['Weight-based heparin and protamine dosing strategies for cardiopulmonary bypass (CPB) do not take into account interpatient variability in drug sensitivity and may result in bleeding complications. We compared the Hemochron RxDx heparin and protamine titration system with standard weight based management with regard to heparin dose, protamine dose, and perioperative bleeding.', 'One hundred and thirty-five cardiac surgical patients were randomised into four groups. Group 1 received standard heparin and protamine management: Group 2 received heparin and protamine by in vitro titration. Group 3 had the heparin dose titrated, and group 4 had the protamine dose titrated. Coagulation tests, bleeding, and transfusion requirements were measured.', 'The initial heparin bolus predicted by the titration was < 300 U.kg-1 in all patients. Group 2 received a lower heparin bolus for the initiation of bypass but total heparin doses were not different among groups (group 1 = 365 +/- 43, group 2 = 348 +/- 73 U.kg-1, group 3 = 394 +/- 86 U.kg-1, group 4 = 376 +/- 60; P = 0.06). Groups 2 and 4 received a lower initial and a lower total protamine dose (total dose group 1 = 4.03 +/- 0.65 mg.kg-1, group 2 = 3.56 +/- 1.11 mg.kg-1, group 3 = 4.22 +/- 0.90 mg.kg-1, group 4 = 3.38 +/- 0.98 mg.kg-1, P = 0.001). The incidences of incomplete heparin neutralisation (P = 0.14) and heparin rebound (P = 0.1) were not different among groups. Postoperative bleeding and transfusion requirements did not differ.'] Do heparin and protamine titration improve haemostasis in cardiac surgical patients?