Anticoagulation management in a patient with an acquired antithrombin III deficiency

We report a case of heparin resistance and its management during cardiopulmonary bypass (CPB). A 63-year-old, 96 Kg female with a posterior myocardial infarction (MI) with previous deep venous thrombosis was treated with intravenous (IV) heparin infusion for 7 days before myocardial revascularization surgery. The patient required 1200 IU/Kg of beef lung heparin to extend the activated clotting time (ACT) in order to initiate CPB. A total of 1562 IU/Kg of heparin was administered throughout the procedure. This acquired heparin resistance was attributed to an antithrombin (AT III) deficiency, and was treated with fresh frozen plasma (FFP) to restore adequate anticoagulation. The patient's heparinized ACTs ranged between 368 seconds and 387 seconds before FFP administration as opposed to 626 seconds to 1329 seconds after treatment with FFP and additional heparin once on CBP. The patient experienced an uneventful postoperative course. Future treatment with AT III concentrate rather than FFP may reduce heparin requirements that will, in turn, reduce protamine reversal dose, postoperative bleeding attributable to heparin rebound, and its associated complications.