Effects of furosemide on pulmonary shunts

In 23 mechanically ventilated anuric (six) or oliguric (17) patients (less than 16 ml/h of urine output) with severe gas exchange abnormality, we investigated the effect of furosemide on intrapulmonary shunt (Qs/QT). Before and after 0.5, 1, and 2 h of IV administration of 200 mg of furosemide, we assessed the intrapulmonary shunt and PaO2 while patients' hemodynamic measurements were monitored. Ventilatory parameters remained constant throughout the study. While the urine output was minimal and no alteration in hemodynamic values was found, the Qs/QT decreased from 27.7 +/- 2.3 percent (mean +/- SEM) at control to 24.3 +/- 2.1 percent (p less than 0.01) at 0.5 h, 21.7 +/- 2.1 percent (p less than 0.001) at 1 h, and 18.1 +/- 1.8 percent (p less than 0.001) at 2 h. The PaO2 showed no significant difference at 0.5 h but rose significantly from 96 +/- 14 to 105 +/- 14 mm Hg (p less than 0.05) and 111 +/- 14 mm Hg (p less than 0.01) at 1 and 2 h, respectively. Since we observed no changes in hemodynamics, we speculate a direct effect of furosemide in the pulmonary vasculature affecting the ventilation-perfusion mismatch and, therefore, the Qs/QT and PaO2.