Venipuncture with a syringe and needle?

Question

I would like to ask,

what size needles and how much of the needle do you insert into the vein before you start aspirating for blood?

Answer 1

the standard size needle for blood draw in the laboratory is 21 gauge.  with practice you learn to stop when you see a flash at the hub of the needle.  eventually you can tell by feel when you are in a vein. as a rule  25 gauge needles are too small to draw blood.. it will cause the blood to be hemolyzed and the specimen will have to be recollected.  occasionally the lab does use 23 gauge needles for really small veins.  butterflies are the same size gauge as regular needles (21g and 23g) the only difference is that the butterflies are shorter..3/4 of an inch rather than 1 inch or 1 1/2.  since they look smaller psychologically the patient thinks you are using a smaller needle.

on very rare occasions I have used a 25 gauge on a neonate with extemely small veins but it takes extreme care get an acceptable specimen.

Answer 2

21g needle, only the tip goes into skin. The needle must be bevel up. that is the opening in the needle itself.

Answer 3

Like the previous posters said--I usually use a 21 or 23 gauge needle but will use a 25 on small children.

When you use a butterfly needle, as soon as you are in the vein you will see a "flash" back into the chamber of the needle--blood pulsing in.  That's how you know you're in and you can stop.  You usually don't have to put more than maybe a third of the needle in.  (You specified venipuncture--when you go for an arterial stick, they are often deeper, so the needle goes in further.)  You just want to be sure the needle is in far enough to stay steady and not dislodge in the middle of your draw.

If you're drawing blood with vacuum tubes, you don't have to aspirate at all--the tubes will do it for you.   Otherwise you can use the syringe to draw the blood up at that point.

Answer 4

Usually the needle size is 20, 21, or 22 gauge.

Ironically, the larger the gauge number, the smaller the needle. So for children or people with small, delicate veins, you might use a 25g.

When inserting the needle, you want it to enter the lumen (center) of the vein. You only use part of the needle and it varies with person how far the needle needs to be inserted (usually only a small part). You can tell with practice if you are not far enough in the vein or too far in, which can be dangerous to the patient.

hope this helped! good luck

Answer 5

I am a phlebotomist and the previous poster is very correct.  25g needles with destroy your cells when you use them. Most syringe draws in our lab are done with a butterfly only so you will see the flash when you are in.  If you go in to far you can pull back a little and keep your bevel down to help with blood flow.  Syringe draws can be very tricky and you have to work quickly but yet pull back gently to save the cell from being destroyed.