Fractional vascular volume

The determination of cerebral perfusion using CTP is based on examining the relationships between the arterial, tissue, and the venous enhancement. More specifically, tracer kinetic theory states that if one knows the input and the output of a tracer from a voxel, one can determine the volume of distribution (i.e., fractional vascular volume) and the clearance rate (i.e., flow per unit tissue volume) [20, 114, 115]. The fractional vascular volume,/, is defined by the following equation ... 

Ad. 3. Manipulation of intra-f extra-cellular ration. Le Rumear et al24 manipulated intra-/extra-cellular ratios and showed that an increase in vascular volume induced by nerve stimulation increased the fraction of the slow relaxation component, while reduced intra-cellular/interstitial volume induced by osmotic diuresis decreased the fraction of the fast relaxing component and increased the fraction of the slow relaxing component, which indicates that the fast and slow relaxing component can be ascribed to the intra- and extra-cellular space, respectively. 

Riviere et aL (1995) studied the toxicokinetics of topically administered C-sulfur mustard in their isolated perfused porcine skin flap (IPPSF) model to support the correlation between eritical steps in the vesication process and concentrations of the agent in different skin regions. About 90% of the radioactivity was not recovered due to evaporation of the agent from the skin. No attempts were made to avoid evaporation, since occlusion was not considered to be a realistic exposure condition. Absorption mainly occurred within the first hour after application, with the majority of the absorbed radioactive dose either in the skin or venous blood stream of the IPPSF. A large fraction of the measured radioactivity was probably not intact sulfur mustard however, the identity of the radioactive species was not established. A multicompartmental toxicokinetic model was developed to predict penetration into and distribution within the IPPSF. The authors report that sulfur mustard decreased the vascular volume of distribution in IPPSF in a dose dependent way, a phenomenon that should be incorporated into the toxicokinetic model. 

Methods for the depolymerization of dextran to uniform fractions of lower molecular weight have led to the use of two dextran fractions that are suitable for parenteral administration.13,30 In the United States, a dextran fraction of MW 70,000 is used as a blood-volume expander. Clinical dextran is used to restore blood volume in the treatment of patients who have either lost considerable amounts of blood or are in shock. A dextran fraction of MW 40,000 is used to improve the flow in capillaries, to prevent or treat vascular occlusion, and to perfuse organs artifically. B-512(F) dextran is completely metabolized141 in man when fractions are administered parentally. Various dextran fractions have been used to prepare numerous derivatives,29 such as the sulfates, and 0-(2-diethylaminoethyl) (DEAE)-dextran, and complexes with various metals. Dextran sulfates have anticoagulant,340 antilipemic,340 and anti-ulcer341 activity. A soluble, iron-dextran complex342 of MW 5000 is used to alleviate iron-deficiency anemia, and a calcium complex332 alleviates hypocalcemia of cattle. 

Smaller vessels may be obstructed with cholesterol emboli, vascular lesions, or platelet plugs, all of which will present as isolated decreased perfusion of the glomeruli. The serum creatinine frequently is increased since the lesions are usually diffuse. However, the urinalysis most commonly will be normal since the kidney itself is not ischemic and the glomeruli are not involved. The urinary indices suggest prerenal azotemia (i.e., a low urine sodium concentration and a low fractional excretion of sodium) in the absence of systemic hypotension or a decrease in effective blood volume. The urine volume may or may not be diminished. However, the onset of oliguria sec-... 

After 20-30 min for equilibration, perfusate samples are collected to coincide with the start of urine collections at 5 to 15 min intervals. The urine volume depends on both perfusion pressure and oncotic pressure [102]. Perfusion pressure and flow are monitored continuously. Renal function is assessed from renal vascular resistance, urine flow, the ratio of l C-inulin in urine to plasma (U/Pinulin), glomerular filtration rate (GFR as inulin clearance UV/P) and the fractional excretion of sodium (FEjvja) potassium (FEj ). Inulin measurement can also be performed chemically. In some situations GFR is misleading as an index of "good function" in this model. For example, in the absence of an oncotic agent, a "reasonable" GFR is over 1 ml/ g/ min, however U/Pinulin is rarely more than 2, FENa is over 0.1 and histological examination shows extensive proximal necrosis within 20-40 min of initiating perfusion. It appears that in this situation the massive... 

In solids that contain vascular systems. D, parallel to the vascular bundle may be twice as large as it is at right angles to the bundle. Furtheimore. in such solids, D, as determined from betch leaching tests increases as the panicle size increases (below a threshold size of 3-5 mm). In dense cellular materials, on the other hand, raptured surface oells make up a progressively smaller fraction of the particle volume as size increases D, consequently decreases slightly as particle size increases. 

It provides detailed information on cardiac structure (atrial and ventricular cavity dimensions, areas, volumes, wall thickness, and mass), cardiac function (systolic and diastolic, right and left ventricular wall motion, fractional shortening and ejection fraction, global and regional, and preload and afterload), valvular disease (structure, function, and degree of regurgitation or stenosis), vascular structures, and hemodynamic data. 

Human Studies of the Consequences of AVF Creation Shortly after access creation, CO increases due to both left ventricular ejection fraction and heart rate increase [9]. These changes are probably driven by the decrease in systemic vascular resistance (caused by the arterial anastomosis of the VA) and by the increase of preload (venous return to the heart). Such changes could be considered rather physiological. However, within some weeks after access creation, Iwashima et al. [10] observed also an increase in the left ventricular diastolic diameter the indices of diastolic left ventricle function worsened, and levels of natriuretic peptides increased. The rise of B-natriuretic peptide (BNP) correlated with the diastolic function (E/A ratio, which is early/atrial left ventricular filling). Similar findings were observed in our center in a group that had their first VA with the access flow volume of only 789 361 ml/min 6 weeks after... 

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