Platelet trapping and haemodynamics in unilateral and bilateral experimental pulmonary macroembolism.

Cat lungs were embolized with autocoagulated autologous blood clots and the platelet-trapping ability of the lung vessels and the haemodynamic responses were studied. Embolization was bilateral or strictly unilateral. It elicited on average a twofold increase in 51Cr-labelled platelets in embolized parts of the lungs. Microscopy revealed platelet aggregates in arteries with diameter 50-100 microns. A temporary decrease in systemic platelets immediately postembolus was found. In the nonembolized lung at unilateral embolization the pulmonary platelet aggregation did not occur and no haemodynamic response was detected, indicating that platelet-aggregating substances or humoral factors did not recirculate from affected to unaffected parts of the lungs.