to you and your cat.
Personaly I would go for the I.V catheter. Sadly I have been present for many euthanasia's from my time working in a clinic and I think a catheter is best. From my experiences anyway.
"An animal's eyes have the power to speak a great language." ~ Martin Buber
"All of the animals except for man know that the principle business of life is to enjoy it." ~ Samuel Butler
"The purity of a person's heart can be quickly measured by how they regard animals" ~ Anonymous