Plasma viscosity regulates systemic and microvascular perfusion during acute extreme anemic conditions
ABSTRACT The hamster window chamber model was used to study systemic and microvascular hemodynamic responses to extreme hemodilution with low- and high-viscosity plasma expanders (LVPE and HVPE, respectively) to determine whether plasma viscosity is a factor in homeostasis during extreme anemic conditions. Moderated hemodilution was induced by two isovolemic steps performed with 6% 70-kDa dextran until systemic hematocrit (Hct) was reduced to 18% (level 2). In a third isovolemic step, hemodilution with LVPE (6% 70-kDa dextran, 2.8 cP) or HVPE (6% 500-kDa dextran, 5.9 cP) reduced Hct to 11%. Systemic parameters, cardiac output (CO), organ flow distribution, microhemodynamics, and functional capillary density, were measured after each exchange dilution. Fluorescent-labeled microspheres were used to measure organ (brain, heart, kidney, liver, lung, and spleen) and window chamber blood flow. Final blood and plasma viscosities after the entire protocol were 2.1 and 1.4 cP, respectively, for LVPE and 2.8 and 2.2 cP, respectively, for HVPE (baseline = 4.2 and 1.2 cP, respectively). HVPE significantly elevated mean arterial pressure and CO compared with LVPE but did not increase vascular resistance. Functional capillary density was significantly higher for HVPE [87% (SD 7) of baseline] than for LVPE [42% (SD 11) of baseline]. Increases in mean arterial blood pressure, CO, and shear stress-mediated factors could be responsible for maintaining organ and microvascular perfusion after exchange with HVPE compared with LVPE. Microhemodynamic data corresponded to microsphere-measured perfusion data in vital organs.
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ABSTRACT: Polypropylene has been compounded with a commercial organoclay both in the absence and in the presence of hydrogenated oligo(cyclopentadiene) (HOCP) as a compatibiliser. The characteristics and the properties of the nanocomposites were evaluated and compared. HOCP favours the intercalation of the polypropylene in the organoclay galleries and enables a more homogeneous dispersion of the nanoclay throughout the polymer matrix. In the compatibilised nanocomposite, the diluent effect ascribed to the HOCP component is associated with the nucleating action of the nanoclay, resulting in the development of the β-crystalline form of the polypropylene. The presence of HOCP preserves the molecular weight of the polymer during the processing and gives good overall mechanical properties to the compatibilised nanocomposite. The thermo-oxidative degradation of the polypropylene is strongly delayed in the compatibilised nanocomposite.Polymer Degradation and Stability 01/2012; 97(1). DOI:10.1016/j.polymdegradstab.2011.10.007 · 2.63 Impact Factor
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ABSTRACT: L’anémie est une complication fréquente chez les patients cérébrolésés. Elle est souvent considérée comme un facteur aggravant le développement de lésions cérébrales secondaires. Néanmoins, le niveau optimal d’hémoglobine à maintenir dans ce contexte est actuellement inconnu, et les effets des transfusions de globules rouges chez les patients atteints de traumatisme crânien grave, d’hémorragie sousarachnoïdienne ou d’accident vasculaire cérébral sont discutés: ils peuvent améliorer le transport local d’oxygène mais aussi être grevés de différentes complications. Le but de cette revue est de décrire les connaissances actuelles dans le domaine de l’anémie et des transfusions chez le patient cérébrolésé.Réanimation 11/2013; 22(6). DOI:10.1007/s13546-013-0728-1
Conference Paper: Randomized Hough transform: better ellipse detection[Show abstract] [Hide abstract]
ABSTRACT: Standard methods of ellipse detection are slow and memory intensive. We present a new algorithm using the randomized Hough transform. The algorithm is demonstrated on both synthetic images and simple real-world images. It is found to be fast, memory efficient and accurate with images containing multiple ellipses and noiseTENCON '96. Proceedings. 1996 IEEE TENCON. Digital Signal Processing Applications; 12/1996