IV injection and Blood sampling- rat tail vein - (Jun/16/2009 )
Hi,
I would like to perform an iv injection in the rat tail vein. Two hours later, I would like to sample 500ul blood from the tail vein. I need to collect a serum sample as opposed to plasma and therefore cannot use heparin. What is the best way to do this? Originally I was just planning on doing the iv injection with a normal 21G needle. Then two hours later, inserting the needle again and taking my blood sample. It has been suggested to me however that I insert a butterfly needle into the tail vein for a few hours and use that to administer the injection and later to sample the blood. I can't use heparin so I'm worried about clotting using the butterfly needle. The rats I will be using are pregnant so I am really trying to minimise stress. Can anyone advise me which way sounds better- 2 needle sticks or the butterfly needle (with risk of clotting)? Thanks 
TRA on Jun 16 2009, 09:41 PM said:
I would like to perform an iv injection in the rat tail vein. Two hours later, I would like to sample 500ul blood from the tail vein. I need to collect a serum sample as opposed to plasma and therefore cannot use heparin. What is the best way to do this? Originally I was just planning on doing the iv injection with a normal 21G needle. Then two hours later, inserting the needle again and taking my blood sample. It has been suggested to me however that I insert a butterfly needle into the tail vein for a few hours and use that to administer the injection and later to sample the blood. I can't use heparin so I'm worried about clotting using the butterfly needle. The rats I will be using are pregnant so I am really trying to minimise stress. Can anyone advise me which way sounds better- 2 needle sticks or the butterfly needle (with risk of clotting)? Thanks
I am assuming that your question was about the method of blood collection, and not about how to get serum.
IMHO, two needle sticks would be better in this case, everything considered. You could perhaps use the same tail vein, but use a distal point to infect and a proximal point to withdraw blood.
kausikdatta on Jun 20 2009, 08:19 PM said:
TRA on Jun 16 2009, 09:41 PM said:
I would like to perform an iv injection in the rat tail vein. Two hours later, I would like to sample 500ul blood from the tail vein. I need to collect a serum sample as opposed to plasma and therefore cannot use heparin. What is the best way to do this? Originally I was just planning on doing the iv injection with a normal 21G needle. Then two hours later, inserting the needle again and taking my blood sample. It has been suggested to me however that I insert a butterfly needle into the tail vein for a few hours and use that to administer the injection and later to sample the blood. I can't use heparin so I'm worried about clotting using the butterfly needle. The rats I will be using are pregnant so I am really trying to minimise stress. Can anyone advise me which way sounds better- 2 needle sticks or the butterfly needle (with risk of clotting)? Thanks
I am assuming that your question was about the method of blood collection, and not about how to get serum.
IMHO, two needle sticks would be better in this case, everything considered. You could perhaps use the same tail vein, but use a distal point to infect and a proximal point to withdraw blood.
I agree that you should definitely do two sticks as opposed to one. When we did a recent rat study, I cut down a 25 g butterfly catheter to about 1 cm so that it dropped drop by drop into my microtainer. This way the blood didn't really have much time to clot in the tube of the catheter. It also bleeds pretty quickly this way.
Thanks a lot for the advice. Might try the modifed catheter. 
TRA on Jun 25 2009, 12:28 AM said:
No problem. The trick is to cut it down short enough so it doesn't clot in the tube. I wish that the manufacturers for the butterfly catheters would make an animal research based one in that the tube would be shorter, but I think the shortest is 3 inches. It's a waste of tubing, but it works.
I had a terrible time today trying to withdraw blood from the rat tail vein with regular 23 and 25 gauge needles attached to a syringe 
. I only managed to get around 50 ul blood and I need 500ul. I think the blood was clotting in the needle. Can anyone advise me on what type of needle to use- maybe a butterfly one like the one shown in the photos on this webpage: http://www.nc3rs.org.uk/bloodsamplingmicro...page.asp?id=351
In that link, that's the modified butterfly catheter that I was describing. If you cut the tubing down on the 25 g butterfly catheter to about a centimeter, it allows the blood to drip slowly, but if you are patient enough, you will get enough blood. Make sure that the tail is warm by either a heat lamp (which is what I use) or warm water, and you can "milk" the tail to get more blood, but you might get a more hemolyzed sample the more you do this. To me, this catheter works much better than a needle attached to a syringe which tends to clot the blood in the hub of the needle. Hope this works for you.
Thanks Stace. Tried modified 21G needle and had a lot more luck!
Glad to hear it. I'm happy that I was able to help.