Dynamic Relationship between Transvascular Fluid Shift and Cardiac Output.

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To investigate transvascular fluid shift under various pathophysiological states, a device for continuous measurement of circulating blood volume was developed. To use the dilution principle for measuring blood volume, Cr 51 tagged red blood cells were employed as a tracer and an extracorporeal shunt was made of the femoral artery and vein. Gamma ray counter was placed within the extracorporeal shunt. Counting time for the radioactivity was set at every 30 second and the data was transferred to microcomputer system. The accuracy of the blood volume determination was more than 98% with this system and it was sufficient to detect the movement of fluid shift through the vascular wall.Experiments with three different protocols were performed: 1) Carbon dioxide stress, 2) Total spinal block. 3) Nicardipine induced hypotension. To determine the transvascular filtration coefficient, the vascular compliance and the compliance of interstitial fluid space in whole body, lactate Ringer's solution was infused intravenously for 10 minutes at a rate of 1 ml/kg/min in the control phase and in those of stress phases.Circulatory parameters such as cardiac output, arterial pressure or venous pressure were almost same as reported by another investigators. However, significant changes in the relationship between blood volume and venous pressure were obtained. Calculated values of transvascular filtration coefficients and compliance of interstitial fluid space were almost same in each experiment. Compliance of vascularture were increased in Nicardipine group and decreased in carbon dioxide and total spinal block groups. Delayed compliance of vascularture were decreased in all stress stages. Hence, we conclude that the delayed compliance is regulated by autonomic nervous systems.