Anti-Xa Assays and Plasmapheresis

From Joni Noges at Virginia Mason Medical Center: Hi George, our pharmacy is  wondering whether anti-Xa levels are affected by plasmapheresis, continuous renal replacement therapy (CRRT), or hemodialysis. For example, should we draw levels 30–60 minutes after the procedures? Thanks.

Hi, Joni, I forwarded your question to Lawrence “Lance” A. Williams, II, MD, who manages our UAB special coagulation laboratory service. Dr. Williams’ response:
We perform total plasma exchange (TPE) on heparinized patients all the time and do not have any special protocol for it. The exception is patients on extracorporeal membrane oxygenation (ECMO) with heparin in the circuit. Here, the only special thing we might do is increase the A/C ratio to avoid over-anticoagulating the patient. But even in this case, we are not monitoring the Xa closely. Some institutions do worry about it and say, stop the heparin 30 mins before the procedure and then restart 30 minutes after with a re-titration, but we do not have a special protocol and we do not do any special monitoring of the Xa before or after the procedure. Honestly, I don’t think TPE would have a big effect and would not worry about it closely monitoring Xa afterwards.

Added 6/16/16: This additional response from Huy Pham, MD, who manages the therapeutic plasmapheresis service: George, This is an interesting question. The AABB Apheresis Committee recently discussed this topic and they submitted an abstract to the AABB annual meeting this year.  Everyone is doing different things. Both here and at my previous institution, there was no special protocol and we do not do any special monitoring of the Xa before or after the procedure. However, we do tell them that we remove all coagulation factors. Thus, if they have problem getting heparin to the therapeutic level, then they should consider checking the antithrombin (ATIII) level. Summarizing the abstract submitted by the committee…

• Performing TPEs every other day rather than daily lessens the effects on clotting factors.
• Most perform TPE for patients while on warfarin, heparin, or DOACs.
• Several places switch patients on these medications to LMWH, which they withhold on the day of TPE.

There are additional recommendations about plasma use versus albumin and about preventing hypocalcemia that will be available to readers of Transfusion when the abstract is published.