Direct effects of nitroprusside do not alter gas exchange in canine oleic acid edema.
The authors investigated why intrapulmonary shunt (QS/QT) increases with sodium nitroprusside (SNP) in canine oleic acid pulmonary edema. To determine the effects of flow alone on QS/QT, a peripheral arteriovenous fistula with a variable resistor was employed to increase cardiac output (Q) 26 and 52% above base line in a stepwise fashion (P less than 0.01). To examine the direct effects of SNP, distinct from changes in flow, the drug was given to produce matched increments in Q in each dog (P less than 0.01). To control for time, base-line measurements were obtained before and after each intervention, the sequence of which was alternated. At each increment in Q, SNP and the arteriovenous fistula increased QS/QT a similar amount. The mixed venous O2 tension (P-vO2) followed Q similarly in each group. Pulmonary vascular resistance (PVR) fell more (P less than 0.01) with SNP than with the arteriovenous fistula at identical Q and P-vO2. The authors conclude that, in this model, a direct pharmacological effect of SNP does not contribute to the deterioration in QS/QT. In fact, SNP exerts a pulmonary vasoactive effect that does not adversely affect gas exchange.
D000704:Analysis of Variance; D000818:Animals; D001164:Arteriovenous Fistula / Q000503:physiopathology; D004285:Dogs; D005292:Ferricyanides / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects; D009599:Nitroprusside / Q000494:pharmacology*; D019301:Oleic Acid; D009829:Oleic Acids; D011654:Pulmonary Edema / Q000139:chemically induced / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange / Q000187:drug effects*
D005292:Ferricyanides; D009829:Oleic Acids; D009599:Nitroprusside; D019301:Oleic Acid