Surgical Procedures
The surgical technique for ATAAD used at our center has been described previously 17. Median sternotomy, cardiopulmonary bypass (CPB) with hypothermic circulatory arrest and cold blood cardioplegia was used in all cases. Heparin was reversed with protamine after weaning from CPB and transfusion of procoagulants and blood products initiated. The cooling strategy used in the elective controls were hemiarch procedure 25°C; valve sparing root replacement (ad modum David): 30°C; root replacement (ad modum Bentall) or aortic valve replacement with supracoronary replacement of the ascending aorta: 32°C; isolated replacement of the ascending aorta: 32-36°C.
During the study period, all patients received preoperative tranexamic acid (2-3g preoperatively and 1-2g after termination of CPB for a total of 4g) to prevent hyperfibrinolysis. A Dideco Electa (Sorin Group, Electa, Italy) cell saver machine was used to process and re-infuse salvaged blood. Heparin dose was calculated using the Hepcon HMS Plus system (Medtronic, Minneapolis, MN, USA) to reach an activated clotting time (ACT) of >480s and monitored serially during CPB to maintain ACT >480s with additional heparin added if necessary. Antithrombin was administered if the heparin dose response slope was low (<70s/U/ml) and a subsequent test was conducted ten minutes later. Two patients in each group received 2000IE of antithrombin during surgery. ACT was routinely controlled at the end of surgery, and additional protamine was given if ACT exceeded 120 seconds.