Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
Now as long as Roxy has pink gums and her breathing rate is ~20-30 breaths per minute; we'd assume that her labored breathing was just related to the distress of feeling unwell with GI upset. Of course, if she had pale/white gums and was in respiratory distress, we'd be in an urgent situation and want her seen immediately.
With that aside, I must note that her appetite loss is likely related to the same nausea that caused her to vomit. Often we see nauseous dogs refuse food. Common causes for all these signs include bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, secondary to organ or metabolic disease, cancer, general dietary indiscretions, and ingestion of harmful items (hopefully less likely at Roxy's age).
Now with all that in mind and since she can keep water down, we can try some home supportive care to try to settle her stomach. To start, if she hasn’t just vomited (since otherwise we’d need to rest her stomach for a few hours first), then you can consider treating her with an antacid. Common OTC pet safe options would be:
* Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid)
*Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac)
* Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet)
Whichever you choose, we’d give this 20 minutes before food to allow absorption. Of course, do double check with your vet if she has a known health issues or is on any medications you haven't mentioned. And I would note that if you give this and she cannot keep it down due to nausea that is usually a red flag that we need to bypass her mouth with injectable anti-vomiting medication from her vet.
Once that has had time to absorb and she is steadier on her stomach, we can start her on small meals of an easily digestible diet like cooked white rice with boiled chicken, boiled white fish, cottage cheese, scrambled eggs, or meat baby food (as long as its garlic/onion free). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning her slowly back to her normal diet.
Since dehydration is a risk for Roxy (especially if her drinking is poor), we need to keep an eye on her hydration. To check that she isn't dehydrated, there are a few things you can test. Further to checking for gum moisture, do make sure she doesn’t have sunken eyes and that she doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you are seeing any signs of dehydration already, then that would be our cue to have her seen before this becomes an additional issue for her (especially as it is often dehydration that makes them feel unwell).
Overall, there are a wide range of agents could trigger this GI upset we are seeing. Therefore, we’d want to start supportive care to settle her stomach. If she cannot keep that or water down at any point, appears dehydrated already, or doesn’t respond to the above within 12-24 hours; then we'd want to get her vet involved. They can assess her hydration, rule out fever, make sure there is nothing in her stomach that shouldn't be there or any sinister viruses present. As well, with her being elderly, you may also want her vet to test a blood sample to ensure her organs are working as they should. Depending on their findings, her vet can treat her with injectable anti-vomiting medication +/- antibiotics to settle her stomach, and get her back feeling like herself.
All the best,
If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you! : )