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The heterogeneity of regional pulmonary blood flow (RPBF) can be assessed by fractal analysis. The fractal dimension (FD) is a scale-independent measure of spatial heterogeneity of blood flow. The relative dispersion (RD) is often used to obtain the heterogeneity of RPBF but it is influenced by the resolution of measurement. The Blood Flow Analysis (BFA) System was developed in Delphi to represent the three-dimensional structure of lung blood flow and calculates statistics of FD, RD, spatial correlation of neighbored tissue samples and shows histograms of blood flows at diverse time points during different experiments. The BFA System reads a text file with flows, measured with fluorescent microsphere technique, and constructs the lung anatomy with volumetric pixels showing the flows with a color schema. It is possible to rotate the lungs into two axis (XY) and the statistics are shown with 3D graphics. The System maintains a database with data from various studies at same time. The BFA System was validated with four data sets from previous experiments. The BFA System has shown consistency and it is a new tool to help researchers during lung perfusion studies.

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Small-volume resuscitation by means of bolus infusion of hypertonic saline solutions was first applied for the primary treatment of severe hemorrhagic and traumatic shock and promptly restored central hemodynamics and regional organ blood flow. Mechanisms of action are diverse--i. maintenance of high cardiac output (direct myocardial stimulation; increase in intravascular volume); ii. maintenance of peripheral arterial vasodilation (effect of hyperosmolality; plasma volume effect) and iii. reduction of tissue edema (shifting of tissue water along the osmotic gradient). These mechanisms promote the restoration of the severely impaired microcirculation frequently seen also in sepsis. Hypertonic volume therapy has been the object of several experimental studies of acute hyperdynamic endotoxemia, however, a greater number of clinical studies have to be developed for the better understanding of the positive, and perhaps hazardous, effects of small-volume resuscitation in sepsis and multiple organ failure. The aim of this paper is to review the concepts involving such solutions, and their potential use in treatment of profound hypovolemia and microcirculatory deterioration associated with sepsis and endotoxic shock.

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Regional left ventricular myocardial blood flow was studied in an experimental model of pulmonary edema and microembolization (PEM) ventilated with positive end-expiratory pressure (PEEP). The analysis was based on a 3-dimensional extension of the autocorrelation function used to assess the spatial correlation (rspat) of myocardial perfusion. Experiments were performed on 8 premedicated, anesthetized and mechanically ventilated dogs. PEM was induced with oleic acid (0.01 mg/kg) and glass beads. Successive PEEP values of 10, 15 and 20 cm H2O (P20) were applied and norepinephrine (NE, 0.2-1.0 microgram min-1 kg-1) was administered after P20. Regional perfusion was measured with radioactive microspheres. The left ventricle (LV) was dissected into 256 samples. rspat was computed as the correlation of regional perfusions of samples p units apart in the apex-to-base, endo-epicardial and angular directions. Analysis was performed after anesthesia and instrumentation (control, C), P20 and NE. Control values of rspat were around 50% in the apex-to-base and angular directions and the sign was inverted in the endo-epicardial direction. A reduction of rspat to values close to zero was observed in all directions for P20 and NE. This is the typical pattern of independent distribution. Thus, the results indicate that, under the experimental conditions used, there is some degree of neighborhood dependence of regional LV myocardial blood flow. This dependence is not observed under PEM, mechanical ventilation with PEEP and NE.

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RESUMEN

Regional left ventricular myocardial blood flow was studied in an experimental model of pulmonary edema and microembolization (PEM) ventilated with positive end-expiratory pressure (PEEP). The analysis was based on a 3-dimensional extension of the autocorrelation function used to assess the spatial correlation (rspat) of myocardial perfusion. Experiments were performed on 8 premedicated, anesthetized and mechanically ventilated dogs. PEM was induced with oleic acid (0.01 mg/kg) and glass beads. Successive PEEP values of 10, 15 and 20 cm H2O (P20) were applied and norepinephrine (NE, 0.2-1.0 microgram min-1 kg-1) was administered after P20. Regional perfusion was measured with radioactive microspheres. The left ventricle (LV) was dissected into 256 samples. rspat was computed as the correlation of regional perfusions of samples p units apart in the apex-to-base, endo-epicardial and angular directions. Analysis was performed after anesthesia and instrumentation (control, C), P20 and NE. Control values of rspat were around 50 per cent in the apex-to-base and angular directions and the sign was inverted in the endo-epicardial direction. A reduction of rspat to values close to zero was observed in all directions for P20 and NE. This is the typical pattern of independent distribution. Thus, the results indicate that, under the experimental conditions used, there is some degree of neighborhood dependence of regional LV myocardial blood flow. This dependence is not observed under PEM, mechanical ventilation with PEEP and NE

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