Cerebral Vasomotor Reactivity Research Articles

Cerebral vasomotor reactivity to carbon dioxide using the rebreathe technique: assessment of within-day and between-day repeatability.

The cerebral vasodilator response to increased arterial carbon dioxide (CO2) concentration, termed cerebral vasomotor reactivity (CVMR), is used to assess cerebral vascular function. We sought to assess the within-day and between-day repeatability of CVMR to rebreathing-induced hypercapnia. Twelve healthy adults performed a within-day short interval protocol (17 ± 2 min between trials), ten performed a within-day long interval protocol (145 ± 16 min between trials), and seventeen performed a between-day protocol (5 ± 2 days between visits). Repeatability of the slope of the percent change in middle cerebral artery mean blood velocity (%MCAvmean) and cerebral vascular conductance index (%CVCi), to the change in partial pressure of end-tidal CO2 ([Formula: see text]) between the two trials/days was assessed. Within-day short interval, %MCAvmean slope demonstrated fair to excellent repeatability (intraclass correlation, ICC = 0.92 [95% confidence interval 0.72-0.98]; P < 0.001) while %CVCi slope showed more variability (ICC = 0.84 [0.47-0.95]; P = 0.002]). Within-day long interval, %MCAvmean (ICC = 0.95 [0.80-0.99]) and %CVCi (ICC = 0.94 [0.71-0.99]) slopes showed good to excellent and fair to excellent repeatability respectively (P < 0.001 for both). For between-day trials, better repeatability was observed for %CVCi (ICC = 0.85 [0.57-0.95]; P < 0.001) compared with %MCAvmean (ICC = 0.76 [0.33-0.91]; P = 0.004) slope. These findings indicate repeatable within- and between-day CVMR responses to rebreathe-induced hypercapnia. However, a longer interval may be better for within-day repeat trials, particularly for CVCi measures.NEW & NOTEWORTHY The cerebral vasodilator response to increases in arterial carbon dioxide concentration, termed cerebral vasomotor reactivity, provides an index of cerebral vascular function/health. Reduced responses are present in populations with elevated cerebral vascular and neurocognitive disease risk/overt disease. Cerebral vasomotor reactivity is often assessed during rebreathing-induced hypercapnia. This study determined that the day-to-day and between-day variability in this response is repeatable, thereby providing important methodological information to the scientific community.

Carbon dioxide induced cerebral vasomotor reactivity in moderate-to-severe cerebral venous thrombosis patients and its impact on prognosis: A transcranial doppler-based prospective exploratory study

Hyperventilation-induced intracranial pressure reduction might be impaired in cerebral venous thrombosis (CVT) patients. Using transcranial Doppler, we assessed carbon dioxide-vasomotor reactivity (CO2-VMR) within 24 hours of admission in CVT patients and studied its correlation with patient outcomes. Adult moderate-severe CVT patients (participants of another large observational study) were included. CO2-VMR was calculated as the percentage change in peak flow velocities during maximal hypercapnia and hypocapnia. Outcome was assessed with the modified Rankin scale (mRS) at one − month post-discharge, dichotomized into favourable (mRS≤2) and unfavourable (mRS>2). Twenty patients’ data was analysed. Impaired CO2-VMR (<70 %) was observed in 13 patients in the affected hemisphere; among them, 10 had impairments in both hemispheres. CO2-VMR correlated negatively with mRS (Rho = -0.688, p = 0.001). Odds for unfavourable outcomes were reduced by 92 % in patients with intact VMR on the ipsilateral hemisphere (Odds ratio (OR) 0.08, Confidence interval (CI) 0.006–––0.636, p = 0.027) and by 94 % with VMR intact on the contralateral hemisphere (OR 0.063, CI 0.003–––0.569, p = 0.03). Thus, impaired CO2-VMR in moderate to severe CVT patients is associated with unfavourable outcomes, and has the potential to prognosticate CVT patients objectively.

Cerebral vasomotor reactivity in the acute phase and after 6 months in non-disabling stroke/TIA: A prospective cohort study

Background and aimCerebral Vasomotor Reactivity (VMR) is a property of cerebral hemodynamics that protects from cerebrovascular disease. We aimed to explore the VMR longitudinal changes in patients with acute non-disabling stroke/Transient Ischemic Attack (TIA) to understand its implication in stroke ethiopatogenesis. MethodsVMR by Transcranial Doppler Breath Holding test was performed at 48-72 h from stroke onset (T1) and after 6 months (T2) on MCA of the non-affected hemisphere and PCA of the affected hemisphere. ResultsWe consecutively enrolled 124 patients with a median age of 66.0 (IQR 54.75-74.25) years with a median NIHSS 2 (IQR 1-3). Both MCA (1.38 %/s SD 0.58) and PCA (1.35 %/s SD 0.75) BHI at T1 did not differ among different stroke subtypes (p=0.067 and p=0.350; N=124). MCA and PCA BHI decreased from T1 to T2 (respectively 1.39 %/s SD 0.56 vs 1.18%/s SD 0.44 and 1.30 %/s SD 0.69 vs 1.20 %/s SD 0.51; N=109) regardless of ethiopatogenesis (respectively p<0.0001 and p=0.111). ConclusionThe VMR is higher in acute phase than at 6 months in patients with non-disabling stroke/TIA, regardless of etiopathogenesis. The higher VMR in acute phase could be sustained by an increased Cerebral Blood Flow due to collateral circulation activation supporting the ischemic zone.

Indices of cerebral vascular function &amp; health in young healthy adults: impact of sex and race

Background: Cerebral vascular diseases and neurocognitive conditions including stroke, cognitive impairment, &amp; Alzheimer’s disease and related dementias are the fastest growing causes of morbidity and mortality. Studies have demonstrated sex differences in indices of physiological function associated with cardiovascular and metabolic disease risk/prevalence. Further, the incidence of these conditions is elevated in Black (BL) individuals; however, BL females have a reduced age adjusted stroke mortality compared to BL males. Reduced cerebral vascular function/health contributes to the risk for these conditions. Limited studies have examined the influence of sex and race on indices of cerebral vascular function/health. This study examined the potential interaction between race and sex in cerebral pulsatility index (PI: index of cerebral vascular stiffness) and cerebral vasomotor reactivity (CVMR) to a hypercapnic challenge (index of cerebral vasodilatory responsiveness). Hypothesis: We hypothesized: 1) females would have reduced PI and elevated CVMR relative to males. 2) BL individuals would exhibit augmented PI and reduced CVMR. 3) BL females would have reduced PI relative to BL males. 4) Lastly, we posit that CVMR will be negatively correlated with PI. Methods: Data is presented from 136 young healthy individuals. 40 BL males (age: 22±3 yr, BMI: 25±4 kg/m²), 37 BL females (age: 21±3 yr, BMI: 24±4 kg/m²), 39 White (WH) males (age: 24±3 yr, BMI: 25±3 kg/m²), and 20 WH females (age: 25±6 yr, BMI: 23±3 kg/m²). Heart rate, beat-to-beat blood pressure, end-tidal carbon dioxide concentration (PETCO2), and middle cerebral artery blood velocity (MCAv) were continuously recorded (minimum of 6 min). Cerebral vascular function/health was indexed as (a) PI ((MCAVv systolic − MCAv diastolic)/MCAv mean). (b) CVMR assessed as % increase in cerebral vascular conductance (CVCi) slope during a hypercapnic challenge (%CVCi/ΔPETCO2). Results: PI was elevated in males (male: 0.86±0.18, female: 0.77±0.11, P=0.03). There was no difference between races (WH: 0.83±0.19, BL: 0.79±0.13, P=0.27) nor was there a sex x race interaction ( P=0.54). CVMR assessed as %CVCi slope was not different between sexes (male: 2.4±1.7 %/mmHg, female: 2.7±1.2 %/mmHg, P=0.16) or BL &amp; WH (WH: 2.7±1.3 %/mmHg, BL: 2.4±1.1 %/mmHg, P=0.16). CVMR was lower in the BL males relative to the BL females (BL male: 2.0±0.9 %/mmHg, BL female: 2.8±1.2 %/mmHg, P=0.002). There was no difference between WH males and females ( P=0.88). Lastly, there was not a significant correlation between PI and CVMR to hypercapnia ( P=0.16). Conclusion: These preliminary data suggest that relatively young and otherwise health White and Black females have augmented indices of cerebral vascular function/health relative to males. Furthermore, BL males have reduced cerebral vasodilatory responsiveness to a hypercapnic stimuli. The University of Texas at Arlington College of Nursing and Health Innovation and Institutional Start up Funds to Dr. Brothers. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Statin treatment intensity and cerebral vasomotor reactivity response in patients with ischemic stroke.

Cerebral vasomotor reactivity (VMR) is vital for regulating brain blood flow and maintaining neurological function. Impaired cerebral VMR is linked to a higher risk of stroke and poor post-stroke outcomes. This study explores the relationship between statin treatment intensity and VMR in patients with ischemic stroke. Seventy-four consecutive patients (mean age 69.3 years, 59.4% male) with recent ischemic stroke were included. VMR levels were assessed 4 weeks after the index stroke using transcranial Doppler, measuring the breath-holding index (BHI) as an indicator of the percentage increase in middle cerebral artery blood flow (higher BHI signifies higher VMR). Multistep multivariable regression models, adjusted for demographic and cerebrovascular risk factors, were employed to examine the association between statin intensity treatment and BHI levels. Forty-one patients (55%) received high-intensity statins. Patients receiving high-intensity statins exhibited a mean BHI of 0.85, whereas those on low-intensity statins had a mean BHI of 0.67 (mean difference 0.18, 95% confidence interval: 0.13-0.22, p-value<.001). This significant difference persisted in the fully adjusted model (adjusted mean values: 0.84vs. 0.68, p-value:.008). No significant differences were observed in BHI values within patient groups on high-intensity or low-intensity statin therapy (all p-values>.05). Furthermore, no significant association was found between baseline low-density lipoprotein (LDL) levels and BHI. High-intensity statin treatment post-ischemic stroke is linked to elevated VMR independent of demographic and clinical characteristics, including baseline LDL level. Further research is needed to explore statin therapy's impact on preserving brain vascular function beyond lipid-lowering effects.

Correlation between Morphological and Hemodynamic Parameters of Carotid Arteries and Cerebral Vasomotor Reactivity.

The function of cerebral small vessels can be assessed using cerebral vasomotor reactivity (VMR). Our aim in this retrospective cross-sectional study was to investigate a correlation between carotid artery stenosis measured through ultrasonographic morphological and hemodynamic parameters and cerebral VMR. A total of 285 patients (125 males; mean age 54) were included. The breath-holding index (BHI) was used to evaluate cerebral VMR. Ultrasonographic carotid artery parameters were collected: the presence and characteristics of carotid plaques, the degree of carotid diameter stenosis, intima-media thickness (IMT), peak systolic velocity (PSV), and end diastolic velocity (EDV). Additionally, hemodynamic parameters of the middle cerebral artery (MCA) were evaluated, including the mean flow velocity (MFV) and pulsatility index (PI). The following was collected from patients' medical histories: age, gender, and vascular risk factors. A negative correlation between the BHI and age (r = -0.242, p < 0.01), BHI and the presence of carotid plaques, BHI and IMT (r = -0.203, p < 0.01), and BHI and the PI of MCA on both sides (r = -0.268, p < 0.01) was found. We found a positive correlation between the BHI in the left MCA and EDV in the left internal carotid artery (r = 0.121, p < 0.05). This study shows the correlation between cerebral VMR and carotid stenosis but indicates a higher influence of morphological parameters on VMR values.

The Effects of Acetazolamide on Cerebral Hemodynamics in Adult Patients with an Acute Brain Injury: A Systematic Review.

Acetazolamide is a non-competitive inhibitor of carbonic anhydrase, an enzyme expressed in different cells of the central nervous system (CNS) and involved in the regulation of cerebral blood flow (CBF). The aim of this review was to understand the effects of acetazolamide on CBF, intracranial pressure (ICP) and brain tissue oxygenation (PbtO2) after an acute brain injury (ABI). Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (PRISMA), we performed a comprehensive, computer-based, literature research on the PubMed platform to identify studies that have reported the effects on CBF, ICP, or PbtO2 of acetazolamide administered either for therapeutic or diagnostic purposes in patients with subarachnoid hemorrhage, intracerebral hemorrhage, traumatic brain injury, and hypoxic-ischemic encephalopathy. From the initial search, 3430 records were identified and, through data selection, 11 of them were included for the qualitative analysis. No data on the effect of acetazolamide on ICP or PbtO2 were found. Cerebral vasomotor reactivity (VMR-i.e., the changing in vascular tone due to a vasoactive substance) to acetazolamide tends to change during the evolution of ABI, with the nadir occurring during the subacute stage. Moreover, VMR reduction was correlated with clinical outcome. This systematic review showed that the available studies on the effects of acetazolamide on brain hemodynamics in patients with ABI are scarce. Further research is required to better understand the potential role of this drug in ABI patients.

Cerebral Vasomotor Reactivity Testing in the Middle Cerebral Artery Using Transcranial Doppler to Assess Brain Dysregulation in Long-Haul COVID Patients for CME Credit December 2023

Cerebral Vasomotor Reactivity Testing in the Middle Cerebral Artery Using Transcranial Doppler to Assess Brain Dysregulation in Long-Haul COVID Patients for CME Credit December 2023

Cerebral Vasomotor Reactivity Testing in the Middle Cerebral Artery Using Transcranial Doppler to Assess Brain Dysregulation in Long-haul COVID Patients

Introduction: COVID-19 has wide-ranging physiological effects, with many patients complaining of persistent asthenia following recovery from the acute phase of the infection. The frequent term for this is “Long-Haul COVID.” While we have tools to measure effects on general physiology in human subjects, a metric for cerebral dysregulation is lacking. Cerebral blood flow is closely regulated in a healthy young person. Cerebral vasomotor reactivity (CVR) was used as a tool to assess this dysregulation. Methods: A transcranial Doppler (TCD) study for CVR was performed under the influence of Carbogen gas. A questionnaire collected prior to the procedure provided additional details on subjects’ demographics and COVID history. Cases and controls were recruited using the self-reported questionnaire. Statistics involved assessing the reproducibility of the test, as well as discovering differences between cases and control groups. Results: Cerebral vasomotor reactivity was assessed in 26 subjects (10 cases and 16 controls). Mean flow velocity in the left middle cerebral artery was analyzed at baseline, at peak Carbogen gas exposure, and in the hypercapnic phase. The reproducibility of the test was established within the longitudinal repeated measures data. The case and control groups were insignificant in difference at the base level but significant when controlled for confounders. Cerebral vasomotor reactivity was found to increase by 3.8 units in cases compared to controls. Confounders like body mass index, gender, and age were found significantly different between cases and controls. The number of COVID episodes and symptom severity was significant for CVR. Conclusion: This simple TCD bedside test was found to be effective in assessing CVR among all the subjects and was homogenous in its effect irrespective of baseline subject differences. As a preliminary test, the test showed differences among cases and control groups. The sample for the test lacked sufficient power and observations. A bigger sample size and a subsequent longitudinal follow-up may help better understand the use of CVR to screen high-risk populations for cerebrovascular anomalies.

Stroke vs. Preeclampsia: Dangerous Liaisons of Hypertension and Pregnancy.

Stroke during pregnancy and preeclampsia are two distinct but interrelated medical conditions, sharing a common denominator-blood control failure. Along with cardiovascular diseases, diabetes, dyslipidemia, and hypercoagulability, hypertension is undoubtedly a major risk factor associated with stroke. Even though men have higher age-specific stroke rates, women are facing higher life-long stroke risk, primarily due to longer life expectancy. Sex hormones, especially estrogen and testosterone, seem to play a key link in the chain of blood pressure control differences between the genders. Women affected with stroke are more susceptible to experience some atypical stroke manifestations, which might eventually lead to delayed diagnosis establishment, and result in higher morbidity and mortality rates in the population of women. Preeclampsia is a part of hypertensive disorder of pregnancy spectrum, and it is common knowledge that women with a positive history of preeclampsia are at increased stroke risk during their lifetime. Preeclampsia and stroke display similar pathophysiological patterns, including hypertension, endothelial dysfunction, dyslipidemia, hypercoagulability, and cerebral vasomotor reactivity abnormalities. High-risk pregnancies carrying the burden of hypertensive disorder of pregnancy have up to a six-fold higher chance of suffering from stroke. Resemblance shared between placental and cerebral vascular changes, adaptations, and sophisticated auto-regulatory mechanisms are not merely coincidental, but they reflect distinctive and complex cardiovascular performances occurring in the maternal circulatory system during pregnancy. Placental and cerebral malperfusion appears to be in the midline of both of these conditions; placental malperfusion eventually leads to preeclampsia, and cerebral to stoke. Suboptimal performances of the cardiovascular system are proposed as a primary cause of uteroplacental malperfusion. Placental dysfunction is therefore designated as a secondary condition, initiated by the primary disturbances of the cardiovascular system, rather than an immunological disorder associated with abnormal trophoblast invasion. In most cases, with properly and timely applied measures of prevention, stroke is predictable, and preeclampsia is a controllable condition. Understanding the differences between preeclampsia and stroke in pregnancy is vital for healthcare providers to enhance their clinical decision-making strategies, improve patient care, and promote positive maternal and pregnancy outcomes. Management approaches for preeclampsia and stroke require a multidisciplinary approach involving obstetricians, neurologists, and other healthcare professionals.

Cerebral Vasomotor Reactivity in COVID-19: A Narrative Review.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) primarily affects the respiratory system but can also lead to neurological complications. Among COVID-19 patients, the endothelium is considered the Achilles heel. A variety of endothelial dysfunctions may result from SARS-CoV-2 infection and subsequent endotheliitis, such as altered vascular tone, oxidative stress, and cytokine storms. The cerebral hemodynamic impairment that is caused is associated with a higher probability of severe disease and poor outcomes in patients with COVID-19. This review summarizes the most relevant literature on the role of vasomotor reactivity (VMR) in COVID-19 patients. An overview of the research articles is presented. Most of the studies have supported the hypothesis that endothelial dysfunction and cerebral VMR impairment occur in COVID-19 patients. Researchers believe these alterations may be due to direct viral invasion of the brain or indirect effects, such as inflammation and cytokines. Recently, researchers have concluded that viruses such as the Human Herpes Virus 8 and the Hantavirus predominantly affect endothelial cells and, therefore, affect cerebral hemodynamics. Especially in COVID-19 patients, impaired VMR is associated with a higher risk of severe disease and poor outcomes. Using VMR, one can gain valuable insight into a patient's disease progression and make more informed decisions regarding appropriate treatment options. A new pandemic may develop with the COVID-19 virus or other viruses, making it essential that healthcare providers and researchers remain focused on developing new strategies for improving survival in such patients, particularly those with cerebrovascular risk factors.

Evaluation of Cerebral Vasomotor Reactivity by Transcranial Doppler Ultrasound in Patients with Diabetic Retinopathy

ABSTRACT The aim of this study was to assess the correlation between cerebral vasomotor reactivity (CVR) and the grade of diabetic retinopathy. A total of 43 diabetic patients with matched severity of diabetic retinopathy between their right and left eyes were included in this study. Diabetic retinopathy was graded in three groups. Right and left middle cerebral artery CVR was assessed by the breath-holding index (BHI) using transcranial Doppler ultrasound (TCD). The mean age of the patients was 56.51 ± 9.34 years with a mean duration of having diabetes mellitus of 14.49 ± 8.06 years. Diabetic retinopathy was graded as mild, moderately severe, and severe in 27.9%, 34.9%, and 37.2% of the patients, respectively. The grade of diabetic retinopathy was associated with the HbA1c level (p < .049), microalbuminuria (p < .024), and BHI (p = .001). In patients with severe diabetic retinopathy, the right-sided BHI was significantly lower as compared to those with mild or moderately severe retinopathy (p = .001 and p = .008, respectively). The left-sided BHI value in patients with severe diabetic retinopathy was significantly lower as compared to those with mild or moderately severe retinopathy (p = .001 and p = .012, respectively). In subjects with moderately severe diabetic retinopathy, both-sided BHI was significantly reduced compared to those with mild retinopathy (p = .001). Our results indicate that the grade of diabetic retinopathy was associated with impaired CVR.

Cerebral vasomotor reactivity across the continuum of subjective cognitive impairment, amnestic mild cognitive impairment and probable Alzheimer's dementia: A transcranial Doppler and PET/MRI study

Cerebrovascular dysfunction has been suggested as a physiomarker of Alzheimer's disease (AD)-associated neuronal degeneration, but the underlying mechanisms are still debated. Herein cerebral vasomotor reactivity (VMR, breath-hold index: BHI), metabolic activity (lobar SUVs, FDG PET MRI), amyloid load (Centiloid score, Flutemetamol PET MRI), hemispheric cortical thickness, white matter lesion load and cerebral blood flow (ASL) were studied in 43 consecutive subjects (mean age: 64 years, female 13), diagnosed with subjective cognitive impairment (SCI, n = 10), amnestic mild cognitive impairment (aMCI, n = 15), and probable Alzheimer's dementia (AD, n = 18). BHI was significantly reduced in AD and aMCI patients compared to SCI subjects. A highly significant inverse correlation was found between BHI and the centiloid score (r = −0.648, p < 0.001). There was moderate positive correlation between BHI and frontal, temporal and parietal FDG SUV and ASL values, and a borderline negative correlation with age and white matter lesion volume. The link between amyloid burden and VMR was independent and strong in linear regression models where all these parameters were included (β from –0.580 to –0.476, p < 0.001). In conclusion, our study confirms the negative association of cerebral amyloid accumulation and vasomotor reactivity in Alzheimer's disease with the most direct data to date in humans.

Cerebral hemodynamic changes to transcranial Doppler sonography in celiac disease: A pilot study.

BackgroundSonographic mesenteric pattern in celiac disease (CD) suggests a hyperdynamic circulation. Despite the well-known CD-related neurological involvement, no study has systematically explored the cerebral hemodynamics to transcranial Doppler sonography.Materials and methodsMontreal Cognitive Assessment (MoCA) and 17-item Hamilton Depression Rating Scale (HDRS) were assessed in 15 newly diagnosed subjects with CD and 15 age-, sex-, and education-matched healthy controls. Cerebral blood flow (CBF) velocities and indices of resistivity (RI) and pulsatility (PI) from the middle cerebral artery (MCA), bilaterally, and the basilar artery (BA) were recorded. We also assessed cerebral vasomotor reactivity (CVR) through the breath-holding test (BHT).ResultsWorse scores of MoCA and HDRS were found in patients compared to controls. Although patients showed higher values of CBF velocity from MCA bilaterally compared to controls, both at rest and after BHT, no comparison reached a statistical significance, whereas after BHT both RI and PI from BA were significantly higher in patients. A significant negative correlation between both indices from BA and MoCA score were also noted.ConclusionThese treatment-naïve CD patients may show some subtle CVR changes in posterior circulation, thus possibly expanding the spectrum of pathomechanisms underlying neuroceliac disease and in particular gluten ataxia. Subclinical identification of cerebrovascular pathology in CD may help adequate prevention and early management of neurological involvement.

Effect of Hyperinsulinemia on Cerebral Autoregulation and Myogenic Control of Cerebral Blood Flow in Healthy Young Adults

ObjectiveHyperinsulinemia has marked vasodilatory effects within the skeletal muscle vasculature in healthy young adults; however, the magnitude of insulin‐stimulated cerebrovascular vasodilation is less clear. Differences between circulations may be due to a greater importance of the cerebral circulation to maintain a constant level of blood flow (i.e., cerebral autoregulation) during hyperinsulinemia. We hypothesized cerebral autoregulation would increase during hyperinsulinemia. Autoregulatory mechanisms, such as myogenic control, play important roles in mediating cerebral vasomotor responses. Thus, we further sought to examine the contribution of the myogenic mechanism to the control of cerebral blood flow during hyperinsulinemia.MethodsMiddle cerebral artery blood velocity (MCAv) and femoral artery blood velocity (FAV) were measured with Doppler ultrasound and femoral artery blood flow (FBF) was calculated in 17 healthy adults (11M/6F, 28±2 yrs, 24±1 kg/m2) at baseline and following a hyperinsulinemic (40 mU/m2body surface area/min), euglycemic infusion. Finger plethysmography was used to assess mean blood pressure (MBP). Normalized transfer function gain between changes in MBP and MCAv were estimated in the 0.02‐0.07 Hz (very low frequency, VLF) and 0.07–0.20 Hz (low frequency, LF) ranges using the Welch method. Interactions between MBP and MCAv or FAV were determined using cross‐correlation analyses.ResultsIntravenous insulin infusion increased plasma insulin concentrations (6±1 to 50±3 μIU/mL, p&lt;0.01) with blood glucose maintained at baseline levels (p=0.33). There was a significant increase in FBF (121±15 to 151±19 mL/min, p=0.03) during hyperinsulinemia, with no change in MCAv (61±4 to 59±4 cm/s, p=0.28) or MBP (86±2 to 89±2 mmHg, p=0.10). There was no effect of hyperinsulinemia on normalized transfer function gain in the VLF (p=0.25) or LF ranges (p=0.46). Hyperinsulinemia had no effect on the association between MBP and MCAv (p=0.15) or FAV (p=0.82).ConclusionsHyperinsulinemia in healthy young adults elicits peripheral vasodilation, but no change in MCAv. Contrary to our hypothesis, the sensitivity of the cerebrovascular circulation to changes in MBP (i.e., cerebral autoregulation) is not altered during systemic hyperinsulinemia in healthy adults. Furthermore, the contribution of the myogenic mechanism to the control of blood flow in the peripheral and cerebral circulations is unaffected by hyperinsulinemia. Whether these results translate to disease states (e.g., diabetes) and the implications for cerebrovascular health warrant further exploration.

Young, non-Hispanic Black men and women exhibit divergent peripheral and cerebral vascular reactivity.

What is the central question of the study? Do peripheral and cerebral vascular function differ between young non-Hispanic Black men and women? What is the main finding and its importance? The non-Hispanic Black women in this study presented greater peripheral conduit artery and cerebrovascular reactivity, yet similar peripheral microvascular function relative to the non-Hispanic Black men. These preliminary findings suggest that young Black women and men possess divergent vascular function, possibly contributing to the unique non-Hispanic Black sex differences in cardiovascular and cerebrovascular diseases. In the USA, cardiovascular and cerebrovascular diseases remain more prominent in the non-Hispanic Black (BL) population relative to other racial/ethnic groups. Typically, sex differences emerge in the manifestation of these diseases, though these differences may not fully materialize in the BL population. While numerous mechanisms are implicated, differences in vascular function likely contribute. Research has demonstrated blunted vasodilatation in several vascular regions in BL versus non-Hispanic White individuals, though much of this work did not assess sex differences. Therefore, this study aimed to ascertain if indices of vascular function are different between young BL women (BW) and men (BM). Eleven BW and 15BM (22 (4) vs. 23 (3) years) participated in this study. Each participant underwent testing for brachial artery flow-mediated dilatation (FMD), post-occlusive reactive hyperaemia and cerebral vasomotor reactivity during rebreathing-induced hypercapnia. BW exhibited greater adjusted FMD than BM (P<0.05 for all), but similar or lower reactive hyperaemia when assessed as blood velocity (P>0.39 for all) or blood flow reactivity (P<0.05 for all), respectively. Across a range of hypercapnia, BW had greater middle cerebral artery blood velocity and cerebrovascular conductance index than BM (P<0.001 for both). These preliminary data suggest that young BW have greater vascular function relative to young BM, though this was inconsistent across different indices. These findings provide insight into the divergent epidemiological findings between BM and BW. Further research is needed to elucidate possible mechanisms and relate these physiological responses to epidemiological observations.

Evaluation of cerebral hemodynamic status in patients with unilateral symptomatic carotid artery stenosis during motor tasks, through use of transcranial Doppler sonography.

Carotid artery stenosis increases cerebral ischemic event risk through changing different cerebral hemodynamic parameters. To investigate how cerebral hemodynamics in the M1 segment of middle cerebral artery change in patients with carotid artery stenosis, after motor tasks using transcranial Doppler sonography (TCD). Thirty-two healthy subjects and 30 patients with unilateral symptomatic carotid artery stenosis were recruited. The patient population was divided into three groups according to the degree of stenosis (group 1: ≥50 to 69%, group 2: 70 to 89% and group 3: ≥90 to 99%). TCD was used to measure the pulsatility index (PI) and cerebral vasomotor reactivity (CVR). In the patient group, significant differences for symptomatic side PI values (p=0.01) and mean CVR increases (p=0.05) were observed, compared with the healthy controls. However, the difference was not statistically significant for asymptomatic side PI values and mean CVR increases. The results from the intergroup comparison showed significantly higher percentages of symptomatic and asymptomatic side CVR increases in group 1, compared with groups 2 and 3 (p=0.001 and p=0.002, respectively). Our study showed that cerebral autoregulation and hemodynamic mechanisms are impaired in patients with carotid artery stenosis. Furthermore, the impairment of PI and CVR tends to get worse with increasing degrees of stenosis. In addition, this study demonstrated that assessment of these two hemodynamic parameters in clinical practice might be helpful for monitoring the progress of carotid artery stenosis.

Cerebrovascular responses to somatomotor stimulation in Parkinson’s disease: A multivariate analysis

Parkinson’s disease (PD) is a common neurodegenerative disorder, yet little is known about cerebral haemodynamics in this patient population. Previous studies assessing dynamic cerebral autoregulation (dCA), neurovascular coupling (NVC) and vasomotor reactivity (VMR) have yielded conflicting findings. By using multi-variate modelling, we aimed to determine whether cerebral blood flow (CBF) regulation is impaired in PD patients. 55 healthy controls (HC) and 49 PD patients were recruited. PD subjects underwent a second recording following a period of abstinence from their anti-Parkinsonian medication. Continuous bilateral transcranial Doppler in the middle cerebral arteries, beat-to-beat mean arterial blood pressure (MAP; Finapres), heart rate (HR; electrocardiogram), and end-tidal CO2 (EtCO2; capnography) were measured. After a 5-min baseline period, a passive motor paradigm comprising 60 s of elbow flexion was performed. Multi-variate modelling quantified the contributions of MAP, ETCO2 and neural stimulation to changes in CBF velocity (CBFV). dCA, VMR and NVC were quantified to assess the integrity of CBF regulation. Neural stimulation was the dominant input. dCA, NVC and VMR were all found to be impaired in the PD population relative to HC (p < 0.01, p = 0.04, p < 0.01, respectively). Our data suggest PD may be associated with depressed CBF regulation. This warrants further assessment using different neural stimuli.

Intracranial pressure dynamics and cerebral vasomotor reactivity in community-acquired bacterial meningitis during neurointensive care.

Community-acquired bacterial meningitis (CABM) is a severe condition associated with high mortality. In this study the first aim was to evaluate the incidence of intracranial pressure (ICP) insults and disturbances in cerebral vasomotor reactivity and the second aim was to evaluate the management and clinical outcome of CABM patients treated in the neurointensive care unit (NICU). CABM patients who were treated in the NICU of Uppsala University Hospital, Sweden, during 2008-2020 were included in the study. Data on demographics, admission variables, treatment, ICP dynamics, vasomotor reactivity, and short-term clinical outcome were evaluated in these patients. Of 97 CABM patients, 81 (84%) received ICP monitoring, of whom 22% had ICP > 20 mm Hg during 5% or more of the monitoring time on day 1, which decreased to 9% on day 3. For those patients with ICP monitoring, 46% required CSF drainage, but last-tier ICP treatment, including thiopental (4%) and decompressive craniectomy (1%), was rare. Cerebral vasomotor reactivity was disturbed, with a mean pressure reactivity index (PRx) above 0.2 in 45% of the patients on day 1, and remained high for the first 3 days. In total, 81 (84%) patients had a favorable outcome (Glasgow Coma Scale motor score [GCS M] 6) at discharge, 9 (9%) patients had an unfavorable outcome (GCS M < 6) at discharge, and 7 (7%) patients died in the NICU. Those with favorable outcome had significantly better cerebral vasomotor reactivity (lower PRx) than the two other outcome groups (p < 0.01). Intracranial hypertension was frequent following severe CABM and CSF drainage was often sufficient to control ICP. Cerebral vasomotor reactivity was commonly disturbed and associated with poor outcome. Clinical outcome was slightly better than in earlier studies.

December 2021 Stroke Highlights

December 2021 <i>Stroke</i> Highlights