anti xa lab draw question



I'm new to the whole anti xa lab protocal and have a question. I had a nurse at work tell me one thing and another nurse tell me something else..

When do we actually adjust the dose? Do we do it from the time the lab was drawn or from the time the lab is back?

Example: The draw time is 0800. The lab is drawn. In our facility it needs to be shipped out, so we don't get them back for a couple of hours. At 1000 (for ease of figuring) the lab is back and the heparin needs to be adjusted. Six hours from now the lab needs to be drawn, right? So 1600.

I say it has to be drawn from the return time, which would be 1000. Another nurse I worked with said it was from the draw time. I'm so confused.


374 Posts

Specializes in Family NP, OB Nursing. Has 15 years experience.

The lab should be drawn 6 hours after any dose adjustment. In your case, if you changed the dose when you got the results back at 1000 then you are correct. You would draw the lab again at 1600.

tokmom, BSN, RN

4,568 Posts

Specializes in Certified Med/Surg tele, and other stuff. Has 30 years experience.

I totally agree with the above poster. The other nurse doesn't know what she is talking about! You would be drawing only 4 hrs later from dose adjustment if you went by the 0800 draw.

Home Health Columnist / Guide


11 Articles; 17,842 Posts

Specializes in Vents, Telemetry, Home Care, Home infusion. Has 46 years experience.

anti xa --new lab test i wasn't aware of...

heparin anti-xa: the test

when is it ordered?

the anti-xa test is not routinely ordered but may be performed whenever a doctor wants to evaluate ufh or lmwh concentrations in the blood. it may be ordered periodically to monitor ufh therapy, especially when a doctor feels that a patient is not responding as expected to ufh or when the ptt is not useful.

when it is used as a lmwh monitoring tool, anti-xa is primarily ordered as a “peak” test. it is collected about 4 hours after a lmwh dose is given, when the concentration of lmwh in the blood is expected to be at its highest level. random and “trough” anti-xa tests may also be ordered when a doctor suspects that a patient may not be clearing the lmwh at a normal rate. trough tests are collected just prior to the next dose, when heparin concentrations are expected to be at their lowest. ...

psu_213, BSN, RN

3,878 Posts

Specializes in Emergency, Telemetry, Transplant. Has 14 years experience.

I once had a nurse try and tell me that the next draw was 6hr after the previous. The protocol specifically said the next ptt was to be drawn 6 hour after the adjustment to the gtt (this was at change of shift, and that nurse even went into the computer to change the time of the next lab draw to meet "her" schedule). The whole point of the protocol and how it is set up is that the next aPTT is based on the pt getting the new dose based on an adjustment to the gtt. Therefore, they need to get 6 hours of the 'new' dose after an adjustment before the next ptt is drawn. Hope that all makes sense. :idea: