Effect on blood volume of maintaining a high central venous pressure after major aortic valve surgery

Fluck, D. C., Lopez Bescos, L., and Gilkes, R. (1973).Thorax,28, 762-767. Effect on blood volume of maintaining a high central venous pressure after major aortic valve surgery. Serial blood volume measurements were made in 15 patients undergoing major aortic valve surgery requiring cardiopulmonary bypass. In all patients the plasma volume was measured by iodine-125 (125I) labelled albumin and in 10 the red cell mass was measured by chromium-51 (51Cr) labelled red cells. Close correlation was found between the blood volume derived from the plasma volume and central venous haematocrits and the blood volume derived by addition of the plasma volume and red cell mass. Postoperatively blood was given to maintain the right atrial pressure at between 10 and 15 cm H2O. Before operation the red cell mass, and plasma and blood volumes related to body weight were within the normal range. In the postoperative phase the first measurement two hours after the end of the operation showed a significant decrease in mean blood volume, red cell mass, and plasma volume as compared with the preoperative level. By the second postoperative measurement six hours after the end of operation the mean blood volume had risen to the preoperative level. Subsequently, over postoperative days 1 to 6 the mean blood volume remained steady, although the red cell mass tended to fall. After blood transfusion had ceased the red cell mass usually showed a progressive fall. It was considered that although there was little relationship between the right atrial pressure and the blood volume there was little or no clinical value in performing serial postoperative measurements of blood volume in addition to venous pressure monitoring in these patients.