Effect of anemia on intrapulmonary shunt during atelectasis in rabbits.
To elucidate the effects of anemia on intrapulmonary shunt, we studied a model of left lung atelectasis in anesthetized rabbits. In 10 rabbits, isovolemic anemia was produced by sequential hemodilution. Seven control rabbits were followed over time, without hemodilution. Intrapulmonary shunt (Qs/QT) was measured by using blood gas analysis and by quantitation of the percentage of blood flow to the collapsed left lung (QLl/QT) using fluorescent microspheres. In control rabbits, Qs/QT and QLl/QT decreased over time, whereas arterial PO2 increased. In hemodiluted rabbits, there was a trend toward increased Qs/QT and QLl/QT. There were significant differences in the behavior of Qs/QT, QLl/QT, and arterial PO2 between control and hemodiluted rabbits. Hemodynamic parameters, including cardiac output and pulmonary artery pressure, were not different between groups. In a third group of rabbits with pharmacologically induced acidosis but no hemodilution, Qs/QT and QLl/QT decreased over time, and arterial PO2 increased. We conclude that acute isovolemic anemia has a deleterious effect on pulmonary gas exchange, possibly through attenuation of hypoxic pulmonary vasoconstriction.
Deem
S
S
Department of Anesthesiology, Seattle Veterans Affairs Medical Center, University of Washington 98195-6540, USA.
Bishop
M J
MJ
Alberts
M K
MK
D000740:Anemia / Q000503:physiopathology*; D000818:Animals; D004195:Disease Models, Animal; D000860:Hypoxia / Q000503:physiopathology; D001261:Pulmonary Atelectasis / Q000503:physiopathology*; D011652:Pulmonary Circulation / Q000502:physiology; D011659:Pulmonary Gas Exchange; D011817:Rabbits; D013997:Time Factors