im so sorry about your cat pasdedeux. that is heartbreaking. we lost our dog about 6 weeks ago and it hurts so much even though she went by herself thank god. whether your can needed to be PTS right then or not s/he is at peace now and in no pain and s/he knows you loved him/her. you did what you believed was best.
im afraid i dont know about the pms but just wanted to say i feel for you.
take good care
biiv