Middle Cerebral Artery Flow Velocity Research Articles

Prognostic Significance of Sentinel Headache Preceding Aneurysmal Subarachnoid Hemorrhage

Sentinel headache (SH) is often assumed to portend an increased risk of delayed cerebral ischemia (DCI) and aneurysm rebleeding. This study aimed to re-evaluate the associations between SH and aneurysm rebleeding, DCI, and outcome after SAH. We retrospectively analyzed 1102 patients with spontaneous SAH and available data regarding history of SH who were enrolled in the Columbia University SAH Outcomes Project between 1996 and 2009. Patients were asked whether they had experienced any episodes of acute, sudden-onset severe headache in the 2 weeks preceding the most recent bleeding event. DCI was defined as neurologic deterioration, infarction, or both due to vasospasm. Rebleeding was defined as the appearance of new hemorrhage on computed tomography. Outcome was assessed at 3 months by telephone interview using the modified Rankin Scale. SH was reported in 152 (14%) of 1102 patients. There were no significant differences between patients with and without SH with regard to admission Hunt-Hess grade or modified Fisher Scale. There was also no difference with regard to the frequency of aneurysm rebleeding (10% vs. 8%, P= 0.42), DCI (18% vs, 20%, P= 0.64), moderate-or-severe angiographic vasospasm on follow-up angiography (51% vs. 56%, P= 0.43), highest recorded mean middle cerebral artery flow velocity on transcranial Doppler (134 versus 128 cm/s, P= 0.30), or the distribution of modified Rankin Scale scores at 3 months. A history of sentinel headache before the clinical diagnosis of SAH does not imply an increased risk of DCI or further rebleeding, and carries no prognostic significance.

Effect of dexmedetomidine on dynamic cerebral autoregulation and carbon dioxide reactivity during sevoflurane anesthesia in healthy patients.

BackgroundThere are conflicting opinions on the effect of dexmedetomidine on cerebral autoregulation. This study assessed its effect on dynamic cerebral autoregulation (dCA) using a transcranial Doppler (TCD).MethodsThirty American Society of Anesthesiologists physical status I and II patients between 18 and 60 years, who underwent lumbar spine surgery, received infusions of dexmedetomidine (Group D) or normal saline (Group C), followed by anesthesia with propofol and fentanyl, and maintenance with oxygen, nitrous oxide and sevoflurane. After five minutes of normocapnic ventilation and stable bispectral index value (BIS) of 40–50, the right middle cerebral artery flow velocity (MCAFV) was recorded with TCD. The transient hyperemic response (THR) test was performed by compressing the right common carotid artery for 5–7 seconds. The lungs were hyperventilated to test carbon dioxide (CO2) reactivity. Hemodynamic parameters, arterial CO2 tension, pulse oximetry (SpO2), MCAFV and BIS were measured before and after hyperventilation. Dexmedetomidine infusion was discontinued ten minutes before skin-closure. Time to recovery and extubation, modified Aldrete score, and emergence agitation were recorded.ResultsDemographic parameters, durations of surgery and anesthesia, THR ratio (Group D: 1.26 ± 0.11 vs. Group C: 1.23 ± 0.04; P = 0.357), relative CO2 reactivity (Group D: 1.19 ± 0.34 %/mmHg vs. Group C: 1.23 ± 0.25 %/mmHg; P = 0.547), blood pressure, SpO2, BIS, MCAFV, time to recovery, time to extubation and modified Aldrete scores were comparable.ConclusionsDexmedetomidine administration does not impair dCA and CO2 reactivity in patients undergoing spine surgery under sevoflurane anesthesia.

Study protocol for SFX-01 after subarachnoid haemorrhage (SAS): a multicentre randomised double-blinded, placebo controlled trial

IntroductionSubarachnoid haemorrhage (SAH) from a ruptured cerebral aneurysm carries high morbidity and mortality. Despite huge advances in techniques to secure the aneurysm, there has been little progress in the treatment...

27 Cerebral Autoregulation Associated with Falls in Older Persons with Orthostatic Hypotension?

Abstract Background It is considered well-established that orthostatic hypotension (OH) is associated with falls, population-based studies have found that a large proportion of community-dwelling older adults fulfill the criteria for OH without experiencing falls. It is therefore postulated that older individuals with OH may only experience fall if cerebral autoregulation, which is the mechanism by which the brain blood flow is maintained constant through a autoregulatory range, is impaired. Objective To evaluate the relationship between cerebral autoregulation and OH in older individuals with and without a history of falls. Method Individuals aged 3 60 years were recruited from medical clinics, by word of mouth, and from existing research registries. Baseline sociodemographics, detailed medical history and medication history were obtained. Bilateral middle cerebral artery (MCA) blood flow were recorded using transcranial Doppler ultrasound (TCD) synchronized with non-invasive continuous blood pressure and ECG recordings. Synchronized brain blood flow signals, heart trace and blood pressure signals were first recorded during 10 minutes’ supine rest. Participants were then be asked to perform a standard set of mathematical calculations, a Valsalva maneuver and to stand up from a seated position. Results 36 participants have been evaluated to date (13 fallers, 23 non-Fallers). There is no statistically significant difference in gender, ethnicity or height and weight between groups. Fluctuations in MCA flow velocity were observed with spontaneous fluctuations in blood pressure at rest and with induced blood pressure changes during the challenge maneuvers. Visual inspection of the signals obtained suggested that changes in MCA flow velocity were more marked among fallers and non-fallers. Conclusion Synchronization of cerebral blood flow and continuous blood pressure signals opens up numerous new possibilities in research and clinical practice. Our preliminary findings suggest that cerebral autoregulation does play a role in determining the presence of symptomats in older individuals with OH.

Acute symptomatic extracranial internal carotid occlusion - natural course and clinical impact.

Background: To assess the vascular and clinical course of acute symptomatic extracranial internal carotid artery (ICA) occlusion. Patients and methods: Patients with an acute ischemic event in the anterior circulation and corresponding extracranial ICA occlusion at CT angiography and/or color-coded duplex sonography underwent recurrent duplex follow-up for detection of spontaneous recanalization. Stroke recurrence and functional outcome 4.5 months after the ischemic index event assessed by modified Rankin scale served as secondary outcome parameters. Results: 133 patients (91 men, mean age 62.3years, SD 10.8) demonstrated symptomatic occlusion of the extracranial ICA with open intracranial ICA and open middle cerebral artery and were followed-up for spontaneous recanalization. Twenty-eight recanalized spontaneously, 25 to high-grade focal stenosis within 12 days, revealing an early cumulative recanalization rate of 23%. Detection of recanalization was independently associated with de novo dual anti-platelet therapy (adjusted odds ratio [OR], 3.24; 95% confidence interval [CI], 1.34 to 7.80). Ischemic recurrence occurred in 16 patients, of which 10 deemed to be embolic and 5 hemodynamic. Spontaneous ICA recanalization and an exhausted cerebrovascular reserve in the hemisphere distal to the occluded ICA were both independently associated with the occurrence of a recurrent ischemic event at Cox regression. An increasing NIHSS score at admission, a decreasing middle cerebral artery flow velocity and an ischemic recurrence independently predicted poor outcome (modified Rankin scale 3 to 6) in multivariate analysis. Conclusions: Acute symptomatic extracranial ICA occlusion is an unstable condition with frequent spontaneous recanalization to severe stenosis and early embolic stroke recurrence, demanding appropriate prevention especially in those patients with only mild deficit.

Reduced cerebrovascular and cardioventilatory responses to intermittent hypoxia in elderly

BackgroundThe impact of aging on cerebrovascular function and tissue oxygenation during graded hypoxemia is incompletely known. This study compared the age effect on these variables during cyclic hypoxemia-reoxygenation. MethodsHypoxia-induced changes in arterial (SaO2) and cerebral tissue (ScO2) O2 saturation, middle cerebral arterial flow velocity (VMCA), estimated cerebral vascular conductance (CVC), heart rate (HR) and ventilation were compared between 12 elderly (71 ± 2 yr, 7 women) and 13 young (24 ± 3 yr, 5 women) adults during the first and fifth 5-min exposures to 10% O2. ResultsAlthough pre-hypoxia SaO2 did not differ between the groups, ScO2 was lower (P < 0.05) in the elderly (68.4 ± 1.2%) than young (73.8 ± 0.9%) adults, commensurate with a lower resting VMCA (P < 0.05). SaO2 fell less sharply (P < 0.05) in the elderly subjects during the first and fifth hypoxia exposures. Moreover, the responses of ScO2, VMCA, CVC, HR and breathing frequency to hypoxia were attenuated in the elderly subjects. Systolic and diastolic arterial pressures fell by 2–6 mmHg during hypoxia in both young and elderly. Thus, hypoxemia developed more gradually in elderly than young adults during normobaric hypoxia, concordant with a reduced metabolic demand in the elderly. ConclusionsThe elderly adults safely tolerated cyclic, moderate hypoxemia which lowered SaO2 by 20–25%, despite dampening of cerebrovascular and cardiac responses to hypoxemia.

Hemodynamic Surveillance of Unilateral Carotid Artery Stenting in Patients With or Without Contralateral Carotid Occlusion by TCD/TCCD in the Early Stage Following Procedure.

Objective: To evaluate the cerebral hemodynamic variations in patients with unilateral carotid artery stenosis and contralateral carotid occlusion (CCO) in hours following carotid artery stenting (CAS) by transcranial Doppler (TCD) or transcranial color-code Doppler (TCCD).Methods: Sixty-five consecutive patients who underwent unilateral CAS were enrolled. Among them, 14 patients had ipsilateral severe stenosis and CCO (CCO group) while the other 51 patients had only unilateral severe carotid stenosis without CCO (UCS group). All patients underwent TCD or TCCD monitoring before, at 1 and 3 h after CAS. We monitored bilateral middle cerebral artery (MCA) peak systolic velocity (PSV), pulsatility index (PI), and blood pressure (BP), and compared that data between two groups.Results: In UCS group, ipsilateral MCA PSV increased relative to baseline at 1 h (96 ± 30 vs. 85 ± 26 cm/s, 15%, P < 0.001) and 3 h (97 ± 29 vs. 85 ± 26 cm/s, 17%, P < 0.001) following CAS. Significant PI increases were observed at 1 and 3 h following CAS on the ipsilateral side. In CCO group, ipsilateral MCA PSV increased relative to baseline at 1 h (111 ± 30 vs. 83 ± 26 cm/s, 35%, P < 0.001) and 3 h (107 ± 28 vs. 83 ± 26 cm/s, 32%, P <0.001) following CAS. The magnitude of ipsilateral MCA PSV increase was significantly higher in CCO group compared with UCS group at 1 h (P = 0.002) and 3 h (P = 0.024) following CAS, while BP similarly decreased between the two groups. On the contralateral side, significant MCA PSV increases were observed following CAS in CCO group but not in UCS group. Bilateral MCA PSV increases were higher in patients with a stenosis degree of ≥90% than in patients with stenosis degree of 70–89% only in CCO group.Conclusion: The ipsilateral MCA PSV and PI increase moderately in the initial hours after unilateral CAS in patients without CCO. In patients with CCO, the ipsilateral, and contralateral MCA PSV increase significantly in the early stage following CAS. CCO is a factor of the increased blood flow velocity in ipsilateral MCA after unilateral CAS.

Ultrasound measurements versus invasive intracranial pressure measurement method in patients with brain injury: a retrospective study

BackgroundThe invasive method for intracranial pressure measurement is ‘gold standard’ but not always feasible because the intraventricular catheter/ intraparenchymal micro transducer used in the measurement of intracranial pressure measurement may cause complications. Imaging modalities with clinical examination protocol have a lack of specificity and accuracy. The objective of the study was to compare the accuracy of diagnostic parameters of ultrasound measurements in patients with brain injury underwent invasive intracranial pressure measurement method.MethodsData of invasive intracranial pressure measurement method and ultrasound measurements of 185 patients with brain injury who required admission diagnosis were included in the analysis. Pearson correlation was tested for diagnostic parameters. Logistical regression analysis was performed for diagnostic parameters of death patients to evaluate independent parameter of mortality.ResultsStraight sinus flow velocities, middle cerebral artery flow velocities, and optic nerve sheath diameter were correlated with intracranial pressure (p < 0.0001 for all). Arterial blood pressure (p = 0.127) and middle cerebral artery pulsatility index (p = 0.06) were not correlated with intracranial pressure. A total of 47 patients died during the study period. Intracranial pressure (p = 0.015) and optic nerve sheath diameter (p = 0.035) were found to be independent predictor of mortality.ConclusionsUltrasound measurement especially optic nerve sheath diameter can be successfully used instead of invasive intracranial pressure measurement method in patients with brain injury.Level of evidenceIII.

Prediction of syncope with nonlinear dynamic analysis during head-up tilt in vasovagal syncope patients

To quantify the relationship between cerebral blood flow velocity and peripheral blood pressure during hypotension period, aiming to predict the brain hypotension before symptomatic occurrence. Twenty vasovagal syncope (VVS) patients who had a previous clinical history were selected in groups and 20 pair-matched control subjects underwent 70° tilt-up test. The subjects remained supine for 30 minutes before recordings when Doppler probes, electrodes and Finapres device were prepared. After continuous baseline recordings for 10 min, the subjects underwent head up tilt (HUT) test (70°), and were standing upright for 30 minutes or until syncope was imminent. For ethical reasons, the subjects were turned back to supine position immediately after SBP dropped to ≥20 mmHg, when their consciousness persisted. The point of syncope was synchronized for all the subjects by the point SBP reached the minima. Their beat-to-beat blood pressures (BP) were recorded continuously and bilateral middle cerebral artery (MCA) flow velocities were obtained with two 2 MHz Doppler probes from a transcranial Doppler ultrasonography (TCD) system. A nonlinear dynamic method--multimodal pressure flow (MMPF) analysis was introduced to access cerebral autoregulation during different time intervals. We introduced a new indicator--syncope index (SI), which was extracted from blood flow velocity (BFV) signal to evaluate the variation of cerebral vascular tension, and could reflect the deepness of dicrotic notch in BFV signal. Compared with the syncope index of the baseline value at the beginning of the tilt test, SI in VVS group showed significantly lower when the VVS occurred (0.16±0.10 vs.0.27±0.10,P<0.01),while there was no significant difference in syncope index between the control group at the end of the tilt test and the baseline value at the beginning of the tilt test. For those VVS patients, pulse index and resistance index had no significant change. Syncope index decreased significantly 3 minutes before the point of syncope (0.23±0.07 vs.0.29±0.07,P<0.01). Dynamic regulation is exhausted when vasovagal syncope occurred. Tension decrease of small vessels could have some relationship with loss of the cerebral autoregulation capability. The proposed syncope index could be a useful parameter in predicting syncope of VVS patients since it decreased significantly up to 3 minutes earlier from the point of syncope.

Effective Cerebral Perfusion Pressure: Does the Estimation Method Make a Difference?

The effective cerebral perfusion pressure (CPPe), zero-flow pressure (ZFP), and resistance area product (RAP) are important determinants of cerebral blood flow. ZFP and RAP are usually estimated by linear regression analysis of pressure-velocity relationships of the middle cerebral artery. The aim of this study was to validate 4 other estimation methods against the standard linear regression method. In a previous study, electroencephalography, arterial blood pressure, and middle cerebral artery flow velocity were measured in patients during internal cardioverter defibrillator implantation procedures to determine the electroencephalography frequency ranges that represent ischemic changes during periods of circulatory arrest. In this secondary analysis, arterial blood pressure and middle cerebral artery flow velocity were used to estimate CPPe, ZFP, and RAP by 4 different methods-the 3-point intercept calculation (LR3, systolic/mean/diastolic) and methods described by Czosnyka (systolic/diastolic), Belford (mean/diastolic), and Schmidt (systolic/diastolic)-and compare them with the reference linear regression method. CPPe was calculated as the difference between mean arterial pressure and ZFP. The primary endpoint was the difference, correlation, and agreement of these differently estimated CPPe measurements. In total, 174 measurements in 35 patients were collected under steady-state conditions before the first circulatory arrest phase during internal cardioverter defibrillator testing. CPPe, ZFP, and RAP measurements based on the 3-point intercept and Czosnyka calculation methods showed small mean differences, good agreement, low percentage errors, and excellent correlation when compared with the reference method. Agreement and correlation were moderate for the Belford method and unsatisfactory for the Schmidt method. CPPe, ZFP, and RAP measurements based on 2 alternative calculation methods are comparable to the linear regression reference method.

Microbleeds of Lacunar Infarction and Middle Cerebral Artery Flow Velocity of Branch Atheromatous Disease Are Essential Factors of Stroke Etiology

Background: Although subcortical infarction patients sometimes show larger infarction size than the definition of small vessel occlusion (SVO), there are no specific predictors of larger size. The aim of this study was to identify the factors, including magnetic resonance imaging (MRI) and ultrasonographic parameters, to predict larger subcortical infarction. Methods: Consecutive patients with acute supratentorial subcortical infarction were studied. Patients were classified into 2 groups (L: larger group, ≥15 mm and ≥3 slices; S: smaller group, SVO based on the TOAST classification). Clinical information, MRI findings including the presence of microbleeds, and ultrasonography findings were evaluated and compared between the 2 groups. Results: A total of 120 patients (81 male, mean 67 years old) were enrolled. The L group included 22 patients (18%), and the S group had 98 patients (82%). On neuroimaging, microbleeds were seen less frequently in the L group than in the S group (23 vs. 53%, p = 0.017), and peak systolic velocity (PSV) by transcranial color-coded sonography was faster in the L group than in the S group (121 ± 39.8 vs. 83.4 ± 25.4 cm/s, p = 0.002). On multivariate logistic regression analysis, no evidence of microbleeds (OR 4.4, 95% CI 1.41–13.68, p = 0.011) and PSV over 92 cm/s (OR 3.1, 95% CI 1.007–9.719, p = 0.049) were found to be independently associated with larger size. Conclusion: Microbleeds is related to smaller size and middle cerebral artery PSV > 92 cm/s indicate larger size in supratentorial subcortical infarcts.

Transfusion requirements after head trauma: a randomized feasibility controlled trial

BackgroundAnemia is frequent among patients with traumatic brain injury (TBI) and is associated with an increased risk of poor outcome. The optimal hemoglobin concentration to trigger red blood cell (RBC) transfusion in patients with TBI is not clearly defined.MethodsAll eligible consecutive adult patients admitted to the intensive care unit (ICU) with moderate or severe TBI were randomized to a “restrictive” (hemoglobin transfusion threshold of 7 g/dL), or a “liberal” (threshold 9 g/dL) transfusion strategy. The transfusion strategy was continued for up to 14 days or until ICU discharge. The primary outcome was the mean difference in hemoglobin between groups. Secondary outcomes included transfusion requirements, intracranial pressure management, cerebral hemodynamics, length of stay, mortality and 6-month neurological outcome.ResultsA total of 44 patients were randomized, 21 patients to the liberal group and 23 to the restrictive group. There were no baseline differences between the groups. The mean hemoglobin concentrations during the 14-day period were 8.4 ± 1.0 and 9.3 ± 1.3 (p < 0.01) in the restrictive and liberal groups, respectively. Fewer RBC units were administered in the restrictive than in the liberal group (35 vs. 66, p = 0.02). There was negative correlation (r = − 0.265, p < 0.01) between hemoglobin concentration and middle cerebral artery flow velocity as evaluated by transcranial Doppler ultrasound and the incidence of post-traumatic vasospasm was significantly lower in the liberal strategy group (4/21, 3% vs. 15/23, 65%; p < 0.01). Hospital mortality was higher in the restrictive than in the liberal group (7/23 vs. 1/21; p = 0.048) and the liberal group tended to have a better neurological status at 6 months (p = 0.06).ConclusionsThe trial reached feasibility criteria. The restrictive group had lower hemoglobin concentrations and received fewer RBC transfusions. Hospital mortality was lower and neurological status at 6 months favored the liberal group.Trial registrationClinicalTrials.gov, NCT02203292. Registered on 29 July 2014.

Factors related to improvement of cerebrovascular reserve after superficial temporal artery to middle cerebral artery anastomosis for patients with atherosclerotic steno-occlusive disease.

This study aimed to investigate factors related to improvement of hemodynamics and evaluated the usefulness of intraoperative Doppler for predicting postoperative hemodynamics in patients with cerebrovascular atherosclerotic steno-occlusive disease (CASD) of the internal carotid artery (ICA) or middle cerebral artery (MCA) who were treated with extracranial-intracranial (EC-IC) bypass surgery. Forty-eight patients with CASD of the ICA or MCA who were treated by superficial temporal artery to middle cerebral artery bypass with a follow-up longer than 12months were enrolled. Repeated transient ischemic attack or completed ischemic stroke was observed under optimal medical therapy in all patients. Intraoperative blood flow velocity of the MCA was evaluated by a Doppler flowmeter. Cerebral blood flow and cerebrovascular reserve (CVR) were evaluated using N-isopropyl-[123I] p-iodoamphetamine (IMP) single photon emission computed tomography (SPECT) preoperatively and 3months after surgery. Imaging and clinical data were retrospectively reviewed. CVR was significantly increased postoperatively (p = 0.03). One year after the operation, two (4.2%) patients developed cerebral infarction. The change in MCA flow velocity just after anastomosis compared with pre-anastomosis proximal and distal of the anastomosis site was a median of 3.0 and 2.6 times, respectively. However, there was no significant association between changes in intraoperative MCA flow velocity and postoperative CVR. Multivariate analysis showed that the presence of a lower estimated glomerular filtration rate (eGFR) was an independent risk factor for a decrease in CVR (p = 0.036). A higher eGFR might have prognostic value for improvement in CVR after EC-IC bypass surgery in patients with CASD and misery perfusion.

WM1-2 SFX-01 after subarachnoid haemorrhage: protocol of a multi-centre, phase II, double-blinded, randomised controlled trial

ObjectivesTo assess the safety and efficacy of SFX-01 after subarachnoid haemorrhage.DesignSFX-01 is a synthetic agent that contains sulforaphane that has been shown to be neuroprotective in animal models of subarachnoid haemorrhage. This is a phase II double-bilinded, placebo-controlled randomised clinical trial.SubjectsTarget of 90 patients with fisher 3 or 4 subarachnoid haemorrhage.MethodsPatients admitted to the three recruiting centres within 48 hours of ictus will be randomly allocated to placebo or SFX-01. The randomisation is stratified into WFNS 1–3 or 4–5. Participants will receive the trial medication in a capsule format twice-daily for 28 days. Patients will have transcranial dopplers (TCD) on alternate daily basis for at least 7 days. The maximum mean MCA flow velocity as well as safety are the two primary end-points. All patients will have paired blood and CSF taken at day 7 either through an LP or via EVD sampling. Follow-ups are performed at day 28, 3 months and 6 months which include safety bloods, functional questionnaires, mRS, GOSE and MRI.Results64 (71% of the target) patients have been enrolled. 35 patients have completed the study. Statistical analysis of the TCD data will be performed at the end of the trial. The mortality is at 9.5% (6). DSMB have met twice since the start of the trial and there have been no safety concerns.ConclusionsThe trial is recruiting on the planned trajectory and at this rate we are projected to complete the trial by the end of the year.

The influence of microgravity on cerebral blood flow and electrocortical activity.

Changes in gravity conditions have previously been reported to influence brain hemodynamics as well as neuronal activity. This paper attempts to identify a possible link between changes in brain blood flow and neuronal activity during microgravity. Middle cerebral artery flow velocity (MCAv) was measured using Doppler ultrasound. Brain cortical activity (i.e., cortical current density) was measured using electroencephalography. Finger blood pressure was recorded and exported to generate beat-by-beat systolic (SBP), diastolic (DBP) and mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), and cerebrovascular conductance index (CVCi). Seventeen participants were evaluated under normal gravity conditions and microgravity conditions, during 15 bouts of 22-s intervals of weightlessness during a parabolic flight. Although MAP decreased and CO increased, MCAv remained unchanged in the microgravity condition. CVCi as the quotient of MCAv and MAP increased in microgravity. Cortical current density showed a global decrease. Our data support earlier data reporting a decrease in the amplitude of event-related potentials recorded during microgravity. However, the general decrease in neural excitability in microgravity seems not to be dependent on hemodynamic changes.

Cerebrovascular Physiology During Pediatric Extracorporeal Membrane Oxygenation: A Multicenter Study Using Transcranial Doppler Ultrasonography*

To explore changes to expected, age-related transcranial Doppler ultrasound variables during pediatric extracorporeal membrane oxygenation. Prospective, observational, multicenter study. Tertiary care PICUs. Children 1 day to 18 years old requiring veno arterial extracorporeal membrane oxygenation. Participants underwent daily transcranial Doppler ultrasound measurement of bilateral middle cerebral artery flow velocities. Acute neurologic injury was diagnosed if seizures, cerebral hemorrhage, or diffuse cerebral ischemia was detected. Fifty-two children were enrolled and analyzed. In the 44 children without acute neurologic injury, there was a significant reduction in systolic flow velocity and mean flow velocity compared with predicted values over time (F [8, 434] = 60.44; p ≤ 0.0001, and F [8, 434] = 17.61; p ≤ 0.0001). Middle cerebral artery systolic flow velocity was lower than predicted on extracorporeal membrane oxygenation days 1-5, and mean flow velocity was lower than predicted on extracorporeal membrane oxygenation days 1-3. In the six infants less than 90 days old suffering diffuse cerebral ischemia, middle cerebral artery systolic flow velocity, mean flow velocity, and diastolic flow velocity from extracorporeal membrane oxygenation days 1-9 were not significantly different when compared with children of similar age in the cohort that did not suffer acute neurologic injury (systolic flow velocity F [8, 52] = 0.6659; p = 0.07 and diastolic flow velocity F [8, 52] = 1.4; p = 0.21 and mean flow velocity F [8, 52] = 1.93; p = 0.07). Pulsatility index was higher in these infants over time than children of similar age in the cohort on extracorporeal membrane oxygenation that did not suffer acute neurologic injury (F [8, 52] = 3.1; p = 0.006). No patient in the study experienced cerebral hemorrhage. Flow velocities in the middle cerebral arteries of children requiring extracorporeal membrane oxygenation are significantly lower than published normative values for critically ill, mechanically ventilated, sedated children. Significant differences in measured systolic flow velocity, diastolic flow velocity, and mean flow velocity were not identified in children suffering ischemic injury compared with those who did not. However, increased pulsatility index may be a marker for ischemic injury in young infants on extracorporeal membrane oxygenation.

Sex differences in cerebral autoregulation are unaffected by menstrual cycle phase in young, healthy women.

Sex is known to affect the prevalence of conditions such as stroke. However, effects of sex on cerebral blood flow regulation are still not well understood. Critical to this understanding is how fluctuations in hormones across the menstrual cycle affect cerebral autoregulation. We measured autoregulation in the early follicular, late follicular, and midluteal phases during spontaneous and induced blood pressure oscillations in 26 young, healthy individuals (13 women and 13 men, age: 26 ± 4 yr). Men participated three times, ~1-3 wk apart. Beat-by-beat blood pressure, heart rate, end-tidal CO2, and transcranial Doppler ultrasonography of the middle (MCA) and anterior (ACA) cerebral arteries were obtained. We did not find a difference in cerebral autoregulation across the menstrual cycle in women but found significantly improved autoregulation in the MCA and ACA of women compared with men. Women demonstrated significantly lower MCA gain (0.97 ± 0.13 vs. 1.17 ± 0.14%/mmHg, P = 0.001), higher MCA phase (46.1 ± 12.6 vs. 35.8 ± 7.9°, P = 0.019), and higher ACA phase (40.5 ± 10.8 vs 31.5 ± 8.5°, P = 0.040) during repeated squat-to-stand maneuvers. Women also had lower MCA gain (1.50 ± 0.11 vs. 1.72 ± 0.30%/mmHg, P = 0.029) during spontaneous fluctuations in pressure while standing and less of a decrease in MCA flow velocity (-18.7 ± 2.7 vs. -23.2 ± 6.0%, P = 0.014) during sit-to-stand maneuvers. Our results suggest that young women have improved cerebral autoregulation compared with young men regardless of menstrual cycle phase and that autoregulation is relatively robust to acute fluctuations in female sex hormones. NEW & NOTEWORTHY This is the first study to investigate thoroughly the effects of menstrual cycle phase and sex differences in cerebral autoregulation in young, healthy individuals. Cerebral autoregulation was unaffected by menstrual cycle phase during both repeated squat-to-stand and sit-to-stand maneuvers. However, women demonstrated significantly improved cerebral autoregulation in the middle and anterior cerebral arteries, suggesting women were able to maintain cerebral blood flow during changes in blood pressure more efficiently than men.

The influence of propofol on middle cerebral artery flow velocity (VMCA) in patients with unruptured intracranial aneurysms during induction of general anaesthesia.

The estimated prevalence of unruptured intracranial aneurysms is 3%. Standard monitoring does not enable one to assess the influence of anaesthetics on the factors determining intracranial homeostasis. Thanks to transcranial Doppler ultrasonography, middle cerebral artery flow velocity (VMCA), reflecting cerebral blood flow, can be measured. The aim of the study was to assess the effects of propofol on intracranial homeostasis in patients with unruptured intracranial aneurysms during the induction of anaesthesia based on VMCA changes. The study encompassed 21 patients (group II) anaesthetised for elective craniotomy due to unruptured intracranial aneurysms. The control group (group I) included 21 patients who underwent discoidectomy. VMCA, as well as HR, MAP, etCO2, and SpO2 were monitored at the following time points: T0 — onset of study; T1 — after 1 minute; T2 — onset of preoxygenation; T3 — after 1 minute of preoxygenation; T4 — administration of fentanyl; T5 — 1 minute after fentanyl; T6 — administration of propofol; T7 — 1 minute after propofol; T8 — intubation; T9 — 1 minute after intubation; T10 — 2 minutes after intubation. In both groups, no changes in mean HR, etCO2 and SpO2 were observed at the successive time points of observation. In groups I and II, an MAP decrease between T6 and T7 and an MAP increase between T7 and T9 were noted. There were no intergroup differences in mean values of MAP at the times of observation. In both groups and bilaterally, a VMCA decrease was recorded between T6 and T7 and an increase between T7 and T8. There were no intergroup differences in mean values of VMCA at the times of observation. In both groups, a weak correlation between VMCA and MAP changes was found bilaterally. Propofol depresses the cerebral circulation during the induction of anaesthesia. The presence of an unruptured aneurysm does not affect the reactivity of the cerebral vessels during the induction of anaesthesia with propofol.

Non-invasive evaluation of cerebral hemodynamic and intracranial pressure in pediatric neuroinfections

The study of intracranial pressure (eICP), cerebral perfusion pressure (eCPP), cerebral blood flow index (CFI), zero flow pressure (ZFP) in 49 children hospitalized in the intensive care unit with severe course of neuroinfections was carried out. The level of consciousness was determined by the Glasgow pediatric scale. Monitoring of central and peripheral hemodynamics (ECG, heart rate, systolic, diastolic and mean blood pressure, and cardiac output), pulse oximetry, capnography, hemoglobin, hematocrit, total protein, urea, creatinine, lactate, glucose and serum electrolytes was done. An ultrasound scanner was used to perform ultrasound duplex scanning of blood flow in the left and middle cerebral artery (MCA), measuring maximum, minimum and average blood flow velocities, pulsation index (PI), and resistance index (RI). Based on the formulae of Edouard et al. indicators of eCPP, ZFP, CFI, eICP were calculated. The eSCP was also determined by the formulae of Kligenchöfer et al. and Bellner et al. All patients were divided into group I with RI &gt; 1.3 and group II with RI &lt; 1.3. It was found that eCPP in the group I was significantly less (29.5 ± 1.3 mm Hg) than in the II group (41.6 ± 1.7 mm Hg). Despite the lack of a reliable difference in blood pressure between groups I and II, the difference in eCPP was found due to a significant difference in eICP 34.6 ± 1.4 and 27.6 ± 0.89 mm Hg in I and II groups respectively. ZFP in group I was significantly higher than in group II. The indexes of the Glasgow coma scale was significantly lower in group I and 7.8 ± 0.6 points. There were observed direct moderate correlations between systolic blood pressure, cardiac output and eSRP and CFI, presumably associated with a loss of autoregulation. CFI in the group I was lower than in the group II. Thus, non-invasive examination of cerebral flow in MCA by duplex sonography revealed that PI &gt; 1.3 is an informative marker of intracranial hypertension and reduction of cerebral perfusion, which is common in children with neuroinfections. To determine the eSRP and CFI it is advisable to use the formula of Edouard et al. and to determine the eICP the formula of Kligenchöfer et al. The obtained data can be useful for objectifying the severity of the condition, predicting the outcomes of neuroinfections, choosing the directions of intensive care and evaluating its effectiveness.

Cerebrovascular risks with rapid blood pressure lowering in the absence of hypertensive emergency

Study objectiveIn the Emergency Department (ED) setting, clinicians commonly treat severely elevated blood pressure (BP) despite the absence of evidence supporting this practice. We sought to determine if this rapid reduction of severely elevated BP in the ED has negative cerebrovascular effects. MethodsThis was a prospective quasi-experimental study occurring in an academic emergency department. The study was inclusive of patients with a systolic BP (SBP) > 180 mm Hg for whom the treating clinicians ordered intensive BP lowering with intravenous or short-acting oral agents. We excluded patients with clinical evidence of hypertensive emergency. We assessed cerebrovascular effects with measurements of middle cerebral artery flow velocities and any clinical neurological deterioration. ResultsThere were 39 patients, predominantly African American (90%) and male (67%) and with a mean age of 50 years. The mean pre-treatment SBP was 210 ± 26 mm Hg. The mean change in SBP was −38 mm Hg (95% CI −49 to −27) mm Hg. The average change in cerebral mean flow velocity was −5 (95% CI −7 to −2) cm/s, representing a −9% (95% CI −14% to −4%) change. Two patients (5.1%, 95% CI 0.52–16.9%) had an adverse neurological event. ConclusionWhile this small cohort did not find an overall substantial change in cerebral blood flow, it demonstrated adverse cerebrovascular effects from rapid BP reduction in the emergency setting.