Blood coagulation does not occur at time of drawing blood. It takes some time. It is called as clotting time. The clotting is the property of the blood if it is not running in the veins and arteries. The reason is that it is flowing in the vessels. If it stagnates (as in vials and test tubes), it will clot. With age there is a thickening of the internal lining of the arteries (called as atherosclerosis), due to which blood has slowing of the blood flow or stagnation. Thus it can clot in the arteries too and thus shut down the blood supply of the organ or any area of the body. That can cause serious consequence.
Please feel free for your follow up questions.
I recently had surgery with 70% block & a stent was put in. Apparently an angiogram of my heart indicated it was fibrillating ( which I had no idea & still don't feel it).
When I was recently in hospital to have a TEE done (going down to view heart area & shock heart), the nurse drew some blood & before she could get across room to do something with it, it had coagulated into a string that had to be pulled from the syringe. She then had to insert a needle into my hand & draw again & apparently it was o.k. & hey proceeded with the rest of procedure. Shocking my heart did not stop the fibrillating.
This is why I am asking these questions. Especially when I am told that there were other things that could happened when the blood was drawn that day.
A blood drawn from a thin needle can coagulate blood very fast and has a same phenomenon as stagnation. This is not a worrying episode and do occur many times and does not point to anything specific. When you had surgery, before it (or that matter any surgery or procedure), there are tests called as bleeding time and clotting time (BT and CT), which are done. If there was any clotting disorder, that would have come abnormal in these tests. So please do not worry
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