Effect of heparin on pulmonary edema after microembolization in rats

Abstract

Similar degree of pulmonary microembolization was induced in nonheparinized and heparinized rats by injecting 50 um diameter glass beads into the jugular vein. At 1 hour after the embolization the extravascular lung water content/bloodless dry lung weight in the non-heparinized was increased from control value of 3.32 ± .067 to 13.06±2.32 (p<0.05); but the increase (p<0.05) in the heparinized rats of 7.53±.48 was less (p<0.05) than in the non-heparinized rats. Fibrin accumulated in the non-heparinized rats after embolization, but not in the heparinized animals. The results suggest that release or activation factors subsequent to the fibrin accumulation induced by pulmonary microembolization attenuates the development of pulmonary edema in the rat. Since heparin pretreatment in rats did not completely prevent the pulmonary edema as in dogs, factors in addition to those associated with fibrin accumulation also contribute to the fluid accumulation in the rat lungs after microembolization. The results suggest that the development of edema after pulmonary microembolization cannot be attributed only to fibrin accumulation in all species, but other factors may also be involved.