(1) There is no mention of blood concentrations or testing. The Andexxa dosing chart is based solely on which inhibitor drug&dose and *when* last taken. If unknown, it assumes it was taken recently.
So they may just be getting patient drug & dose info and then quickly guestmating a high or low dose of Andexxa.
(2) Also, the complaint about Andexxa & reconsitution delay might be more procedural than anything to do with the drug. It looks like a pharmacist could have some ready in 15 minutes. It's a manual, slow process - especially for multiple vials. I can't imagine pharmacists would be happy mixing this stuff up multiple times on a shift. But it didn't look unworkable by any means.