Relationship between hemodynamics and blood volume changes after cardiopulmonary bypass during coronary artery bypass grafting.

The blood volume and central hemodynamics were assessed in 22 patients undergoing coronary artery bypass grafting before and after cardiopulmonary bypass. Patients were divided into two groups according to their blood volume after cardiopulmonary bypass. In group A (n = 10) the patients were hypovolemic and in group B (n = 12) the patients were hypervolemic after cardiopulmonary bypass. At the same time the mean plasma volume did not change significantly in group A and increased in group B. Hypovolemia in group A was accompanied by a significantly lower cardiac index and oxygen delivery index than in group B. There was a correlation between the changes in cardiac index and changes in total blood volume (r = 0.57; P < 0.01). Patients in neither group suffered from hypoxia. We conclude that extreme hemodilution after cardiopulmonary bypass must be normovolemic, and the pulmonary capillary wedge pressure or right atrial pressure as a guide for blood volume evaluation after termination of cardiopulmonary bypass may be misleading.