Disconnect between ACT results and anti Xa for ECMO patients
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The ECMO team in our hospital is noticing ACT results from our Hemochrons being low and anti Xa results coming back at above range. They are dosing the patients with more heparin at the time with the ACT result only to find out once the Xa result comes back from the lab that the patient shouldn't have been dosed with more heparin.
Are any of you experiencing this?
One of our doctors that specializes in Coag explains that Factor VIII can be high in critical patients in ECMO and this can shorten PTT and ACT but doesn't affect Xa. Any thoughts on this?
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Our Hemochrons are limited to the CVOR and Cath lab. Our ECMO protocol currently has ISTAT ACTs performed at regular intervals until the patient is stable for at least 4 runs. ECMO protocol also includes I think at least a daily PTT, regular interval anti-Xa UNF and also AT3 daily at a certain point.
I know that the Hemochron has some limitations. Being a pediatric hospital we occasionally face these limitations. I am not sure how it plays out in the adult world.
Our ACT+ cartridges (Hemochron Signature Elite) can monitor between 1U/mL and 6U/mL, but our Xa assay (IL TOP) is only linear up to 2U/mL. That means there is very little overlap in their ranges.
Different patients can have vastly different responses to heparin, which would be reflected in ACT results, since they are a measure of time-to-clot formation. The Xa assay is a direct measure of heparin but will not indicate how that heparin dose has affected the patient's clotting response. Since these assays are measuring different things, I wouldn't expect great correlation between the two.
It's nice to have different ways to measure heparin (Xa) and the body's clotting response to heparin (ACT) via these assays, but they are not measuring the same thing. ACT will be affected by many in-vivo variables. Staff that are interpreting these results should be made aware of the differences between these tests.
I was wondering, do any of you use the hemochron for citrate APTT/PTINR?
We used hemochrons in cath lab for 15 years then moved to Istat.
Debbie, I'd like to hear more about your transition from Hemochron to iSTAT..