VALIDATION OF FLUORESCENT-LABELED MICROSPHERES FOR MEASUREMENT OF REGIONAL ORGAN PERFUSION

Estimations of dog lung, pig heart, and pig kidney regional perfusion by use of fluorescent-labeled microspheres were compared with measurem ents obtained with standard radiolabeled microspheres. Pairs of radio- and fluorescent-labeled microspheres (15 mum diam, 6 colors) were inj ected into a central vein of a supine anesthetized dog and the left ve ntricle of three supine anesthetized pigs while reference blood sample s were simultaneously withdrawn from a femoral artery in the pigs. The lungs were cubed into approximately 2 cm3 pieces (n = 1,510). Each pi g heart and kidney was cubed into approximately 1-g pieces (total n = 192 and 120, respectively). The radioactivity of each organ piece and reference blood sample was determined using a scintillation counter wi th count rates corrected for decay, background, and spillover. Tissue samples and reference blood samples were digested with KOH and filtere d and the fluorescent dye was extracted with a solvent, or the dye was extracted from lung tissue without filtering. The fluorescence of eac h sample was determined for each color by use of an automated spectrop hotometer. Perfusion was calculated for each organ piece from both the radioactivity and fluorescence. Correlation between flow determined b y radio- and fluorescent-labeled microspheres was as follows: r = 0.98 +/- 0.01 (SD) (lung, filtered, n = 588), r = 0.99 +/- 0.00 (lung, non filtered, n = 710), r = 0.95 +/- 0.02 (heart, filtered), and r = 0.96 +/- 0.02 (kidney, filtered). Compared with colored microspheres, metho ds for quantitating fluorescent-labeled microspheres are more sensitiv e, less labor intensive, and less expensive. Fluorescent-labeled micro spheres provide a new nonradioactive method for single and repeated me asurement of regional organ perfusion.