Changes in blood volume during acute normovolemic hemodilution

Question. What is the impact of acute preoperative normovolemic hemodilutio n (ANH) on blood volume, intravascular colloid, and loss of red cells in th e perioperative period? Methods. In 20 patients undergoing radical hysterectomy, preoperative ANH w as performed to a hematocrit of 22 % using 5 % albumin (albumin group;n=10) or 6% hydroxyethylstarch solution (HES group; n=10). Intraoperative retran sfusion of ANH blood was started at a hematocrit of 18%. Plasma volume (ind ocyanine green-dilution technique), hematocrit, and plasma protein concentr ation were measured before and after ANH, before retransfusion, and postope ratively. Red cell volume (labelling erythrocytes with fluorescein) was det ermined before and after ANH and postoperatively. In the HES group hydroxye thylstarch concentrations were measured in plasma and urine. Results. After removal of about 1,500 ml of blood and replacement with 15% more colloid solution,the blood volume was maintained in both groups after ANH. After a mean blood loss of about 1,800 ml, an average of 150 ml of red cells were saved due to ANH in both groups. Conclusions. Double label measurements of blood volume demonstrated that wi th the colloids used a surplus of 15% of colloid infusion in relation to bl ood removal was necessary to generate isovolemia after ANH.