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Can someone explain to me how INR, blood clotting and Warfarin works?

DribbleKing97 specializes in ACE.

I am not familiar and my school never taught me well about it. I get confused about blood clots how they are good and such cause it helps control bleeding? But then there are bad blood clots that can cause a PE? Are they the same? How does Warfarin apply to them?

KatieMI specializes in ICU, LTACH, Internal Medicine.

OK. Get me coffee (black, lots of sugar) and one for yourself, too, make yourself comfortable. There will be a long talk (and likely several posts).

To do its job - to deliver oxygen, antibodies, cells, nutrition and all that, and to flow out various chemical trash, blood must stay within the vessels. Therefore, if a vessel gets a hole, it must be quickly patched so that blood won't leak. Also, if there is something sticking into or out of the vessel wall, this thing must be covered in some way so that it doesn't dusrupt blood flow. 

The two things above are, from the body's point of view, very important. To get them done, the body has several overlapping systems. The name for ALL these systems are COAGULATION CASCADE. Why cascade? Because it works like an avalanche in the mountains. Once one part goes on, it activates the following step and each following step goes the same till, from the point of the view of the body, problem is solved and problem blood vessel is CLOTTED off. And, in case of blood vessels injury, in is "good" thing. Otherwise, blood would just flow out and you'll die from blood loss after scratching your finger. 

You just saw above that, basically, there can be two causes why a blood vessel might need to be clotted: either it is injured and blood leaks out, or there is some injury on the vessel wall, like piece of fat (yep, those "cholesterol plaques" in vessels are just areas of yellow hard fat which stick out into the vessel). Therefore, there can be two ways to activate clotting cascade. They are named "intrinsic" which starts from damaged vessel wall, and "extrinsic" which starts from another tissue damage but NOT damaged wall. 

KatieMI specializes in ICU, LTACH, Internal Medicine.

Continuing:

Without much ado about biochemistry (most interesting part for me, but it is another giant talk):

Both clotting pathways work similarly. Each is a row of chemical reactions when one component (they are all proteins which present in plasma in non-activated condition and they all got names which always start from F, for "factor", and continue as a number in Roman numericals, like FII, FX, FXII) activates the next one, which activates the next one, and so forth till FX, or "Stewart-Power factor", becomes active. FX is the central key component which ties extrinsic and intrinsic pathways into one and, with help of other "F"s, makes a plasma chemical named "protrombin", his other name "FII", into its active form "thrombin". Trombin activates another plasma chemical named "fibrinogen" into its active form "fibrin". Fibrin looks like thin and very sticky threads. These fibrin threads stick to exposed tissue, vessel wall and blood cells and form thrombus which cloths the vessel. 

Now, several "F" proteins are made in liver. Several of these liver-made proteins, namely FII(protrombin), FIX (which only works in intrinsic part) and that all- important FX guy need vitamin K to be made. Coumadin blocks action of vitamin K, therefore if patient takes coumadin, factors FII, FIX and FX are not made and blood won't make cloths. 

Just in case so that all this big system won't start running at a random place and time, organism has at least one chemical blocking each step and every chemical in coagulation cascade. These chemicals do not work like an avalanche and instead stop every cascade step as they go. At norm, coagulation and anticoagulation systems balance each other. If you cut your finger, local activation of coagulation cascade happens and only the wounded vessels are quickly clotted. If some platelets stick to the aterosclerotic plaque in your aorta (all humans have them after early childhood, so do not worry), local anticoagulation kicks in and cloth won't form. But, there are conditions which move balance toward coagulation. These are: 

- slow, static blood flow (for whatever reason- immobility, dehydration, low blood pressure)

- inflammation (caused by whatever)

- pregnancy

- trauma

- too much platelets

- various debris swimming in blood (think about metastatic cells, bacteria or microscopic pieces of broken bone)

- and quite a few others. Some people genetically have proteins in their plasma which activate coagulation (if you ever hear about "factor Leiden", that's one of the most common of them, but there are over a hundred of them known for now)

In these cases, coagulation becomes our enemy, because blood starts to get clotted rather randomly and in dangerous places. Since leg veins are wide and "soft", blood flow is normally slower there and cloths happen more frequently. They flow into vena cava, then in right heart, then into pulmonary artery and make PE, which is not good. If a cloth starts to form into arteries which supply heart muscle, there will be myocardial infarction. If it happens in brain artery, there will be an ischemic stroke. In these cases, we can administer drugs named "anticoagulants" (btw, please try not to name them "blood thinners" - they do not "thin" anything, they prevent clotting). Each of them works differently with different "F" factor(s) or with platelets which initiate extrinsic pathway, blocking their work in various ways. They can be "natural" (human blood contains chemicals very much like heparin but there is no way to boost their production in human body so far, so that medical heparin is made from internal organs of domestic cattle) or totally artificial like coumadin.

 

Edited by KatieMI

KatieMI specializes in ICU, LTACH, Internal Medicine.

One thing for you to remember iron-hard:

- there is no such thing as "good" and "bad" physiologic process. Blood pressure, coagulation, cholesterol, etc., CANNOT be "good" or "bad", just like rain or the Sun. They are here, and we are managing them when and if needed.

If you find yourself not knowing and understanding questions like this, it means your level of knowledge is critically deficient. I hope that what I wrote above helps in some way, but it won't substitute for your patho and pharma books and lectures, which you must dust off and re-read till you understand every single word. I purposefully did not go into INR question. Knowing and understanding all the above, it won't be too difficult for you to figure out what INR is and how it changes. 

To show your work: if patient experiences liver failure, where INR will go, and why? 

Counting for your other posts as well, I wonder  what kind of school "never taught you" about this basic info stuffed tightly into NCLEX. Accounting for how frequently a nurse should use knowledge about coagulation and how many patients are taking meds affecting coagulation, it looks like you might want your money back. 

Edited by KatieMI

You nailed that, KatieMI. Textbook perfect. Those are basic concepts I had to know six ways to Sunday before I sat for boards 42 years ago. I worry about the future of nursing. New nurses today are being done a great disservice when they're encouraged to move on to advanced degrees without teaching them the basics. No wonder they're 'confused.'

KatieMI specializes in ICU, LTACH, Internal Medicine.

6 minutes ago, sevensonnets said:

You nailed that, KatieMI. Textbook perfect. Those are basic concepts I had to know six ways to Sunday before I sat for boards 42 years ago. I worry about the future of nursing. New nurses today are being done a great disservice when they're encouraged to move on to advanced degrees without teaching them the basics. No wonder they're 'confused.'

Worse yet, I am usually the only one provider who takes time to sit and explain those basics. 

I do not know how schools nowadays let out nurses who literally do not know ABCDs of pathology and pharma and how these nurses successfully pass NCLEX in droves and get employed without having the slightest idea of what they are playing with. 

Oh, bother....

londonflo specializes in oncology.

On 7/28/2020 at 4:42 PM, KatieMI said:

I do not know how schools nowadays let out nurses who literally do not know ABCDs of pathology and pharma and how these nurses successfully pass NCLEX in droves and get employed without having the slightest idea of what they are playing with. 

 

If you would read the other posts of this OP, you would probably know this individual is not an RN and is not in the US. But it always is more fun to blame knowledge deficits on the education system that we know.  However, there are great gaps in her/his knowledge base but the Practical nursing educational program does not go in great depth on anatomy and physiology.

 

On 7/28/2020 at 4:42 PM, KatieMI said:

I am usually the only one provider who takes time to sit and explain those basics. 

Please find reassurance in that you are not the only provider that provides basic nursing education. You just may be the only one who needs to comment that the help was provided by you. Many others help our nursing students and licensed nurses. One of the defining characteristics of a profession is that those in the profession provide educational assistance to students/practitioners that follow and without needing public recognition

NCLEX is always looking for test item writers. Since you feel a large number of people/ drove are not identified as have an unsafe knowledge base with the NLCEX, please help! https://www.NCSBN.org/4801.htm

Rose_Queen specializes in OR, education.

52 minutes ago, londonflo said:

If you would read the other posts of this OP, you would probably know this individual is not an RN and is not in the US.

Several of member's other posts indicate he works as an RN in a retirement facility.

amoLucia specializes in LTC.

dianah - TY. I was thinking to ask you to split this post out. It is one of the most informative and upper level discussions here.

dianah specializes in Cath Lab/Radiology.

Just now, amoLucia said:

dianah - TY. I was thinking to ask you to split this post out. It is one of the most informative and upper level discussions here.

I agree, amoLucia, and wanted to preserve it!  We have such wise and knowledgeable members!

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