Site of pulmonary edema after unilateral microembolization

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Abstract
The effect of unilateral pulmonary microembolization on regional lung extravascular fluid accumulation was determined in dogs. Embolization was produced by injecting 100 .mu.m-diameter glass beads (0.25 g/kg) into the right pulmonary artery. After embolization of 1 lung, pulmonary arterial pressure .**GRAPHIC**. and pulmonary vascular resistance increased (P < 0.05) from base-line values of 11.7 .+-. 1.3 to 17.9 .+-. 1.3 Torr and of 3.4 .+-. 0.05 to 5.5 .+-. 0.5 Torr/(l/min). Blood flow to embolized lung measured with labeled microspheres decreased from 104.2 .+-. 24.9 to 35.2 .+-. 9.2 ml/min .cntdot. g bloodless lung after embolization, whereas flow to the normal lung increased from 43.1 .+-. 5.6 to 71.2 .+-. 19.2 ml/min .cntdot. g bloodless lung. Extravascular lung water-to-bloodless dry lung weight ratio (W/D) of 4.97 .+-. 0.32 was greater (P < 0.001) in embolized lung than the value of 3.34 .+-. 0.15 in nonembolized lung. In 6 dogs pretreated with 500 U/kg of heparin, a similar degree of duration of embolization and similar hemodynamic changes did not result in significant differences in W/D (3.88 .+-. 0.18 in right lung vs. 3.02 .+-. 0.53 in the left lung), and the right lung ratio was less (P < 0.05) than the value in the heparinized dogs, suggesting that humoral mechanisms contribute to the genesis of pulmonary edema after regional embolization. Unilateral embolization leads to a greater increase in extravascular content in the embolized lung than in the nonembolized lung. Because .**GRAPHIC**. was in the normal range after embolization, regional pulmonary edema may be due partly to the local release of factors that increase lung vascular permeability.