How do you approach heparin management in patients who have suprathetherapeutic Xa levels on minimal heparin?

Assuming heparin is administered using standard weight-based dosing, that the infusion rate is being accurately monitored, and that the assay was done properly, very high anti-Xa levels that persist despite lowering the heparin dose would be most unusual. In that setting, I would suspect that either, 1) the test sample was contaminated with heparin from a line or drawn from a vein immediately upstream of the heparin infusion, 2) there is a residual amount of one of the oral Xa inhibitors (which ...