Practice Tip: Useful ET Tips from Patrick Comyn, DVM

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Published on: June 10, 2015

I have several things that I will try to explain that I have found useful in embryo transfer.

1. I use the EZ WAY filters. I had been draining the filter and then washing down with 3 × 20 mL flush solution with the outlet plugged. The problem was that the fluid would get sort of deep in the bottom of the dish, making searching hard, especially if the recovered fluid was more mucousy or cloudy than usual. So now I keep the plug out after draining and wash with 4 × 20 mL flush solution. Then I place the plug in the bottom of the drain side of the dish. Doing this allows ~25–30 mL of fluid to accumulate in the bottom of the dish. This method makes searching the plate much easier and faster; also, embryos settle to the bottom faster.

2. When using short straws, because of heat sealing, always double check the embryo sheath before placing the embryo. Do this by pulling down the sheath over the rod and straw (seated in the rod) until the straw should be seated in the sheath tip. Then pull back the sheath while in the light. If the straw does not move back and forth with the sheath, then it is not seated. So, then cut the bottom of the sheath a centimeter or so until the straw does seat correctly.

3. I think that blown straws are largely caused by a miniscule amount of liquid nitrogen getting pulled into the area under the plastic plug. Liquid nitrogen has a 600-fold expansion coefficient from liquid to gas at room temperature. So, if while seeding the straw one seeds the top air column without properly seeding the fluid column next to the plug, it will cause the column to contract because of the contraction of the air column due to temperature drop. The contraction pulls air in through the plastic plug–straw interface IF the plug–straw interface is not well sealed (irregular straw or plug surface). Nitrogen then creeps in while the straw is bathed in liquid nitrogen. The solution to this is to always thoroughly seed the top fluid column before seeding any air columns. Per label, one should seed the air columns if using Syngro Freeze solution for DT.

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