Middle Cerebral Blood Flow Velocity Research Articles

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 > 1.3 and group II with RI < 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 > 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.

The beach chair position for shoulder surgery in intravenous general anesthesia and controlled hypotension: Impact on cerebral oxygenation, cerebral blood flow and neurobehavioral outcome

Study objectivesThe aim of this study was to assess the impact of intravenous general anesthesia and controlled hypotension on cerebral saturation (rScO2), cerebral blood flow measured as middle cerebral artery blood flow velocity (Vmax MCA) and neurobehavioral outcome in patients scheduled for shoulder surgery in beach chair position. DesignProspective, assessor-blinded observational study. SettingUniversity hospital, shoulder surgery operating room. PatientsForty ASA I-II patients scheduled for shoulder surgery in beach chair position and controlled hypotension. InterventionsNeurological and neurobehavioral tests were performed prior and the day after surgery. The baseline data for near-infrared spectroscopy, bispectral index, cerebral blood flow, PaCO2 and invasive blood pressure (radial artery) were taken prior anesthesia and after anesthesia induction, after beach chair positioning and all 20 min after surgery start until discharge of the patient. MeasurementsNeurological and neurobehavioral tests, cerebral saturation (rScO2) using near-infrared spectroscopy, BIS, cerebral blood flow using Doppler of the middle cerebral artery (Vmax MCA), PaCO2 and invasive blood pressure assessed at heart and at the external acoustic meatus level. Main resultsThe incidence of cerebral desaturation events (CDEs) was 25%. The blood pressure drop 5 min after beach chair position measured at the acoustic meatus level in the CDE group was higher compared to patients without CDEs (p = 0.009) as was the rScO2 (p = 0.039) and the Vmax MCA (p = 0.002). There were no neurological deficits but patients with CDEs showed a greater negative impact on neurobehavioral tests 24 h after surgery compared to patients without CDEs (p = 0.001). ConclusionsIn ASA I-II patients intravenous general anesthesia and controlled hypotension in the beach chair position affects cerebral blood flow and cerebral oxygenation with impact on the neurobehavioral outcome.

Hypertonic Lactate to Improve Cerebral Perfusion and Glucose Availability After Acute Brain Injury*

Lactate promotes cerebral blood flow and is an efficient substrate for the brain, particularly at times of glucose shortage. Hypertonic lactate is neuroprotective after experimental brain injury; however, human data are limited. Prospective study (clinicaltrials.gov NCT01573507). Academic ICU. Twenty-three brain-injured subjects (13 traumatic brain injury/10 subarachnoid hemorrhage; median age, 59 yr [41-65 yr]; median Glasgow Coma Scale, 6 [3-7]). Three-hour IV infusion of hypertonic lactate (sodium lactate, 1,000 mmol/L; concentration, 30 µmol/kg/min) administered 39 hours (26-49 hr) from injury. We examined the effect of hypertonic lactate on cerebral perfusion (using transcranial Doppler) and brain energy metabolism (using cerebral microdialysis). The majority of subjects (13/23 = 57%) had reduced brain glucose availability (baseline pretreatment cerebral microdialysis glucose, < 1 mmol/L) despite normal baseline intracranial pressure (10 [7-15] mm Hg). Hypertonic lactate was associated with increased cerebral microdialysis lactate (+55% [31-80%]) that was paralleled by an increase in middle cerebral artery mean cerebral blood flow velocities (+36% [21-66%]) and a decrease in pulsatility index (-21% [13-26%]; all p < 0.001). Cerebral microdialysis glucose increased above normal range during hypertonic lactate (+42% [30-78%]; p < 0.05); reduced brain glucose availability correlated with a greater improvement of cerebral microdialysis glucose (Spearman r = -0.53; p = 0.009). No significant changes in cerebral perfusion pressure, mean arterial pressure, systemic carbon dioxide, and blood glucose were observed during hypertonic lactate (all p > 0.1). This is the first clinical demonstration that hypertonic lactate resuscitation improves both cerebral perfusion and brain glucose availability after brain injury. These cerebral vascular and metabolic effects appeared related to brain lactate supplementation rather than to systemic effects.

Non-Invasive Pressure Reactivity Index Using Doppler Systolic Flow Parameters: A Pilot Analysis.

The goal was to predict pressure reactivity index (PRx) using non-invasive transcranial Doppler (TCD) based indices of cerebrovascular reactivity, systolic flow index (Sx_a), and mean flow index (Mx_a). Continuous extended duration time series recordings of middle cerebral artery cerebral blood flow velocity (CBFV) were obtained using robotic TCD in parallel with direct intracranial pressure (ICP). PRx, Sx_a, and Mx_a were derived from high frequency archived signals. Using time-series techniques, autoregressive integrative moving average (ARIMA) structure of PRx was determined and embedded in the following linear mixed effects (LME) models of PRx: PRx ∼ Sx_a and PRx ∼ Sx_a + Mx_a. Using 80% of the recorded patient data, the LME models were created and trained. Model superiority was assessed via Akaike information criterion (AIC), Bayesian information criterion (BIC), and log-likelihood (LL). The superior two models were then used to predict PRx using the remaining 20% of the signal data. Predicted and observed PRx were compared via Pearson correlation, linear models, and Bland-Altman (BA) analysis. Ten patients had 3-4 h of continuous uninterrupted ICP and TCD data and were used for this pilot analysis. Optimal ARIMA structure for PRx was determined to be (2,0,2), and this was embedded in all LME models. The top two LME models of PRx were determined to be: PRx ∼ Sx_a and PRx ∼ Sx_a + Mx_a. Estimated and observed PRx values from both models were strongly correlated (r > 0.9; p < 0.0001 for both), with acceptable agreement on BA analysis. Predicted PRx using these two models was also moderately correlated with observed PRx, with acceptable agreement (r = 0.797, p = 0.006; r = 0.763, p = 0.011; respectively). With application of ARIMA and LME modeling, it is possible to predict PRx using non-invasive TCD measures. These are the first and as well as being preliminary attempts at doing so. Much further work is required.

Assessment of the cerebral pressure-flow relationship using psychological stress to manipulate blood pressure

Recent evidence indicates that cerebral autoregulation (CA) might be more pressure passive than previously thought. That is, cerebral blood flow, traditionally thought to be regulated independently of prevailing mean arterial pressure (MAP), might fluctuate, to some extent, as a function of MAP. However, due to limitations associated with experimental usage of pharmaceuticals to manipulate MAP and inconsistent control of arterial carbon dioxide, questions remain regarding the MAP-cerebral blood flow relationship, especially during typical daily activities that alter MAP. Therefore, the current study aimed to assess CA using a nonpharmacological acute psychological stress task to augment MAP, while at the same time controlling for end-tidal carbon dioxide (PET CO2 ). Twenty-five healthy young adults completed a stressful task while continuous measures of MAP, middle cerebral artery blood flow velocity (MCAv), and PET CO2 were recorded. Slope values obtained from hierarchical linear regression were used to assess the strength of the MAP-MCAv relationship and control for PET CO2 . The stress task significantly increased MAP (p<0.001) and MCAv (p<0.001), and decreased PET CO2 (p=0.05). For every 10mmHg task-induced increase in MAP, MCAv increased by ≈3.5%; task-induced changes in PET CO2 did not appreciably change the MAP-MCAv relationship. Greater task-induced MAP responses were significantly related to decreased MAP-MCAv slope values, consistent with CA. These data support the hypothesis that CA is more pressure passive than previously thought and provide initial evidence indicating that a pressure-passive MAP-MCAv relationship may play a role in the observed associations between MAP stress responses, stroke, and cerebrovascular disease.

THE RELATIONSHIP BETWEEN BETA-AMYLOID AND VASCULAR HEALTH IN OLDER ADULTS

To assess the relationship of beta-amyloid (Aβ) burden with peripheral vascular endothelial function and central cerebrovascular resistance among cognitively normal older adults. We enrolled eighty-three participants aged 65 to 87. Global Aβ burden was quantified using [18F] Florbetapir. All individuals classified as elevated had global Aβ burden >1.1 standard uptake value ratio (SUVR). Using Doppler ultrasound, we examined a measure of vascular endothelial function, brachial artery flow-mediated dilation (FMD). Cerebrovascular resistance measured by pulsatility index (PI) and middle cerebral artery blood flow velocities were recorded by transcranial Doppler ultrasound during 8 minutes of rest. White matter lesions (WML) total volume and count, common indices of cerebral small vessel health, were quantified by MRI. After adjusting for age and cardiovascular risk factors, there was a significant negative association between Aβ burden and FMD (p<0.01), such that for each 0.1 increase in Aβ burden, FMD decreased by 0.8%. Decreased brachial artery FMD response was found in individuals with elevated Aβ compared with the non-elevated group (p<0.01). The optimal cut point of FMD predicting Aβ elevation was 5% (AUC=0.836, p<0.01, 95%CI: 0.742 - 0.930), with 81.8% sensitivity and 75.4% specificity. Higher PI was demonstrated in elevated Aβ individuals (p=0.04), but was not correlated with Aβ burden. WML were not associated with Aβ.

Regular walking breaks prevent the decline in cerebral blood flow associated with prolonged sitting.

Decreased cerebrovascular blood flow and function are associated with lower cognitive functioning and increased risk of neurodegenerative diseases. Prolonged sitting impairs peripheral blood flow and function, but its effects on the cerebrovasculature are unknown. This study explored the effect of uninterrupted sitting and breaking up sitting time on cerebrovascular blood flow and function of healthy desk workers. Fifteen participants (10 male, 35.8 ± 10.2 yr, body mass index: 25.5 ± 3.2 kg/m2) completed, on separate days, three 4-h conditions in a randomized order: 1) uninterrupted sitting (SIT), 2) sitting with 2-min light-intensity walking breaks every 30 min (2WALK), or 3) sitting with 8-min light-intensity walking breaks every 2 h (8WALK). At baseline and 4 h, middle cerebral artery blood flow velocity (MCAv) and CO2 reactivity (CVR) of the MCA and carotid artery were measured using transcranial Doppler (TCD) and duplex ultrasound, respectively. Cerebral autoregulation (CA) was assessed with TCD using a squat-stand protocol and analyzed to generate values of gain and phase in the very low, low, and high frequencies. There was a significant decline in SIT MCAv (-3.2 ± 1.2 cm/s) compared with 2WALK (0.6 ± 1.5 cm/s, P = 0.02) but not between SIT and 8WALK (-1.2 ± 1.0 cm/s, P = 0.14). For CA, the change in 2WALK very low frequency phase (4.47 ± 4.07 degrees) was significantly greater than SIT (-3.38 ± 2.82 degrees, P = 0.02). There was no significant change in MCA or carotid artery CVR ( P > 0.05). Results indicate that prolonged uninterrupted sitting in healthy desk workers reduces cerebral blood flow; however, this is offset when frequent short-duration walking breaks are incorporated. NEW & NOTEWORTHY Prolonged uninterrupted sitting in healthy desk workers reduces cerebral blood flow. However, this reduction in cerebral blood flow is offset when frequent short-duration walking breaks are incorporated into this sitting period. For those who engage in long periods of sedentary behavior, chronically breaking up these sitting periods with frequent active break strategies may have important implications for cerebrovascular health; however, further research should explore this hypothesis.

Compromised dynamic cerebral autoregulation in patients with generalized anxiety disorder: a study using transfer function analysis

BackgroundPatients with generalized anxiety disorder (GAD) usually present with various neurological symptoms, but the mechanisms remain unclear. We aimed to analyze the characteristics of dynamic cerebral autoregulation (dCA) in patients with GAD.MethodsPatients (aged ≥18 years) who were diagnosed with GAD were enrolled in this study. Medically and psychiatrically healthy volunteers were recruited as controls. Subjects received the Hamilton Rating Scale for Anxiety (HAMA) and 17-item Hamilton Depression Rating Scale (HAMD) evaluation. Noninvasive continuous arterial blood pressure and bilateral middle cerebral artery blood flow velocity were recorded simultaneously from each subject. Transfer function analysis was used to derive the autoregulatory parameters, including phase difference, gain, and coherence function.ResultsA total of 57 patients with GAD and 40 healthy volunteers were enrolled. We found that the phase difference values were significantly compromised in patients with GAD. In the Spearman correlation analysis, the phase difference values were negatively correlated with the HAMA scores and the HAMD scores. In the multiple linear regression analysis, GAD is negatively correlated with the phase difference values, whereas age is positively correlated with the phase difference values.ConclusionsOur results suggested that the dCA was compromised in patients with GAD and negatively correlated with the score of anxiety. Improving the dCA may be a potential therapeutic method for treating the neurological symptoms of GAD patients.

Cerebral Autoregulation Is Impaired In Recurrent Syncope Patients

PURPOSE: Cerebral autoregulation is a homeostatic mechanism that serves to maintain cerebral blood flow constant over a wide range of perfusion pressure. Syncope is thought to be caused by cerebral hypoperfusion due to the transient blood pressure drop, and thus impairment of cerebral autoregulation may facilitate syncope. A previous study has reported that a past history of syncope is a strong predictor of future syncope recurrence. However, it is unclear whether impaired cerebral autoregulation would be related with recurrent syncope. The purpose of this study was to test our hypothesis that cerebral autoregulation would be impaired in syncope patients with a past history of syncope as compared with those for the first time. METHODS: We evaluated cerebral autoregulation in 24 syncope patients for the first time (age; 64±19 years old, male/ female; 15/9) and 20 syncope patients with a past history of syncope (age; 52±26 years old, male/female; 11/9). In patients with recurrent syncope, the number of past syncope was 2.9±1.6 times (range 2-7 times). Middle cerebral artery mean blood flow velocity (MCA Vmean) and mean arterial pressure (MAP) were measured by transcranial Doppler ultrasound and tonometry on right radial artery for 3 min in the supine position. In offline analysis after the measurement, the transfer function gain between MAP and MCA Vmean were calculated at very low frequency (0.023-0.07 Hz, VLF) and low frequency (0.07-0.2 Hz, LF) ranges to estimate dynamic cerebral autoregulation. RESULTS: LF gain did not differ between syncope patients with a past history of syncope and those for the first time (P=0.23). In contrast, VLF gain was significantly higher in patients with a past history of syncope than in those for the first time (1.81±1.17 cm/s/mmHg vs. 1.09±0.65 cm/s/mmHg, P=0.02). CONCLUSIONS: These data suggest that impaired cerebral autoregulation at least in part explains physiological mechanisms underlying recurrent syncope.

Cerebral Blood Flow Pulse Is Influenced By Ascending Aortic Flow During Acute Hypotension

PURPOSE: Recently, it has been suggested that cardiac function is one of important physiological factors to determine cerebral blood flow (CBF). However, dynamic relationship between cardiac outflow and CBF is still unknown. The purpose of the present study was to assess the dynamic relationship between arterial blood pressure (BP) or ascending aortic blood flow and CBF. METHODS: Six male healhy subjects participated (age, height, and weight; 33±6 yrs, 173±3 cm, and 72±8 kg) in the present study. Continuous beat-by-beat arterial BP was recorded from a finger using the Penaz method. Ascending aortic blood flow velocity (Ao-BFV) and middle cerebral artery blood flow velocity (MCA-BFV) were continuously measured using supra-sternum and transcranial Doppler ultrasound. After 10 min of resting condition, bilateral thigh cuffs were rapidly inflated to 200 mmHg and maintained for 2 min. Then both cuffs were rapidly deflated, and data were subsequently collected for 1 min. The same measurements were performed in the supine and 45-degree semi- Fowler’s positions. Pearson’s correlation coefficients were calculated to identify the relationship between relative change of BP or Ao-BFV and those of MCA-BFV among individuals. RESULTS: Correlation coefficient of mean BP and mean MCA-BFV was much larger than that of mean Ao-BFV and mean MCA-BFV in both the supine and semi-Fowler’s positions (R=0.615 vs. 0.009 and 0.353 vs. -0.753). In contrast, the correlation coefficient of pulse BP and pulse MCA-BFV was much smaller than that of pulse Ao-BFV and pulse MCA-BFV in the supine position (R=-0.068 vs 0.659), while it was comparable in the semi-Fowler’s position (R=0.555 vs 0.435). CONCLUSIONS: Dynamic change in mean CBF are likely to be only influenced by mean BP. However, dynamic change in pulse CBF seems to be more influenced by that of pulse ascending aortic blood flow rather than pulse BP especially in the supine position.

Effect of hyperbaric oxygen combined with nimodipine on treatment of diffuse brain injury.

The aim of the present study was to was investigate the treatment efficacy of hyperbaric oxygen (HBO) combined with nimodipine on diffuse brain injury. AA total of 80 patients with diffuse brain injury were randomly divided into four groups: Group A, conventional treatment; Group B, conventional treatment + nimodipine; Group C, conventional treatment + HBO therapy and Group D, conventional treatment + nimodipine + HBO therapy. The Glasgow Coma Scale (GCS) score and serum tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels were assessed before treatment and at 8, 24, 48 and 72 h after treatment. The bilateral middle cerebral arterial blood flow velocity (VmMCA) was measured by transcranial Doppler ultrasound. The results indicated that serum TNF-α and IL-1β were significantly decreased in all groups at 24, 48 and 72 h after treatment, compared with 8 h after treatment (P<0.05), with Group D exhibiting the largest decrease. The serum TNF-α, IL-1β and VmMCA peaked at 8 h and gradually decreased over the treatment period. VmMCA was decreased in Group B and D compared with Group A and C, and the decrease rate was higher in Group D compared with Group B (P<0.05). GCS scores were significantly increased in all groups at 24, 48 and 72 h after treatment compared with 8 h after treatment (P<0.05), with Group D exhibiting the largest increase. Serum TNF-α and IL-1β levels were positively correlated with VmMCA (P<0.05) and negatively correlated with GCS (P<0.05). Punctate hemorrhage was observed in all groups on CT before treatment, with a value of 66±3 HU. Punctate hemorrhage was observed to decrease over time in CT images, and CT values were significantly decreased in all groups at 8, 24, 48 and 72 h compared with before treatment (P<0.05). CT values were significantly lower in group D compared with groups A, B and C (P<0.05) at all time points. Serum TNF-α and IL-1β levels were positively correlated with CT value (P<0.05). In conclusion, HBO combined with nimodipine exhibited increased efficacy in the treatment of brain injury compared with either treatment alone.

Cerebral blood flow velocity in migraine and chronic tension-type headache patients.

IntroductionThe present study seeks to use transcranial Doppler ultrasound to evaluate cerebral blood flow velocities in anterior and posterior circulation arteries, during an attack-free episode in migraine patients, with and without aura, as well as in chronic tension-type headache patients who were not receiving prophylactic medication.MethodsA total of 50 patients (35 female, 15 male) were evaluated during a headache-free episode: 30 migraine patients without aura (mean age: 32±8 years), 10 migraine patients with aura (mean age: 34±4 years), and 10 patients with chronic tension-type headache (mean age: 34±5 years).ResultsNo significant difference was present between anterior, middle, and posterior cerebral and vertebral arteries’ blood flow velocities between migraine patients, with and without aura, or in patients with a tension-type headache, and normal controls (p>0.05). However, a significant increase in basilar artery cerebral blood flow velocities relative to controls was present in patients with a tension-type headache (p>0.001).ConclusionIt is difficult to predict the main reason for the significant increase in basilar artery blood flow velocities in patients with chronic tension-type headache. It may be due to constriction of conductance or the dilatation of the resistance vessels.

Cerebral autoregulation during exposure to artificial gravity

Our work has previously shown that exposure to artificial gravity (AG) can improve orthostatic tolerance. The purpose of this work is to examine whether cerebral autoregulation is improved with AG in twelve hypovolemic men and women. The protocol consisted of an initial ~45 minutes of a “step up” tolerance period, used to determine participants' presyncopal limit, followed by ~45 minutes training period at GZ below participants presyncopal limit. Beat‐by‐beat blood pressure (Portapres), heart rate (ECG), middle cerebral artery blood flow velocity (Transcranial Doppler) and end‐tidal carbon dioxide (capnography) were collected on participants during short arm centrifugation. Cerebral autoregulation was assessed using transfer function analysis between mean arterial pressure (MAP) and mean cerebral blood flow velocity (MCBFV) in 3‐min intervals during the training period. Exposure to AG resulted in a significant positive correlation between GZ and MAP, MAP variability and MCBFV variability in the low frequency (LF) range (0.07–0.15 Hz). In addition, coherence between MAP and MCBFV in the LF range was positively correlated. There was no change in gain and phase between MAP and MCBFV in the same frequency range. With higher GZ, there was a significant positive correlation in coherence and significant negative correlation in gain between MAP and MCBFV in the very low frequency range (0.03–0.07 Hz). These data suggest that increasing GZ exposure is correlated to increasing MAP variability. However, despite this increased MAP variability gain values demonstrated a negative correlation with GZ, suggesting that cerebral autoregulation tended to improve with increasing GZ exposure. We expect increased coherence was a result of the increased MAP variability associated with higher GZ. These data may suggest that exposure to AG may be helpful to improve cerebral autoregulation. Therefore, one could speculate that AG may be a useful tool to consider as a countermeasure for post‐flight astronauts to improve their orthostatic tolerance as well as cerebral autoregulation and improve re‐adaptation to a gravity environment.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cyclooxygenase Inhibition and Cerebrovascular Reactivity: Interaction of Aging and Aerobic Fitness

The ability of the cerebral microvessels to respond to chemical or metabolic stimuli declines with age and this change may be one mechanism through which age‐related cognitive decline occurs. Prostaglandins play an important role in the control of vascular tone, therefore changes in prostaglandin synthesis or expression may be underlying the age‐related alterations in cerebral microvascular function. Additionally, we have previously shown that aerobic fitness was associated with a decrease in cerebral microvascular function after cyclooxygenase (COX) blockade; yet this was in a small sample size of healthy older adults who were not exercise trained. Thus, the purpose of our study was to evaluate the effect of age on cerebral microvascular reactivity to hypercapnia (CVR) and to determine if habitual exercise modifies the response to COX blockade. We recruited 45 younger (YA; age = 26±1 y) and 31 older (OA; age = 63±1 y) healthy adults, including 21 sedentary YA, 24 exercising YA, 12 sedentary OA, and 19 exercising OA. Aerobic fitness (VO2 max) was measured during an incremental cycle ergometer test. Middle cerebral artery blood flow velocity (MCAv) and end‐tidal CO2 (ETCO2) were continuously recorded. CVR was calculated as the linear slope of the relationship between ETCO2 and MCAv and was assessed before and after the administration of the COX inhibitor indomethacin (INDO). The change in CVR was calculated as pre INDO CVR – post INDO CVR. There were no group differences in MCAv pre INDO (YA: 65±3 cm/s vs. OA: 59±3 cm/s; p&gt;0.05); however, YA had higher MCAv post INDO (YA: 45±1 cm/s vs. OA: 40±2 cm/s; p&lt;0.05). OA had significantly greater change in CVR compared with YA (2.0±0.1 cm/s/mmHg vs. 1.5±0.2 cm/s/mmHg, respectively; p&lt;0.05). There was also a significant effect of habitual exercise, such that sedentary adults had a greater change in CVR compared with exercising adults (2.0±0.2 cm/s/mmHg vs. 1.5±0.2 cm/s/mmHg, respectively; p&lt;0.05). In addition, there was an inverse association between VO2 max and the change in CVR in OA (r=0.42, p&lt;0.05), but not in YA (p&gt;0.05). Our results indicate that older adults, regardless of exercise status, rely more on COX‐derived products for cerebral microvascular responses to hypercapnia. Our results also suggest that habitual exercise may alter the contribution of COX‐derived products to cerebral blood flow regulation.Support or Funding InformationSupported by National Institute of Health grant HL118154This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Countdown before voluntary exercise induces muscle vasodilation with decreased muscle sympathetic nerve activity in humans

We examined whether countdown (CD) before voluntary bicycle ergometer exercise induced cerebro‐cardiovascular responses and, if so, whether these responses to CD were altered by postural change from the semi‐recumbent to supine position. Young men (n=14) performed voluntary cycle exercise in the semi‐recumbent position while middle cerebral artery blood flow velocity (CBF; Doppler ultrasonography), heart rate (HR), blood pressure (finger photoplethysmography), oxygen consumption rate (VO2), oxygen saturation in the right thigh muscle (StO2; near‐infrared spectrometry), cardiac output (CO; cZ method) and total peripheral resistance (TPR) were measured. The subjects repeated 8 trials, intermitted by more than 5‐min rest. In 4 trials randomly selected from 8 trials, the onset of exercise was signaled by a 30‐sec CD, whereas in the remaining 4 trials, exercise was started without CD. We found that CD increased CBF, HR, CO, mean blood pressure, and VO2 sequentially, decreasing TPR with increased StO2. To assess efferent signals causing vasodilation and the effects of posture change from the semi‐recumbent to supine position, other groups of subjects underwent the same exercise protocol but using only right leg in the semi‐recumbent (n=10) or supine (n=8) positions while muscle sympathetic nerve activity (MSNA; microneurography) and StO2 were measured in the left and right leg, respectively. We found that CD decreased MSNA burst frequency and total MSNA (both, P&lt;0.05), which were significantly correlated with the increase in StO2 (both, P&lt;0.001). However, these responses to CD were nearly abolished by the postural change. Thus, CD before starting voluntary exercise induced cerebro‐cardiovascular responses from central system to effector organs in a sequential manner in the semi‐recumbent position, but these responses were minimized while in the supine position.Support or Funding InformationThis study was supported by grants from the Japan Society for the Promotion of Science (24689014 and 15H04680).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Dynamic Cerebral Autoregulation Impairment Persists Past Resolution of Symptoms in Collegiate Athletes Following Concussion

ObjectivesDespite 3.8 million concussions occurring annually in the United States, the pathophysiological sequelae of the injury are still poorly understood. Animal and human studies have consistently reported deficits in cerebral blood flow (CBF) following concussion suggesting impairments in CBF regulation. Reductions in CBF are also associated with functional outcomes. The purpose of the study was to examine dynamic cerebral autoregulation (dCA) in an ongoing prospective cohort of collegiate athletes 3 days, 21 days, and 90 days following a concussion and compare them with non‐injured controls.Materials and MethodsTwenty‐seven NCAA and recreational athletes (20±1 years) with a physician diagnosed sports‐related concussions were enrolled in the study. For the injured athletes, data was collected on days 3,21, and 90 following concussion. Twenty‐five age and sports matched non‐injured controls (20±1 years) were also enrolled. For non‐injured controls, data was collected at one time point. Symptom number and severity was measured using the Sports Concussion Assessment Tool (SCAT‐3). Depression scores were assessed with Patient Health Questionnaire‐9 (PHQ‐9). Continuous mean arterial blood pressure (MBP) was obtained with finger photoplethysmography and middle cerebral artery blood flow velocity (MCAV) was obtained with a 2 MHz transcranial Doppler ultrasonography while subjects were seated in an upright position. dCA was estimated from transfer function (Tf) analysis of beat‐to‐beat spontaneous fluctuations in MBP and MCAV within the low (LF, 0.07–0.20 Hz) and high (HF, 0.20–0.35 Hz) frequency ranges. Effective dCA would attenuate spontaneous changes in MCAV in response to variations in MBP, which would correspond to relatively low transfer function gain. Independent and paired t‐tests were used to compare dCA between days 3, 21, and 90 following concussion with the non‐injured controls.ResultsCompare to the controls, concussed athletes exhibited greater symptom number on day‐3 (12.2±6.8 vs. 2.4±3.4; p&lt;0.001) and higher PHQ‐9 score (8.7±5.6 vs. 2.1±2.1; p&lt;0.001). LF Tf gain was higher on day‐3 (1.26±0.34U vs. 1.04±0.28U; p=0.016) compared to the controls. LF Tf gain continued to be high on day‐21 (1.30±0.45U; p=0.025) compared to the non‐injured controls despite no differences in symptoms number or depression scores between the groups. LF Tf gain was comparable to the controls on day‐90.ConclusionsDynamic cerebral autoregulation appears to be impaired at least up to 21 days following concussion despite improvement in symptom and depression. Cerebral autoregulation estimated from transcranial Doppler ultrasonography may be useful as a potential vascular biomarker for return‐to‐play decisions following a concussion preventing the risk of second‐impact syndrome.Support or Funding InformationThis work was supported by SMU University Research Council Grant, Spring 2015 &amp; Texas Institute for Brain Injury and Repair (TIBIR) Pilot Grant 2016.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Lactotripeptide ingestion increases cerebral blood flow velocity in middle-aged and older adults

The age-related decrease in cerebral blood flow velocity increases the risk of cerebrovascular disease. Milk protein-derived bioactive peptides, e.g., lactotripeptide (LTP), have been shown to inhibit angiotensin converting enzyme activities and increase vasodilator production. We hypothesized that LTP ingestion increases cerebral blood flow velocity in middle-aged and older adults. In a randomized, placebo-controlled, double-blind design, 15 healthy middle-aged and older adults were assigned to either a LTP group or a placebo group. The subjects ingested LTP or placebo orally for 8 weeks. Before and after intervention, middle cerebral blood flow velocity was measured using transcranial Doppler ultrasonography. The baseline middle cerebral blood flow velocity and most other key dependent variables did not differ between the groups. LTP ingestion significantly increased middle cerebral blood flow velocity, but there was no such improvement in the placebo groups. We concluded that 8 weeks of LTP ingestion increased middle cerebral blood flow velocity in middle-aged and older adults.

Whole blood viscosity and cerebral blood flow velocities in obese hypertensive or obese normotensive adolescents.

Obesity affects all major organ systems and leads to increased morbidity and mortality. Whole blood viscosity is an important independent regulator of cerebral blood flow. The aim of the present study was to evaluate the effect of whole blood viscosity on cerebral artery blood flow velocities using transcranial Doppler ultrasound in pediatric patients with obesity compared to healthy controls and analyze the effect of whole blood viscosity and blood pressure status to the cerebral artery blood flow velocities. Sixty patients with obesity diagnosed according to their body mass index (BMI) percentiles aged 13-18 years old were prospectively enrolled. They were grouped as hypertensive or normotensive according to their ambulatory blood pressure monitoring. Whole blood viscosity and middle cerebral artery velocities by transcranial Doppler ultrasound were studied and compared to 20 healthy same aged controls. Whole blood viscosity values in hypertensive (0.0619±0.0077 poise) and normotensive (0.0607±0.0071 poise) groups were higher than controls (0.0616±0.0064 poise), with no significance. Middle cerebral artery blood flow velocities were higher in the obese hypertensive (73.9±15.0 cm/s) and obese normotensive groups (75.2±13.5 cm/s) than controls (66.4±11.5 cm/s), but with no statistical significance. Physiological changes in blood viscosity and changes in blood pressure did not seem to have any direct effect on cerebral blood flow velocities, the reason might be that the cerebral circulation is capable of adaptively modulating itself to changes to maintain a uniform cerebral blood flow.

Increased middle cerebral artery mean blood flow velocity index after stroke thrombectomy indicates increased risk for intracranial hemorrhage

Background and purposeCerebral hyperperfusion has been related to the risk of intracranial hemorrhage (ICH) in stroke patients after vessel recanalization therapy. We hypothesized that after successful mechanical thrombectomy for acute...

Compression garments and cerebral blood flow: Influence on cognitive and exercise performance

This study aimed to describe the effect of compression garments on middle cerebral artery blood flow velocity (MCAv) in relation to cognitive and exercise performance whilst cycling. In a randomised-controlled-cross-over design, 15 well-trained male cyclists were recruited to participate in three identical trials wearing loose fitting shorts (control), low-grade, or medium-grade compression garments. The protocol involved four 8 min increments of cycling at 30%, 50%, 70%, and 85% maximal power output and a 4 km time-trial. Participants undertook a cognitive Stroop task at baseline and at the midpoint of each increment. MCAv was monitored with Transcranial Doppler Ultrasonography. Mean arterial pressure (MAP) and partial pressure of end-tidal CO2 (PetCO2) were measured throughout. MCAv, MAP, PetCO2, and reaction time of the complex Stroop task were influenced by exercise intensity, but not compression garments. Compression garments significantly affected cognitive accuracy in the complex Stroop task such that low-grade compression appeared to enhance cognitive accuracy in comparison to the control condition at the highest intensity (p = .010). Time-trial performance did not differ between the control (338.0 ± 17.3 s), low-grade (338.7 ± 18.7 s), or medium-grade (342.2 ± 19.3 s) conditions (p = .114). Compression garments did not affect MCAv during exercise or time-trial performance, but compression may be beneficial for improved cognitive accuracy during high-intensity exercise. Further research is required to elucidate the potential impact on cognitive performance.