Constant Blood Flow Research Articles

Sildenafil does not have a significant effect on the portal vein velocity, cross-sectional area, and congestion index in the dog.

In veterinary medicine, sildenafil is most frequently used to treat pulmonary hypertension, but has also been investigated and used as a treatment for congenital megaesophagus and ischemic infarcts. With the increasing use, the effects of sildenafil on the portal vasculature in the dog have not been previously evaluated. The purpose of this study was to evaluate the effects sildenafil has on the portal vasculature, which anecdotally may have caused decreased portal vein pressure in an adult dog. The ultrasound cross-sectional area of the aorta, cross-sectional area of the portal vein, and portal vein blood flow velocity were acquired in dogs prior to administration, and 45, 90, and 120 min after oral administration of sildenafil for the treatment of pulmonary hypertension. Thirteen dogs were enrolled in the study. No statistically significant difference was detected between all measured values and the congestion index at all time points. A trend was identified that demonstrated progressively lower portal vein velocity with each evaluation, but this was not significant. Although this study had a small sample size, sildenafil was not shown to have a significant effect on the size or blood flow velocity of the portal vasculature. The hepatic buffer system, designed to maintain a constant blood flow to the liver, may be a contributing factor, but further studies with a larger sample size will be required for further evaluation.

Non-Invasive and Minimally-Invasive Cerebral Autoregulation Assessment: A Narrative Review of Techniques and Implications for Clinical Research.

The process of cerebral vessels regulating constant cerebral blood flow over a wide range of systemic arterial pressures is termed cerebral autoregulation (CA). Static and dynamic autoregulation are two types of CA measurement techniques, with the main difference between these measures relating to the time scale used. Static autoregulation looks at the long-term change in blood pressures, while dynamic autoregulation looks at the immediate change. Techniques that provide regularly updating measures are referred to as continuous, whereas intermittent techniques take a single at point in time. However, a technique being continuous or intermittent is not implied by if the technique measures autoregulation statically or dynamically. This narrative review outlines technical aspects of non-invasive and minimally-invasive modalities along with providing details on the non-invasive and minimally-invasive measurement techniques used for CA assessment. These non-invasive techniques include neuroimaging methods, transcranial Doppler, and near-infrared spectroscopy while the minimally-invasive techniques include positron emission tomography along with magnetic resonance imaging and radiography methods. Further, the advantages and limitations are discussed along with how these methods are used to assess CA. At the end, the clinical considerations regarding these various techniques are highlighted.

Advances in the Role of Endothelial Cells in Cerebral Small Vessel Disease.

Cerebral small vessel disease (CSVD) poses a serious socio-economic burden due to its high prevalence and severe impact on the quality of life of elderly patients. Pathological changes in CSVD mainly influence small cerebral arteries, microarteries, capillaries, and small veins, which are usually caused by multiple vascular risk factors. CSVD is often identified on brain magnetic resonance imaging (MRI) by recent small subcortical infarcts, white matter hyperintensities, lacune, cerebral microbleeds (CMBs), enlarged perivascular spaces (ePVSs), and brain atrophy. Endothelial cell (EC) dysfunction is earlier than clinical symptoms. Immune activation, inflammation, and oxidative stress may be potential mechanisms of EC injury. ECs of the blood–brain–barrier (BBB) are the most important part of the neurovascular unit (NVU) that ensures constant blood flow to the brain. Impaired cerebral vascular autoregulation and disrupted BBB cause cumulative brain damage. This review will focus on the role of EC injury in CSVD. Furthermore, several specific biomarkers will be discussed, which may be useful for us to assess the endothelial dysfunction and explore new therapeutic directions.

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

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

Adrenaline improves regional cerebral blood flow, cerebral oxygenation and cerebral metabolism during CPR in a porcine cardiac arrest model using low-flow extracorporeal support

BackgroundThe effects of adrenaline on cerebral blood vessels during cardiopulmonary resuscitation (CPR) are not well understood. We developed an extracorporeal CPR model that maintains constant low systemic blood flow while allowing adrenaline-associated effects on cerebral vasculature to be assessed at different mean arterial pressure (MAP) levels independently of the effects on systemic blood flow. MethodsAfter eight minutes of cardiac arrest, low-flow extracorporeal life support (ECLS) (30 ml/kg/min) was started in fourteen pigs. After ten minutes, continuous adrenaline administration was started to achieve MAP values of 40 (n = 7) or 60 mmHg (n = 7). Measurements included intracranial pressure (ICP), cerebral perfusion pressure (CePP), laser-Doppler-derived regional cerebral blood flow (CBF), cerebral regional oxygen saturation (rSO2), brain tissue oxygen tension (PbtO2) and extracellular cerebral metabolites assessed by cerebral microdialysis. ResultsDuring ECLS without adrenaline, regional CBF increased by only 5% (25th to 75th percentile: −3 to 14; p = 0.2642) and PbtO2 by 6% (0–15; p = 0.0073) despite a significant increase in MAP to 28 mmHg (25–30; p < 0.0001) and CePP to 10 mmHg (8–13; p < 0.0001). Accordingly, cerebral microdialysis parameters showed a profound hypoxic-ischemic pattern. Adrenaline administration significantly improved regional CBF to 29 ± 14% (p = 0.0098) and 61 ± 25% (p < 0.001) and PbtO2 to 15 ± 11% and 130 ± 82% (both p < 0.001) of baseline in the MAP 40 mmHg and MAP 60 mmHg groups, respectively. Importantly, MAP of 60 mmHg was associated with metabolic improvement. ConclusionThis study shows that adrenaline administration during constant low systemic blood flow increases CePP, regional CBF, cerebral oxygenation and cerebral metabolism.

Hydrodynamic model of blood flow in major arteries pulsing in various modes.

Traditionally, the arteries in mammals are viewed as the tubes with elastic wall, whose elasticity could be slowly (during a minute) tuned to change its diameter thereby regulating regional blood supply. Recent findings showed that an artery is a much more sophisticated organ, which can change elasticity of vascular wall within a fraction of a second during a cardiac cycle due to activation of its smooth muscles manifested by generation of arterial action potentials. The rapid variations in elasticity of vascular wall resulted in three basic modes of arterial pulsing: passive, active, and intermediate. The latter is characterized by counteraction of dilation force of arterial pressure and the contractile one of smooth muscle in arterial wall, which can result in seemingly "rigid" artery of constant diameter. The prevalence of any of these forces results in active or passive pulsing modes. Existence of various pulsing modes raises the question of their effect on the main function of blood vessels, i.e., the transport of blood. The aim of this study is to assess the effect of various modes of arterial pulsing on hydraulic impedance of major arteries. The linearized Navier-Stokes equation was employed to develop a model of pulsatile flow of viscous incompressible fluid at small velocity via a conduit artery with the walls of variable or constant elasticity. An essential feature of the developed model is the shape of variable pressure drop applied to the ends of arterial segment, which simulates the real changes in arterial pressure during the heartbeat. Here, it is modeled by periodic (systolic) positive bell-shaped impulses with maxima corresponding to systolic arterial pressure, while the minimal plateau level refers to diastolic arterial pressure. The model assesses the changes in arterial hydraulic impedance during a cardiac cycle relatively to the stable level corresponding to constant blood flow driven by persistent pressure drop. Within intermediate variety of pulsing modes between the active and passive ones, the approximation of rigid arterial segment with infinite elasticity of arterial wall showed that hydraulic impedance in rigid artery is not constant due to inertial properties of the flowing blood. In passive pulsing mode characterized with constant elasticity of arterial wall, the diameter of artery changes in parallel with systolic pressure applied to the ends of arterial segment. At this, the overall change of hydraulic resistance is negative. In active pulsing mode, elasticity of arterial wall varies at different phase shifts relative to arterial pressure due to periodic contractions and relaxation of the smooth muscles in arterial wall. An important feature of active mode is possibility to decrease the hydraulic impedance during the front of arterial pressure. Various experimental modes of artery pulsing can be mathematically simulated. The passive and active modes of pulsing as well as a broad variety of intermediate pulsing modes with various phase shifts between arterial pressure and its diameter result in potency of the arteries to tune its performance in order to meet the regional circulatory requirements. The model showed that active arterial pulsing can diminish the arterial hydraulic impedance and contribute to the work needed for circulation thereby helping the pumping action of the heart.

Modeling acid-base transport in hemodialyzers

One important objective of the hemodialysis treatment is the neutralization of interdialytic acid generation by transport of bicarbonate and other buffer bases from dialysis fluid to the patient via the hemodialyzer. Quantification of solute transport in hemodialyzers, in general, employs the concept of dialysance, a parameter that is often constant for given flow conditions, smaller than both the blood and dialysate flow rates, and independent of the solute concentration difference between blood and dialysate. This approach has been applied to bicarbonate transport in hemodialyzers, but such an approach neglects the transport of dissolved carbon dioxide (CO2) between dialysate and plasma, chemical equilibrium between bicarbonate and CO2, and other acid-base chemical reactions within blood. We describe a novel, one-dimensional model of bicarbonate and CO2 transport in hemodialyzers. The model equations were solved numerically and fitted to published data to estimate mass transfer-area coefficients for the relevant chemical species. Base excess in blood was assumed constant in the hemodialyzer. Simulations were performed for a dialysate bicarbonate concentration of 32 mEq/L at constant blood and dialysate flow rates and different plasma bicarbonate concentrations at the inlet of the hemodialyzer, both with and without CO2 transport. In the latter case, the bicarbonate mass transfer-area coefficient was adjusted to achieve the same total carbon dioxide transport. Calculated dialysance for CO2 exceeded the blood flow rate due to its conversion from bicarbonate in the hemodialyzer, and all calculated dialysances varied with inlet plasma bicarbonate concentration. We concluded that acid-base transport in hemodialyzers cannot be universally characterized by dialysances that are always less than the blood flow rate and independent of the concentration difference between dialysate and blood.

Xiaoxuming Decoction Regulates Vascular Function by Modulating G Protein-Coupled Receptors: A Molecular Docking Study.

Xiaoxuming decoction (XXMD) is a traditional Chinese herbal medicine (CHM) that is used for the treatment of stroke in China. Stroke injury damages the cerebral vasculature and disrupts the autoregulation of vasoconstriction and vasodilatation, which is crucial for maintaining constant cerebral blood flow (CBF). It has been reported that XXMD exerts a positive effect on cerebral circulation in animal models of stroke. However, the mechanisms underlying the regulatory effect of XXMD on vascular tone, and the interactions among the multiple components of XXMD, remain unclear. In this study, XXMD was found to induce relaxation of the basilar artery rings of rats precontracted by 5-hydroxytryptamine (5-HT) in vitro, in a dose-dependent manner. The modulation of vascular tone and the process of cerebral ischemia are mediated via the interactions between G protein-coupled receptors (GPCRs) and their ligands, including 5-HT, angiotensin II (Ang II), and urotensin II (UII). Thus, the potential synergistic effects of the different components of XXMD on the regulation of vasoconstriction and vasodilation were further investigated by molecular docking based on network pharmacology. We constructed and analyzed a database comprising 963 compounds of XXMD and studied the interactions between five vascular GPCRs (5-HT1A receptor (5-HT1AR), 5-HT1B receptor (5-HT1BR), Ang II type 1 receptor (AT1R), beta 2-adrenergic receptor (β2-AR), and UII receptor (UTR)) and the various herbal constituents of XXMD using molecular docking. By constructing and analyzing the compound-target networks of XXMD, we found that Glycyrrhizae Radix et Rhizoma, Ginseng Radix et Rhizoma, and Paeoniae Radix Alba were the three major herbs that contained a large number of compounds with high docking scores. We additionally observed that several constituents of XXMD, including gallotannin, liquiritin apioside, nariutin, 1,2,3,4,6-pentagalloylglucose, folic acid, and ginsenoside Rb1, targeted multiple vascular GPCRs. Moreover, the interactions between the components of XXMD and the targets related to vascular tone constituted the comprehensive cerebrovascular regulatory function of XXMD and provided a material basis of the vasoregulatory function of XXMD. The study reports the contributions of various components of XXMD to the regulatory effects on vascular tone and provides scientific evidence for the multicomponent and multitargeting characteristics of XXMD.

Investigating the role of pericytes in cerebral autoregulation: a modeling study

The brain’s inability to store nutrients for more than a few seconds makes it one of the most tightly regulated systems in the body. Driven by metabolic demand, cerebral autoregulation (CA) ensures a constant cerebral blood flow (CBF) over a ±50% change in arterial blood pressure (ABP) from baseline. Recent evidence suggests that pericytes, contractile cells in the capillary bed, play a previously-ignored regulatory role. To elucidate the CA phenomenon, the role of oxygen metabolism, pericyte activity and neural signaling in CBF modulation were quantified. Driven by nutrient metabolism in the tissue and pressure sensitivity in the vasculature, the model introduced here successfully replicates CA. To highlight the role of different vessel sizes, vessels with a diameter above 1 mm were represented using a lumped parameter model while the microvasculature was illustrated as a branching tree network model. This novel approach elucidated the relationship between the microvasculature’s nutrient supply and arterial regulation. Capillary responses to local increases in neuronal activity were experimentally determined, showing that pericytes can increase the diameter of the adjacent vessel by 2.5% in approximately 1 s. Their response was quantified and included in the computational model as an active component of the capillary bed. To compare the efficacy model presented here to existing ones, four feedback mechanisms were tested. To simulate dynamic CBF regulation a 10% increase in ABP was imposed. This resulted in a 23.79%–34.33% peak increase in CBF, depending on the nature of the feedback mechanism of the model. The four feedback mechanisms that were studied significantly differ in the response time, ultimately highlighting that capillaries play a fundamental role in the rapid regulation of CBF. Conclusively, this study indicates that while pericytes do not greatly alter the peak CBF change, they play a fundamental role in the speed of regulation.

Reduced Flow during Ex-Situ Heart Perfusion Provides Superior Function Preservation and Less Edema Formation

PurposeEx-situ heart perfusion (ESHP) allows continuous functional and metabolic resuscitation of donor hearts before transplantation. Evidence indicates that hearts that are perfused under physiologic conditions lose the normal vasomotor tone and fail in a few hours. We aim to evaluate the reduced coronary flow during ex situ heart perfusion on cardiac function and coronary vascular resistance.MethodsPorcine hearts (n=6 each group) were perfused in working mode for 6 hours either by constant diastolic pressure perfusion (40 mmHg) or constant coronary blood flow rate perfusion (500mL/min). Cardiac functional parameters, coronary vascular resistance (CVR) and metabolism were monitored continuously. Myocardial injury parameter of cardiac troponin I and lipid peroxidation marker oxidized low-density lipoprotein were evaluated in the perfusate. These parameters were compared between groups at different time.ResultsCardiac function was better preserved in the flow control group at 5 hours (T5) of perfusion, indicated by higher stroke work and cardiac index (p<0.05, Figure AC). After perfusion the flow control group showed less edema than the pressure control group (p<0.001, Figure B). Both groups have a significant decrease of CVR, with relative higher in the flow control group (p<0.01, Figure D). cTnI was lower in the flow control group starting at T3, indicating less myocardial injury (p<0.05, Figure E). oxLDL increased in both groups, indicating lipid peroxidation formation; the level in the flow control group was significantly lower in comparison to the pressure control group (p<0.01, Figure F), suggesting less oxidative stress in this group.ConclusionReduced coronary flow during ex-situ heart perfusion decreased edema formation, showed less myocardial damage and oxidative stress which may contribute to better cardiac function preservation. The relative higher coronary vascular resistance induced by reduced coronary flow perfusion may help to maintain the cardiac function. Ex-situ heart perfusion (ESHP) allows continuous functional and metabolic resuscitation of donor hearts before transplantation. Evidence indicates that hearts that are perfused under physiologic conditions lose the normal vasomotor tone and fail in a few hours. We aim to evaluate the reduced coronary flow during ex situ heart perfusion on cardiac function and coronary vascular resistance. Porcine hearts (n=6 each group) were perfused in working mode for 6 hours either by constant diastolic pressure perfusion (40 mmHg) or constant coronary blood flow rate perfusion (500mL/min). Cardiac functional parameters, coronary vascular resistance (CVR) and metabolism were monitored continuously. Myocardial injury parameter of cardiac troponin I and lipid peroxidation marker oxidized low-density lipoprotein were evaluated in the perfusate. These parameters were compared between groups at different time. Cardiac function was better preserved in the flow control group at 5 hours (T5) of perfusion, indicated by higher stroke work and cardiac index (p<0.05, Figure AC). After perfusion the flow control group showed less edema than the pressure control group (p<0.001, Figure B). Both groups have a significant decrease of CVR, with relative higher in the flow control group (p<0.01, Figure D). cTnI was lower in the flow control group starting at T3, indicating less myocardial injury (p<0.05, Figure E). oxLDL increased in both groups, indicating lipid peroxidation formation; the level in the flow control group was significantly lower in comparison to the pressure control group (p<0.01, Figure F), suggesting less oxidative stress in this group. Reduced coronary flow during ex-situ heart perfusion decreased edema formation, showed less myocardial damage and oxidative stress which may contribute to better cardiac function preservation. The relative higher coronary vascular resistance induced by reduced coronary flow perfusion may help to maintain the cardiac function.

Association between circle of Willis and ischemic stroke: a systematic review and meta-analysis

BackgroundCircle of Willis is the main structure that provides constant and regular blood flow to the brain, protects the brain from ischemia. Stroke has remained the second leading cause of death globally in the last fifteen years. It is the fifth leading cause of death in the United States. It is also the leading cause of serious adult disability. Interlinked problems related to ischemic stroke are become increasing nowadays. Strong evidence is needed about the pooled measure of association between the circle of Willis (COW) and ischemic stroke. Therefore, this systematic review and meta-analysis were intended to provide compressive and up to date evidence on the association between the variations of COW and ischemic stroke using the available studies.MethodsPubMed, Google Scholar, Science Direct, and Cochrane Library databases were systematically searched. All essential data were extracted using a standardized data extraction template. The heterogeneity across studies was assessed by using the Cochrane Q test statistic, I2 test statistic, and P-values. A fixed-effect model was used to estimate the pooled effect of the measure association between COW and ischemic stroke.ResultsIn this meta-analysis, 2,718 participants were involved. The pooled measure of association between COW and ischemic stroke was 1.38 (95% CI 0.87, 2.19). Therefore, this indicated that the presence of any variation in COW was 1.38 times more likely to develop ischemic stroke as compared to the patent COW. The presence of hypoplasia/incompleteness in a posterior communicating artery (PcomA) [Pooled OR: 1.34 (95% CI 0.80, 2.25)] and anterior communicating artery (AcomA) [Pooled OR: 1.32 (95% CI 0.81, 2.19)] were a contributing factor for the development of ischemic stroke. Hypertension was the most common comorbid condition, followed by diabetes mellitus, smoking, coronary artery disease, and hyperlipidemia.ConclusionsThere was a non-significant positive association between COW variation and ischemic stroke in this meta-analysis.

Cerebral autoregulation in hypertensive patients: A review

Cerebral Autoregulation (AR) consists of a complex mechanism characterized by the ability of the brain microcirculation to contract and dilate in response to variations in Blood Pressure (BP), aiming at maintaining a constant Cerebral Blood Flow (CBF). Vascular changes induced by Systemic Arterial Hypertension (SAH), such as thickening of the smooth muscle layer and intimal proliferation, result in reduced luminal diameter and increased cerebrovascular resistance (CVR). Here, the mechanisms of AR and the repercussions of these histological changes on the microcirculatory capacity to maintain constant CBF in these patients will be reviewed. The material for this review was taken mostly from electronic journals. To collect publications, PubMed e Cochrane database of systematic reviews were used.

CHANGES OF HORMONAL STATUS IN PREGNANT WOMEN WITH MISCARRIAGE IN EARLY GESTATION TERMS

Introduction. The article represents the results of the study of the placental hormone level during the early stages of gestation (5-20 weeks).&#x0D; The aim of the study. To analyze the level of hormones of the fetoplacental complex in pregnant women with miscarriage, along with the dynamics of changes in these indicators. To evaluate the features of the hormonal status of women during law-risk pregnancy and miscarriage in history and the impact of these features on the functional state of the fetoplacental complex and the subsequent course of pregnancy.&#x0D; Material and methods. We examined 30 somatically healthy women with a physiological course of pregnancy (the control group) and 30 pregnant women with a miscarriage in history (the main group).&#x0D; Research results. It was found that the content of estradiol, chorionic gonadotropin and placental lactogen in the blood plasma of pregnant women of the main group was significantly lower during the entire gestational period compared to the control group. Estradiol levels in pregnant women with miscarriage were 4.2 times lower than in healthy pregnant women. Placental lactogen levels in the main group of pregnant women were 6.1 times lower, and chorionic gonadotropin - 3.7 times lower compared with the control group. There was also a significant backlog in the growth of hormone levels as the pregnancy progressed. In its turn it indicates the development of placental dysfunction in women with a miscarriage in history in the early stages of gestation.&#x0D; Conclusions. As a result of the described changes there is a violation of the first wave of cytotrophoblast invasion and, as a consequence, incomplete gestational remodeling of segments of spiral arteries. The walls of blood vessels are not completely replaced by fibrinoid and the formed placental vessels do not provide a constant flow of arterial blood into the intervillous space. As a result, the uterine-placental area and the formed placenta are not ready to meet the needs of the developing fetus. In the future, this can lead to perinatal losses.

Spaceflight not an eye-popping experience for astronauts.

Spaceflight not an eye-popping experience for astronauts.

HUBUNGAN RESILIENSI DENGAN KUALITAS HIDUP PADA PASIEN GAGAL GINJAL KRONIS YANG MENJALANI HEMODIALISA

Hemodialysis is a diffusion process across a semipermeable membrane to get rid of unwanted substances from the blood and add the desired components, the constant flow of blood from one side of the membrane and the dialysis cleaning solution on the other causes removal of the waste product similar to glomerular filtration. This study aimed at determining the correlation between resilience and life quality in chronic kidney disease patient in Sanjiwani Regional Hospital, Gianyar. This study used descriptive correlational type and the approach model used was cross-sectional. The sampling technique used was non-probability sampling was purposive sampling with a total sample of 72 respondents. Spearman Rank test results to analyze the relationship of resilience with life quality obtained p- value of 0.001, which means there is a correlation between resilience and life quality. The closeness of the correlatiom between the two variables can be seen from the correlation value of 0.592, meaning that the correlation has a moderate closeness, so it can be concluded that the higher the resilience, the better the quality of life of the respondent.

Aerobic Exercise Acutely Improves Dynamic Cerebral Autoregulation During Brain Activation

PURPOSE: Cognitive function is temporarily improved by acute aerobic exercise, especially clinical high-intensity interval exercise (cHIIE; four 4 min bouts of high-intensity exercise) (Tsukamoto et al. 2016). Meanwhile, dynamic cerebral autoregulation (dCA) is an important cerebrovascular mechanism to maintain relatively constant cerebral blood flow (CBF) against the rapid fluctuations in perfusion pressure, but it is impaired during cognitive tasks (causing brain activation) due to cerebral vasodilation (Ogoh et al. 2018). Although it has been demonstrated that dCA is not changed by aerobic exercise (Tsukamoto et al. 2019), which improves cognitive function (Tsukamoto et al. 2016), the impact of aerobic exercise on the brain activation-induced dCA impairment remains unclear. The purpose of the present study was to investigate the changes in dCA during a cognitive task prior to following different types of aerobic exercise. METHODS: Nine healthy male subjects performed three trials in a randomized crossover order; moderate-intensity continuous exercise (for 40 min), low-volume HIIE (lvHIIE; ten 1 min bouts of high-intensity exercise), and cHIIE protocols. The participants performed a 5 min color-word Stroop task (cognitive task) before, immediately after, and 30 min after each exercise bout. Middle cerebral artery blood flow velocity (Transcranial doppler ultrasonography) and arterial pressure (Finger photosplethysmography) were continuously measured to determine dCA using transfer function analysis, and dCA was estimated at rest and during each cognitive task. RESULTS: Before exercise, transfer function phase in the very low-frequency (VLF) was decreased during cognitive task compared to the resting measurement (P < 0.01), indicating that there was brain activation-induced dCA impairment. However, VLF phase during the cognitive task immediately after exercise was higher than before (P < 0.01) and 30 min (P < 0.01) after exercise regardless of exercise protocol, indicating that dCA impairment during the cognitive task was blunted immediately after exercise. CONCLUSIONS: The brain activation-induced dCA impairment is attenuated immediately after exercise. This result implies that aerobic exercise improves dynamic CBF regulation in response to brain activation during a cognitive task.

Impaired cerebral blood flow regulation in chronic traumatic brain injury

Baroreflex sensitivity (BRS) and cerebral autoregulation (CA) play an important role in maintaining constant cerebral blood flow (CBF) during systemic changes in blood pressure (BP). Impaired BRS and CA have been reported in acute traumatic brain injury (TBI) which may also contribute to secondary injury and poorer recovery after acute TBI; however, their status during chronic stages remains elusive. Thus, the goal of this study is to determine whether cardiac BRS and dynamic CA (dCA) were impaired during the chronic stage in patients with single TBI and persistent neurological symptoms. Twenty-two subjects with blunt head TBI ≥ 6 months prior to the study (13 mild and 9 moderate to severe TBI) and persistent symptoms on Rivermead Post-Concussion Symptoms Questionnaire at enrollment were compared to 22 age/sex/fitness level-matched healthy control subjects. Beat-to-beat changes in heart rate, BP, and CBF velocity were measured at rest and during a repeated sit-stand maneuver. Hemodynamic variability, dCA, and cardiac BRS were calculated using spectral and transfer function analyses. We found dCA phase in low frequency (LF) range of 0.07–0.20 Hz was lower in subjects with TBI than in control subjects (0.51 ± 0.19 vs. 0.63 ± 0.26, p = 0.043) during the resting condition. Among subjects with TBI, the lower dCA phase in LF was correlated with poorer performance on measures of cognitive function (all p < 0.05). These findings suggested that subjects with chronic TBI showed impaired dCA which may contribute to persistent cognitive impairment. Cerebrovascular measures may provide a physiological measure to evaluate interventions for chronic TBI and accompanying functional deficits.

Automated CO2 angiography: Injection pressure and volume settings

The purpose of this work was to outline some practical rules for pressure and volume settings in automatic CO2 injection angiographic procedures focusing on the iliac arterial system, since, in current clinical practice, each operator uses his personal experience to obtain imaging results which are not always easy to compare. A theoretical model was thus developed and then verified by a mechanical simulator of the aortoiliac vascular system, with constant and pulsatile blood flow. The conditions of forward and reverse flows have been described, both for constant and pulsatile regimens and pressures, flows, and optical images of the bubbles in glass vessels were simultaneously acquired, analyzed and compared. Our results demonstrated that “good” radiological images (adequate to patient's conditions and clinical need) are strictly related to appropriate settings of gas injection pressure and flow, in accordance with two simple operative rules. These rules prescribe that the patient's pressure, the blood flow in the vessel, and the hydraulic resistance of the gas injection line be known: the first two parameters may be estimated, while the third must be experimentally measured. By following these rules, it is possible to obtain the best results for each clinical setting, a more standardized approach and better imaging during angiographic procedures with carbon dioxide as contrast medium.

Variation of Arteries Forming Circle of Willis in Adult Human Cadavers

Introduction: Circle of Willis is a large arterial anastomosis between internal carotid and vertebrobasilar arterial system. It is the principal collateral channel for constant blood flow to brain. Any changes in its morphology may cause vascular insufficiency of variable severity. Knowledge about its anomalies may elucidate occurrence of cerebrovascular disorders, its presentation, treatment, prognosis and prevention. Methods: An observational study on 107 fresh cadavers was conducted at Maharajgunj Medical Campus from September 2016 to August 2017. After dissection of the scalp and removal of the vault and dura mater, the brain was obtained. Then the Circle of Willis was identified and observed for its completeness, symmetry, presence, origin and number of arteries forming it and the obtained data were documented, photographed and analyzed. Results: Out of 107 cadavers, variations were noted among 15 (14%): out of which 10 were male and 5 female. Twelve cadavers had single variation while 3 had two variations. Accessory anterior cerebral artery was found in 7 (38.90%), fetal origin of right posterior communicating artery in 2 (11.10%), fetal origin of left posterior communicating artery in 4 (22.20%), early bifurcation of left posterior cerebral artery in 1 (5.60%), variant anterior communicating artery in 2 (11.10%), fused anterior cerebral artery in 1 (5.60%) and aneurysm in 1(5.60%) subjects were found. Conclusion: Variations were noted among 15 cadavers (14%), 12 cadavers had single variation while 3 had two variations. The most common variation seen was accessory anterior cerebral artery found in 7 cadavers (38.90%). Most of the variations were found in midline anteriorly followed by right side.

Variation of Arteries Forming Circle of Willis in Adult Human Cadavers

Introduction Circle of Willis is a large arterial anastomosis between internal carotid and vertebrobasilar arterial system. It is the principal collateral channel for constant blood flow to brain. Any changes in its morphology may cause vascular insufficiency of variable severity. Knowledge about its anomalies may elucidate occurrence of cerebrovascular disorders, its presentation, treatment, prognosis and prevention.&#x0D; MethodsAn observational study on 107 fresh cadavers was conducted at Maharajgunj Medical Campus from September 2016 to August 2017. After dissection of the scalp and removal of the vault and dura mater, the brain was obtained. Then the Circle of Willis was identified and observed for its completeness, symmetry, presence, origin and number of arteries forming it and the obtained data were documented, photographed and analyzed.&#x0D; ResultsOut of 107 cadavers, variations were noted among 15 (14%): out of which 10 were male and 5 female. Twelve cadavers had single variation while 3 had two variations. Accessory anterior cerebral artery was found in 7 (38.90%), fetal origin of right posterior communicating artery in 2 (11.10%), fetal origin of left posterior communicating artery in 4 (22.20%), early bifurcation of left posterior cerebral artery in 1 (5.60%), variant anterior communicating artery in 2 (11.10%), fused anterior cerebral artery in 1 (5.60%) and aneurysm in 1(5.60%) subjects were found.&#x0D; ConclusionVariations were noted among 15 cadavers (14%), 12 cadavers had single variation while 3 had two variations. The most common variation seen was accessory anterior cerebral artery found in 7 cadavers (38.90%). Most of the variations were found in midline anteriorly followed by right side.