To expand on my earlier post: I had to have a cat euthanized due to feline leukemia and stayed with him for the procedure. The bottle (which at the time I just observed as a big bottle of blue liquid which looked like the blue shit barbers put combs in, but I now recognize as unsterile pentobarbital dyed blue to identify it as such) had lots of syringes stuck in it of various sizes, with needles of various gauges. This is obviously for the different sizes of animals being put down. It first struck me as kind of haphazard until I realized there's no point in sterility when it's a lethal injection. After he had injected my cat, the needle went straight back in the bottle, and I remember seeing blood mix into the fluid in a purple tinge.
So, if you're back in the lethal injection room and you happen to have a moment alone, you might do well to search the cabinet for a new bottle, but I wouldn't bother with the one currently being used.
One final note: the injection worked incredibly fast. Little Yoda caught the little kitty bus quickly and peacefully. We should all be so lucky.