ACT Guided Heparinization During Open Abdominal Aortic Aneurysm Repair.

Aim of the ACTION-1 study is to determine whether ACT guided heparinization decreases thrombo-embolic complications (TEC) and mortality after elective open AAA surgery, without causing more bleeding complications.

Heparin is used during open abdominal aortic aneurysm (AAA) surgery to reduce thrombo-embolic complications (TEC): such as myocardial infarction, stroke, peripheral embolic events and the related mortality. On the other hand, heparin may increase blood loss, causing harm for the patient.

Heparin has an unpredictable effect in the individual patient. The effect of heparin can be measured by using the Activated Clotting Time (ACT). ACT measurement in open AAA repair could be introduced to ensure the individual patient of safe, tailor-made anticoagulation with a goal ACT of 200-220 seconds. A randomized controlled trial (RCT) has to prove that ACT guided heparinization would result in fewer TEC and lower mortality than a standardized bolus of heparin of 5 000 international units (IU), the current gold standard. ACT guided heparinization results in higher doses of heparin during operation and this should not result in significantly more bleeding complications of importance.

The ACTION-1 study will evaluate the effect of weight dosed heparinization during open abdominal aortic aneurysm surgery.The study will be an international multi-centre single blind randomized controlled trial. Patients will be randomized using a computerized program (CASTOR EDC) with a random block size of a maximum of 8. The randomization will be stratified by participating centre. Separate evaluation of results and if complications can be labelled as TEC, will be performed by an Independent Central Adjudication Committee. The 3 members of this Committee will be blinded with regard to if the patient was randomized for ACT guided heparinization or standard bolus of 5 000 IU without ACT measurements.

In the intervention group, heparin is given to reach an ACT of 200-220 seconds. Based on the ACT, an additional dose of heparin will be administered. Five minutes after every administration of heparin the ACT is measured. If the ACT is 200 seconds or longer, the next ACT measurement is performed every 30 minutes, until the end of the procedure or until new heparin administration is required (because of ACT \< 200 seconds). Depending on the ACT value near the end of surgery, protamine will be given to neutralize the effect of heparin.

In the comparative group, a single dose of 5 000 IU of heparin will be given 3-5 minutes before clamping of the aorta. No ACT measurements will be performed, except for one ACT measurement after re-establishing blood flow and removing all clamps. Depending on that ACT value near the end of surgery, the local protamine can be given to neutralize the effect of heparin.

Eligibility Criteria:
Inclusion Criteria:

* Able to speak and read in local language of trial hospital.
* Patients older than 18 years scheduled for elective, open repair of an iliac or abdominal aortic aneurysm distal of the Superior Mesenteric Artery (SMA) (DSAA segment C).
* Implantation of a tube or bifurcation prosthesis.
* Trans-abdominal or retroperitoneal surgical approach of aneurysm.
* Able and willing to provide written informed consent.

Exclusion Criteria:

* Not able to provide written informed consent.
* Previous open or endovascular intervention on the abdominal aorta (previous surgery on other parts of the aorta or iliac arteries is not an exclusion criterion).
* History of coagulation disorders, heparin induced thrombocytopenia (HIT), allergy for heparin or thrombocyte pathology.
* Impaired renal function with EGFR below 30 ml/min.
* Acute open AAA surgery.
* Hybrid interventions.
* Connective tissue disorders.
* Dual anti-platelet therapy, which cannot be discontinued.
* Life expectancy less than 2 years.
* Inflammatory, mycotic or infected aneurysms.
* Allergy for protamine or fish protein