Clarification on drawing dose into syringe

[FullAuto]

For the past 18 months, I have been using 1ml "Luer-Lock" syringes (#04-3001) and need some clarification on drawing the proper dose into the syringe. I think I may be injecting 0.1ml too much each week, but I am not entirely sure?

My protocol is to inject 0.7ml/140mg of Test per week...…I use my 18g draw needle to draw the Test from the vile to the 0.7ml line, but as I drawback before installing the 25g needle for my injection, the actual amount in the syringe will read 0.8ml from the base Zero line. This type of syringe looks to hold 0.1ml of Test between the installed needle headspace to the zero line.

I have used different type syringes in the past were the face of the rubber stopper is flat and after injected IM, I would still have a residual amount of Test left in the tip of the needle....However the "Luer-Lock" syringes use a rubber stopper that incorporates a nipple that injects all the Test drawn into the syringe. So is the proper volume from the zero line to fill line, or from completely empty to fill line?

Thanks in advance and I truly hope I didn't confuse the heck out of everyone!

Cheers!

Doug (FullAuto)

 

[Vince Carter]

I dont see a problem other than you can use smaller/shorter needles, there's no real need to use anything larger or longer than a 29g 1/2". There's low waste in that type of needle, or dead space.

 

[Cataceous]

I'm not sure how you can get that result. What you first describe sounds like a high-dead space tip, which does waste about 0.1 mL, as illustrated on the right:

In this case you would see about 0.8 mL of fluid when you pull back the plunger a little to exchange tips. But in this scenario you would be left with the extra 0.1 mL in the syringe after the injection. However, if there's a tapered plunger then things should be more like the left-hand illustration, and you should see 0.7 mL of fluid in the syringe, e.g. going from the 0.1 mL mark to the 0.8 mL mark after you pull back.

 

[FullAuto]

After careful examination...I have answered my own question, additionally your response with diagrams have helped too...Thank you!

So the Luer-Lock syringes I use have an extended nipple incorporated into the rubber plunger along with high dead space, this nipple pushes all of the contained fluid out of the syringe when completely depressed versus leaving any fluid remaining......I've since realized that when I draw 0.7ml it is actually 0.7ml and not to be confused with when I draw the syringe back slightly to change from my draw needle to my injection needle since this nipple still takes up the same volumetric space regardless of volume.

Thanks for the response...we can now close discussion on this topic!

I'm not sure how you can get that result. What you first describe sounds like a high-dead space tip, which does waste about 0.1 mL, as illustrated on the right:

In this case you would see about 0.8 mL of fluid when you pull back the plunger a little to exchange tips. But in this scenario you would be left with the extra 0.1 mL in the syringe after the injection. However, if there's a tapered plunger then things should be more like the left-hand illustration, and you should see 0.7 mL of fluid in the syringe, e.g. going from the 0.1 mL mark to the 0.8 mL mark after you pull back.

 

[FullAuto]

Thanks for the quick response Vince...I have since solved my question after giving it some thought! However, I may have just revealed to everyone that that I might just be a dumbass! (face in palm) Ha!...All good

I dont see a problem other than you can use smaller/shorter needles, there's no real need to use anything larger or longer than a 29g 1/2". There's low waste in that type of needle, or dead space.