[1][2] The ACT test can be used to monitor anticoagulation effects, such as from high-dose heparin before, during, and shortly after procedures that require intense anticoagulant administration, such as cardiac bypass, interventional cardiology, thrombolysis, extra-corporeal membrane oxygenation (ECMO), and continuous dialysis.
The clotting time is based on a relative scale and requires a baseline value for comparison due to inconsistencies between the source and formulation of the activator being used.
Clotting time measurements can be affected by drugs such as warfarin, aprotinin, and GpIIb/IIIa inhibitors, and physiologic disturbances such as hypothermia, hypervolemia, and hypovolemia.
It fell out of favor to monitor heparin dosing during cardiac surgery because of the dedicated time required.
The coagulation end point can be determined by the optical (e.g., increased opacity detected by optical sensor) or mechanical properties (e.g., increased rigidity detected by the displacement of material in the vial) of the clotting blood.