Why do we have dofferent gauges of needle for injection? What difference does it make?



Why do we have dofferent gauges of needle for injection? What difference does it make?

In: Biology

A higher gauge allows for a greater flow rate (without cranking up the pressure, which is generally a bad idea) at the cost of greater discomfort to the patient. If you’re giving a 500 mL blood donation, you use a fairly high gauge because it would take hours otherwise. If you’re only getting a few mL of a drug, smaller gauge is fine.

Obligatory *not a doctor*. There may be other factors.

One muscular therapy, called “dry needling”, used to be done with syringes and was quite painful. Now, it is done with acupuncture needles (which are as fine as a hair) and it is painless (or nearly so).

Ooh, I know this one, as I regularly have to take an intramuscular injection.

Needles come in a huge variety of gauges, with the larger numbers being smaller in diameter and vice versa, so an 18 gauge drawing needle would be much bigger in diameter than a 24 gauge intramuscular needle which would be much bigger in diameter than a 30 gauge subdermal insulin needle.

The smallest ones are for water-based solutions like insulin. Their viscosity is very low so they push easily through the tiny needle. The bigger ones like 24-21 gauge gauge needles are for more viscous (thicker) solutions like testosterone, which is an oil-based solution or some antibiotics like Bicillin which is just really thick stuff. The ones in the teens like an 18 gauge drawing needle is for pulling the medicine out of its vial. The viscous oil is hard to push through the needle and even harder to pull with the vacuum pressure of pulling on a syringe, so the hole the medicine needs to travel through needs to be bigger to allow the person using it to get the medicine into the syringe without spending a minute or more getting the medicine out of the vial.

Other uses are as others have said before me, based around flow rate, like when a person is donating blood. It would take a LONG time to pull almost a half liter of blood (standard donation is 470 ml) through a small needle and if the donation were plasma, the blood cells would need to be returned to the person and would be way too viscous to try to push through a small needle.

A larger needle gets more liquids in at a time. A smaller needle does less damage and heals easier.

As people have stated lower gauges mean bigger needles which can be hooked up to wider IVs. Radius size increases the resistance of flow as it shrinks. So for pushing drugs having a smaller gauge allows for a quicker flow rate. Also in the case of dialysis, blood benefits from a flow rate that will lower its chance to clot. So high gauge tubing will not work at a certain point. At least without having to give a blood thinner simultaneously