Macromolecules are present in lung preservation solutions to limit liquid filtration out of the pulmonary circulation and minimize
pulmonary edema. We tested the effectiveness of these molecules by measuring interstitial
edema in rat lungs perfused with macromolecular solutions (University of Wisconsin [
UW] solution and
Euro-Collins solution supplemented with modified
pentastarch [
pentafraction, PEN]) or with solutions that lacked macromolecules (
UW solution with PEN and
Euro-Collins solution.) The lungs were inflated with air and perfused with one of the test solutions, then rapidly frozen and prepared for histological analysis. From tissue sections, we measured cross-sectional areas of pulmonary arteries and veins, and also measured cross-sectional areas of the interstitial spaces surrounding arteries and veins. We then calculated the interstitium-to-vessel cross-sectional area ratio. In lungs perfused with macromolecular solutions these ratios were 0.09+/-0.15 and 0.53+/-0.56 (mean +/- SD) for
UW solution and Euro-Collins solutions
solution with PEN, respectively (P</=0.05). In lungs perfused with solutions that lacked macromolecules, area ratios were 0.48+/-0.88 and 1.95+/-1.82 for
UW solution without PEN and
Euro-Collins solution, respectively (P</=0.05). Solutions containing PEN caused less interstitial expansion than their counterparts that lacked it, but
UW solution without PEN caused interstitial expansion equal to that of
Euro-Collins solution with PEN. We conclude that macromolecules limit
edema formation, but other constituents of
UW solution limit
edema formation also.