Senseless death

In regards to Jazmine76, our Shih-Tzu just had to be put to sleep last night. She to was a healthy 3 year old dog full of life and energy. About 11 days ago she became sick and took her to the vet. The vet said she had a fever of 104 and sent us home with an antibiotic. The next day she seemed worse so I took her back to the vet and she gave her a cortizone shot . Next 3 days she seemed much better, but that night symtoms started back up with the same shaking and just wanting to lay down. Brought her back to vet and he said she probably has an infection in her uterus and wanted to do a ultrasound which came back fine as did all of her blood work. The vet gave new antibiotic and sent us home. The next day our dog was even worse cold not urinate and was walking funny, with her back arched up. We brought back to vet and they thought she had a slipped disk and kept her over night. Again, the next day she was worse and could not move her back legs. Our vet took x-rays of her back and could not see anything abnormal. They kept her again overnight and gave her an iv with strong antibiotics, but her health continued to decline and last night her tempature reached 107 and the vet said she could not recover. We made the gut wrenching decision to put her to sleep. Our family is in deep pain over this senseless death from a seamingly very healthy dog . The only connection I can see that was different was putting the Revolution flea tic and heartworm medication on her the day before all these symptoms started. After reading the pamphlet inclosed with the warnings it did say it could cause fever and in rare cases even death. So, my conclusion is beware of this medication that is supposed to protect your pets because it might be killing them. If there is anyone out there with a similar story please respond back to me.