Time-averaged Blood Flow Velocity Research Articles

Remodeling of extracranial veins and venous-arterial imbalance in extrinsic stenosis and hypoplasia of the internal jugular veins

The aim of the study was to compare hemodynamic parameters, the sequence of remodeling of the jugular and extrajugular outflow tracts of cerebral venous circulation in extrinsic stenosis and hypoplasia of the internal jugular vein (IJV). Material and methods. Groups with external compression and IJV stenosis (n = 50), with IJV hypoplasia (n = 27), and after IJV ligation/resection (n = 6) as a model of IJV occlusion with a minimal cerebral venous insufficiency and venous encephalopathy and control group (n = 31) were compared. All patients underwent a neurological examination, ultrasound duplex scanning of the IJV (J2 and at the level of stenosis), common carotid and vertebral artery (V2), 2DToF or 3DToF magnetic resonance venography of the neck veins. The degree of stenosis of the IJV, the crosssectional area and the time average blood flow velocity, the calculated indicator of the venous-arterial balance (VAB) were determined according to the modified formula. Results and discussion. In the group of external compression of the IJV, stenosis averaged 64.52 %. The area of the IJV at the site of stenosis was 6 times, and at the standard place (J2) – 3 times less than the area of the opposite IJV. The hypoplastic IJV throughout its entire length (from J1 to J3) had the same area (0.21 ± 0.12 cm2 ), smooth contours, without local expansions or narrowings. A very low blood flow velocity (10.2 ± 11.67 cm/s) is characteristic for stenosis, in contrast to the normal velocity in the hypoplastic vein and in the control group. The blood flow velocity in the contralateral IJV with external stenosis does not differ from normal, but it is increased with hypoplasia (34.62 ± 12.23 cm/s). With MR venography, it is possible to detect a stenosing factor, symptoms of a filling defect, a decrease or loss of a blood flow signal, and an assessment of the overall picture of remodeling of the venous network of the neck. A decrease in the IJV area on the side of the lesion/anomaly corresponds to negative remodeling, while an expansion of the opposite IJV corresponds to positive remodeling. If the obstruction persists, the homolateral, then the contralateral external jugular vein expands, then the vertebral veins and plexuses, spinal epidural veins, anterior jugular and posterior cervical veins expand too. The magnitude of the IJV on the side of the anomaly/pathology with hypoplasia did not differ from the value with stenosis (9 %), but was slightly less than on the opposite IJV (53.39 ± 13.40 and 67.24 ± 18.02 %, respectively, p < 0.06) and significantly less compared to the control (24.16 ± 8.06 % on the left and 33.15 ± 8.27 % on the right, p < 0.0001), which makes this indicator a good additional criterion for outflow abnormality according to the IJV of one side.

Hands-free continuous carotid Doppler ultrasound for detection of the pulse during cardiac arrest in a porcine model

Background/PurposePulse palpation is an unreliable method for diagnosing cardiac arrest. To address this limitation, continuous hemodynamic monitoring may be a viable solution. Therefore, we developed a novel, hands-free Doppler system, RescueDoppler, to detect the pulse continuously in the carotid artery. MethodsIn twelve pigs, we evaluated RescueDoppleŕs potential to measure blood flow velocity in three situations where pulse palpation of the carotid artery was insufficient: (1) systolic blood pressure below 60 mmHg, (2) ventricular fibrillation (VF) and (3) pulseless electrical activity (PEA). (1) Low blood pressure was induced using a Fogarty balloon catheter to occlude the inferior vena cava. (2) An implantable cardioverter-defibrillator induced VF. (3) Myocardial infarction after microembolization of the left coronary artery caused True-PEA. Invasive blood pressure was measured in the contralateral carotid artery. Time-averaged blood flow velocity (TAV) in the carotid artery was related to mean arterial pressure (MAP) in a linear mixed model. ResultsRescueDoppler identified pulsatile blood flow in 41/41 events with systolic blood pressure below 60 mmHg, with lowest blood pressure of 19 mmHg. In addition the absence of spontaneous circulation was identified in 21/21 VF events and true PEA in 2/2 events. The intraclass correlation coefficient within animals for TAV and MAP was 0.94 (95% CI. 0.85–0.98). ConclusionsIn a porcine model, RescueDoppler reliably identified pulsative blood flow with blood pressures below 60 mmHg. During VF and PEA, circulatory arrest was rapidly and accurately demonstrated. RescueDoppler could potentially replace unreliable pulse palpation during cardiac arrest and cardiopulmonary resuscitation.

Cardiovascular effects of fentanyl and propofol on hemodynamic function in rabbits

To evaluate short-term cardiovascular effects after IV administration of boluses of fentanyl in rabbits. 6 healthy New Zealand White rabbits. Each rabbit was anesthetized with propofol (4.0 to 8.0 mg/kg, IV); anesthesia was maintained by administration of propofol (1.2 to 1.3 mg/kg/min, IV). Subsequently, 3 injections of fentanyl (0.0053 mg/kg) were administered. Before and for 10 minutes after injections, the following variables were measured: vessel diameter, peak systolic blood flow velocity, minimum diastolic blood flow velocity, end-diastolic blood flow velocity, time-average blood flow velocity, mean volumetric flow (VFmean), resistance index (RI), and pulsatility index for the left common carotid artery after the first injection and abdominal aorta after the third injection; mean arterial pressure (MAP); heart rate (HR); arterial oxygen saturation; end-tidal partial pressure of carbon dioxide; and body temperature. Echocardiography was performed after the second injection. Fentanyl injections caused a transient and significant decrease in diameter and VFmean of the abdominal aorta and end-diastolic blood flow velocity of the left common carotid artery and an increase in peak systolic blood flow velocity and RI of the left common carotid artery. Also, MAP, HR, and body temperature decreased significantly after injections. Fentanyl injections induced a short-term decrease of vessel diameter in the abdominal aorta and increased resistance in the distal distribution area of the left common carotid artery. Results revealed decreases in MAP, HR, and body temperature, with an increasing effect after the third bolus injection, which indicated a cumulative drug effect.