[Disorders of the oxygenating function of the lungs during open-heart surgery]

A retrospective analysis of arterial blood oxygenation during open-heart surgery in 463 patients revealed pulmonary oxygenation disorders in 23% prior to perfusion and in 49% in the post-perfusion period. The basic mechanism underlying the fall in arterial blood oxygenation is the increasing venous admixture in the lungs. A growth in the venous admixture in the post-perfusion period is brought about by a decreased total ventilation/perfusion ratio, increased alveolar shunting, and impaired diffusion. It was found, that the assisted ventilation regimen at +5+8 cm H2O in the post-perfusion period caused a 30% reduction in the venous admixture and improved the blood oxygenation. Additional use of diuretics to diminish the intrapulmonary water causes a 59% reduction in the venous admixture. A prophylactic pre-perfusion administration of corticosteroids, vitamin E, and protease inhibitors maintains the oxygenating function of the lungs, which is manifested in a higher blood oxygenation in these patients after assisted circulation compared to the controls.