Middle Cerebral Artery Flow Research Articles

Post-reperfusion hyperperfusion after endovascular stroke treatment: a prospective comparative study of TCD versus MRI

BackgroundIncreased middle cerebral artery (MCA) blood flow velocities on transcranial duplex sonography (TCD) were recently reported in individual patients after successful mechanical thrombectomy (MT) and were related to intracranial hemorrhage...

Low Heart Rate Is Associated with Cerebral Pulsatility after TIA or Minor Stroke.

Beta-blockers are beneficial in coronary artery disease but less so in stroke prevention and dementia, potentially due to reduced heart rate (HR). Cerebral pulsatility is strongly associated with cerebral small vessel disease (SVD) and may be increased by lower diastolic pressures resulting from longer cardiac cycles. Patients 4-6 weeks after TIA or non-disabling stroke (Oxford Vascular Study) underwent 5 minutes continuous monitoring of blood pressure (BP), electrocardiogram (ECG), and middle cerebral artery flow velocity (transcranial ultrasound). Beat-to-beat relationships between HR, blood pressure and Gosling's pulsatility index (MCA-PI) are reported as beta-coefficients from general linear models for each individual. Across 759 patients, average MCA-PI during monitoring was associated with lower HR and diastolic BP (DBP) and greater systolic BP (SBP) (∆MCA-PI per 10 bpm/mmHg: -0.02, -0.04, 0.03, all p < 0.001), with HR particularly associated with low end-diastolic cerebral velocity (0.86, p=0.014). Beat-to-beat HR was strongly associated with concurrent low DBP and high SBP, potentially mediating the association with greater beat-to-beat cerebral pulsatility (average ∆MCA-PI vs HR/DBP/SBP unadjusted: -0.062, -0.052, 0.0092; adjusted for concurrent BP: -0.039, -0.11, 0.041). The beat-to-beat association between HR and MCA-PI increased with age, beta-blockers, arterial stiffness, low HR (age > 70 + HR < 65 vs age < 70 + HR > 65: -0.081 vs -0.024, interaction p < 0.001), and severe SVD on MRI (age > 70 + severe vs age < 70 + none: -0.087 vs -0.047, interaction p=0.03), with interactions between age, severe SVD, and low HR synergistically increasing MCA-PI. Low HR is associated with greater cerebral pulsatility in patients with SVD, potentially mediated by lower diastolic blood flow and representing a novel potential treatment target. ANN NEUROL 2022;92:909-920.

Intracranial Artery Morphology in Pediatric Moya Moya Disease and Moya Moya Syndrome.

Moya Moya disease (MMD) and Moya Moya syndrome (MMS) are cerebrovascular disorders, which affect the internal carotid arteries (ICAs). Diagnosis and surveillance of MMD/MMS in children mostly rely on qualitative evaluation of vascular imaging, especially MR angiography (MRA). To quantitatively characterize arterial differences in pediatric patients with MMD/MMS compared with normal controls. MRA data sets from 17 presurgery MMD/MMS (10M/7F, mean age = 10.0 years) patients were retrospectively collected and compared with MRA data sets of 98 children with normal vessel morphology (49 male patients; mean age = 10.6 years). Using a level set segmentation method with anisotropic energy weights, the cerebral arteries were automatically extracted and used to compute the radius of the ICA, middle cerebral artery (MCA), anterior cerebral artery (ACA), posterior cerebral artery (PCA), and basilar artery (BA). Moreover, the density and the average radius of all arteries in the MCA, ACA, and PCA flow territories were quantified. Statistical analysis revealed significant differences comparing children with MMD/MMS and those with normal vasculature ( P < .001), whereas post hoc analyses identified significantly smaller radii of the ICA, MCA-M1, MCA-M2, and ACA ( P < .001) in the MMD/MMS group. No significant differences were found for the radii of the PCA and BA or any artery density and average artery radius measurement in the flow territories ( P > .05). His study describes the results of an automatic approach for quantitative characterization of the cerebrovascular system in patients with MMD/MMS with promising preliminary results for quantitative surveillance in pediatric MMD/MMS management.

Cerebral Hemodynamics and Regional Oxygen Metabolism during Ductus Arteriosus Ligation in Preterm Infants

Introduction: Neurodevelopmental impairment is a growing concern for preterm infants who received surgical ligation of patent ductus arteriosus (PDA). We aimed to explore the cerebral hemodynamics during the critical period of PDA ligation. Methods: Very-low-birth-weight (VLBW) preterm infants who underwent PDA ligation were prospectively enrolled. Patients were monitored preoperatively and until 72 h post-ligation. Middle cerebral artery (MCA) flow, regional cerebral oxygen saturation (rcSO₂), and cardiac output were measured through Doppler ultrasound, near-infrared spectroscopy, and electrical cardiometry, respectively. Using rcSO₂ <55% indicating cerebral hypoxia, the duration (% of time) and burden (cumulative negative quantity of rsSO₂ <55% × the period [minutes]) were estimated. An abnormal MCA was defined as an MCA flow of <10th percentile of flow velocity or >90th percentile of pulsatility or resistance index. Poor outcomes were defined as in-hospital death or neurologic disorders, either neuroimaging or functional abnormalities, upon discharge. Results: Thirty-two VLBW infants were examined, and 15 (46.9%) had poor outcomes. Infants with poor outcomes had significantly longer duration of cerebral hypoxia (5.4 [2.2–32.3] vs. 1.8 [0.4–5.6] %, p = 0.033) and worse hypoxic burden (2,118 [684–13,549] vs. 622 [88–1,669] %minutes, p = 0.027). In a linear mixed model, rcSO₂ was positively correlated with arterial saturation (β 0.860, 95% CI: 0.649–1.070) and negatively correlated with abnormal MCA flow (β −5.287, 95% CI: −8.238 to −2.335). Conclusion: Longer duration of cerebral hypoxia and worse hypoxic burden post-ligation was associated with an increased risk of in-hospital mortality or neurologic disorders upon discharge in VLBW preterm infants.

Cerebral Autoregulation in Healthy Term Newborns: Brief Report

Cerebral autoregulation is a homeostatic process that maintains cerebral blood flow (CBF) across a range of mean arterial pressures (MAPs). Cerebral autoregulation can be impaired in pathologic systemic and neurological conditions and can lead to cerebral hypoperfusion or cerebral hyperperfusion from low and high MAPs, respectively. 1 Obrist W.D. Gennarelli T.A. Segawa H. Dolinskas C.A. Langfitt T.W. Relation of cerebral blood flow to neurological status and outcome in head-injured patients. J Neurosurg. 1979; 51: 292-300 Crossref PubMed Scopus (116) Google Scholar Little is known about the maturation of cerebral autoregulation after birth or whether there are sex differences in CBF at birth. One study of 16 term neonates without congenital heart disease tested autoregulation using cerebral oximeter monitoring with tilt testing and reported that cerebral autoregulation was intact between three and 10 days. 2 Tran N.N. Kumar S.R. Hodge F.S. Macey P.M. Cerebral autoregulation in neonates with and without congenital heart disease. Am J Crit Care. 2018; 27: 410-416https://doi.org/10.4037/ajcc2018672 Crossref PubMed Scopus (11) Google Scholar Sex differences in CBF have been observed in older ages. Similar to healthy adolescents aged 10 to 16 years and healthy adults, prepubertal girls between four and eight years have higher middle cerebral and basilar artery flow velocities than age-matched boys. 3 Vavilala M.S. Kincaid M.S. Muangman S.L. Suz P. Rozet I. Lam A.M. Gender differences in cerebral blood flow velocity and autoregulation between the anterior and posterior circulations in healthy children. Pediatr Res. 2005; 58: 574-578 Crossref PubMed Scopus (92) Google Scholar ,4 Tontisirin N. Muangman S.L. Suz P. et al. Early childhood gender differences in anterior and posterior cerebral blood flow velocity and autoregulation. Pediatrics. 2007; 119: e610-e615 Crossref PubMed Scopus (62) Google Scholar Studies report that both healthy boys and girls aged between four and 16 years have intact cerebral autoregulation and children aged two to six years have a lower limit of autoregulation (LLA) similar to adolescents and adults. 3 Vavilala M.S. Kincaid M.S. Muangman S.L. Suz P. Rozet I. Lam A.M. Gender differences in cerebral blood flow velocity and autoregulation between the anterior and posterior circulations in healthy children. Pediatr Res. 2005; 58: 574-578 Crossref PubMed Scopus (92) Google Scholar , 4 Tontisirin N. Muangman S.L. Suz P. et al. Early childhood gender differences in anterior and posterior cerebral blood flow velocity and autoregulation. Pediatrics. 2007; 119: e610-e615 Crossref PubMed Scopus (62) Google Scholar , 5 Vavilala M.S. Lee L.A. Lam A.M. The lower limit of cerebral autoregulation in children during sevoflurane anesthesia. J Neurosurg Anesthesiol. 2003; 15: 307-312 Crossref PubMed Scopus (78) Google Scholar This finding means that infants and young children have less cerebral autoregulatory reserve (difference between MAP and LLA) than older children. 5 Vavilala M.S. Lee L.A. Lam A.M. The lower limit of cerebral autoregulation in children during sevoflurane anesthesia. J Neurosurg Anesthesiol. 2003; 15: 307-312 Crossref PubMed Scopus (78) Google Scholar However, girls aged four to 16 years have higher normative autoregulatory indices of the basilar artery compared with age-matched boys and healthy boys aged four to 16 years have higher normative autoregulatory indices of the middle cerebral artery (MCA) compared with healthy girls; the reasons for these differences are not well understood. 3 Vavilala M.S. Kincaid M.S. Muangman S.L. Suz P. Rozet I. Lam A.M. Gender differences in cerebral blood flow velocity and autoregulation between the anterior and posterior circulations in healthy children. Pediatr Res. 2005; 58: 574-578 Crossref PubMed Scopus (92) Google Scholar ,4 Tontisirin N. Muangman S.L. Suz P. et al. Early childhood gender differences in anterior and posterior cerebral blood flow velocity and autoregulation. Pediatrics. 2007; 119: e610-e615 Crossref PubMed Scopus (62) Google Scholar In clinical practice, hypotension is commonly defined in relation to gestational age (GA), and hypotension is common in critically ill neonates. 6 Dilli D. Soylu H. Tekin N. Neonatal hemodynamics and management of hypotension in newborns. Turk Pediatri Ars. 2018; 53: S65-S75 Crossref PubMed Scopus (10) Google Scholar Obtaining normative data for female and male newborns is a requisite for further understanding CBF and cerebral autoregulation and optimizing cerebral perfusion in critically ill neonates. We explored CBF velocity and cerebral autoregulation of the anterior cerebral circulation among healthy term newborns.

Physiological Mechanisms and Significance of Intracranial B Waves.

ObjectiveRecently published studies have described slow spontaneous cerebral blood flow (CBF) and cerebrospinal fluid (CSF) oscillations measured by magnetic resonance imaging (MRI) as potential drivers of brain glymphatic flow, with a similar frequency as intracranial B-waves. Aiming to establish the relationship between these waveforms, we performed additional analysis of frequency and waveform parameters, of our previously published transcranial Doppler (TCD) and intracranial pressure (ICP) recordings of intracranial B waves, to compare to published MRI frequency measurements of CBF and CSF slow oscillations.Patients and MethodsWe analyzed digital recordings of B waves in 29 patients with head injury, including middle cerebral artery (MCA) flow velocity (FV), ICP, end tidal CO2, and arterial blood pressure (ABP). A subset of these recordings demonstrated high B wave activity and was further analyzed for parameters including frequency, interaction, and waveform distribution curve features. These measures were compared to published similar measurements of spontaneous CBF and CSF fluctuations evaluated using MRI.ResultsIn patients with at least 10% amplitude B wave activity, the MCA blood flow velocity oscillations comprising the B waves, had a maximum amplitude at 0.0245 Hz, and time derivative a maximum amplitude at 0.035 Hz. The frequency range of the B waves was between 0.6–2.3 cycles per min (0.011-0.038 Hz), which is in the same range as MRI measured CBF slow oscillations, reported in human volunteers. Waveform asymmetry in MCA velocity and ICP cycles during B waves, was also similar to published MRI measured CBF slow oscillations. Cross-correlation analysis showed equivalent time derivatives of FV vs. ICP in B waves, compared to MRI measured CBF slow oscillations vs. CSF flow fluctuations.ConclusionsThe TCD and ICP recordings of intracranial B waves show a similar frequency range as CBF and CSF flow oscillations measured using MRI, and share other unique morphological wave features. These findings strongly suggest a common physiological mechanism underlying the two classes of phenomena. The slow blood flow and volume oscillations causing intracranial B waves appear to be part of a cascade that may provide a significant driving force for compartmentalized CSF movement and facilitate glymphatic flow.

Cerebral Blood Flow in Healthy Subjects with Different Hypnotizability Scores.

Hypnotizability is a cognitive trait associated with differences in the brachial artery flow-mediated dilatation of individuals with high hypnotizability (highs) and low hypnotizability scores (lows). The study investigated possible hypnotizability-related cerebrovascular differences. Among 24 healthy volunteers, the Stanford Hypnotic Susceptibility Scale Form A identified 13 medium-to-lows (med-lows), 11 medium-to-highs (med-highs), and 1 medium hypnotizable. Hypnotizability did not influence the significant changes produced by the trail making task (TMT), mental arithmetic task (MAT), hyperventilation (HVT), and rebreathing (RBT) on heart rate (HR), arterial blood pressure (ABP), and partial pressure of end-tidal CO2 (PETCO2), but moderated the correlations between the changes occurring during tasks with respect to basal conditions (Δ) in ABP and PETCO2 with middle cerebral artery flow velocity (MCAv). In HVT, med-lows exhibited a significant correlation between ΔMCAv and ΔPETCO2, and med-highs showed a significant correlation between ΔABP and ΔMCAv. Cerebrovascular reactivity (CVR) and conductance (ΔCVCi) were significantly correlated with ΔMCAv only in med-lows during HVT and RBT. For the first time, cerebrovascular reactivity related to hypnotizability was investigated, evidencing different correlations among hemodynamic variables in med-highs and med-lows.

The implementation of transcranial Doppler ultrasonography for preclinical study of migraine.

Transcranial Doppler ultrasonography is used to study intracranial blood flow changes associated with migraine in humans, but whether this method is helpful in preclinical settings is yet unknown. To identify changes in rat intracranial blood flow specific to trigeminovascular activation-a key process in migraine pathophysiology-we measured Doppler indices in the middle cerebral artery and basilar artery before, during, and after dural or somatosensory electrical stimulation. Hemodynamic changes specific to dural stimulation were tested further in separate experiments. After baseline recordings, the animals received cumulative infusions of valproate (100 mg/kg, trice), sumatriptan (0.3, 1, and 3mg/kg), or saline, and dural stimulation with measurement of Doppler indices was repeated every 10 min for 1 h. Several parameters of blood flow in the rat middle cerebral artery underwent alterations specific to trigeminovascular activation. These changes, however, were insensitive to valproate and sumatriptan and diminished over time. These findings question the reliability of blood flow velocity variations in large intracranial vessels as biological markers of migraine-related processes and do not support the idea of using transcranial Doppler ultrasonography for preclinical screening of antimigraine treatments, at least in the model of acute trigeminovascular activation in rats.

Middle cerebral arterial flow redistribution is an indicator for intrauterine fetal compromise in late pregnancy in low-resource settings: A prospective cohort study.

ObjectiveWe aimed to determine the prevalence of abnormal umbilical artery (UA), uterine artery (UtA), middle cerebral artery (MCA) and cerebroplacental ratio (CPR) Doppler, and their relationship with adverse perinatal outcomes in women undergoing routine antenatal care in the third trimester.DesignProspective cohort.SettingKagadi Hospital, Uganda.PopulationNon‐anomalous singleton pregnancies.MethodsWomen underwent an early dating ultrasound and a third‐trimester Doppler scan between 32 and 40 weeks of gestation, from 2018 to 2020. We handled missing data using multiple imputation and analysed the data using descriptive methods and a binary logistic regression model.Main outcome measuresComposite adverse perinatal outcome (CAPO), perinatal death and stillbirth.ResultsWe included 995 women. The mean gestational age at Doppler scan was 36.9 weeks (SD 1.02 weeks) and 88.9% of the women gave birth in a health facility. About 4.4% and 5.6% of the UA pulsatility index (PI) and UtA PI were above the 95th percentile, whereas 16.4% and 10.4% of the MCA PI and CPR were below the fifth percentile, respectively. Low CPR was strongly associated with stillbirth (OR 4.82, 95% CI 1.09–21.30). CPR and MCA PI below the fifth percentile were independently associated with CAPO; the association with MCA PI was stronger in small‐for‐gestational‐age neonates (OR 3.75, 95% CI 1.18–11.88).ConclusionIn late gestation, abnormal UA PI was rare. Fetuses with cerebral blood flow redistribution were at increased risk of stillbirth and perinatal complications. Further studies examining the predictive accuracy and effectiveness of antenatal Doppler ultrasound screening in reducing the risk of perinatal deaths in low‐ and middle‐income countries are warranted.Tweetable abstractBlood flow redistribution to the fetal brain is strongly associated with stillbirths in low‐resource settings.

Abstract TMP80: Intraoperative Blood Flow Changes Predict Angiographic Outcomes After Direct Cerebral Revascularization For Moyamoya Disease

Introduction: Moyamoya Disease (MMD) is a progressive steno-occlusive vasculopathy of the large intracranial vessels precipitating ischemic and hemorrhagic events. Cerebral revascularization is the mainstay of treatment in MMD. Intraoperative measurements of cerebral blood flow following direct intracranial bypass may be performed to quantitatively assess the anastomosis. Objectives: To correlate intraoperative flow parameters in direct cerebral bypass for moyamoya disease to postoperative angiographic and clinical outcomes. Methods: Consecutive patients undergoing direct superficial temporal artery (STA) to middle cerebral artery (MCA) bypass were retrospectively analyzed. Preoperative and 6-month postoperative patient data was collected including presenting symptoms, MRI and angiographic findings, neurological complications, and functional outcome. Intraoperative cerebral blood flow was measured from the donor and recipient arteries using a micro flow probe pre- and post-anastomosis. Results: A total of 50 direct revascularization procedures in 39 patients were analyzed, of which 40 were in females (80%). The mean flow prior to anastomosis in the M4 MCA was +2.2 ± 6.1 ml/minute and +26.8 ± 19.0 ml/min in the STA. Post-anastomosis, the mean flow was -10.9 ± 14.8 ml/min (towards the Sylvian Fissure) in the proximal M4 and +7.9 ± 9.2 ml/min in the distal M4. At 6-month follow-up angiography, the graft was patent in all cases, with 98% demonstrating direct supply. A component of indirect supply was observed in 56% of grafts. Matsushima grade A, B, and C revascularization were obtained in 64%, 20%, and 16% of cases, respectively. Amongst Matsushima grade A patients, low flow was observed in the M4 (mean 1.7 ± 4.8 ml/min) prior to bypass, which became retrograde following bypass, measuring -13.5 ± 16.0 ml/min. Lower post bypass flow was observed in grade B and C patients, with -6.8 ± 13.1 ml/min and -5.6 ± 10.3 ml/min, respectively. Postoperative stroke occurred in one patient, who had a Matsushima grade C. Conclusions: Greater intraoperative retrograde flow in the recipient MCA immediately following anastomosis was observed in patients achieving a higher Matsushima grade.

Relation of middle cerebral artery flow velocity and risk of cognitive decline: A prospective community-based study

ObjectivesHemodynamic parameters measured by the Transcranial Doppler Ultrasound (TCD) are related to cognitive impairment in many cross-sectional studies, but the longitudinal evidence is scarce. In this study, we aim to verify the association between flow velocity of Middle Cerebral Artery (MCA) and the longitudinal cognitive decline in community dwelling older adults. Materials and methodsParticipants were administered TCD examination at the baseline. The Peak Systolic Velocity (PSV), Mean Flow Velocity (MFV), and Pulsatility Index (PI) of MCA segments on left middle (LmMCA), left proximal (LpMCA), right middle (RmMCA), and right proximal (RpMCA) were obtained. Mini-mental state examination (MMSE) were conducted at both baseline and follow-up. ResultsOne hundred and thirteen participants without dementia were followed up for 6.3 years in average. The mean annual rate of decline in the MMSE score was 0.15 (min to max: −1.0 to 1.2). LpMCA PSV (β = −0.0034, r = −0.231, P = 0.022) and LpMCA MFV (β = −0.0049, r = −0.217, P = 0.031) were inversely associated with annual rate of decline in the MMSE score after adjusting for age, gender, education year, APOE ε4, obesity, hypertension, diabetes mellitus, stroke, and coronary heart disease. ConclusionsBlood flow velocity of left proximal MCA was inversely related to global cognitive decline. Cerebral blood flow velocity may impact the cognitive function.

Cardiac Stroke Volume Index Is Associated With Early Neurological Improvement in Acute Ischemic Stroke Patients.

Early neurological improvement as assessed with the NIH stroke scale (NIHSS) at 24 h has been associated with improved long-term functional outcomes following acute ischemic stroke (AIS). Cardiac dysfunction is often present in AIS, but its association with outcomes is incompletely defined. We performed a pilot study to evaluate the association between non-invasively measured cardiac parameters and 24-h neurological improvement in prospectively enrolled patients with suspected AIS who presented within 12 h of symptom-onset and had an initial systolic blood pressure>140 mm Hg. Patients receiving thrombolytic therapy or mechanical thrombectomy were excluded. Non-invasive pulse contour analysis was used to measure mean arterial blood pressure (MAP), cardiac stroke volume index (cSVI), cardiac output (CO) and cardiac index (CI). Transcranial Doppler recorded mean middle cerebral artery flow velocity (MFV). We defined a decrease of 4 NIHSS points or NIHSS ≤ 1 at 24-h as neurological improvement. Of 75 suspected, 38 had confirmed AIS and did not receive reperfusion therapy. Of these, 7/38 (18.4%) had neurological improvement over 24 h. MAP was greater in those without improvement (108, IQR 96–123 mm Hg) vs. those with (89, IQR 73–104 mm Hg). cSVI, CO, and MFV were similar between those without and with improvement: 37.4 (IQR 30.9–47.7) vs. 44.7 (IQR 42.3–55.3) ml/m2; 5.2 (IQR 4.2–6.6) vs. 5.3 (IQR 4.7–6.7) mL/min; and 39.9 (IQR 32.1–45.7) vs. 34.4 (IQR 27.1–49.2) cm/s, respectively. Multivariate analysis found MAP and cSVI as predictors for improvement (OR 0.93, 95%CI 0.85–0.98 and 1.14, 95%CI 1.03–1.31). In this pilot study, cSVI and MAP were associated with 24-h neurological improvement in AIS.

Transcranial Doppler findings in reversible cerebral vasoconstriction syndrome.

Reversible cerebral vasoconstriction syndrome (RCVS) is a syndrome characterized by reversible segmental vasoconstriction of cerebral arteries. Digital subtraction and noninvasive angiograms are typically used to detect vasospasm; however, due to the dynamic nature of RCVS these tests are often negative initially and may need to be repeated multiple times. Transcranial Doppler (TCD) offers many advantages as it is a noninvasive and nonradiating modality. Studies investigating its diagnostic utility for capturing vasospasm and studying temporal evolution of RCVS are limited. We conducted a retrospective analysis on all patients admitted with suspected RCVS from 2009 to 2014 to a single center at Jackson Memorial Hospital. We identified 9 patients (88.9% women, age 46.6 ± 13.5 years) who met diagnostic criteria for RCVS. All patients presented with headache, 5 developed nonaneurysmal subarachnoid hemorrhage, 5 developed ischemic stroke, and 1 developed posterior reversible encephalopathy syndrome. At initial TCD, 8 patients had increased flow velocities in at least one large intracranial artery and ultimately all patients had abnormal middle cerebral artery flow velocity over the course of RCVS. We found that the number of vessels with abnormal velocities increases gradually and peaks between 13 and 14 days after first symptom onset. Finally, mean flow velocity of affected vessels also increases around the same time frame and normalizes at 60 days. In this case series, we found TCD to be useful in detecting vasospasm and monitoring the temporal evolution of RCVS. TCD could be a helpful clinical tool to diagnose and monitor RCVS.

TP10.1.12Personal Protective Equipment impairs pulmonary gas exchange causing systemic hypercapnia-hypoxaemia and cerebral hyperperfusion-induced cephalalgia

Abstract Aims To what extent Personal Protective Equipment (PPE) impacts integrated cardiopulmonary-cerebrovascular function has not been examined. The hypothesis tested was that PPE adversely influences pulmonary gas exchange, resulting in systemic hypercapnic-hypoxaemia and cerebral hyperperfusion-induced cephalalgia. Methods Eight male Higher Surgical Trainees (aged 33 ± 2y) participated in a repeated measures crossover study, completing two-hour laparoscopic simulation tasks, on two separate occasions (separate days), once in standard operating attire, and once in full PPE (including FFP3 mask). Results Following two hours of simulation, full PPE (compared with standard operating attire) was associated with increased FICO2 (7.9% (±0.8%) vs. 7.1% (±1.2%); p = 0.025), decreased FIO2 (16.0% (±0.4%) vs. 16.6% (±0.5%); p = 0.011), and decreased peripheral O2 saturation (95% (± 1%) vs. 98% (±1%); p = 0.001). Headaches were reported by three participants in PPE (Chi2 3.692, p = 0.055), and was associated with increased Middle Cerebral Artery flow velocity; 82 (±4) cm/s, compared with 63 (±9) cm/s in the remaining five participants (p = 0.008). Skin temperature increased by 1.3 °C during simulation in PPE (p = 0.001), with an equal mean insensible fluid loss of 300ml under both conditions (p = 0.049). Conclusions Collectively, these findings highlight the integrated cardiopulmonary-cerebrovascular complications associated with PPE-induced impairment in pulmonary gas exchange. Protective countermeasures should be designed to prevent risk to healthcare staff and patients alike.

Cerebral autoregulation in anoxic brain injury patients treated with targeted temperature management

BackgroundLittle is known about the prevalence of altered CAR in anoxic brain injury and the association with patients’ outcome. We aimed at investigating CAR in cardiac arrest survivors treated by targeted temperature management and its association to outcome.MethodsRetrospective analysis of prospectively collected data. Inclusion criteria: adult cardiac arrest survivors treated by targeted temperature management (TTM). Exclusion criteria: trauma; sepsis, intoxication; acute intra-cranial disease; history of supra-aortic vascular disease; severe hemodynamic instability; cardiac output mechanical support; arterial carbon dioxide partial pressure (PaCO2) > 60 mmHg; arrhythmias; lack of acoustic window. Middle cerebral artery flow velocitiy (FV) was assessed by transcranial Doppler (TCD) once during hypothermia (HT) and once during normothermia (NT). FV and blood pressure (BP) were recorded simultaneously and Mxa calculated (MATLAB). Mxa is the Pearson correlation coefficient between FV and BP. Mxa > 0.3 defined altered CAR. Survival was assessed at hospital discharge. Cerebral Performance Category (CPC) 3–5 assessed 3 months after CA defined unfavorable neurological outcome (UO).ResultsWe included 50 patients (Jan 2015–Dec 2018). All patients had out-of-hospital cardiac arrest, 24 (48%) had initial shockable rhythm. Time to return of spontaneous circulation was 20 [10–35] min. HT (core body temperature 33.7 [33.2–34] °C) lasted for 24 [23–28] h, followed by rewarming and NT (core body temperature: 36.9 [36.6–37.4] °C). Thirty-one (62%) patients did not survive at hospital discharge and 36 (72%) had UO. Mxa was lower during HT than during NT (0.33 [0.11–0.58] vs. 0.58 [0.30–0.83]; p = 0.03). During HT, Mxa did not differ between outcome groups. During NT, Mxa was higher in patients with UO than others (0.63 [0.43–0.83] vs. 0.31 [− 0.01–0.67]; p = 0.03). Mxa differed among CPC values at NT (p = 0.03). Specifically, CPC 2 group had lower Mxa than CPC 3 and 5 groups. At multivariate analysis, initial non-shockable rhythm, high Mxa during NT and highly malignant electroencephalography pattern (HMp) were associated with in-hospital mortality; high Mxa during NT and HMp were associated with UO.ConclusionsCAR is frequently altered in cardiac arrest survivors treated by TTM. Altered CAR during normothermia was independently associated with poor outcome.

Sleep deprivation impairs cognitive performance, alters task-associated cerebral blood flow and decreases cortical neurovascular coupling-related hemodynamic responses

Sleep deprivation (SD) is a common condition and an important health concern. In addition to metabolic and cardiovascular risks, SD associates with decreases in cognitive performance. Neurovascular coupling (NVC, "functional hyperemia") is a critical homeostatic mechanism, which maintains adequate blood supply to the brain during periods of intensive neuronal activity. To determine whether SD alters NVC responses and cognitive performance, cognitive and hemodynamic NVC assessments were conducted prior to and 24 h post-SD in healthy young male individuals (n = 10, 27 ± 3 years old). Cognition was evaluated with a battery of tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Hemodynamic components of NVC were measured by transcranial Doppler sonography (TCD) during cognitive stimulation, dynamic retinal vessel analysis (DVA) during flicker light stimulation, and functional near infrared spectroscopy (fNIRS) during finger tapping motor task. Cognitive assessments revealed impairments in reaction time and sustained attention after 24 h of SD. Functional NIRS analysis revealed that SD significantly altered hemodynamic responses in the prefrontal cortex and somatosensory cortex during a motor task. NVC-related vascular responses measured by DVA and TCD did not change significantly. Interestingly, TCD detected decreased task-associated cerebral blood flow (CBF) in the right middle cerebral artery in sleep deprived participants. Our results demonstrate that 24 h of SD lead to impairments in cognitive performance together with altered CBF and hemodynamic components of cortical NVC responses.

To Study Acute Changes in Brain Oxygenation on MRI in Healthcare Workers Using N95 Mask and PPE Kits for Six Hours a Day.

Background Due to long working hours wearing an N95 mask and PPE kit during the COVID-19 pandemic, the healthcare workers (HCWs) complained of headaches, confusion, and exhaustion. This study was therefore performed to study the changes in brain oxygenation. Aim To compare brain oxygenation in health care workers wearing an N95 mask with a PPE kit versus a three-ply mask during an intensive care setting for 6 hours. Materials and Methods Thirty clinicians and 30 paramedical staff participated in the study. The control (three-ply mask) and subject (N95 mask with PPE) groups included 15 clinicians and 15 paramedical staff. A comparative analysis of brain oxygenation using a 3T magnetic resonance imaging (MRI) machine was performed in these two groups at the beginning and the end of their work shift. Results The mean age of the individuals in the control and subject groups was 30.8 and 30.13 years, respectively. The median value of brain oxygenation in the control and subject groups in the pre-shift was between 33 and 31 and post-shift was 30 and 24. The drop in brain oxygenation in subjects was more than the controls ( p = 0.004) in the post-shift assessments. The cerebral blood flow (CBF) in the bilateral middle cerebral artery (MCA) using arterial spin labeling (ASL) showed a rise in CBF in both groups post-shift as compared with the pre-shift values. The median values of the right and left MCA in the control and subject groups pre-shift were 82.75/83.45 and 89.75/106.65. The post-shift median values of both MCAs of the control and subject groups were 115.65/115.55 and 109.60/119.49. Conclusion MRI-BOLD imaging revealed a significant drop in brain oxygenation in the subject group as compared with the control group. Multiphasic-ASL showed a compensatory rise in CBF in both groups.

Experimental high thoracic spinal cord injury impairs the cardiac and cerebrovascular response to orthostatic challenge in rats.

Spinal cord injury (SCI) impairs the cardiovascular responses to postural challenge, leading to the development of orthostatic hypotension (OH). Here, we apply lower body negative pressure (LBNP) to rodents with high-level SCI to demonstrate the usefulness of LBNP as a model for experimental OH studies, and to explore the effect of simulated OH on cardiovascular and cerebrovascular function following SCI. Male Wistar rats (n = 34) were subjected to a sham or T3-SCI surgery and survived into the chronic period postinjury (i.e., 8 wk). Cardiac function was tracked via ultrasound pre- to post-SCI to demonstrate the clinical utility of our model. At study termination, we conducted left-ventricular (LV) catheterization and insonated the middle cerebral artery to investigate the hemodynamic, cardiac, and cerebrovascular response to a mild dose of LBNP that is sufficient to mimic clinically defined OH in rats with T3-SCI but not sham animals. In response to mimicked OH, there was a greater decline in stroke volume, cardiac output, maximal LV pressure, and blood pressure in SCI compared with sham (P < 0.034), whereas heart rate was increased in sham but decreased in SCI (P < 0.029). SCI animals also had an exaggerated reduction in peak, minimum and mean middle cerebral artery flow, for a given change in blood pressure, in response to LBNP (P < 0.033), implying impaired dynamic cerebral autoregulation. Using a preclinical SCI model of OH, we demonstrate that complete high thoracic SCI impairs the cardiac response to OH and disrupts dynamic cerebral autoregulation.NEW & NOTEWORTHY This is the first use of LBNP to interrogate the cardiac and cerebrovascular responses to simulated OH in a preclinical study of SCI. Here, we demonstrate the utility of our simulated OH model and use it to demonstrate that SCI impairs the cardiac response to simulated OH and disrupts dynamic cerebrovascular autoregulation.

Relation of middle cerebral artery flow velocity and risk of cognitive decline: A prospective community-based study

Hemodynamic parameters measured by the Transcranial Doppler Ultrasound (TCD) are related to cognitive impairment in many cross-sectional studies, but the longitudinal evidence is scarce. This study aimed to verify the association between flow velocity of Middle Cerebral Artery (MCA) and the longitudinal cognitive decline in community dwelling older adults.

Transcranial Doppler study in acute spontaneous intracerebral hemorrhage: The role of pulsatility index.

ObjectivePulsatility index (PI) is a parameter calculated by transcranial Doppler sonography (TCD), which is commonly used for patients with subarachnoid hemorrhage or ischemic stroke. However, we performed a retrospective analysis of patients with acute spontaneous intracerebral hemorrhage (ICH) to assess the function of TCD, particularly the PI.MethodsThis study involved a total of 46 patients with acute ICH who received treatment at a single center between May 2013 and December 2014. Medical records of baseline characteristics, except for the modified Rankin scale, were obtained at initial evaluation in the emergency room, and TCD was used to calculate middle cerebral artery flow velocity (MFV) and PI at admission (baseline), 24 h, and 7 days. The PI and MFV values on the affected middle cerebral artery were compared with those on the contralateral side. Linear regression analysis was used for statistical analyses (SPSS 21.0, IBM Corp., Armonk, NY, USA).ResultsStatistical analysis indicated that sex, age, Glasgow coma scale, intraventricular hemorrhage, and hematoma size were not correlated with PI (p＞0.05); however, only PI was positively correlated with functional outcome at 6 months after treatment (R=0.846, p=0.002).ConclusionsThese results provide evidence that the parameter of PI is an independent determinant prognostic factor in acute spontaneous ICH. Further research is needed to investigate the influence of cerebral blood flow dynamics on a larger, more controlled, and more randomized basis.