The lung in hemorrhagic shock. IV. The role of neutrophilic polymorphonuclear leukocytes.

The time sequence of changes in total and differential white blood cell counts in dogs subjected to hemorrhagic shock are described and are correlated with alterations in the ultrastructure of intravascular neutrophilic polymorphonuclear leukocytes in the lungs of the same dogs. Total circulating white blood cells fall to 20% of control values and neutrophils fall to 10% of control values in hemorrhagic shock; these values do not return to control levels after reinfusion of shed blood. Intravascular neutrophils in the lung are increased in number after hemorrhagic shock and exhibit alterations in ultrastructure which include loss of density in the cell sap, loss of density in granules and unusual apposition between the plasma membranes of netrophils and adjacent endothelial cells. The results are interpreted as suggesting that circulating neutrophils become "sticky" in hemorrhagic shock; that the lung exerts a sieving effect on these cells; that obstruction of alveolar capillaries by these cells may account for certain abnormalities in the alveolar microcirculation in shock; and that these results may explain the observation that the isolated lung is protected from the deleterious effects of hemorrhagic shock.