Oh Cynthia, I am so sorry.
I know that Mercedes crossed that Rainbow Bridge and is frolicking, pain-free and carefree, in a meadow with all her favorite treats and toys nearby. God bless her, and you and your family who loved her and gave her a wonderful life here on Earth.
Big, warm (((hugs))) to you, and to all of you who posted about the worries you have for your own beloved pets. My heart's with you all. Our Bichon, Eddie, is 13 and I know we're lucky that he's in pretty good shape at that relatively advanced doggy age.