Effect of acute hemorrhagic shock on pulmonary microvascular fluid filtration and protein permeability in sheep.

In an attempt to further delineate the pathophysiology of the shock-lung syndrome, we studied the effect of hemorrhagic shock on the pulmonary microcirculation in the adult sheep with lung lymph flow and lymph protein transport as indices of fluid filtration and vascular permeability to protein. We noted that lymph flow remained at baseline levels during shock, despite significant decreases in pulmonary artery and left atrial pressures. This suggests that microvascular pressure is maintained by an increase in pulmonary venous resistance. We demonstrated that lymph protein transport does not increase during shock, which indicates that a change in pulmonary vascular permeability to protein does not occur.