PubMed · 929823
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Z M Vucicevic, L Russo. New Doppler machine.. https://pubmed.ncbi.nlm.nih.gov/929823/
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We show that many salient hemodynamic flow properties, which have been difficult or impossible to assess in microvessels in vivo, can be estimated by using microviscometry and fluorescent microparticle image velocimetry in microvessels >20 microm in diameter. Radial distributions in blood viscosity, shear stress, and shear rate are obtained and used to predict axial pressure gradient, apparent viscosity, and endothelial-cell surface-layer thickness in vivo. Based solely on microparticle image velocimetry data, which are readily obtainable during the course of most intravital microscopy protocols from systemically injected particle tracers, we show that the microviscometric method consistently predicted a reduction in local and apparent blood viscosity after isovolemic hemodilution. Among its clinical applications, hemodilution is a procedure that is used to treat various pathologies that require reduction in peripheral vascular-flow resistance. Our results are directly relevant in this context because they suggest that the fractional decrease in systemic hematocrit is approximately 25-35% greater than the accompanying fractional decrease in microvascular-flow resistance in vivo. In terms of its fundamental usefulness, the microviscometric method provides a comprehensive quantitative analysis of microvascular hemodynamics that has applications in broad areas of medicine and physiology and is particularly relevant to quantitative studies of angiogenesis, tumor growth, leukocyte adhesion, vascular-flow resistance, tissue perfusion, and endothelial-cell mechanotransduction.
BACKGROUND: Changes in renal arterial Doppler flow may identify parenchymal disease, but in newborns knowledge of normal physiological parameters is a prerequisite for correct interpretation. OBJECTIVE: To evaluate renal blood flow in healthy newborns by means of Doppler US. MATERIALS AND METHODS: On the fourth day of life we examined 100 normal term newborn infants (200 kidneys). Blood flow in the central renal arteries was compared with that in the intraparenchymal arteries. Maximum systolic velocity ( V(max)), end-diastolic velocity ( V(ed)), mean flow velocity ( V(mean)), resistive index (RI) and pulsatility index (PI) were assessed. RESULTS: All parameters were significantly higher in the central renal arteries than in the intraparenchymal arteries (RI 0.78+/-0.07 vs 0.62+/-0.05, P<0.0001; PI 1.84+/-0.52 vs 1.09+/-0.18, P<0.0001). CONCLUSIONS: Physiological data are presented that are necessary for the correct interpretation of neonatal Doppler US.
OBJECTIVE: To examine the relationship between fetal biophysical profile (FBP), Doppler cerebro-umbilical (C/U) ratio and neonatal neurosonography in growth restricted newborns. STUDY DESIGN: This prospective study included 87 growth restricted fetuses from 28 to 42 weeks of gestation. The FBP and C/U ratio were assessed twice a week. Within 48h and on the seventh day after birth, neonatal neurosonography was performed as the outcome parameter. RESULTS: Brain damage was detected, by neurosonography, in 34 newborns with intrauterine growth restriction (IUGR). Severe periventricular echodensities (PVE) were ultrasonographically verified in eleven infants. Intraventricular or intraparenchymal hemorrhage (severe intracranial hemorrhage ICH) was detected in seven infants, and subependymal hemorrhage (SEH) in nine infants with IUGR. Porencephalic cysts, as a result of chronic intrauterine hypoxia, were found in four infants, and brain atrophy was detected in one case. Nonspecific ultrasonographic changes were observed in two newborns. The FBP and C/U ratio were statistically significantly associated with neurosonographicaly verified neonatal brain lesions (P < 0.001). CONCLUSIONS: The FBP and the C/U ratio represent the useful indicators for early detection and assessment of fetal hypoxia. They may also be parameters for the prediction of neonatal neurosonography findings in newborns with IUGR.