Anticoagulation Initiation and Reversal for Cardiac Surgery

Case Synopsis

An 81-year-old woman with dyspnea at rest due to aortic stenosis (valve area 0.4 cm ² , mean gradient 50 mm Hg) presents for aortic valve replacement. Past medical history is significant for a recent pulmonary embolism, for which she received intravenous heparin therapy. At the time of operation, antithrombin III (AT-III) levels are low and the activated partial thromboplastin time is elevated. After heparinization (375 U/kg), the activated clotting time (ACT) increases to 325 seconds. An additional 125 U/kg heparin and 2000 units of AT-III concentrate are given. Thereafter the ACT increases to 866 seconds, and cardiopulmonary bypass (CPB) is commenced without further complications.