For many of the last 25 years of ECMO support in the United States, activated clotting time (ACT) point of care testing has been the primary standard for assisting the ECMO Specialist adjust heparin. The delicate balance of keeping the system from clotting and keeping the patient from bleeding rested on a very primitive test done at the patient bedside. I have heard it said that using the ACT to adjust heparin is a little like using a sledge hammer to play a concert piano. Yet the ACT remains one of the most frequently used tests for ECMO patients.
With that said, over the last few years there has been a definite move towards adding additional tests to the equation and in some places the ACT has been completely eliminated from the equation. There have been numerous reports, papers, abstracts, and research articles discussing how tests such as aPTT, antix-a, ATII, PT/PTT, TEG, and others are used in conjunction with or instead of ACT to help balance appropriate anticoagulation for the ECMO patient.
So, here is my chance to share some of the results of my ruminations.
I would suggest consideration of utilizing the COMBINATION of
- ACT (Activated Clotting Time)
- Anti Xa (Heparin Assay)
- Fibrinogen Level
- Platelet Count
Some might notice the absence of APTT (Activated Partial Thromboplastin Time). I am not completely opposed to it. Some use it exclusively. It’s not in my top 5…yet. There are conflicting reports regarding how APTT correlates with the old and crude ACT standard for ECMO patients. But there are conflicting reports about anticoagulation strategies as a whole. I wanted to at least acknowledge that APTT should be part of a discussion and discovery process as you explore what works best for your center.
So why the 5 tests that I listed? Check back for more explanation of Randy’s Ruminations related to anticoagulation management for ECMO patients.