The influence of heparin on haemodynamics and blood gases during abdominal aortic surgery.

Central haemodynamics and blood gases were measured in 26 patients undergoing elective aortic surgery for atherosclerotic or aneurysmal disease. Recordings were made at seven defined time points, starting before anaesthesia and ending 30 min after declamping of the aorta. The patients were randomly divided into two groups, one receiving heparin at an early stage and the other at a late stage of the operative procedure. A declamping shock phenomenon could be prevented by thorough blood and fluid replacement. After removal of the aortic clamp the cardiac output increased, except in a few patients who were considered preoperatively to be poor risks. A significant decrease in arterial oxygen tension and increase in pulmonary artery and pulmonary capillary wedge pressures occurred in patients receiving heparin at a later stage. The effect of heparin points to possible intravascular coagulation and pulmonary microembolism during the operation.