From SSB:

Alright....ive been reading the "injection into vein" thread and i noticed that alot of people are pulling the plunger back to a certain extend. Having been a hematoloy lab tech, and a phlebotomist, i am going to explain the "art" behind the perfect aspiration..

First, you must understand that the blood circulatory system is under pressure at all times within the vessels...so minimal vaccum should cause a draw effect.

Having said that, you must also realize that if you create too big of a vaccum with a syringe inside the vein, you will collapse the vein as you will suck the vein wall right against the bevel of the syringe and that will create a plunger effect.

NOW...since you know the above, now we can start explaining how to aspirate...

What one should do is either just use their finger and flick the plunger or push gently upwards (move the plunger no more than a millimeter) this vaccum draw should create a vaccum effect that you will end up with a fair bit of blood in the syringe already....If you pull to hard and too fast, you will just end up with no blood in the syringe because you created the plunger effect mentioned above...and youll just inject into the blood vessel.


Hope this clarifys how to aspirate...