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Critical Heparin Values

Dave McGlasson posted this question on Medlab_L and gave me his permission to paraphrase and copy it here:

What do you use for critical heparin values when notifying providers about hemorrhage risk? It seems there is no standardization on this issue.  Chest 2008;133, Antithrombotic and  thrombolytic Therapy: American College of Chest Physicians Evidenced-Based Clinical Practice Guidelines (8th edition) does not seem to offer guidelines other than for elevated PTTs in standard unfractionated heparin monitoring.  Manufacturers of heparinoids also are strangely non-committal when asked these questions.

I have a couple of comments in follow-up to Dave’s question…

I checked with Dr. Marisa Marques and technical specialists Laura Taylor and Patti Tichenor at UAB special coagulation laboratory. They phone all PTT results over the unfractionated heparin therapeutic range.

Here is a statement regarding monitoring of low molecular weight heparin in Hirsh J, Bauer KA, Donati MB, et al. Parenteral anticoagulants. American College of Chest Physiciants Evidence-Based Clinical practice Guidelines (8th Edition). Chest 2008;133:141S-159S:

“Although some studies reported that high anti-Xa levels are associated with an increased bleeding risk, several other studies failed to show a relationship betweeen anti-Xa levels and bleeding. A randomized controlled trial comparing monitored and unmonitored dalteparin therapy for treatment of venous thromboembolism showed no benefit of monitoring. Therefore, routine anti-Xa monitoring is not indicated.”

Hirsh’s article recommends monitoring in pregnancy, weight-based dosing in obesity, and substitution of unfractionated for low molecular weight heparin in renal insufficiency, but does not further address critical values for the anti-Xa assay.

I’d like to learn what others do with anti-Xa heparin assay results above their therapeutic ranges. Please post your comments here or send me an e-mail. Geo

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