Introduction: Unfractionated heparin (UFH) has been used for decades to prevent thrombotic events during vascular surgery. Although it is known that UFH has a complex and nonlinear pharmacokinetics, with great individual variability, anticoagulation monitorization in vascular surgery is not routine and a standard empirical dose is often used. Activated clotting time (ACT) has been shown to be a simple, reliable...