Biomedical subjects

L Pourcelot

Publications and source records attributed to L Pourcelot.

152 records · Page 9Linked to original sources

PubMedDate not supplied

Effects of indomethacin on cerebral hemodynamics at rest and during endotracheal suctioning in preterm neonates.

The effect of therapeutic doses of indomethacin versus placebo (saline) on cerebral hemodynamics was studied in nine mechanically ventilated preterm infants. Recordings were made at rest and during endotracheal suctioning. Indomethacin at a dose of 0.2 mg/kg body weight was infused over 5 min. Compared to placebo, there was a significant decrease in Doppler mean frequency in the anterior cerebral artery within minutes of starting the indomethacin infusion during the resting period after the first (p less than 0.01), second (p less than 0.001) and third (p less than 0.025) doses. This effect has persisted during endotracheal suctioning. Thus, indomethacin alters cerebral hemodynamics by decreasing Doppler mean frequency. In view of these findings, and particularly because of the alteration in the resting cerebral hemodynamics, the recommendation of prophylactic treatment with indomethacin remains questionable.

Blood Flow Velocity↗

PubMedDate not supplied

Cardiac cycle-dependent alternating flow in vertebral arteries with subclavian artery stenoses.

Continuous-wave Doppler sonography is a reliable method for detecting severe subclavian stenosis and occlusion as well as subclavian steal. Intermediate stages leading to subclavian steal can also be detected. These are characterized by a cardiac-phase-dependent alternating flow direction in the vertebral artery. Some cases of proximal subclavian or proximal vertebral artery stenosis produce a systolic deceleration of flow in the vertebral artery. Stenosis and occlusion of the subclavian artery as well as stenosis of the subclavian and vertebral arteries can be distinguished. The pulse curve changes described can be reversed by a vascular by-pass. Alternating flow direction or systolic deceleration of flow in the radial artery could also be observed or induced in a iatrogenic model using Cimino's a-v fistula in the arm in patients on dialysis. The results in beginning subclavian steal situations can be applied in principle to other collateral circulations, and in particular to the hemodynamics in the region of watersheds.

Arterial Occlusive Diseases↗

PubMedDate not supplied

Ultrasound characterization and quantification of carotid atherosclerosis lesions.

The development of ultrasonography in vascular applications has entailed research of ultrasound parameters leading to precise the diagnosis and quantification of carotid lesions in routine. The use of recent colour Doppler imaging techniques (velocity or power encoding) is recommended as they allow a better definition of the lesions and recesses. At present, features of plaque that could be related to increased incidence of stroke are: echogenicity, with a more frequent observation of anechoic or hypoechoic lesions in the case of clinical signs; texture, with frequent haemorrhage; surface contour, with a high rate of ulcerations which were accompanied by stroke; plaque motion, with a significant alteration in plaque motility in symptomatic patients; progression or regression in size, with a faster progression of anechoic and hypoechoic plaques; an increase in plaque volume is associated with a greater risk of stroke; a significant relationship between the presence of "ulcers" and embolic activity. The quantification of stenosis degree could be made using velocity criteria and/or morphological criteria. Velocity criteria could be obtained at the site of the stenosis (direct criteria) or downstream the carotid stenosis using Duplex systems. Morphological criteria could be obtained using B-mode imaging or colour Doppler but this quantification remains difficult in case of diffuse carotid stenoses or very severe stenoses.

Arteriosclerosis↗

PubMedDate not supplied

Doppler spectrum analysis and vascular imaging in the diagnosis of extracranial carotid artery disease.

Ultrasound methods are well suited for the exploration of the carotid system. High resolution echography can visualize atheromatous defects on the vessels walls with a resolution better than one mm, whereas Doppler examination detects haemodynamic disturbances due to these plaques. Conventional Doppler examination can reveal moderate or severe stenosis (greater than 60%); the recent development of frequency analysis of the Doppler audio signal makes now possible the detection of very light haemodynamic disturbances due to low grade stenosis even as small as 15%. Spectral distribution abnormalities have been classified in four grades according to their amplitude. The combination of the morphological and functional data provided by echography and Doppler spectrum analysis has drastically increased the diagnostic possibilities of the ultrasound methods in the field of the extracranial vascular pathology. With a new duplex system which combines echography and C.W. Doppler examination (duplex probe) it is possible to detect, and quantify carotid stenosis (in percentage of the lumen reduction), and to evaluate blood flow volume in ml/mn.

Carotid Artery Diseases↗

PubMedDate not supplied