international normalized ratio

And that's in contrast to unfractionated heparin and low molecular weight heparin such as anoxaparin, which are more like indirect thrombin inhibitors because heparin and anoxaparin actually bind and activate antithrombin.

Then remember that the traditional coagulation tests primarily include PT, INR, and PTT.

PT and INR are a measure of the extrinsic pathway, and PTT evaluates the intrinsic pathway.

PT and INR are elevated first with synthetic liver dysfunction due to factor VII having the shortest half-life.

Okay, let's move on to the technology of Teg and Rotem.

TEG is thromboelastography and Rotem is rotational thromboelastometry.

So here's the lab translation.

So the PT and the INR, they are going to measure the extrinsic and the common pathways.

Somebody drew this out for me one time when they showed the PT and PTT, and then they drew a little stick figure man.

If you draw it next to the PT, it's the T doesn't make a full house around it, so he's kind of outside or extrinsic.

It just stops new active factors from being made.

So the effect depends on how quickly each existing factor is going to wear off.

Factor seven has the shortest half-life, around six hours, so that's gonna fall first, and that's why the PT and the INR are going to rise early.

It's also why warfarin can be briefly prothrombotic at the start of the therapy.