Blood loss in patients on cardiopulmonary bypass is tremendously large after surgery due to platelet dysfunction. Desmopressin acetate (a synthetic analogue of vasopressin) has been shown to improve blood coagulation in a variety of platelet disorders especially in patients with hemophilia, von Willebrand's disease and uremia. Recent years, it has been used to treat patients with severe platelet dysfunction and profuse hemorrhage after cardiopulmonary bypass. We have investigated the effect of desmopressin acetate administration in randomized trials of 48 adult patients placed on cardiopulmonary bypass during cardiac surgery. Twenty four patients received intravenous infusion 0.3 microgram/kg desmopressin acetate one hour after cardiopulmonary bypass and other patients only received a placebo. Comparing with the control group, patients receiving desmopressin had shortened bleeding time (3.4 +/- 0.6 vs 5.1 +/- 1.6 mins, 8 hrs post bypass), lessened blood loss (482 +/- 258 ml vs 1430 +/- 733 ml, 24 hrs post bypass) and received fewer blood component therapy (pack RBC 2.7 +/- 2.2 vs 6.6 +/- 3.2 units, FFP 4.3 +/- 2.4 vs 11.7 +/- 5.7 units, platelet 3.8 +/- 5.0 vs 8.4 +/- 7.2 units). We conclude that desmopressin acetate can improve blood coagulation ability with safety and in reducing blood loss in patients after cardiopulmonary bypass.