Acute normovolemic hemodilution does not reduce antithrombin concentration for cardiac surgery.
BACKGROUND
Acute normovolemic hemodilution (ANH) is used to reduce allogeneic blood transfusion with cardiac surgery. This procedure involves pre-operatively removing and storing a volume of whole blood and replacing the volume with crystalloid. The stored blood is then available for transfusion, if required. Hemodilution associated with ANH may reduce the effectiveness of heparin anticoagulation due to dilution of antithrombin. The aim of this study was to determine if antithrombin concentrations are reduced in patients who undergo one unit of ANH during cardiac surgery.


METHODS
Patients scheduled for cardiac surgery (n = 71) were grouped according to whether they did or did not undergo ANH pre-operatively. Antithrombin concentrations were measured before and after ANH. This study had 80% power to detect a difference in reduction of antithrombin concentration of 6% between groups following ANH with an alpha error of <0.05. The effect of one unit ANH was expected to cause a difference of 12% or greater.


RESULTS
No significant difference in the concentration of antithrombin between ANH patients and those that did not have ANH, nor was there a difference in the decrease in antithrombin between groups.


CONCLUSIONS
The results indicate that one unit of ANH does not significantly reduce the concentration of antithrombin prior to cardiac surgery. Thus patients who undergo one unit of ANH are not at increased risk due to dilution of antithrombin.
Linden
Matthew Dean
MD
Department of Pathology, University of Western Australia, Nedlands, Western Australia, Australia. matthew.linden@umassmed.edu
Schneider
Mark
M
Erber
Wendy Naomi
WN
D000368:Aged; D000990:Antithrombin III / Q000032:analysis*; D006348:Cardiac Surgical Procedures / Q000379:methods*; D002315:Cardiopulmonary Bypass; D000077324:Crystalloid Solutions; D005260:Female; D006438:Hemodilution / Q000009:adverse effects*; D006801:Humans; D007552:Isotonic Solutions; D008297:Male; D008875:Middle Aged; D010952:Plasma Substitutes / Q000627:therapeutic use; D011300:Preoperative Care
D000077324:Crystalloid Solutions; D007552:Isotonic Solutions; D010952:Plasma Substitutes; D000990:Antithrombin III