Cristina,

You're right to try heating the tail. However, if you have access to a 'hot box', then transferring the animals into here for a short space of time (up to 30 minutes) to increase body temperature and thus tail blood flow should help you considerably. It sounds like you have it, in essence, though - I am not sure why you're only getting partial injections. Unless there's something obvious happening like a bubble forming and you've hit the interstitial environment instead. There may be issues with the agent you're delivering, also? Some larger compounds (Evans Blue springs to mind, in my experience) need to be dissolved and filtered well before use, else the agent often gets 'stuck' further up the vein.

Hope this is of at least some help to you!

Ross

The bottom line is that this is a difficult procedure.  I received training from our animal care services veterinarian and found that once you are aware of how to do the injection, it will then take a lot of practice.  Here are the tips that I found most helpful:  1) Trap the blood in the vein by squeezing the base of the tail with two fingers; this will cause the vein to swell and make it easier to see. 2) If you miss or go straight through, the vein distal to the puncture will collapse so you really only have one good shot, but if you begin distal and work your way up the tail you may get more than one injection per side.  3) A successful injection will cause an obvious immediate blanching of the vein proximal to the injection site.  4) Practice on an older/larger mouse or even a rat to perfect your technique.  5) Make the puncture with the needle bevel side down, then lift up slightly once you are in the vein while moving the syringe parallel and in line with the vein as you enter it.  6)  I thought an insulin syringe was the way to go, but I found that having a longer needle was necessary to get the proper angle during the injection.  Best of luck!

I use the hot water to heat the tail too. And it works for me. 

Stabilize the tail on a surface and put the tail in hot water (40C) for a min. Then do the injection. Try to hold your hands very still. Do lots of practice.  

Dear all, many thanks for all your tips. I have been trying tail vein injections these last few days and my rate of success has considerably increased. Now is only do lots of practice. 

I used to do IV injections all the time (see attachment). Get a stand to hold a big heat lamp bulb. Put it above the mouse cage and let them heat up a little. Get the blood moving.  And, as another commented, practice is the key.

Many thanks Dr. Mills! 

Thank-you all for the insides. I am going to start this injection technique soon, I hope I can make this work. 

Medilumine offers a tail-vein injection training workshop and service.

https://www.medilumine.com/tail-vein-injection-training-course/

https://www.medilumine.com/services/

I've trained hundreds of people to do tail vain injections and I always recommend to start on an anesthetized mouse, preferably a white or nude. This way you can get the feel of "hitting" the vessel. Practice this until your eyes bleed. Then move on to the pigmented mice because Black 6 mice are tough. After you master the Black 6 mouse anesthetized, then move on to an awake animal. This is significantly more difficult. I don't use any transillumination, or a tourniquet, or heated water but I do keep the mouse on a heated surgery board. Occasionally, I use a hair dryer on low heat to open the vessel. I've been catheterizing and injecting into mouse tails for over 25 years and there are still occasional days that I couldnt hit the vessel if my life depended on it. :) Enjoy.

Christine M Howison you would recommend me to use a dye to check the injection? or how can I be sure to perform the injection well?

thanks a lot!

kind regards.