In a comparative analysis study of 10 patients undergoing cardiopulmonary bypass, three different methods of the ACT test were compared with ECT [66]. Although not as accurate as the ECT, the more commonly available celite-ACT was found to have an acceptable correlation with ECT-determined bivalirudin 0.93). Bivalirudin has the broadest experience in patients undergoing cardiac surgery (with and without CPB) and in patients with HIT and patients with HIT with throm- bosis requiring CPB [67]. This includes procedures requiring deep hypothermic circulatory arrest [68]. Controlled trials suggest that bivalirudin provides adequate anticoagulation in all patients [69, 70]. In these trials, secondary endpoints including mortality, 24-hour blood loss, overall incidence of transfusions, and dura- tion of surgery were similar for bivalirudin-treated pa- tients and for patients having CPB with heparin anticoagulation and protamine reversal. Several studies for example, the Evaluation of Patients During Coronary Artery Bypass Graft Operation: Linking Utilization of Bivalirudin to Improved Outcomes and New Anticoagu- lant Strategies (EVOLUTION-ON) and the Coronary Artery Bypass Grafting Heparin-Induced Thrombocyto- penia Thrombosis Syndrome On- and Off-Pump Safety and Ef cacy (CHOOSE-ON) trials propose a reliable therapeutic protocol for bivalirudin [69, 70]. Bivalirudin dosing in the CHOOSE-ON and EVOLUTION-ON trials included a loading dose of 1.0 mg/kg, infusion of 2.5 mg $ , and pump prime of 50 mg. The adequacy of anticoagulation was monitored using 2.5 times the base- line ACT. In many centers, target ACT levels were ach- ieved with lower loading dose and infusion rates. In the EVOLUTION-ON multicenter, open label trial, 101 patients were randomly assigned to either bivalirudin or heparin with protamine reversal. Both groups were successfully anticoagulated, and there were no signi cant differences in morbidity or mortality between groups at 7 days, 30 days, or 12 weeks. 