Effect of furosemide in canine low-pressure pulmonary edema.

We studied the effect of furosemide on pulmonary oxygen exchange, lung liquid, and central hemodynamics in dogs with pulmonary capillary leak induced by intravenous oleic acid (OA). 2 h after OA, triple indicator-dilution lung liquid volume and pulmonary shunt (Qs/Qt) doubled despite normal pulmonary capillary wedge pressure in 16 dogs compared with dogs not given OA in which no variable change during the same time. Six edematous dogs were then treated with furosemide (1 mg/kg), and 2 h later they showed significant reductions in Qs/Qt and lung liquid. In contrast, six other edematous dogs not given furosemide increased Qs/Qt and lung liquid during the same time. The changes in edema after furosemide could not be attributed to altered wedge or colloid osmotic pressures, and similar changes in Qs/Qt and lung liquid with furosemide were observed in four nephrectomized dogs. We conclude that pulmonary vasoactive effects of furosemide account for reduced shunt and edema in canine pulmonary capillary leak. These effects of furosemide differ from those in cardiogenic pulmonary edema, and suggest a different rationale for diuretic therapy in low-pressure pulmonary edema. Analysis of count rates from 51Cr-labeled erythrocytes and 125I-labeled albumin in lungs excised from 12 dogs indicated that the composition of excess lung liquid did not change with furosemide, and was 50% plasma, 25% blood, and 25% crystalloid.