Anastomotic concept – 120 degrees, 9 stitches
We will be using nine stitches of 10.0 suture.
The anastomotic concept is the same as for the previously described rat femoral artery model.
Precautions to avoid tear
In this model it is crucial to select a suture with a slim needle, as a thick needle is likely to tear the tissue when penetrating it.
It is also more important than in previous models (a) not to touch the tip of your needle, so it remains sharp, and (b) to turn, rather than push the needle through the vessel wall.
The thread should not have too much memory, as this would cause it to remain kinked after being bent around an instrument’s edge.
To reduce resistance while pulling the thread through the vessel wall, be sure to guide it with your needle holder.
The thread should be kept moist and clean so it slides through the tissues smoothly.
When performing a venous anastomosis, it may be helpful to choose a larger distance between each stitch and the cut edge than in an arterial anastomosis.
This helps increase resistance to tear when pulling on the suture while tying knots.
Anastomosis – 120 degrees, 9 stitches
The anastomosis is best performed in partial or complete submersion to keep the vessel from collapsing.
The first stitch is placed, its suture guided through the fragile vessel wall and its knot tied. The second stitch is placed 120 degrees from the first in the same fashion. Stitches three and four are placed as a pair between the first two and complete the front wall. Stitch five is placed in the middle of the back wall.
Stitches six and seven complete the second 120-degree segment. Stitches eight and nine complete the anastomosis.
When the anastomosis has been completed, release the clamps in the order proximal, then distal, so that the pressure in the vein is increased gradually.
Finally, perform a gentle Acland test.
If your anastomosis is patent, cover it up with moist gauze and leave it alone for 20 minutes. Then test its patency once more.
You can use the same vessel to repeat the exercise for as often as you can approximate the vessel ends, or you can use the same animal for another exercise on abdominal vessels, contralateral femoral vessels or neck vessels.
Now that you have performed a venous anastomosis in a relatively small vessel, we recommend you to try the exercise on the relatively larger inferior vena cava, where collapsing of the vessel and flotation may be somewhat harder to manage.
A similar scenario will be presented in the Rat Vein Graft Model.
Advanced/optional: anastomosis – 120 degrees, 6 stitches
Just like the rat femoral artery, the rat femoral vein can be anastomosed with six stitches instead of the previously demonstrated nine, as long as all stitches are perfectly spaced.
Minor bleeding can generally be stopped with gentle compression, while fewer stitches pose a lesser risk of injuring the vessel wall. This is especially important for venous anastomoses since the venous vessel wall is generally more fragile than that of the artery.