[Thomas]

Thomas asked the Naked Scientists:

Hello, I recently had an operation on my leg and needed to carry a bottle connected to a drain in the wound. Because there was vacuum in the bottle, it gently removed excess fluids which would collect in the transparent bottle.

Now, the question is this: why did the (few millilitres of) blood not clot within a day? I was under the impression, when blood stops moving, it'll rapidly coagulate.

What do you think?

[iko]

Hi Thomas,

that blood did not contain fibrinogen-fibrin (clot forming protein) anymore.
In your case, blood probably clotted inside slowly and 'defibrinated blood' had been aspirated.
Anyway, it is not so uncommon to have clots clogging surgical drains.