than the patients without neurological symptoms. Mentioned parameters (cerebral rSO2 and MCAv) showed significant increasing right after the procedure. Mostly, CEA surgeries under local anesthesia were observed, for monitoring patients’ consciousness status and comparing it to patients who undergo general anesthesia, to view the reliability of these techniques during CEA procedures, and to predict and avoid intraoperative neurological symptoms.

Differential Systolic and Diastolic Regulation of the Cerebral Pressure-Flow Relationship During Squat-Stand Manoeuvres.

Cerebral pressure-flow dynamics are typically reported between mean arterial pressure and mean cerebral blood velocity. However, by reporting only mean responses, potential differential regulatory properties associated with systole and diastole may have been overlooked. Twenty young adults (16 male, age: 26.7 ± 6.6 years, BMI: 24.9 ± 3.0 kg/m2) were recruited for this study. Middle cerebral artery velocity was indexed via transcranial Doppler. Cerebral pressure-flow dynamics were assessed using transfer function analysis at both 0.05 and 0.10 Hz using squat-stand manoeuvres. This method provides robust and reliable measures for coherence (correlation index), phase (timing buffer) and gain (amplitude buffer) metrics. There were main effects for both cardiac cycle and frequency for phase and gain metrics (p < 0.001). The systolic phase (mean ± SD) was elevated at 0.05 (1.07 ± 0.51 radians) and 0.10 Hz (0.70 ± 0.46 radians) compared to the diastolic phase (0.05 Hz: 0.59 ± 0.14 radians; 0.10 Hz: 0.33 ± 0.11 radians). Conversely, the systolic normalized gain was reduced (0.05 Hz: 0.49 ± 0.12%/%; 0.10 Hz: 0.66 ± 0.20%/%) compared to the diastolic normalized gain (0.05 Hz: 1.46 ± 0.43%/%; 0.10 Hz: 1.97 ± 0.48%/%). These findings indicate there are differential systolic and diastolic aspects of the cerebral pressure-flow relationship. The oscillations associated with systole are extensively buffered within the cerebrovasculature, whereas diastolic oscillations are relatively unaltered. This indicates that the brain is adapted to protect itself against large increases in systolic blood pressure, likely as a mechanism to prevent cerebral haemorrhages.

Comparison of Resistance Index and Peak Systolic Velocity of Fetal Middle Cerebral Artery between Normal and Fetuses with Mutated Beta-Thalassemia Gene

Comparison of Resistance Index and Peak Systolic Velocity of Fetal Middle Cerebral Artery between Normal and Fetuses with Mutated Beta-Thalassemia Gene

Impact of correction of anemia in end-stage renal disease patients on cerebral circulation and cognitive functions.

End-stage renal disease (ESRD) patients have been associated with accelerated vascular disease of the cerebral circulation due to uremic toxins. Furthermore, anemia increases cerebral oxygen extraction fraction which impairs the cerebral vasodilatory capacity. We evaluated the effect of correction of anemia on cerebral blood flow by measuring the mean blood flow velocity, resistance index (RI), and pulsatility index (PI) in the middle cerebral artery (MCA) in relation to cognitive functions. We measured the mean blood flow velocity, RI, and PI in MCA of 120 ESRD patients when the hemoglobin (Hb) ranges between 8 and 10 g/dL and after correction of anemia to two Hb ranges between 10-11.5 g/dL and 11.5-12.5 g/dL in the same patients using transcranial Doppler (TCD) ultrasound in relation to cognitive functions assessment by Mini-Mental State Examination. We observed that there is a mild-to-moderate cognitive impairment in hemodialysis (HD) patients associated with anemia. With the improvement of anemia, the cognitive functions improved. There was an improvement of blood flow of MCA with improvement of Hb. The improvement was obvious at Stage 3 (Hb 11.5-≤12.5 g/dL) in comparison to Stage 2 (Hb 10-<11.5 g/dL) with P <0.001 at all. The optimal Hb for HD patients ranges from 11.5 to ≤12.5 g/dL which associated with better improvement of cognitive function and cerebral circulation investigated by TCD ultrasound for MCA.

The Effect of Maternal Mathematical Activities on the Fetal Brain

Background: In recent years, there has been growing interest in the effect of maternal exposure to physiological, environmental, and also psychological factors during gestation on child development. Several independent studies link maternal stress during pregnancy to emotional and behavioral problems in the child. Objectives: This study aimed to observe the effect of maternal cognitive activity on fetal brain blood flow to determine whether systematic maternal mathematical activity during pregnancy might influence child brain development. Method: Thirty-five women in the 28th to 40th week of pregnancy engaged in mathematical activities. Fetal middle cerebral artery (MCA), pulsatility index (PI) and peak systolic velocity (PSV) were monitored before, during, and after the activity. Results: Brain activity and blood flow were shown to be intimately linked. We observed a significant decrease in fetal brain MCA resistance, as evidenced by decreased MCA PI, towards the end of the mathematical activity. This may result in increased blood flow in the arteries supplying most brain regions and, possibly, increased brain activity. Conclusions: A correlation between the mother’s engagement in mathematical activities and fetal brain blood flow may lead to enhancement of the fetus’s brain function and a cognitive advantage for the child.

Chemoreflex function and brain blood flow during upright posture in men and women.

Orthostatic intolerance is more common in women than men, and some studies have found that women in the early follicular (EF) phase of the menstrual cycle experience the greatest feelings of lightheadedness. Chemoreflex function while supine or upright was investigated to determine the potential contribution of ventilatory control to these phenomena. Men (n = 13) and women (n = 14) were tested while supine and 70° upright (head‐up tilt [HUT]) and given: (1) normoxia or (2) hypercapnia (5% CO2). Women were tested during the EF phase (days 2–5) and the midluteal phase (ML; days 18–24). During HUT, all groups reduced cerebrovascular resistance index (men: 1.45 ± 0.08 to 1.42 ± 0.07 mmHg/(cm·sec), EF: 1.38 ± 0.11 to 1.26 ± 0.10 mmHg/(cm·sec), ML: 1.25 ± 0.07 to 1.09 ± 0.07 mmHg/(cm·sec); P ≤ 0.019); however, only men increased ventilation (men: 11.99 ± 0.65 to 13.24 ± 0.83 L/min; P < 0.01). In response to hypercapnia in the supine position, men had a smaller increase of diastolic middle cerebral artery velocity compared to women in the ML phase (men: +9.1 ± 2.0 cm/sec, ML: +15.7 ± 3.1 cm/sec, P = 0.039). During hypercapnia in HUT (compared to hypercapnia while supine), all groups had an augmented increase of ventilation (men: +7.46 ± 1.34 vs. +5.84 ± 1.09 L/min, EF: +6.71 ± 0.83 vs. +5.48 ± 0.66 L/min, ML: +7.99 ± 1.13 vs. +5.65 ± 0.81 L/min; P ≤ 0.028), suggesting that all groups experienced augmentation of the CO2 chemoreflex; however, only men had an augmented increase of mean arterial pressure (+0.10 ± 0.58 to +4.71 ± 0.87 mmHg; P ≤ 0.017). Our results indicate that men have different ventilatory responses to upright tilt compared to women, and that the CO2 chemoreflex response is enhanced in upright posture in both sexes. Furthermore, sexually dimorphic blood pressure responses to this chemoreflex enhancement are evident.

Paradigm Change? Cardiac Output Better Associates with Cerebral Perfusion than Blood Pressure in Ischemic Stroke.

In patients with acute ischemic stroke, penumbral perfusion is maintained by collateral flow and so far is maintained by normal mean arterial pressure (MAP) levels. Since MAP is dependent on cardiac function, optimization of cardiac output might be a valuable hemodynamic goal in order to optimize cerebral perfusion (CP). Cerebral perfusion was assessed by transcranial color-coded duplex and transcranial perfusion sonography in 10 patients with acute large hemispheric stroke. Time-to-peak (TTP) values of defined regions of interest (ROI) within the middle cerebral artery (MCA) territory were assessed bilaterally in addition to mean flow velocities of the MCA. Via semi-invasive advanced hemodynamic monitoring systemic hemodynamic parameters were assessed, including MAP and cardiac index (CI). Patients received sonographic follow-up after optimizing CI. TTP values of the deeply located ROIs of the non-affected as well as the affected hemisphere correlated highly significantly with CI (in affected side r = -0.827, p = 0.002; and in non-affected side r = -0.908, p < 0.0001). This demonstrates dependence of CP on CI, while correlation with MAP was not detected. Neither CI nor MAP revealed significant correlation with MCA velocity.

Serum Levels of S100b and NSE Proteins in Patients with Non-Transfusion-Dependent Thalassemia as Biomarkers of Brain Ischemia and Cerebral Vasculopathy.

Patients with non-transfusion-dependent thalassemia (NTDT) are at risk of developing brain ischemia. Transcranial Doppler (TCD) has been established as a useful screening tool of cerebrovascular disease in patients with sickle cell disease. Proteins neuron specific enolase (NSE) and S100B are biomarkers that reflect CNS injury. The purpose of this study is to evaluate cerebral vessel vasculopathy and brain damage in NTDT patients using non-invasive methods as TCD and measurement serum levels of NSE and S100B. We included in our study 30 patients with NTDT, aged between 8 and 62 years old (mean: 29.4, median: 32) who presented in our Unit for regular follow-up. We performed in all patients a non-imaging TCD examination and have measured serum S100, NSE and lactate dehydrogenase (LDH) levels. We investigated the possible correlation between TCD results and S100B, NSE and LDH levels as well as between NSE-LDH and S100B-LDH levels by regression analysis. We found a statistically significant relationship for both NSE, S100B with LDH. We also found a statistically significant relationship for S100B and time-averaged mean velocity (TAMV)/peak velocity of left middle cerebral artery (MCA), NSE and pulsatility index (PI)/resistive index (RI) of the left posterior cerebral artery (PCA). TCD results correlated with biomarkers for brain ischemia. This finding enhances the role of TCD as a screening tool for brain ischemia in patients with NTDT.

Cerebrovascular Hemodynamics During the Practice of Bhramari Pranayama, Kapalbhati and Bahir-Kumbhaka: An Exploratory Study.

Various pranayama techniques are known to produce different physiological effects. We evaluated the effect of three-different pranayama techniques on cerebrovascular hemodynamics. Eighteen healthy volunteers with the mean ± standard deviation age of 23.78 ± 2.96years were performed three-different pranayama techniques: (1) Bhramari, (2) Kapalbhati and (3) Bahir-Kumbhaka in three-different orders. Continuous transcranial Doppler (TCD) monitoring was performed before, during and after the pranayama techniques. TCD parameters such as peak systolic velocity, end diastolic velocity (EDV), mean flow velocity (MFV) and pulsatility index (PI) of right middle cerebral artery were recorded. Practice of Kapalbhati showed significant reductions in EDV and MFV with significant increase in PI while, Bahir-Kumbhaka showed significant increase in EDV and MFV with significant reduction in PI. However, no such significant changes were observed in Bhramari pranayama. Various types of pranayama techniques produce different cerebrovascular hemodynamic changes in healthy volunteers.

Post-prandial hyperlipidaemia results in systemic nitrosative stress and impaired cerebrovascular function in the aged.

Post-prandial hyperlipidaemia (PPH) acutely impairs systemic vascular endothelial function, potentially attributable to a free radical-mediated reduction in vascular nitric oxide (NO) bioavailability (oxidative-nitrosative stress). However, it remains to be determined whether this extends to the cerebrovasculature. To examine this, 38 (19 young (≤35 years) and 19 aged (≥60 years)) healthy males were recruited. Cerebrovascular function (middle cerebral artery velocity, MCAv) and cerebrovascular reactivity to hypercapnea (CVRCO2Hyper) and hypocapnea (CVRCO2Hypo) were determined via trans-cranial Doppler ultrasound and capnography. Venous blood samples were obtained for the assessment of triglycerides (photometry), glucose (photometry), insulin (radioimmunoassay), ascorbate free radical (A•-, electron paramagnetic resonance spectroscopy) and nitrite (NO2-, ozone-based chemiluminescence) in the fasted state prior to and 4 h following consumption of a standardized high-fat meal (1362 kcal; 130 g of fat). Circulating triglycerides, glucose and insulin increased in both groups following the high-fat meal (P<0.05), with triglycerides increasing by 1.37 ± 1.09 mmol/l in the young and 1.54 ± 1.00 mmol/l in the aged (P<0.05). This resulted in an increased systemic formation of free radicals in the young (P<0.05) but not the aged (P>0.05) and corresponding reduction in NO2- in both groups (P<0.05). While the meal had no effect on MCAv in either age group, CVRCO2Hyper was selectively impaired in the aged (P<0.05). These findings indicate that PPH causes acute cerebrovascular dysfunction in the aged subsequent to systemic nitrosative stress.

Cerebrovascular Reactivity and Vascular Activation in Postmenopausal Women With Histories of Preeclampsia.

Cerebrovascular reactivity (CVR) is reduced in patients with cognitive decline. Women with a history of preeclampsia are at increased risk for cognitive decline. This study examined an association between pregnancy history and CVR using a subgroup of 40 age- and parity-matched pairs of women having histories of preeclampsia (n=27) or normotensive pregnancy (n=29) and the association of activated blood elements with CVR. Middle cerebral artery velocity was measured by Doppler ultrasound before and during hypercapnia to assess CVR. Thirty-eight parameters of blood cellular elements, microvesicles, and cell-cell interactions measured in venous blood were assessed for association with CVR using principal component analysis. Middle cerebral artery velocity was lower in the preeclampsia compared with the normotensive group at baseline (63±4 versus 73±3 cm/s; P=0.047) and during hypercapnia (P=0.013-0.056). CVR was significantly lower in the preeclampsia compared with the normotensive group (2.1±1.3 versus 2.9±1.1 cm·s·mm Hg; P=0.009). Globally, the association of the 7 identified principal components with preeclampsia (P=0.107) and with baseline middle cerebral artery velocity (P=0.067) did not reach statistical significance. The interaction between pregnancy history and principal components with respect to CVR (P=0.084) was driven by a nominally significant interaction between preeclampsia and the individual principal component defined by blood elements, platelet aggregation, and interactions of platelets with monocytes and granulocytes (P=0.008). These results suggest that having a history of preeclampsia negatively affects the cerebral circulation years beyond the pregnancy and that this effect was associated with activated blood elements.

In-room assessment of intravascular velocity from time-resolved rotational angiography in patients with arteriovenous malformation: a pilot study

BackgroundTime-resolved rotational angiography (t-RA) enables interventionists to better comprehend complex arteriovenous malformations (AVMs), thereby facilitating endovascular treatment. However, its use in evaluating hemodynamic changes has rarely been explored.ObjectiveThis study uses...

COMPARATIVE CHARACTERISTICS OF CLASSICAL AND EVERSION ENDARTERECTOMY OF THE CAROTID ARTERIES

Purpose. The effectiveness of classical and eversion carotid endarterectomy (CE) in patients with cerebral ischemia in atherosclerotic stenosing carotid artery disease (ICA) was compared in the article.Material and methods. The examination and analysis of data of 122 patients with more than 60% ICA stenosis was held: men — n = 92 (60.1%), women n = 61 (39.9%). The average age was 52.3 years (ranged from 34 to 74 years). All the patients were symptomatic. 92 patients underwent an eversion endarterectomy (CE), 30 patients underwent classical CE.The effectiveness of surgical treatment was assessed by the dynamics of the neurological status, the change in the parameters of duplex and transcranial studies before the operation, on day 10, at 1, 3, 6, 9 months, 1, 1.5, 2, 3 years.Results. In patients who underwent eversion CE, in the early postoperative period, a significant decrease in the asymmetry coefficient was revealed in the study of background LSC valuesdue to an increase in the blood flow velocity in the ipsilateral middle cerebral artery (MCA) and a decrease in the linear velocity of the blood flow (LVBF) in the posterior cerebral artery (PCA) on the side of the initially stenotic ICA on the background of improvement of hemodynamic conditions in all cases (p &lt; 0.05). In patients, a significant increase in the reactivity factor for the hypercapnic load from the initial value was noted against the background of approaching the normative indices of the pulsation index. The latent period of vascular reactivity was shortened to 24.3 ± 3.7 seconds. In patients who underwent classical CEAE n = 30, in early terms of up to 1 month, a decrease in the coefficient of asymmetry of LVBF was noted due to the normalization of the velocity characteristics of cerebral blood flow in all the main cerebral vessels of the carotid and vertebrobasilar basins. Comparative analysis of the spectral expansion (SE) values obtained initially and recorded in groups with different types of surgical intervention revealed a significant difference in the resulting data (p &lt; 0.05). Restoration of SE parameters to normative ones was registered in the group of classical CEA in 26.7% (n = 8) and 79.3% (n = 73) with an eversion EAE for 1 month. The maximum rate of positive dynamics was traced during the first month after cerebral revascularization, complete recovery was recorded at the end of the 18th month in the group of eversion CE and 24 months in the group of classical CE. There were no significant differences in the resultant indices of regression of neurological disorders in the postoperative period of an eversion EAE and classical EAE (p &gt; 0.05).With the eversion CE, the total number of complications was n = 9 (9.8%), and 1 (1.1%) case — restenosis in the reconstruction zone. In the case of classical CE, the total number of complications was n = 10 (33.3%), of which n = 1 (3.3%) cases of hyperperfusion syndrome were observed; in n = 2 (6.6%) patients, development of a stroke, 1 (3.3%) developed myocardial infarction. Restenosis in the reconstruction zone was formed in n = 2 (6.6%) patients, peripheral nerve damage was in n = 4 (13.3%) patients.Conclusions. Classic and eversion CE are both effective. Short- and long-term clinical and hemodynamic results of surgical treatment by the method of eversion of the CE are somewhat better than the results of classical one.Classical CE is indicated in cases of extended plaque, eversion of the CE is indicated in the cases of short local plaques.

Post-carotid Endarterectomy Hypertension. Part 2: Association with Peri-operative Clinical, Anaesthetic, and Transcranial Doppler Derived Parameters

The first paper in this series observed that pre-operative baroreceptor dysfunction and poorly controlled hypertension were independently predictive for identifying patients who went on to require treatment for post-endarterectomy hypertension (PEH). The second paper examines the influence of intra-operative patient, transcranial Doppler (TCD) ultrasound, and anaesthetic variables on the incidence of PEH. In total, 106 patients underwent carotid endarterectomy (CEA) under general anaesthesia. Systolic blood pressure (SBP) changes, anaesthetic and vasoactive agents, analgesia, and post-operative pain scores, as well as TCD derived changes in middle cerebral artery (MCA) velocity during surgery were recorded. Patients who met pre-existing unit criteria for treating PEH after CEA (SBP>170mmHg without symptoms or SBP>160mmHg with headache/seizure/neurological deficit) were treated according to an established and validated protocol. In total, 40/106 patients (38%) required treatment for PEH following CEA (26 in theatre recovery [25%], 27 back on the vascular surgery ward [25%]), whereas seven (7%) had SBP surges>200mmHg on the ward. Patients requiring treatment for PEH had significantly higher pre-induction SBP (174±21mmHg vs. 153±21mmHg; p<.001), the greatest decreases in SBP after induction of anaesthesia (median decrease 100±32mmHg vs. 83±24mmHg; p=.01) and were significantly more likely to experience moderate/severe pain scores post-operatively (p=.003). Logistic regression analysis of the pre- and intra-operative data revealed that higher pre-induction mean SBP and lower pre-operative (impaired) BRS were the only independent predictors of PEH. This analysis of intra-operative variables has demonstrated that patients with poorly controlled and/or labile hypertension at induction of general anaesthesia were those at greatest risk of requiring treatment for PEH in the post-operative period after CEA. No other variables, including use of vasopressors, treatment of hypotension, anaesthetic agents, or changes in MCA velocity after clamp release and restoration of flow were able to predict who might go on to require treatment for PEH. Identification of at-risk individuals and aggressive blood pressure control in the post-operative period remains the mainstay of treatment.

EP14.24: Early and late fetal growth restriction: changes in fetal Doppler flow and correlation with pregnancy outcome in China

The aims are(1) insight into the changes in fetal Doppler flow of early FGR and late FGR respectively by ultrasound evaluation;(2) to explore ultrasound predictor associated with pregnancy outcome. FGR was divided into early FGR (<32 weeks) and late FGR (>32 weeks) based on the time of onset. A total of 55 early FGR and 57 late FGR were recruited in our study with the normal controls established respectively. Ultrasound evaluation included fetal growth, umbilical artery (UA), heart rate (HR), fetal cardiac function (myocardial performance index, MPI and stroke volume, SV), ductus venosus (DV) and middle cerebral artery (MCA). Table1 was shown Fetal Doppler flow changes for early FGR and late FGR respectively. Perinatal morbidity and mortality rate for early FGR was 23/55 (41.8%) but it was only 4/63 (6.3%) for late FGR (P value<0.05). UA PI (OR=92.757), a wave velocity of DV (OR=0.958) and diastolic blood flow velocity of MCA (OR=1.363) were associated with early FGR pregnancy outcome by logistic regression. However, there was no fetal Doppler parameter but estimated fetal weight (OR=0.996) by ultrasound had relationship with late FGR pregnancy outcome. Early FGR is associated with a series of alterations in fetal Doppler flow. So once it is diagnosed, UA PI, a wave velocity of DV and diastolic blood flow velocity of MCA should be monitored comprehensively by ultrasound Doppler in order to improve pregnancy outcome based on the higher perinatal morbidity and mortality rate. However, late FGR has slight change on fetal Doppler flow, which tends to be good prognosis. As late FGR, estimated fetal weight by ultrasound is more important for pregnancy outcome than Doppler monitoring. EP14.24: Table 1. Fetal Doppler flow changes for early FGR and late FGR(All of P value <0.05) MCA PI CPR(Cerebroplacental) MPI systolic blood flow velocity of MCA

Cognitive function during exercise under severe hypoxia

Acute exercise has been demonstrated to improve cognitive function. In contrast, severe hypoxia can impair cognitive function. Hence, cognitive function during exercise under severe hypoxia may be determined by the balance between the beneficial effects of exercise and the detrimental effects of severe hypoxia. However, the physiological factors that determine cognitive function during exercise under hypoxia remain unclear. Here, we examined the combined effects of acute exercise and severe hypoxia on cognitive function and identified physiological factors that determine cognitive function during exercise under severe hypoxia. The participants completed cognitive tasks at rest and during moderate exercise under either normoxic or severe hypoxic conditions. Peripheral oxygen saturation, cerebral oxygenation, and middle cerebral artery velocity were continuously monitored. Cerebral oxygen delivery was calculated as the product of estimated arterial oxygen content and cerebral blood flow. On average, cognitive performance improved during exercise under both normoxia and hypoxia, without sacrificing accuracy. However, under hypoxia, cognitive improvements were attenuated for individuals exhibiting a greater decrease in peripheral oxygen saturation. Cognitive performance was not associated with other physiological parameters. Taken together, the present results suggest that arterial desaturation attenuates cognitive improvements during exercise under hypoxia.

Cyclical blood flow restriction resistance exercise: a potential parallel to remote ischemic preconditioning?

Remote ischemic preconditioning (RIPC) is characterized by the cyclical application of limb blood flow restriction and reperfusion and has been shown to protect vital organs during a subsequent ischemic insult. Blood flow restriction exercise (BFRE) similarly combines bouts of blood flow restriction with low-intensity exercise and thus could potentially emulate the protection demonstrated by RIPC. One concern with BFRE, however, is the potential for an augmented rise in sympathetic outflow due to greater activation of the exercise pressor reflex. Because of the use of lower workloads, however, we hypothesized that BFRE would elicit an attenuated increase in sympathetic outflow [assessed via plasma norepinephrine (NE) and mean arterial pressure (MAP)] and middle cerebral artery velocity (MCAv) when compared with conventional exercise (CE). Fifteen subjects underwent two leg press exercise interventions: 1) BFRE-220 mmHg bilateral thigh occlusion at 20% 1 rep-max (1RM), and 2) CE-65% 1RM without occlusion. Each condition consisted of 4 × 5-min cycles of exercise, with 3 × 10-reps in each cycle. Five minutes of rest and reperfusion (for BFRE) followed each cycle. MAP increased with exercise (P < 0.001) and was 4-5 mmHg higher with CE versus BFRE (P ≤ 0.09). Mean MCAv also increased with exercise (P < 0.001) and was higher with CE compared with BFRE during the first bout of exercise only (P = 0.07). Plasma NE concentration increased with CE only (P < 0.001) and was higher than BFRE throughout exercise (P ≤ 0.02). The attenuated sympathetic response, combined with similar cerebrovascular responses, suggest that cyclical BFRE could be explored as an alternative to CE in the clinical setting.

Combining remote ischemic preconditioning and aerobic exercise: a novel adaptation of blood flow restriction exercise.

Remote ischemic preconditioning (RIPC) can attenuate tissue damage sustained by ischemia-reperfusion injury. Blood flow restriction exercise (BFRE) restricts blood flow to exercising muscles. We implemented a novel approach to BFRE with cyclical bouts of blood flow restriction-reperfusion, reflecting the RIPC model. A concern about BFRE, however, is potential amplification of the exercise pressor reflex, which could be unsafe in at-risk populations. We hypothesized that cyclical BFRE would elicit greater increases in sympathetic outflow and arterial pressure than conventional exercise (CE) when performed at the same relative intensity. We also assessed the cerebrovascular responses due to potential implementation of BFRE in stroke rehabilitation. Fourteen subjects performed treadmill exercise at 65-70% maximal heart rate with and without intermittent BFR (4 × 5-min intervals of bilateral thigh-cuff pressure followed by 5-min reperfusion periods). Mean arterial pressure (MAP), plasma norepinephrine (NE), and middle and posterior cerebral artery velocities (MCAv and PCAv) were compared between trials. As expected, BFRE elicited higher concentration NE compared with CE (1249 ± 170 vs. 962 ± 114 pg/ml; P = 0.06). Unexpectedly, however, there were no differences in MAP between conditions (overall P = 0.33), and MAP was 4-5 mmHg lower with BFRE versus CE during the reperfusion periods (P ≤ 0.05 for reperfusion periods 3 and 4). There were no differences in MCAv or PCAv between trials (P ≥ 0.22), suggesting equivalent cerebrometabolic demand. The exaggerated sympathoexcitatory response with BFRE was not accompanied by higher MAP, likely because of the cyclical reperfusions. This cyclical BFRE paradigm could be adapted to cardiac or stroke rehabilitation, where exercising patients could benefit from the cardio and cerebro protection associated with RIPC.