Patients who are seropositive for heparin antibodies are at increased risk of both thrombosis and bleeding (asso- ciated with heparin alternatives). Given the potentially catastrophic thrombotic complication associated with rapid-onset HIT in patients with a recent history of HIT, a very high level of vigilance is recommended in patients reexposed to heparin. These patients warrant careful surveillance, thromboprophylaxis, and possibly other special treatments to manage the increased risk. Reversal of Anticoagulation During Cardiac Operations Class IIa Recommendation  Protamine dosing for heparin reversal: It can be bene cial to calculate the protamine reversal dose based on a titration to existing heparin in the blood as this technique has been associated with reduced bleeding and blood transfusion. (Level of Evidence B) Heparin is by far the most commonly used anticoagu- lant during the conduct of cardiac operations, whether done with or without CPB. The preeminent bene t of heparin as compared with other anticoagulants is the ability to reverse its effect with protamine in a safe and expeditious manner. The goals of successful anticoagulation during CPB include limiting clotting and safely reversing the anticoagulation effect during and at the conclusion of operation, respectively. For the vast majority of opera- tions performed using CPB, heparin is the anticoagulant used and protamine is the reversal agent. An important part of the operation is to adequately remove all of the heparin effect at the end of operation. There are at least three methods commonly used to detect residual heparin effect after protamine reversal: (1) ACT measurement; (2) point-of-care testing using protamine titration of hepa- rinized blood samples; and (3) thromboelastography with or without heparinase. Comparisons of these three methods suggest that ACT-based measurements of re- sidual heparin effect are the least accurate means of detecting residual heparin effect [84, 85]. 