Superior Vena Cava Obstruction

The effects of superior vena cava obstruction vary according to the degree and location of the obstruction and the suddenness of its development. To determine the tolerance of animals to this condition, to measure the effect on venous pressure and to trace the paths of collateral circulation, experimental obstruction of the superior vena cava was produced in dogs. The vein was exposed through an intercostal incision and completely occluded by dividing between ligatures. The usual aseptic technique was followed and the operations were performed under intratracheal ether anesthesia administered with positive pressure. Obstructions were of 2 types, (1) above the junction of the azygos vein, and (2) including the azygos vein. Two attempts were also made to obstruct the superior vena cava below the junction of the azygos vein but both dogs died within a few minutes. Obstruction above the level of the azygos vein was produced in 7 dogs. One died within 24 hours and 3 died within 12 to 14 days as a result of a propagating thrombus or an empyema. Three recovered. Of the latter, one was sacrificed for study after 30 days. Another was later subjected to azygos vein obstruction and the third is alive after more than 5 months. One dog survived the immediate effects of a 2-stage obstruction of the superior vena cava and azygos vein but died at the end of 21 days from an infected bilateral pleural effusion. The most striking general results of superior vena cava obstruction were cyanosis of the tongue and oral mucosa and injection of the conjunctivae. Somnolence, listlessness and slow deep respirations were also noted. The dogs with obstruction just above the right atrium, dying within a few minutes, had extreme cyanosis of the upper part of the body.