Coagulation in Acute Aortic Dissection (CAAD)

Impact of Anticoagulation Management on Thrombin Generation During Surgery for Acute Aortic Dissection

Acute aortic dissection (AAD) involving the ascending aorta (Stanford classification type A) remains a life-threatening disease. Excessive perioperative bleeding requiring massive transfusion of allogeneic blood products, and surgical reexploration remain major challenges in these patients. Previous research has indicated that patients with AAD show pronounced haemostatic alterations prior to surgery which are aggravated during major aortic surgery with cardiopulmonary bypass and hypothermia full heparinization. Intensified anticoagulation management guided by heparin dose response (HDR) calculation, and repeated measurement of heparin concentration may be more effective than standard empiric weight-based heparin and protamine management monitored by activated clotting time (ACT) measurements to suppress thrombin generation during surgery for AAD. This randomized controlled clinical trial compares the impact of two recommended anticoagulation management strategies during surgery for AAD including deep hypothermia on activation of coagulation: Heparin/protamine-management based on HDR-titration by means of HMS Plus® versus current institutional standard (HDR- versus ACT-approach). Primary endpoint is thrombin generation as measured by early postoperative prothrombin fragment 1+2 (F1+2). Secondary endpoints are other markers of coagulation and fibrinolysis as well as clinical outcome.

Hypotheses: Primary: HDR-approach is superior to ACT-approach in terms of suppressing thrombin generation after emergent surgery for acute aortic dissection (Stanford type A). Secondary: HDR-approach is superior with regard to early postoperative haemostatic capacity requirement of blood product transfusion and haemostatic agents postoperative bleeding Design: Investigator-initiated, single-site, parallel-group (1:1), prospective, randomized, partially double-blinded trial in patients undergoing emergent surgery for acute aortic dissection comparing two heparin management strategies with superiority design. Prior to randomization, patients are stratified according to preoperative organ dysfunction and anticoagulation therapy. Acute research study design as patients with acute aortic dissection are considered incompetent according to the Danish Research Ethics Committees definition. Deferred consent by the competent patient or her/his proxy (next of kin) and an independent physician) is used. 26 consecutive patients undergoing emergent surgery for acute aortic dissection (Stanford type A) are randomized 1:1 into the following heparin management strategies with an ACT target of 480 seconds: Individualised HDR-approach Conventional ACT-approach No interim analysis. A sub-study to compare cost-benefit of both strategies is planned.

Investigator-initiated single-site paralle-group (1:1) prospective, randomized, partially double-blinded trial

Treatment group allocation cannot be concealed for the operating team, but participants, other members of the treatment team, laboratory personnel and other practitioners administering postoperative care as well as outcome assessors will be blinded regarding the allocation.

Heparin concentration necessary to achieve target ACT > 480 sec. calculated based on individual HDR-curve. If HDR slope ˂80 s/IU/mL (reduced sensitivity to heparin), 1000 IU of AT concentrate (Antitrombin III "Baxalta"®, Takeda Pharma, Vallensbæk Strand, DK). Whole blood concentration of circulating heparin assessed by heparin assays. Additional heparin given as required. After weaning, protamine necessary to reverse circulating heparin calculated according to heparin-protamine titration measurement. After protamine, heparin reversal evaluated with low-range heparin-protamine titration cartridge and additional protamine given as required.

Initial Heparin 400 IU/kg (500 IU/kg if treated with heparin prior to surgery). ACT Assessment with Hemochron® Signature Elite (ITC, International Technidyne Corp., Edison, NJ, USA). Additional heparin until ACT > 480 sec. If ACT < 480 sec. after despite repeated heparin supplement with 1000 IU of AT III concentrate. Target ACT > 480 sec. during normothermic CPB, and target ACT > 700 seconds during hypothermia After weaning, protamine 10mg/mL (0.7 mg of protamine/ 100 IU total heparin administered). Heparin reversal is evaluated with an activated partial thromboplastin (APTT). If APTT > 40 seconds, additional protamine (25-50 mg i.v.).

Gravimetric estimation of intraoperative blood loss (calculation based on the change between dry and blood-soaked sponges, accounting for irrigation) in mL

Inclusion Criteria: Age > 18 years Emergent Acute Aortic Dissection with cardiopulmonary bypass Incapable of providing informed consent Exclusion Criteria: History of congenital coagulation disorder (haemophilia) Previous open cardiac surgery Death during induction of anaesthesia