Pulmonary Arteriovenous Admixture in Cardiac Surgical Patients

Abstract

Patients undergoing cardiac surgery with cardiopulmonary bypass for mitral insufficiency develop significant hypoxemia after surgery. This is due mostly to true shunt, but there is a significant contribution due to ventilation-perfusion abnormalities. The condition persists for eight to ten days but is reversible. Breathing 100% oxygen in the postoperative period reduced cardiac output and pulmonary artery pressure and increased arteriovenous oxygen content differences. A redistribution of pulmonary blood flow is suggested by these findings, and accordingly the value for true shunt may vary with changing inspired oxygen concentrations.