Materials and Methods

Twenty-seven mongrel dogs weighing betwccn 20 to 30 Kg. were anesthetized with intravenous sodium pentobarbital. Respira-tion was controlled with a mechanical res-pirator, using room air with intermittent positive pressure. Either right or left tho-racotomy or median stermotomy incisions were utilized for cxposure. For closed car-diac proccdures, no extracorporeai circu-latory assistance was used. For procedures which rcquired opening the aorta or a chamber of the heart, an extracorporeal pump system with a disposable bubble oxygenator was used. Both venae cavae and one femoral artrey were cannulated for outflow and inflow conduits. Dyes used for injections were methylene blue and