The correlation of sequential changes in the distribution of pulmonary blood flow in hemorrhagic shock with the histopathologic anatomy.

Histopathologic changes were described and correlated with hemodynamic changes in a series of farm-reared dogs by a preparation and a protocol which were shown to simulate closely physiologic events in clinical hemorrhagic shock; neither anesthesia nor thoracotomy was used and flush solutions for catheters were strictly limited; a series of sham-treated controls was used for comparison. Five different isotopes were used to label microspheres to measure blood flow sequentially at the tissue level at various stages of the shock protocol. At death, multiple tissue sections were taken relative to six parallel segments of the lung arranged according to dependency so that correlations of structure and function might be related to the influence of gravity. The degrees of severity of atelectasis, hemorrhage, edema, congestion, inflammation, and hyperaeration were evaluated by rating scales. Tissues from the most dependent areas had a higher incidence and greater severity of histologic lesions. Tissues with mild histologic rating tended to have lower percentages of flow after hemorrhage, but normal or increased flow after reinfusion. The severely damaged tissue received greater than average flow throughout. Tissues with severe atelectasis paralleled the course of those with a high over-all severe pathologic rating. Tissues with severe inflammation had less blood flow in the control period, increased flow in Stages B1 and B2 and a subsequent return to control values. Those with severe edema had reduced flow in Stages B2 and B3, but high flows after reinfusion.