Determinations of blood flow and shunting of 9- and 15-micrometer spheres in regional beds

Abstract

In 17 pentobarbitalized dogs, the shunting of 15-micrometer and 9-micrometer microspheres was studied in the brain, myocardium, kidney, intestine, and lung. The veins of these organs were catheterized for constant blood withdrawal for 2 min by direct venipuncture. The ratio of microsphere radioactivity in the venous blood to that in the arterial blood gave the shunting of microspheres by the venous sampling technique. The 15-micrometer microspheres showed 2% or less shunting for all organs studied, whereas the 9-micrometer microspheres had shunting ranging from 3% in the coronary sinus to 24% in the portal vein. The shunting of 9-micrometer microspheres was also calculated from direct tissue counting, where the 15-micrometer spheres were considered to be completely entrapped. The results of direct tissue counting indicate that the 2-min venous sampling underestimates microsphere shunting. CO2 administration increased significantly the shunting of 9-micrometer spheres, whereas the shunting of 15-micrometer spheres determined by venous sampling remained less than 2%. Consideration of shunting indicates that the 15-micrometer microspheres might be more appropriate for regional organ blood flow measurements, including the myocardium.

Effects of Dopamine, Dobutamine, Amrinone and Milrinone on Regional Blood Flow in Isoflurane Anesthetized Dogs

“…AM and ML might improve pulmonary circulation in the dogs with facilitating pulmonary blood circulation. As described above CM technique detected only arterial blood flow, blood flow in liver was evaluated by only through hepatic artery [9]. In this study arterial blood flow in liver tended to decrease with dopamine.…”

Salt-induced hypertension in Dahl salt-sensitive rats. Hemodynamics and renal responses.

“…Cardiac output and blood flow distribution were determined by a microsphere method, which had been validated in our laboratory by comparison with electromagnetic flow meter and xenon-133 washout technique. 21 - 24 Latex microspheres (15.0±1.0 /un in diameter, New England Nuclear Corp., Boston, Massachusetts) labeled with scandium-46 and suspended in 10% dextran solution (mol wt 78,000) were used. A known amount of microsphere suspension (about 50,000 spheres/kg body wt) was injected into the left ventricle within 10-15 seconds, and the catheter was immediately flushed with 0.7 ml 0.9% NaCl.…”

The relationship between myocardial blood flow and contraction by myocardial layer in the canine left ventricle during ischemia.

“…This problem can be minimized by taking tissue samples of adequate size such as was done in the present study. In addition, it has been suggested that there is a 1-3% non-entrapment rate in the myocardium with the use of nine micron microspheres (Buckberg et al, 1971, Fan et al 1979. With 15-/im microspheres, fewer microspheres are injected, although nonentrapment should no longer be a problem.…”