[Intrapulmonary venous admixture during open heart surgery]. / Vnutrilegochnoe venoznoe primeshivanie pri operatsiiakh na otkrytom serdtse.

Monitor-computer study of changes in the ventilatory parameters, hemodynamics, gas exchange has shown that assisted circulation in patients operated on for acquired heart valve defects causes in the postperfusion period a 2-fold increase in intrapulmonary venous admixture (Qs/Qt), which accompanied an increase in alveolar-arterial difference (pO2) and a fall in arterial blood pO2. An increase in Qs/Qt upon assisted circulation is associated with a decrease in ventilation/perfusion pulmonary ratio and possible deterioration of diffuse processes due to hemodilution-induced water balance disturbances. Controlled lung ventilation with positive end respiratory pressure (5-8 cm H2O) partially decreases intrapulmonary shunting and improves arterial blood oxygenation. Positive effect, i. e. improved oxygenating lung capacity and decreased intrapulmonary shunting is achieved with water balance normalization due to early administration of diuretics upon assisted circulation.

[Disorders of the oxygenating function of the lungs during open-heart surgery]. / Narushenie oksigeniruiushchei funktsii legkikh vo vremia operatsii na otkrytom serdtse.

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.