Present state of intentional hemodilution.

Preoperative intentional hemodilution is induced by isovolemic exchange of whole blood with colloid solutions in order to gain autologous blood while maintaining normovolemia. The basic mechanism that compensates for the fall of oxygen capacity of the diluted blood is the rise in cardiac output, and organ blood flow, factors that result from the improved fluidity of blood at lower hematocrits. Normal tissues maintain adequate oxygenation during hemodilution through the enhanced redistribution of blood. In ischemic tissues this effect is enhanced, and causes an increase in the oxygenation of ischemic tissues. Limited preoperative and intraoperative hemodilution are alternatives to donor blood transfusion in patients undergoing elective surgery. In shock patients the hemodilution achieved with red cell free primary volume substitutes is an effective treatment for shock-induced microcirculatory disorders; furthermore, intentional hemodilution is the most effectual hemorheological therapy for the treatment of ischemic disease.