Cerebral Artery Mean Flow Velocity Research Articles

Efeitos do sulfato de magnésio e da milrinona sobre o vasoespasmo cerebral após hemorragia subaracnoidea por aneurisma: estudo randômico

BackgroundAneurysmal subarachnoid hemorrhage is an important cause of premature death and disability worldwide. Magnesium sulphate is shown to have a neuroprotective effect and it reverses cerebral vasospasm. Milrinone is also used in the treatment of cerebral vasospasm. The aim of the present study was to compare the effect of prophylactic magnesium sulphate and milrinone on the incidence of cerebral vasospasm after subarachnoid hemorrhage. MethodsThe study included 90 patients with aneurysmal subarachnoid hemorrhage classified randomly (by simple randomization) into two groups: magnesium sulphate was given as an infusion of 500mg.day−1 without loading dose for 21 days. Group B: milrinone was given as an infusion of 0.5μg.kg−1.min−1 without loading dose for 21 days. The cerebral vasospasm was diagnosed by mean cerebral blood flow velocity in the involved cerebral artery (mean flow velocity≥120cm.s−1), neurological deterioration by Glasgow coma scale, or angiography (the decrease in diameter of the involved cerebral artery >25%). ResultsThe mean cerebral blood flow velocity decreased significantly in the magnesium group compared to milrinone group through Day 7, Day 14 and Day 21 (p<0.001). The incidence of cerebral vasospasm decreased significantly with magnesium compared to milrinone (p=0.007). The Glasgow coma scale significantly improved in the magnesium group compared to milrinone group through Day 7, Day 14 and Day 21 (p=0.036, p=0.012, p=0.016, respectively). The incidence of hypotension was higher with milrinone than magnesium (p=0.012). ConclusionsThe incidence of cerebral vasospasm after aneurysmal subarachnoid hemorrhage was significantly lower and Glasgow coma scale significantly better with magnesium when compared to milrinone. Milrinone was associated with a higher incidence of hypotension and requirement for dopamine and norepinephrine when compared to magnesium.

Effect of magnesium sulphate and milrinone on cerebral vasospasm after aneurysmal subarachnoid hemorrhage: a randomized study

BackgroundAneurysmal subarachnoid hemorrhage is an important cause of premature death and disability worldwide. Magnesium sulphate is shown to have a neuroprotective effect and it reverses cerebral vasospasm. Milrinone is also used in the treatment of cerebral vasospasm. The aim of the present study was to compare the effect of prophylactic magnesium sulphate and milrinone on the incidence of cerebral vasospasm after subarachnoid hemorrhage. MethodsThe study included 90 patients with aneurysmal subarachnoid hemorrhage classified randomly (by simple randomization) into two groups: magnesium sulphate was given as an infusion of 500mg.day−1 without loading dose for 21 days. Group B: milrinone was given as an infusion of 0.5μg.kg−1.min−1 without loading dose for 21 days. The cerebral vasospasm was diagnosed by mean cerebral blood flow velocity in the involved cerebral artery (mean flow velocity≥120cm.s−1), neurological deterioration by Glasgow coma scale, or angiography (the decrease in diameter of the involved cerebral artery >25%). ResultsThe mean cerebral blood flow velocity decreased significantly in the magnesium group compared to milrinone group through Day 7, Day 14 and Day 21 (p<0.001). The incidence of cerebral vasospasm decreased significantly with magnesium compared to milrinone (p=0.007). The Glasgow coma scale significantly improved in the magnesium group compared to milrinone group through Day 7, Day 14 and Day 21 (p=0.036, p=0.012, p=0.016, respectively). The incidence of hypotension was higher with milrinone than magnesium (p=0.012). ConclusionsThe incidence of cerebral vasospasm after aneurysmal subarachnoid hemorrhage was significantly lower and Glasgow coma scale significantly better with magnesium when compared to milrinone. Milrinone was associated with a higher incidence of hypotension and requirement for dopamine and norepinephrine when compared to magnesium.

Influential factors of cerebral oxygen saturation in pediatric cardiovascular surgery

To determine the intervention measures for the decrease of cerebral tissue oxygen saturation during anesthesia for the congenital heart disease in children. Methods: Twenty-eight children with cardiac surgery were enrolled. Anesthesia was deepened with propofol (3 mg/kg) intravenous injection. The data of cerebral tissue oxygen saturation(SctO2), mean arterial pressure (MAP), HR, bispectral index (BIS), arterial partial pressure of oxygen (PaO2), arterial partial pressure of carbon dioxide (PaCO2), hemoglobin (Hb) and middle cerebral artery (MCA) mean flow velocity (Vm) at different points were collected after intravenous injection of propofol at 3 mg/kg. The changes of SctO2 and the influential factors were analyzed. Results: SctO2 decreased by 4.99% after deepen anesthesia, with 95% CI 4.33% to 5.65% (P>0.05). There was no significant differince in MAP, PaO2, PaCO2, and Hb between the time points after deepen anesthesia and the baseline (P>0.05). MCA Vm decreased obviously after deepen anesthesia for 1, 5, 10 min (P<0.05). The decrease in MAP, HR, PaCO2 and MCA Vm is positively correlated with the decrease in SctO2. Conclusion: The decrease of MAP, HR, PaCO2, and MCA Vm is the risk factor for SctO2. To avoid the decrease, it needs to maintain the stability of SctO2 and prevent neurological complications.

Abstract TMP87: Non-Invasive Respiratory Impedance Enhances Cerebral Perfusion in Acute Stroke Patients

Introduction: Optimization of cerebral blood flow is a cornerstone of clinical management in a number of neurologic diseases, most notably acute ischemic stroke. Intra-thoracic pressure influences cardiac output and has the potential to impact cerebral blood flow (CBF). We aimed to quantify cerebral hemodynamic changes in acute ischemic stroke patients during increased respiratory impedance using a non-invasive oral device. Methods: Cerebral perfusion was measured during low (6cm H 2 0) and high (12cm H 2 0) levels of respiratory impedance in 20 patients within 72 hours of acute ischemic stroke. Microvascular CBF was measured by optical diffuse correlation spectroscopy, and middle cerebral artery mean flow velocity (MFV) was assessed by transcranial Doppler ultrasound. Results: High level respiratory impedance resulted in a 10% increase in MFV. Low level respiratory impedance resulted in a smaller (4%) non-significant change in MFV. Changes in cortical CBF were non-significant (figure). MFV varied across all studied levels (baseline vs low vs high, p=0.0017) with a significant test of trend (p=0.001), but this was not seen with microvascular CBF (p=0.33). Heart rate, cardiac output, and end tidal CO 2 remained stable during all levels of respiratory impedance. There was a small increase in mean arterial blood pressure at the low and high level of respiratory impedance, 4% (p=0.013) and 6% (p=0.017) respectively. All patients completed the protocol in its entirety, and the respiratory impedance exercise was well tolerated. Conclusions: Manipulating intrathoracic pressure via non-invasive respiratory impedance was safe and produced a small but measurable increase in cerebral blood flow in acute stroke patients. Future studies are warranted to assess whether respiratory impedance is feasible during hyperacute stroke management, and to determine the effect of volume status on the hemodynamic response to respiratory impedance.

Abstract WP322: Inhaled Nitric Oxide Augments Cerebral Blood Flow in Healthy Subjects

Introduction: Optimizing cerebral blood flow (CBF) is a cornerstone of clinical management for a number of neurologic disease states, most notably acute ischemic stroke. Transdermal nitric oxide donors are being investigated for acute stroke, though the effect of inhaled nitric oxide (iNO) on CBF remains largely unknown. Here we aim to quantify the cerebral hemodynamic response to iNO in healthy volunteers. Methods: Cerebral perfusion was measured during three doses of iNO (5ppm, 10ppm, and 20ppm) using the iNOMAX system (Mallinckrodt Pharmaceuticals) in 20 healthy volunteers. Continuous measurements of microvascular CBF were made with diffuse correlation spectroscopy (DCS), while middle cerebral artery mean flow velocity (MFV) was measured with transcranial Doppler. Cardiopulmonary status and nitric oxide toxicity (i.e. NO 2 ) were continuously monitored for safety. Results: Overall, iNO was safe and well tolerated. All subjects completed the protocol in its entirety. All 3 doses of iNO resulted in a small but statistically significant increase in microvascular CBF as compared to baseline (figure). No significant changes in MFV were identified (figure). During administration of iNO, there was no detrimental effect on blood pressure, nor was there any significant accumulation of toxic metabolites. Conclusions: iNO was safe and produced a small but significant increase in microvascular CBF in healthy volunteers. Future studies are warranted to determine the optimal dose of iNO and to explore the effect in acute ischemic stroke patients.

Compromised Cerebrovascular Regulation and Cerebral Oxygenation in Pulmonary Arterial Hypertension.

BackgroundFunctional cerebrovascular regulatory mechanisms are important for maintaining constant cerebral blood flow and oxygen supply in heathy individuals and are altered in heart failure. We aim to examine whether pulmonary arterial hypertension (PAH) is associated with abnormal cerebrovascular regulation and lower cerebral oxygenation and their physiological and clinical consequences.Methods and ResultsResting mean flow velocity in the middle cerebral artery mean flow velocity in the middle cerebral artery (MCAvmean); transcranial Doppler), cerebral pressure‐flow relationship (assessed at rest and during squat‐stand maneuvers; analyzed using transfer function analysis), cerebrovascular reactivity to CO 2, and central chemoreflex were assessed in 11 patients with PAH and 11 matched healthy controls. Both groups also completed an incremental ramp exercise protocol until exhaustion, during which MCAvmean, mean arterial pressure, cardiac output (photoplethysmography), end‐tidal partial pressure of CO 2, and cerebral oxygenation (near‐infrared spectroscopy) were measured. Patients were characterized by a significant decrease in resting MCAvmean (P<0.01) and higher transfer function gain at rest and during squat‐stand maneuvers (both P<0.05). Cerebrovascular reactivity to CO 2 was reduced (P=0.03), whereas central chemoreceptor sensitivity was increased in PAH (P<0.01), the latter correlating with increased resting ventilation (R 2=0.47; P<0.05) and the exercise ventilation/CO2 production slope (V˙E/V˙CO2 slope; R 2=0.62; P<0.05) during exercise for patients. Exercise‐induced increases in MCAvmean were limited in PAH (P<0.05). Reduced MCAvmean contributed to impaired cerebral oxygen delivery and oxygenation (both P<0.05), the latter correlating with exercise capacity in patients with PAH (R 2=0.52; P=0.01).ConclusionsThese findings provide comprehensive evidence for physiologically and clinically relevant impairments in cerebral hemodynamic regulation and oxygenation in PAH.

90 Comparison of Emergency Department Antihypertensive Agents on Cerebral Blood Flow

Data on the cerebral effects of commonly administered emergency department (ED) antihypertensive agents are limited. These effects are potentially important in patients requiring blood pressure reduction in neurological emergencies or those with known intracranial stenosis. The study objective was to measure the effect of common ED antihypertensive agents on cerebral blood flow in ED patients with severely elevated blood pressure. We conducted a prospective, quasi-experimental study of patients with a SBP > 180 mmHg and planned antihypertensive treatment in the ED. Patients who were < 18 years, pregnant, unable to consent prior to treatment, or had a known acute stroke were excluded. Non-invasive hemodynamic and cerebral vascular measurements were obtained prior to and post treatment. Cerebral vascular measurements were obtained with a transcranial Doppler fixed to a head-frame to detect middle cerebral artery mean flow velocities (MFV). Antihypertensive therapy was at the discretion of the treating physician. Analysis included descriptive statistics and generalized linear modeling, adjusted for baseline BP, to test the effect of four categories of antihypertensive agents on MFV. Categories included oral clonidine, intravenous (IV) labetalol, IV hydralazine and combination therapy (agents from ≥ 2 classes given within a 30-minute period). We enrolled 35 patients (37% female) with a mean age of 49 ± 13 years. A total of 8 (23%) patients received clonidine, 6 (17%) IV labetalol, 5 (14%) IV hydralazine and 16 (46%) combined therapy. Combination therapy most frequently included IV hydralazine and IV labetalol. The mean baseline SBP was 214 ± 24 mmHg and MFV was 49 ± 13 cm/sec. The mean percentage fall in mean arterial pressure by medication was: clonidine -12 ±7%, labetalol -13 ±12%, hydralazine -23 ± 11%, and combination -23 ± 16%. The overall change in MFV was -9 ± 15%, and by medication was: clonidine -10% (95% CI -2 to -21%), labetalol -11% (95% CI -5 to -27%), hydralazine +1% (95% CI -18 to +21%), and combination -11% (95% CI -2 to -19%). Adjusting for baseline BP, patients receiving hydralazine had less change in MFV compared to other medications (difference between means +12%, 95% CI -3 to +26%, p=0.1). In this study with modest BP reductions, common rapid-acting ED antihypertensive medications have comparable effects on cerebral blood flow. These results hint that cerebral blood flow may be more stable with hydralazine administration, but further testing is required.

A mesenteric traction syndrome affects near-infrared spectroscopy evaluated cerebral oxygenation because skin blood flow increases.

During abdominal surgery manipulation of internal organs may induce a "mesenteric traction syndrome" (MTS) including a triad of flushing, hypotension, and tachycardia that lasts for about 30min. We evaluated whether MTS affects near-infrared spectroscopy (NIRS) assessed frontal lobe oxygenation (ScO2) by an increase in forehead skin blood flow (SkBF). The study intended to include 10 patients who developed MTS during pancreaticoduodenectomy and 22 patients were enrolled (age 61 ± 8 years; mean ± SD). NIRS determined ScO2, laser Doppler flowmetry determined SkBF, cardiac output (CO) was evaluated by pulse-contour analysis (Modelflow), and transcranial Doppler assessed middle cerebral artery mean flow velocity (MCA Vmean). MTS was identified by flushing within 60min after start of surgery. MTS developed 20min (12-24; median with range) after the start of surgery and heart rate (78 ± 16 vs. 68 ± 17bpm; P = 0.0032), CO (6.2 ± 1.4 vs. 5.3 ± 1.1L min-1; P = 0.0086), SkBF (98 ± 35 vs. 80 ± 23 PU; P = 0.0271), and ScO2 (71 ± 6 vs. 67 ± 8%; P < 0.0001), but not MCA Vmean (32 ± 8 vs. 32 ± 7; P = 0.1881) were largest in the patients who developed MTS. In some patients undergoing abdominal surgery NIRS-determined ScO2 is at least temporarily affected by an increase in extra-cranial perfusion independent of cerebral blood flow as indicated by MCA Vmean. Thus, NIRS evaluation of ScO2 may overestimate cerebral oxygenation if patients flush during surgery.

Carbon monoxide reduces near-infrared spectroscopy determined ‘total’ hemoglobin: a human volunteer study

Carbon monoxide (CO) increases middle cerebral artery mean flow velocity (MCAVmean), but the effect of CO on the near-infrared spectroscopy (NIRS) determined cerebral oxygenation (ScO2) is not detailed. In our study, 11 non-smoking subjects breathed 100% O2 through a closed circuit. A CO2 scrubber with CO (1.5 mL kg−1) was added to the circuit. Two NIRS systems (NIRO-200NX and INVOS-5100) assessed ScO2 as the ratio of oxygenated to deoxygenated hemoglobin, while venous blood samples were analyzed for carboxyhemoglobin (COHb). After CO/O2 rebreathing COHb increased to 8.7% (IQR; 7.9–9.4; p = .004) vs. normoxia, but MCAVmean remained stable (55.6 cm s−1; 53.1–69.7) compared to inhalation of O2 (54.6 cm s−1; 48.4–62.9; p = .178) and normoxia (54.1 cm s−1; 44.5–66.9; p = .055). Also, INVOS-5100 determined ScO2 increased during CO/O2 (74.4 ± 7.5%) and O2 inhalation (73.1 ± 7.2%) compared to normoxia (68.9 ± 6.9%; p < .001). In contrast, NIRO-200NX determined ScO2 remained unchanged during CO/O2 and O2 inhalations but oxygenated and deoxygenated hemoglobin decreased (by 19.7 μM (median; IQR 2.8–34.8; p = .016) and 37.3 μM (30.8–46.6; p = .004), respectively) during inhalation of CO/O2 compared to inhalation of O2. Therefore, NIRO-200NX determined ‘total’ hemoglobin (sum of O2Hb and HHb) decreased (by 62.1 μM; 44.5–78.2; p = .001). In conclusion, exposure to CO did not increase MCAVmean, and neither NIRO-200NX nor INVOS-5100 detected a change in ScO2 when CO was added to inhalation of oxygen. Unaffected ScO2 after exposure to CO reflected a similar decrease in oxygenated and deoxygenated hemoglobin suggesting that detection of exposure to CO by NIRS should focus on ‘total’ hemoglobin rather than on ScO2.

Non-Invasive Respiratory Impedance Enhances Cerebral Perfusion in Healthy Adults.

Optimization of cerebral blood flow (CBF) is the cornerstone of clinical management in a number of neurologic diseases, most notably ischemic stroke. Intrathoracic pressure influences cardiac output and has the potential to impact CBF. Here, we aim to quantify cerebral hemodynamic changes in response to increased respiratory impedance (RI) using a non-invasive respiratory device. We measured cerebral perfusion under varying levels of RI (6 cm H2O, 9 cm H2O, and 12 cm H2O) in 20 healthy volunteers. Simultaneous measurements of microvascular CBF and middle cerebral artery mean flow velocity (MFV), respectively, were performed with optical diffuse correlation spectroscopy and transcranial Doppler ultrasound. At a high level of RI, MFV increased by 6.4% compared to baseline (p = 0.004), but changes in cortical CBF were non-significant. In a multivariable linear regression model accounting for end-tidal CO2, RI was associated with increases in both MFV (coefficient: 0.49, p < 0.001) and cortical CBF (coefficient: 0.13, p < 0.001), although the magnitude of the effect was small. Manipulating intrathoracic pressure via non-invasive RI was well tolerated and produced a small but measurable increase in cerebral perfusion in healthy individuals. Future studies in acute ischemic stroke patients with impaired cerebral autoregulation are warranted in order to assess whether RI is feasible as a novel non-invasive therapy for stroke.

Abstract WP432: Non-invasive Respiratory Impedance Enhances Cerebral Perfusion

Background: Optimization of cerebral blood flow is the cornerstone of clinical management in a number of neurologic diseases, most notably ischemic stroke. Intra-thoracic pressure influences cardiac output and has the potential to impact cerebral blood flow (CBF). Here we aim to quantify cerebral hemodynamic changes in response to increased respiratory impedance using a non-invasive respiratory device. Methods: Cerebral perfusion was measured under varying levels of respiratory impedance (6cm H 2 0, 9cm H 2 0, and 12 cm H 2 0) in 20 healthy volunteers. Simultaneous measurements of microvascular CBF and middle cerebral artery mean flow velocity (MFV), respectively, were performed with optical diffuse correlation spectroscopy (DCS) and transcranial Doppler ultrasound (TCD). Results: At the high level of respiratory impedance, mean flow velocity increased by 6.4% compared to baseline (p=0.004), but changes in cortical CBF were smaller and non-significant (Figure). Heart rate, cardiac output, respiratory rate, and end tidal CO 2 remained stable during all levels of respiratory impedance. There was small increase in mean arterial blood pressure, 1.7% (p=0.006), at the high level of respiratory impedance. In a multivariable linear regression model accounting for end tidal CO 2 and individual variability, respiratory impedance was associated with increases in both mean flow velocity (coefficient: 0.49, p&lt;0.001) and cortical CBF (coefficient: 0.13, p&lt;0.001). Conclusions: Manipulating intrathoracic pressure via non-invasive respiratory impedance was well tolerated and produced a small but measurable increase in cerebral perfusion in healthy individuals. Future studies in acute ischemic stroke patients with impaired cerebral autoregulation is warranted in order to assess whether respiratory impedance is feasible as a novel non-invasive therapy for stroke.

Evidence for hysteresis in the cerebral pressure-flow relationship in healthy men.

The cerebrovasculature is more efficient at compensating for pharmacologically induced transient hypertension versus transient hypotension. Whether this phenomenon exists during nonpharmacologically induced hypertension and hypotension is currently unknown. We compared the percent change in mean velocity in the middle cerebral artery (MCAvmean) per percent change in mean arterial pressure (MAP) (%ΔMCAVmean/%ΔMAP) during transient hypertension and hypotension induced during squat-stand maneuvers performed at 0.05 Hz (20-s cycles) and 0.10 Hz (10-s cycles) in 58 male volunteers. %ΔMCAvmean/%ΔMAP was attenuated by 25% (P = 0.03, 0.05 Hz) and 47% (P < 0.0001, 0.10 Hz) during transient hypertension versus hypotension. Thus, these findings indicate that the brain in healthy men is better adapted to compensate for physiologically relevant transient hypertension than hypotension.NEW & NOTEWORTHY The novel finding of this study is that the change in middle cerebral artery mean flow velocity is attenuated during hypertension compared with hypotension physiologically induced by oscillations in blood pressure in men. These results support that the human brain is more effective at compensating for transient hypertension than hypotension.

Staged carotid artery angioplasty and stenting for patients with high-grade carotid stenosis with high risk of developing hyperperfusion injury: a retrospective analysis of 44 cases

BackgroundHyperperfusion syndrome (HPS) is a rare but potentially a life-threatening complication after carotid artery angioplasty and stenting (CAS). Staged CAS has been an alternative to prevent HPS.Materials and methods44 of...

Early Ambulation in Patients With External Ventricular Drains: Results of a Quality Improvement Project.

Prolonged immobility in patients in the intensive care unit (ICU) can lead to muscle wasting and weakness, longer hospital stays, increased number of days in restraints, and hospital-acquired infections. Increasing evidence demonstrates the safety and feasibility of early mobilization in the ICU. However, there is a lack of evidence in the safety and feasibility of mobilizing patients with external ventricular drains (EVDs). The purpose of this study was to determine the safety and feasibility of early mobility in this patient population. We conducted a prospective, observational study. All patients in the study were managed with standard protocols and procedures practiced in our ICU including early mobility. Patients with an EVD who received early mobilization were awake and following commands, had a Lindegaard ratio <3.0 or middle cerebral artery (MCA) mean flow velocity <120 cm/s, a Mean Arterial Pressure (MAP) > 80 mm Hg, and an intracranial pressure consistently <20 mm Hg. Data were collected by physical therapists at the time of encounter. Ninety patients with a total of 185 patient encounters were recorded over a 12-month period. The average time between EVD placement and physical therapy (PT) session was 8.3 ± 5.5 days. In 149 (81%) encounters, patients were at least standing or better. Patients were walking with assistance or better in 99 (54%) encounters. There were 4 (2.2%) adverse events recorded during the entire study. This observational study suggests that PT is feasible in patients with EVDs and can be safely tolerated. Further research is warranted in a larger patient population conducted prospectively to assess the potential benefit of early mobility in this patient population.

OP.3C.05] CHARACTERISTICS OF CEREBRAL HEMODYNAMICS AND CAROTID STIFFNESS IN PATIENTS WITH ISCHEMIC LEUKOARAIOSIS AND NEW ULTRASOUND INDICES OF ISCHEMIC LEUKOARAIOSIS

Objective: Leukoaraiosis (ILA) is believed to be ischaemic in origin due its association with cerebrovascular risk factors and similar location as lacunar infarctions. Its pathophysiology is not well understood and its diagnosis is still based on magnetic resonance imaging (MRI) as well as exclusion of other causes of white matter hyperintensities (WMH). So far there are no known confirming or screening diagnostic tests of ILA. Ultrasound studies have recently shown increased large artery stiffness, increased cerebrovascular resistance and lower cerebral blood flow in ILA patients. Increased arterial stiffness and decreased blood flow could have a synergistic effect and their ratio could be a useful diagnostic index of ILA. Design and method: We used Trans Cerebral Doppler sonography (TCD) and carotid duplex ultrasound to compeare cerebral blood flow and carotid stiffness in 53 ILA patients to 40 risk factor matched controls. The ILA diagnosis was based on head MRI and exclusion of other causes of WMH. Middle cerebral artery (MCA) systolic, diastolic and mean blood flow velocities (v-MCAs, v-MCAd, v-MCAm) and resistance indices (RI, PI) were determined. Carotid stiffness was accessed by pulse wave velocityβ (PWVβ, m/s), pressure–strain elasticity modulus (Ep, kPa) and β index. In addition we introduced new ILA indices (ILAi) that are rations of carotid stiffness parameters and MCA mean blood flow velocity. The diagnostic significance of ILAi for the prediction of ILA was analysed. Results: We found significantly lower diastolic, systolic and mean MCA blood flow velocities and increased carotid stiffness in the ILA group (p < 0,05). Higher pulsatility and resistivity indices of MCA were found in the ILA group, but they did not reached statistical significance. All the ILAi were significantly higher in the ILA group, the most significant was PWVβ/v-ACMm (p = 0.003). All ILAi were allso significantly associated with ILA and were sensitive and specific for predicting ILA (p < 0.05). Conclusions: MCA blood flow velocities are lower and carotid stiffness increased in ILA patients compared to risk factors matched controls. The combination of lower velocities and increased carotid stiffness represented as ILA indices could have a potential diagnostic value for ILA.

Impact of aerobic fitness on cerebral blood flow and cerebral vascular responsiveness to CO2 in young and older men.

We sought to test the hypothesis that brain blood flow and cerebral vascular responsiveness to carbon dioxide (CVRCO2 ) are greater in aerobically trained young and old individuals compared to their untrained counterparts. In 11 young trained {[23 (20-26) years] [mean (95% confidence interval)]}, 10 young untrained [25 (22-28) years], 8 older trained [65 (61-69) years], and 9 older untrained [67 (64-71) years] healthy individuals, Doppler ultrasound of the internal carotid (ICA) and vertebral (VA) artery blood flow were determined, along with middle cerebral artery mean flow velocity (MCA Vmean ). Bilateral ICA blood flow was higher in trained individuals when compared to untrained (≈31%, P<0.05), but was not influenced by age. VA blood flow was not affected by age or cardiorespiratory fitness. MCA Vmean was reduced with age [59.5 (55.0-64.1) cm/s young vs 43.6 (38.4-48.9) cm/s old, P<0.05] with no significant effect of training observed. MCA CVRCO2 were not significantly affected by either age or training status, while ICA CVRCO2 tended to be elevated in the old trained group. These findings indicate that endurance training enhances bilateral ICA but not VA blood flow in both young and older individuals.

Abstract WP350: Pumping Against Gravity - Cardiac Function Affects Fluctuations in Cerebral Blood Flow Caused by Head Position Change in Acute Ischemic Stroke

Introduction: Acute ischemic stroke (AIS) patients often have the head-of-bed (HOB) elevated to 30 0 while in the Emergency Department (ED). Flat HOB positioning has been shown to impact cerebral flow. Whether this holds true in undifferentiated, ED stroke patients is unknown. Hypothesis: We tested the hypothesis that 0 0 HOB positioning improves middle cerebral artery (MCA) mean flow velocity (MFV) in AIS compared to 30 0 . We secondarily tested the hypothesis that lower cardiac output (CO) is associated with greater fluctuation of MFV. Methods: This was a quasi-experimental study with repeat measurements of MCA MFV at 30 0 and 0 0 HOB position. Patients &gt; 18 years presenting to the ED within 12 hours of symptom onset and a NIHSS ≥ 4 were eligible. After applying non-invasive monitoring of mean arterial pressure (MAP) and CO, an investigator used transcranial Doppler to obtain bilateral MCA MFV at 30 0 and 0 0 HOB position. If a signal was unobtainable on the ischemic side, the contralateral MFV was used for analysis. The primary analysis comprised all subjects with confirmed stroke on subsequent imaging and included student t-test for continuous measures. Secondary analysis used multiple linear regression to test if baseline NIHSS, age, MAP and CO were associated with changes in MFV. Results: There were 38 subjects enrolled, of whom 32 had confirmed AIS and were included in analysis. The mean age was 66 (±15) years and NIHSS 7 (±6). Stroke location was mixed (50% lacunar, 25% posterior and 25% anterior circulation). Averaged across all subjects, the MFV did not significantly increase when changing the HOB position from a 30 0 to 0 0 (+0.7 cm/s, 95% CI -1.6 to 3.1). Nevertheless, 16% (95% CI 5-33%) of subjects had a ≥ 20% increase and 47% (95% CI 29-65%) had any increase in MFV at 0 0 compared to 30 0 HOB. Adjusting for age, NIHSS and MAP, lower CO was associated with greater change in MFV (+2 cm/s [95% CI 0.2-3.7 cm/s] for every 1 L/min lower cardiac output, p=0.03). Conclusions: In conclusion, in a mixed sample of ED AIS patients, lower HOB position does not significantly impact cerebral flow on average, yet a considerable proportion of individuals may benefit from lower HOB position. Low cardiac output may identify those that benefit most.

Eat, drink and be merry--and protect the brain.

Cerebral blood flow is sensitive to even minor changes in the arterial carbon dioxide tension (), with the ‘reactivity’ being ∼4% for a 1 mmHg change in . That is the case at a normal of ∼40 mmHg (5.3 kPa), but the reactivity becomes lower at low or high levels (e.g. Hurr et al. 2015a,b). Also, the cerebral CO2 reactivity differs between the parts of the brain served by the internal carotic artery, including the middle cerebral artery and those parts of the brain supplied by the vertebral artery (Sato et al. 2012). Accepting anatomical differences and that the CO2 reactivity of the brain depends on the , there remains variation in responses, i.e. the CO2 reactivity of the brain is reported with a substantial SD of ∼30% of the mean (e.g. Sato et al. 2012). Such variation in results may be taken to reflect how accurately the variable can be determined by the method chosen, or the SD may reflect that the measured varible is not entirely stable, e.g. heart rate and blood pressure vary through the respiratory cycle. Yet, there may also be genuine differences among subjects and circumstanses. For example, the CO2 reactivity for the brain circulation is reported to increase during exercise (Rasmussen et al. 2006), while CO2 reactivity does not explain the reduction in cerebral blood flow when people are upright (Immink et al. 2009). Among subjects, it may not be appreciated that there can be sex differences in the determined variable(s), dependence on the size of the individual or variation related to physical fitness besides age. Such influences are then addressed in separate evaluations, and it should be considered whether difference in results may also relate to genetics. An important physiological variable, cardiac output, differs according to Arg16Gly polymorphism, both at rest and during exercise (Snyder et al. 2006; Rokamp et al. 2013). Considering a genetic influence on the circulation, Hurr et al. (2015b) provided the observation that the increase in middle cerebral artery mean flow velocity as an indication for cerebral blood flow in response to (expressed by the end-tidal value) is smaller at college age for African Americans than for Causian Americans. A comparison of the CO2 reactivity of the brain between different ethnic groups is of interest because African Americans are known to suffer from cardiovascular diseases related to the so-called metabolic syndrome/diabetes type II, including hypertension, coronary artery disease and, notably, stroke. To prevent such calamaties, focus has been on, e.g. control of diet, antihypertensive medication and prescription of exercise, all of which typically are not attractive to the patient, who is likely not to be experiencing symptoms when the advise/therapy is instituted. Thus, type II diabetics suffer from fatigue (Kim et al. 2015), limiting their enthusiasm for exericse. Advice may be obtained in the Bible: And I commend joy, for man has nothing better under the sun but to eat and drink and be joyful, for this will go with him in his toil through the days of his life that God has given him under the sun (Ecclesiastes 8:15). One or several interventions can be proved beneficial, but the patient's adherence to the intervention is limited if it is not associated with some joy. Obviously, taking pills is no fun and medication is often not taken because the patient experiences side-effects. Likewise, prescription of exercise results in increased activity, but only for as long as the study lasts if it is not felt to be interesting. For example, Ottesen et al. (2010) found that among inactive women (fun) football creates more ‘social capital’ than (dull) running. Also it is well known that whatever diet is applied and however successful it is in reducing weight, the weight is regained shortly after the end of the diet. In a follow-up paper in this isssue of Experimental Physiology, Hurr et al. (2015a) demonstrate that the ∼20% reduced CO2 reactivity for young African Americans is normalized following administration of flavanol. As mentioned by the authors, flavanol is an ingredient of, for example, chocolate, black tea and red wine. Obviously, it needs to be established to what extent the reactivity of the brain early in life is coupled to later development of stroke, but before that relationship is established we and, especially, people of African orgin can be advised not to be restricted but to enjoy the pleasure of, for example, chocolate, tea and red wine. Cheers!

A retrospective pilot study of correlation of cerebral augmentation effects of external counterpulsation with functional outcome after acute ischaemic stroke

ObjectiveExternal counterpulsation (ECP) is a non-invasive method used to augment cerebral blood flow of patients with ischaemic stroke via induced hypertension. We aimed to explore the correlation between the cerebral blood flow augmentation effects induced by ECP and clinical outcome after acute ischaemic stroke.MethodsWe retrospectively analysed our ECP registry of patients with ischaemic stroke who were enrolled within 7 days after stroke onset. Bilateral middle cerebral arteries of patients were monitored using transcranial Doppler (TCD). Flow velocity changes before, during and after ECP were, respectively, recorded for 3 min. The cerebral augmentation index (CAI) was the increase in percentage of the middle cerebral artery mean flow velocity during ECP compared with baseline. TCD data were analysed based on the side ipsilateral or contralateral to the infarct. The modified Rankin Scale (mRS) (good outcome: mRS 0∼2; poor outcome: mRS 3∼6) was evaluated 6 months after the index stroke.Results72 patients were included (mean age, 63.8±10.7 years; 87.5% males). At month 6 after stroke onset, univariate analysis showed that the National Institutes of Health Stroke Scale at recruitment was significantly higher and ECP therapy duration was longer in the poor outcome group, while the ipsilateral CAI was significantly lower in the good outcome group than that in the poor outcome group (3.71±4.94 vs 7.73±7.66, p=0.044). Multivariate logistic regression showed that ipsilateral CAI was independently correlated with an unfavourable functional outcome after adjusting for confounding factors.ConclusionsThe higher degree of cerebral blood flow velocity augmentation on the side ipsilateral to the infarct induced by ECP is independently correlated with an unfavourable functional outcome after acute ischaemic stroke.

Volatile sedation with sevoflurane in intensive care patients with acute stroke or subarachnoid haemorrhage using AnaConDa®: an observational study

The anaesthetic conserving device, AnaConDa(®), allows use of inhaled anaesthetics for sedation in the intensive care unit. We prospectively measured cerebral and cardiopulmonary parameters in patients with acute stroke or subarachnoid haemorrhage during a switch from i.v. to inhalative sedation. 25 patients were switched from i.v. to an indefinite period of inhaled sedation with sevoflurane. Mean arterial (MAP), intracranial (ICP), and cerebral perfusion pressure (CPP), middle cerebral artery mean flow velocity (MFV) and fractional tissue oxygen extraction (FTOE), systemic cardiopulmonary parameters, and administered drugs were assessed before and after the change (-6 to +12 h). In 8 patients, critically reduced MAP or ICP crisis led to premature termination of sevoflurane sedation. In the other 17 patients, after the first hour, mean ICP increased [2.4 (4.5) mm Hg; P=0.046], MAP decreased [7.8 (14.1) mm Hg; P=0.036] and thus CPP decreased also [-10.2 (15.1) mm Hg; P=0.014]. MFV and FTOE did not change. Over a 12 hour post switch observational period, [Formula: see text] increased slightly [0.3 (0.8) kPa; P=0.104], ICP did not change [0.2 (3.9) mm Hg; P=0.865], but MAP [-6 (6.9) mm Hg; P=0.002] and thus CPP decreased [-6 (8.5) mm Hg; P=0.010]. Sevoflurane led to sufficient sedation, but decreased MAP and CPP in a selected cerebrovascular neurocritical care population. In about a third of these patients, severe adverse reactions, including intolerable ICP increases, were observed.