BACKGROUND AND PURPOSE: External counterpulsation (ECP) is a noninvasive method used to enhance cerebral perfusion by elevating the blood pressure in ischemic stroke. However, the response of the beat-to-beat blood pressure variability (BPV) in ischemic stroke patients during ECP remains unknown. METHODS: We enrolled recent ischemic stroke patients and healthy controls. Changes in the blood flow velocities in bilateral middle cerebral arteries and the continuous beat-to-beat blood pressure before, during, and after ECP were monitored. Power spectral analysis revealed that the BPV included oscillations at very low frequency (VLF; <0.04 Hz), low frequency (LF; 0.04-0.15 Hz), and high frequency (HF; 0.15-0.40 Hz), and the total power spectral density (TP; <0.40 Hz) and LF/HF ratio were calculated. RESULTS: We found that ECP significantly increased the systolic and diastolic blood pressures in both stroke patients and controls. ECP decreased markedly the systolic and diastolic BPVs at VLF and LF and the TP, and the diastolic BPV at HF when compared with baseline. The decreases in diastolic and systolic BPV reached 37.56% and 23.20%, respectively, at VLF, 21.15% and 12.19% at LF, 8.76% and 16.59% at HF, and 31.92% and 23.62% for the total TP in stroke patients, which did not differ from those in healthy controls. The change in flow velocity on the contralateral side was positively correlated with the total TP systolic BPV change induced by ECP (r=0.312, p=0.035). CONCLUSIONS: ECP reduces the beat-to-beat BPV when increasing the blood pressure and cerebral blood flow velocity in ischemic stroke patients. ECP might be able to improve the clinical outcome by decreasing the beat-to-beat BPV in stroke patients, and this should be explored further in future studies.
Blood Flow Velocity ; Blood Pressure* ; Cerebrovascular Circulation* ; Counterpulsation* ; Humans ; Methods ; Middle Cerebral Artery ; Perfusion ; Stroke*

Utilizing the third-order polynomial curve fitted to the experimental data, which represents the relationship between cerebral blood flow (CBF) and mean artery blood pressure (MABP), we constructed a lumped-parameter dynamic model with 5 elements. In this model; the resistance is not constants it is determined by the fitted curve. We simulated the process of CBF autoregulation numerically by solving the govern equation of this model and got quite accurate results. Furthermore, we studied the influence of hemodynamic parameters on the CBF autoregulation by this model and proved that the characteristic resistance is the most important factor.
Blood Flow Velocity ; Blood Pressure ; physiology ; Cerebrovascular Circulation ; physiology ; Homeostasis ; Humans ; Hypotension ; physiopathology ; Models, Biological ; Oxygen ; metabolism ; Regional Blood Flow

This study was performed to examine the influence of isoflurane anesthesia on the pulsatility index (PI) and the peak systolic velocity (PSV) of the blood flow in the basilar artery of dogs by duplex Doppler ultrasonography. Twelve healthy dogs were used to measure the PI and the PSV under the conscious state and isoflurane anesthesia. The pulsatility index (PI) and the peak systolic velocity (PSV) in the basilar artery were measured five times with random intervals. The blood pressure was measured. The PI and PSV values in dogs under isoflurane anesthesia were 1.37 +/- 0.32 and 72 +/- 19 cm/sec, whereas those in the conscious dogs were 1.37 +/- 0.13 and 81 +/- 16 cm/sec, respectively. The indirect mean arterial systolic and diastolic pressures under isoflurane anesthesia were 107 and 51 mmHg, whereas those in the conscious dogs were 133 and 74 mmHg. Though the isoflurane is generally known to induce hypotension, there were no significant differences in the PI and PSV between the isoflurane-anesthetized and the conscious dogs. In conclusion, the isoflurane anesthesia did not influence the PI and PSV in the basilar artery of dogs.
Anesthetics, Inhalation/*pharmacology ; Animals ; Basilar Artery/drug effects/*ultrasonography ; Blood Flow Velocity/drug effects/veterinary ; Blood Pressure/drug effects ; Cerebrovascular Circulation/drug effects ; Dogs/*physiology ; Female ; Isoflurane/*pharmacology ; Male ; Pulsatile Flow/drug effects ; Ultrasonography, Doppler, Duplex/veterinary

BACKGROUND: Melatonin has been shown to attenuate the reflex sympathetic increases that arise in response to orthostatic challenges. We tested the hypothesis that the attenuated sympathetic increase induced by melatonin premedication may weaken the arterial blood pressure (ABP) preserving the capability during acute hypotension, thereby altering dynamic cerebral autoregulation and causing a further decrease in cerebral blood flow (CBF). METHODS: Acute hypotension was induced in 12 healthy subjects by releasing bilateral thigh cuffs before and after an oral dose of melatonin (0.2 mg/kg). Heart rate (HR), arterial blood pressure (ABP), Modelflow estimate of cardiac output (CO), total peripheral resistance (TPR) and cerebral blood flow velocity (CBFV) by transcranial Doppler were measured. RESULTS: Steady state HR, the mean arterial pressure and CBFV were not altered 60 minutes after melatonin ingestion. Reduced systolic arterial pressure (DeltaSAP), changes in HR (DeltaHR), CO (DeltaCO), and TPR (DeltaTPR), DeltaHR/DeltaSAP and percentage restoration of SAP were not affected after a temporal decrease in ABP induced by thigh cuff release. In the cerebral circulation, melatonin did not affect changes in CBFV, cerebrovascular resistance index, the rate of regulation and percentage restoration of CBFV following a sudden decrease in ABP. CONCLUSIONS: Contrary to our hypothesis, melatonin did not affect the rapid vasodilatory and recovery responses of cardiovascular and dynamic cerebral autoregulation. These results suggest that melatonin premedication may not impair ABP and CBF preserving capability induced by sudden postural changes or hemorrhage.
Arterial Pressure ; Blood Flow Velocity ; Blood Pressure ; Cardiac Output ; Cerebrovascular Circulation ; Eating ; Heart Rate ; Hemorrhage ; Homeostasis ; Humans ; Hypotension ; Male ; Melatonin ; Premedication ; Reflex ; Thigh ; Vascular Resistance

OBJECTIVETo observe the three-dimensional distribution of vessels, and to establish a new method for measurement of blood flow velocity in mice cerebral cortex using two-photon laser scanning microscopy and fluorescence probe labeling technique.

METHODSThe mouse was made cranial window surgery and injected Texas-Red through tail vein after anesthetized. The three-dimensional imaging of vessel was obtained through z-stack scanning, and blood flow velocity was quantified through line scanning.

RESULTSWe could detect vascular distribution for more than 500 µm depth using two-photon microscopy. The velocity of blood flow was (0.59 ± 0.12) mm/s in capillary.

CONCLUSIONThe method for observing the brain blood flow by two-photon microscopy was established, which could achieve quantification of single vascular blood flow velocity and provide experimental evidence for basic research and medical applications.

Animals ; Blood Flow Velocity ; Brain ; blood supply ; Capillaries ; Cerebrovascular Circulation ; Fluorescent Dyes ; Hemodynamics ; Mice ; Microscopy, Fluorescence

OBJECTIVETo evaluate the changes of cerebral blood flow (CBF) with real-time contrast-enhanced ultrasound (CEU) in a canine model of acute cerebral ischemia.

METHODSCerebral perfusion was assessed in 6 dogs subjected to craniotomy with CEU at the time of 0, 30, 60, 90 and 120 min after occlusion of the left common carotid artery (LCCA). The microvascular volume (A) and blood flow velocity (beta) in the brain were measured from the time-versus-acoustic intensity plots, and the value of Axbeta were calculated. 99mTc-ECD brain single photon emission computed tomography (SPECT) was performed on the day before the experiment and at 120 min after LCCA occlusion. The radioactive counts on both sides of the cerebral cortex were calculated.

RESULTSA significant correlation was found between Axbeta from CEU and volume of the blood flow of the CCA from Doppler flowmetry. A, beta and Axbeta values varied significantly between the different time points (P>0.001). The ipsilateral hemisphere showed a low-perfusion state while the contralateral hemisphere showed a high-perfusion state immediately after the occlusion.

CONCLUSIONSThe changes of beta is the main regulation mechanism during acute cerebral ischemia in dogs.

Animals ; Blood Flow Velocity ; Brain ; blood supply ; Brain Ischemia ; diagnostic imaging ; Cerebrovascular Circulation ; Dogs ; Male ; Regional Blood Flow ; Ultrasonography

OBJECTIVETo investigate the effect of nasal cavity expansion surgery on the abnormal blood supply of the cerebral arterial system.

METHODSFifty-nine inpatients with abnormal blood supply of cerebral arterial system confirmed by transcranial doppler (TCD) and chronic nasal obstructive diseases were included in this study. All patients accepted nasal cavity expansion surgery and were followed-up with TCD every month after operation until TCD became normal, or up to seven months even if the TCD was still abnormal. SPSS 17.0 software was used to analyze the data.

RESULTSIn all 59 patients, there were 164 TCD-abnormal cerebral arteries. Among them, 37 patients(62.71%) with abnormal TCD arteries became normal within 1 to 7 months after operation, 8 patients (13.56 %) got better, but 14 patients (23.73 %) did not improve.

CONCLUSIONSAbnormal blood flow of some cerebral arteries was possibly induced by increasing the activation of sympathetic nervous system around the vertebral arterial system, caused by chronic nasal obstruction. Nasal dilatancy surgery can improve the blood supplement of the cerebral arterial system.

Blood Flow Velocity ; Cerebral Arteries ; Cerebrovascular Circulation ; Humans ; Nasal Cavity ; Ultrasonography, Doppler, Transcranial

The methods for measurement of blood flow contain dilution, electro-magnetism, nuclear magnetic resonance, Doppler etc. The dilution, which includes heat dilution, 131Xe, etc., can not display the moving blood flow in real-time. The expenses of nuclear magnetic resonance expenses are very high. Electromagnetism must be used in the surgical operation. And ultrasound Doppler can not record other parameters of hemodynamics synchronously. This paper brings up a kind of blood flow measuring method with simple operating rules, dependable performance, and low cost to meet the needs in hemodynamic studies. The differential pressure between stay and fluxion points of the tube is produced in proportion to the square of velocity while fluid flows through the tube. We not only measure blood pressure or transfer drug using the detention catheter with double chamber, but also detect the differential pressure related within blood flow. The result of detecting cerebral blood flow (CBF) in clinical setting shows this method can record the diagram of dynamic blood flow and is a valid was of detecting blood flow for hemodynamic studies.
Blood Flow Velocity ; Cerebrovascular Circulation ; physiology ; Equipment Design ; Hemorheology ; instrumentation ; methods ; Humans ; Middle Aged ; Monitoring, Intraoperative

By using Doppler sensor and pressure sensor, the cerebrovascular stroke detector can be used to measure the blood flow velocity and blood pressure of the carotid artery. In this study, a variety of signal conversion and isolation processing techniques are proposed for processing and feature extraction of the output signals from the sensors. Finally, effective signal output waveforms that can be used to evaluate the cerebrovascular hemodynamics index (CVHI) are obtained, and the sound signal outputs that can reflect the change characteristics of blood flow velocity and blood pressure signals are generated, which realizes the application functional requirements of the detector.
Blood Flow Velocity/physiology* ; Cerebrovascular Circulation/physiology* ; Hemodynamics/physiology* ; Humans ; Stroke ; Technology

Sympathetic neuronal activity is primarily responsible for the neurogenic control of cerebral autoregulation. The stimulation of sympathetic nerves causes both large arterial constriction and small vessel dilation in experimental animals. However, the role of the sympathetic nervous system in the control of cerebral hemodynamics has yet to be clarified in humans. In order to assess the effect of sympathetic activation on human cerebral hemodynamics, we performed a simultaneous transcranial Doppler (TCD) monitoring of bilateral middle cerebral arterial flow velocity in 16 healthy male volunteers (mean age 26) during well-known sympathetic activation measures such as isometric hand-grip exercise (IHE) and cold pressor test (CPT). Blood pressure was checked manually before and at each minute during tests. The mean arterial pressure (MAP) was calculated as (systolic pressure + 2 X diastolic pressure)/3. There was a significant increase in MCA flow velocities during both sympathetic activation tests. The percent increase of diastolic velocity (36% with IHE and 24% with CPT) was significantly higher than systolic velocity (21% with IHE and 9% with CPT). The pulsatility index was significantly decreased during the tests (from 0.75 to 0.58 with IHE and from 0.81 to 0.63 with CPT). These results suggest that sympathetic activation increases MCA flow velocities, related with a reduction in small vessel resistance and/or a constriction of large arteries.
Adult ; Blood Flow Velocity ; Carbon Dioxide/blood ; Cerebral Arteries/physiology* ; Cerebrovascular Circulation* ; Hemodynamics ; Human ; Male ; Sympathetic Nervous System/physiology*